CA Cancer J Clin 2002; 52:125
doi: 10.3322/canjclin.52.3.125
© 2002 American Cancer Society
AIR POLLUTION LINKED TO DEATHS FROM LUNG CANCER
Previous studies have linked particulate air pollution to premature death from cardiovascular and non-malignant lung disease. Now a recent report in JAMA (2002;287:1132-1141) also describes increased death rates from lung cancer in the most polluted cities, even among lifetime nonsmokers.
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A recent study links increased death rates from lung cancer in some cities to air pollution.
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"There’s an excess risk of both lung cancer and cardiopulmonary disease associated with increased exposure to fine particles [in air pollution]," said study first author C. Arden Pope III, PhD, of Brigham Young University.
Smoking is clearly the main cause of lung cancer, said Pope, but breathing very polluted air long term can raise risk of lung cancer as much as breathing second-hand smoke, he added. The effect of polluted air on deaths from heart disease and lung cancer was apparent in lifelong nonsmokers as well as in current and former smokers.
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Study Longest, Largest Yet
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Earlier studies including a 1995 analysis from the American Cancer Society’s Cancer Prevention Study II (CPS-II) have reported associations between acute exposure to air pollution and cardiopulmonary diseases. Two studies that were particularly important to the Environmental Protection Agency’s (EPA) 1997 decision to tighten limits on particulate air pollution were the Harvard Six Cities Study and CPS-II. An extensive reanalysis by a Canadian team of air pollution researchers has replicated the major findings of these earlier studies.
Because of the substantial public health, regulatory, and economic implications of this issue, Pope and coauthors from Health Canada, the American Cancer Society (ACS), and New York University conducted the most com-prehensive study to date on the long-term effects of air pollution on mortality rates.
The current analysis was based on CPS-II, an ongoing prospective mortality study of over 1.2 million adults recruited in 1982 by ACS volunteers. The new study included about 500,000 of the CPS-II participants who resided in over 100 metropolitan areas for which data on air pollutants were available. Overall mortality rates, as well as mortality rates for cardiopulmonary diseases, lung cancer, and other causes were determined from 1982 to 1998, longer follow-up than for any previous study.
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Risk Increases as Pollution Increases
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The study found a progressive increase in death rates from cardiopulmonary disease, lung cancer, and all causes of death combined associated with higher levels of particulate air pollution. Fine particulates (smaller than 2.5 microns) and sulfur oxides were the two pollutants most clearly associated with the increases in mortality.
The risk of lung cancer death increased by eight percent with every ten micrograms of fine particles per cubic meter of air, and death rates for heart disease and non-neoplastic lung diseases increased by six percent. The impact of these two disease categories was to increase the all-cause death rate by four percent for every such increase in fine particulates.
The association between particulate air pollution and increased death rates persisted in Cox proportional hazards analyses adjusted for demographic factors (age, sex, race, education, and marital status) and environmental or lifestyle exposures (smoking, alcohol, occupa-tional dust, and diet).
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Limits Imposed by the EPA
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Scientists had known since the 1970s that acute episodes of air pollution were associated with short-term increases in mortality from heart and lung disease. By the 1980s and 1990s, studies were reporting increases in cardio-vascular and respiratory diseases even at ambient levels of air pollution. In 1997, the EPA limited emissions of fine particulate for power plants and other sources.
Air pollution has lessened since the 1970s, Pope said, but was still above the current EPA limits in some US cities as late as 1999 and 2000.
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Relation of Air Pollution to Cancer
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"Most of the risk associated with particulate air pollution relates to cardiovascular and nonmalignant lung diseases rather than lung cancer," says coauthor Michael Thun, MD, ACS Vice President for Epidemiology and Surveillance Research. "The association with lung cancer received much of the media attention on this study because it was the new finding. While air pollution is an important and legitimate public concern, it should not distract attention away from tobacco control."
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Study Longest, Largest Yet
Risk Increases as Pollution...
