Bisphenol A Biomarkers and Biomonitoring

C H A P T E R

25 Bisphenol A Biomarkers and Biomonitoring P. Cohn1, A.M. Fan2 1

New Jersey Department of Health (retired), Trenton, NJ, United States; 2California Environmental Protection Agency (retired), Oakland/Sacramento, CA, United States

INTRODUCTION Bisphenol A (BPA), 2,2-bis (4-hydroxy-phenyl) propane, has been receiving increasing attention because of evidence on its reproductive toxicity and endocrine disruption effects in laboratory studies, the growing literature correlating environmental BPA exposure to adverse effects in humans, its high production volume, its widespread human exposure, and the potential diverse types of human health effects in addition to reproductive toxicity and endocrine disruption (Fan et al., 2017). The widespread use of BPA in the production of polycarbonate plastics and epoxy resins used in many consumer products, including packaged foods, has led to its extensive distribution and contamination in the environment and nearly universal exposure to humans in developed countries. Due to the instability of the polymers, BPA leaches out because of heating or the acidity/alkalinity of the food. Importantly, maternal exposure to BPA results in embryos and newborns receiving BPA via placental transfer and breast milk. The evidence available from laboratory animal studies is that unconjugated BPA (uBPA) has estrogenic activities of concern at levels found in human environmental exposure (Richter et al., 2007; Vandenberg et al., 2013), whereas BPA conjugated with glucuronide or sulfate is inactive. Most of the conjugation activity occurs in the liver, and blood flow from the intestinal tract goes first to the liver. Dermal absorption and direct absorption in the mouth do not pass first through the liver. The concern about individual variation in the level of uBPA informs one of the key biomarker issues in the next section. Although the European Food Safety Authority (EFSA) based its temporary tolerable daily intake of 4 mg/kg body wt/day on increased kidney weight in

Biomarkers in Toxicology, Second Edition https://doi.org/10.1016/B978-0-12-814655-2.00025-6

male mice (EFSA, 2015), mammary gland, liver, various endocrine functions, and metabolism have also been shown to be affected (Vandenberg et al., 2013). As part of an update on BPA toxicology, the US National Toxicology Program (NTP) recently announced the peer review of the Draft NTP Research Report on the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA) Core Study (NTP, 2018). The draft report is on perinatal and chronic extended-dose-range study of BPA in rats. This study is part of the CLARITY-BPA, a research program between the NIEHS, NTP, and the National Center for Toxicological Research (NCTR) of the US Food and Drug Administration (FDA). CLARITY-BPA was developed to bridge guideline-compliant research conducted at the FDA with hypothesis-based research investigations conducted by academia on the toxicity of BPA. The final conclusions are expected in 2019, which will be based on the integration of the Core Study and Grantee Study findings. In considering the toxicity and adverse health effects of BPA exposure, a particular concern is the possibility of low-dose effect and that nonmonotonicity of BPA would occur at doses lower than those used in regulatory toxicity studies, as demonstrated in nonmonotonic doseeresponse curves (NMDRC). The NMDRC is characterized by a change in the sign of the slope, and the function can take on the shape of a U, the shape of an inverted U, or another shape that has more than one inflection point. There are uncertainties requiring additional research on effects on mammary gland, and reproductive, neurobehavioral, immune, and metabolic systems at low levels. The causes of the U-shaped curve can include the inhibition/activation of different subsets of cellular receptors, one or more enzymes, and nuclear transcription factors and proteasomes as the dosage is changed from low to high.

429

Copyright © 2019 Elsevier Inc. All rights reserved.

430

25. BPA BIOMARKERS

The environmental and human health concerns have led to bans or restrictions in use in different countries. The preponderance of international regulatory bodies evaluated and determined that there is no health risk in the general population from average BPA exposure, and that existing exposures are below the health guidance value of 4 mg/kg body wt/day established by the EFSA (2015). However, other opinions have expressed concerns about its potential human health hazard and uncertainties relating to the toxicity and exposure of BPA. These aspects in toxicology and risk assessment of BPA have been described in an earlier discussion (Fan et al., 2017), which should be read as a supplementary compendium to this chapter to serve as a background to the present discussion on biomarkers with a focus on urinary BPA biomarkers. Readers are also referred to the discussion in an earlier chapter on biomarkers in toxicology, risk assessment, and chemical regulations for a discussion of the different types of biomarkers (i.e., biomarkers of exposure, biomarkers of effect, biomarkers of susceptibility) and some of the chemical samples presented (Fan, 2014). The present discussion will focus on review of recent reports (last 10 years or relevant as appropriate) on the following: (1) studies that investigate the prevalence of BPA exposure in humans, using urinary BPA as biomarker, including several major population studies (e.g., biomonitoring studies such as the United States [US] National Health and Nutrition Examination Surveys [NHANES], Canadian Health Measures Survey [CHMS], Generation R study in the Netherlands, Norwegian Mother and Child Cohort Study [MoBa] for the general and certain specific populations); and (2) selected studies on findings on urinary BPA in pregnant women, children, and motherechild pairs, along with observations of neurobehavioral effects in some of the studies. Children are more susceptible to the effects of environmental toxicants under certain conditions especially in the early months of life (Marty, 2015). They have immature metabolic pathways and differences in ability to metabolize, detoxify, and eliminate toxins compared to adults. These led to a particular interest in BPA, which has been shown to have endocrine activities, reproductive toxicity, and adverse effects on the young.

BISPHENOL A BIOMARKER ISSUES IN BIOMONITORING Environmental chemicals that have entered the human body may leave markers reflecting the exposure. The marker may be the chemical itself or a derivative of the chemical, measured in the biological matrix, but

it may also be some change in the body resulting from the agent or its breakdown product(s). Biomonitoring programs provide an important source of human exposure data to environmental chemicals, including BPA. BPA has been measured as total BPA, uBPA, BPA glucuronide, and BPA sulfate in human urines. In humans and other primates, orally administered BPA is rapidly absorbed and transformed to BPA glucuronide during first pass metabolism in the gut wall and the liver and a small amount of BPA is converted to a sulfate conjugate (WHO, 2009). More than 80% of orally administered BPA is cleared from the body in 5 h. The conjugated forms of BPA are devoid of estrogenic activity. BPA metabolism is influenced by age, gender, route of exposure, and physiological state (e.g., pregnant vs. nonpregnant). There are variations in metabolism due to genetic polymorphisms. There are also mechanisms to deconjugate BPA (Ginsberg and Rice, 2009), and these could be affected by polymorphisms in individuals. Some of these could affect only certain tissues, but not be obvious by measuring urinary BPA. Urinary BPA has been the preferred biomarker in BPA studies because of its practicality. Calafat et al. (2015) discussed considerations that are essential when evaluating exposure to nonpersistent, semivolatile environmental chemicals such as phthalates and phenols (e.g., BPA) and concluded that the biological and technical factors strongly support urine as the optimal matrix for measuring nonpersistent, semivolatile, hydrophilic environmental agents. The factors include representativeness of usual personal exposures and not recent extraneous exposures; minimization of contamination arising from collection, sampling, or analysis procedures; pharmacokinetics (e.g., fast metabolism and urine is the compartment with the highest concentrations of metabolites); and knowledge of intraindividual reliability over the biologic window of interest. Potential external contamination sources include sampling containers, preservatives, air, or dust (the latter reported by Longnecker et al. (2013)). There are various approaches to correct for urine dilution to avoid overestimation with highly concentrated urine samples and underestimation with dilute samples. Creatinine adjustment is widely used for urinary chemical testing and has been shown to vary by factors such as age, gender, and race/ethnicity. The easiest calculation is by reporting a chemical by mg/g of creatinine, but inclusion of creatinine in multivariate statistical regression is also used. The other method is to directly adjust for urine dilution/concentration by the specific gravity (SG) of the urine sample. Vandenberg et al. (2010a,b) examined more than 80 published human biomonitoring studies that measured BPA concentrations in human tissues, urine, blood,

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

BISPHENOL A BIOMARKER ISSUES IN BIOMONITORING

and other fluids, along with two toxicokinetic studies of human BPA metabolism. The biomonitoring studies examined included measurements in thousands of individuals from many developed and some developing countries, and these studies overwhelmingly detected BPA in individual adults, adolescents, and children. uBPA or free BPA was routinely detected in blood in the ng/mL range, and conjugated BPA was routinely detected in the vast majority of urine samples (also in the ng/mL range). These data indicate that the general population is exposed to BPA and is at risk from internal exposure to uBPA. The studies provide data that account for all sources and routes of exposures. Although oral exposure has been thought to be the major source, not all sources for BPA have been identified. The authors found that (1) the large number of biomonitoring studies are highly consistent and therefore reliable; (2) the detection rates and concentrations of BPA in urine and blood of environmentally exposed individuals are remarkably similar in studies performed in many laboratories using a variety of techniques, including highly accurate and sensitive methods as used in the US Centers for Disease Control and Prevention’s (CDC) national biomonitoring programs (Calafat et al., 2005; Calafat and Needham, 2008); and (3) there is no evidence to suggest that these studies have poor quality control (e.g., contamination from collection materials, breakdown of conjugates during storage, inadequate blanks). Overall, the reproducibility of these results showed that internal doses in humans for uBPA have a central measure of the distribution in the 0.5e3 ng/mL (equivalent to mg/L) range, but as much as 10 ng/mL. Vandenberg et al. (2010a,b) also evaluated two toxicokinetic studies conducted in 15 adults administered BPA (Volkel et al., 2002, 2005) that suggested human uBPA exposure is negligible, and determined that the studies had significant deficiencies and are directly contradicted by environmental exposure studies. Other studies described in this chapter have provided additional extensive evidence of exposure. The level of systemic BPA exposure, as represented by serum or plasma, may differ from exposure as represented by urinary BPA (Ginsberg and Rice, 2009; Vandenberg et al., 2014b; vom Saal and Welshons, 2014; Stahlhut et al., 2016), particularly in infants because of low activity of metabolic enzymes (Ginsberg and Rice, 2009). A remaining issue is the practicality of blood sampling in epidemiology. It is possible to reliably measure the various forms of BPA in blood (Vandenberg et al., 2014a), but there remains a debate about practicality (Calafat et al., 2015, 2016). Veiga-Lopez et al. (2015) conducted a fetal growth study based on maternal and cord plasma (see below in the Mother-Infant/Child Pairs

431

section) following the round robin laboratory methods discussed by Vandenberg et al. (2014a). The observed median uBPA in first and third trimester BPA was 0.66 and 3.0 mg/L plasma, respectively, whereas the umbilical cord plasma median was 0.19 mg/L. The respective 75th percentile levels were 1.5, 16.6, and 2.8 mg/L, and the respective 95th percentile levels were 32, 59, and 14.8 mg/L. The total BPA levels were only moderately higher, by factors of 5%e20%, because of the low level of glucuronidation. The limit of detection for both uBPA and glucuronidated BPA was 0.02 mg/L. Gerona et al. (2016) noted that most biomonitoring studies to date have estimated prenatal exposure to total BPA indirectly, using enzyme hydrolysis to cleave glucuronide and sulfate bonds with BPA, then quantifying uBPA. They used the direct analytical method, LC-MS/MS, to avoid the possibility of incomplete enzyme hydrolysis at higher BPA levels in a study of predominately low-income pregnant women (n ¼ 112) in their second trimester. They found universal and high exposure to uBPA and its metabolites: median concentrations were 0.25, 2.6, and 0.31 mg/g for uBPA, BPA glucuronide, and BPA sulfate, respectively. Median total BPA, 4.0 mg/g, was roughly twice that measured in US pregnant women in other studies. The 75th percentile level in this study was 13.9 mg/g. On average, total BPA consisted of 71% BPA in glucuronide form, 15% BPA in sulfate form, and 14% in uBPA. As BPA has a short average half-life of less than 6 h, a single measurement would be useful only if the environmental exposure is relatively constant over weeks or months, and issues of representativeness of longerterm exposures, temporal reliability, and stability after storage need to be considered. Nepomnaschy et al. (2009) evaluated the stability of BPA in urinary specimens after 22e24 years of storage and measured within-person temporal variability in urinary BPA. They concluded that the similar levels found in later sampling (see Section NHANES, below) provide indirect evidence that BPA is relatively stable during long-term freezer storage. These findings suggest that developmental effects of BPA exposure could be investigated with measurements from stored urine. Jusko et al. (2014) noted that exposure to BPA is episodic, varying in dose and duration. Because of its short half-life, an estimate of exposure based on a spot urine specimen is likely to misclassify individuals with regard to their average long-term exposure, for example, over 9 months of pregnancy. They evaluated the reproducibility of BPA concentration in serial urine specimens taken during pregnancy and noted that results indicate a high degree of within-person variability, which presents challenges for designing well-powered epidemiologic studies.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

432

25. BPA BIOMARKERS

EXPOSURE AND SELECTED OUTCOME STUDIES Analysis of health effects is an important use of surveys such as NHANES, although in general the epidemiological design is cross-sectional (exposure and outcome are measured at the same time) and, therefore, cannot be easily used for determining causality. Although questionnaire data on past use of tobacco and alcohol are valid retrospective data, chemicals that are quickly excreted, such as BPA, represent only a moment in time. Prospective studies on pregnant women and their children are presented in this chapter (in the subsections on Mother-Infant/Child Pairs and on Children, below). Urinary BPA in gestational samples taken during regular clinical visits have been compared to later outcomes, such as fetal growth, thyroid, neurodevelopment, and respiratory outcomes, which represent the largest number of studies, summarized in Tables 25.2e25.5. Other studies have also been published on other endocrine effects, metabolism, liver function, immune function, oxidative/nitrosative effects, and epigenetics, but are not discussed in this chapter.

LARGE GENERAL POPULATION BIOMONITORING PROGRAMS The following presents a brief description of some of the large biomonitoring programs that measured BPA in human fluids. The review is not meant to be comprehensive. Studies usually included other potential endocrine disruptors, such as phthalates, but the focus was placed on BPA. Summary of BPA levels are shown in Table 25.1.

