Study links ozone to higher death risk

Posted by Laura Grant on March 12, 2009
Posted in Green News

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Los Angeles smog by Infinite Wilderness licensed under Creative Commons licence

We normally think of ozone in connection with the hole in the atmosphere that’s letting in ultraviolet radiation and increasing the risk of skin cancers. When it’s in the upper atmosphere, ozone is beneficial to us. But when we breathe it in at ground level, it’s not. A new US study has found that long-term exposure to ground-level ozone, a major component of smog, is associated with an increased risk of death from respiratory ailments.

Ground level ozone is formed through a complex chemical reaction in sunlight between nitrogen oxides (NOx), commonly spewed from vehicle exhausts, and industrial factory emissions.

To analyse the risk of death for both ozone and fine particulate matter, two of the most prevalent components of air pollution, researchers followed nearly 450,000 people in 96 metropolitan regions in the United States for two decades, according to the University of California, Berkeley. Michael Jerrett, UC Berkeley associate professor of environmental health sciences, led the study.

The researchers found that people living in areas with the highest concentrations of ozone, such as Los Angeles, had a 25 to 30 percent greater annual risk of dying from respiratory diseases compared with people from regions with the lowest levels of the pollutant.

“This is the first time we’ve been able to connect chronic exposure to ozone, one of the most widespread pollutants in the world, with the risk of death,” said Jerrett.

“Previous research has connected short-term or acute ozone exposure to impaired lung function, aggravated asthma symptoms, increased emergency room visits and hospitalisations, but the impact of long-term exposure to ozone on mortality had not been pinned down until now.”

The study found that for every 10 parts-per-billion (ppb) increase in ozone level, there is a 4 percent increase in risk of death from respiratory causes, primarily pneumonia and chronic obstructive pulmonary disease.

“World Health Organisation data indicate that about 240,000 people die each year from respiratory causes in the US,” said Jerrett. “Even a 4 percent increase can translate into thousands of excess deaths each year. Globally, some 7.7 million people die from respiratory causes, so worldwide the impact of ozone pollution could be very large.”

The study is published in the March 12 issue of the New England Journal of Medicine.

Source: UC Berkely

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