Delayed emissions of POPs from transboundary waste streams may cause spatially and temporally divergent monitoring trends.

Time trends in human concentrations of select persistent organic pollutants (POPs) during 1979-2007 in five repeated blood samples from 53 men in Northern Norway demonstrated clear relations between and environmental emissions. Despite considerable declines for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) since 1986, the sum of the 49 targeted POPs increased from 1979 until 2001, with per- and polyfluorinated alkyl substances (PFASs) dominating recent blood burden measurements. Specifically, the time trends in serum concentrations of POPs, exemplified by PCB- 153, 1,1′-(2,2,2-Trichloroethane-1,1-diyl)bis(4-chlorobenzene) (DDT) and perfluorooctane sulfonic acid (PFOS), resembled the trends in available data on their emissions, production or use. Further, emission-based mechanistic modelling, exemplified by PCBs, provided estimated blood concentrations that agreed well with the time trends observed. Our results suggest that interpretations of human biomonitoring trends for POPs should consider historic emissions. Although emissions are low in many countries compared to those in the past, many industrial POPs remain in products and waste streams even today due to the long life-time of products containing these compounds. As some of this waste is exported across country borders, this causes delayed emissions which may again cause divergent spatial and temporal trends among various monitoring studies. One example is the elevated emissions from informal waste or recycling processes in developing regions, such as of PCBs and other organic contaminants released from waste electrical and electronic equipment. Indeed, elevated concentrations of legacy POPs in humans in areas influenced by such activities have been reported. Thus, although temporal trends of the legacy POPs clearly indicate reduced human exposure to these compounds in industrialized countries, the trends in developing countries do not necessarily conform. Comparisons of the PCB concentrations from Norway, a country with no past production of PCBs and that banned new use in 1980, to available monitoring results from selected areas known to be affected by informal waste and/or recycling processes underlined that human time trends may be spatially variable across the globe, which in this specific case was likely attributed to elevated emissions from contaminants in transboundary waste streams. Clearly, knowledge of temporal and spatial differences in emissions of POPs from waste streams could guide the design and interpretation of biomonitoring studies in populations experiencing possible significant time-lags in human exposure to legacy POPs.