TERRESTRIAL WILDLIFE RISK ASSESSMENT FOR TCDD IN LAND-APPLIED PULP AND PAPER-MILL SLUDGE

A risk assessment was performed to evaluate the potential effects of 2 ,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in land-applied pulp and pap er mill sludge on terrestrial wildlife. Three representative bird and mammal species were assessed for potential individual risk of adverse effects. A dietary model was used to estimate TCDD exposures of adult birds and mammals, and a pharmacokinetic model was used to estimate ex posure for avian embryos. Using the quotient method, modeled exposure levels were compared to published no-observed-adverse-effect levels (N OAELs) for birds and mammals to calculate risk. Monte Carlo analysis w as used to consider the variability and uncertainty in the risk estima tes. The results su applied pulp and paper sludge may pose significant individual risks to terrestrial wildlife under certain circumstances. Shrews were found to be most at risk due to their high consumption ra te of food items that are expected to bioconcentrate the TCDD from soi l at the application sites. Of all possible pathways, only dietary exp osure was considered in this investigation; The analysis centered on p arameter uncertainty and does not include an assessment of alternative models, although this could be a significant source of uncertainty.