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Elevated hair levels of cadmium and lead in school children exposed to smoking and in highways near schools
Clinical Biochemistry 40 (2007) 52 – 56
Elevated hair levels of cadmium and lead in school children exposed to smoking and in highways near schools Tülin Ayşe Özden a,⁎, Gülbin Gökçay a , Hayriye Vehid Ertem a , Özlem Durmaz Süoğlu a , Ayşe Kılıç a , Semra Sökücü b , Günay Saner a b
a Institute of Child Health, Istanbul University, Çapa 34093, Istanbul, Turkey Department of Child Health, Istanbul University, Istanbul Medical Faculty, Çapa 34093, Turkey
Received 9 June 2006; received in revised form 25 July 2006; accepted 27 July 2006 Available online 12 August 2006
Abstract Objectives: Heavy metal pollution has become a serious health concern in recent years. Cadmium (Cd) and Lead (Pb) are toxic heavy metals. This study was aimed to determine the risk factors for high cadmium and lead levels in school children. Design and methods: The scalp hair samples were obtained from 760 children at 13 schools in Istanbul. A questionnaire was prepared to gather information about demographic and socioeconomic characteristics of the children. Hair cadmium and lead concentrations were determined by atomic absorption spectrophotometer. Results: Household exposure to smoking and attending a school near to Main Streets were found to be the most important risk factors for the high hair cadmium and lead levels in our study. Conclusion: These findings support the public health recommendations that children should not have household exposure to smoking, schools should not be near to the main streets and unleaded gasoline use should be promoted. © 2006 The Canadian Society of Clinical Chemists. All rights reserved. Keywords: Toxic metals; Cadmium; Lead; Environmental exposure; School children; Hair analysis; Smoking
Introduction Heavy metal pollution has become a serious health concern in recent years. Cadmium (Cd) and lead (Pb) are toxic heavy metals. Continuous exposure to low levels of these toxic heavy metals may result in bioaccumulation and can cause a wide variety of biological effects on human beings depending upon the level and the duration of exposure [1,2]. Long-term, lowlevel exposure to cadmium will result in accumulation in liver and kidneys, the main storage organ to cadmium [3]. Several studies have suggested that even low levels of lead exposure may cause adverse impacts on cognitive functioning [4,5]. These metals can be found in the work place, drinking water, in food, consumer products, enamel utensils and traditional medicines [6,7].
⁎ Corresponding author. Fax: +90 212 631 39 97. E-mail address: [email protected] (T.A. Özden).
These metals enter the human body mainly after inhalation and also via gastrointestinal absorption. Inhalation is the second major means of cadmium and lead absorption for children [6– 9]. The strength of the problem depends on the body dimensions of the child. In addition, children absorb greater percentage of ingested lead than adults [9]. Many authors have reported that human hair is a good indicator of environmental pollution. Therefore using scalp hair as an indicator of the environmental exposure to several trace elements has become a common method [10–12]. However, there is no definite result about the significance of Cd in hair as an index of exposure [13]. With the increasing importance of these metals in clinical medicine, reference ranges of these metals in biological samples are needed as tools for diagnosis. However, trace element concentrations in biological samples are affected by environmental and geographical factors. Therefore, considerable variations can occur between specific subgroups of the populations [2].
0009-9120/$ - see front matter © 2006 The Canadian Society of Clinical Chemists. All rights reserved. doi:10.1016/j.clinbiochem.2006.07.006
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
The current study was carried out among school children in Istanbul, which is a big city with heavy traffic as well as some industrial emissions from the surrounding districts. The Table 1 Sociodemographic characteristics of children Variables
n
%
Gender Male Female
331 429
43.6 56.4
Child employment status Yes No Unknown
16 738 6
2.1 97.1 0.8
Maternal education Illiterate Primary Secondary High school University
40 312 144 192 72
5.3 41.1 18.9 25.3 9.4
Paternal education Illiterate Primary Secondary High school University Unknown
12 203 198 207 138 2
1.6 26.7 26.1 27.2 18.2 0.2
Maternal working status Yes No Unknown
190 568 2
25.0 74.7 0.3
Paternal working status Unemployed Laborers–civil servant Private business Unknown
20 310 419 11
2.6 40.8 55.1 1.5
Insurance Yes No Unknown
168 557 5
22.1 73.3 0.6
Socioeconomic status High middle Middle Low middle Low
306 153 194 107
40.3 20.1 25.5 14.1
Home ownership Yes No
239 521
31.4 68.6
Heating style Coal–stove Furnace Natural gas Unknown
270 202 287 1
35.5 26.6 37.8 0.1
Mother smoking Yes No
337 423
44.3 55.7 (continued on next page)
53
Table 1 (continued) Variables
n
%
Number of smokers at home 0 1 2 ≥3
173 289 237 61
22.8 38.0 31.2 8.0
challenge against toxic element exposure varies from country to country. However, the required steps to eliminate the effects are now apparent [8]. The aim of this study was to asses the concentration of cadmium and lead in hair and to determine the risk factors for high lead and cadmium levels in school children in Istanbul. Material and methods Study population The approval of the Medical School Ethic Committee was obtained at the beginning of the study. The permission of Istanbul Education Directorate was sought before receiving the consents of both the school administration and the parents. The study was conducted in 13 elementary schools in Istanbul. The schools were chosen according to the distance from the main streets in the both sides of Istanbul. A questionnaire was sent to 1500 students at 5th and 6th grades, whose ages were ranging between 11 and 13 years. Of all these students' families 894 have accepted to give hair samples. We were able to take hair samples from 760 children who were present during the study day. Since 134 boys had very short hair cut, no hair sample could be obtained from these children. Out of 13 schools, 7 were close to the main streets. A questionnaire was prepared to gather information about demographic and socioeconomic characteristics of the families and the smoking status of the household people. Analytical methods and instrumentation Hair samples were cut in 0.5 cm using stainless steel scissors to avoid contamination. Hair samples of the children were collected from suboccipital area of the head in immediate proximity to the scalp and stored in plastic bags. The proximal hair length was 2–2.5 cm and the proximal weight was around 100–200 mg. Duplicated hair samples of approximately 50– 200 mg were washed sequentially three times in hexane, pure analyze analytical grade ethanol and fresh bidistilled water. They were dried at 75°C in a vacuum oven for a night, 20– 100 mg weighted in polyethylene vial. Hair was digested using perchloric acid and nitric acid. Digestion was made between 65 and 75°C [9,14,15]. Ashed samples were then dissolved in 1 mL of 0.5 M nitric acid and 10 μl aliquots were injected into graphite furnace by an auto sampler. The concentration of lead and cadmium in hair was determined by double beam atomic absorption spectrophotometer Varian spectraAA-200 equipped with GTA-100 [16].
