In a new study of air pollution, scientists Tuesday reported a link between hazy skies over U.S. cities and life-threatening illnesses, including lung cancer.
A link to cancer had long been suspected but not established. Now a team of researchers from Canada, New York and Utah has found that people living in hazy cities across the nation are more likely to die of lung cancer, heart attacks and respiratory failure than people in communities with cleaner air.
They found that for every 10 micrograms of tiny particles swirling in the air, the risk of dying of lung cancer increased by 8%. Someone living in heavily polluted Bakersfield or Rubidoux, Calif., faces a risk 20% greater than someone living in Pueblo, Colo.
While the threat pales in comparison with cigarette smoking or exposure to toxic chemicals in factories, it is comparable to the hazard posed by secondhand smoke, according to the American Lung Assn.
"This study provides the most definitive epidemiological evidence to date that long-term exposure to air pollution is associated with lung cancer deaths," said George Thurston, a co-author of the study and associate professor of environmental medicine at New York University.
The report is being published today in the Journal of the American Medical Assn. It followed more subjects, about 500,000 adults, for 16 years, longer than any other study of its kind and included 156 cities, ranging from Buffalo to Los Angeles and from Pittsburgh to Huntington, Ala.
Researchers from Brigham Young University, the University of Ottawa, NYU and the American Cancer Society participated in the study. It was funded by grants from the National Institutes of Health and other government agencies.
The study comes during a time of intense political debate over the future of air pollution controls, and clean-air advocates seized upon it to challenge the Bush administration's recent attempts to alter the nation's clean-air regulations.
Two weeks ago, the White House unveiled a new anti-smog strategy for industrial and power plant emissions, but environmentalists and many air quality officials rejected it as an attempt to roll back pollution controls.
Last week, the EPA's chief of air pollution enforcement resigned in protest over Bush administration policies he said are weakening clean-air rules, particularly those that require power plants to install the most modern emission control equipment. Emissions from power plants are a major source of haze in national parks and in the eastern half of the country.
"It makes no sense to weaken the Clean Air Act in light of this important new evidence. It raises urgency to moving forward to reduce fine particles," said A. Blakeman Early, a consultant to the American Lung Assn.
The new study will likely lend support to maintaining the nation's standard for regulating fine-particle pollution.
The standard, which was approved in 1997 and affirmed by the U.S. Supreme Court, targets particles that are 2.5 microns or smaller. Health experts say the latest study reinforces the need to retain that air pollution standard and hasten air pollution cleanup.
"This study is good news because it shows our efforts in the past and current efforts to improve our air quality are not in vain but will in fact result in significant improvements in public health," said C. Arden Pope, the lead author of the study and an environmental epidemiologist at BYU.
For years, air pollution cleanup has focused on ways to reduce ozone, a gas that reduces respiratory function. Yet, more and more studies implicate microscopic particles that form haze as a serious health risk. While ozone levels are generally in decline nationwide, and dramatically so in Southern California, progress against particle pollution is more modest.
Haze comes from dust and soot. Significant sources include farm equipment, dust blowing off unpaved roads, diesel trucks and buses and portable generators.
The most dangerous particles are the smallest specks, which can float in the air for weeks, circumnavigate the globe and bypass the body's defenses to lodge deep in the lungs. Those particles come primarily from fossil fuel combustion, and some are formed when emissions from power plants, factories and vehicles react with sunlight to form microscopic bits.
California has some of the nation's highest particle pollution levels, due in part to its geography. Valleys surrounded by mountains tend to trap the haze created by cars and factories.
"We recognize it [particle pollution] as a major problem," said Shankar Prasad, health advisor to the California Air Resources Board.
Yet even in the latest study, scientists remain puzzled over which component of particle pollution is most injurious to health. Some say it may be a specific component while others say the sheer volume of particles in the air is dangerous.
"It may just be the insult of particles and the reaction they instigate in the lung," said Morton Lippmann, director of the Particulate Matter Health Research Center at NYU.