Toenail Arsenic Concentrations Research Articles

Arsenic modifies the effect of folic acid in spina bifida prevention, a large hospital-based case-control study in Bangladesh

BackgroundSpina bifida, a developmental malformation of the spinal cord, is associated with high rates of mortality and disability. Although folic acid-based preventive strategies have been successful in reducing rates of spina bifida, some areas continue to be at higher risk because of chemical exposures. Bangladesh has high arsenic exposures through contaminated drinking water and high rates of spina bifida. This study examines the relationships between mother’s arsenic exposure, folic acid, and spina bifida risk in Bangladesh.MethodsWe conducted a hospital-based case-control study at the National Institute of Neurosciences & Hospital (NINS&H) in Dhaka, Bangladesh, between December 2016 and December 2022. Cases were infants under age one year with spina bifida and further classified by a neurosurgeon and imaging. Controls were drawn from children seen at NINS&H and nearby Dhaka Shishu Hospital. Mothers reported folic acid use during pregnancy, and we assessed folate status with serum assays. Arsenic exposure was estimated in drinking water using graphite furnace atomic absorption spectrophotometry (GF-AAS) and in toenails using inductively coupled plasma mass spectrometry (ICP-MS). We used logistic regression to examine the associations between arsenic and spina bifida. We used stratified models to examine the associations between folic acid and spina bifida at different levels of arsenic exposure.ResultsWe evaluated data from 294 cases of spina bifida and 163 controls. We did not find a main effect of mother’s arsenic exposure on spina bifida risk. However, in stratified analyses, folic acid use was associated with lower odds of spina bifida (adjusted odds ratio [OR]: 0.50, 95% confidence interval [CI]: 0.25-1.00, p = 0.05) among women with toenail arsenic concentrations below the median value of 0.46 µg/g, and no association was seen among mothers with toenail arsenic concentrations higher than 0.46 µg/g (adjusted OR: 1.09, 95% CI: 0.52–2.29, p = 0.82).ConclusionsMother’s arsenic exposure modified the protective association of folic acid with spina bifida. Increased surveillance and additional preventive strategies, such as folic acid fortification and reduction of arsenic, are needed in areas of high arsenic exposure.

Increased arsenic levels in both environmental measurements and biomonitoring results are associated with elevated risk of spina bifida

BACKGROUND AND AIM: Arsenic is associated with multiple adverse reproductive outcomes, and previous studies suggested higher risk of neural tube defects among mothers exposed to higher concentration of well water arsenic in Bangladesh. We further examine the association using water arsenic as proxy for external exposure and toenail as biomarkers for internal dose. METHODS: Parental toenail and water arsenic concentrations were examined in a case-control study in National Institute of Neurosciences & Hospital, Dhaka, Bangladesh. The associations between log-transformed and percentile arsenic concentrations and physician-diagnosed spina bifida were evaluated with logistic regression and cluster analysis, adjusted for maternal age, maternal BMI, parity, educational level, folic acid use and second-hand smoke exposure during pregnancy and weighted by self-reported dietary patterns. RESULTS:Median concentration for water, maternal and paternal arsenic are 2.0 ppb, 0.4 and 0.5 microgram per gram toenail among 280 included child-parent trios (156 with spina bifida) with complete exposure data. We observed associations between highest quartile maternal arsenic levels, higher than 10 ppb arsenic in water and spina bifida risk for their children after weighted for diet (Adjusted OR for water arsenic=1.49, 95% CI=1.00-2.06; adjusted OR for maternal arsenic=1.57, 95% CI=1.10-2.24), and higher composite exposure in both hierarchical clustering and k-means clustering were also associated with increased risk after weighting. Effect heterogeneity was observed between different folic acid supplement conditions, in which dose-response was attenuated for both water and paternal concentrations. CONCLUSIONS:Prenatal inorganic arsenic exposure was associated with elevated risk of spina bifida in Bangladesh, and joint parental exposure is associated with a higher risk. Investigations and interventions to mitigate arsenic exposure during for pregnant women are warranted. KEYWORDS: Heavy metals, birth outcomes, children's environmental health

Low- and moderate- levels of arsenic exposure in young adulthood and incidence of chronic kidney disease: Findings from the CARDIA Trace Element Study

