Impact of a water-damaged indoor environment on kindergarten student absences due to upper respiratory infection

Building and Environment 64 (2013) 1e6

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Impact of a water-damaged indoor environment on kindergarten student absences due to upper respiratory infection Yung-Chieh Tsao a, Yaw-Huei Hwang a, b, * a b

Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, College of Public Health, Taipei, Taiwan, ROC Department of Public Health, National Taiwan University College of Public Health, Taipei, Taiwan, ROC

a r t i c l e i n f o

a b s t r a c t

Article history: Received 23 October 2012 Received in revised form 17 January 2013 Accepted 1 February 2013

Children are relatively sensitive to health pollutants, including those in indoor environments. This study was conducted to explore the impact of a water-damaged indoor environment on children’s weekly absences resulting from upper respiratory infection in a kindergarten. Twenty-six and 27 children were recruited from water-damaged and non-water-damaged classrooms in the same building, and 936 and 1017 person-weeks were followed up during the study period of 42 weeks. Weekly absence rates were computed from daily absence records. The weekly absence rate was significantly higher for children in the water-damaged classroom (2.99%) than for those in the nonwater-damaged classroom (1.28%). After adjusting for gender and grade, the odds ratio for absence was 2.45 (95% CI: 1.15e5.24) for the children in the water-damaged classroom. Additionally, fungal concentration was significantly higher in the water-damaged classroom (993 CFU/m3) than in the nonwater damaged classroom (404 CFU/m3). It is tentatively concluded that, in the subtropics, fungal concentration is a better indicator than humidity for early-stage water damage. Periodic fungal measurement is recommended to alter the water-damaged effect. Ó 2013 Elsevier Ltd. All rights reserved.

Keywords: Water-damaged Absence rate Kindergarten Upper respiratory infection Fungi Humidity

This study illustrated the association of damp indoor environment with health-related impact on kindergarten student, and implied that elevated airborne fungal concentration, rather than the relative humidity, was correlated with this health impact. This study therefore suggests that periodic fungal monitoring can be an efficient indicator of potential dampness-related health risk in the early stage of dampness development in the indoor environment.

1. Introduction Lifestyles have changed rapidly and substantially in the last three decades. Because we spend an increasing amount of time indoors d up from 80% to 90% of our time d the indoor environment has attracted increasing research attention [1e4]. Pre-

* Corresponding author. Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Room 735, No. 17, XuZhou Road, Taipei 100, Taiwan, ROC. Tel./fax: þ886 2 33668081. E-mail address: [email protected] (Y.-H. Hwang). 0360-1323/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.buildenv.2013.02.002

school children constitute one of the groups most vulnerable to the effects of air pollutants, partly because their respiratory systems are not fully developed until approximately six years of age [5]. In the U.S., about 14 million students attend schools in buildings considered below indoor air quality standard [6]. One study reported a statistically significant increase in cough symptoms by 40%e50% in moisture-damaged schools, but no findings for other health symptoms [7]. Another study recruited currently asthma-afflicted students with higher relative humidity in their classrooms and higher mold and bacteria levels in the air and reported an elevated asthma attack rate. Within indoor air quality study, many researches has demonstrated the adverse health effects caused by indoor air pollutants, such as carbon monoxide (CO), volatile organic compounds (VOCs), formaldehyde (HCHO), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (PM), ozone (O3), and mold [8e15]. Of these harmful pollutants in the indoor environment, some are continuously emitted from materials in new construction, furniture, or decorations; some come from outdoor air; and others result from building operation (e.g., damaged air-conditioning system or poor building maintenance). Single or multiple substances will pollute indoor air quality and damage occupancy’s health. It is always a challenge in a study to well control these diversity pollutants synchronously for exploring the relationship of indoor pollutants and health outcome.

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Y.-C. Tsao, Y.-H. Hwang / Building and Environment 64 (2013) 1e6

Office zone Reading zone

Toilet I

Toilet II Playing zone

Note: 1: Water-damaged classroom (K-5 and K-6 mixed class). 2: Non-water-damaged classroom (K-5 and K-6 mixed class). 3: Pre-kindergarten classroom. 4: K-4 classroom. Fig. 1. Kindergarten layout for the water-damaged and non-water-damaged classrooms.