54
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
Statistical analyses
Table 2 Determinants of hair cadmium levels
Hair cadmium and lead levels of children were not normally distributed therefore the distance of the schools to the main street, ownership of the house, socioeconomic status, mother smoking habits, gender, insurance status, working status of the mother and the father, the number of smokers at home, heating style were grouped with respect to the median hair cadmium and lead levels. Furthermore, these groups were analyzed with Pearson Chi-square test. Logistic regression analyses were used to determine the effects of the above parameters on the hair cadmium level and hair lead level medians. Spearman correlation analysis was carried out between hair cadmium and lead levels. The classification of socioeconomic status of the children was made according to Neyzi criteria [17].
Variables
Results Of the 760 students whose scalp hair samples were obtained and evaluated for analysis 43.6% were male and 55% were from the schools close to the main streets. Sociodemographic characteristics of the students are shown in Table 1. This socioeconomic classification was made according to the education levels of the parents and the occupation of the fathers. The percentage of children from high middle, middle, low middle and low socioeconomic levels of children were 40.3%, 20.1%, 25.5% and 14.1% respectively (Table 1). Of all mothers, 5.3% were illiterate, 60% primary or secondary school graduates and 25% working. Of all fathers 1.6% were illiterate, 52.8% the graduates of primary or secondary school, 40.8% laborers or civil servants and 55.1% had private business. Of all mothers 44.3% were smokers. Of all children, 22.8% had no smoker at home and 2.1% were working (Table 1). The values of hair cadmium and lead levels were not normally distributed. The mean values of the hair cadmium and lead levels of all children were 53.38 ± 44.13 μg/g, 2.41 ± 2.22 μg/g, respectively. Median values (cut off) of hair cadmium and lead levels are 40 ng/g and 1.9 μg/g, respectively. There was a weak correlation between hair Cd and Pb levels (rs = 0.44). Hair cadmium and lead levels were grouped as either above or equal and below median values for the analyses. As the number of smokers at home increased, the proportion of children with hair cadmium and lead levels above the median also increased. These differences were found to be statistically significant (Tables 2, 3). The distance of the school to the main street and socioeconomic status had statistically significant impact on the hair lead and cadmium levels (Tables 2, 3). The logistic regression analyses have demonstrated that the distance of school to the main street (ORCd: 0. 676; 0.488– 0.936 95% CI), existence of a smoker at home had statistically significant impacts on the hair cadmium levels (Table 4). According to the results of logistic regression analysis, boys had higher hair cadmium levels and students from the schools far from the main street had lower hair cadmium
Hair cadmium levels <40.0 ng/g
≥40.0 ng/g
N
%
N
%
161 216
48.6 50.3
170 213
51.4 49.7
Pearson χ2
P
df
0.218
0.6
1
Comparative distance of school to main street Far 184 53.8 158 46.2 Close 193 46.2 225 53.8
4.379
0.036
1
Mother smoking Yes No
Gender Male Female
147 230
43.6 54.4
190 193
56.4 45.6
8.676
0.003
1
Maternal employment Yes 83 No 293
43.7 51.6
107 275
56.3 48.4
3.555
0.059
1
Child employment Yes 12 No 363
75.0 49.2
4 374
25.0 50.8
4.174
0.041
1
Insurance Yes No
75 283
44.6 50.8
93 274
55.4 49.2
1.963
0.161
1
Home ownership Yes No
123 254
51.5 48.8
116 267
48.5 51.2
0.482
0.487
1
Number of smokers at home 0 86 49.7 1 146 50.5 2 126 53.2 ≥3 19 31.1
87 143 111 42
50.3 49.5 46.8 68.9
9.612
0.022
3
Heating style Coal–stove Furnace Natural gas
49.6 51.5 48.4
136 98 148
50.4 48.5 51.6
0.442
0.802
2
0.269
0.874
2
3.745
0.290
3
134 104 139
Paternal working status Unemployed 11 Laborers–civil 152 servant Private business 210
55.0 49.0
9 158
45.0 51.0
49.5
214
50.5
Socioeconomic status High middle 152 Middle 72 Low middle 106 Low 47
49.7 47.1 54.6 43.9
154 81 88 60
50.3 52.9 45.4 56.1
levels than the students from the schools near to the main street (Table 4). The logistic regression analyses showed that school distance to the main street, gender (ORpb: 1.558; 1.132–2.145 95%) and number of smokers at home (ORPb: 0. 229; 0.164–0.321 95% CI) had statistically significant impact on hair lead levels (Table 4).