BackgroundIt is unclear whether arsenic exerts adverse health effects on the kidney at low- and moderate- levels of exposure. We prospectively examined toenail arsenic concentrations measured during young adulthood in relation to incidence of chronic kidney disease (CKD) in midlife. MethodsA total of 3768 participants (53 % female and 48 % blacks) in the Coronary Artery Risk Development in Young Adults (CARDIA) study were included. Arsenic concentration in toenail clippings was assessed by using inductively coupled plasma mass spectrometry at CARDIA exam year 2. Incident CKD was identified if having estimated glomerular filtration rate <60 mL/min per 1.73 m² or albuminuria >30 mg/g. The association between toenail arsenic levels and CKD incidence over a mean of 24 years of follow-up was examined using multivariable-adjusted Cox proportional hazards models. ResultsAfter controlling for potential confounders, including demographics, socioeconomics, lifestyle factors, clinical measurements of blood pressure, lipids, and glucose, and medical history, arsenic exposure measured in toenails was not associated with CKD incidence (quintile 5 versus quintile 1: hazard ratio = 1.04, 95 % confidence interval = 0.78–1.40, P for trend = 0.38). ConclusionThis longitudinal study does not support the hypothesis that low- and moderate- levels of arsenic exposure are associated with elevated incidence of CKD in the US general population. Further studies are need to investigate species of arsenic biomarkers in relation to nephrotoxicity.

Prenatal arsenic exposure, child marriage, and pregnancy weight gain: Associations with preterm birth in Bangladesh

BackgroundPreterm birth is a disease of multifactorial etiologies that has environmental, social, and maternal health components. Individual studies have shown that exposure to arsenic contaminated drinking water, child marriage, and low maternal weight gain during pregnancy contribute to preterm birth. These factors are highly prevalent and often co-exist in Bangladesh, a country in South Asia with one of the world's highest prevalences of preterm birth. ObjectiveTo evaluate the individual and interactive effects of prenatal arsenic exposure, child marriage, and pregnancy weight gain on preterm birth in a prospective birth cohort in Bangladesh. MethodsDuring 2008–2011, we recruited 1613 pregnant women aged ≥18years at ≤16weeks of gestation and followed them until 1-month post-partum. We measured total arsenic in drinking water (n=1184) and in maternal toenails (n=1115) collected at enrollment and ≤1-month post-partum, respectively using inductively coupled plasma mass spectrometry. Child marriage (<18years old) was defined using self-report, and 2nd and 3rd trimester pregnancy weight gain was calculated using monthly records. Gestational age was determined at enrollment by ultrasound. ResultsIn multivariate adjusted Poisson regression models, the risk ratios (RR) for preterm birth were 1.12 (95% CI: 1.07–1.18) for a unit change in natural log water arsenic exposure, 2.28 (95% CI: 1.76–2.95) for child marriage, and 0.64 (95% CI: 0.42–0.97) for a pound per week increase in maternal weight during the 2nd and 3rd trimesters. In stratified analysis by child marriage, pregnancy weight gain was inversely associated with preterm birth among women with a history of child marriage (RR=0.58; 95% CI: 0.37–0.92), but not among women with no history of child marriage (RR=0.86; 95% CI: 0.37–2.01). Mediation analysis revealed that both arsenic exposure and child marriage had small but significant associations with preterm birth via lowering pregnancy weight gain. Similar associations were observed when arsenic exposure was assessed using maternal toenail arsenic concentrations. ConclusionsReducing arsenic exposure and ending child marriage could reduce the risk of preterm birth in Bangladesh. Furthermore, enhancing nutritional support to ensure adequate weight gain during pregnancy may provide additional benefits especially for women with a history of child marriage.

Associations between Diet and Toenail Arsenic Concentration among Pregnant Women in Bangladesh: A Prospective Study.

