“Our estimates make outdoor air pollution among the most important environmental risk factors for health,” said Jason West of the University of North Carolina. “Many of these deaths are estimated to occur in East Asia and South Asia, where population is high and air pollution is severe.”

West and colleagues’ numbers for premature deaths each year are similar to other recent findings. “Because we use different methods, it is interesting to see that good agreement,” he told environmentalresearchweb. “In particular, a large study of the global burden of disease has recently concluded. While that work has certain strengths with respect to ours, our study has the strength of using multiple models.”

The team modelled air pollution for 1850 and the year 2000 with a suite of global atmospheric chemistry-climate models. Then they employed concentration-response functions from epidemiological studies to estimate the resulting number of premature deaths.

“This study is the first to use a suite of global models for this purpose,” said West. “[This…] gives us the ability to … see how results differ among the models, and to get a better idea of uncertainty over the range of models.”

The question of how many premature deaths resulting from outdoor air pollution can be attributed to climate change has received little attention, according to West. “We show that the proportion of air-pollution deaths that can be attributed to climate change that has already occurred is very small,” he said. “In fact, some models estimated increases in air-pollution deaths resulting from climate change, while some suggest that climate change has decreased air pollution deaths. More work will be needed to distinguish better the effects of climate change on air quality and health.”

Climate change is likely to affect air quality by altering temperature, humidity, rainfall rates and emissions from vegetation.

Now the team plans to investigate future air pollution deaths, including the effects of future climate change. “Since nobody knows for certain what future air pollution and climate change will look like, we will consider several different emissions scenarios, all simulated by the same ensemble of models,” said West.

West and colleagues reported the work in Environmental Research Letters (ERL).

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