Presenter: Toru Kawai (National Institute for Environmental Studies)

Description:
With the implementation of the Minamata Convention on Mercury, a reduction in anthropogenic mercury emissions is expected. Numerical modeling is useful for quantitatively assessing when, where, and to what extent such emission reductions correspond with mercury levels in the environment and within organisms, and with the risks of human exposure to mercury. In recent years, global models that simulate the long-range transport and multimedia dynamics of mercury have been developed. These models calculate the production and decomposition of methylated mercury (MeHg) in pelagic seawater and its transfer to marine particle organic matter (POM). In this study, we calculated the weekly intake (WI) of MeHg via seafood ingestion for 209 countries worldwide; MeHg concentrations in POM were simulated by our global model, FATE-Hg. We also used FAO global statistical data for seafood food balances. The calculated WI was below the provisional tolerable weekly intake (PTWI = 16 μg Hg/kg/week) in 187 countries, which is 90% of the 209 countries for which WI was calculated. Geographically, WI tended to be relatively high in island countries such as Small Island Developing States (SIDS) near the equator. We also estimated the contribution of various sources of MeHg in the seafood consumed. The results showed that, on a global average, the contribution of anthropogenic emissions since the Industrial Revolution was approximately 60%. The remaining 40% was due to other sources such as anthropogenic emissions before 1850 and geogenic emissions. Of the contribution of anthropogenic emission since 1850, emissions from East Asia, Europe, and North America were 9%, 16%, and 15%, respectively. Considering that East Asia is currently the largest mercury emitter, these results suggest that a significant amount of mercury that was emitted in the past has accumulated in present-day seafood.