Development of human health damage factors for PM2.5 based on a global chemical transport model

Purpose Health damage from ambient fine particulate matter (PM2.5) shows large regional variations and can have an impact on a global scale due to its transboundary movement. However, existing damage factors (DFs) for human health in life cycle assessments (LCA) are calculated only for a few limited regions based on various regional chemical transport models (CTMs). The aim of this research is to estimate the human health DFs of PM2.5 originating from ten different regions of the world by using one global CTM. Methods The DFs express changes in worldwide disability-adjusted life years (DALYs) due to unit emission of black carbon and organic carbon (BCOC), nitrogen oxides (NOx), and sulfur dioxide (SO2). DFs for ten regions were calculated as follows. Firstly, we divided the whole world into ten regions. With a global CTM (MIROC-ESM-CHEM), we estimated the concentration change of PM2.5 on the world caused by changes in the emission of a targeted precursor substance from a specific region. Secondly, we used population data and epidemiological concentration response functions (CRFs) of mortality and morbidity to estimate changes in the word's DALYs occurring due to changes in the concentration of PM2.5. Finally, the above calculations were done for all ten regions. Results and discussion DFs of BCOC, NOx, and SO2 for ten regions were estimated. The range of DFs could be up to one order of magnitude among the ten regions in each of the target substances. While population density was an important parameter, variation in transport of PM2.5 on a continental level occurring due to different emission regions was found to have a significant influence on DFs. Especially for regions of Europe, Russia, and the Middle East, the amount of damage which occurred outside of the emitted region was estimated at a quarter, a quarter, and a third of their DFs, respectively. It was disclosed that the DFs will be underestimated if the transboundary of PM2.5 is not taken into account in those regions. Conclusions The human health damage factors of PM2.5 produced by BCOC, NOx, and SO2 are estimated for ten regions by using one global chemical transport model. It became clear that the variation of transport for PM2.5 on a continental level greatly influences the regionality in DFs. For further research to quantify regional differences, it is important to consider the regional values of concentration response function (CRF) and DALY loss per case of disease or death.