National Health and Nutrition Examination Survey, United States In the United States, the Division of Laboratory Sciences of the CDC operates the National Biomonitoring Program (NBP), which also assesses the nutrition status of the US population (CDC, 2018a). Biomonitoring data are used to determine the presence and concentrations of chemicals in human blood, urine, breast milk, and saliva and to track exposure trends and impacts of public health programs. The NBP measures more than 300 environmental chemicals and nutritional indicators. The data and biomonitoring research are used to develop various studies and publications, including two key reports: (1) the National Report on Human Exposure to Environmental Chemicals, which is a series of ongoing assessments of the US population’s exposure to environmental

chemicals; and (2) the National Report on Biochemical Indicators of Diet and Nutrition in the US population, which is a series of publications that provide ongoing assessment of the U.S. population’s nutrition status. The NHANES is a program conducted by the National Center for Health Statistics of studies designed to assess the health and nutritional status of the noninstitutionalized civilian resident population of the United States (CDC, 2018b). The survey combines interviews and physical examinations. This information is used to estimate the prevalence of various diseases and conditions and to provide information for use in planning health policy. Urine BPA has been measured by NHANES in each 2-year cycle since 2003. In 2005, Calafat et al. (2005) provided the first reference range of human internal dose levels of BPA in a demographically diverse human population. BPA was measured in archived urine samples from a reference population of 394 adults in the United States selected from the Third NHANES (NHANES III, 1988e94) callback cohort, a nonrepresentative subset of NHANES III composed of approximately 1000 adults. The urine samples were all spot samples, collected at different times throughout the day. The concentration ranges of BPA were similar to those observed in other human populations. BPA was detected in 95% of the samples examined at concentrations 0.1 mg/L urine; the geometric mean (GM) and median concentrations were 1.33 mg/L (1.36 mg/g creatinine in urine, abbreviated below as mg/g) and 1.28 mg/L (1.32 mg/g), respectively; the 95th percentile concentration was 5.18 mg/L (7.95 mg/g). Gender and age group (<50 or 50 years of age) were not statistically significant predictors, but rural versus urban residence was. The adjusted GM of BPA for an urban resident (1.21 mg/L) was significantly lower than that for a rural resident (1.56 mg/L). Since 1999, NHANES has been conducted continuously with approximately 10,000 respondents from 30 locations in each 2-year data cycle. BPA is measured in 1/3 of the samples (Parker et al., 2018). This study is limited to adults aged 20 and over with complete data on BPA, creatinine, race/ethnicity, gender, age, poverty status, urbanization, education, and cigarette smoking (6608). Summary results for 2003e12 NHANES showed that the estimated median of BPA (mg/L) by gender and race/Hispanic origin, for adults, are as follows: maled non-Hispanic white, 2.00; Mexican American, 2.00; non-Hispanic black, 2.70; femalesdnon-Hispanic white, 1.6; Mexican American, 1.9; non-Hispanic black, 2.8. In a second study, Calafat and Needham (2008) assessed exposure to BPA in the US general population. Total (free plus conjugated) urinary concentrations of BPA were measured in 2517 participants 6 years of age in the 2003e04 NHANES study. Urine

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

433

LARGE GENERAL POPULATION BIOMONITORING PROGRAMS

TABLE 25.1

Urinary Bisphenol A (BPA) Occurrence in the General Population and in Pregnant Women

Study

Cohort, Location

Years

Calafat et al. (2008)

NHANESa subset, USA

2003e04

CDC (2018a) b

Age (years)/ Gestation (weeks)

N

Concentration, CreatinineAdjusted

Statistical Analysis/Comment

LSGMp 6 years

2514

2.6 mg/g

6e11 years

314

4.3 mg/g

12e19 years

713

2.8 mg/g

20e59 years

950

2.4 mg/g

60 years

537

2.3 mg/g

1296 \

2.8 mg/g

1228 _

2.4 mg/g

1469

8.0 mg/g

2009e10

>6 years

Ye et al. (2008)

MoBa subset Norway

1999e2008

Pregnant 110 of 17e18 weeks 65000

Mean 5.9 mg/g

Possible external contamination

Braun et al. (2011a)

HOME,c Cincinnati, OH, USA

2003e06

Pregnant

GMq

ICC ¼ 0.10 (for unadj ¼ 0.25) Correlation of log10 BPA Week 16 versus 26: R ¼ 0.12 (unadjusted BPA R ¼ 0.28) Week 16 versus birth: R ¼ 0.06 (unadjusted BPA R ¼ 0.21) Week 26 versus birth: R ¼ 0.12 (unadjusted BPA R ¼ 0.28)

389

16 weeks

1.7 mg/g

26 weeks

2.0 mg/g

Birth

2.0 mg/g

Casas et al. (2015, 2016), INMA,d Sabadell, Gascon Spain et al. (2015)

2004e06

Pregnant 12 and 32 weeks

462e470

Median 2.4 mg/g

ICC ¼ 0.14 (week 12 vs. week 32)

Braun et al. (2012)

EARTH,e Boston, MA, USA

2004e09

Pregnant

137  2 samples

GM 1.5 mg/L

ICC ¼ 0.12

Perera et al. (2012)

CCCEH,f New York City

1998e2003

Pregnant

361

GM

African American and Dominican

1.96 mg/L 3.94 mg/L (SG-adjusted)

3e4 year old Harley et al. (2013)

CHAMACOS,g Salinas, CA, USA

1999e2000

Pregnant

292

GM

Week 12 versus 32: R ¼ 0.25

1.1 mg/g

12 and 32 weeks

(SG-adjusted) 2.5 mg/g

5 year old Jusko et al. (2014)

h

Gen-R subset, Rotterdam, the Netherlands

2002e05

Pregnant

20 weeks

80 randomly Median selected from 2.9 mg/g 1024 w/ complete 3.0 mg/g sampling 3.0 mg/g

30 weeks

2.6 mg/g

All weeks 13 weeks

i

Philippat et al. (2014)

EDEN, France

2003e06

Pregnant 520 23e29 weeks

Median 2.4 mg/L

Lee et al. (2014)

MOCEHj

2006

Pregnant trimester 3

GM 1.9 mg/g

757

ICC ¼ 0.32

Continued

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

434 TABLE 25.1

25. BPA BIOMARKERS

Urinary Bisphenol A (BPA) Occurrence in the General Population and in Pregnant Womendcont’d

Years

Age (years)/ Gestation (weeks)

Concentration, CreatinineAdjusted

N

7e8 years

127

GM 1.02 mg/L

Study

Cohort, Location

Kim et al. (2014)

School pupils, Seoul, South Korea

Evans et al. (2014)

SFF-II,k multicenter in NY, USA

2002e05

Pregnant 10e39 years (mean 27)

157

Median 1.6 mg/g Mean 3.7 mg/g

Arbuckle et al. (2014, 2015)

MIREC,l Canada

2008e11

Pregnant Trimester 1

1890

GM

Statistical Analysis/Comment

0.91 mg/L (SG-adjusted) 1% uBPA at median BPA 13% uBPA at 95th percentile

Gerona et al. (2016)

San Francisco, CA, USA

2009e11

Pregnant

112

Median 5.23 mg/g 14% uBPA

Cantonwine et al. (2015)

Boston, MA and Philadelphia PA, USA

2006e08

Pregnant 10, 18, 26, 35 weeks

1695

GM 1.3e1.4 mg/g

Park et al. (2016)

KoNEHS,m South Korea

2009e11

19 years

2044

GM 2.01 mg/g

Health Canada (2017)

CHMS,n multicenter in Canada

2014e15

2560

GM

Buckley et al. (2018)

o

MSCEHS

0.93 mg/L

3e79 years

1998e2002

3e5 years

511

2.0 mg/L

6e11 years

511

1.2 mg/L

12e19 years

505

0.83 mg/L

Pregnant 159 25e40 weeks

Median 1.3 mg/L (regressionadjusted)

a

National Health and Nutrition Examination Survey. Norwegian Mother and Child Cohort Study. c Health Outcomes and Measures of the Environment. d Infancia y Medio Ambiente (Childhood and Environment). e Environment and Reproductive Health Study. f Columbia Center for Children’s Environmental Health. g Center for the Health Assessment of Mothers and Children of Salinas. h Generation - R. i Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant. j Mothers and Children’s Environmental Health. k Study for Future Families II. l Maternal-Infant Research on Environmental Chemicals. m Korean National Environmental Health Survey. n Canadian Health Measures Survey. o Mount Sinai Children’s Environmental Health Study. p Least squares geometric mean. q Geometric mean. b

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

Intersample time correlation Spearman R ¼ 0.17e0.26, P < .01 ICC ¼ 0.21

LARGE GENERAL POPULATION BIOMONITORING PROGRAMS

concentrations of total BPA differed by race/ethnicity, age, gender, and household income. BPA was detected in 92.6% and 57.4% of the persons, respectively. Least square geometric mean (LSGM) concentrations of BPA were significantly lower in Mexican Americans than in non-Hispanic blacks and non-Hispanic whites. LSGM concentrations for non-Hispanic blacks and nonHispanic whites were not statistically different. Females had statistically significantly higher BPA LSGM (2.8 mg/ L) concentrations than males (2.4 mg/L). Children (6e 11 years old) had higher concentrations (4.3 mg/L) than adolescents (2.8 mg/L), who in turn had higher concentrations than adults (2.4 mg/L). LSGM concentrations were lowest for participants in the high household income category (>$45,000/year). Lakind and Naiman (2011) also estimated BPA daily intakes in the United States based on the 2005e06 NHANES urinary data on BPA and its metabolites. Excretion of ingested BPA into urine, mainly as the glucuronide conjugate, is essentially complete in 24 hr. Therefore, total urinary BPA in a 24-hr urine sample approximates the BPA intake from the previous 24 hr. Associations between urinary BPA levels and items from the NHANES questionnaire and examination data that specifically related to packaged food/drink consumption, smoking, and specific medical procedures were evaluated. The median daily BPA intake was approximately 34-ng/kg body wt/day for the overall population, and 54-ng/kg body wt/day for 6e11-year-olds, the youngest group. Intakes for men were statistically significantly higher than for women, and there was a significant decrease in daily BPA intake with increasing age. Estimates of daily BPA intake have decreased compared with those from the 2003e04 NHANES. Consumption of soda, school lunches, and meals prepared outside the homedbut not bottled water or canned tunadwere associated with higher urinary BPA. More recently, Lakind and Naiman (2015) compared the 2003e04 to 2011e12 NHANES to examine temporal trends and assess the resiliency of the previous reported associations. The median daily intake for the overall population was approximately 25 ng/kg day, which represents a gradual decrease in exposure. Three approaches were assessed for their effect on trends and associations: (1) use of generic literaturebased 24-h urine excretion volumes, (2) use of creatinine adjustments, and (3) use of individual urine flow rate data from NHANES. Estimates of associations between lifestyle/demographic/dietary factors and BPA exposure revealed inconsistencies related to both NHANES survey year and the three approaches listed above. The authors noted that these results demonstrate the difficulties in interpreting urinary BPA data, despite efforts to account for urine dilution. Stahlhut et al. (2009) investigated the relationship between urine BPA concentration

435

and fasting time in 1469 adult participants in the 2003e04 NHANES. Because food is the predominant BPA exposure source, and BPA appears to be rapidly excreted, BPA levels in fasting individuals should decrease with increased fasting time. They estimated the BPA half-life for fasting times of <4.5 h, 4.5e8.5 h, and >8.5 h. Results showed that the overall half-life for the 0- to 24-hr interval was 43 h (95% confidence interval [CI], 26e119 h). Among those reporting fasting times of 4.5e8.5 h (n ¼ 441), BPA declined significantly with fasting time, with a half-life of 4.1 h (95% CI, 2.6e10.6 h). However, within the fasting time intervals of 0e4.5 h (n ¼ 129) and 8.5e24 h (n ¼ 899), no appreciable decline was seen. Fasting time did not significantly predict highest (>12 ng/mL) or lowest (below limit of detection) BPA levels. Overall, BPA levels did not decline rapidly with fasting time in this sample. The authors noted that this suggests substantial nonfood exposure, accumulation in body tissues such as fat, or both. Of course, delayed uptake from the gut (due to fat content and differences in gut motility) and diurnal patterns of kidney function are also likely factors, even after exclusion of subjects using laxatives and antidiarrheal medications or drinking coffee, tea, or carbonated beverages or using mints or lozenges during the fasting period. Nelson et al. (2012) analyzed data from the 2003e06 NHANES using multivariable linear regression to examine the association between urinary concentrations of BPA and multiple socioeconomic measures and race/ ethnicity. BPA was inversely associated with family income, higher in people who reported very low food security and received emergency food assistance. This association was particularly strong in children: 6e11year-olds whose families received emergency food had BPA levels 54% higher (95% CI, 13%e112%) than children of families who did not. Smaller and less consistent associations with education and occupation were observed. Mexican Americans had the lowest BPA concentrations of any racial/ethnic group. Income, education, occupation, and food security appear to capture different aspects of SEP that may be related to exposure to BPA and are not necessarily interchangeable as measures of SEP in environmental epidemiology studies. Differences by race/ethnicity were independent of SEP. Silver et al. (2011) noted that previous studies using data from the NHANES showed an inconsistent association between prevalence of self-reported type-2 diabetes mellitus (T2DM) and urinary BPA. The authors also used hemoglobinA1c (HbA1c) as a surrogate for T2DM with a larger subset of NHANES. They analyzed data from 4389 adult from three NHANES cycles (2003e08). T2DM was defined as having a HbA1c  6.5% or use of diabetes medication. Multivariate analysis of the total sample revealed that a twofold increase

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

436

25. BPA BIOMARKERS

in urinary BPA was associated with T2DM (OR ¼ 1.08, 95% CI 1.02e1.16). However, when each NHANES cycle was examined individually, a statistically significant association was only found in the 2003/04 cycle, OR ¼ 1.23. Shankar and Teppala (2011) also examined the association between urinary BPA levels and diabetes mellitus (type 1) using the NHANES 2003e08. Results showed that positive association was observed, independent of confounding factors such as age, gender, race/ethnicity, body mass index (BMI), and serum cholesterol levels. Compared to quartile 1 (referent), the adjusted (age, gender, race/ethnicity, BMI, and serum cholesterol level) OR of diabetes associated with quartile 4 was 1.68 (1.22e2.30) (P-trend ¼ .002). Prediabetes (5.7% e6.4% HbA1C or 100e125 mg/dL fasting blood glucose or 140e199 mg/dL 2-h blood glucose) was also associated (Sabanayagam et al., 2013). The adjusted odds ratio (AOR) was 1.34 (95% CI 1.03, 1.7) and was stronger among women and obese subjects.

Canadian Health Measures Survey The Canadian Health Measures Survey (CHMS) is an ongoing national direct health measures survey (Health Canada, 2017). Statistics Canada, in partnership with Health Canada and the Public Health Agency of Canada, launched the CHMS in 2007 to collect health and wellness data and biological specimens from a nationally representative sample of Canadians. Biological specimens were analyzed for indicators of health status, chronic and infectious diseases, nutritional status, and environmental chemicals. Four reports for four biennial cycles have been published on Human Biomonitoring of Environmental Chemicals in Canada in 2010, 2013, 2015, and 2017. Collection for cycle 5 began in January 2016 through the end of 2017. Data for Cycle 4 on 54 chemicals were collected from approximately 5700 Canadians aged 3e 79 years at 16 sites in 10 provinces across Canada. Selected findings on BPA concentrations expressed as the GMs of urine concentrations (mg/L) are shown as follows (adapted from Tables 9.1.1 and 9.1.2, Health Canada, 2017): Total 3e79 years, N-2560/2559, 1.0 mg/L; 0.93 mg/L creatinine-adjusted M 3e79 years, N-1273/1272, 1.2 mg/L; 0.92 mg/L creatinine-adjusted F 3e37 years, N-1287, 0.92; 0.94 mg/L creatinineadjusted 3e5 years, N-511, 1.2; 2.0 mg/L creatinine-adjusted 6e11 years, N-511/510, 1.1; 1.2 um/L creatinineadjusted 12e19 years, N-505, 1.1; 0.83 mg/L creatinine-adjusted

20e39 years, N-362, 1.1; 0.91 mg/L creatinineadjusted 46e59 years, N-311, 0.86; 0.78 mg/L creatinineadjusted 60e79 years, N-360, 1.1; 1.0 mg/L creatinine-adjusted.

