It's not just the heat -- it's the ozone: Study highlights hidden dangers

I have noticed that I often feel like it's hard to breathe when it's hot, even when the particulates air pollution rating is low. Maybe it's ozone that affects me.

http://www.eurekalert.org/pub_releases/2013-07/uoy-inj071913.php

Public release date: 19-Jul-2013
Contact: David Garner
University of York

During heat waves -- when ozone production rises -- plants' ozone absorption is curtailed, leaving more pollution in the air, and costing an estimated 460 lives in the UK in the hot summer of 2006.

Vegetation plays a crucial role in reducing air pollution, but new research by the Stockholm Environment Institute (SEI) at the University of York shows that they may not protect us when we need it most: during extreme heat, when ozone formation from traffic fumes, industrial processes and other sources is at its worst.

The reason, explained lead author Dr Lisa Emberson, is that during heat waves -- when the ground is especially dry -- plants become stressed and shut their stomata (small pores on their leaves) to conserve water. This natural protective mechanism makes them more resilient to extreme heat and high ozone levels, but it also stops them from absorbing ozone and other pollutants.

"Vegetation can absorb as much as 20 per cent of the global atmospheric ozone production, so the potential impact on air quality is substantial," says Dr Emberson, a senior lecturer in the Environment Department at the University of York and director of SEI's York Centre. "What we set out to do in this study was to quantify that impact in terms of increased ozone levels and the toll on human life."

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