Exploring the possible implications of exports of waste towards developing regions for global emissions of PCBs

The global production of polychlorinated biphenyls (PCBs) peaked more than 40 years ago and ceased when the last factories closed in Russia in 1993. Yet, PCBs continue to be omnipresent in the global environment. While this is partly caused by their environmental persistence, another key aspect is that most PCBs were used in closed applications with long use-life expectancies (e.g., capacitors, transformers), which may cause significant delays between production/use and primary emissions. Over the last decade, a number of studies have reported surprisingly high levels of PCBs within or outside developing regions in Asia and West Africa. As PCBs were never extensively produced nor used in these regions, this previously led us to hypothesize that there might be a potential shift in global source regions, attributed to exports of wastes containing PCBs towards developing regions. If true, it follows that global emissions cannot be completely estimated, nor fully rationalized, without considering emissions caused by the global flows of relevant wastes. In this study, we have therefore updated an existing global historical PCB emission inventory to account for exports of wastes, using global flows of e-waste as a proxy for wastes containing PCBs. Our revised emission scenarios indicate that (i) global emissions may significantly increase as result of exports of wastes in comparison to reference scenario (i.e. no exports) and (ii) different long-term temporal trends in emissions within former production and use regions versus developing regions implicated as importers of wastes are expected. In summary, our results therefore suggest that exports of wastes may lead to divergent temporal and spatial patterns of PCBs in the global environment (see Armitage et al. SETAC Vancouver). Yet, significant uncertainties in these global emission scenarios (i.e. our hypothesis with regard to the magnitude, location and timing of PCB emissions) still persist because of (i) a lack of accurate activity data (flows of relevant wastes), as well as (ii) studies allowing for accurate emission estimates from informal recycling and disposal in developing regions.