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WEDNESDAY, Oct. 10, 2018 (HealthDay News) -- Living in urban areas with heavy air pollution could increase your risk for mouth cancer, a new study says.
Middle-aged men living in 64 municipalities throughout Taiwan were more likely to develop oral cancer if they lived in places with high levels of air pollutants, the researchers report.
Those exposed to the highest levels of fine particulate matter in the air were 43 percent more likely to be diagnosed with mouth cancer, the study found.
The association held even after researchers controlled for other habits that could contribute to mouth cancer, such as smoking tobacco or chewing betel quid, a type of smokeless tobacco popular in Southeast Asia.
Heavy metals contained in particulate air pollution could be responsible for this risk, said senior researcher Yung-Po Liaw, a professor of public health at Chung Shan Medical University in Taichung City, Taiwan.
"The mechanism behind the association between air pollution and oral cancer is not very clear," Liaw said. "However, some metallic components of [fine particulate pollution] like lead, cadmium, arsenic, chromium and nickel, as well as organic compounds like polycyclic aromatic hydrocarbons [PAHs], are believed to be carcinogenic."
The study only found an association and not a cause-and-effect link.
"Given that many of the compounds that comprise overall fine particulate matter are carcinogens, this study raises important questions related to the health effects of pollution, beyond cardiac and respiratory effects," said Moline, vice president of occupational medicine, epidemiology and prevention.
Nearly 49,750 Americans are diagnosed with mouth cancer every year, and only about half will still be alive in five years, according to the Oral Cancer Foundation. The death rate associated with this cancer tends to be high because it is routinely diagnosed at a late stage.
"This important work could explain why there is an increase in the oral cancers among World Trade Center-exposed workers, who had a massive exposure to fine particulate matter," said Moline, who was not involved with the new study.
"Further research like this is critical to understanding the implications of air pollution, whether from industrial facilities, or the aftermath of a disaster such as the World Trade Center attacks," she added.
Fine-particle pollution -- the main cause of haze -- stems from chemicals emitted by power plants, industries and automobiles, as well as smoke from fires, according to the U.S. Environmental Protection Agency.
For this study, researchers compared the health records of more than 482,000 men 40 and older with pollution data gathered from 66 air quality monitoring stations across Taiwan.
Smoking and frequent betel quid chewing were associated with increased risk, but so too were heavy levels of particulate pollution.
Because the particles in pollution are so tiny, the heavy metals contained within them might be easily absorbed by the tissues of the mouth, researchers said. Their size might also allow them to wreak greater havoc on the body.
Liaw said people concerned about mouth cancer should pay attention to air quality reports and avoid prolonged outdoor activities when particulate pollution levels are too high. They also might consider wearing a face mask when outdoors to reduce the amount of air pollutants they inhale.
"Because it is hard to completely avoid exposure to air pollution, modification of lifestyles associated with oral cancer is encouraged," Liaw said. For instance, not smoking, not chewing betel quid and avoiding exposure to air pollutants may help prevent the malignancy, he said.
Liaw also recommended mouth-cancer screening for people living in smoggy areas, "to avoid late diagnosis and subsequent mortality."
The findings were published Oct. 9 in the BMJ.
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