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

Abstract

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.