Exposure to chlorite and chlorate in drinking water and adverse pregnancy outcomes in Italy.

Introduction: Chlorite and chlorate are the main Disinfection By Products (DBPs) in drinking water when chlorine dioxide treatment is applied. Exposure to DBPs during pregnancy has been associated with adverse outcomes, such as miscarriage, preterm delivery, Small for Gestational Age at term (term-SGA): however to date epidemiological evidence is inconclusive, mainly due to inaccurate exposure assessment. At the moment chlorine dioxide treatment is widely used in Italy: a multicentric study was carried out in Italy, aimed to evaluate the association, if any, between chlorite and chlorate in drinking water and both preterm delivery and term-SGA. Methods: A case control study with incident cases was performed in 9 Italian towns between October 1999-September 2000. Preterm deliveries and term-SGA newborns in the areas were cases, and singleton births, at term and weight >10th percentile were controls; n.1194 subjects were enrolled and n.893 water samples were collected from subjects' homes (433 cases and 460 controls) where drinking water was treated with chlorine dioxide or both with chlorine and chlorine dioxide. Chlorite and chlorate levels and also concentrations of other DBPs as total Trihalomethanes (tTHMs) were evaluated; moreover each subject was required to fill out a previously validated questionnaire about personal habits associated with exposure to DBPs, both by inhalation and ingestion. Also information about those characteristics which could act as confounders was collected. Multivariate logistic analysis was carried out adjusting for those variables significantly associated in univariate analyses. Results: Levels of tTHMs were generally very low (median: 0.01 [mu]g/l), while chlorite and chlorate, when detectable (45% of the sample for chlorite and 34% for chlorate), showed high concentrations (median: 216.5 [mu]g/l for chlorite and 76.5 [mu]g/l for chlorate). Multivariate logistic analysis adjusted for sex of the newborn, education, water-based beverages, kind of water usually drank (tap or bottled mineral water) and tobacco smoke showed an association between term-SGA and chlorite when levels were >= 200 [mu]g/l and also high exposure both by ingestion and inhalation (daily showering and bathing) was present. (OR: 1.99, 95%CI: 1.06-3.74). An even weak association is suggested with either tTHMs >= 30 [mu]g/l, or chlorite/chlorate >= 200 [mu]g/l present in water (OR: 1.38, 95%CI: 0.92-2.07), while preterm delivery did not show any association with DBPs exposure. Conclusions: The association between term-SGA and chlorite in drinking water may be due to chlorite itself, or to a different DBP produced by chlorine dioxide, or to a not yet identified confounder: anyway as levels of chlorite and chlorate appeared sometimes very high, the presence and significance of these substances in drinking water must be investigated further as the number of water utilities applying chlorine dioxide is increasing.