Persistent organic pollutants in Australian sewage sludge : environmental monitoring and land application risk assessment

Presented is a study of persistent organic pollutants in Australian sewage sludge, focusing on environmental monitoring and a sewage sludge land application human health risk contaminated with these compounds. The chemicals of concern were: • Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and 'dioxin-like' polychlorinated biphenyls (PCBs); collectively termed 'dioxins-like compounds' • The brominated fire retardants: polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) • Organochlorine pesticides (OCPs) • Polychlorinated biphenyls (PCBs) • Phthalate acid esters (PAEs). Empirical data on the concentration of these compounds was determined in a number of Australia wide surveys. A discussion of these concentrations is placed within the context of international literature for comparison. A human health risk assessment for the land application of sewage sludge contaminated with the aforementioned compounds has been completed. Four exposure pathways were identified and evaluated, that included direct human exposure, plant uptake, bioaccumulation in grazing animals, and drinking water contamination. A framework of exposure for other organic pollutants has been developed and requires tolerable daily intake (TDI) and octanol-water partition coefficient (KOW) to quantify the human exposure and risk. The increased exposure of biosolids contaminated with the 95th concentration of the chemicals of concern was determined to be less than 3 % of the maximum residue limit (MRL) of agricultural produce and demonstrates that the land application of biosolids does not pose a risk to human health from these COCs. Soil quality limits have been calculated for each of the exposure pathways that are equivalent to the MRLs.