Ozone pollution is a killer, increasing the yearly risk of death from respiratory diseases by 40% to 50% in heavily polluted cities like Los Angeles and Riverside and by about 25% throughout the rest of the country, researchers reported today.
Environmental scientists already knew that increases in ozone during periods of heavy pollution caused short-term effects, such as asthma attacks, increased hospitalizations and deaths from heart attacks.
But the 18-year study of nearly half a million people, reported today in the New England Journal of Medicine, is the first to show that long-term, low-level exposure to the pollutant can also be lethal.
Current standards for ozone pollution cover only eight-hour averages of the colorless gas, but even with that relatively relaxed rule, 345 counties with a total population of more than 100 million people are out of compliance.
The Environmental Protection Agency "has already said that it will revisit the current ozone standards in the country," said Dan Greenbaum, president of the Boston-based Health Effects Institute, one of the study's sponsors.
"Undoubtedly, when it happens these results are going to be a very important part of that review," said Greenbaum, who was not involved in the study.
The EPA may need to implement an annual standard, said University of Ottawa environmental health scientist Daniel Krewski, one of the paper's authors.
Coauthor Michael Jerrett of UC Berkeley said the findings could have profound implications because they show that ozone worsens conditions that already kill a large number of people.
Deaths from respiratory diseases, such as chronic obstructive pulmonary disease, emphysema and pneumonia, account for about 8.5% of all U.S. deaths, an estimated 240,000 each year. Worldwide, such conditions account for 7.7 million deaths each year.
Ozone is what is known as a secondary pollutant. It is not formed directly by the burning of fossil fuels. Rather, nitrogen oxides produced by such combustion react in the presence of sunlight to form ozone. It is thus the biggest problem in areas that are sunny and hot, Jerrett said.
As an oxidizing agent, ozone reacts with virtually anything it comes into contact with. In particular, it reacts with cells in the lungs, causing inflammation and a variety of other effects that lead to premature aging.