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
Discussion In this study cadmium and lead levels were analyzed in the scalp hair of school children to assess the extent of the burden of pollution in the body. School distance to the main street and presence of a smoker at home was found to be important factors. Schuhmacher et al. [16] showed that blood and hair lead levels decreased during the period 1990–1995 after reduced leaded Table 3 Determinants of hair lead levels Variables
Gender Male Female
Hair lead levels <1.9 μg/g
≥1.9 μg/g
n
%
n
%
146 234
44.1 54.5
185 195
55.9 45.5
Comparative distance of school to main street Far 268 64.1 150 35.9 Close 112 32.7 230 67.3
Pearson χ2
8.141
P
df
0.004
1
74.024
0.000
51.1 49.2
165 215
49.0 50.8
0.261
0.609
1
Maternal employment Yes No
97 282
51.1 49.6
93 286
48.9 50.4
0.112
0.737
1
Child employment Yes No
7 369
43.9 50.9
9 369
56.3 50.0
0.245
0.621
1
Insurance Yes No
81 279
48.2 50.1
87 278
51.8 49.9
0.182
0.670
1
Home ownership Yes No
125 255
52.3 48.9
114 266
47.7 51.1
0.739
0.390
1
Number of smokers at home 0 99 1 160 2 115 ≥3 6
57.2 55.6 48.5 9.8
74 129 122 55
42.8 44.6 51.5 90.2
46.505
0.000
3
Heating style Coal–stove Furnace Natural gas
119 108 152
44.1 53.5 53.0
151 94 135
55.9 46.5 47.0
5.769
0.056
2
Paternal working status Unemployed 11 Laborers–civil servant 141 Private business 224
55.0 45.5 52.8
9 169 200
45.0 54.5 47.2
4.082
0.130
2
Socioeconomic status High middle Middle Low middle Low
52.0 56.2 46.8 44.9
147 67 107 59
48.0 43.8 55.2 55.1
6.023
0.111
3
df: degrees of freedom.
Variables
For cadmium No smoker a Only one smoker a School far from the main street b For Lead Male School far from the main street b No smoker at home a Only one smoker at home a High–middle socioeconomic status c a b
Sig.
Exp. (β)
Confidence interval (95%) Lower limit
Upper limit
0.000 0.000 0.018
0.104 0.055 0.392 0.234 0.676 0.488
0.194 0.658 0.936
0.007 0.000 0.000 0.000 0.005
1.558 0.229 0.179 0.361 2.939
2.145 0.321 0.361 0.621 6.189
1.132 0.164 0.089 0.209 1.396
More than one smoker. School close on the main street. Low socioeconomic status.
1
172 208
a
Table 4 The effect of some variables on cadmium and lead levels according to logistic regression analysis
c
Mother smoking Yes No
159 86 87 48
a
55
gasoline consumption. Consumption of lead free petroleum in China leads to a decrease in blood lead levels in children [18]. Weaver [19] found that the blood lead levels of children living near the city centers were over 20 μg/mL. Tobacco contains varying amounts of cadmium and lead. A cigarette generally contains 1–2 μg cadmium, 0.6–17 μg lead [20–22]. About 10% of this amount may be inhaled. The use of insecticides with lead arsenate in tobacco fields may be the cause of high lead levels in tobacco plants. Apart from that, cadmium and lead in soil penetrate easily into tobacco plant while growing. These particles in air are accumulated on the leaves of tobacco plant and can also become a source of these toxic elements [19]. Cigarette smoking is an important predictor for heavy metal exposure, especially of cadmium and lead. Wolfsperger et al. [23] showed that smoker's hair lead levels were higher than non-smoker hair lead levels. In Morocco, Lekouch et al. showed that average hair lead levels were higher in children exposed to wastewater which contains lead than in the non-exposed children [24]. Some workers [25,26] indicated that smoking increased blood cadmium concentration. Weyerman and Brenner [20] found a dose response relationship between amounts of tobacco smoked each day and blood lead levels. Many studies showed that parents' smoking habits or passive smoking had an impact on children's blood lead levels [27–29]. Willers et al. [28] also found a dose response relationship between the amount of tobacco smoked by the mother and blood lead levels of children. In these students, we reported that presence of a smoker at home and living close the heavy traffic affect blood lead levels [30]. Our results are in agreement with these studies and showed similar findings for the hair lead levels of the student. These findings support that passive or active smoking contributes to Cd and Pb toxicity. Some investigators reported that blood Pb [2,21], hair Pb and Cd [12] levels in male were higher than in female. In our study hair Pb and Cd levels were found higher in male than in female and this difference was statistically significant for Cd levels.
56
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
The reason for a higher hair Pb and Cd levels in males may be probably due to difference in out door activities, health behaviors, difference of urine excretion or kidney activities [2]. To our knowledge, this is the only study on hair Cd levels in school children. Our study had some limitations. The study sample was not selected randomly and cannot be generalized to the whole population but the students were from a heterogeneous group. We did not gather information about the smoking habits of fathers because fathers generally spend most of their time out of home and away from their children. This may be a limitation for our study but we do not think that we missed any additional findings about passive smoking. In conclusion, our findings support the public health recommendations that children should not have household exposure to smoking, schools should not be near to the main streets and unleaded gasoline use should be promoted. Acknowledgments This project was supported by the Istanbul University Research Fund. The authors would like to thank for the assistance of the following people and association: Nurşen Toruş, Hüseyin Yılmazgüç, Sevim Soğancıoğlu, Nihal Kılıç, Nurşen Kılıç, Fürüzan Üstündağ, Fatma Büren, Fatoş Kıyak and Yeni Akatlar Lions Club.
