Persistent organic pollutants in sewage sludge: Levels, sources & trends

All sewage sludges in developed countries contain Persistent Organic Pollutants (POPs) and are a source of these chemicals to the environment when recycling this material to land. Therefore, it is important to understand the risks to human health and the environment from this practice. Over the past thirty years a significant amount of research has focused on this subject and this chapter presents an overview of that research. The chemicals that have been reviewed are polychlorinated dioxins/furans, polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers, polybrominated biphenyls and perfluorochemicals. A discussion of levels, sources (if known) and trends of each of the chemical groups is presented. The chapter finishes with a brief review of risk assessment work conducted in the area. Most risk assessments have concluded that there is negligible risk to human health from non-ionic POPs when applying this material to land at concentrations typically observed in contempary sewage sludges. However, assessment of the ecological consequences of sewage sludge land application still remains to be completed. Finally, studies indicate that the concentrations of most POPs in sewage sludge are declining globally, demonstrating the effectiveness of source control in reducing environmental contamination.