estimates of environmental contributions from an individual facility to better than within a factor of 10. The models suggest that fish consumption is potentially the major pathway of human exposure to mercury and that meats, dairy products, and fish are potentially the major pathways of exposure to dioxins and furans.
Because the food chain is potentially the primary path for exposure to dioxins and furans and toxic metals such as mercury, the correlation between total exposure and local emissions is expected to be low. Because of the persistence of these pollutants and their long range transport, not all relevant sources contributing to exposure pathways are local. In addition, the foods that are implicated as the major pathway of exposure could include a fairly high portion of products imported from other regions.
Detailed information is required on the distribution of contaminants in the environment once they are released from waste-incineration facilities. Better assessments are needed of transport, accumulation, and physical and chemical transformations of contaminants through all potentially important exposure pathways, including air, food, soil, and water.
Exposures to dioxins and furans, mercury, and other heavy metals are best assessed by monitoring food consumption. Drinking water may be an important pathway in some circumstances. Models can be used to establish the chemicals' pathways to humans, regional distribution, and persistence in the environment.
Environmental assessment and management strategies for emissions from individual incineration facilities should include an appropriate regional-scale framework for assessing the collective dispersion, persistence, and potential long-term impacts of incinerator emissions on human health.
Better material balance information—including measurements of source emissions to air and deposition rates to soil, water, and vegetation—are needed to determine the contribution of waste-incineration facilities to environmental concentrations of persistent chemicals. The variation of these emissions over time needs to be taken into account for the short-term to determine if any important emission increases occur at an incineration facility, and for the long-term to measure changes due to replacement of less-efficient incinerators with modern, lower-emitting units.
In characterizing potential health effects of waste-incineration emissions, all environmental media should be assessed. Also, all possible exposure routes by which contaminants enter the body of a person should be considered, including inhalation, ingestion of food or drink, and absorption through skin. Such an approach is consistent with EPA's guidelines for health risk assessments.