Assessment of dioxin-related health risks for the Melbourne metropolitan area

A community health risk assessment was conducted during 1990 in Melbourne for polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) released in Laverton North by Nufarm Limited, an agricultural chemicals manufacturer. This risk assessment incorporated current scientific knowledge into hazard identification, dose-response assessment, exposure assessment and risk characterisation sections, according to the four-step framework used by the United States Environmental Protection Agency. The hazard identification showed that health effects are unlikely to result from general population exposures to PCDDs and PCDFs. The dose-response assessment supported a safety-factor approach for PCDD and PCDF risk assessment. The exposure assessment incorporated exaggerated assumptions to estimate both total daily exposure (203 pg total toxic equivalents of PCDDs and PCDFs, or 2.9 pg/kg body weight) and daily exposure attributable to Nufarm (56.4 pg, or 0.80 pg/kg body weight) under a worst-case scenario. The risk characterisation section found that exposures under 20 pg/kg body weight per day should not induce the aryl hydrocarbon hydroxylase system, which appears to be the starting point for PCDD and PCDF toxicity. We concluded that the general population exposure to PCDDs and PCDFs in Melbourne was within the range of acceptable daily intakes used by European and Canadian governments and the World Health Organization, as well as within the range of acceptable daily intakes derived using current scientific knowledge.