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Running in smog risky

Running in smog risky

Monday December 12 2005

The answer to Rob James’ important question about the hazard of exercising in highly polluted air is potentially complex (‘Damage to exercisers?’, December 7). Research on this and related health issues is seriously hampered by lack of funding.

So far, on a whole-population basis, our analyses have shown that pollution causes large-scale harmful effects to health at all ages. Equally, they show that exercise is hugely protective to our health and prevents premature death. We have evidence that this protective effect operates for some even in the presence of air pollution.

But it is important to note that the large benefits of exercise are gained at relatively very low levels of activity. While athletes need to ‘regularly train and race outdoors’, doing this in highly polluted air will predictably cause an injury to heart, lungs and blood vessels. In susceptible individuals this could lead to acute adverse health effects. Children may be particularly vulnerable.

But those who take regular vigorous exercise are a highly self-selected group who are probably less likely to experience health problems in the short term. It is equally likely that many non-athletes limit their activity because they experience pollution-induced symptoms.

The benefits of exercise and good nutrition may mitigate these pollution-induced health effects, but we suggest there are no strong arguments for raising your ventilatory rate to very high levels in the air of the Pearl River Delta. Unfortunately, Hong Kong’s Air Pollution Index is of no help because most of the measured harm from pollution occurs well below the average level, where health effects are officially stated to be ‘not expected for the general population’.

CHIT-MING WONG, TAI-HING LAM and ANTHONY J. HEDLEY, department of community medicine, University of Hong Kong

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