This prospective study evaluated the relationship between long-term dietary habits and total arsenic (As) concentration in toenail clippings in a cohort of 1616 pregnant women in the Bangladeshi administrative regions of Sirajdikhan and Pabna Sadar. Diet was assessed at Gestation Week 28 and at Postpartum Month 1, using a locally-validated dish-based semi-quantitative food-frequency questionnaire. Toenail As concentration was analyzed by microwave-assisted acid digestion and inductively coupled plasma mass spectrometry. Associations between natural log-transformed consumption of individual food items and temporally matched natural log-transformed toenail As concentration were quantified using general linear models that accounted for As concentration in the primary drinking water source and other potential confounders. The analysis was stratified by As in drinking water (≤50 μg/L versus >50 μg/L) and the time of dietary assessment (Gestation Week 28 versus Postpartum Week 1). Interestingly, toenail As was not significantly associated with consumption of plain rice as hypothesized. However, toenail As was positively associated with consumption of several vegetable, fish and meat items and was negatively associated with consumption of rice, cereal, fruits, and milk based food items. Further studies in pregnant women are needed to compare As metabolism at different levels of As exposure and the interaction between dietary composition and As absorption.

Estimating Effects of Arsenic Exposure During Pregnancy on Perinatal Outcomes in a Bangladeshi Cohort.

The relationship between arsenic and birth weight is not well understood. The objective was to evaluate the causal relationship between prenatal arsenic exposure and birth weight considering the potential mediation effects of gestational age and maternal weight gain during pregnancy using structural equation models. A prospectively enrolled cohort of pregnant women was recruited in Bangladesh from 2008 to 2011. Arsenic was measured in personal drinking water at the time of enrollment (gestational age <16 weeks, N = 1,140) and in toenails collected ≤1 month postpartum (N = 624) using inductively coupled plasma mass spectrometry. Structural equation models estimated the direct and indirect effects of arsenic on birth weight with gestational age and maternal weight gain considered as mediating variables. Every unit increase in natural log water arsenic was indirectly associated with decreased birth weight (β = -19.17 g, 95% confidence interval [CI]: -24.64, -13.69) after adjusting for other risk factors. This association was mediated entirely through gestational age (β = -17.37 g, 95% CI: -22.77, -11.98) and maternal weight gain during pregnancy (β = -1.80 g, 95% CI: -3.72, 0.13). When exposure was modeled using toenail arsenic concentrations, similar results were observed. Every increase in natural log toenail arsenic was indirectly associated with decreased birth weight (β = -15.72 g, 95% CI: -24.52, -6.91) which was mediated through gestational age (β = -13.59 g, 95% CI: -22.10, -5.07) and maternal weight gain during pregnancy (β = -2.13 g, 95% CI: -5.24, 0.96). Arsenic exposure during pregnancy was associated with lower birth weight. The effect of arsenic on birth weight appears to be mediated mainly through decreasing gestational age and to a lesser extent by lower maternal weight gain during pregnancy.

Risk of death from cardiovascular disease associated with low-level arsenic exposure among long-term smokers in a US population-based study

High levels of arsenic exposure have been associated with increases in cardiovascular disease risk. However, studies of arsenic's effects at lower exposure levels are limited and few prospective studies exist in the United States using long-term arsenic exposure biomarkers. We conducted a prospective analysis of the association between toenail arsenic and cardiovascular disease mortality using longitudinal data collected on 3939 participants in the New Hampshire Skin Cancer Study. Using Cox proportional hazard models adjusted for potential confounders, we estimated hazard ratios and 95% confidence intervals associated with the risk of death from any cardiovascular disease, ischemic heart disease, and stroke, in relation to natural-log transformed toenail arsenic concentrations. In this US population, although we observed no overall association, arsenic exposure measured from toenail clipping samples was related to an increased risk of ischemic heart disease mortality among long-term smokers (as reported at baseline), with increased hazard ratios among individuals with ≥31 total smoking years (HR: 1.52, 95% CI: 1.02, 2.27), ≥ 30 pack-years (HR: 1.66, 95% CI: 1.12, 2.45), and among current smokers (HR: 1.69, 95% CI: 1.04, 2.75). These results are consistent with evidence from more highly exposed populations suggesting a synergistic relationship between arsenic exposure and smoking on health outcomes and support a role for lower-level arsenic exposure in ischemic heart disease mortality.

Infant toenails as a biomarker of in utero arsenic exposure.

