It’s well known that smoking can lead to lung cancer. New research also finds a connection between air pollution and lung cancer.
A team of epidemiologists have been looking into the causes of various cancers, beyond smoking, for years. They recently published their third study in the series, which focuses on lung cancer, in the journal Environmental Health.
It’s a disease that can take 20 years to develop, so they designed a study to take smoking out of the equation over time.
“What if no one smoked 20 years ago, what would cancer rates look like today?,” asked coauthor Doug Myers, a professor in epidemiology and sociology in the School of Public Health at Boise State University.
The researchers looked at 1,078 counties in the 15 states that provided data to the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) program, and simulated a scenario where everyone stopped smoking.
On average, lung cancer rates were cut by more than half, but the results varied widely. In some counties, lung cancer rates plunged. But in others, there was only a modest drop.
“Then immediately, the question is, well, why? What’s going on in those counties?” said coauthor Dave Kriebel, professor emeritus in environmental epidemiology in the Department of Public Health at the University of Massachusetts Lowell.
At first, they found that what they called the “low benefit” counties were more likely to be urban. “Which naturally led us to suspect air pollution,” the authors said in an email.
Using data from the Environmental Protection Agency’s Air Quality Index (AQI) they found that in counties with higher pollution levels, cancer rates remained higher than in places with cleaner air.
“We wanted to see more specifically which chemicals might be responsible for the lack of improvement,” Myers said.
A closer look at certain pollutants
The researchers analyzed AQI data for the year 1999 in ‘low benefit’ counties for pollution.
They found urban counties that benefited less from the elimination of smoking had high concentrations of radon, as well as benzene, diesel exhaust, and polycyclic organic matter (POM), a class of chemicals that are formed during combustion.
“It could be wildfires, but it also is burning combustion products in vehicles and some other kinds of burning,” Kriebel said, explaining that POM is a complicated mixture of compounds.
“Certainly the coke oven is going to be one place to find that in a place like Allegheny County.”
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While Pennsylvania does not contribute data to the SEER program used in this study, the researchers used 2019 data from the Pa. Department of Health to look at the impact of smoking on cancer rates in counties in southwestern Pa. They found Allegheny County was a ‘low benefit’ county, when smoking was eliminated.
Using data from U.S. EPA and other sources, the researchers also found that twenty years earlier, in 1999, Allegheny County had among the highest levels of any county they analyzed for the pollutants in their study. Allegheny County was one of 53 counties with coke oven pollution, and compared to others nationwide, had more diesel exhaust exposure than 96% of counties and more benzene than 97%.
The researchers were surprised in their latest study to find a link between non-smoking related lung cancer rates and benzene, which is emitted from coke ovens, as well as many other sources.
“We think we’re the first ones to see an environmental association between benzene and lung cancer,” Myers said. “Which means we need to do more work to confirm this.”
The limitations of an epidemiologic study
This study did not look at the specific causes of individual lung cancer cases. “It’s inherent in this kind of data set and analysis that you don’t have a direct link between the person’s exposure and their outcome,” said Lianne Sheppard, a professor of biostatistics and environmental health at the University of Washington, who wasn’t involved with this research. The Allegheny Front asked her to review it.
Sheppard found the study’s conclusions were reasonable: that cancer prevention efforts should focus on more than personal habits, like smoking, but also on public policy.
“It’s another way of showing that it’s not just what we do as individuals, but it’s also what is in our environment that can impact whether we get cancer or not,” she said.
Kriebel sees good news in their findings, “Because it says, ‘Oh, this is not this hopeless,'” he said. For example, Allegheny County and other areas can use public policy to reduce diesel pollution cars and trucks.
“These are things you can control. We can do something about diesel exhaust,” he said. “We can keep trucks out of neighborhoods. We can switch from diesel to electric trucks.”
The research was funded in part by the Heinz Endowments, which also funds The Allegheny Front.
