The mortality effect of PM_2.5 sources in the Greater Metropolitan Region of Sydney, Australia

We describe an assessment of the impact on mortality of eight major sources of PM_2.5 in the Greater Metropolitan Region of Sydney, Australia (GMR). We modeled exposure to PM_2.5 for the year July 2010 to June 2011 and estimated the burden of current mortality attributable to these sources. We also estimated the number of life-years that would be produced if emissions from wood heaters and power stations, the two largest emissions sources, were reduced. Wood heaters (assuming a real-world emissions factor of 11.4 g of PM_2.5 per kg of wood burned) were the most important source of PM_2.5 exposure, responsible for around 24.0% of the total anthropogenic PM_2.5 concentration. On-road sources and power stations were also important, responsible for 16.9% and 10.5% of anthropogenic PM_2.5 exposure respectively. Around 1.2% of mortality (5,900 YLL) was attributable to long-term exposure to all anthropogenic PM_2.5, including 0.3% (1,400 YLL) attributable to wood heater-related PM_2.5, 0.2% (990 YLL) to on-road sources and 0.1% (620 YLL) to power stations. Compared to ongoing emissions at 2010/11 levels, we estimated that a sustained reduction in emissions from wood heaters due to the introduction of an emissions standard of 1.5 g of PM_2.5 per kilogram of wood burned (real world emissions factor of 3.9 g of PM_2.5 per kg of wood burned) and the associated reduction in PM_2.5 population exposure would produce 90,000 life-years among the cohort of people alive in 2010/11. Complete removal of sulphur oxide emissions from power stations would produce 14,000 life-years and complete removal of nitrogen oxide emissions would produce 38,000 life-years. A range of sensitivity analyses indicate the true impact of PM_2.5 from these sources is likely to be at least as large as these estimates. This assessment shows that eight sources are responsible for more than 60% of exposure to anthropogenic PM_2.5 in the Sydney GMR. Although the burden of mortality attributable to each source is relatively small, interventions that achieve sustained reductions in emissions could provide substantial health benefits, which are likely to far outweigh the costs.