Evaluation of the relative contribution of exposure routes in a health risk assessment of dioxin emissions from a municipal waste incinerator.

Polychlorinated dioxins (PCDDs) and furans (PCDFs) are perceived by the public as the most hazardous materials emitted from municipal waste incinerators. These compounds disperse in the atmosphere and deposit on environmental media, where they may bioconcentrate in the food chain, resulting in a number of potential sources for human exposure. We performed a cancer risk assessment of PCDD/PCDF emissions from a municipal waste incinerator to evaluate the relative contribution of various exposure routes. Three scenarios were examined, all of which predicted ingestion of fish to be a significant source of exposure. In the common case, representative of the general population consuming mainly foods from commercial sources, inhalation was predicted to be the source of greatest exposure, followed by ingestion of fish, beef, milk, vegetation, and soil. In addition to fish, milk and beef ingestion contributed significantly to total exposure under the highly-exposed and worst case scenarios. Life-time cancer risk from the emitted PCDD/PCDFs was assessed for each scenario and was estimated as 1.8 x 10(-7) (common case), 2.5 x 10(-6) (highly-exposed case), and 6.7 x 10(-6) (worst case). In view of the conservative assumptions used in the assessment, the relatively low magnitude of these risks suggests that the PCDD/PCDF emissions from this incinerator should not be considered a significant public health concern.