Generation R Study, The Netherlands Various studies have reported on the Generation R study in Rotterdam, the Netherlands. The Generation R study biobank is a resource for epidemiological studies in children and their parents (Jaddoe et al., 2007). It is a population-based prospective cohort study in the Netherlands from fetal life until young adulthood. It focuses on four primary areas of research: (1) growth and physical development; (2) behavioral and cognitive development; (3) diseases in childhood; and (4) health and healthcare for pregnant women and children. There are 9778 mothers enrolled (with a delivery date from April 2002 until January 2006) in the study. Prenatal and postnatal data collection has been conducted by physical examinations, questionnaires, interviews, ultrasound examinations, and biological samples. Major efforts have been conducted for collecting biological specimens including DNA, blood for phenotypes, and urine samples. Together with detailed phenotype measurements, these biological specimens form a unique resource for epidemiological studies focused on environmental exposures, genetic determinants, and their interactions in relation to growth, health, and development from fetal life onward. Compared to other birth-cohort studies, the size of the Generation R study cohort is not larger, but the measurements are more detailed and the study group has a large ethnic variety. An update on the Generation R study was provided by Kooijman et al. (2016). Response at baseline was 61%, and general follow-up rates until the age of 10 years were around 80%. Data collection in children and their parents include questionnaires, interviews, detailed physical and ultrasound examinations, behavioral observations, lung function, magnetic resonance imaging, and biological sampling. Genome and epigenome wide association screens are available. Ye et al. (2008) reported on biological monitoring data from 100 pregnant women, a subset of participants in the Generation R study. The unadjusted and creatinine-adjusted concentrations were reported and compared to NHANES and other studies. The data showed similar exposure to BPA. Among the 100 pregnant women, BPA was detectable among 82% of samples. The creatinine-adjusted median concentration was 1.6 mg/g Cr, and the unadjusted median concentration was 1.2 mg/L. Urinary free BPA accounted for only a small percentage of total BPA.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

LARGE GENERAL POPULATION BIOMONITORING PROGRAMS

Philips et al. (2018) examined first trimester bisphenol (BPX) and phthalate urine concentrations, including BPX and phthalate replacements, and found nutritional-, sociodemographic-, and lifestyle-related determinants. The authors measured first trimester BPX, phthalate, and creatinine urine concentrations in samples collected in 2004e05, with a median gestational age of 12.9 weeks in a population-based prospective cohort of 1396 mothers in the Netherlands. They examined associations of potential determinants with logtransformed BPX and phthalate concentrations. Outcomes were back-transformed. Nutritional analyses were performed in a subgroup of 642 Dutch participants only, as the Food Frequency Questionnaire was aimed at Dutch food patterns. Results showed that bisphenol A, bisphenol S (BPS), and bisphenol F (BPF) were detected in 79.2%, 67.8%, and 40.2% of the population, respectively. Bisphenol S and F are produced as alternatives to BPA, see Food Packaging and Bisphenol A Alternatives, below. The authors noted that bisphenol S and F exposure was highly prevalent in pregnant women in the Netherlands as early as 2004e05. Although associations of dietary and other key factors with BPX and phthalate concentrations were limited, adverse lifestyle factors including obesity and the lack of folic acid supplement use seem to be associated, likely as an indirect effect, with higher phthalate concentrations in pregnant women. The major limitation was the availability of only one urine sample per participant. The authors noted that previous studies among pregnant women generally reported higher levels of BPXs and phthalates to be associated with lower socioeconomic status, younger maternal age, and smoking (Arbuckle et al., 2014; 2015; Casas et al., 2013), likely due to food choices, but results are inconsistent (Arbuckle et al., 2014; Berman et al., 2014). Being overweight has also been suggested as a determinant of BPX and phthalate levels (Valvi et al., 2013). Likewise, this association is probably due to an indirect effect on food choices. Jusko et al. (2014) determined the reproducibility of BPA using three urine specimens collected from 80 pregnant women selected as a random sample of the 1024 women with three urine specimens and complete data. Total maternal BPA concentrations were detectible in all specimens. On average (SD), maternal urine specimens were collected at 13 (1.7), 20 (0.7), and 30 (0.7) weeks of gestation, and median BPA concentrations were 1.1, 1.5, and 1.6 mg/L (3.0, 3.0, and 2.6 mg/g creatinine) across these three sampling periods. BPA concentrations in the present study were higher than those reported in a previous analysis of a subset of pregnant women in the Generation R study who had only one urine specimen collected after 20 weeks of pregnancy, likely owing to the greater proportion of older, Dutch, and better educated women participating in the present

437

study, factors that have been also been associated with higher BPA concentrations in the Generation R study. In contrast, in the NHANES surveys BPA is higher in women of lower socioeconomic class (Calafat and Needham, 2008). To address the issue of potential contamination, uBPA concentrations in 26 samples having high total BPA were quantified, and all but one sample were found to have uBPA that comprised 1%e2% of the total BPA concentration. Pair-wise measures of BPA concentrations were moderately correlated (0.13  rspearman 0.49), regardless of whether they were expressed on a volumetric or creatinine-adjusted basis. BPA measurements closer in time were more strongly correlated, although this was not true for the creatinine basis measures. The intraclass correlation coefficient (ICC, the percent of total variance explained by between-person variance) for the three sampling events were 0.32 (95% CI: 0.18, 0.46), and on a creatinine basis, 0.31 (95% CI: 0.16, 0.47), indicating low reproducibility.

Norwegian Mother and Child Cohort Study, Norway The MoBa study was planned in the 1990s with the objective of testing specific etiological hypotheses by estimating the association between exposures (including genetic factors) and diseases, aiming at prevention and to collect data on as many relevant exposures and health outcomes as feasible (Magnus et al., 2006). It is a prospective birth cohort enrolling pregnant women throughout Norway from 1999 to 2008 (Rønningen et al., 2006). Biological material is to be collected from women in 100,000 pregnancies. In addition, cord blood from their newborn infants and samples from 80,000 fathers may result in more than 380,000 unique sample sets for long-term storage. In addition to biological materials, detailed questionnaire data are collected during pregnancy and as the child ages. Additional health outcome information is available through linkage to Norwegian national health registries. The overall aim is to study the effects of genetic and environmental factors on pregnancy outcomes and later health of the children as well as the parents. The study includes collection of questionnaires and registry information and aims at having DNA for all participants as well as biological samples from pregnant women to assess environmental exposures. The MoBa Biobank is charged with long-term storage of more than 380,000 biological samples from pregnant women, their partners, and their children for up to 100 years. Biological specimens include whole blood, plasma, DNA, and urine; samples are collected at 50 hospitals in Norway. The unique combination of biological specimens, DNA, and questionnaire data

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

438

25. BPA BIOMARKERS

makes the MoBa Study a resource for many future investigations of the effects of genetic and environmental factors on pregnancy outcome and on human morbidity. Ye et al. (2008) measured BPA in 10 pooled urine samples representing 110 pregnant women who participated in the MoBa study in 2004. Daily intakes were estimated from urinary data and compared with RfDs and TDIs. The authors found that MoBa women had a higher mean BPA concentration (4.50 mg/L) than the pregnant women in the Generation R study in the Netherlands and the NHANES in the United States. The higher levels of may have been due to consumption of canned food, especially fish/seafood. In the MoBa study whereby over 65,000 urine specimens were collected from pregnant women, Longnecker et al. (2013) encountered unexpectedly high concentrations of total and free BPA, with 24% containing more than 10 ng/mL of total BPA, suggesting external contamination. Subsequent investigation of the source of free BPA in the specimens showed that under typical conditions used to collect urine specimens in an epidemiologic study of outpatients, contamination with BPA occurred by two separate mechanisms, one due to the preservative, and the other possibly via dust in clinics.

Other General Population Exposure Studies in Various Countries Calafat et al. (2005) also presented briefly the urinary BPA levels in various populations in Southeast Asia reported by various researchers: (1) In Japan for 1992, 1999, 2002, and 2003, BPA was measured in urine samples from two different groups of university students in 1992 (n ¼ 50, 92% male) and 1999 (n ¼ 56, 87.5% male) with most of the BPA found in the urine as the glucuronide conjugate, and the median urinary BPA levels were approximately 2.2-fold higher than in 1999. (2) BPA glucuronide was detected in all of the urine samples collected from 48 female Japanese college students at concentrations ranging from 0.2 to 19.1 ng/mL, with a median level of 1.2 mg/L (0.77 mg/g). (3) In 2004, a median daily urinary excretion of BPA of 1.2 mg/day and an estimated maximum daily intake of BPA to be 0.23 mg/ kg/day were reported based on the measurement of BPA in 24-hr urine samples collected from 36 men. This estimated intake was lower than the temporary TDI (10 mg/kg) set by the European Commission’s Scientific Committee in Food in 2002. (4) In Korea for nonoccupational exposure assessment, urinary levels of BPA in a group of 73 adults showed a GM concentration of BPA of 9.54 mg/L (8.91 mg/g). Park et al. (2016) reported that BPA urinary concentrations in Korea may be higher than those in other Asian countries and North America, but lower than or

similar to those in European countries. The current study included a total of 2044 eligible adults of all ages and gender. The GM of preadjusted (adjusted) urinary BPA concentrations was 1.83 mg/L (2.01 mg/g) for subjects of all ages, and there was no statistically significant difference in BPA concentrations between males (1.90 mg/L, 1.87 mg/g) and females (1.76 mg/L, 2.16 mg/g). In Sweden, phthalates and phenolic substances were investigated in urine samples from first-time mothers in Uppsala County, collected between 2009 and 2014 in the POPUP study (Persistent Organic Pollutants in Uppsala Primiparas) conducted by the Swedish National Food Agency (Gyllenhammar et al., 2017). The aim was to investigate if measures to decrease production and use of some of these nonpersistent chemicals have resulted in decreased human exposure, and to determine if exposure to replacement chemicals has increased. A total of 178 women were included in the data set; 30 women were sampled every year between 2009 and 2014 and the participating rate was 52%. BPA showed a downward trend, with a half-life of 6.6 years, whereas BPF, identified as one of the substitutes for BPA, showed an increasing trend, with a doubling in mean concentrations every 3.8 years. The authors noted that declining temporal trends for BPA has also been seen in the US NHANES study between 2003 and 2012 (Lakind and Naiman, 2015) and also in young Swedish men between 2010 and 2013 (Jo¨nsson et al., 2014). When compared with other studies, the authors indicated that median concentrations of BPA were in the same range as in young Swedish women and about 30% lower compared with Swedish mothers (Jo¨nsson et al., 2014; Larsson et al., 2014). Concentrations of BPA found in the study were also lower compared to recent studies of 684 women in other European countries sampled in 2008 and 2011e12 (Covaci et al., 2015; Guidry et al., 2015).

PREGNANT WOMEN, MOTHEReINFANT/ CHILD PAIRS, INFANTS, CHILDREN Pregnant Women Summary BPA levels for each study can also be found in Table 25.1. Braun et al. (2011a) estimated the variability and predictors of serial urinary BPA concentrations taken during pregnancy (around 16 and 26 weeks of gestation) and at birth. Data were collected from pregnant women participating in the Health Outcomes and Measures of the Environment (HOME) Study, an ongoing prospective birth cohort in the Cincinnati, Ohio, metropolitan area designed to examine low-level environmental

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

toxicant exposure. Beginning in March 2003, through 2006, women were identified from seven prenatal clinics associated with three hospitals. Eligibility criteria for enrollment in the study included 19 weeks of gestation, age 18 years, living in a house built before 1978, negative HIV status, and not taking medications for seizure or thyroid disorders. Letters were mailed to 5184 women who were 18 years of age and living in a house built before 1978. Of the 1263 eligible responding women, 468 enrolled in the study (37%), but 67 dropped out before delivery, and 3 had stillbirths. This analysis was further restricted to 389 mothers who delivered singleton children between March 2003 and January 2006. Women provided three spot urine samples collected at approximately 16 and 26 weeks of gestation at prenatal care appointments and at birth. Results showed that the GM creatinine-standardized concentrations (micrograms per gram, mg/g) were 1.7 (16 weeks), 2.0 (26 weeks), and 2.0 (birth). Log10-transformed urinary BPA concentrations were weakly correlated at 16 and 26 weeks (r ¼ 0.28), 26 weeks and birth (r ¼ 0.28), and 16 weeks and birth (r ¼ 0.21). Correlations between creatinine-standardized urinary BPA concentrations were even lower at 16 and 26 weeks (r ¼ 0.12), 26 weeks and birth (r ¼ 0.12), and 16 weeks and birth (r ¼ 0.06). The ICC for serial urinary BPA measurements indicated poor reproducibility in analyses using unstandardized (ICC ¼ 0.25) and creatinine-standardized concentrations (ICC ¼ 0.10). Creatinine-standardized BPA concentrations exhibited low reproducibility (ICC ¼ 0.11). The ICC was used to assess BPA variability and estimated associations between log10-transformed urinary BPA concentrations and demographic, occupational, dietary, and environmental factors, using mixed models. Only maternal education and occupation was associated. By occupation, cashiers had the highest BPA concentrations (GM: 2.8 mg/g) and serum cotinine, a tobacco smoke metabolite, was associated with higher BPA concentrations. In children almost 99% of BPA exposure was estimated to come from dietary sources. Dietary findings are further discussed below, in the Food packaging and BPA alternatives section. The authors noted that future studies should standardize or adjust for the timing of urine collection or measure BPA at multiple times to minimize biases due to within-day and within-woman variability of urinary BPA and creatinine concentrations. Braun et al. (2012) also characterized the variability of urinary phthalate and BPA concentrations before and during pregnancy. No prior study had examined the same woman before and during pregnancy. Women 18e45 years of age were recruited from clinical partners seeking evaluation and treatment for infertility at

