Health impact assessment of PM2.5-related mitigation scenarios using local risk coefficient estimates in 9 Japanese cities

Previous studies have highlighted the negative effects of PM₂.₅ on mortality, expressed in terms of attributable deaths and life years lost. However, there are very few studies assessing the health impacts of air pollution in terms of economic burden/benefits. This study assessed the health impact of two hypothetical interventions among sex- and age-specific risk populations using a robust risk estimation and economic valuation process. We utilized the sex- and age-stratified daily all-cause mortality together with the daily PM₂.₅ of the 9 Japanese cities from 2002 to 2008 in estimating the relative risks. The estimated risks were then utilized for the economic valuation of co-benefits/burden with respect to the two hypothetical PM₂.₅-related mitigation scenarios, in comparison to status quo, namely: i) decrease to Japanese standards, and ii) decrease to WHO standards. Impact of these interventions on health were assessed using the following HIA metrics: attributable mortality, attributable years life lost, and environmental health impact. A 10-μg/m³ increase in PM₂.₅ would increase the risk by 0.52% (95% CI: −0.91% to 1.99%) for all-cause mortality, with varying risk estimates per subgroup. High economic burdens were estimated at status quo, with particularly distinct burden difference for age-specific mortality; 0.40 trillion yen (0–64 y.o.) and 1.50 trillion yen (>64 y.o.). If stricter standards, relative to status quo, were to be enforced, i.e. WHO standard, there is a potential to yield economic benefits in the same risk population; 0.26 trillion yen (0–64 y.o.) and 0.98 trillion yen (>64 y.o.). We did not observe any substantial difference with the burden and benefit related to sex-specific mortality. Using the estimated local risk coefficients complemented with the valuation of the risks, policymaking entities will have the opportunity to operate their own HIA to assess the relevant air pollution-related health impacts.