[11]
[12] [13]
[14]
[15] [16]
[17] [18]
[19] [20]
[21]
References [22] [1] Goyers RA. Toxic effects of metals. In: Klaassen CD, Amdur MO, Doull J, editors. Casarett and Doull's toxicology: the basic science of poisons. 5th ed. New York: McGraw-Hills; 1996. pp. 691–736. [2] Mortada WI, Sobh MA, El-Defrawy MM, Farahat SE. Reference intervals of cadmium, lead and mercury in blood, urine, hair and nails among residents in Mansoura city, Nile Delta, Egypt. Environ Res, Sect A 2002;90:104–10. [3] Prased Ananda S. Clinical biochemical and nutritional aspects of trace elements. 150 fifth Avenue New York, NY 10011: Alan R. Liss. Inc; 1982. p. 513–9. [4] Haan MP, Gerson M, Zishka BA. Identification of children at risk for lead poisoning. An evaluation of routine pediatric blood screening in an HMOinsured population. Pediatrics 1996;97:79–83. [5] Schwartz J. Low level lead exposure and children's IQ: a meta-analysis and search for a threshold. Environ Res 1994;65:42–55. [6] WHO. Inorganic Lead. Environmental Health Criteria 165. World Health Organization Geneva; 1995. p. 25–31. [7] Committee on Environmental Hazards Committee on accident and poison prevention. Statement on childhood lead poisoning. Pediatrics 1987;79: 457–65. [8] Ryan D, Levy B, Levy BS, Pollack S, Walker B. Protecting children from lead poisoning and building healthy communities. Am J Public Health 1999;89:822–4. [9] Tuthill RW. Hair lead levels related to children's classroom attentiondeficit behavior. Arch Environ Health 1996;1:214–21. [10] Chlopicha J, Zadrodzki P, Zachwieja Z, Krooeniak M, Flota M. Use of
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
pattern recognition methods in the interpretation of heavy metal content (lead and cadmium) in children's scalp hair. Analyst 1995;120:943–6. Takao W, Okujou I, Haruo N, Hiroshi I, Masayuki I. Correlation of cadmium, copper, manganese and zinc levels in the urine of people in nonpolluted areas. J Toxicol Environ Health 1991;33:263–8. Nowak B. Contents and relationship of elements in human hair for a nonindustrialised population in Poland. Sci Total Environ 1998;209:56–68. Liu XJ, Arisawa K, Nakano A, Saito H, Takahashi T, Kosaka A. Significance of cadmium concentrations in blood and hair as an indicator of dose 15 years after the reduction of environmental exposure of cadmium. Toxicol Lett 2001;123:135–41. Sen J, Das Chauduri AB. Brief communication of washing method of hair samples for trace element analysis in environmental studies. Am J Phys Anthropol 2001;115:289–91. Kapito L, Byers RK, Shwachman H. Lead in hair of children with chronic lead poisoning. N Engl J Med 1967;276:949–53. Schumacher M, Belles M, Rico A, Domingo JL, Corbella J. Impact of reduction of lead in gasoline on the blood and hair lead levels in population of Tarragona province, Spain, 1990–1995. Sci Total Environ 1996; 184:203–9. Neyzi O, Alp H. Characteristics of Puberty I. Istanb Med Fac J 1977;40:11. Zheng W. Blood lead screening in China; organisation, quality assurance and results. In: Proceedings of the International Conference on Lead Poisoning: Banglore, India, 8–10 February 1999, Banglore. The George Foundation; 1999. p. 119–22. Weaver VM. Environmental tobacco smoke exposure in inner-city children. Cancer Epidemiol 1996;5:135–7. Weyermann M, Brenner H. Alcohol Consumption an smoking habits determinants of blood lead levels in a national population sample from Germany. Arch Environ Health 1997;52:233–9. Watanabe T, Kasahara M, Nakatsuka H, Ikeda M. Cadmium and lead contents of cigarettes in various areas of the world. Sci Total Environ 1987; 66:29–37. Nnorom IC, Asıbanjo O, Ojı-Nnorom CG. Cadmium determination in cigarettes available in Nigeria. Afr J Biotechnol 2005:1128–32. Wolfsperger M, Hauser WM, Gossler W, Schlagenhaufen C. Heavy metals in human hair from Austria and Italy: influence of sex and smoking habits. Sci Total Environ 1994;156:235–42. Lekouch N, Sedki A, Bouhouch S, Nejmeddine A, Pineau A, Pihan JC. Trace element in children's hair, as related exposure in wastewater spreading field of Marrakesh (Morocco). Sci Total Environ 1999;243/ 244:323–8. Telisman S, Jurasovic J, Pizent A, Cvitkovic P. Cadmium in the blood and seminal fluid of non-occupationally exposed adult male subjects with regard to smoking habits. Int Arch Occup Environ Health 1997;70:243–8. Satarug S, Moore MR. Adverse health effects of chronic exposure to lowlevel cadmium in foodstuffs and cigarette smoke. Environ Health Perspect 2004;10:1099–103. Baghurst P, Tong SL, MCMichael AS, Robertson EF, Wigg NR, Vimpani GV. Determinants of blood lead concentrations to age 5 years in a birth cohort study of children living in the lead smelting city of Port Pirie and surrounding areas. Arch Environ Health 1992;47:203–10. Willers S, Schutz A, Attewell R, Skerfving S. Relation between lead and cadmium in blood and the involuntary smoking of children. Scand J Work, Environ & Health 1998;14:385–9. Lyngbye T, Jorgenson PJ, Grendjean P, Hansen ON. Validity and interpretation of blood lead levels: a study of Danish school children. Scand J Clin Lab Invest 1990;50:441–9 [8; 14 :385–9]. Ozden TA, Kılıc A, Vehid HE, Toparlak D, Gokcay G, Saner G. Blood lead levels in school children. Indoor Built Environ 2004;13:149–54.
