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NZ has ‘nek minute’, WHO has ‘next target’

Reducing global particulate matter pollution could save millions of lives

Globally, more than 3.2 million premature deaths per year are attributed to exposure to ambient fine particulate matter (PM2.5). A new study estimates that 2.1 million premature deaths could be avoided if countries achieved the WHO guideline for PM2.5. Even meeting their closest WHO interim concentration targets could avoid 750 000 (23%) deaths attributed to PM2.5 per year.

The World Health Organization has issued a specific guideline value for ambient PM2.5, set at 10 ug/m3 as an annual average. It has further given interim targets concentrations for PM2.5 at 35, 25, 15 ug/m3, target values that can be used by governments to approach the final guideline value of 10 ug/m3 in a stepwise manner.

The study found that limiting PM2.5 concentrations to WHO interim target levels 35, 25, 15, or 10 µg/m3, could avoid approximately 0.39, 0.73, 1.4, and 2.1 million annual premature deaths, respectively. Another strategy, called ‘next target’ (a country at 27 µg/m3 would try to get down to its closest lower target of 25 µg/m3, for example) could save approximately 750 000 lives globally.

The study also revealed the impact of demographic factors and the (non-linear) exposure-response function on PM2.5 mortality. Highly polluted areas require a greater reduction of PM2.5 than less polluted areas to achieve the same decrease in attributed mortality. In the most highly polluted areas, such as India and China, a 50% reduction in mortality would require a 68% reduction of PM2.5. Conversely, a 50% mortality reduction in less polluted areas, such as Europe and North America, could be achieved through a reduction of just 25% of PM2.5.

The researchers stress that initial improvements to ambient PM2.5 concentrations must be worked into long-term mitigation strategies, which will differ greatly between more or less polluted areas. Population age structure should also be taken into account when planning mitigation policies, they say. In fact, if the world met the World Health Organization 10 µg/m3 target, nearly 70% of the total mortality avoided would be concentrated in East Asia and India because these areas are densely populated and currently experience high PM levels. Importantly, the researchers say there is also high potential for reducing mortality in less polluted areas as well. Furthermore, there could also be positive impacts on climate change because PM2.5 mitigation may also reduce the emission of other accompanying pollutants, such as black carbon.

Source: Apte, J. S., Marshall, J. D., Cohen, A. J. & Brauer, M. (2015). Addressing Global Mortality from Ambient PM2.5. Environmental Science & Technology 49(13): 8057-8066. DOI:10.1021/acs.est.5b01236.

Contact: JSApte@utexas.edu