Fans of previous Olympic Games, most notably Beijing (2008) and Los Angeles (1984), will recall the concern over the effects of pollution and smog on the distance events, particularly for the marathon.
Indeed, so worried were some competitors in Beijing, many decided to bring smog masks that they were even considering wearing during final training sessions and perhaps even in competition. As it was, the Chinese authorities shut down the major polluting industries in and around Beijing, resulting in a relatively smog-free experience for distance athletes.
Air pollution clearly has a major effect upon exercise. Researchers reviewing the published literature have shown that exposure to carbon monoxide (CO) from everyday traffic is detrimental to athletic performance, since CO has a greater affinity with haemoglobin than oxygen.1 In other words, CO preferentially binds with red blood cells, limiting oxygen transport.
In addition, other airborne particulates such as sulphur dioxide (SO2) can pose health problems such as wheezing, chest tightness and increased airway resistance, especially for those with breathing conditions, including those who suffer exercise-induced asthma. Note that asthmatics are around 10 times more sensitive to SO2 than non-asthmatics, particularly when exercising.
Fairly obviously, the greater the physical activity level, the higher the respiratory rate and the volume of air intake. It has been estimated that, for a healthy adult male, one hour of heavy physical activity would be equivalent in terms of respiratory rate to about seven hours at rest, while for a child, vigorous activity such as playing football will result in about five times the inhalation rate as sitting playing computer games.2
Thus, if the air around you is polluted, exercising in this polluted air is a real health risk. Note that even in non-exercisers, the effects of air pollution typical of big cities “include reduced lung function, acute and chronic bronchitis, asthma attacks, emergency room visits, increased hospitalisations for respiratory and cardiac causes, elevated mortality rates, and increased duration of respiratory symptoms.”3
The five common air pollutants are ozone (O3), inhalable particles (particles of a diameter less than or equal to 10 microns, PM10), oxides of nitrogen (e.g., NO2), SO2 and CO, and it is these that are typically measured to provide an index of air quality. When the air quality is described as ‘poor’ (or ‘very high’) in the UK, it means that these common air pollutants are to be found in increased concentrations. Note that there may also be other ‘trace air toxics’ such as volatile organic compounds (e.g., toluene), metals (e.g., manganese, chromium, cadmium, lead) and aromatic (carcinogenic) hydrocarbons (e.g., benzene) in polluted air.
Outdoor physical activity should be undertaken cautiously when air quality is poor and particularly if there is a ‘smog alert’. If you or your family members already have asthma, bronchitis, chronic obstructive pulmonary disease or other related cardiovascular diseases, you should consider exercising indoors instead. Air pollution tends to be less hazardous in low traffic, non-industrial areas early in the morning, so changing training times or environments where possible can help.
- Carlisle AJ and Sharp NCC (2001), Exercise and outdoor ambient air pollution, British Journal of Sports Medicine, 35(4):214-222.
- Basrur SV (2003), Air pollution and physical activity: Examination of Toronto air data to guide public advice on smog and exercise, Toronto Public Health, June, p4.
- Ibid, p6.
This feature was first printed in the October/November 2011 issue of Fitpro Network magazine.
The views and opinions expressed in this article are those of the author and not of Fitness Professionals Ltd or Virtual Magazine. Consult a qualified health or fitness professional before making changes to your diet or exercise.