Exposure to Disinfection By-Products in drinking water during pregnancy and congenital anomalies - a case-control study in the Emilia-Romagna Region (Northern Italy)

Introduction: Epidemiological and toxicological studies suggest that exposure during pregnancy to various Disinfection by-products (DBPs), mainly Trihalomethanes (THMs), can increase the risk of congenital malformations (CA), however evidence is not conclusive. This study aimed at investigating the association between CA and different DBPs in an area, where various disinfectants are used. Methods: A register based case-control study was carried out in Emilia-Romagna region. Data on chromosomal anomalies and different CA (neural tube, cardiovascular, abdominal wall, cleft lip and palate, respiratory, genital and urinary tract defects) occurred in the period 2002-2005 were extracted from the Regional Malformation Registry. 4 Controls (newborns without malformations) were randomly selected form the Regional Birth Register and frequency matched to cases according to pregnancy period. The network supplying drinking water during the first trimester of pregnancy was identified on the basis of mother’s address: DBPs data, technical and structural information were linked to each subject. Results: Overall, THMs levels were very low (3.8±3.6μg/l), and no risk excess was observed. Chlorite and chlorate values were fairly high, (427±184μg/l and 283±78μg/l, respectively). In comparison to those exposed to levels 700µg/l were, after adjusting for personal, reproductive and socio-economical confounders, at higher risk of newborns with renal defects (OR:3.3;95%IC:1.4-8.1), abdominal wall defects (OR:6.9; 95%IC:1.7-28), cleft palate (OR:4.1; 95%IC:0.98-16.8); while women with chlorate level >200µg/l were at higher risk of newborns with obstructive urinary defects (OR:2.9; 95%IC:1.1-7.6), spina bifida (OR:4.94; 95%IC:1.1-22). Conclusions: This was the first study evaluating the relationship between CA and both THMs and chlorite/chlorate exposure: significant increased risks were observed, mainly for urinary tract defects, when chlorite and chlorate exposure occurred.