A growing body of evidence suggests that in utero and early-life exposure to arsenic may have detrimental effects on children, even at the low to moderate levels common in the United States and elsewhere. In a sample of 170 mother-infant pairs from New Hampshire, we determined infant exposure to in utero arsenic by evaluating infant toenails as a biomarker using inductively coupled plasma mass spectrometry. Infant toenail arsenic concentration correlated with maternal postpartum toenail concentrations (Spearman's correlation coefficient 0.34). In adjusted linear models, a doubling of maternal toenail arsenic concentration was associated with a 53.8% increase in infant toenail arsenic concentration as compared with 20.4% for a doubling of maternal urine arsenic concentration. In a structural equation model, a doubling of the latent variable integrating maternal toenail and urine arsenic concentrations was associated with a 67.5% increase in infant toenail arsenic concentration. A similar correlation between infant and maternal postpartum toenail concentrations was observed in a validation cohort of 130 mother-infant pairs from Rhode Island. In utero exposure to arsenic occurs through maternal water and dietary sources, and infant toenails appear to be a reliable biomarker for estimating arsenic exposure during the critical window of gestation.

Geostatistical modelling of arsenic in drinking water wells and related toenail arsenic concentrations across Nova Scotia, Canada

Arsenic is a naturally occurring class 1 human carcinogen that is widespread in private drinking water wells throughout the province of Nova Scotia in Canada. In this paper we explore the spatial variation in toenail arsenic concentrations (arsenic body burden) in Nova Scotia. We describe the regional distribution of arsenic concentrations in private well water supplies in the province, and evaluate the geological and environmental features associated with higher levels of arsenic in well water. We develop geostatistical process models to predict high toenail arsenic concentrations and high well water arsenic concentrations, which have utility for studies where no direct measurements of arsenic body burden or arsenic exposure are available. 892 men and women who participated in the Atlantic Partnership for Tomorrow's Health Project provided both drinking water and toenail clipping samples. Information on socio-demographic, lifestyle and health factors was obtained with a set of standardized questionnaires. Anthropometric indices and arsenic concentrations in drinking water and toenails were measured. In addition, data on arsenic concentrations in 10,498 private wells were provided by the Nova Scotia Department of Environment. We utilised stepwise multivariable logistic regression modelling to develop separate statistical models to: a) predict high toenail arsenic concentrations (defined as toenail arsenic levels ≥0.12μgg−1) and b) predict high well water arsenic concentrations (defined as well water arsenic levels ≥5.0μgL−1). We found that the geological and environmental information that predicted well water arsenic concentrations can also be used to accurately predict toenail arsenic concentrations. We conclude that geological and environmental factors contributing to arsenic contamination in well water are the major contributing influences on arsenic body burden among Nova Scotia residents. Further studies are warranted to assess appropriate intervention strategies for reducing arsenic body burden among human populations.

Relationship between drinking water and toenail arsenic concentrations among a cohort of Nova Scotians

Consumption of arsenic-contaminated drinking water is associated with increased cancer risk. The relationship between arsenic body burden, such as concentrations in human toenails, and arsenic in drinking water is not fully understood. We evaluated the relationship between arsenic concentrations in drinking water and toenail clippings among a cohort of Nova Scotians. A total of 960 men and women aged 35 to 69 years provided home drinking water and toenail clipping samples. Information on water source and treatment use and covariables was collected through questionnaires. Arsenic concentrations in drinking water and toenail clippings and anthropometric indices were measured. Private drilled water wells had higher arsenic concentrations compared with other dug wells and municipal drinking water sources (P<0.001). Among participants with drinking water arsenic levels ≥1 μg/l, there was a significant relationship between drinking water and toenail arsenic concentrations (r=0.46, P<0.0001). Given similar levels of arsenic exposure from drinking water, obese individuals had significantly lower concentrations of arsenic in toenails compared with those with a normal weight. Private drilled water wells were an important source of arsenic exposure in the study population. Body weight modifies the relationship between drinking water arsenic exposure and toenail arsenic concentrations.

Diet and toenail arsenic concentrations in a New Hampshire population with arsenic-containing water.

