Chlorination by-products (CBPs) in drinking water have been associated with an increased risk of adverse pregnancy outcomes, including small for gestational age at term (term-SGA) and preterm delivery. Epidemiological evidence is weakened by a generally inaccurate exposure assessment, often at an ecological level.
A case control study with incident cases was performed in nine Italian towns between October 1999 and September 2000. A total of 1,194 subjects were enrolled: 343 preterm births (26th–37th not completed week of pregnancy), 239 term-SGA (from 37th completed week, and weight less than the lowest 10th percentile) and 612 controls. Exposure was assessed both by applying a questionnaire on mothers' personal habits during pregnancy and by water sampling directly at mothers' homes.
Levels of trihalomethanes (THMs) were low (median: 1.10 µg l−1), while chlorite and chlorate concentrations were relatively high (median: 216.5 µg l−1 for chlorites and 76.5 µg l−1 for chlorates). Preterm birth showed no association with CBPs, while term-SGA, when chlorite levels ≥200 µg l−1 combined with low and high levels of inhalation exposure are considered, suggested a dose-response relationship (adjusted-Odds Ratios (ORs): 1.52, 95%CI: 0.91–2.54 and 1.70, 95%CI: 0.97–3.0, respectively). A weak association with high exposure levels of either THMs (≥30 µg l−1), or chlorite or chlorate (≥200 µg l−1) was also found (adjusted-OR: 1.38, 95%CI: 0.92–2.07). Chlorine dioxide treatment is widespread in Italy; therefore, chlorite levels should be regularly and carefully monitored and their potential effects on pregnancy further evaluated and better understood.
Association between exposure to drinking water disinfection byproducts and adverse pregnancy outcomes in South Africa
