Air Pollution Deaths Overstated, Study Finds

A second look at a study linking soot and smoke in the air to mortality indicates fewer deaths than previously thought among people exposed to high levels of the pollution.

The findings by a team of leading researchers is rekindling debate over air pollution and could delay a review of limits for particle air pollution underway at the U.S. Environmental Protection Agency.

For years, scientists around the world have linked microscopic specks of dust, chemicals and smoke to premature death and sickness, and the new analysis affirms that connection. More than 100 scientific papers have been produced on the topic, including one 2-year-old study from Johns Hopkins University that examined death, disease rates and air pollution in 90 major U.S. cities.

Although that study, called the National Morbidity, Mortality and Air Pollution Study, also links particle pollution to sickness and premature death, when scientists reevaluated the paper this year they discovered a glitch in the computer software used to calculate statistics.

The scientists reported that, in some cases, their original findings overstated death rates from microscopic airborne particles.

For example, deaths attributable to dirty air occurred only about half as often as first believed, according to the Boston-based Health Effects Institute, which sponsored the research.

Whenever particle concentrations in the air increased by 10 micrograms--smoke and dust levels approach 200 micrograms on a very hazy day in Riverside or San Bernardino--deaths caused by heart attacks and respiratory failure increased an average of two-tenths of 1%, not four-tenths of 1% as the study first reported.

The revision may seem small, but it is likely to be used as ammunition in a long-running feud over national clean-air standards. Industry groups have been battling the EPA since the agency approved two new particle pollution standards in 1997.

The limits have not yet gone into effect. The last five years have been spent in legal wrangling that culminated in a U.S. Supreme Court ruling last year rejecting most of the objections in a lawsuit brought by the U.S. Chamber of Commerce and the American Trucking Assns.

The EPA is in the midst of a periodic review of its particle pollution standards. Agency officials say they have no plans to back off stringent air pollution limits, although in light of the new findings they say they will take more time to review the mortality study and others that might have used the same methodology.

“It doesn’t pull the whole thing down. The problem is not that great. It doesn’t derail the PM [particulate matter] standard,” said EPA spokesman Joe Martyak.

In California, the controversy is blunted because the state has long had its own set of air pollution standards more stringent than the national limits. The state Air Resources Board has proposed tightening one particle pollution standard while adding another to reflect new medical findings. A public workshop on the proposal is scheduled today in El Monte.

In several ways, the reassessment of the Johns Hopkins study in question affirms what scientists and the EPA have long believed--that daily changes in death and sickness due to air pollution correspond to changes in pollution levels.

“These preliminary analyses suggest that the new findings, though resulting in smaller estimates of effect, appear to be similar to the original in several respects,” wrote Daniel Greenbaum, president of the Health Effects Institute, in a May 20 letter.