Wildfires push ozone above legal levels

Scientists in the US have discovered that wildfires can push up ozone levels so high that they threaten human health.

Researchers at the National Centre for Atmospheric Research looked at ground ozone levels in California and neighbouring states during the California wildfires of 2007.

This was a particularly intense wildfire year in California as drought conditions combined with powerful winds to spread the flames of 9,000 fires, wiping out over 2,000 homes.

Scientists found that during the fires, ozone at ground level repeatedly hit levels dangerous to humans across widespread areas in California and neighbouring Nevada.

Wild fires release large amounts of nitrogen oxides and hydrocarbons into the atmosphere, which can then spread ozone across vast areas as the chemicals react with sunlight.

This means that ozone levels can be dangerously high even in places where no-one can see smoke.

The research, sponsored by NASA and the National Science Foundation, was carried out using computer models and data from 55 ground monitoring stations.

Ozone hit levels higher than legal air quality standards 66 times during the research period.

Manifest as a yellow haze, ozone hangs in the air and increases the risk of respiratory illnesses, particularly among elderly people and children.