Objective: To explore the interactive effect of chemical fertilizer exposure and drinking untreated water during pregnancy on the risk of birth defects.
Methods: The data were collected from a population-based birth surveillance system in Pingding County, Shanxi Province, from 2007 to 2012. Totally, 157 cases of birth defects were followed up and 204 healthy newborns taken as controls. The additive model and relative excess risk of interaction (RERI) were used to evaluate the interactive effect of chemical fertilizer exposure and drinking untreated water during pregnancy on the risk of birth defects.
Results: After adjusted for potential confounding factors, mothers living in villages with ≥ 65 ton/year chemical fertilizer application and drinking untreated water, as from deep underground, cellars, mountain spring, rivers, lakes or ponds, showed a higher risk of birth defects than those living in villages with <65 ton/year chemical fertilizer application and drinking tap or purified water (aOR = 2.12, 95% CI: 1.11－4.07). A strengthened interaction was observed between the annual application of chemical fertilizer at the village level and drinking untreated water (RERI = 2.08, 95% CI: 0.23－3.92, P < 0.05).
Conclusion: The pollution of drinking water may be an important pathway for chemical fertilizer exposure affecting birth outcomes.
Keywords: birth defects; chemical fertilizer exposure; untreated drinking water; interaction effect.