Elevated hair levels of cadmium and lead in school children exposed to smoking and in highways near schools Tülin Ayşe Özden a,⁎, Gülbin Gökçay a , Hayriye Vehid Ertem a , Özlem Durmaz Süoğlu a , Ayşe Kılıç a , Semra Sökücü b , Günay Saner a b
a Institute of Child Health, Istanbul University, Çapa 34093, Istanbul, Turkey Department of Child Health, Istanbul University, Istanbul Medical Faculty, Çapa 34093, Turkey
Received 9 June 2006; received in revised form 25 July 2006; accepted 27 July 2006 Available online 12 August 2006
Abstract Objectives: Heavy metal pollution has become a serious health concern in recent years. Cadmium (Cd) and Lead (Pb) are toxic heavy metals. This study was aimed to determine the risk factors for high cadmium and lead levels in school children. Design and methods: The scalp hair samples were obtained from 760 children at 13 schools in Istanbul. A questionnaire was prepared to gather information about demographic and socioeconomic characteristics of the children. Hair cadmium and lead concentrations were determined by atomic absorption spectrophotometer. Results: Household exposure to smoking and attending a school near to Main Streets were found to be the most important risk factors for the high hair cadmium and lead levels in our study. Conclusion: These findings support the public health recommendations that children should not have household exposure to smoking, schools should not be near to the main streets and unleaded gasoline use should be promoted. © 2006 The Canadian Society of Clinical Chemists. All rights reserved. Keywords: Toxic metals; Cadmium; Lead; Environmental exposure; School children; Hair analysis; Smoking
Introduction Heavy metal pollution has become a serious health concern in recent years. Cadmium (Cd) and lead (Pb) are toxic heavy metals. Continuous exposure to low levels of these toxic heavy metals may result in bioaccumulation and can cause a wide variety of biological effects on human beings depending upon the level and the duration of exposure [1,2]. Long-term, lowlevel exposure to cadmium will result in accumulation in liver and kidneys, the main storage organ to cadmium [3]. Several studies have suggested that even low levels of lead exposure may cause adverse impacts on cognitive functioning [4,5]. These metals can be found in the work place, drinking water, in food, consumer products, enamel utensils and traditional medicines [6,7].
⁎ Corresponding author. Fax: +90 212 631 39 97. E-mail address: [email protected] (T.A. Özden).
These metals enter the human body mainly after inhalation and also via gastrointestinal absorption. Inhalation is the second major means of cadmium and lead absorption for children [6– 9]. The strength of the problem depends on the body dimensions of the child. In addition, children absorb greater percentage of ingested lead than adults [9]. Many authors have reported that human hair is a good indicator of environmental pollution. Therefore using scalp hair as an indicator of the environmental exposure to several trace elements has become a common method [10–12]. However, there is no definite result about the significance of Cd in hair as an index of exposure [13]. With the increasing importance of these metals in clinical medicine, reference ranges of these metals in biological samples are needed as tools for diagnosis. However, trace element concentrations in biological samples are affected by environmental and geographical factors. Therefore, considerable variations can occur between specific subgroups of the populations [2].
0009-9120/$ - see front matter © 2006 The Canadian Society of Clinical Chemists. All rights reserved. doi:10.1016/j.clinbiochem.2006.07.006
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
The current study was carried out among school children in Istanbul, which is a big city with heavy traffic as well as some industrial emissions from the surrounding districts. The Table 1 Sociodemographic characteristics of children Variables
n
%
Gender Male Female
331 429
43.6 56.4
Child employment status Yes No Unknown
16 738 6
2.1 97.1 0.8
Maternal education Illiterate Primary Secondary High school University
40 312 144 192 72
5.3 41.1 18.9 25.3 9.4
Paternal education Illiterate Primary Secondary High school University Unknown
12 203 198 207 138 2
1.6 26.7 26.1 27.2 18.2 0.2
Maternal working status Yes No Unknown
190 568 2
25.0 74.7 0.3
Paternal working status Unemployed Laborers–civil servant Private business Unknown
20 310 419 11
2.6 40.8 55.1 1.5
Insurance Yes No Unknown
168 557 5
22.1 73.3 0.6
Socioeconomic status High middle Middle Low middle Low
306 153 194 107
40.3 20.1 25.5 14.1
Home ownership Yes No
239 521
31.4 68.6
Heating style Coal–stove Furnace Natural gas Unknown
270 202 287 1
35.5 26.6 37.8 0.1
Mother smoking Yes No
337 423
44.3 55.7 (continued on next page)
53
Table 1 (continued) Variables
n
%
Number of smokers at home 0 1 2 ≥3
173 289 237 61
22.8 38.0 31.2 8.0
challenge against toxic element exposure varies from country to country. However, the required steps to eliminate the effects are now apparent [8]. The aim of this study was to asses the concentration of cadmium and lead in hair and to determine the risk factors for high lead and cadmium levels in school children in Istanbul. Material and methods Study population The approval of the Medical School Ethic Committee was obtained at the beginning of the study. The permission of Istanbul Education Directorate was sought before receiving the consents of both the school administration and the parents. The study was conducted in 13 elementary schools in Istanbul. The schools were chosen according to the distance from the main streets in the both sides of Istanbul. A questionnaire was sent to 1500 students at 5th and 6th grades, whose ages were ranging between 11 and 13 years. Of all these students' families 894 have accepted to give hair samples. We were able to take hair samples from 760 children who were present during the study day. Since 134 boys had very short hair cut, no hair sample could be obtained from these children. Out of 13 schools, 7 were close to the main streets. A questionnaire was prepared to gather information about demographic and socioeconomic characteristics of the families and the smoking status of the household people. Analytical methods and instrumentation Hair samples were cut in 0.5 cm using stainless steel scissors to avoid contamination. Hair samples of the children were collected from suboccipital area of the head in immediate proximity to the scalp and stored in plastic bags. The proximal hair length was 2–2.5 cm and the proximal weight was around 100–200 mg. Duplicated hair samples of approximately 50– 200 mg were washed sequentially three times in hexane, pure analyze analytical grade ethanol and fresh bidistilled water. They were dried at 75°C in a vacuum oven for a night, 20– 100 mg weighted in polyethylene vial. Hair was digested using perchloric acid and nitric acid. Digestion was made between 65 and 75°C [9,14,15]. Ashed samples were then dissolved in 1 mL of 0.5 M nitric acid and 10 μl aliquots were injected into graphite furnace by an auto sampler. The concentration of lead and cadmium in hair was determined by double beam atomic absorption spectrophotometer Varian spectraAA-200 equipped with GTA-100 [16].
