Study ties air pollution to death rate
Mortality risk seen higher in cities
CHICAGO -- Increases in air pollution caused by cars, power plants, and industry can be directly linked to higher death rates in US cities, a study said yesterday.
Reducing such ozone pollution by about 35 percent on any given day could save about 4,000 lives a year across the country, researchers at the Yale School of Forestry and Environmental Studies said.
The conclusion came from a look at 95 urban areas where about 40 percent of the US population lives, comparing spikes in ozone pollution there with death rates from 1987 to 2000.
Ground-level ozone typically increases when temperatures rise. While short-term increases have been recognized as causing jumps in hospital admissions, especially among those with chronic respiratory problems, there have been inconsistent results from studies tying them to mortality rates, the authors said.
''By linking day-to-day variations in ambient ozone levels and daily number of deaths in each of the urban areas, and pooling the results across the 95 urban areas, this study provides strong evidence of short-term effects of ozone on mortality," said Francesca Dominici, an author of the study.
''This is one of the largest ozone pollution studies ever conducted," added Michelle Bell, the lead author. ''This actually underestimates the total impact of ozone on mortality, because it only captures the mortality impact associated with high ozone levels in the past few days, not the impact associated with a lifetime exposure to high ozone levels."
High levels of ozone can trigger an array of health problems, including chest pain, coughing, throat irritation, and congestion. And it can worsen chronic respiratory conditions such as emphysema and asthma. The particulates in ozone can invade the lungs, inflaming their lining and impairing their ability to function well. Repeated exposure to ozone can result in scarring in the lungs.
The government-financed study, published in this week's Journal of the American Medical Association, found that for any given day, an increase of 10 parts per billion in ozone pollution in the previous week was associated with an increase of 0.52 percent in the daily death rate and specifically with a 0.64 percent increase in cardiovascular and respiratory-related deaths.
People ages 65 to 74 had a slightly higher increase in the death rate, at 0.70 percent. The 10 parts per billion increase would correspond to an additional 319 annual premature deaths in New York City and 3,767 premature deaths annually for the other urban communities, the study said.
Stephen Smith of the Globe staff contributed to this report. 