BackgroundLimited data exist on the contribution of dietary sources of arsenic to an individual’s total exposure, particularly in populations with exposure via drinking water. Here, the association between diet and toenail arsenic concentrations (a long-term biomarker of exposure) was evaluated for individuals with measured household tap water arsenic. Foods known to be high in arsenic, including rice and seafood, were of particular interest.MethodsAssociations between toenail arsenic and consumption of 120 individual diet items were quantified using general linear models that also accounted for household tap water arsenic and potentially confounding factors (e.g., age, caloric intake, sex, smoking) (n = 852). As part of the analysis, we assessed whether associations between log-transformed toenail arsenic and each diet item differed between subjects with household drinking water arsenic concentrations <1 μg/L versus ≥1 μg/L.ResultsAs expected, toenail arsenic concentrations increased with household water arsenic concentrations. Among the foods known to be high in arsenic, no clear relationship between toenail arsenic and rice consumption was detected, but there was a positive association with consumption of dark meat fish, a category that includes tuna steaks, mackerel, salmon, sardines, bluefish, and swordfish. Positive associations between toenail arsenic and consumption of white wine, beer, and Brussels sprouts were also observed; these and most other associations were not modified by exposure via water. However, consumption of two foods cooked in water, beans/lentils and cooked oatmeal, was more strongly related to toenail arsenic among those with arsenic-containing drinking water (≥1 μg/L).ConclusionsThis study suggests that diet can be an important contributor to total arsenic exposure in U.S. populations regardless of arsenic concentrations in drinking water. Thus, dietary exposure to arsenic in the US warrants consideration as a potential health risk.

Diet and toenail arsenic concentrations in a New Hampshire population with arsenic-containing water

Diet and toenail arsenic concentrations in a New Hampshire population with arsenic-containing water

Ongoing soil arsenic exposure of children living in an historical gold mining area in regional Victoria, Australia: Identifying risk factors associated with uptake

Elevated levels of arsenic have been observed in some mine wastes and soils around historical gold mining areas in regional Victoria, Australia. Arsenic uptake from soil by children living in these areas has been demonstrated using toenail arsenic concentration as a biomarker, with evidence of some systemic absorption associated with periodic exposures. We conducted a follow-up study to ascertain if toenail arsenic concentrations, and risk factors for exposure, had changed over a five year period in an historical gold mining region in western regional Victoria, Australia. Residential soil samples (N=14) and toenail clippings (N=24) were analyzed for total arsenic using instrumental neutron activation analysis, including 19 toenail clippings samples that were obtained from the same study cohort in 2006. Toenail arsenic concentrations in 2011 (geometric mean, 0.171μg/g; range, 0.030–0.540μg/g) were significantly lower than those in 2006 (geometric mean, 0.464μg/g; range, 0.150–2.10μg/g; p<0.001). However, toenail arsenic concentrations were again correlated with soil arsenic levels (Spearman’s rho=0.630; p=0.001). Spending time outdoors more often and for longer periods correlates with increased arsenic uptake (p<0.05). Mining-influenced residential soils represent a long-term continuing source for potential arsenic exposure for children living in this historical mining region.

Associations between toenail arsenic concentration and dietary factors in a New Hampshire population.

BackgroundDietary factors such as folate, vitamin B12, protein, and methionine are important for the excretion of arsenic via one-carbon metabolism in undernourished populations exposed to high levels of arsenic via drinking water. However, the effects of dietary factors on toenail arsenic concentrations in well-nourished populations exposed to relatively low levels of water arsenic are unknown.MethodsAs part of a population-based case–control study of skin and bladder cancer from the USA, we evaluated relationships between consumption of dietary factors and arsenic concentrations in toenail clippings. Consumption of each dietary factor was determined from a validated food frequency questionnaire. We used general linear models to examine the associations between toenail arsenic and each dietary factor, taking into account potentially confounding effects.ResultsAs expected, we found an inverse association between ln-transformed toenail arsenic and consumption of vitamin B12 (excluding supplements) and animal protein. Unexpectedly, there were also inverse associations with numerous dietary lipids (e.g., total fat, total animal fat, total vegetable fat, total monounsaturated fat, total polyunsaturated fat, and total saturated fat). Finally, increased toenail arsenic concentrations were associated with increased consumption of long chain n-3 fatty acids.ConclusionIn a relatively well-nourished population exposed to relatively low levels of arsenic via water, consumption of certain dietary lipids may decrease toenail arsenic concentration, while long chain n-3 fatty acids may increase toenail arsenic concentration, possibly due to their association with arsenolipids in fish tissue.

