Ozone: don't push it in the sun 

The damaging effects of ground-level ozone on the body are another reason to take care when exercise in the summer.

Exercise is good for you but in the sun, as well as getting plenty of water and covering up against sunburn, be aware of the effects of ozone. Ozone or trioxygen, which is higher at ground level in the summer, has previously been linked to inflammation in the lungs, and to breathing problems - particularly in older and younger people and those with asthma. But now new research from the USA shows that even at the current safe-levels, it can damage the lungs of young healthy adults.

The findings, reported in the American Journal of Respiratory and Critical Care Medicine, are based on exercise tests of 31 non-smokers between the ages of 18 and 25.

They suggest that if healthy young adults exercise outside at ozone levels of 70 ppb (parts per billion) for several hours - taking a long hike, for instance - about half will suffer respiratory symptoms like coughing or pain during deep breathing.

Current safe levels in the US are 75 ppb. The European Commission says ozone levels should be no more than 61 ppb while the UK air quality standard is 50 ppb. Today (Monday 17 August 2009), levels in the UK, were, according to the European Environment Agency's useful map, between 38 and 76 ppb. In the new study 16% (1 in 6) showed significantly decreased lung function at 60 ppb.

Sensitivity varies from person to person

'One thing that is often lost,' lead researcher Dr Edward Schelegle, of the University of California, Davis told Reuters Health, 'is that the magnitude of response to ozone varies greatly from one person to the next, and that it is important for even healthy people to be conscious of their respiratory symptoms when exercising for prolonged periods in areas where ozone levels may be elevated, even if the levels are below the current NAAQ Standard.'

At ground level, ozone can be formed as a result of reactions between sunlight and volatile organic compounds released as pollutants. On high ozone days, you can experience a 15-20% reduction in lung function.

In March, the Los Angeles Times reported that ozone pollution increased the yearly risk of death from respiratory diseases by 40% to 50% in heavily polluted cities like Los Angeles and by about 25% throughout the rest of the USA.