Fine particulate matter air pollution raises risk of lung cancer death in never-smokers

October 31st, 2011 by American Journal of Respiratory and Critical Care Medicine

Long-term exposure to air pollution containing fine particles of soot, dirt, smoke and other materials causes a small but measurable increase in lung cancer among men and women who have never smoked, according to researchers in Canada and the United States, who studied the association between long-term exposure to fine particulate matter air pollution and lung cancer death among 188,699 men and women.

Car exhaust gases are a major source of Guernsey's air pollution. Cars emit benezene, nitrogen dioxide, Benzoapyrene and particles (PM 10s and PM 2.5s) (click image to expand - ©RLLord)

The findings were published online ahead of the print edition of the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.

“We showed that long-term concentrations of fine particulate matter found in the air are associated with an increase in lung cancer death among lifelong never-smokers, and that even small increases in fine particulate matter can significantly raise an individual’s risk for death from lung cancer,” said Michelle Turner, a Ph.D candidate at the McLaughlin Center for Population Health Risk Assessment at the University of Ottawa.

Particulate matter, or PM, is the term for tiny particles of material found in the air. Particles less than 10 micrometers in diameter are considered to be a health risk because they are small enough to be inhaled into the lungs. Fine particulate matter, or PM2.5, refers to particles that are less than 2.5 micrometers in diameter – about 1/30th of the width of a human hair – and are considered to pose the most serious health risks, since their small size allows them to lodge deep within the tissues of the lungs. The World Health Organization (WHO) has estimated that long-term PM2.5 exposure is responsible for approximately 5 percent of all cancers of the airway.

“There is compelling evidence that acute and chronic exposure to ambient fine particulate matter air pollution increases cardiopulmonary mortality, but the role of PM2.5 in the development of lung cancer has been less clear,” said Ms. Turner. “We conducted this study with the hope of further defining the association between fine particulate air pollution and lung cancer mortality.”

For their study, the investigators examined health data from 188,699 lifelong never-smokers who had enrolled in the American Cancer Society’s Cancer Prevention Study (CPS)–II in 1982, and followed them prospectively through 2008. At initial enrollment in 1982, study participants were assigned regional designations based on their household zip code. For this study, researchers used those designations to determine the concentrations of fine particulate matter in specific areas using central monitoring data. Then, the researchers correlated that information with lung cancer mortality data from study participants.

The researchers found that each increase in fine particulate matter of 10 micrograms per cubic meter of air was associated with a 15 percent to 27 percent increase in lung cancer mortality. The association between PM2.5 and lung cancer mortality was similar in men and women and across categories of age and educational attainment, but was stronger in those with a history of chronic lung disease at enrollment.

Although this large, prospective study showed clear positive associations between mean long-term ambient fine particulate matter air pollution concentrations and lung cancer mortality the magnitude of lung cancer risk associated with exposure to fine particulate matter is notably smaller compared to that of active cigarette smoking, the researchers said.

“The results of this study will aid in a clearer understanding of the relationship between fine particulate air pollution and the development of lung cancer, and could be especially important in areas where levels of air pollution are particularly high,” Ms. Turner said.

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Another study, “Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution” published in the Journal of the American Medical Association (JAMA) in 2002 concluded that “long-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality.”

 

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