MATERNAL RESIDENTIAL PROXIMITY TO HAZARDOUS-WASTE SITES AND RISK FOR SELECTED CONGENITAL-MALFORMATIONS

Using data from two population-based case-control studies, we investig ated whether maternal residential proximity to hazardous waste sites i ncreased the risk for neural tube defects, conotruncal heart defects, and oral cleft defects in California. We obtained a residential histor y by interview for mothers of 507 neural cube defect cases (82.7% of e ligible) and their 517 controls (84.6%); and 201 heart cases (84.4%), 439 cleft cases (82.2%), and their 455 controls (72.1%). We identified the locations of 764 inactive hazardous waste sites and systematicall y collected information on site-related contamination for the subset o f 105 National Priority List sites. After controlling for several pote ntial confounders, we found little or no increased risk for maternal r esidence in a census tract containing a site [odds ratio (OR) = 0.9, 9 5% confidence interval(CI) = 0.7-1.3 for neural tube defects; OR = 1.3 , 95% CI = 0.8-2.1 for heart cases; OR = 1.2, 95% CI = 0.8-1.8 for cle fts], but elevated risks for neural tube defects (OR = 2.1, 95% CI = 0 .6-7.6) and heart defects (OR = 4.2, 95% CI = 0.7-26.5) for maternal r esidence within 1/4 mile of a National Priority List site. Furthermore , we observed elevated ORs (greater than or equal to 2.0) for neural t ube defects and heart defects in association with maternal residence w ithin I mile of National Priority List sites containing selected chemi cal contaminants. Among controls, only 0.4% and 4.4% lived within 1/4 mile and 1 mile of a National Priority List site, respectively, result ing in imprecision in risk estimation.