Agrichemicals in surface water and birth defects in the United States.

Objectives: To investigate if live births conceived in months when surface water agrichemicals are highest are at greater risk for birth defects.

Methods: Monthly concentrations during 1996-2002 of nitrates, atrazine and other pesticides were calculated using United States Geological Survey's National Water Quality Assessment data. Monthly United States birth defect rates were calculated for live births from 1996 to 2002 using United States Centers for Disease Control and Prevention natality data sets. Birth defect rates by month of last menstrual period (LMP) were then compared to pesticide/nitrate means using logistical regression models.

Results: Mean concentrations of agrichemicals were highest in April-July. Total birth defects, and eleven of 22 birth defect subcategories, were more likely to occur in live births with LMPs between April and July. A significant association was found between the season of elevated agrichemicals and birth defects.

Conclusion: Elevated concentrations of agrichemicals in surface water in April-July coincided with higher risk of birth defects in live births with LMPs April-July. While a causal link between agrichemicals and birth defects cannot be proven from this study an association might provide clues to common factors shared by both variables.