Dioxins: Threat Versus Reality-A Case Study at a Sulfite pulp Mill

摘要

Potential human health and ecological risks associated with exposure to polychlorinated idbenzo-p-dioxins and polychorinated dibenzofurans remain a central public concern nad impretus for agency responses at bleached pulp mills. This paper examines the relative importance of PCDDs/Fs as a health risk for human and ecological receptors at a dissolving sulfite pulp mill, which recently closed in southeast alaska. Key issues wrere recognizing multiple offsite sources in the sampling strategy and applying a realistic seafood consumption rate. An uncertainty assessment demonstrated that ocnsumption of PCDDs/Fs in the typical U.S.diet results in far greater human exposure than that related ot the site. Upland ecological issues were assessed with the use of a food-web model; marine ecological evaluations included food-web modeling and sediment bionassarys. Despite use of conservative U.S. Envirinomental Protection agency methods, netither assessment identified PCDD/F risks above identified acceptable risk levels. In contrast, localized upland areas had elevated human health risks related to arsenic in soil. Similarly, observed toxicity in marine sedimnets was attributed to sulfide and ammonia. WHile PCDDs/Fs continue to be the focus of public concern and involvemnet, the remedial actions approved by regulatory agencies have been based on identified risk levels.