A great number of the nationwide or regional studies to determine which pollutants or factors are most important in controlling air quality. Examples include the Building Assessment Survey and Evaluation (BASE) in the U.S. and the Nordic Dampness (Nordic interdisciplinary review of the scientific evidence on associations between exposure to “dampness” in buildings and health effects, NORDDAMP) study. Epidemiological investigations within these projects have indicated that “dampness” in old buildings is an important factor in indoor air quality and should be thoroughly investigated. The American Housing Survey of the 2003 U.S. Census reported that 10.4% of U.S. homes had water damage resulting from exterior leakage, while 8% had water damage resulting from interior leakage. In a survey of 100 representative U.S. office buildings, 45% had current water leaks and 85% had past leaks [16]. Mudarri and Fisk analyzed eight previous studies and reported an average prevalence of 47% for dampness or mold in U.S. homes [17], weighted by population. The General Accounting Office found that 30% of U.S. schools had plumbing problems, 27% had waterproofing problems, and 63% of students in the U.S. attended schools where one or more building features were in need of extensive repair, overhaul, or replacement [18]. The adverse health effects of dampness or mold in indoor environments include not only respiratory symptoms (cough, wheeze and asthma), asthma, and allergy [19], but also nonspecific symptoms such as fatigue and headaches [6]. In Europe, NORDDAMP demonstrated that the range of relative risks for health effects in the airways, such as cough, wheeze, and asthma, were 1.4e2.2 [12]. In 2004, the Institute of Medicine (IOM) of the U.S. National Academy of Sciences reported a 30e50% increase in a variety of adverse respiratory and asthma-related health outcomes as a result of exposure to dampness or mold in the indoor environment [20e23]. In Taiwan, located in the subtropics, dampness has been reported to be associated with asthma (odds ratios: 1.77; 95% confidence interval (CI): 1.24e2.53) [24] and respiratory

syndromes (odds ratios ranging from 1.72 to 1.98), including cough, wheezing, bronchitis, and asthma [25]. These studies concluded that the evidence for an association between “dampness” and health effects is strong. However, the specific agents (e.g., molds, bacteria, or organic chemicals) causing these health effects remains uncertain. However, no existing study examines the association between water-damaged environments on sick leaves due to clinically diagnosed upper respiratory tract infection. Therefore, the present study was conducted (1) to compare the prevalence of diagnosed respiratory tract infections among students in water-damaged and non-water-damaged classrooms and (2) to determine the primary indoor air factors involved in these adverse health effects. 2. Materials and methods 2.1. Study site The study was conducted in an affiliated kindergarten funded by an electronics manufacturing company, located in Hsinchu Science Park in northwestern Taiwan. The kindergarten is in a building enveloped by a glass wall and equipped with an air handling unit (AHU) but no windows or natural ventilation. No decorations were added in recent years and, therefore, volatile organic compounds (VOCs) and formaldehyde emissions into the air from new furniture were limited. The kindergarten consists of four classrooms, including one for pre-kindergarten toddlers, one for four-year-olds (K-4), and two for five- and six-year-olds (K-5 and K-6). All classrooms were covered with wood flooring and included a sink for hygienic convenience. At August of 2009, teachers found that water slopped out from under the wooden floor when stamped on in one of the K-5 and K-6 mixed-age classrooms; this classroom was designated water-damaged. This did not occur in the prekindergarten classroom. Later, visible mold appeared on the

Y.-C. Tsao, Y.-H. Hwang / Building and Environment 64 (2013) 1e6 Table 1 Demographics of the study children by classroom with or without water damage.

Number Person-week Gender Boys Girls Age, year old Grade K-6 K-5 Weekly absence rate (%)

