5.5 percent

Air pollution in the United States — caused by small-particle pollutants that can be inhaled and absorbed into the bloodstream — increased 5.5 percent between 2016 and 2018, a new study found. The increase comes after a two-decade low; small-particle pollution declined more that 24 percent between 2009 and 2016.

The report by two Carnegie Mellon University researchers, published in October by the National Bureau of Economic Research, draws on data provided by the Environmental Protection Agency and identified several reasons for the increase. These include rising natural gas use and people driving more.

EPA officials have rejected the report’s findings, according to USA Today, stating that air quality improved between 2016 and 2018.


An increase in wildfires is another factor researchers identified as a cause for worsening pollution because they release large amounts of smoke and fine particles into the atmosphere. In particular, the 2018 California wildfires played a role in driving up total national air pollution. But removing them from the equation does not eliminate the increase between 2017 and 2018.

Small-particle pollutants that the study focused on are microscopic “globs of solid or liquid in a very small droplet” suspended in the air, Anthony Wexler, the director of the Air Quality Research Center and professor of engineering at UC Davis, told USA Today. These pollutants can be inhaled and absorbed into the bloodstream and can damage a person’s respiratory system, accumulate in the brain, and send people to the emergency room, the Washington Post reported.

Abbi Matheson can be reached at abbi.matheson@globe.com. Follow her on Twitter at @AbbiMatheson