Associations between toenail arsenic concentration and dietary factors in a New Hampshire population

Associations between toenail arsenic concentration and dietary factors in a New Hampshire population

A case-control study of polymorphisms in xenobiotic and arsenic metabolism genes and arsenic-related bladder cancer in New Hampshire

Arsenic is associated with bladder cancer risk even at low exposure levels. Genetic variation in enzymes involved in xenobiotic and arsenic metabolism may modulate individual susceptibility to arsenic-related bladder cancer. Through a population-based case-control study in NH (832 cases and 1191 controls), we investigated gene-environment interactions between arsenic metabolic gene polymorphisms and arsenic exposure in relation to bladder cancer risk. Toenail arsenic concentrations were used to classify subjects into low and high exposure groups. Single nucleotide polymorphisms (SNPs) in GSTP1, GSTO2, GSTZ1, AQP3, AS3MT and the deletion status of GSTM1 and GSTT1 were determined. We found evidence of genotype-arsenic interactions in the high exposure group; GSTP1 Ile105Val homozygous individuals had an odds ratio (OR) of 5.4 [95% confidence interval (CI): 1.5–20.2; P for interaction=0.03] and AQP3 Phe130Phe carriers had an OR=2.2 (95% CI: 0.8–6.1; P for interaction=0.10). Bladder cancer risk overall was associated with GSTO2 Asn142Asp (homozygous; OR=1.4; 95% CI: 1.0–1.9; P for trend=0.06) and GSTZ1 Glu32Lys (homozygous; OR=1.3; 95% CI: 0.9–1.8; P for trend=0.06). Our findings suggest that susceptibility to bladder cancer may relate to variation in genes involved in arsenic metabolism and oxidative stress response and potential gene-environment interactions requiring confirmation in other populations.

EXPOSURE TO METALS AND GENE-SPECIFIC METHYLATION IN COMMUNITY-DWELLING ELDERLY MEN

Background and Aims: Methylation changes in promoter regions of genes have been linked to gene expression changes and subsequent human disease. Heavy metals are known to trigger oxidative stress, changes in immune response, and inflammation throughout the body. DNA methylation is a potential pathway through which heavy metals exert their toxicity. We aimed to evaluate the association between exposure to arsenic, cadmium, mercury, manganese and lead and DNA methylation in nine different genes related to inflammation, immune response, and endothelial function in a population of environmentally exposed elderly men. Methods: Our study population was 773 participants from the Normative Aging Study cohort in Boston, USA, with repeated visits between 1999 and 2009. Our associations of interest were explored in a minimum of 423 and a maximum of 611 participants depending on the availability of the exposure and outcome measurements. We measured the concentration of metals in toenails (in mcg/gr) while DNA methylation (in % of 5methyl cytosine) in promoter regions of the IL6, IFN-gamma, iNOS, ICAM, CRAT, OGG, TLR2, F3 and GCR genes was measured in blood leukocytes. The toenail metal concentrations were natural logarithm-transformed. We used multivariable linear mixed effects models to evaluate the associations of interest. Results: Toenail arsenic and manganese concentrations were negatively associated with the iNOS gene methylation [b=-0.2, 95%CI: -0.3 to -0.1 for ten percent increase in toenail arsenic; b= -0.1, 95%CI: -0.1 to -0.01 for ten percent increase in toenail manganese). We did not find any statistically significant associations between the other metals and gene-specific methylation. Conclusions: Both arsenic and manganese concentrations were associated with decreased iNOS methylation which can potentially lead to increased iNOS gene function and subsequent increased nitrogen oxide production, a process involved in inflammation. Our results indicate that heavy metal exposures may exert their effects through epigenetic mechanisms.

TOENAIL ARSENIC CONCENTRATIONS AMONG RESIDENTS OF A COAL MINING AREA OF THE APPALACHIAN MOUNTAINS OF THE UNITED STATES: A PILOT STUDY.