No waterdamage

Waterdamage

All

P value

27 1017

26 936

53 1953

14 13 5.25  0.51

16 10 5.13  0.57

30 23 5.19  0.54

NS

18 9 1.28

16 10 2.99

34 19 2.1

NS 0.0094

bulletin board on the wall between Toilet I and the water-damaged classroom (Fig. 1). 2.2. Recruited children The kindergarten was only open to employees’ children for enrollment. This study recruited 26 children in the water-damaged K-5 and K-6 mixed-age classroom and 27 children in the nonwater-damaged K-5 and K-6 mixed-age classroom. These children were followed for 42 weeks from August 2009 to June 2010. During the study period, three weeks were not counted, including one week for the Chinese Lunar New Year holiday and two weeks for class suspension due to an influenza epidemic. 2.3. Absence record and weekly absence rate Records of daily absences due to upper respiratory infection were provided by the kindergarten teacher, and the clinical diagnoses were confirmed with the absentees’ parents. Two weekly absence rates were recruited into this study to compare the influence from outside of school. Firstly, the general weekly absence rate is defined as any absence occurred in a week. Secondly, only absences occurring on Tuesday, Wednesday, Thursday and Friday were included in the weekly absence rate calculation, as a Monday absence could be attributed to weekend activities outside of school. Weekly absence rate was calculated as the number of children absent due to upper respiratory infection divided by the number of children in the classroom. A three-week moving average absence rate was also applied to smoothly present absence rate due to upper respiratory infection during the whole follow up study period. 2.4. Airborne fungi and bacteria measurement Airborne fungi and bacteria samples were collected using the BioStage viable cascade impactor (SKC Inc. Eighty Four, PA, USA) with Malt Extract Agar plates (MEA) and Tryptic Soy Agar (TSA) at a flow rate of 28.3 l/min [26]. The sampling height was 1.2e1.5 m (i.e., near the human breathing zone). Samplers were set at the center of each classroom for 5-min sampling. Between every two consecutive measurements, the samplers were swabbed with 70% ethanol. Airborne fungi and bacteria were collected twice a day on the scheduled sampling dates, at approximately 9:00 to 9:30, while the children were arriving at school, and approximately 14:30 to 15:00, while the children took naps. A total of seven sampling sites were chosen, i.e., four classrooms, playing zone, reading zone, and office zone as shown in Fig. 1. Two sampling dates were scheduled in September of 2009 and March of 2010. After field sampling, the plates with MEA were incubated at 25  C for 5 days for fungal growth, and the plates with TSA were incubated at 30  C for 2 days to estimate levels of bacteria growth. Fungi were identified

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morphologically according to mycology references (Barnett et al., 1987). Colony-forming units per cubic meter (CFU/m3) was used to demonstrate the levels of fungal and bacteria in the air. All the bioaerosol samplings were conducted in replicate. Average concentrations of these samples were used to present the microbial levels for each sampling time at each sampling site. 2.5. Statistical analysis As the weekly absence rates were not distributed normally, the KolmogoroveSmirnov test was used to determine whether there was a difference in absence rates between the two classrooms. The relationship between the weekly absence rates in the two classrooms was examined using the generalized estimating equation (GEE) approach as implemented in the GENMOD procedure in SAS. An autoregression covariance matrix adjusted for the correlations within study children. Taking into account the correlations between demographic variables, we used the GEE-estimated regression coefficients to compare the difference in upper respiratory tract infection related absence in the water-damaged and nonwater-damaged classrooms. All of the statistical analyses were performed with the Statistical Analysis System (SAS version 9.1, Cary, North Carolina, USA). 3. Results Table 1 shows the demographics of the recruited children. The children were followed for a total of 1953 person-weeks, comprising 936 and 1017 person-weeks in the water-damaged and non-water-damaged classrooms, respectively, during the 42week study period. Both classes contained more boys than girls; the class in the water-damaged room contained 61.5% boys. Enrollment ages were not significantly different between these two classes (5.25  0.51 versus 5.13  0.57 years old). In addition, there were more K-6 children than K-5 children in each class, but no significant difference between K-5 and K-6 children on weekly absence rate. Five out of 53 children were not followed throughout the entire study period due to parent’s resignation, but they were followed for at least 10 weeks. For children of the non-water-damaged classroom, the weekly absence rates were 1.87% for any upper respiratory infection absence occurring from Monday through Friday within a week (definition I) and 1.28% for any absence occurring from Tuesday through Friday (definition II). Meanwhile, the weekly absence rates for children of the water-damaged classroom were 3.47% with definition I and 2.99% with definition II. With either definition, significantly higher weekly absence rate in water-damaged classroom than non-water-damaged classroom were observed (p ¼ 0.0118 and p ¼ 0.0094, respectively). Since this study focused on water-damaged environment related health impact, definition II was preferred to express the absence attributed to classroom dampness by eliminating confounding effect of sick leave on Monday that might be attributed to contagious contacts occurring outside school during weekend. Fig. 2(a) presents the weekly absence rates for these two classes in water-damaged and nonwater-damaged classrooms, respectively, and Fig. 2(b) shows the same data as three-week moving average absence rate. Both figures show that the absence rate for the class in the water-damaged classroom was greater than the rate in the non-water-damaged classroom for thirty out of forty-two weeks. The weekly absence rate for the class in the water-damaged classroom peaked in the 7th, 17th, and 39th weeks. Although gender and grade show no effect on weekly absence rate, K-5 children had marginally higher odds of being absent than K-6 children, with an OR of 2.02 (95% confidence interval (CI):

