“Overall, this large, multicounty analysis provides evidence of significant associations of fine particles with daily mortality among nearly two-thirds of California’s population,” scientists concluded. The study is one of the first to examine the association between deaths and tinier pollutants, which studies show are more toxic that other microscopic soot.
Scientists have found what appears to be a significant association between the daily health-related death rate in Sacramento and other populous counties in California and the amount of haze in the air that day, state environmental officials said in what they described as the largest study of its kind.
The statistical analysis comparing daily mortality with levels of tiny tailpipe exhaust particles smudging the skies showed a strong enough correlation to implicate the wind-blown specks in the deaths, which would be limited mainly to people with heart or lung disease, the researchers said.
Health-related deaths in Sacramento County averaged 22 a day during the 1999-2002 study period.
“These people are dying earlier than what their life expectancy normally would be,” said Bart Ostro, the state’s top air pollution epidemiologist who conducted the study along with scientists at the University of California, Davis, and UC San Francisco. The results were released Friday.
The link is particularly evident among women, diabetics and people over 65, according to the peer-reviewed study, published in the scientific journal Environmental Health Perspectives.
The study raised several questions, such as why higher mortality rates were found among people with less than a high school education. Researchers said this was probably a reflection of poor diet and health care and higher exposure to heavy traffic, such as by living close to freeways.
Also, researchers could only speculate as to why the increase in the death rate from lung diseases in Sacramento County was more than double that of any other area studied, except Orange County.
The chemical composition of particles might vary by area, researchers suggested.
Ostro has launched a follow-up study to learn which factors — such as obesity, age, location of residence — might explain why the pollution affects some regions and some groups of people more than others.
Without identifying such risk factors, Ostro said, this would be “just another scare story.”
The Office of Environmental Health Hazard Assessment, Cal-EPA’s scientific arm, initiated the study to help regulators identify better ways to cut people’s exposure to pollution, such as tougher auto emission controls, better land-use planning and encouraging healthier lifestyles.
“It’s important to know the factors that affect our health, and fortunately this is something we can do something about,” Ostro said.
In the past decade, many studies from around the world have tied the inhalation of microscopic specks, or soot, to heart attacks and lung-related deaths.
The correlations found in the California study are considered especially robust because it looked at a much larger population, about 23 million.
The study is one of the first to examine such associations with tinier pollutants, known as “fine particles,” which studies show are more toxic.
“Overall, this large, multicounty analysis provides evidence of significant associations of fine particles with daily mortality among nearly two-thirds of California’s population,” scientists concluded in the paper.
The fine, wind-blown particles penetrate more deeply into lungs than ordinary dust, aggravating existing heart and lung conditions, such as asthma, and even triggering death, many studies show.
Even brief episodes of severe particle pollution — a day or two — can be enough to kill people with asthma or heart disease sooner than expected.
The California study focused on these day-to-day exposures, taking four years of data from air pollution monitors in downtown Sacramento and in other cities in Contra Costa, Fresno, Kern, Los Angeles, Orange, Riverside, San Diego and Santa Clara counties.
Death data during the same period were obtained from the state Department of Health Services.
The California findings come as the U.S. Environmental Protection Agency is revising national standards for fine particles, which measure 2.5 microns or less in diameter and are mainly products of fossil fuel combustion in automobiles, power plants and other sources.
A human hair is about 100 microns in diameter.
“The EPA administrator is going to have a harder time rejecting the stronger standards proposed by his own staff,” said Dr. John Balmes, a volunteer consultant for the American Lung Association.
Balmes, a UC San Francisco professor of medicine, was not connected with the study.
The findings support California’s initiative in setting the nation’s strictest enforceable limits on fine-particle pollutants, adopted in 2002 by the state Air Resources Board, said Dr. Joan Denton, director of Cal-EPA’s Office of Environmental Health Hazard Assessment.
She supports tightening standards nationwide.
“We should not overlook the potential health impacts of the smallest of these particles,” Denton said.
California has some of the worst particle pollution in the nation.
Hardest hit are the inland, poorly ventilated counties in the southern San Joaquin Valley and in Riverside and San Bernardino counties.
The Sacramento area generally meets national standards for particle pollutants, except during the Thanksgiving and Christmas holidays when smoke from wood-burning fireplaces is heavy.