Ground-level ozone is a killer, says study

13 March 2009

An 18-year study in the US shows that people who live in areas with high ground ozone levels face a 30-per cent greater risk of death due to respiratory problems.

Environmental scientists already knew that increases in ozone levels during periods of heavy pollution caused short-term ill effects such as asthma attacks, increased hospitalisations and deaths from heart attacks. But the new study is the first to show that long-term, low-level exposure to the pollutant can also be lethal.

The research, published in the New England Journal of Medicine, said the issue is not just the effects of high-ozone days but the effects of long-term cumulative exposure, New York University Langone Medical Center said Thursday in a release.

Lead author Michael Jerrett of the University of California, Berkeley, said background levels of ozone have at least doubled since the pre-industrial-revolution. The findings are based on American Cancer Society data that followed 450,000 people from 1982 to 2000, covering 96 metropolitan regions in the US.

Riverside in California had the highest mean daily maximum ozone concentration during the 18-year period with 104 ppb. Los Angeles was a close second, with an estimated 43 per cent increased risk, the report said.

In contrast, San Francisco had the lowest average ozone level (33 ppb) of the 96 regions studied and only a 14-per cent increased risk, probably because of the fog and prevailing winds that reduce ozone formation. The Pacific Northwest also had low levels of ozone, again because of rain and cool weather.