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Y.-C. Tsao, Y.-H. Hwang / Building and Environment 64 (2013) 1e6 14.0

Water-damaged

Non-water-damaged

12.0

10.0

8.0

6.0

4.0

2.0

0.0 1

2 3

4

5 6 7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

(a). Weekly absence rate for the classes in water-damaged and non-water-damaged classrooms. 14.0

Water-damaged

Non-water-damaged

12.0

10.0

8.0

6.0

4.0

2.0

0.0 1

2 3

4

5 6 7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

(b). Three-week moving average absence rate for the classes in water-damaged and non-water-damaged classrooms. Fig. 2. Weekly and three-week moving average absence rate for the classes with water-damaged and non-water-damaged classrooms.

0.99e4.11, P ¼ 0.054). After adjusting for these two demographic factors, children in the water-damaged classroom presented a significant OR of 2.45 (95% CI: 1.15e5.24) for absence due to upper respiratory tract infection as compared to those in the classroom without water damage (Table 2). Table 3 shows the indoor air quality measurements for temperature, humidity, carbon dioxide (CO2), bacteria, and fungi levels in September of 2009 and March of 2010 at seven locations, including four classrooms, office, reading zone, and playing zone. Bacteria and fungi levels were only determined in March of 2010. There is no significant difference on temperature, humidity and CO2 concentration between the two measurements in March and September, respectively. It indicated that the air conditioning system worked very well in this kindergarten, even in different seasons, i.e., fall and spring, in Taiwan. All CO2 measurements were below 1000 ppm recommended by ASHRAE for indoor environments [27], indicating efficient air-conditioning system. All bacteria concentrations exceeded 1000 CFU/m3 and were averaged 1700  956 (mean  SD) CFU/m3, while fungi concentration was averaged 443  322 CFU/m3, all below 1000 CFU/m3. Although bacteria concentrations in the water-damaged (1769 CFU/m3) and non-water-damaged (1863 CFU/m3) classroom were quite close, fungal concentration for the water-damaged classroom 993 CFU/

m3, was significantly higher than that of non-water damaged classroom, 404 CFU/m3. 4. Discussion In this longitudinal study, an odds ratio of 2.45 was obtained, demonstrating an association between kindergarten children’s sick leave with clinically diagnosed upper respiratory tract infection with the water-damaged indoor environment. Compared with other studies, e.g., in Europe (OR: 1.4e2.2) [12] and worldwide (OR: 1.7) [21], this study presents a very high OR value. In Taiwan, several previous studies have pointed out that the fungal genera of Aspergillus, Penicillium, Cladosporium, Alternaria, and yeast predominated the total fungal concentration in the subtropical region, in which fungal levels were higher than in other regions [28e33]. In this study, the high observed fungal concentrations are strongly believed to result from the long-term water damaged in the environment. This damp environment likely encouraged fungal growth [34e39]. It is well known that humidity in excess of 70% promotes fungal growth. In general, Taiwan, located in the subtropics, is naturally in a condition of high outdoor humidity (73e90%) [40]. Consequently, Li et al. reported that the average indoor fungal concentration of a

Y.-C. Tsao, Y.-H. Hwang / Building and Environment 64 (2013) 1e6

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Table 2 Unadjusted and adjusted odds ratios for the risks of gender, grade and exposure group on the weekly absence rate. Present N ¼ 1912 (person-week)

Water-damage No 1004 Yes 908 Gender Boys 1052 Girls 860 Grade K-6 1155 K-5 757 a

%

Absence N ¼ 41 (person-week)

%

Unadjusted

Adjusted

OR

95% CI

OR

95% CI

(98.7) (97.0)

13 28

(1.3) (3.0)

1 2.33*

(1.05e5.20)

1 2.45*

(1.15:5.24)

(98.5) (97.2)

16 25

(1.5) (2.7)

1 1.71

(0.82:3.57)

1 1.65

(0.83:3.28)

(98.6) (96.8)

16 25

(1.6) (3.2)

1 2.02a

(0.99:4.11)

1 2.02b

(0.92:3.76)

b

Note: *: p < 0.05. .p ¼ 0.054. .p ¼ 0.082.

