Adults with long-term exposure to ozone (O3) face an increased risk of dying from respiratory and cardiovascular diseases, according to a study published online ahead of print in the American Journal of Respiratory and Critical Care Medicine.

Using data from a large US study begun in 1982, researchers found that every additional 10 parts per billion (ppb) in long-term ozone exposure increased the risk of dying by:

  • 12% from lung disease
  • 3% from cardiovascular disease
  • 2% from all causes.

Researchers said the increased risk of death was highest for diabetes (16%), followed by dysrhythmias, heart failure and cardiac arrest (15%) and by COPD (14%).

Researchers took into account fine particulate (PM2.5) pollution, an established cause of premature mortality, and nitrogen dioxide (NO2) pollution, which has been linked to premature mortality. They adjusted for 29 behavioral and demographic factors, including smoking, alcohol use, body weight, occupational exposures, diet, poverty, and race.

Researchers found the association between ozone and mortality began at 35 ppb, based on the annual 8-hour average. They said that many communities are above this level, suggesting further reductions in ozone would have immediate health benefits. Dr. Jerrett added that reducing ozone, a potent greenhouse gas, would also provide future health benefits by reducing climate change.

Researchers were surprised by one finding: near-source PM2.5, largely attributable to traffic, was more strongly associated with death from cardiovascular disease than regional PM2.5, largely attributable to fossil-fuel burning and secondary formation of the particles in the atmosphere. With each 10-ppb increase in near-source PM2.5, mortality rate rose 41%, compared to 7% for regional source.

“About 130 million people are living in areas that exceed the National Ambient Air Quality standard,” said Michael Jerrett, PhD, chair of environmental health sciences at UCLA and study co-author. “While ozone has decreased in the US, the reductions are not nearly as big as decreases in other pollutants, and elsewhere in the world, ozone is a growing problem.”