When it comes to the ultra-fine particles you may breathe in from polluted air, all is not created equal as it affects your health. 

Fine particle pollutants known PM2.5 — particles that are 2.5 microns or less in diameter — appear to double the risk for premature death over time if they originate from coal-fired power plants versus other sources, a new study finds. 

“PM2.5 from coal has been treated as if it’s just another air pollutant. But it’s much more harmful than we thought, and its mortality burden has been seriously underestimated,” lead author Lucas Henneman said in a Harvard University news release. He’s an assistant professor of civil, environmental, and infrastructure engineering at George Mason University in Fairfax, Va.

The study was led by researchers at George Mason, Harvard and the University of Texas at Austin. The team reported its findings Nov. 23 in Science.

The study was based on more than two decades of Medicare data collected between 1999 and 2020.

The team estimate that exposure to coal PM2.5 could have contributed to over 460,000 U.S. deaths over the study period. Most of these deaths occurred between 1999 and 2007, when coal PM2.5 levels were highest, Henneman and colleagues said.

Scientists have long known that PM2.5 can lodge deep in the human respiratory tract, with unhealthy results.

But until now, it wasn’t known if the source of the PM2.5 mattered. 

“As countries debate their energy sources — and as coal maintains a powerful, almost mythical status in American energy lore — our findings are highly valuable to policymakers and regulators as they weigh the need for cheap energy with the significant environmental and health costs,” study co-author Francesca Dominici, professor of biostatistics, population and data science at Harvard, said in the news release.

The study, which was funded by the National Institutes of Health, also used detailed data on emissions from 480 U.S. coal plants over the same study time period.  

The team looked at how these emissions drifted in the short term over geographic areas to create “exposure fields.”

They compared exposure field data to 1999-2016 Medicare data on seniors who were living and dying in those areas. 

A rise in levels of airborne coal PM2.5 was linked to a 1.12% increase in local death rates — double the increase compared to a local uptick in PM2.5 coming from any other source.

Drilling down further into the data, the team was able to estimate the contribution to local death rates of individual power plants. 

Overall, 10 of the 480 plants are thought to have each contributed to 5,000 excess deaths over the two decades of the study. 

But there was also some good news: Reductions in the prevalence of coal-fired power plants across the U.S. after 2007 was mirrored in a rapid reduction in these types of deaths. 

“Deaths from coal were highest in 1999 but by 2020 decreased by about 95%, as coal plants have installed scrubbers or shut down,” Henneman said.

In fact, “I see this as a success story,” study senior author Corwin Zigler, associate professor of statistics and data sciences at UT Austin, said in the news release. “Coal power plants were this major burden that U.S. policies have already significantly reduced.”

However, he stressed that “we haven’t completely eliminated the burden — so this study provides us a better understanding of how health will continue to improve and lives will be saved if we move further toward a clean energy future.”

More information

Find out more about PM2.5 at the California Air Resources Board.

SOURCE: Harvard T. Chan School of Public Health, news release, Nov. 23, 2023

Source: HealthDay