Air pollution can affect exercise

Exposure to air pollution is a common part of city life but in regions where these levels are much higher than the average, such as Hong Kong, it is known to have a detrimental impact on public health.

However, it is now thought that air pollution can also mean that exercise actually has a negative effect on health, rather than a positive one, and could be putting people at risk of developing a serious illness.

Dr Michael Tse of the Active Health Clinic at the Institute of Human Performance in Hong Kong told the South China Morning Post: "At rest, we have some basic protection measure against pollution - our nose. The olfactory tissue and nose hairs act as a kind of first defence."

However, when a person's rate of breathing is increased, such as when exercising, exposure is radically increased, according to the expert. Not only do people breathe quicker and more often when running, but at higher intensities, it is common to breath through your mouth to get sufficient oxygen. This leads to a "direct intake of pollutants", Dr Tse said.

This puts strain on the lungs and cardiovascular system, with each breath damaging the fine tissue in the lungs and causing inflammation. 

"As inflammation is repeated, a person is at greater risk of developing asthma, bronchitis, chronic obstructive pulmonary diseases, damage to the mucous producing glands in the airways, and has an increased risk of pneumonia," Professor Anthony Hedley, creator of the Hedley Environmental Index and Emeritus Professor at the University of Hong Kong's School of Public Health, told the South China Morning Post.

This can often mean that those suffering from respiratory illnesses, such as asthma, are at a higher risk.

A study published in the American Heart Association Circular in 2005 found that inhalation of diesel exhaust impairs blood vessel functioning. The double-blind research exposed 30 healthy men aged between 20 and 38 years old to diluted diesel exhaust or regular air for one hour during intermittent exercise at a moderate level. The team at the University of Edinburgh found that this brief period of exposure had caused damage to the heart and surrounding vessels, providing a link to the development of plaque or lesions in the blood vessels and heart attacks.