439

the Massachusetts General Hospital Fertility Center in Boston between November 2004 and December 2009 for a prospective open-cohort study, the Environment and Reproductive Health (EARTH) Study. For BPA analyses, 137 women provided two or more urine samples before and during pregnancy. They were predominately white, highly educated, and had a mean (SD) of 35  4.1 years of age at enrollment. Before pregnancy, women provided between 2 and 13 urine samples (median, 3 samples) during a period of <1e110 weeks after enrollment (median, 12 weeks). During pregnancy, a median of three samples was collected. Results showed that urinary BPA concentrations were variable before and during pregnancy, ICC ¼ 0.12, which is similar to observations in studies with multiple samples during pregnancy. In the EDEN motherechild cohort (Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant) recruited in Nancy and Poitiers, France, a subgroup of 587 pregnant women were tested once for urinary BPA and phthalates between the 23rd and 29th weeks of gestation during 2003e06 (Philippat et al., 2014). Median BPA adjusted by statistical regression for creatinine, as well as day and time of sampling, gestational age, duration of storage at room temperature, and year of analysis, was 2.4 mg/L. Occupational and nonoccupational contact with paper receipts was positively associated with BPA in conjugated (glucuronidated þ sulfated) form after adjustment for demographic characteristics. The author noted that recent consumption of foods and beverages likely to be contaminated with BPA was infrequent among participants. Arbuckle et al. (2014, 2015) reported on free and conjugated forms of BPA during pregnancy in about 1890 first-trimester urine samples from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a large multicenter cohort study of Canadian pregnant women. Study participants tended to be well educated, > 30 years of age, born in Canada, had never smoked, had an underweight or normal BMI prior to pregnancy, and had a parity of 0 or 1. Results showed that the glucuronides of BPA were the predominant forms measured (detected in 95% of samples), whereas the free forms were detected in 43% of samples. The GM of SG-adjusted urinary BPA glucuronide was 0.91 mg/ L. On average, only about 1% of the total BPA was present in the unconjugated form. However, at the 95th percentile level of total BPA the percentage of uBPA versus total BPA was 12%. Significant predictors of BPA included maternal age <25, current smoking, low household income, and low education level. The results from this study represent the largest nation-level data on urinary concentrations of free and conjugated forms of BPA in pregnant women.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

440

25. BPA BIOMARKERS

Teeguarden et al. (2016) evaluated 30 healthy pregnant women for total BPA exposure over a 30-h period comprising one-half day in the field and 1 day in a clinical setting. BPA and its metabolites were measured in serum and total BPA was measured in matching urine samples, including sampling outside the clinical setting. It was also intended to identify potential explanations for previously reported and anomalously high serum BPA concentrations. The 30 pregnant volunteers were recruited for the study from the Salt Lake City, UT metropolitan area in 2014. Eligibility included no tobaccoealcoholedrug use, 18e40 (mean 26.5) years of age, and being at 15e35 (mean 23.7) weeks of a normal, low-risk pregnancy, with normal GI tract, kidney, and liver function, as determined by clinical laboratory tests, medical history, and physical examination. Volunteers were not taking medications that alter hepatic glucuronidation/ sulfonation or renal elimination, were HIV- and hepatitis-free, and had not undergone dental procedures in the 2 days preceding the study. Two cohorts were recruited from a pool of 116 candidates. A 20-member BPA cohort with the highest potential for exposure to BPA was selected based on the screening survey to assess exposure to BPA by ingestion of canned foods and handling of cash register receipts. Serum BPA levels were assessed in samples with a high corresponding urinary BPA result. The mean total exposure was similar to that in NHANES. Women working as cashiers did not have higher total BPA exposure. BPA was detected in some serum samples (0.25e0.51 ng/mL) but showed no relationship to total BPA in corresponding urine samples, no relationship to total BPA exposure, and had uBPA fractions of 60% e80%, consistent with established criteria for sample contamination. The authors concluded that typical exposures of North American pregnant women produce internal exposures to BPA in the picomolar range. They also suggested that previously published human biomonitoring studies of BPA in pregnant women that reported serum uBPA/total BPA ratios much greater than 15% are probably the result of contamination during sampling, and the reported concentrations appear unrelated to typical exposures in the general population of pregnant women. However, the findings, below, of Veiga-Lopez et al. (2015), following the round robin methods discussed by Vandenberg et al. (2014a), partly contradict this conclusion.

MothereInfant/Child Pairs The study of mothereinfant/child pairs enables the prospective type of epidemiological study design. Prospective studies are a superior design because the

exposure metrics are established before the outcome is measured. This helps to avoid misclassification of exposure and some aspects of confounding. The studies mostly examined fetal growth, neurodevelopment, and thyroid and respiratory outcomes, summarized in Tables 25.2e25.5. A large number of studies has been published from the prospective HOME birth cohort (see above, in the section on studies of Pregnant Women), which measured a large number of chemicals. Spanier et al. (2012) compared BPA concentrations in serial maternal urine samples of 398 mothereinfant pairs and assessed parent-reported child wheeze every 6 months for 3 years. Results showed that for 365 children for which both BPA and respiratory data were available, BPA was detected in 99% of maternal urine samples during pregnancy (16 and 26 weeks of gestation), with a mean prenatal creatinine-adjusted GM ¼ 2.4 mg/g. In multivariate analysis, a 1-unit increase in logtransformed creatinine-standardized mean prenatal BPA concentration was not significantly associated with child wheeze from birth to 3 years of age. Potential confounder data included socioeconomic factors, race/ ethnicity, season, familial and child history of allergy, pet ownership, insect exposure, urban/suburban/rural residence, and maternal cotinine, a surrogate for tobacco use. Mean prenatal BPA above versus below the median was positively associated with wheeze at age 6 months and AOR of 2.3 (95% CI: 1.3, 4.1), but not at later (12, 18, 24, 30, and 36 months) time points. In secondary analyses evaluating associations of early and late prenatal BPA concentration separately, urinary BPA measured at 16 weeks gestation were associated with wheeze (AOR 1.2, 95% CI 0.99, 1.5), but not BPA from 26 weeks of gestation or at birth. In this regard it is of interest that BPA levels in the two gestational samples were only weakly correlated (r ¼ 0.18, P ¼ .03). Discussion presented below (Donohue et al., 2013) suggests that urinary levels may not be as representative at later gestational time points of BPA because of increasing retention in the fetoplacental unit as gestation nears term. A follow-up study (Spanier et al., 2014) tracked the children through age 5 years, adding spirometry data for forced-expiratory-volume-in-1-second (FEV1) from testing at ages 4 (N ¼ 155) and 5 (N ¼ 193). There was a combined total of 208. Mean maternal BPA was associated with FEV1 at age 4 (b ¼ 14, 95% CI, 24, 4, P ¼ .007), but not at age 5. Child BPA at 4 and 5 was not associated with FEV1. The degree of association was similar with the 16-week and the 26-week gestational samples. Yolton et al. (2011) examined the association of prenatal exposure to BPA in the HOME study with data from a Neonatal Intensive Care Unit Network Neurobehavioral

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

441

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

TABLE 25.2

Association of Gestational Urinary Bisphenol A (BPA) With Human Fetal Growth, as Measured at Birth

Study/Cohort

Design

Snijder et al. (2013) Generation R, Netherlands

Maternal-child pairs (prospectivelongitudinal)

Sampling Timeline

N

Test/Effect

Each trimester 2002e06

80 with all 3 samples

Fetal growth at birth >4.2 versus < 1.54 mg/g

Effect Difference

Head circumference

3.9 cm (2.6 SD)

Birth wt

683 g (1.7 SD) NS

Philippat et al. (2012) EDEN,a France

Maternal-child pairs (prospectivelongitudinal)

22e29 weeks gestation 2003e06

560

Fetal growth

Veiga-Lopez et al. (2015) U Michigan Hospital, Ann Arbor, MI, USA

Maternal-child pairs (prospectivelongitudinal)

First and third trimester blood sampling

80

Birth weight First trimester plasma BPA Female pregnancy

183 g/twofold uBPAc (P < .005) 607 g/10-fold uBPA (P ¼ .0093)

Male pregnancy

NS

Third trimester Plasma BPA Female pregnancy

96 g/twofold uBPA (P < .05) 318 g/10-fold uBPA (P ¼ .034)

Male pregnancy

NS

Gestation time Third trimester plasma BPA

Casas et al. (2016) INMA-Sabadell,b Spain

Maternal-child pairs (prospectivelongitudinal)

12, 32 weeks gestation 2004e06

470

Female pregnancy

1.1 d/2-fold BPA

Male pregnancy

NS

Fetal growth, by ultrasound

NS

Birth weight Boys

21.6 g/mg/g BPA (NS)

Girls

11.0 g/mg/g BPA (NS)

NS ¼ not statistically significant; SD ¼ standard deviation a Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant. b Infancia y Medio Ambiente. c unconjugated BPA.

Scale, assessed during a postnatal visit at 5 weeks old. They did not find evidence of an association among the 350 mother/infant pairs. Braun et al. (2009) examined the association between prenatal BPA exposure and behavior in 2-year-old children and investigated whether gender modified the association. Study data were obtained from the HOME Study cohort. Child behavior was assessed using the second edition of the Behavioral Assessment System for Children-2 (BASC2). The association between prenatal BPA concentrations and BASC-2 scores was analyzed using linear regression. Median BPA concentrations among the 249

mothers included in this first set of analyses were 1.8 (16 weeks), 1.7 (26 weeks), and 1.3 (birth) ng/mL. Mean (SD) BASC-2 externalizing and internalizing scores (see next paragraph) were 47.6  7.8 and 44.8  7.0, respectively. After adjustment for confounders (maternal age, race, education, mental health, household income, marital status, and a care-giving score), log10-transformed mean prenatal BPA concentrations were associated with externalizing scores, but only among females (b ¼ 6.0; 95% CI, 0.1e12.0). In contrast, the trend for boys was inverse. Notably, the statistically nonsignificant trends for internalizing behavior

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

442 TABLE 25.3

25. BPA BIOMARKERS

Association of Gestational Urinary Bisphenol A (BPA) With Human Neonatal Thyroid Function

Study/Cohort

Design

Chevrier et al. (2013) CHAMACOSa Salinas, CA, USA

Maternal-child pairs (prospective-longitudinal)

Romano et al. (2015) HOME,b Cincinnati OH, USA

Maternal-child pairs (prospective-longitudinal)

Sampling Timeline 12, 26 week gestation 1999e2000

16, 26 week gestation 2003e06

N/Age

Test/Effect

476

TSHc

181

Effect Difference (95% CI)

Boys, 12 þ 26 week BPA

9.9%/log2 (16%, 3.5%)

Boys, 12 week BPA

NS

Boys, 26 week BPA

9.3%/log2 (16%, 1.7%)

Girls

NS

Other thyroid hormones

NS

TSH Boys

NS

Girls, 26 week BPA

43%/10-fold [ (60%, 18%)

Girls, 16 week BPA

NS/10-fold [

Triiodothyronine

Aung et al. (2017) Boston, MA and Philadelphia, PA

Maternal-child pairs (prospective-longitudinal)

10, 18, 26, 35 week gestation

116 preterm neonates

2006e08

323 term neonates

Girls, 16 þ 26 week BPA

13%/10-fold [

Other thyroid hormones

NS

TSH

8.2%/interquartile range

NS ¼ not statistically significant; CI ¼ confidence interval a Center for the Health Assessment of Mothers and Children of Salinas. b Health Outcomes and Measures of the Environment. c TSH.

exhibited a similar patterndwith higher maternal BPA girls had a higher score and boys had a lower score. Compared with 26-week and birth concentrations, BPA concentrations collected around 16 weeks were more strongly associated with externalizing scores among all children (b ¼ 2.9; 95% CI, 0.2e5.7), and this association was stronger in females (b ¼ 4.8; 95% CI, 1.3e8.3) than in males. Among all children, measurements collected at  16 weeks showed a stronger association (b ¼ 5.1; 95% CI, 1.5e8.6) with externalizing scores than did measurements taken at 17e21 weeks (b ¼ 0.6; 95% CI, 2.9e4.1). Externalizing and internalizing behaviors are problem behaviors, summarized as composite scores. The former includes outwardly directed behaviors, such as fighting, disobedience, stealing, and vandalism. The latter behaviors are focused inward, such as fear and withdrawal. A positive score means more problems. Braun et al. (2011b) continued their follow-up of the HOME study by examining behavior and executive function of 3-year-old children of 244 enrolled mothers. In addition to the three maternal spot urine samples, children’s spot urine samples were collected at 1, 2,

and 3 years of age during clinic or home visits, between 2004 and 2009. For statistical analysis, the authors characterized gestational and childhood BPA exposures by using the mean BPA concentrations of two urine samples from each mother and child. Behavior and executive function were measured by using the BASC-2 and the Behavior Rating Inventory of Executive FunctionPreschool (BRIEF-P). BPA was detected in >97% of the gestational (median 2.0 mg/L) and childhood (median 4.1 mg/L) urine samples. Overall correlation of each individual’s paired samples (i.e., early vs. later gestation, maternal vs. child, and the child’s sequential samples) was weak: a Pearson R statistic < 0.25 or with creatinine-adjusted concentrations, a Pearson R < 0.18. With adjustment for confounders, each 10-fold increase in gestational BPA concentrations was associated with more anxious and depressed behavior on the BASC-2 and poorer emotional control and inhibition on the BRIEF-P. The magnitude of the gestational BPA associations differed according to child gender; BASC2 and BRIEF-P scores increased from 9 to 12 points among girls, but changes were null or negative among boys. Hyperactivity among girls was increased, b ¼ 9.1

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

443

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

TABLE 25.4

Association of Urinary Bisphenol A (BPA) With Human Neurobehavioral Development

Study/Cohort

Sampling Timeline

Design

Braun et al. (2009) Maternal-child HOMEa Study pairs Cincinnati, OH, USA (prospectivelongitudinal)

Maternal-child Braun et al. (2011b) HOME Study pairs Cincinnati, OH, USA (prospectivelongitudinal)

16, 26 week gestation 2004e06

16, 26 week gestation 2004e06 1,2,3 year 2004e09

N/Age

Test/Effect

Slope or Rate Ratio (95% CI)

249 2 year

BASC-2h

per log10 [ maternal BPA

Externalizing behavior

b ¼ 2.9 (0.2, 5.7)

(16 week BPA only)

b ¼ 5.1 (1.5, 8.6)

Internalizing behavior

NS

BASC-2

per 10-fold [ maternal BPA

Internalizing behavior

Primarily girls

Hyperactivity, girls

b ¼ 9.1 (3.1, 15); child BPA was NS

BRIEF-Pi

per 10-fold [ maternal BPA

244 3 year

Emotional Control, girls b ¼ 9.1 (2.8, 15); child BPA was NS Stacy et al. (2017) Maternal-child HOME Study pairs Cincinnati, OH, USA (prospectivelongitudinal)

Harley et al. (2013) CHAMACOSb Salinas, CA, USA

Maternal-child pairs (prospectivelongitudinal)

16, 26 week gestation 2004e06 1e8 year 2004e15

14, 26 week gestation 1999e2000

228 8 year

292 7e9 year

BASC-2

per 10-fold [ maternal BPA

Externalizing behavior Boys

NS

Girls

b ¼ 6.2 (0.8, 11.6)/10-fold [ maternal BPA

Boys

b ¼ 3.9 (0.6, 7.2)/10-fold [ 8 year BPA

Girls

NS

BASC-2

Continuous variable analysis

Externalizing behavior

NS

Internalizing behavior

NS

Psychomotor

Third tertile versus First

1 year

b ¼ 4.3 (8.1, 0.41)

