It is well known that air pollution can adversely affect health. However a new study has found that the health benefits of walking and cycling appear to outweigh the damage caused by pollution.

While regular physical activity is known to reduce the risk of a number of conditions, including heart disease and diabetes, some have raised concerns about the effects on the body of walking or cycling in urban environments, particularly where air pollution may be rife.

One of the main sources of air pollution in cities is transport, something which many people are dependent on. UK researchers decided to look into the potential benefits of ‘active travel', e.g. walking or cycling to work rather than driving.

While previous studies have suggested that the health benefits of active travel outweigh the potential risks, these studies tended to be carried out in areas with relatively low air pollution.

This latest study used information from international studies and computer simulations to compare the risks and benefits associated with active travel in locations around the world with different levels of air pollution.

The researchers found that in practical terms, air pollution risks will not negate the health benefits of active travel in most urban areas worldwide. In other words, walking or cycling to work, for example, will outweigh the negative health effects of any pollution you may be exposed to during your journey.

"Our model indicates that in London, health benefits of active travel always outweigh the risk from pollution. Even in Delhi, one of the most polluted cities in the world - with pollution levels 10 times those in London - people would need to cycle over five hours per week before the pollution risks outweigh the health benefits," explained Dr Marko Tainio of the University of Cambridge.

However, he did note that a small number of workers in the most polluted cities, such as bike messengers, could be exposed to air pollution levels that are ‘high enough to cancel out the health benefits of physical activity'.

The researchers emphasised that these findings are ‘not an argument for inaction in combatting pollution'.

"The study provides further support for investment in infrastructure to get people out of their cars and onto their feet or their bikes - which can itself reduce pollution levels at the same time as supporting physical activity," they said.

Details of these findings are published in the journal, Preventive Medicine.