Wildfire study highlights ozone danger

Wildfires such as those that swept California last autumn can push ozone pollution to levels that could be damaging to human health.

Scientists at the National Centre for Atmospheric Research (NCAR) found that the fires caused ground-level ozone to spike to levels that breached US health standards across a large swathe of California and neighbouring Nevada.

Publication of the study’s results in the journal Geophysical Research Letters has come as fires are again raging out of control near Los Angeles, claiming at least two lives.

Using computer models and measurements taken at ground level, the scientists looked at the wildfires of last September and October and found that they made ozone three times as likely to reach dangerous levels.

The study, funded by NASA and the National Science Foundation, is believed to be the first to quantify the impact of wildfires on health.

“It is important to understand the health impacts,” NCAR scientist and lead author of the study Gabriele Pfister said.

“Ozone can hit unhealthy levels even in places where people don’t see smoke.”

Fires worsen ozone levels by releasing nitrogen oxides and hydrocarbons, which can form ozone near the fire or far downwind as a result of chemical reactions in sunlight.

This ground-level ozone can trigger health problems from mild coughs and throat irritations, to aggravating asthma, bronchitis and emphysema.

“Wildfires are expected to worsen in the future, especially as our climate grows warmer,” Pfister said.

“But we are only now beginning to understand their potential impacts on people and ecosystems, not only nearby but also potentially far downwind.”

The researchers found that the unhealthy levels of ozone were mainly detected in rural areas.

They admitted this could be due to the computer modelling, which was unable to zoom into relatively dense urban areas, but may show that wildfire emissions have a greater impact on ozone levels in the countryside than in the cities.

Kate Martin

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