4 year

NS

Hyperactivity

IRRn ¼ 1.7 (1.1, 2.7) for 10-fold [ maternal BPA

4 year

Primarily boys

7 year

NS

5 year 2004e09

Casas et al. (2015) INMA-Sabadellc Spain

Perera et al. (2012) CCCEHd New York City

Maternal-child pairs (prospectivelongitudinal)

Maternal-child pairs (prospectivelongitudinal)

12, 32 weeks gestation 2004e06

34 week gestation; 3e4 year 1998e2003

382 1 year 365 4 year 361 7 year

198 3e5 year

j

CBCL

4th quartile versus lower quartiles

Emotionally Reactive Boys

RRm ¼ 1.6 (1.1, 1.5)

Anxious/Depressed Girls

RR ¼ 0.75 (0.57, 0.99)

Aggressive Behavior Boys

RR ¼ 1.3 (1.1, 1.5)

Girls

RR ¼ 0.82 (0.70, 0.97) Continued

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

444 TABLE 25.4

25. BPA BIOMARKERS

Association of Urinary Bisphenol A (BPA) With Human Neurobehavioral Developmentdcont’d

Study/Cohort

Sampling Timeline

Design

Evans et al. (2014) Maternal-child SFFIIe pairs New York multicenter (prospectivelongitudinal)

10e39 week (mean ¼ 27) gestation 2002e05

N/Age

Test/Effect

Slope or Rate Ratio (95% CI)

125 pairs with detected maternal BPA 6e10 year

CBCL

per natural log BPA

Externalizing behavior Boys

b ¼ 0.35, P ¼ .05

Girls

NS

Internalizing behavior Boys

b ¼ 0.45, P ¼ .02

Girls

NS

Philippat et al. (2017) Maternal-child pairs EDEN,f France (prospectivelongitudinal)

23e29 week gestation 2003e06

464 5e6 year

Hyperactivity inattention

IRR ¼ 1.08 (1.01, 1.14)

Nakiwala et al. (2018) Maternal-child pairs EDEN,f France (prospectivelongitudinal)

23e29 week gestation 2003e06

452 5e6 year

IQ (WPPSI-3k)

NS (continuous variable analysis)

Tewar et al. (2016) 2003e04 NHANESg

8e15 year 2003e04

460 8e15 year

ADHDl

> versus < median BPA

All children

AORo ¼ 5.7 (1.4, 86)

Boys

AOR ¼ 11 (1.4,20)

Girls

AOR ¼ 2.8 (0.4, 21)

Li et al. (2018) Guangzhou, China

Cross-sectional

case-control

6e12 year old not stated

465 6e12 year

ADHD boys and girls quartile 2 versus 1

AOR ¼ 1.8 (0.95, 3.4)

quartile 3 versus 1

AOR ¼ 7.4 (3.9, 14)

quartile 4 versus 1

AOR ¼ 9.4 (4.9, 18)

quartiles 2, 3, 4 versus 1 Boys

AORs ¼ 1.8, 9.1, 10

Girls

AORs ¼ 0.96, 3.4, 4.6

NS ¼ not statistically significant. a Health Outcomes and Measures of the Environment. b Center for the Health Assessment of Mothers and Children of Salinas. c Infancia y Medio Ambiente. d Columbia Center for Children’s Environmental Health. e Study for Future Families II. f Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant. g National Health and Nutrition Examination Survey. h Behavior Assessment System for Children, second Edition. i Behavior Rating Inventory of Executive Function-Preschool. j Child Behavior Checklist. k Wechsler Preschool and Primary Scale of Intelligence. l Attention-Deficit/Hyperactivity Disorder. m Rate Ratio. n Interquartile Rate Ratio. o Adjusted Odds Ratio.

(95% CI: 3.1, 15), but was decreased among boys, b ¼ 6.3 (95% CI: 12, 0.6). Anxiety and depression were also associated with BPA among girls. Associations between childhood BPA exposure and neurobehavior were largely null and not modified by child gender. Overall, gestational BPA exposure affected behavioral

and emotional regulation domains (anxiety, hyperactivity, emotional control, and behavioral inhibition) at 3 years of age, especially among girls, in a manner consistent with their previous findings. A follow-up study of 228 motherechild pairs from the HOME Study (Stacy et al., 2016) found that each

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

445

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

TABLE 25.5

Association of Urinary Bisphenol A (BPA) With Human Respiratory Outcomes Sampling Timeline

N/Age

Test/Effect

Maternal-child pairs (prospectivelongitudinal)

16, 26 week gestation 2004e06

398 every 6 mo 6 mo- 3 year

Mean prenatal BPA versus 6 mo wheeze, > versus < median BPA 16 week gestation BPA versus wheeze at 6 mo - 3 year, per log10 BPA 26 week gestation BPA versus wheeze at 6 mo - 3 year, per log10 BPA

Maternal-child pairs (prospectivelongitudinal)

16, 26 week gestation 2004e06; 1,2,3 year 2004e09

155 At 4 year 193 At 5 year

Mean prenatal BPA

Study/Cohort

Design

Spanier et al. (2012) HOMEa Study Cincinnati, OH, USA

Spanier et al. (2014) HOME Study Cincinnati, OH, USA

Slope or Rate Ratio (95% CI) AORg ¼ 2.3 (1.3, 4.1) AOR ¼ 1.2 (1.0, 1.5) NS

FEV1 at 4 year, per 10-fold BPA

b ¼ 14 (24, 4)

FEV1 at 5 year, per 10-fold BPA

NS

Child BPA at 4 and 5 year FEV1 at 4 and 5 year, per 10-fold BPA Donohue et al. (2013) CCCEHb New York City

Maternal-child pairs (prospectivelongitudinal)

34 week gestation 1998e2006 3e7 year 2001e10

368e429 at 5 e7 year 474 at 5e7 year

NS

Mean 3e7 year BPA Wheeze, per log10 BPA at 5 year

AOR ¼ 1.5 (1.1, 2.0)

at 6 year

AOR ¼ 1.4 (1.0, 1.9)

at 7 year

AOR ¼ 1.4 (1.0, 2.0)

Asthma, per log10 BPA

AOR ¼ 1.6 (1.2, 2.1)

prenatal BPA Wheeze, by continuous BPA variable

Kim et al. (2014) Korean elementary school

Gascon et al. (2015) INMA-Sabadellc Spain

Longitudinal

Maternal-child pairs (prospectivelongitudinal)

7e8 year

12, 32 weeks gestation 2004e06

127 7e12 year

437-445 at 6 mo 385 at 4 year 361 at 7 year

at 5 year

AOR ¼ 0.7 (0.5, 0.9)

at 6,7 year

NS

Asthma

NS

Wheeze, per log10 increase of BPA

AOR ¼ 2.5 (1.15,5.3)

Asthma, per log10 increase of BPA

AOR ¼ 2.1 (1.5, 3.0)

Girls

AOR ¼ 2.4 (2.2, 2.8)

Mean prenatal BPA

Wheeze, per 2-fold BPA

RRh ¼ 1.2 (1.03, 1.4)

Chest infection, per 2-fold BPA

RR ¼ 1.15 (1.00, 1.3)

Bronchitis, per 2-fold BPA

RR ¼ 1.18 (1.01, 1.4)

Asthma (tested only at 7 year), per 2-fold BPA

RR ¼ 1.2 (0.95, 1.6) Continued

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

446 TABLE 25.5

25. BPA BIOMARKERS

Association of Urinary Bisphenol A (BPA) With Human Respiratory Outcomesdcont’d

Study/Cohort

Design

Vernet et al. (2017) EDEN,d France

Maternal-child pairs (prospectivelongitudinal)

Buckley et al. (2018) MSCEHSe

Maternal-child pairs (prospectivelongitudinal)

Sampling Timeline

N/Age

Test/Effect

Slope or Rate Ratio (95% CI)

23e29 week gestation 2003e06

587

Wheeze, Bronchiitis, FEV1f

NS

Asthma, per log10 BPA

HRi ¼ 1.2 (0.97, 1.6)

25e40 week gestation 1998e2002

159 6e7 year

Asthma, per standard deviation of natural log BPA Boys

AOR ¼ 3.0 (1.4, 6.6)

Girls

NS

NS, not statistically significant. a Health Outcomes and Measures of the Environment. b Columbia Center for Children’s Environmental Health. c Infancia y Medio Ambiente. d Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant. e Mount Sinai Children’s Environmental Health Study. f Spirometry data for forced expiratory volume in 1 s. g Adjusted Odds Ratio. h Rate Ratio. i Hazard Ratio.

10-fold increase in prenatal BPA was associated with more externalizing behaviors (see below) in 8-year-old girls (b ¼ 6.2, 95% CI: 0.8, 11.6) on testing with the BASC-2, but not among boys. In contrast, externalizing behaviors in boys was associated with urinary BPA level at age 8 (b ¼ 3.9, 95% CI: 0.6, 7.2), but not in girls. Stacy et al. (2017) examined the patterns, variability, and predictors of urinary BPA concentrations in 337 mothers and children from the HOME Study. From 2003 to 2014 six urine samples were collected from children between 1 and 5 and at 8 years of age. Urinary BPA concentrations had a low degree of reproducibility (ICC < 0.2). Estimated daily intakes (EDIs) decreased with age. BPA concentrations were linked to consuming food stored or heated in plastic, consuming canned food and beverages, and handling cash register receipts. EDIs decreased as child age increased, with median intakes of 190 and 39 ng/kg/day for 1- and 8-year-olds, respectively. Romano et al. (2015) observed that BPA in the 26th gestational week was associated with a 43% decrease of thyroid stimulating hormone (TSH) in the cord blood of female, but not male, neonates. BPA in the 16th gestational week was not associated with neonatal TSH. There was no effect on thyroxine (T4), but there was a marginal statistically significant association with triiodothyronine (T3) in girls. Chemical covariates unique to this study’s analysis included iodine intake, polychlorinated biphenyls, and hexachlorobenzene. The INMA study (Infancia y Medio Ambiente; Childhood and Environment) is a population-based birth cohort study that recruited 657 pregnant women in the Spanish region of Sabadell between 2004 and 2006 (Guxens et al., 2012). Pregnant women were

recruited at their first routine prenatal care visit. Maternal urine samples were collected at 12  1.7 and 32  1.4 weeks of gestation. Total BPA was determined in 470 motherechild pairs. Data available for multivariate analysis included maternal age, socioeconomics, weight and height, parity, marital status, dietary information, use of household cleaning products, tobacco use, and season of birth, as well as first trimester blood mercury, total polychlorobiphenyls, and the DDT metabolite, DDE. For the 462 children included in Gascon et al. (2015), reported below, the median maternal BPA was 2.4e2.5 mg/g and the interquartile level was 1.7e3.7 mg/g. The ICC for the two maternal samples was 0.15 for unadjusted BPA and 0.14 for adjusted BPA (Casas et al., 2016), indicating low reproducibility. The GM for the 37 pregnant mothers <25 years of age was 3.3 mg/ g, whereas for the 83 pregnant mothers 35 years of age the GM was 2.2 mg/g. Respiratory parameters in the children of the INMASabadell cohort were studied by Gascon et al. (2015). Children were tested at 6 months (N ¼ 437e445), 14 months (N ¼ 424), 4 years (N ¼ 385), and 7 years (N ¼ 361). For each doubling in concentration of mean maternal urinary BPA the adjusted relative risks (RRs) over all ages combined increased for wheeze (RR, 1.20; 95% CI, 1.03e1.40; P ¼ .02), chest infections (RR, 1.15; 95% CI, 1.00e1.32; P ¼ .05), and bronchitis (RR, 1.18; 95% CI, 1.01e1.37; P ¼ .04). Asthma, tested only at age 7, showed an association but not with statistical significance (RR, 1.21 (0.94e1.57; P ¼ 0.14). These were slightly lower in a model that adjusted for other pollutants. The associations with early and late gestation BPA have shown different degrees of effect.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

Casas et al. (2016) estimated growth curves for femur length, head circumference, abdominal circumference, and biparietal diameter and estimated fetal weight during pregnancy (weeks 12e20 and 20e34), and for birth weight, birth length, head circumference at birth, and placental weight in 470 births. The median maternal BPA level was 2.3 mg/g. This study, one of the first to combine repeat exposure biomarker measurements and multiple growth measures during pregnancy, found little statistically significant evidence of an effect on fetal growth. However, the trend for BPA was for lower birth weight (21.6 g per mg/g BPA for girls and 11.0 g per mg/g for boys). Notably, the high intraindividual variability of the measurements meant likely exposure misclassification, probably random, thereby reducing the degree of observable linkage. At age 4 (Valvi et al., 2013), maternal BPA was associated with increased waist circumference (b per log 10 mg/g ¼ 0.28, 95% CI, 0.01, 0.57) and, with marginal statistical significance, BMI (b ¼ 0.28, 95% CI, 0.06, 0.63). Neurobehavioral testing (Casas et al., 2015) revealed that (1) psychomotor scores at age 1 were reduced in the highest tertile of creatinine-adjusted prenatal urinary BPA, but not at age 4, and (2) for each log10 mg/g of prenatal exposure there was increased incidence of hyperactivity, as reported by teachers using the Diagnostic and Statistical Manual of Mental Disorders-IV tool for Attention-Deficit/Hyperactivity Disorder (ADHD), when the children were 4 years old. The adjusted incidence rate ratio (IRR) for hyperactivity was 1.72 (95% CI: 1.08, 2.73) and was stronger in boys, 1.9 (95% CI; 1.01, 3.7), than in girls, 1.6 (95% CI: 0.79, 3.2). The IRR for inattention was elevated in boys (IRR ¼ 1.4) but was not statistically significant. However, the IRR for second tertile versus the first tertile showed a statistically significant elevation, 1.6 (95% CI: 1.01, 2.4). When the children were tested again at the age of 7, there was no association of prenatal BPA with hyperactivity, as measured by parents with the Conner’s Parent Rating Scales, nor were there links with externalizing and internalizing problems (Strengths and Difficulties Questionnaire). There were no significant associations with cognitive scores or their subscales. However, it must be noted that, ADHD is a complex disease and still not well understood, so there may be other important environmental chemicals (and other confounders) that were not included in the analysis. The relationships between early and late pregnancy samples and neurobehavioral testing were not analyzed separately. Perera et al. (2012) examined the association between prenatal BPA exposure and child behavior, adjusting for postnatal BPA exposure and hypothesizing genderspecific effects. Participants in this study were mothers

