Congenital cardiac anomalies in relation to water contamination, Santa Clara County, California, 1981-1983.

In November 1981, a leak of solvents from an underground storage tank was detected at an electronics manufacturing plant in Santa Clara County, California. Solvents (predominantly 1,1,1-trichloroethene, or methyl chloroform) were found in a nearby well which supplied drinking water to the surrounding community. Residents were concerned about a possible relation between adverse reproductive outcomes and consumption of contaminated water. To address this concern, the California Department of Health Services conducted two epidemiologic studies: one of these, reported here, is a county-wide study of cardiac anomalies. This study, which looked at major cardiac anomalies among births throughout Santa Clara County in 1981-1983, found an increased prevalence in the service area of the water company which operated the contaminated well. During the potentially exposed time period (January 1981 through August 1982), 12 babies with major cardiac anomalies were born to residents of this area. This represents an excess of six cases over the number expected based on the prevalence in the remainder of the county (relative risk = 2.2, 95 per cent confidence interval 1.2-4.0). No excess was observed in the unexposed time period (September 1982 through December 1983). However, the temporal distribution of major cardiac cases born during the exposed time period suggests that the solvent leak is an unlikely explanation for this excess.