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Smog May Boost Risk for Several Cancers

Study finds even small increases in pollution raised overall odds of dying from disease by 22 percent

By Steven Reinberg
HealthDay Reporter

FRIDAY, April 29, 2016 (HealthDay News) -- Long-term exposure to fine particles of air pollution -- from cars, trucks, power plants and manufacturing facilities -- is tied to an increased risk of dying from several kinds of cancer, a new study suggests.

"Air pollution remains a clear, modifiable public health concern," said researcher G. Neil Thomas, a reader in epidemiology at the University of Birmingham in England.

"Put simply, the more of these particulates there are in the air, the greater the risk of getting these cancers," Thomas said, although the study did not prove the particles actually cause cancer.

The study, involving more than 66,000 older residents of Hong Kong, found an increased risk of dying from cancer for even small increases in exposure to these tiny particles of air pollution, which are measured in micrograms per cubic meter (mcg/m3). For example, the overall risk of dying from cancer increased 22 percent with every additional 10 mcg/m3 of exposure, the researchers said.

The raised risk seemed higher for some cancers than others: The additional air pollution was linked to a 42 percent rise in the risk of dying from cancer in the upper digestive tract, and a 35 percent increased risk of dying from liver, bile duct, gall bladder and pancreatic cancer, the researchers said.

Among women, the increased exposure was tied to an 80 percent heightened risk of dying from breast cancer. Among men, the higher pollution levels carried a 36 percent increased risk of dying of lung cancer, the study authors said.

"This study, combined with existing research, suggests that other urban populations may carry the same risks," Thomas said. "The implications for other similar cities around the world are that pollution must be reduced as much and as fast as possible."

Although the role of air pollution in cancer is not fully understood, it could include defects in DNA repair, alterations in the immune response or inflammation that triggers the growth of new blood vessels that allow cancer to spread, Thomas said. In cancer of the digestive organs, heavy metal pollution could also affect gut bacteria and promote development of cancer, he suggested.

In the study, it was not known whether any of the people had cancer before the study began. Researchers followed the residents until 2011. Causes of deaths were provided by Hong Kong death registries.

To gauge the exposure to tiny particles of air pollution, the researchers relied on estimates from satellite data and air quality monitors. The researchers also adjusted their findings for smoking, and excluded deaths that happened up to three years after people were enrolled in the study.

The study findings show how pervasive the harms of air pollution are, two experts said.

"This study adds to a growing body of evidence that air pollution may be associated with cancers other than lung cancer," said Susan Gapstur, vice president for epidemiology at the American Cancer Society.

Ted Brasky, a cancer control researcher at Ohio State University's Comprehensive Cancer Center, said the effect of fine particle air pollution on cancer deaths is probably larger than this study was able to show.

"These data imply that if we were to have less environmental pollution, you would have lower risks of dying from cancer," Brasky said. "Air pollution doesn't just increase the risk for asthma, lung cancer and heart disease, but might also increase the risk of dying from cancer."

Thomas said the solution is simple.

"We should therefore be aiming to limit our exposure, for instance, through legislation to force machine manufacturers, particularly for cars and trucks, into maximizing engine efficiencies that will minimize such particulates in exhaust gases and switching to non-fossil fueled engines," he said.

The study findings were published online April 29 in the journal Cancer Epidemiology, Biomarkers & Prevention.

The risk of death from cancer is not the only harm that air pollution has been tied to recently.

A study published April 27 in the journal Environmental Health Perspectives found that being exposed to just a small amount of air pollution during pregnancy may raise the risk of a complication that can cause premature birth and long-term health problems in children.

More information

For more on pollution and cancer, visit the American Cancer Society.

SOURCES: G. Neil Thomas, Ph.D., reader in epidemiology, University of Birmingham, U.K.; Susan Gapstur, M.P.H., Ph.D., vice president, epidemiology, American Cancer Society; Ted Brasky, Ph.D., cancer control researcher, Comprehensive Cancer Center, Ohio State University; April 29, 2016, Cancer Epidemiology, Biomarkers & Prevention, online

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