room without air conditioning, approximately 1500 CFU/m3, is closely correlated with the outdoor fungal concentration [28e30]. In contrast, Su et al. showed that fungal concentrations in office buildings equipped with air conditioning systems were less affected by the outdoor environment and usually less than 1000 CFU/m3, with air-handling unit (AHU) systems performing better and being less affected by outdoor fungal concentration than fan coil unit (FCU) systems [31]. In this study, the outdoor fungal level was determined as of 856 CFU/m3, while the indoor fungal concentration of the non-water damaged classroom was only 404 CFU/m3, well below and not associated with the outdoor fungal level. This situation closely paralleled the finding by Su et al. [31], implying the air condition system, i.e., AHU system, of the classrooms in the present study functioned very well and effectively limited the influence of outdoor dampness on the indoor environment. Since both the water-damaged and the non-waterdamaged classrooms shared the same AHU system in a building and this air conditioning system was periodically maintained by wind speed checking, temperature monitoring, filter inspection and replacement, it was inferred that the water-damaged classroom would not be affected by the outdoor air dampness, either. Accordingly, the difference in indoor fungal concentration between the water-damaged and the non-water-damaged classrooms could be mostly attributed to the water-leak resulted dampness. Water is essential for both fungal growth and bacterial growth. In general, bacteria require more water than fungi and are therefore more likely to grow outdoors than indoors, especially in areas with high humidity [41]. In this study, the similar measurements for total bacteria, 1863 and 1769 CFU/m3, observed in the two study classrooms seemed to indicate no difference in the impact on the studied health effect due to the existing bacteria. However, Hyvärinen et al. found that Streptomycetes can grow on damp or wet building material [42]. Solomon et al. suggested that endotoxins from Gram-negative bacteria occur at elevated levels in damp buildings [39]. Both studies show that some bacteria species can grow in damp indoor environments, with adverse health Table 3 Indoor air quality on temperature, relative humidity, CO2, bacteria, and fungi concentration.

Temperature ( C) Relative Humidity (%) CO2 (ppm) Bacteria (CFU/m3) Fungi (CFU/m3)

September, 2009 (n ¼ 7)

March, 2010 (n ¼ 7)

23.7  0.29 70.9  1.92 816  112

23.5 69.2 726 1700 443

    

0.28 1.90 143 956a 322b

a The bacteria concentration for water-damaged classroom was 1769 CFU/m3 and for non-water-damaged classroom was 1863 CFU/m3. b The fungal concentration for water-damaged classroom was 993 CFU/m3 and for non-water-damaged classroom was 404 CFU/m3.

impacts on human beings. Therefore, while this study demonstrated the differential health impacts of fungal concentrations in the studied classrooms, further study is warranted to explore the role of bacteria species in the relationship between dampness and health effects in terms of sick leave due to upper respiratory tract infection. The definition of dampness is a key factor in exposure assessment in the various studies on the health effects of indoor dampness. In the WHO’s definition [43], any visible, measurable, or perceived outcome linked to excess moisture constitutes a damp environment. This three-part definition has been widely used in multidisciplinary research, but few studies clearly consolidated these three definitions together into the study design. In this study, an indoor environment was considered damp if there was visible mold, evident leakage from the toilet, slightly higher relative humidity, or higher fungal concentration. All of these indicators were present in the water-damaged classroom; visible mold was the sign that first caught our attention and prompted us to make the additional measurements that led to the positive identification of water leakage. However, visible mold is quite common in buildings in the subtropics, where humidity over 70% is not unusual [31]. This tends to reduce building occupants’ alertness to possible water leakage inside. In this study, the humidity measurements in both classrooms were too close to provide an indication of possible indoor water leakage, as the AHU system kept the indoor environment from becoming uncomfortably damp. This made the occupants likely to neglect the leakage. In general, indoor air quality is difficult to measure accurately and reliably because it depends on the outdoor air, occupants’ activity, and the functioning of the air conditioning system. All three of these factors influence the appropriate choice of dampness indicator. Nevertheless the results of this study suggest that fungal concentration measurements serve as valid indicators of possible water leakage in buildings equipped with functioning air conditioning systems. This result leads us to strongly recommend fungal concentration as an appropriate indicator to evaluate the possibility of suspected water damage in association with health effects in air-conditioned buildings in the subtropics. In this study, effort has been made to isolate the effect of indoor water damage on sick leave due to upper respiratory tract infection. First, the study omitted Monday absences to eliminate the confounding effect of sick leaves attributed to contagious contacts occurring outside of school. This increased the likelihood that a given measured absence was due to classroom dampness, increasing the reliability of our observations of the effects of indoor dampness on health. Second, all of the study children’s parents were employees of the same electronics manufacturing company, generally recognized as ranking high in terms of annual income and education in Taiwan, and believed to live in residences with aboveaverage indoor environmental quality. This constrained variation

