Wildfires wipe out 20 years of air quality improvements in western USA

While this year’s wildfires in Canada and the USA had an impact around the world, wildfires – albeit on a smaller scale – have been having a local impact for years and a new study has examined their long term effects for the first time.

The researchers from the University of Iowa calculated black carbon concentrations from satellite data and 500 ground-based monitoring stations by using ‘deep learning’, a form of AI which enables computer systems to produce accurate predictions from a collection of different data. Daily concentrations were calculated at a 1-km resolution in the USA for the 20 years between 2000 and 2020.

The areas where the concentration of black carbon has risen most are shown in red, and in blue where it has fallen.

Premature deaths were calculated through a formula that incorporated average life span, black carbon exposure, and population density.

The reserarchers found that both PM2·5 and black carbon in the USA had been decreasing overall during 2000 to 2020 (22% decrease for PM2·5 and 11% decrease for black carbon), leading to a reduction of around 4,200 premature deaths per year.

However, since 2010, from when there has been an increasing occurrence of severe wildfires, that decrease has been reversed in the western USA which saw a 55% increase in PM2·5 and an 86% increase in black carbon. This lead to an increase of 670 premature deaths. The eastern USA, which has been unaffected by such wildfires saw no such increase in particulates or mortality.

Jun Wang, James E. Ashton professor and chair in the Department of Chemical and Biochemical Engineering, assistant director of the Iowa Technology Institute at the University of Iowa, and the lead corresponding author on the study said: ‘Our air is supposed to be cleaner and cleaner due mostly to EPA regulations on emissions, but the fires have limited or erased these air-quality gains. In other words, all the efforts for the past 20 years by the EPA to make our air cleaner basically have been lost in fire-prone areas and downwind regions. We are losing ground.

‘Wildfires have become increasingly intensive and frequent in the western U.S., resulting in a significant increase in smoke-related emissions in populated areas. This has likely contributed to a decline in air quality and an increase in attributable mortality.’

Jing Wei, the study’s lead author, added: ‘The increasing number and intensity of wildfires in the U.S. counteract or even overshadow the reduction in anthropogenic emissions, exacerbating air pollution and heightening the risks of both morbidity and mortality.’



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