From AFP report:
The study found that the risk of dying from respiratory disease increased as much as 50 percent as a result of long-term exposure to high concentrations of ground-level ozone.
This is the first study to look at the long-term health impacts of ozone, which is formed through the chemical reaction between sunlight and the nitrogen oxides spewed from vehicle exhaust and industrial emissions.
"Many studies have shown that a high-ozone day leads to an increase in risk of acute health effects the next day, for example, asthma attacks and heart attacks," said study co-author George Thurston of New York University’s medical school.
"What this study says is that to protect the public’s health, we can’t just reduce the peaks, we must also reduce long-term, cumulative exposure."
The researchers estimate that the risk of dying from respiratory causes rises four percent for every 10 parts-per-billion increase in exposure to ozone.