Temporal trends of persistent organic pollutants in digested sewage sludge (1993-2012)

The analysis of temporal trends is a key tool to assess the success of national and international regulations on chemical pollution. Persistent organic pollutants (POPs) are chemical pollutants, which are not only harmful, but also because of their slow environmental degradation they pose a long-time risk. In this study, concentrations of selected POPs were measured between 1993 and 2012 in digested sewage sludge from eight municipal waste water treatment plants. Polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-dioxins and furans (PCDD/Fs), which have been banned or restricted for decades, exhibited decreasing trends with apparent half-lives between 9 and 12years. Polybrominated diphenyl ethers (PBDEs) and long-chain perfluorinated acids showed no clear trend, which reflects the recent introduction of regulations. The analysis of octabromodiphenyl ethers did not reveal indications for reductive debromination of decabromodiphenyl ether; however the analysis of total bromine showed that up to 14% of the total bromine load in sewage sludge originated from PBDEs (average 2%). This is the first study to report temporal trends for more than 20years of series POPs in sewage sludge.