447

and their children in the Columbia Center for Children’s Environmental Health (CCCEH) low income cohort, predominantly African-American and Dominican women, in New York City. Enrollment in 1998 was limited to women who were in the age range of 18e 35 years, nonusers of tobacco products or illicit drugs, free of diabetes, hypertension, or known HIV, and who initiated prenatal care by the 20th week of pregnancy. Urine samples were collected at the 34th week of gestation on average and from children between 3 and 4 years of age. Out of 337 motherechild pairs with prenatal BPA measurements and maternal prenatal questionnaire data, BPA was detectable in the urine of >90% of both mothers and children. The ranges of total SG-adjusted BPA in maternal and child urine samples were 0.24e38.53 mg/L and 0.42e73.50 mg/L, respectively, indicating a wide variation in exposure. The GMs for maternal and child urinary concentrations of BPA were 1.96 and 3.94 mg/L, respectively. No significant differences were observed between boys and girls in median and mean prenatal or postnatal BPA concentrations, whether SG-adjusted or not. The authors assessed behavior of children between 3 and 5 years of age using the Child Behavior Checklist (CBCL) in 198 of these motherechild pairs (87 boys, 111 girls). Among boys, high prenatal BPA exposure (highest quartile vs. the three lower quartiles) was associated with significantly higher CBCL scores (more problems) on Emotionally Reactive (1.62 times greater; 95% CI: 1.13, 2.32) and Aggressive Behavior scales (1.29 times greater; 95% CI: 1.09, 1.53). Among girls, higher exposure was associated with lower scores on all syndromes, reaching statistical significance for Anxious/Depressed (0.75 times as high; 95% CI: 0.57, 0.99) and Aggressive Behavior (0.82 times as high; 95% CI: 0.70, 0.97) scales. These results suggest that prenatal exposure to BPA may affect child behavior, and differently among boys and girls. Among boys they found significant positive associations between prenatal BPA and CBCL scores of Emotionally Reactive and Aggressive Behavior. In contrast, among girls prenatal BPA was associated with significantly lower scores for the Aggressive Behavior and Anxious/Depressed syndromes. The authors noted that these findings are inconsistent with reports by Braun et al. (2009, 2011b), discussed above, who reported evidence of adverse effects predominantly in girls. The different ethnicity and socioeconomic status levels of the two sets of subjects provide a somewhat different neurobehavioral developmental setting that might contribute to the inconsistency. Among the first studies of the fetal effect of BPA on asthma published on maternaleinfant/child pairs, Donohue et al. (2013) looked at asthma in the CCCEH cohort. Sampling for urinary BPA was conducted during

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

448

25. BPA BIOMARKERS

the third gestational trimester and in their children at ages 3, 5, and 7 years old. There was no correlation of BPA levels between gestational and child samples (r  0.02) nor between samples taken at ages 3 and 5, but between ages 3 and 5 or 7 the r-statistic, 0.14e0.16, was significant. Wheeze was assessed with questionnaires at 5, 6, and 7 years of age, whereas an asthma assessment was conducted by a physician once between ages 5 and 12. The number of subjects with complete data for analysis ranged from 270 to 390. BPA levels at 3, 5, and 7 years were each associated with asthma, and the adjusted OR for mean child BPA was 1.6 (95% CI: 1.2, 2.1). The adjusted ORs were similar or lower for wheeze. Notably, third trimester maternal BPA was inversely associated with wheeze (AOR ¼ 0.7, 95% CI: 0.5, 0.9). The authors discussed a theory based on the pharmacokinetics of BPA in the pregnant mouse and measurements in human placenta in other studies. They noted that BPA was retained in the fetoplacental unit, which would limit the observable amount in the urine. If some pregnant women and fetuses displayed similar pharmacokinetics, it raises the possibility of significant misclassification of exposure, especially in the third trimester. This would be consistent with the finding above that 16th gestational week samples were more associated with childhood respiratory outcomes than 26th week samples (Spanier et al., 2012). In the multicenter Study for Future Families II, initiated during 2002e05, maternal urinary samples were collected during a visit sometime in the 10e39 weeks (mean 27 weeks) of gestation timeframe (Evans et al., 2014). Maternal median BPA was 1.6 mg/g and mean BPA was 3.7 mg/g. Externalizing and internalizing behaviors measured with the CBCL in boys at aged 6e 10 years was associated with maternal BPA among motherechild pairs in which the BPA was detectable (28 out of 153 pairs were excluded). The increases were small, but statistically significant, b ¼ 0.35 (P ¼ .05) and b ¼ 0.35 (P ¼ .02), respectively. Girls exhibited no associations with these measures. Nested in the Generation R cohort, Snijder et al. (2013) analyzed a subset of 80 women for whom there was urinary BPA data from each trimester during pregnancy visits. The fetal growth rate was reduced in women with >4.2 mg/g BPA compared with women whose BPA was <1.54 mg/g. Weight at birth was reduced by 683 g and head circumference was reduced by 3.9 cm (See above for the analysis of BPA levels in this subset by Jusko et al. (2014)). Maternalechild pairs in an agricultural area of California were the focus of the Center for the Health Assessment of Mothers and Children of Salinas study. Gestational urinary samples were taken at approximately 12 and 26 weeks during 1999e2000. The GM of creatinine-adjusted BPA was 1.1 mg/L and the two

samples were only weakly correlated (r ¼ 0.25). Maternal BPA, particularly the 26-week sample, was associated with lower TSH in neonatal boys (9.9% per log2 unit increase of BPA), but not in girls (Chevrier et al., 2013). BPA at 26 weeks but not 12 weeks was also associated with lower total maternal thyroxine (b ¼ 0.13 mg/dL per log2 unit) measured at 26 weeks. Iodine level was not a confounder. BASC-2 internalizing behaviors tended to be increased with higher maternal BPA in 7-year-old boys but not girls in both mothers’ and teachers’ reports, though the score differences were not statistically significant (Harley et al., 2013). Early and late pregnancy samples were not examined separately. BPA was also measured in 5-year-olds (GM ¼ 2.5 mg/L) and was associated with outcomes, primarily among girls (Harley et al., 2013). Analysis of reports on girls completed by mothers linked child BPA to several externalizing behaviors (score difference of 1.2, 95% CI: 0.3, 2.1) and two of its scales, including conduct problems (score difference of 1.8, 95% CI: 0.8, 2.9) and inattention (score difference of 0.9, 95% CI: 0.2, 1.6). Using a different tool, the Conners’ ADHD/Diagnostic and Statistical Manual for Mental Disorders-IV, data generated by the mothers uncovered associations with inattention (score difference of 1.3, 95% CI: 0.4, 2.2), hyperactivity (score difference of 1.1, 95% CI: 0.1, 2.0), and ADHD (score difference of 1.3, 95% CI: 0.3, 2.3). Analysis of data from teacher reports also provided evidence of statistically significant associations among both boys and girls of BASC-2 internalizing behaviors (boys score difference of 1.8, 95% CI: 0.14, 3.1; girls score difference of 1.8, 95% CI: 0.1, 3.6) and its scales, especially anxiety and depression, but not externalizing behaviors. CADS components scored by teachers tended to be associated with girls. Inattention, hyperactivity, and ADHD score differences were 1.7, 0.4, and 1.1, respectively for boys and 1.0, 1.7, and 1.7 for girls. The EDEN (Etude des De´terminants pre´ et post natals du de´veloppement et de la sante´ de l’Enfant) cohort examined mothereinfant/child pairs from Poitiers and Nancy, France. Maternal urinary BPA sampled between gestational weeks 22 and 29 (N ¼ 520) had 2.4 mg/L creatinine-adjusted BPA (Philippat et al., 2014). There was no association of urinary BPA with birth weight, but there was increased head circumference (Philippat et al., 2012). Children tended to have heavier weight at 12, 24 and 36 months but not with statistical significance (Philippat et al., 2014). This was similar to findings by Valvi et al. (2013) in the INMA-Sabadell cohort. Follow-up (Philippat et al., 2017) found only a small effect due to urinary BPA from gestational weeks 23e29 on the internalizing behavior score at 3 years of age (IRR ¼ 1.06, 95% CI: 1.00, 1.12, per doubling in BPA concentration, N ¼ 457), especially for peer

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

PREGNANT WOMEN, MOTHEReINFANT/CHILD PAIRS, INFANTS, CHILDREN

relationship problems, and on the externalizing behavior score, especially in the hyperactivitye inattention subscale at 5e6 years of age (IRR ¼ 1.08, 95% CI: 1.01, 1.14, per doubling in BPA concentration). Dichotomizing the score data resulted in an OR for internalizing behavior of 1.2 with marginal statistical significance (95% CI: 0.96, 1.6) and an OR of 1.4 (95% CI: 1.08, 1.8) for hyperactivityeinattention. The data were provided by mothers (N ¼ 464) who completed the Strength and Difficulties Questionnaire. Covariates included child age, maternal adiposity, parental education, breastfeeding duration, smoking, and maternal mental status. An IRR of 1.08 (95% CI: 1.01, 1.14) was reported. In addition, IQ was assessed in 5e6-year-old boys using the Wechsler Preschool and Primary Scale of Intelligence (Nakiwala et al., 2018). No association was observed. Boys born to a subgroup of 587 women from the EDEN cohort in France were also examined at age 5 for respiratory health (Vernet et al., 2017). Comparison of FEV1 with log-transformed urinary BPA revealed a nonstatistically significant inverse relationship with FEV1 and a positive association with asthma (Hazard ratio ¼ 1.2, 95% CI: 0.97, 1.55; third tertile HR ¼ 1.4, 95% CI: 0.87, 2.2). There was no association with wheeze. Preterm birth (<37 weeks) was studied by Cantonwine et al. (2015) in a study nested in a cohort enrolled during 2006e08 in Boston and Philadelphia. Urine samples were obtained over four visits (at 10th, 18th, 26th, and 35th weeks of gestation) from 1695 pregnant women. SG-corrected BPA indicated low stability across trimesters (ICC ¼ 0.21; 95% CI: 0.16, 0.27), and ICCs were slightly higher in cases of preterm birth (0.25) compared with controls (0.19). Spearman correlations between study visits for BPA were low, 0.17e0.26 (all P-values < .01). The trend to preterm births with increasing gestational BPA was mostly not statistically significant, but notable, nonetheless, because the BPA from the fourth visit (33e38 weeks of gestation) was associated (P < .01) in all three statistical models with spontaneous preterm birth (N ¼ 25; 298 controls). The AOR in the model with the most adjusting covariates, including total urinary phthalates, was 2.2 (95% CI: 1.3, 4.0). Neonatal TSH was lower and thyroxine was increased with increased BPA, 8.2% and 4.8%, respectively, per natural log of the interquartile concentration (Aung et al., 2017). The association was primarily due to the gestational weeks of 26 and 35 samples, which are 13.5% and 17.3%. However, the conclusions are limited because this cohort was enriched with preterm births (116 preterm and 323 term neonates). The authors noted a general consistency between BPA and TSH in studies of men, nonpregnant women, and children. Recently, Buckley et al. (2018) reported on the association of log-transformed urinary BPA in the third

449

gestational trimester with previously diagnosed asthma in the respective 6e7-year-old boys (AOR ¼ 3.0, 95% CI: 1.4, 6.6), but not girls, in the Mount Sinai Children’s Environmental Health Study of 164 maternalechild pairs. The median unadjusted BPA concentration in the third trimester was 1.3 mg/L and the interquartile range was 0.6e2.3 mg/L. A small blood sampling study of 80 maternaleinfant pairs at the University of Michigan Hospital (VeigaLopez et al., 2015) found that birth weight of a female pregnancy was 183 g (P > .005) lower per twofold increase in plasma uBPA and 607 g (P ¼ .0093) lower per 10-fold increase in uBPA, based on first trimester samples. The term uBPA had an opposite effect, a gain of 96 g (P < .05) per twofold increase of uBPA and 318 g (P ¼ .034) per 10-fold increase, as well as an increased gestational age for female births, 1.1 days (P ¼ .06) and 3.7 days (P ¼ .06), respectively. There was no effect on male births. Notably, term uBPA was approximately twice as high as in the first trimester and was higher in 68% of term mothers. This may prove to be an example of a U-shaped doseeresponse curve. In addition, it is not clear from the literature whether the other studies analyzing birth weight and urinary BPA examined the different gestational weeks separately. If there was not a statistically significant difference, then, it may be that uBPA in blood is a more enlightening approach.

Children The association between concurrently measured BPA and ADHD symptoms was examined in 460 8e15-yearold children, using data from the 2003e04 NHANES (Tewar et al., 2016). The prevalence of ADHD in the group was 7.1%. Among children with urinary BPA above the median, the prevalence was 11.2%, in contrast with 2.9% below the median. The AOR was 5.68 (95% CI: 1.6, 20), adjusted for child’s age, family income, gender, race/ethnicity, urine creatinine, prenatal tobacco exposure, blood lead level (log-transformed), urine organophosphate metabolite level (log-transformed), and insurance status. For boys the AOR was 11 (95% CI: 1.4, 86), whereas in girls the AOR was 2.8 (95% CI: 0.4, 21). Recently, the results of a case-control study of a group of 465 6e12-year-old children in Guangzhou, China showed that concurrently measured creatinineadjusted urinary BPA was associated with ADHD in a concentration-dependent manner (Li et al., 2018). Study enrollment was composed of 215 children with ADHD and 250 controls. Comparing the second, third, and fourth quartiles to the first (referent) quartile of BPA, the AORs were, respectively, 1.8 (95% CI: 0.95, 3.4), 7.4 (95% CI: 3.9, 14), and 9.4 (95% CI: 4.9, 18). The effect

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

450

25. BPA BIOMARKERS

was stronger in boys than girls, AOR of 1.8, 9.1, and 10.1, versus 0.96, 3.35, and 4.6, respectively, but only 27 of the 215 cases were girls. For cases the GM of creatinineadjusted BPA was 4.63 mg/g versus 1.71 mg/g for controls. Like other studies (see above) this difference was larger in 6e9-year-old children, among whom the creatinine-adjusted BPA GM was 5.15 mg/g in cases versus 1.74 mg/g in controls. Consistent with these findings was the greater use of plastic food and beverage containers by ADHD children, but one cannot easily say whether higher exposure to BPA preceded the ADHD diagnosis because of the study design. In a respiratory disease study, Kim et al. (2014) tested 127 children every 2 years at an elementary school in Seoul, South Korea, starting with urinary BPA measurement at age 7e8 and wheeze and asthma testing every 2 years, ending at age 11e12. Children with diagnosed asthma were excluded. The GM of BPA was 1.0 mg/L. A one-unit increase in log-transformed creatinineadjusted BPA was associated with wheeze (AOR ¼ 2.5, 95% CI: 1.15, 5.3) and asthma (HR ¼ 2.1, 95% CI: 1.5, 3.0), but the association with asthma was primarily in girls (HR ¼ 2.4, 95% CI: 2.2, 2.8). Covariates for analysis included parental asthma history, parental education level, tobacco use, pet ownership, and cockroach sensitization.