54
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
Statistical analyses
Table 2 Determinants of hair cadmium levels
Hair cadmium and lead levels of children were not normally distributed therefore the distance of the schools to the main street, ownership of the house, socioeconomic status, mother smoking habits, gender, insurance status, working status of the mother and the father, the number of smokers at home, heating style were grouped with respect to the median hair cadmium and lead levels. Furthermore, these groups were analyzed with Pearson Chi-square test. Logistic regression analyses were used to determine the effects of the above parameters on the hair cadmium level and hair lead level medians. Spearman correlation analysis was carried out between hair cadmium and lead levels. The classification of socioeconomic status of the children was made according to Neyzi criteria [17].
Variables
Results Of the 760 students whose scalp hair samples were obtained and evaluated for analysis 43.6% were male and 55% were from the schools close to the main streets. Sociodemographic characteristics of the students are shown in Table 1. This socioeconomic classification was made according to the education levels of the parents and the occupation of the fathers. The percentage of children from high middle, middle, low middle and low socioeconomic levels of children were 40.3%, 20.1%, 25.5% and 14.1% respectively (Table 1). Of all mothers, 5.3% were illiterate, 60% primary or secondary school graduates and 25% working. Of all fathers 1.6% were illiterate, 52.8% the graduates of primary or secondary school, 40.8% laborers or civil servants and 55.1% had private business. Of all mothers 44.3% were smokers. Of all children, 22.8% had no smoker at home and 2.1% were working (Table 1). The values of hair cadmium and lead levels were not normally distributed. The mean values of the hair cadmium and lead levels of all children were 53.38 ± 44.13 μg/g, 2.41 ± 2.22 μg/g, respectively. Median values (cut off) of hair cadmium and lead levels are 40 ng/g and 1.9 μg/g, respectively. There was a weak correlation between hair Cd and Pb levels (rs = 0.44). Hair cadmium and lead levels were grouped as either above or equal and below median values for the analyses. As the number of smokers at home increased, the proportion of children with hair cadmium and lead levels above the median also increased. These differences were found to be statistically significant (Tables 2, 3). The distance of the school to the main street and socioeconomic status had statistically significant impact on the hair lead and cadmium levels (Tables 2, 3). The logistic regression analyses have demonstrated that the distance of school to the main street (ORCd: 0. 676; 0.488– 0.936 95% CI), existence of a smoker at home had statistically significant impacts on the hair cadmium levels (Table 4). According to the results of logistic regression analysis, boys had higher hair cadmium levels and students from the schools far from the main street had lower hair cadmium
Hair cadmium levels <40.0 ng/g
≥40.0 ng/g
N
%
N
%
161 216
48.6 50.3
170 213
51.4 49.7
Pearson χ2
P
df
0.218
0.6
1
Comparative distance of school to main street Far 184 53.8 158 46.2 Close 193 46.2 225 53.8
4.379
0.036
1
Mother smoking Yes No
Gender Male Female
147 230
43.6 54.4
190 193
56.4 45.6
8.676
0.003
1
Maternal employment Yes 83 No 293
43.7 51.6
107 275
56.3 48.4
3.555
0.059
1
Child employment Yes 12 No 363
75.0 49.2
4 374
25.0 50.8
4.174
0.041
1
Insurance Yes No
75 283
44.6 50.8
93 274
55.4 49.2
1.963
0.161
1
Home ownership Yes No
123 254
51.5 48.8
116 267
48.5 51.2
0.482
0.487
1
Number of smokers at home 0 86 49.7 1 146 50.5 2 126 53.2 ≥3 19 31.1
87 143 111 42
50.3 49.5 46.8 68.9
9.612
0.022
3
Heating style Coal–stove Furnace Natural gas
49.6 51.5 48.4
136 98 148
50.4 48.5 51.6
0.442
0.802
2
0.269
0.874
2
3.745
0.290
3
134 104 139
Paternal working status Unemployed 11 Laborers–civil 152 servant Private business 210
55.0 49.0
9 158
45.0 51.0
49.5
214
50.5
Socioeconomic status High middle 152 Middle 72 Low middle 106 Low 47
49.7 47.1 54.6 43.9
154 81 88 60
50.3 52.9 45.4 56.1
levels than the students from the schools near to the main street (Table 4). The logistic regression analyses showed that school distance to the main street, gender (ORpb: 1.558; 1.132–2.145 95%) and number of smokers at home (ORPb: 0. 229; 0.164–0.321 95% CI) had statistically significant impact on hair lead levels (Table 4).