Background and Aims: Arsenic is an established lung carcinogen. Lung cancer rates in the Appalachian region of Kentucky are about twice the national rates in the U.S.A. The high rates of smoking in the area do not explain all the elevation in lung cancer risk. This area is also characterized by extensive coal mining activity. This pilot study explored a comparison of toenail arsenic concentrations in Appalachian Kentucky and another distant region of the state. Methods:Toenail samples were collected for a population - based case-control study in Kentucky. A sub-group of the samples were selected and analyzed for trace elements, based on location of the study participants, who were included if they lived in the East Kentucky Coal counties in Appalachian Kentucky, or in the largest urban center of Jefferson County. For the assessment of population-based exposure, only the controls of the original study were included. Total elemental analyses were performed using inductively-coupled plasma-mass spectrometry. There were a considerable number of samples with arsenic concentrations below the method detection limit, due in part to inadequate sample mass. Therefore, a reverse Kaplan-Meier method was used for the statistical analysis of the left-censored data. Results: A total of 88 toenail samples from Appalachian Kentucky and 155 from Jefferson County were analyzed for arsenic concentrations. The reverse Kaplan-Meier estimation indicated that the arsenic concentrations in the Appalachian counties were significantly higher than in Jefferson (75th and 90th percentiles were 0.13 vs. 0.03 and 0.29 vs. 0.04 ug/g, respectively). Conclusions: The results of this study suggest that residents of the selected Appalachian Kentucky counties with high coal mining activity have higher exposure to arsenic than those in an urban, non-coal mining region of the same state. However, further studies are needed to elucidate the source of the arsenic exposure.

Age and Gender Modifies Dose-response Relationship Between Tubewell Arsenic Exposure and Toenail Arsenic Concentration

S-29A7-2 Background/Aims: Although arsenic exposure from drinking water has been significantly associated with toenail arsenic (As) concentrations in adults, similar association in young adults and children, particularly at low exposure range, remains unknown. Thus, we tested a hypothesis that the dose response in adolescents and children due to As intake from drinking tube-well water and toenail As concentration is linear without threshold. Methods: In an As-endemic area of Bangladesh, all members of 50 families (n = 254) were enrolled in a prospective, repeated measures biomonitoring study. Inorganic As intake from drinking water was examined for its ability to predict the toenail As. Samples of drinking water and toenails were collected every 3 months during a 4-year period and analyzed for As using inductively coupled plasma-mass spectrometry. As concentrations in toenail were modeled using linear mixed effects models with regression splines. Results: As concentrations in drinking water varied by >1000-fold among the 254 persons (range, below detection limit—751.50 μg/L). Overall, the shape of the dose response was S-shape, with 3 distinct coefficients of association at low (<10 μg/L), medium (10–200 μg/L), and high (200–751.50 μg/L) exposure range. Water intake at medium As concentration range was associated with an 80% increase toenail As concentrations (P = 0.02). However, high water As exposure range was associated with 21% increase in toenail As concentration (P > 0.05). Furthermore, while no association was observed at the low range of water-level As concentration among boy <18 years of age, same range of exposure was associated with 68% higher toenail As level among girls <18 years old. Conclusion: Present results suggest that the dose-response relationship between tube-well As concentration and toenail concentration might significantly differ by age group, gender, and concentration range.

70 Genetic polymorphisms and risk of familial non-medullary thyroid cancer

Arsenic is associated with bladder cancer risk even at low exposure levels. Genetic variation in enzymes involved in xenobiotic and arsenic metabolism may modulate individual susceptibility to arsenic-related bladder cancer. Through a population-based case-control study in NH (832 cases and 1191 controls), we investigated gene-environment interactions between arsenic metabolic gene polymorphisms and arsenic exposure in relation to bladder cancer risk. Toenail arsenic concentrations were used to classify subjects into low and high exposure groups. Single nucleotide polymorphisms (SNPs) in GSTP1, GSTO2, GSTZ1, AQP3, AS3MT and the deletion status of GSTM1 and GSTT1 were determined. We found evidence of genotype-arsenic interactions in the high exposure group; GSTP1 Ile105Val homozygous individuals had an odds ratio (OR) of 5.4 [95% confidence interval (CI): 1.5–20.2; P for interaction = 0.03] and AQP3 Phe130Phe carriers had an OR = 2.2 (95% CI: 0.8–6.1; P for interaction = 0.10). Bladder cancer risk overall was associated with GSTO2 Asn142Asp (homozygous; OR = 1.4; 95% CI: 1.0–1.9; P for trend = 0.06) and GSTZ1 Glu32Lys (homozygous; OR = 1.3; 95% CI: 0.9–1.8; P for trend = 0.06). Our findings suggest that susceptibility to bladder cancer may relate to variation in genes involved in arsenic metabolism and oxidative stress response and potential gene-environment interactions requiring confirmation in other populations.