the risk of some cardiac anomalies. Persons living in a small valley of Tucson, Arizona, who consumed contaminated water were three times more likely to produce offspring with congenital heart disease.

A limited number of reports in the peer-reviewed scientific literature have linked spontaneous abortion, low birth weight, and birth defects to the consumption of domestic water or to other environmental exposures. A variety of other health effects, including liver and neurologic disease, have also been associated with waterborne exposure to substances from hazardous-waste sites. Some studies have detected increased rates of neurologic deficits in persons with chronic exposures to contaminants such as TCE.

Several factors lead us to conclude that contamination of domestic water supplies with a number of hazardous chemicals, such as those that could be encountered at hazardous-waste sites, is injurious to human health, although the magnitude of the risk cannot be determined. Some of the common by-products of chlorination also occur as contaminants at Superfund sites, such as dichloroacetic and trichloroacetic acid, metabolites of TCE. Moreover, exposures are not limited to ingestion, but include those due to volatization of hazardous gases and dermal absorption.

There is also evidence from epidemiologic studies that neurologic, hepatic, and immunologic function can be damaged by exposure to domestic water contaminated with some toxic chemicals. The long-term consequences of the abnormalities detected, however, are largely unknown and must be the subject of further research, on which the committee will comment in more detail in its next report.

Chapter 6: Soil and Food as Potential Sources of Exposure at Hazardous-Waste Sites

Soil provides a usually unrecognized source of exposure to contaminants. Models indicate that adults can be exposed directly or indirectly, through the food chain, and that children incur greater exposures per unit of body weight. Home gardening and ingestion of subsistence or recreational fish can be important sources of these contaminants. In addition, commercial shellfish and finfish may also be contaminated. Epidemiologic studies of hazardous-waste sites need to incorporate broader consideration of soil and food as routes of exposure.

It is difficult to identify completely the routes of exposure when ill health effects are suspected from hazardous-waste sites, as Chapter 5 notes. The same problem of determining precisely who is exposed exists for exposure through ingestion of soil as it does for exposure



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