FOOD PACKAGING AND BISPHENOL A ALTERNATIVES Volkel et al. (2011) determined both free and total BPA in urine samples of 1e2-month-old infants collected via urine bags. The infants were not exposed to chemicals via medical devices. Data were collected on infants after use of BPA-containing BPA-bottles in contrast to infants without use of PC-bottles. Free BPA was observed above the limit of quantitation (LOQ) in only 3 of 91 (3%) samples from 47 infants. Total BPA was observed in only 38 (42%) urine samples, at concentrations up to 18 mg/L. The highest concentration was just under the current EFSA guidance. Infants who were fed using baby bottles showed approximately twofold higher median levels of total BPA. The data also indicate substantial conjugation of BPA in infants. It is interesting to note that BPA (and phthalates) exposures were substantially reduced when individuals’ diets were restricted to food with limited packaging. Rudel et al. (2011) evaluated the contribution of food packaging to exposure, and measured urinary BPA and phthalate metabolites before, during, and after a “fresh foods” dietary intervention. Twenty participants in five families were selected based on self-reported use of canned and packaged foods. Participants ate their usual diet, followed by 3 days of “fresh foods” that were

not canned or packaged in plastic, and then returned to their usual diet. Evening urine samples were collected over 8 days in January 2010 and were composited into preintervention, during intervention, and postintervention samples. Results showed that urine levels of BPA metabolites decreased significantly during the fresh foods intervention (e.g., BPA GM, 3.7 ng/mL preintervention vs. 1.2 ng/mL during intervention). The intervention reduced GM concentrations of BPA by 66% with the maxima reduced by 76%. Morgan et al. (2011) quantified urinary total BPA in 81 children 23e64 months of age in Ohio over 48-h periods to quantify the relationship with overall exposure. Estimated median intake doses of BPA for these 81 children were 109 ng/kg/day (dietary ingestion), 0.06 ng/kg/ day (nondietary ingestion), and 0.27 ng/kg/day (inhalation). The estimated median excreted amount of urinary BPA was 114 ng/kg/day, which closely matched exposure. Consuming canned vegetables at least once a day was associated in the HOME study (Braun et al., 2012) with higher BPA concentrations (GM ¼ 2.3 mg/g) compared with those consuming no canned vegetables (GM ¼ 1.6 mg/g). BPA concentrations did not vary by consumption of fresh fruits and vegetables, canned fruit, or fresh and frozen fish. In the Spanish INMA-Sabadell cohort investigators (Casas et al., 2013) estimated that 21% e25% of the urinary BPA in the pregnant women was associated with consumption of canned fish (Casas et al., 2013). Findings of BPA alternatives that have gradually replaced BPA have also been reported in urine, some data of which were included in studies described above. The substitution of BPA includes alternative BPXs such as bisphenol S (BPS; 4,4-sulfonyldiphenol), bisphenol B (2,2-bis[4-hydroxyphenyl]butane), BPF (4,4-dihydroxydiphenylmethane), and bisphenol AF (4,4-[hexa-fluoroisopropylidene] diphenol) (Usman and Ahmad, 2016). BPA-related compounds or BPXs consist of two phenol groups attached through a bridging carbon or other chemical structure. The parahydroxy groups are critical in binding to estrogen receptor. Because BPXs are structurally similar to BPA, it is expected that they may also have the same toxicological effects on the biological system. BPF and BPS are selected here as examples to examine in brief some of the findings related to these alternatives. BPF is absorbed by oral route and distributed to the whole organism, including the reproductive tract and the fetus by crossing the placental barrier, is mainly excreted through the urine, and has been shown to be as hormonally active as BPA. BPF has a broad range of industrial applications including manufacture of epoxy resins and polycarbonates (Usman and Ahmad, 2016). BPF residues have been found in

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

CONCLUDING REMARKS AND FUTURE DIRECTIONS

foodstuffs packaged in containers with epoxy coatings, in the drinking water pumped out from the water pipes incidentally using bisphenol F diglycidyl etherebased epoxy resins for renovation; in vegetables, fish and seafood, meat and meat products, and beverages; and in indoor dust, and personal care products (PCPs). BPF was detected in 98% of the urine samples (LOQ of 0.03 mg/ L) collected in the Swedish POPUP study during 2009e2014 with a median SG-adjusted concentration of 0.32 mg/L and with levels increasing between 2009 and 2014 (Gyllenhammar et al., 2017). As an environmental contaminant, BPF has been detected in environmental media such as surface water, sewage water, sediment samples, sewage sludge, liquid manure samples, compost water samples, and municipal landfill leachates. BPS has hormonal potencies of the same magnitude as BPA. BPS use was increased in the production of epoxy resins, thermal papers, and infant feeding bottles after restrictions were put on BPA (Usman and Ahmad, 2016). It is more heat resistant and photoresistant than BPA. Studies showed that BPS has been detected in PCPs, foodstuffs (beverages, dairy products, fish and seafood, cereals, meat and meat products, and canned fruits and vegetables), indoor dust, river water, sewage, sediment, and sludge. The authors noted that moderate to high concentrations of BPS in the range of a few nanogram per gram to several milligrams per gram were detected in thermal receipts collected from various cities of United States, Korea, Vietnam, and Japan. The EDI through dermal absorption was 0.00418 mg/kg bw/ day for the general population and 0.312 mg/kg bw/ day for individuals who are occupationally exposed. BPS has a greater half-life and better dermal penetration than BPA and can lead to higher body burden in comparison to BPA. It is nondegradable in the aerobic conditions and likely to accumulate in the aquatic environment. Studies cited reported that (1) the detection rate of BPS in human matrices has been as high as 81% in urine and 3% in breast milk collected from United States and seven Asian countries; and (2) a mean EDI of 1.7 mg/day in Japan followed by China and the United States, 0.34 mg/day and 0.32 mg/day, respectively. Gyllenhammar et al. (2017) found BPS 68% of urine samples (Swedish POPUP study, see above) at an SG-adjusted median 0.048 mg/L.

CONCLUDING REMARKS AND FUTURE DIRECTIONS BPA has been measured in human urine samples in various biomonitoring programs and research studies worldwide. An integrated approach that uses all data types along the environmental disease continuum is

451

required for a complete understanding of the findings. Biomarkers may be particularly useful when they provide linkage to important exposure but must be measured in the correct matrix for exposure route/ source of interest, and the analytical technology must be available, reliable, and reproducible, among other considerations. Nondetection may mean that the technology is limited in measuring low concentrations of specific chemicals, or that the exposure occurred at an earlier point in time, allowing for the chemical to be eliminated from the person’s body before measurement took place. Although biomonitoring provides reference ranges, for most environmental chemicals there are no “standard ranges” or “safe ranges” established for biomarkers. In using data on human exposure to environmental chemicals for performing risk assessment of such exposure, the information needed include an understanding of the pattern of exposure, toxicology and epidemiology databases, estimates of intake, measurements of exposure, use of biomarker data, and interpretation of the data and parameters to evaluate the associated public health implications and environmental management and regulatory decision-making. Therefore, for biomarkers to be useful for environmental (and occupational) health risk assessments, they have to be relevant and valid (WHO, 2001). A good biomarker of exposure should be useful to predict adverse effects, rather than exposure levels. In addition, biomarkers must be validated before application in the risk assessment process, i.e., the relationship between the biomarker, the exposure, and the health outcome must be established. The general criteria for validating biomarkers include understanding the natural history, biological and temporal relevance, pharmacokinetics, background variability, dose response, and confounding factors (WHO, 2001). The validation process includes the critical assessment of different relationships: exposureedose, dose response (effect), and effectedisease. Validation can focus on the demonstration of a correspondence between a biomarker of exposure and external exposure, or the assessment of their relationship with the concentration in the critical organ (e.g., concentration in the kidney vs. in blood or urine) or with critical effects (e.g., lead neurotoxicity vs. blood lead concentration). For BPA, health reference values have been established based on animal data, but in the meantime, the results of a number of laboratory animal studies has not been sufficiently consistent. There are still uncertainties particularly on two aspectsdlow dose effects and NMDRC. BPA has been measured as uBPA, conjugated BPA, and total BPA. As the conjugated forms are currently viewed to be the inactivated forms without endocrine activities, knowing the forms of BPA and the associated

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

452

25. BPA BIOMARKERS

respective amounts present systemically in humans would be important for understanding the health implications of BPA in the body. Blood samples are a typical and valid approach to estimating systemic contaminant levels and uBPA is detectable in serum samples (Vandenberg et al., 2014a; vom Saal and Welshons, 2014), but it is not as practical as urine sampling. A high degree of within-person variability has also been reported (Braun et al., 2011a; Jusko et al., 2014; Stacy et al., 2017). Lakind and Naiman (2015) noted the difficulties in interpreting urinary BPA data, despite efforts to account for urine dilution and translate spot sample data to daily exposure. In addition, the BPA levels measured in urine can vary by factors such as age, gender, and race/ethnicity. A small but provocative study of blood plasma in mothereinfant pairs (Veiga-Lopez et al., 2015) observed that gestational term uBPA was approximately twice as high as in the first trimester and was higher in 68% of term mothers. The results, if found to be accurate when repeated, may explain inconsistent findings within and between studies and suggest that the way forward in epidemiology of BPA should include blood sampling to better address different development time frames. The implications of measurements of BPA concentrations in human tissues and their correlations to a dosee response relationship have yet to be clearly established. Likely, there are sensitive subsets of individuals and critical windows of effect during development, and the goal must be delineation of the mechanisms behind those subsets and time frames. Possibilities of mechanism include enzymatic and cellular receptor polymorphisms and epigenetic causes. Notably, behavior, cognitive ability, IQ, and ADHD are complex phenomena and still not well understood, so there may be other important environmental chemicals and other confounders that were not included. Other known critical pollutants also need to be included in the analysis, such as blood lead in the neurodevelopmental studies. However, the epidemiological studies point to a concern about neurodevelopmental and respiratory effects from fetal and childhood exposures.

References Arbuckle, T.E., Davis, K., Marro, L., et al., 2014. Phthalate and bisphenol A exposure among pregnant women in Canada–results from the MIREC study. Environ. Int. 68, 55e65. Arbuckle, T.E., Marro, L., Davis, K., et al., 2015. Exposure to free and conjugated forms of bisphenol A and triclosan among pregnant women in the MIREC cohort. Environ. Health Persp. 123, 277e284. Aung, M.T., Johns, L.E., Ferguson, K.K., et al., 2017. Thyroid hormone parameters during pregnancy in relation to urinary bisphenol A concentrations: a repeated measures study. Environ. Int. 104, 33e40.

Berman, T., Goldsmith, R., Go¨en, T., et al., 2014. Demographic and dietary predictors of urinary bisphenol A concentrations in adults in Israel. Int. J. Hyg Environ. Health 217 (6), 638e644. Braun, J.M., Kalkbrenner, A.E., Calafat, A.M., et al., 2011a. Variability and predictors of urinary bisphenol A concentrations during pregnancy. Environ. Health Persp. 119, 131e137. Braun, J.M., Kalkbrenner, A.E., Calafat, A.M., et al., 2011b. Impact of early-life bisphenol A exposure on behavior and executive function in children. Pediatrics 128 (5), 873e882. Braun, J.M., Smith, K.W., Williams, P.L., et al., 2012. Variability of urinary phthalate metabolite and bisphenol A concentrations before and during pregnancy. Environ. Health Persp. 120, 739e745. Braun, J.M., Yolton, K., Dietrich, K.N., et al., 2009. Prenatal bisphenol A exposure and early childhood behavior. Environ. Health Persp. 117, 1945e1952. Buckley, J.P., Quirόs-Alcala´, L., Teitelbaum, S.L., et al., 2018. Associations of prenatal environmental phenol and phthalate biomarkers with respiratory and allergic diseases among children aged 6 and 7 years. Environ. Int. 115, 79e88. Calafat, A.M., Kuklenyik, Z., Reidy, J.A., et al., 2005. Urinary concentrations of bisphenol A and 4-nonylphenol in a human reference population. Environ. Health Persp. 113, 391e395. Calafat, A.M., Longnecker, M.P., Koch, H.M., et al., 2015. Optimal exposure biomarkers for nonpersistent chemicals in environmental epidemiology. Environ. Health Persp. 123 (7), A166eA168. Calafat, A.M., Longnecker, M.P., Koch, H.M., et al., 2016. Response to “Comment on optimal exposure biomarkers for nonpersistent chemicals in environmental epidemiology”. Environ. Health Persp. 124, A66eA67. Calafat, A.M., Ye, X., Wong, L.-Y., et al., 2008. Exposure of the U.S. population to bisphenol A and 4-tertiary-octylphenol: 2003e2004. Environ. Health Persp. 116, 39e44. Cantonwine, D.E., Ferguson, K.K., Mukherjee, B., et al., 2015. Urinary bisphenol A levels during pregnancy and risk of preterm birth. Environ. Health Persp. 123, 895e901. Casas, M., Forns, J., Martı´nez, D., et al., 2015. Exposure to bisphenol A during pregnancy and child neuropsychological development in the INMA-Sabadell cohort. Environ. Res. 142, 671e679. Casas, M., Valvi, D., Ballesteros-Gomez, A., et al., 2016. Exposure to bisphenol A and phthalates during pregnancy and ultrasound measures of fetal growth in the INMA-Sabadell cohort. Environ. Health Persp. 124, 521e528. Casas, M, Valvi, D., Luque, N., et al., 2013. Dietary and sociodemographic determinants of bisphenol A urine concentrations in pregnant women and children. Environ. Int. 56, 10e18. CDC, 2018a. Healthy People 2020. Chapter 12. Environmental Health. Centers for Disease Control and Prevention (CDC). https://www. cdc.gov/nchs/data/hpdata2020/HP2020MCR-C12-EH.pdf. CDC, 2018b. National Health and Nutrition Examination Survey: Estimation Procedures, 2011e2014. In: Data Evaluation and Methods Research. Vital and Health Statistics Series 2, Number 177. Centers for Disease Control and Prevention (CDC), National Center for Health Statistics, Hyattsville, Maryland. DHHS Publication No. 2018e137.7. Chevrier, J., Gunier, R.B., Bradman, A., et al., 2013. Maternal urinary bisphenol A during pregnancy and maternal and neonatal thyroid function in the CHAMACOS study. Environ. Health Persp. 121, 138e144. Covaci, A., Den Hond, E., Geens, T., et al., 2015. Urinary BPA measurements in children and mothers from six European member states: overall results and determinants of exposure. Environ. Res. 141, 77e85. Donohue, K.M., Miller, R.L., Perzanowski, M.S., et al., 2013. Prenatal and postnatal bisphenol A exposure and asthma development among inner-city children. J. Allergy Clin. Immunol. 131, 736e742.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

