Carnegie Mellon University
September 25, 2020

EPP Faculty and Alums research flows of particulate matter damage in the U.S.

In a new study, EPP PhD alums Brian Sergi (’19) and Inês Azevedo (’09), along with EPP Professor Nick Muller and Steve Davis find that emissions flows across U.S. county lines plays an important role in health damages from air pollution.

Despite several decades of declining emissions, the health costs of particulate matter (PM2.5) in the U.S. remain substantial, with more than $1 trillion in annual damages. The group of researchers analyzed the inter-county impacts of PM2.5 for 2008, 2011, and 2014 and found that even though emissions from point sources have fallen over this period, the share of PM2.5 attributable to pollution transported across the county and state boundaries is still considerable in many localities. Importantly, the benefits of reduced emissions are not uniformly distributed nationwide, with 26% of counties—concentrated in the South, Midwest, and Pacific Northwest—experiencing worsening health damages since 2008. Around 30% of all U.S. counties receive 90% of their health damages from emissions in other counties, and these damage-importing counties also tend to have lower median incomes.

The researchers found that falling emissions from point sources over 2008 to 2014 have contributed substantially to the reduction in health damages from exposure to PM2.5, with deaths falling by 23,000 annually. The group found that the dramatic decline is largely attributable to coal plants, many of which have closed for economic reasons or have begun to operate emissions control technology.

Declining emissions levels have been used by some to advocate for a diminished federal role in regulating air quality. Yet the group's results underscore the continued importance of inter-county, interstate, and regional flows of pollution and policies capable of reducing them. In 2014, imports accounted for over 90% of total annual health damages from PM2.5 in nearly a third of U.S. counties; for 90% of counties, 75% of damages are imported from elsewhere. These illustrate that emissions flows are the dominant source of health damages from PM2.5 across most of the country.

The group claims that the dichotomy between the interdependencies of health damages from PM2.5 and the jurisdictional boundaries of local political systems implies the need for more integrated emissions planning that connects producers who emit with those that utilize those goods and services.

To read the full publication, go here.