Simulating the potential implications of transboundary waste exports on the fate and exposure to PCBs

Polychlorinated biphenyls (PCBs) are one of the few classes of chemicals for which relatively detailed information on production, use and emissions is available. The physical-chemical properties of these compounds are also reasonably well-characterized. Using these input data, the fate/transport and human exposure to these contaminants has been simulated at various spatial and temporal resolutions and compared to available monitoring data. While good agreement between model output and monitoring data is frequently observed, there are some notable exceptions. Of particular interest is the number of monitoring studies reporting surprisingly high levels of PCBs within or in proximity to developing nations in West Africa and South Asia. These observations led to the hypothesis that a substantial shift in PCB emissions has occurred recently, attributable to the export of wastes containing PCBs from developed countries (i.e., main historic source regions) to developing regions. Based on this hypothesis, existing historic PCB emission inventories were updated by Breivik et al. (SETAC Vancouver) using global flows of e-waste as a proxy for transboundary movement of wastes containing PCBs. The purpose of this study is to simulate and compare the global fate and transport of PCBs using the original and revised emission inventories in order to assess the potential significance of these waste exports at regional and global scales. To accomplish this task, we use the BETR Global 2.0 model, a publicly available fate/transport model which represents the globe as 288 interconnected, multi-compartment zones at a spatial resolution of 15 x 15 degrees. Simulations are conducted for the period 1930–2100 and output from various locations and time periods are interpreted in the context of available monitoring data. Model output is also used to characterize the potential implications of transboundary movement of wastes containing PCBs for human exposure in countries currently receiving these products.