T.A. Özden et al. / Clinical Biochemistry 40 (2007) 52–56
Discussion In this study cadmium and lead levels were analyzed in the scalp hair of school children to assess the extent of the burden of pollution in the body. School distance to the main street and presence of a smoker at home was found to be important factors. Schuhmacher et al. [16] showed that blood and hair lead levels decreased during the period 1990–1995 after reduced leaded Table 3 Determinants of hair lead levels Variables
Gender Male Female
Hair lead levels <1.9 μg/g
≥1.9 μg/g
n
%
n
%
146 234
44.1 54.5
185 195
55.9 45.5
Comparative distance of school to main street Far 268 64.1 150 35.9 Close 112 32.7 230 67.3
Pearson χ2
8.141
P
df
0.004
1
74.024
0.000
51.1 49.2
165 215
49.0 50.8
0.261
0.609
1
Maternal employment Yes No
97 282
51.1 49.6
93 286
48.9 50.4
0.112
0.737
1
Child employment Yes No
7 369
43.9 50.9
9 369
56.3 50.0
0.245
0.621
1
Insurance Yes No
81 279
48.2 50.1
87 278
51.8 49.9
0.182
0.670
1
Home ownership Yes No
125 255
52.3 48.9
114 266
47.7 51.1
0.739
0.390
1
Number of smokers at home 0 99 1 160 2 115 ≥3 6
57.2 55.6 48.5 9.8
74 129 122 55
42.8 44.6 51.5 90.2
46.505
0.000
3
Heating style Coal–stove Furnace Natural gas
119 108 152
44.1 53.5 53.0
151 94 135
55.9 46.5 47.0
5.769
0.056
2
Paternal working status Unemployed 11 Laborers–civil servant 141 Private business 224
55.0 45.5 52.8
9 169 200
45.0 54.5 47.2
4.082
0.130
2
Socioeconomic status High middle Middle Low middle Low
52.0 56.2 46.8 44.9
147 67 107 59
48.0 43.8 55.2 55.1
6.023
0.111
3
df: degrees of freedom.
Variables
For cadmium No smoker a Only one smoker a School far from the main street b For Lead Male School far from the main street b No smoker at home a Only one smoker at home a High–middle socioeconomic status c a b
Sig.
Exp. (β)
Confidence interval (95%) Lower limit
Upper limit
0.000 0.000 0.018
0.104 0.055 0.392 0.234 0.676 0.488
0.194 0.658 0.936
0.007 0.000 0.000 0.000 0.005
1.558 0.229 0.179 0.361 2.939
2.145 0.321 0.361 0.621 6.189
1.132 0.164 0.089 0.209 1.396
More than one smoker. School close on the main street. Low socioeconomic status.
1
172 208
a
Table 4 The effect of some variables on cadmium and lead levels according to logistic regression analysis
c
Mother smoking Yes No
159 86 87 48
a
55
gasoline consumption. Consumption of lead free petroleum in China leads to a decrease in blood lead levels in children [18]. Weaver [19] found that the blood lead levels of children living near the city centers were over 20 μg/mL. Tobacco contains varying amounts of cadmium and lead. A cigarette generally contains 1–2 μg cadmium, 0.6–17 μg lead [20–22]. About 10% of this amount may be inhaled. The use of insecticides with lead arsenate in tobacco fields may be the cause of high lead levels in tobacco plants. Apart from that, cadmium and lead in soil penetrate easily into tobacco plant while growing. These particles in air are accumulated on the leaves of tobacco plant and can also become a source of these toxic elements [19]. Cigarette smoking is an important predictor for heavy metal exposure, especially of cadmium and lead. Wolfsperger et al. [23] showed that smoker's hair lead levels were higher than non-smoker hair lead levels. In Morocco, Lekouch et al. showed that average hair lead levels were higher in children exposed to wastewater which contains lead than in the non-exposed children [24]. Some workers [25,26] indicated that smoking increased blood cadmium concentration. Weyerman and Brenner [20] found a dose response relationship between amounts of tobacco smoked each day and blood lead levels. Many studies showed that parents' smoking habits or passive smoking had an impact on children's blood lead levels [27–29]. Willers et al. [28] also found a dose response relationship between the amount of tobacco smoked by the mother and blood lead levels of children. In these students, we reported that presence of a smoker at home and living close the heavy traffic affect blood lead levels [30]. Our results are in agreement with these studies and showed similar findings for the hair lead levels of the student. These findings support that passive or active smoking contributes to Cd and Pb toxicity. Some investigators reported that blood Pb [2,21], hair Pb and Cd [12] levels in male were higher than in female. In our study hair Pb and Cd levels were found higher in male than in female and this difference was statistically significant for Cd levels.
56
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The reason for a higher hair Pb and Cd levels in males may be probably due to difference in out door activities, health behaviors, difference of urine excretion or kidney activities [2]. To our knowledge, this is the only study on hair Cd levels in school children. Our study had some limitations. The study sample was not selected randomly and cannot be generalized to the whole population but the students were from a heterogeneous group. We did not gather information about the smoking habits of fathers because fathers generally spend most of their time out of home and away from their children. This may be a limitation for our study but we do not think that we missed any additional findings about passive smoking. In conclusion, our findings support the public health recommendations that children should not have household exposure to smoking, schools should not be near to the main streets and unleaded gasoline use should be promoted. Acknowledgments This project was supported by the Istanbul University Research Fund. The authors would like to thank for the assistance of the following people and association: Nurşen Toruş, Hüseyin Yılmazgüç, Sevim Soğancıoğlu, Nihal Kılıç, Nurşen Kılıç, Fürüzan Üstündağ, Fatma Büren, Fatoş Kıyak and Yeni Akatlar Lions Club.
