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Tuesday, March 5, 2002, 12:00 p.m. EDT
Link Strengthened between Lung Cancer, Heart Deaths and Tiny Particles of Soot, Dust
Years of exposure to the high concentrations of tiny particles of soot and dust from cars, power plants and factories in some metropolitan areas of the United States significantly increase residents' risk of dying from lung cancer and heart disease, according to a study financed largely by the (http://www.niehs.nih.gov) and conducted by scientists at Brigham Young University (http://www.byu.edu/) , Provo, Utah; the University of Ottawa (http://www.uottawa.ca/welcome.html) , Ontario, the American Cancer Society (http://www.cancer.org/) and New York University School of Medicine (http://www.med.nyu.edu/) , Tuxedo, N.Y.
Arden Pope, professor of economics at Brigham Young University in Provo, Utah, the study's co-leader, said that while far less than the risks associated with active cigarette smoking, "we found that the risk of dying from lung cancer as well as heart disease in the most polluted cities was comparable to the risk associated with nonsmokers being exposed to second-hand smoke over a long period of time."
The study evaluated the effects of air pollution on human health over a 16-year period.
Previous studies have linked soot in the air to many respiratory ailments and even death, but the new findings "provide the strongest evidence to date that long-term exposure to fine particulate air pollution common to many metropolitan areas is an important risk factor for cardiopulmonary mortality," as well as lung cancer deaths, the authors said in this week's issue of the Journal of the American Medical Association (http://jama.ama-assn.org/) .
George Thurston, Sc.D., associate professor of environmental medicine at NYU School of Medicine and study's co-leader, said, "This study provides the most definitive epidemiological evidence to date that long-term exposure to air pollution in the United States is associated with lung cancer deaths."
The study assessed the impact of particles smaller than 2.5 microns (called fine particulate matter) in cities across the United States. It analyzed data from some 500,000 adults who were followed from 1982 to 1998 as part of an ongoing cancer study. The data, which included cause of death, were linked to air pollution levels for cities nationwide using advanced statistical modeling to control for individual risk factors, such as age, smoking status, body mass, and diet, as well as for regional differences among the study populations.
The researchers calculated that the number of deaths from lung cancer increases by 8% for every 10 micrograms of fine particulate matter per cubic meter, according to the study. Larger particles and gaseous pollutants were generally not as associated with higher number of deaths.
The health dangers of tiny particles of soot in the air have been the focus of considerable controversy since 1997, when the Environmental Protection Agency issued new regulations tightening its standards to cover particles smaller than 2.5 microns (a human hair is 100 microns thick). Industry fought the regulations, but the EPA prevailed and the agency is now considering new rules for limiting the emission of the particles.
The EPA set annual average limits on fine particular matter to 15 micrograms per cubic meter in 1997. However, many cities presently exceed that standard. According to the study, from 1979 to 1983, the annual average was 24 ug/m3 in New York City, 27 ug/m3 in Los Angeles, 23 ug/m3 in Chicago and 26 ug/m3 in Washington D.C. The levels have come down over the years, and in 1999 and 2000 the annual average was 16.ug/m3 in New York, 20 ug/m3 in Los Angeles, 18 ug/m3 in Chicago and 15 ug/m3 in Washington, D.C. Despite this improvement in levels, the study shows that the prevailing levels of fine particulate matter air pollution in the U.S. are still associated with significant risk of cancer and cardio-pulmonary deaths.
The new study extends previous studies that linked chronic exposure to the small particles to deaths from lung cancer and other causes, and addresses many of the criticisms of the earlier studies. It substantially extends the follow-up analysis of an earlier study by Dr. Pope and colleagues of this same cohort, for example. It greatly expands exposure data to include gaseous co-pollutant data on gaseous pollutants and the newest data on fine particulate matter collected nationwide in 1999 and 2000. It also incorporates extensive individual-level information on other cancer risk factors such as occupation and diet, including total fat consumption and consumption of fruit and vegetables.
The study's co-authors are: Richard Burnett, Ph.D., and Daniel Krewski, Ph.D., of University of Ottawa, Ottawa, Canada; Michael Thun, M.D. and Eugenia Calle, Ph.D., of American Cancer Society, Atlanta; and Kazuhiko Ito, Ph.D., of New York University School of Medicine.
The National Institute of Environmental Health Sciences, the major financial supporter of the study, is a part of the National Institutes of Health (http://www.nih.gov) .