By Shane Robinson
March 18, 2002

A new study published in the March 6th issue of the Journal of the American Medical Association links long-term exposure to fine particles of air pollution to lung cancer. Scientists have known for several years that short-term exposure to larger particles of this pollutant can result in aggravated asthma, increases in respiratory symptoms like coughing and difficult or painful breathing, chronic bronchitis, and decreased lung function — all possibly contributing to premature death. This, however, is the first study to link long-term exposure of fine particulate matter and cancer.

Particulate matter (PM) can be emitted directly into the air from man-made sources such as automobiles and industrial boilers or indirectly as a result of chemical reactions between other pollutants emitted into the air, such as sulfur oxides (SOx). However, coal-fired power plants, refineries, pulp and paper mills, and other large industrial facilities are the biggest source of PM.

The researchers analyzed data from over a half-a-million adults who were surveyed as part of an ongoing study by the American Cancer Society from 1982 to 1998. The researchers took into account other factors, such as smoking history, diet, weight, age, sex, and occupational exposures to pollutants, and still found that the number of deaths from lung cancer increases by up to 8 to 12 percent in the most polluted areas.

Regulatory Efforts

The U.S. Environmental Protection Agency, through the States, already regulates "PM-10" — coarse particulate matter of 10 micrometers or less in diameter. However, this study focused on even finer particles, termed "PM-2.5" — particulate matter of 2.5 micrometer or less is diameter.

Health research in the mid-1990's already showed serious non-cancer impacts from these smaller particles. Based on that research, in 1997 EPA updated the national ambient air quality standard (NAAQS) for particulate matter. The new NAAQS, termed the "PM-2.5 standard" — as well as the new 8-hour ozone standard — was challenged in court by industry groups. The new standards were ultimately upheld by the U.S. Supreme Court. At the same time, however, the Court ruled that EPA must re-design its plan to implement the new standards (see related article, Status of Tougher Air Quality Standards, below).

Two proposals making their way through Congress and the White House will further affect levels of this pollutant. The first is multi-pollutant legislation that would reduce not only SOx emissions from power plants, but also their emissions of nitrous oxides (NOx) and mercury. The second proposal is regulatory changes to the New Source Review (NSR) program. Going forward with these proposals has the potential to dramatically reduce PM-2.5 levels in the air. However, environmental and public health advocates caution these efforts could also weaken efforts to reduce pollution levels. For more information about these proposals, visit www.usmayors.org/CleanAir