[11]
[12] [13]
[14]
[15] [16]
[17] [18]
[19] [20]
[21]
References [22] [1] Goyers RA. Toxic effects of metals. In: Klaassen CD, Amdur MO, Doull J, editors. Casarett and Doull's toxicology: the basic science of poisons. 5th ed. New York: McGraw-Hills; 1996. pp. 691–736. [2] Mortada WI, Sobh MA, El-Defrawy MM, Farahat SE. Reference intervals of cadmium, lead and mercury in blood, urine, hair and nails among residents in Mansoura city, Nile Delta, Egypt. Environ Res, Sect A 2002;90:104–10. [3] Prased Ananda S. Clinical biochemical and nutritional aspects of trace elements. 150 fifth Avenue New York, NY 10011: Alan R. Liss. Inc; 1982. p. 513–9. [4] Haan MP, Gerson M, Zishka BA. Identification of children at risk for lead poisoning. An evaluation of routine pediatric blood screening in an HMOinsured population. Pediatrics 1996;97:79–83. [5] Schwartz J. Low level lead exposure and children's IQ: a meta-analysis and search for a threshold. Environ Res 1994;65:42–55. [6] WHO. Inorganic Lead. Environmental Health Criteria 165. World Health Organization Geneva; 1995. p. 25–31. [7] Committee on Environmental Hazards Committee on accident and poison prevention. Statement on childhood lead poisoning. Pediatrics 1987;79: 457–65. [8] Ryan D, Levy B, Levy BS, Pollack S, Walker B. Protecting children from lead poisoning and building healthy communities. Am J Public Health 1999;89:822–4. [9] Tuthill RW. Hair lead levels related to children's classroom attentiondeficit behavior. Arch Environ Health 1996;1:214–21. [10] Chlopicha J, Zadrodzki P, Zachwieja Z, Krooeniak M, Flota M. Use of
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
pattern recognition methods in the interpretation of heavy metal content (lead and cadmium) in children's scalp hair. Analyst 1995;120:943–6. Takao W, Okujou I, Haruo N, Hiroshi I, Masayuki I. Correlation of cadmium, copper, manganese and zinc levels in the urine of people in nonpolluted areas. J Toxicol Environ Health 1991;33:263–8. Nowak B. Contents and relationship of elements in human hair for a nonindustrialised population in Poland. Sci Total Environ 1998;209:56–68. Liu XJ, Arisawa K, Nakano A, Saito H, Takahashi T, Kosaka A. Significance of cadmium concentrations in blood and hair as an indicator of dose 15 years after the reduction of environmental exposure of cadmium. Toxicol Lett 2001;123:135–41. Sen J, Das Chauduri AB. Brief communication of washing method of hair samples for trace element analysis in environmental studies. Am J Phys Anthropol 2001;115:289–91. Kapito L, Byers RK, Shwachman H. Lead in hair of children with chronic lead poisoning. N Engl J Med 1967;276:949–53. Schumacher M, Belles M, Rico A, Domingo JL, Corbella J. Impact of reduction of lead in gasoline on the blood and hair lead levels in population of Tarragona province, Spain, 1990–1995. Sci Total Environ 1996; 184:203–9. Neyzi O, Alp H. Characteristics of Puberty I. Istanb Med Fac J 1977;40:11. Zheng W. Blood lead screening in China; organisation, quality assurance and results. In: Proceedings of the International Conference on Lead Poisoning: Banglore, India, 8–10 February 1999, Banglore. The George Foundation; 1999. p. 119–22. Weaver VM. Environmental tobacco smoke exposure in inner-city children. Cancer Epidemiol 1996;5:135–7. Weyermann M, Brenner H. Alcohol Consumption an smoking habits determinants of blood lead levels in a national population sample from Germany. Arch Environ Health 1997;52:233–9. Watanabe T, Kasahara M, Nakatsuka H, Ikeda M. Cadmium and lead contents of cigarettes in various areas of the world. Sci Total Environ 1987; 66:29–37. Nnorom IC, Asıbanjo O, Ojı-Nnorom CG. Cadmium determination in cigarettes available in Nigeria. Afr J Biotechnol 2005:1128–32. Wolfsperger M, Hauser WM, Gossler W, Schlagenhaufen C. Heavy metals in human hair from Austria and Italy: influence of sex and smoking habits. Sci Total Environ 1994;156:235–42. Lekouch N, Sedki A, Bouhouch S, Nejmeddine A, Pineau A, Pihan JC. Trace element in children's hair, as related exposure in wastewater spreading field of Marrakesh (Morocco). Sci Total Environ 1999;243/ 244:323–8. Telisman S, Jurasovic J, Pizent A, Cvitkovic P. Cadmium in the blood and seminal fluid of non-occupationally exposed adult male subjects with regard to smoking habits. Int Arch Occup Environ Health 1997;70:243–8. Satarug S, Moore MR. Adverse health effects of chronic exposure to lowlevel cadmium in foodstuffs and cigarette smoke. Environ Health Perspect 2004;10:1099–103. Baghurst P, Tong SL, MCMichael AS, Robertson EF, Wigg NR, Vimpani GV. Determinants of blood lead concentrations to age 5 years in a birth cohort study of children living in the lead smelting city of Port Pirie and surrounding areas. Arch Environ Health 1992;47:203–10. Willers S, Schutz A, Attewell R, Skerfving S. Relation between lead and cadmium in blood and the involuntary smoking of children. Scand J Work, Environ & Health 1998;14:385–9. Lyngbye T, Jorgenson PJ, Grendjean P, Hansen ON. Validity and interpretation of blood lead levels: a study of Danish school children. Scand J Clin Lab Invest 1990;50:441–9 [8; 14 :385–9]. Ozden TA, Kılıc A, Vehid HE, Toparlak D, Gokcay G, Saner G. Blood lead levels in school children. Indoor Built Environ 2004;13:149–54.