Air pollution has been linked to a variety of diseases, including lung cancer, other lung diseases, and heart disease. In 1997, the Environmental Protection Agency (EPA) changed its air quality standards to limit the allowable amount of fine pollution particles in the air—those that are less than 2.5 micrometers in diameter (PM 2.5 ). These new standards have been controversial. However, a recent air pollution study published in the Journal of the American Medical Association , suggests that fine pollution particles found in U.S. metropolitan areas may increase your risk of dying from lung cancer and heart and lung diseases.

About the study

In 1982, the American Cancer Society enrolled 1.2 million Americans over age 30 into the Cancer Prevention Study II (CPSII), an ongoing study that tracked the cause of death of the participants when they died. At the start of the study, participants answered a questionnaire about age, sex, weight, height, smoking history, alcohol use, occupational exposures, diet, education, marital status, and other lifestyle characteristics.

For this recent study of air pollution, U.S. and Canadian researchers analyzed data on approximately 500,000 CPSII participants who lived in metropolitan areas with available pollution data, such as New York, Chicago, Los Angeles, and Washington, D.C. In 1998 after 16 years of follow-up, researchers compared the causes of death for the participants who had died with the level of air pollution where they lived. Air pollution data was collected from the EPA's Aerial Retrieval System, the Inhalable Particle Monitoring Network, and the National Aerometric Database. These databases contain measures of pollutants in the air based on regular sampling of air at numerous sites throughout the United States.

Finally, the researchers used advanced statistical modeling techniques to determine how increases in pollution levels affected the number of deaths from all causes, from lung cancer, and from heart/lung diseases.

The findings

Overall, exposure to higher levels of fine pollution particles and the gaseous pollutant sulfur dioxide were associated with an increase in deaths from all causes, lung cancer, and heart and lung diseases. Specifically, an increase of 10 micrometers of fine pollution particles per cubic meter of air increased the number of deaths from all causes by 4%, heart and lung diseases by 6%, and lung cancer by 8%. Surprisingly, however, exposure to larger air pollution particles (greater than PM 2.5 ) and other gaseous pollutants was not associated with a higher number of deaths.

In calculating these statistics, the researchers accounted for risk factors such as smoking, high alcohol consumption, occupational exposure to pollutants, body mass index (BMI), and diet.

There are limitations to this study, however. First, personal information from the participants, such as risk factors and place of residence, was only collected at the start of the study, so any changes in this information are not accounted for in the results. Second, it's possible that other environmental factors not accounted for in this study affected the risk of dying from all causes, lung cancer, or heart and lung diseases.

How does this affect you?

How does the risk of lung cancer due to air pollution compare to the risk of lung cancer due to cigarette smoking? Long-term exposure to fine particle air pollution, say the study authors, presents roughly the same risk of lung cancer as long-term exposure to second-hand smoke.

This study provides evidence that long-term exposure to the air pollution present in American cities may increase the risk of death from lung cancer and heart and lung diseases. The findings also support the EPA's 1997 limits on fine pollution particles (PM 2.5 ), because they provide evidence that these smaller particles may cause more health hazards than larger particles and gaseous pollutants.

There is some good news, however. The results of this study also showed that fine particle pollution in U.S. cities declined during the 16 years of this study. In fact, reductions were largest in cities that had the highest pollution levels at the start of the study. Although, some cities—such as New York, Chicago, Los Angeles, and Washington—still have PM 2.5 levels that exceed the EPA limits, their levels are declining significantly. This study highlights the importance of continuing this downward trend in fine particle pollution levels.