Worse air quality linked to premature deaths

Air pollution in the United States increased by 5.5% from 2016 to 2018, after a decline of 24% from 2009 to 2016, according to a working paper issued by the National Bureau of Economic Research.

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The increase in air pollution, defined as the amount of fine particulate matter (PM_2.5) in the air, was associated with an additional 9,700 premature deaths from 2016 to 2018, representing damages totaling $89 billion, wrote Karen Clay and Nicholas C. Miller of Carnegie Mellon University, Pittsburgh. The increase may reflect in part the impact of the a major wildfire that occurred in the fall of 2018.

“These increases are worrisome, because previous studies have shown that PM_2.5 increases premature mortality risk,” the researchers wrote. To assess the changes in air quality, they reviewed data from the Air Quality System (AQS) database including total PM_2.5 and three PM_2.5 species: ammonium nitrate, sulfate, and elemental carbon.

To examine the impact of pollution on public health, the researchers used data from the damage function approach used in the Environmental Protection Agency’s Benefit-Cost Analysis of the Clean Air Act, the Regulatory Impact Analysis for PM_2.5, and multiple academic studies.

The number of premature deaths linked to PM_2.5 increased by approximately 4,900 between 2016 and 2017 and by 9,700 from 2016 to 2018 in U.S. counties with monitors.

Elderly individuals are especially vulnerable to particulate matter exposure and experience approximately 80% of the burden of disease related to pollution, the researchers said.

“While some deaths among the elderly are shifted by days or weeks, recent research suggests that the burden is ‘concentrated among the elderly with 5-10 years of remaining life expectancy, followed by those with 2-5 years remaining, because these groups represent a large fraction of the Medicare population and are also vulnerable to acute particulate matter exposure,’” they said.

Overall, pollution levels across the United States stopped declining in 2016. When broken down by four Census regions, no change in PM_2.5 levels occurred in the Northeast and South between 2016 and 2018; the Midwest and West showed increases in PM_2.5 of 9.3% and 11.5%, respectively.

The researchers suggested three possible factors affecting the increase in pollution: economic activity, wildfires, and air quality enforcement. They noted that increases in PM_2.5 were especially high in California, and that California accounted for 43% of the increase in pollution-related premature deaths nationwide between 2016 and 2018. When the researchers examined PM_2.5 month by month, “November 2018 had an outsized effect on our mortality calculations,” largely because the devastating Camp Fire occurred in California at that time, they said.

With regard to the impact of economic activity on pollution, the researchers reviewed data from the National Highway Administration and Energy Information Administration that showed increased use of natural gas and increased vehicle travel as contributing to higher levels of nitrate and elemental carbon in the air.

Finally, the researchers reported that enforcement of the Clean Air Act appeared to have declined since 2013, and this decline, although it might reflect increased compliance in some areas “is concerning in light of the increases in air pollution in both attainment and nonattainment counties after 2016,” they said.

The researchers had no financial conflicts to disclose.

SOURCE: Clay K, Miller NZ. NBER 2019. Working Paper 26381. doi: 10.3386/w26381.