REFERENCES

EFSA, 2015. Scientific opinion on the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs: executive summary. EFSA panel on food contact materials, enzymes, flavourings and processing aids (CEF). European Food Safety Authority, Parma, Italy. EFSA J. 13 (1), 3978 (1040 pages). Evans, S.F., Kobrosli, R.W., Barrett, E.S., et al., 2014. Prenatal bisphenol A exposure and maternally reported behavior in boys and girls. Neurotoxicology 45, 91e99. Fan, A.M., Chou, W.C., Lin, P.P., 2017. Toxicology and risk assessment of bisphenol A. In: Gupta, R.C. (Ed.), Developmental and Reproductive Toxicology, second ed. Academic Press/Elsevier, Amsterdam, pp. 765e795. Fan, A.M., 2014. Biomarkers in toxicology, risk assessment and chemical regulations. In: Gupta, R.C. (Ed.), Biomarkers in Toxicology, first ed. Academic Press/Elsevier, Amsterdam, pp. 1057e1079. Gascon, M., Casas, M., Morale,s, E., et al., 2015. Prenatal exposure to bisphenol A and phthalates and childhood respiratory tract infections and allergy. J. Allergy Clin. Immunol. 135, 370e378. Gerona, R.R., Pan, J., Zota, A.R., et al., 2016. Direct measurement of bisphenol A (BPA), BPA glucuronide and BPA sulfate in a diverse and low-income population of pregnant women reveals high exposure, with potential implications for previous exposure estimates: a cross-sectional study. Environ. Health 15, 50. Ginsberg, G., Rice, D.C., 2009. Does rapid metabolism ensure negligible risk from bisphenol A? Environ. Health Persp. 117, 1639e1643. Guidry, V.T., Longnecker, M.P., Aase, H., et al., 2015. Measurement of total and free urinary phenol and paraben concentrations over the course of pregnancy: assessing reliability and contamination of specimens in the Norwegian mother and child cohort study. Environ. Health Persp. 123, 705e711. Guxens, M., Ballester, F., Espada, M., et al., 2012. Cohort profile: the INMAdINfancia y Medio Ambiente d (environment and childhood) project. Int. J. Epidemiol. 41, 930e940. Gyllenhammar, I., Glynn, A., Jo¨nsson, B.A.G., et al., 2017. Diverging temporal trends of human exposure to bisphenols and plastizisers, such as phthalates, caused by substitution of legacy EDCs? Environ. Res. 153, 48e54. Harley, K.G., Gunier, R.B., Kogut, K., et al., 2013. Prenatal and early childhood bisphenol A concentrations and behavior in schoolaged children. Environ. Res. 126, 43e50. Health Canada, 2017. Fourth Report on Human Biomonitoring of Environmental Chemicals in Canada. Results of the Canadian Health Measures Survey Cycle 4 (2014e2015). Jaddoe, V.W., Bakker, R., van Duijn, C.M., et al., 2007. The Generation R Study Biobank: a resource for epidemiological studies in children and their parents. Eur. J. Epidemiol. 22, 917e923. Jo¨nsson, B.A.G., Amon, A., Lindh, C.H., 2014. Tidstrender fo¨r och halter av perfluorerade alkylsyror (PFAAs) i serum samt ftalatmetaboliter och alkylfenoler I urin hos unga svenska ma¨n och kvinnor - resultat fra˚n den fja¨rde uppfo¨ljningensunderso¨kningen a˚r 2013. Avdelningen fo¨r Arbets- och miljo¨medicin. Lunds universitet, Lund. Cited by Calafat et al., 2005. Jusko, T.A., Shaw, P.A., Snijder, C.A., et al., 2014. Reproducibility of urinary bisphenol A concentrations measured during pregnancy in the Generation R Study. J. Expo. Sci. Environ. Epidemiol. 24 (5), 532e536. Kim, K.N., Kim, J.H., Kwon, H.J., et al., 2014. Bisphenol A exposure and asthma development in school-age children: a longitudinal study. PLoS One 9, e111383. Kooijman, M.N., Kruithof, C.J., van Duijn, C.M., et al., 2016. The Generation R Study: design and cohort update 2017. Eur. J. Epidemiol. 31, 1243e1246. Lakind, J.S., Naiman, D.Q., 2015. Temporal trends in bisphenol A exposure in the United States from 2003 to 2012 and factors associated with BPA exposure: spot samples and urine dilution complicate data interpretation. Environ. Res. 142, 84e95.

453

Lakind, J.S., Naiman, D.Q., 2011. Daily intake of bisphenol A and potential sources of exposure: 2005e2006 National Health and Nutrition examination survey. J. Expo. Sci. Environ. Epidemiol. 21 (3), 272e279. Larsson, K., Ljung Bjo¨rklund, K., Palm, B., et al., 2014. Exposure determinants of phthalates, parabens, bisphenol A and triclosan in Swedish mothers and their children. Environ. Int. 73, 323e333. Lee, B.E., Park, H., Hong, Y.C., et al., 2014. Prenatal bisphenol A and birth outcomes: MOCEH (mothers and Children’s environmental Health) study. Int. J. Hyg Environ. Health 217 (2e3), 328e334. Li, Y., Zhang, H., Kuang, H., et al., 2018. Relationship between bisphenol A exposure and attention-deficit/hyperactivity disorder: a casecontrol study for primary school children in Guangzhou, China. Environ. Pollut. 235, 141e149. Longnecker, M.P., Harbak, K., Kissling, G.E., 2013. Reports from the field. The concentration of bisphenol A in urine is affected by specimen collection, a preservative, and handling. Environ. Res. 126, 211e214. Magnus, P., Irgens, L.M., Haug, K., 2006. Cohort profile: the Norwegian mother and child cohort study (MoBa). Int. J. Epidemiol. 35, 1146e1150. Marty, M., 2015. Consideration of infants and children in risk assessment. In: Fan, A.M., Khan, E.M., Alexeeff, G.V. (Eds.), Toxicology and Risk Assessment. Pan Stanford Publishing Pte. Ltd, pp. 93e133. Morgan, M.K., Jones, P.A., Calafat, A.M., et al., 2011. Assessing the quantitative relationships between preschool children’s exposures to bisphenol A by route and urinary biomonitoring. Environ. Sci. Technol. 45, 5309e5316. Nakiwala, D., Pevre, H., Heude, B., et al., 2018. In-utero exposure to phenols and phthalates and the intelligence quotient of boys at 5 years. Environ. Health 17, 17. NTP, 2018. Draft NTP Research Report on the CLARITY-BPA Core Study: A Perinatal and Chronic Extended-dose-range Study of Bisphenol A in Rats. NTP RR 9. Research Triangle Park, N.C. National Toxicology Program. (9), pp. 1e249. Nelson, J.W., Scammell, M.K., Hatch, E.E., et al., 2012. Social disparities in exposures to bisphenol A and polyfluoroalkyl chemicals: a crosssectional study within NHANES 2003e2006. Environ. Health 11 (10). Art. No 10. Nepomnaschy, P.A., Baird, D.D., Weinberg, C.R., et al., 2009. Withinperson variability in urinary bisphenol A concentrations: measurements from specimens after long-term frozen storage. Environ. Res. 109, 734e737. Park, J.H., Hwang, M.S., Ko, A., et al., 2016. Risk assessment based on urinary bisphenol A levels in the general Korean population. Environ. Res. 150, 606e615. Parker, J.D., Aoki, Y., Ingram, D., 2018. Does Creatinine Adjustment Method Affect Estimated BPA Levels? (Powerpoint Presentation). https://www.cdc.gov/nchs/ppt/nchs2015/parker_wednesday_ brooksideab_dd5.pdf. Perera, F., Vishnevetsky, J., Herbstman, J.B., et al., 2012. Prenatal bisphenol A exposure and child behavior in an inner-city cohort. Environ. Health Persp. 120, 1190e1194. Philips, E.M., Jaddoe, V.W.V., Asimakopoulos, A., et al., 2018. Bisphenol and phthalate concentrations and its determinants among pregnant women in a population-based cohort in the Netherlands, 2004e5. Environ. Res. 161, 562e572. Philippat, C., Botton, J., Calafat, A.M., 2014. Prenatal exposure to phenols and growth in boys. Epidemiology 25, 625e635. Philippat, C., Mortamais, M., Chevrier, C., Petit, C., Calafat, A.M., Ye, X., et al., 2012. Exposure to phthalates and phenols during pregnancy and offspring size at birth. Environ. Health Persp. 120, 464e470.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS

454

25. BPA BIOMARKERS

Philippat, C., Nakiwala, D., Calafat, A.M., et al., 2017. Prenatal exposure to nonpersistent endocrine disruptors and behavior in boys at 3 and 5 years. Environ. Health Persp. 125, 097014. Richter, C.A., Birnbaum, L.S., Farabollin,i, F., et al., 2007. In vivo effects of bisphenol A in laboratory rodent studies. Reprod. Toxicol. 24, 199e224. Romano, M.E., Webster, G.M., Vuong, A.M., et al., 2015. Gestational urinary bisphenol A and maternal and newborn thyroid hormone concentrations: the HOME study. Environ. Res. 138, 453e460. Rønningen, K.S., Paltiel, L., Meltzer, H.M., et al., 2006. The biobank of the Norwegian mother and child cohort study: a resource for the next 100 years. Eur. J. Epidemiol. 21, 619e625. Rudel, R.A., Gray, J.M., Engel, C.L., et al., 2011. Food packaging and bisphenol A and bis(2-ethyhexyl) phthalate exposure: findings from a dietary intervention. Environ. Health Persp. 119, 914e920. Sabanayagam, C., Teppala, S., Shankar, A., 2013. Relationship between urinary bisphenol A levels and prediabetes among subjects free of diabetes. Acta Diabetol. 50 (4), 625e631. Shankar, A., Teppala, S., 2011. Relationship between urinary bisphenol A levels and diabetes mellitus. J. Clin. Endocrinol. Metab. 96, 3822e3826. Silver, M.K., O’Neill, M.S., Sowers, M.R., et al., 2011. Urinary bisphenol A and type-2 diabetes in U.S. adults: data from NHANES 2003e2008. PLoS One 6 (10), e26868. Snijder, C.A., Heederik, D., Pierik, F.H., et al., 2013. Fetal growth and prenatal exposure to bisphenol A: the Generation R Study. Environ. Health Persp. 121, 393e398. Spanier, A.J., Kahn, R.S., Kunselman, A.R., et al., 2012. Prenatal exposure to bisphenol A and child wheeze from birth to 3 years of age. Environ. Health Persp. 119, 916e920. Spanier, A.J., Kahn, R.S., Kunselman, A.R., Schaefer, E.W., et al., 2014. Bisphenol A exposure and the development of wheeze and lung function in children through age 5 years. JAMA Pediatr. 168, 1131e1137. Stacy, S.L., Eliot, M., Calafat, A.M., et al., 2016. Patterns, variability, and predictors of urinary bisphenol A concentrations during childhood. Environ. Sci. Technol. 50 (11), 5981e5990. Stacy, S.L., Papadonatos, G.D., Calafat, A.M., et al., 2017. Early life bisphenol A exposure and neurobehavior at 8 years of age: identifying windows of heightened vulnerability. Environ. Int. 107, 258e265. Stahlhut, R.W., Welshons, W.V., Swan, S.H., 2009. Bisphenol A data in NHANES suggest longer than expected half-life, substantial nonfood exposure, or both. Environ. Health Persp. 117, 784e789. Stahlhut, R.W., van Breeman, R.B., Gerona, R.R., et al., 2016. Comment on “Optimal exposure biomarkers for nonpersistent chemicals in environmental epidemiology”. Environ. Health Persp. 124, A66. Teeguarden, J.G., Twaddle, N.C., Churchwell, M.I., et al., 2016. Urine and serum biomonitoring of exposure to environmental estrogens. I: bisphenol A in pregnant women. Food Chem. Toxicol. 92, 129e142. Tewar, S., Auinger, P., Braun, J.M., et al., 2016. Association of bisphenol A exposure and attention-deficit/hyperactivity disorder in a national sample of U.S. children. Environ. Res. 150, 112e118. Usman, A., Ahmad, M., 2016. From BPA to its analogues: is it a safe journey? Chemosphere 158, 131e142.

Valvi, D., Casas, M., Mendez, M.A., et al., 2013. Prenatal exposure to bisphenol A and phthalates and childhood respiratory tract infections and allergy. Epidemiology 24 (6), 791e799. Vandenberg, L.N., Chahoud, I., Heindel, J.J., et al., 2010a. Urinary, circulating, and tissue biomonitoring studies indicate widespread exposure to bisphenol A. Environ. Health Persp. 118 (8), 1055e1070. Vandenberg, L.N., Chahoud, I., Padmanabhan, V., et al., 2010b. Biomonitoring studies should be used by regulatory agencies to assess human exposure levels and safety of bisphenol A. Environ. Health Persp. 118 (8), 1051e1054. Vandenberg, L.N., Ehrlich, S., Belcher, S.M., et al., 2013. Low dose effects of bisphenol A: an integrated review of in vitro, laboratory animal and epidemiology studies. Endocr. Disruptors 1, e25078. Vandenberg, L.N., Gerona, R.R., Kannan, K., et al., 2014a. A round robin approach to the analysis of bisphenol a (BPA) in human blood samples. Environ. Health 13, 25e45. Vandenberg, L.N., Welshons, W.V., Vom Saal, F.S., et al., 2014b. Should oral gavage be abandoned in toxicity testing of endocrine disruptors? Environ. Health 13, 46e53. Veiga-Lopez, A., Kannan, K., Liao, C., et al., 2015. Gender-specific effects on gestational length and birth weight by early pregnancy BPA exposure. J. Clin. Endocrinol. Metab. 100 (11), E1394eE1403. Vernet, C., Pin, I., Giorgis-Allemand, L., et al., 2017. In utero exposure to select phenols and phthalates and respiratory health in fiveyear-old boys: a prospective study. Environ. Health Persp. 125, 097006. Volkel, W., Kiranoglu, M., Fromme, H., 2011. Determination of free and total bisphenol A in urine of infants. Environ. Res. 111, 143e148. Volkel, W., Colnot, T., Csanady, G.A., et al., 2002. Metabolism and kinetics of bisphenol A in humans at low doses following oral administration. Chem. Res. Toxicol. 15, 1281e1287. Volkel, W., Bittner, N., Dekant, W., 2005. Quantitation of bisphenol A and bisphenol A glucuronide in biological samples by high performance liquid chromatography-tandem mass spectrometry. Drug Metab. Dispos. 33, 1748e1757. vom Saal, F.S., Welshons, W.V., 2014. Evidence that bisphenol A (BPA) can be accurately measured without contamination in human serum and urine, and that BPA causes numerous hazards from multiple routes of exposure. Mol. Cell. Endocrinol. 398, 101e113. WHO, 2001. Environmental Health Criteria 222, Biomarkers in Risk Assessment: Validity and Validation. United Nations Environment Programme (UNEP)/International Labor Organization (ILO)/ World Health Organization (WHO), Geneva, Switzerland. WHO, 2009. Bisphenol A (BPA). Current State of Knowledge and Future Actions by WHO and FAO. International Food Safety Authorities Network (INFOSAN Information Note No. 5/2009Bisphenol A. Ye, X., Pierik, F.H., Hauser, R., et al., 2008. Urinary metabolite concentrations of organophosphorous pesticides, bisphenol A, and phthalates among pregnant women in Rotterdam, the Netherlands: the Generation R Study. Environ. Res. 108, 260e267. Yolton, K., Xu, Y., Strauss, D., et al., 2011. Prenatal exposure to bisphenol A and phthalates and infant neurobehavior. Neurotoxicol. Teratol. 33, 558e566.

III. CHEMICAL AGENTS, SOLVENTS AND GASES TOXICITY BIOMARKERS