Study supports EPA proposal for stricter rules on particulate matter
Gary Polakovic / Los Angeles Times 14dec00
Dust and soot in the air contribute to between 20 and 200 early deaths each day in America's biggest cities, according to the largest coast-to-coast scientific study of the problem.
Ill health from particulates -- tiny specks smaller than the width of a human hair -- is spread across 20 of the largest cities in the United States, the new research indicates. Elderly people suffer the most harm.
For years, researchers have known that microscopic particles can lodge deep in the lungs. They have known, as well, that high levels of particles in the air are associated with respiratory illness, heart attacks and premature deaths.
But whether the particles are the cause of illness has been in dispute. The Environmental Protection Agency has been attempting to tighten rules that limit emissions of particles. Critics in the business community are challenging those new rules in the Supreme Court, arguing that the regulations are too costly and that the scientific evidence behind them is too sketchy.
The new study, conducted by a team of researchers at Johns Hopkins University in Maryland and published in the current edition of the New England Journal of Medicine, is likely to bolster the EPA's case. ( Abstract Below ) The researchers found strong statistical evidence that dust and soot particles, not other factors suggested by industry, appear to be causing the harmful effects. And they found that ill effects occur even in cities that meet existing national air pollution standards -- suggesting that stronger controls would protect public health.
The researchers examined daily changes in air pollution and mortality between 1987 and 1994 and made allowance for other factors that could skew the results, including access to health care, influenza outbreaks, socioeconomic status, weather and the presence of other pollutants.
The EPA currently sets the maximum allowable concentration of microscopic particles, called PM10, at 150 micrograms per cubic meter of air. All the cities tested had average air pollution levels well below that level.
But the researchers found that even at those existing levels, if the amount of particles rose by 10 micrograms per cubic meter, the rate of death increased just about one-half of 1 percent. While that increase is small, it translates into 20 to 200 deaths per day nationwide, the researchers said.
Some of the nation's worst particle smog is found in California. The state's metropolitan areas included in the study were Los Angeles, Santa Ana- Anaheim, San Bernardino, San Diego, San Jose and Oakland.
"When we look nationally, we see an effect of particles on mortality that suggests there is a public health problem. The science continues to indict particles and their role in mortality," said Dr. Jonathan M. Samet, lead author of the study and chairman of the epidemiology department at Johns Hopkins University in Baltimore.
"The higher the PM10 levels, the higher the health effects, so if you are exposed to high levels, the risk is greater," said Jean Ospital, health effects officer for the South Coast Air Quality Management District, which is charged with cleaning smog in the Los Angeles region.
Fine Particulate Air Pollution and Mortality in 20 U.S. Cities, 1987-1994
The New England Journal of Medicine 14dec00 -- Vol. 343, No. 24
Jonathan M. Samet, Francesca Dominici, Frank C. Curriero, Ivan Coursac, Scott L. Zeger
Abstract
Background. Air pollution in cities has been linked to increased rates of mortality and morbidity in developed and developing countries. Although these findings have helped lead to a tightening of air-quality standards, their validity with respect to public health has been questioned.
Methods. We assessed the effects of five major outdoor-air pollutants on daily mortality rates in 20 of the largest cities and metropolitan areas in the United States from 1987 to 1994. The pollutants were particulate matter that is less than 10 µm in aerodynamic diameter (PM10), ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. We used a two-stage analytic approach that pooled data from multiple locations.
Results. After taking into account potential confounding by other pollutants, we found consistent evidence that the level of PM10 is associated with the rate of death from all causes and from cardiovascular and respiratory illnesses. The estimated increase in the relative rate of death from all causes was 0.51 percent (95 percent posterior interval, 0.07 to 0.93 percent) for each increase in the PM10 level of 10 µg per cubic meter. The estimated increase in the relative rate of death from cardiovascular and respiratory causes was 0.68 percent (95 percent posterior interval, 0.20 to 1.16 percent) for each increase in the PM10 level of 10 µg per cubic meter. There was weaker evidence that increases in ozone levels increased the relative rates of death during the summer, when ozone levels are highest, but not during the winter. Levels of the other pollutants were not significantly related to the mortality rate.
Conclusions. There is consistent evidence that the levels of fine particulate matter in the air are associated with the risk of death from all causes and from cardiovascular and respiratory illnesses. These findings strengthen the rationale for controlling the levels of respirable particles in outdoor air. (N Engl J Med 2000;343:1742-9.)
Source Information
From the Departments of Epidemiology (J.M.S.) and Biostatistics (F.D., F.C.C., I.C., S.L.Z.), School of Hygiene and Public Health, Johns Hopkins University, Baltimore. Address reprint requests to Dr. Samet at Johns Hopkins University, School of Public Health, 615 N. Wolfe St., Suite 6041, Baltimore, MD 21205, or at jsamet@jhsph.edu
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