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due to socioeconomic status among the study children’s families, reducing the likelihood of interfering factors in the children’s home environments. Third, the two study classrooms were located in the same building, shared an AHU system with the same air exchange rate, were of similar physical plan, and accommodated the same number of children. By controlling the potential effects of the air conditioning system, air exchange rate, number of occupants, and classroom size, this study took advantage of the environmental similarities of the two study classrooms to isolate the effect of water-damage-induced dampness on sick leave resulting from upper respiratory tract infection. 5. Conclusion As the number of buildings with air-conditioning systems grows, the factors influencing indoor air quality become complicated and it becomes difficult to identify dampness-related indoor environmental problems, especially in sub-tropical areas like Taiwan. This study illustrated the association of dampness-related health impacts in a kindergarten with airborne fungal concentration rather than the relative humidity. In addition, this study shows that periodic fungal monitoring can be an efficient indicator of potential dampness-related health risks in the early stages of dampness development in the indoor environment. References [1] Klepeis NE, Tsang AM, Behar JV. Analysis of the National Human Activity Pattern Survey (NHAPS) responses from a standpoint of exposure assessment. EPA/6000/R-96/074. Contract 68-01-7325 to Information Systems and Services, Inc.. Las Vegas, NV: U.S. Environmental Protection Agency; 1996 [2] Klepeis NE, Nelson WC, Ott WR, Behar JV, Hem SC, Engelman WH. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J Expo Anal Environ Epidemiol 2001;11(3):231e52. [3] De Bruin YB, Carrer P, Jantunen M, Cavallo D, Maroni M. Personal carbon monoxide exposure levels: contribution of local sources to exposures and microenvironment concentrations in Milan. J Expo Anal Environ Epidemiol 2004;14(4):312e22. [4] Schweizer C, Edwards RD, Bayer-Oglesby L, Lai HK, Nieuwenhuijsen M, Kuzli N. Indoor time-microenvironment-activity patterns in seven regions of Europe. J Expos Sci Environ Epidemiol 2006;17(2):170e81. [5] Schwartz J. Air pollution and children’s health. Pediatrics 2004;113:1037e43. [6] Jones AP. Indoor air quality and health. Dev Environ Sci 2002;1:57e115. [7] Meklin T, Husman T, Vepsalainen A, Vahteristo M, Koivisto J, Halla-Aho J, et al. Indoor air microbes and respiratory symptoms of children in moisture damaged and reference schools. Indoor Air 2002;12(3):175. [8] Yu C, Crump D. A review of the emission of VOCs from polymeric materials used in buildings. Build Environ 1998;33(6):357e74. [9] Nevalainen A, Pasanen AL, Niininen M, Reponen T, Kalliokoski P, Jantunen MJ. The indoor air quality in Finnish homes with mold problems. Environ Int 1999;17(4):299e302. [10] Singer BC, Coleman BK, Destaillats H, Hodgson AT, Lunden MM, Weschler CJ, et al. Indoor secondary pollutants from cleaning product and air freshener use in the presence of ozone. Atmos Environ 2006;40(35):6696e710. [11] Haghighat F, De Bellis L. Material emission rates: literature review, and the impact of indoor air temperature and relative humidity. Build Environ 1998;33(5):261e77. [12] Bornehag CG, Blomquist G, Gyntelberg F, Jarvholm B, Malmgerg P, Nordvall L, et al. Dampness in buildings and health Nordic interdisciplinary review of the scientific evidence on associations between exposure to “dampness” in buildings and health effects (NORDDAMP). Indoor Air 2001;11(2):72e86. [13] Schildcrout JS, Sheppard L, Lumley T, Slaughter JC, Koenig JQ, Shapiro GG. Ambient air pollution and asthma exacerbations in children: an eight-city analysis. Am J Epidemiol 2006;164(6):505e17. [14] Kagi N, Fujii S, Horiba Y, Namiki N, Ohtani Y, Emi H, et al. Indoor air quality for chemical and ultrafine particle contaminants from printers. Build Environ 2007;42(5):1949e54. [15] Moon JS, Kim YS, Kim JH, Soon BS, Kim DS, Yang W. Respiratory health effects among school children and their relationship to air pollutants in Korea. Int J Environ Health Res 2009;19(1):31e48.

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