Discoveries and Data: Exposures and Risk Factors

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Does living near a Superfund sites—hazardous waste sites included on the Environmental Protection Agency’s National Priority List for cleanup—raise the risk for birth defects?

To answer this question in 3 common conditions, the California Birth Defects Monitoring Program interviewed over 2000 mothers, calculating distances from their homes to hazardous waste sites.

VERY CLOSE RESIDENCE RAISES RISK

Women who lived within 1/4 mile of a Superfund site during the first 3 months of pregnancy had a greater risk for having babies with certain birth defects:

bullet-9455091 Conotruncal heart defects, a group of serious heart defects, were 4 times as likely (increasing from 1/1000 to 1/ 250 babies).
bullet-9455091 Neural tube defects—spina bifida and anencephaly—were 2 times as likely (increasing from 1/1000 to 1/ 500 babies).
bullet-9455091 Cleft lip and cleft palate occurred no more frequently than expected.

Women who lived farther than 1/4 mile from sites showed no higher risk.

ONLY A SMALL NUMBER OF FAMILIES AFFECTED

bullet-9455091 Only 0.6% of the mothers interviewed lived within 1/4 mile of a Superfund site. About half of these women lived on military bases
bullet-9455091 Hazardous waste sites were a possible factor in only a few birth defects cases: 8 of the 507 babies with neural tube defects and 3 of the 201 babies with heart defects.

IMPLICATIONS

bullet-9455091 Although the small number of cases around hazardous waste sites means the findings don’t have strong statistical power, they do support earlier research suggesting higher risk.
bullet-9455091 Study findings—higher risk for certain birth defects among those living within 1/4 mile of Superfund sites—are relevant as communities plan to develop or re-use these sites.
bullet-9455091 A central problem in studying hazardous waste sites is defining exposure. A woman living near a site may not actually have contact with its contents—airborne contamination diffuses rapidly as it travels from its source; groundwater contamination may never reach drinking water supplies. Further studies are not likely to yield more definitive answers unless they can incorporate direct exposure measures.

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