Metals exposure in a community-initiated pilot study of drinking water

Abstract

Background/Aims: Metals are commonly found in drinking water, but the safe level for many metals (e.g. manganese (Mn)), particularly during sensitive developmental periods, is unknown. This study responded directly to community concerns about the safety of the public drinking water supply. We characterized current and past exposure to metals in 28 school-age children who resided in Holliston, Massachusetts since before birth. Methods: We collected naturally shed teeth and measured concentrations of 11 metals in dentine using laser ablation ICP-MS to represent exposure in weekly intervals during gestation through 12 months of age. Mn was also measured in residential tap water to estimate current exposure. Questionnaires were used to collect information on sociodemographic factors, past and current drinking water consumption habits and child information. We examined correlates of dentine metals concentrations in linear mixed models and characterized water Mn levels. Results: Water Mn levels ranged from 0.07 to 5302 ug/L (median: 2.3 ug/L) with 13% of samples above the lifetime health advisory of 300 ug/L. Tooth metals concentrations decreased over time for some (e.g., Mn) but not all metals (e.g., lead [Pb]). Mn levels were higher in females compared to males (prenatal: 10% [95% CI: -21%, 53%]; postnatal: 72% [7%, 174%]). Formula as predominant source of milk during infancy (compared to breastmilk) was associated with 19% [-55%, 45%] lower postnatal tooth Mn levels. For Pb, females had higher dentine Pb than males in both prenatal (36% [-14%, 113%]) and postnatal (69% [-1%, 186%]) periods. Conclusions: Results suggest differences in tooth Mn and Pb concentrations by child sex. Postnatal tooth metals concentrations are more variable than prenatal concentrations, which may suggest varied sources of exposure between time windows. Water Mn levels vary considerably spatially and temporally and sometimes exceed the lifetime health advisory, which warrants further investigation of potential health risks.