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Athletes and Air Pollution
by Dr. Alex Mroszczyk-McDonald, MAP Team Member and Winner of IM Lake Placid 2007.
For decades people have been encouraged to “get some fresh-air” or as a child to “go outside and play,” however, the air-quality in many cities and suburban areas is making this option potentially less healthy. Air pollution has become such a pervasive problem across the country that there are virtually no places left unaffected. One group that is particularly at risk are athletes who exercise outside. We are all aware of the benefits of exercise, however, what about the potential health risks? Respiratory, cardiac and thromboembolic events (stroke/heart attack) have all been linked to air pollution and exercise (1). Most people exercise near large metropolitan areas, where the air quality is often very poor. However, the air quality can be as bad or even worse hundreds of miles away from urban centers when weather patterns carry pollutants great distances from their source.
Concerns about air quality in Beijing for the 2008 Summer Olympic Games, climate change , automobile emissions and other environmental issues have driven a recent boom in studies of air pollution's medical effects. Most studies haven't used exercisers as subjects. But their results have implications for athletes, who breathe with particular vigor and oomph (2).
The air in many areas of the world contain noxious pollutants that reach unhealthful levels, such as ozone, carbon monoxide, fine particles, sulfur dioxide, nitrogen dioxide, or lead. The greatest overall public health impact of air pollution comes from fine particulates, which can be seen only with an electron microscope, however, ozone poses a particular health risk as well.
Particulate air pollution refers to a combination of fine solids such as dirt, soil dust, pollens, molds, ashes, and soot; and aerosols that are formed in the atmosphere from gaseous combustion by-products such as volatile organic compounds, sulfur dioxide and nitrogen oxides. Fine particulate pollution is ubiquitous. Cars, trucks, and diesel buses are the main source such of particle pollution and spew millions of the microscopic pollutants into the air daily (3). Pollution of this size is easily inhaled deeply into the lungs where it can be absorbed into the bloodstream or remain embedded for long periods of time. A recent study showed a 17% increase in mortality risk in areas with higher concentrations of small particles (4).
Ozone is a highly reactive gas, which makes up the major component of smog. Ozone is formed from the action of sunlight on hydrocarbons, acting in combination with oxides of nitrogen. Hydrocarbons are produced primarily by motor vehicles, oil and chemical storage and handling facilities, and a variety of commercial and industrial sources. Oxides of nitrogen are produced as a by-product of burning fuel in heavy industry and in motor vehicles (4).
Ozone acts as a respiratory irritant at the levels frequently found in most of the nation's urban areas particularly during the summer months. Symptoms include shortness of breath, chest pain when inhaling deeply, wheezing and coughing. The effects of prolonged exposures (6 ½ hours) to relatively low levels of ozone produce decreased lung function, increased pulmonary inflammation and general respiratory discomfort. In studies of animals, ozone exposure has been found to increase susceptibility to bacterial pneumonia infection. Recently, attention has begun to focus on the effects of long-term, repeated exposures to high levels of ozone. A study of a sample of long-time residents of Los Angeles, which has the highest and most frequent ozone problem in the nation, found that the group had a higher than expected loss of lung function over time, including changes in lung structure (4). Numerous ozone exposure studies, both in the laboratory and "real world" confirm that people who exercise, or otherwise participate in activities that increase their respiratory rate, respond much more severely to ozone exposure than people at rest (4).
Exercise makes us more vulnerable to health damage from these pollutants. We breathe 10-20 times more air during exercise or strenuous work than when sedentary. We draw air more deeply into the lungs. And when we exercise heavily, we breathe mostly through the mouth, bypassing the body's first line of defense against pollution, the nose (5).
The study of the health effects of compounds polluting the air is in its infancy, but evidence to date implicates them in acute effects on health and exercise performance. Furthermore these health effects are not restricted to asthma and other respiratory diseases, myocardial infarction, arrhythmia and thromboembolic complications can occur as well (1).
Air quality measures, or Air Quality Index (AQI) are more commonly acknowledged and known about in areas of the country where pollution is highest. However, there are several resources where individuals can determine the air quality and therein safety of whatever region of the country they live. One of which is AIRNow (7) which is collaboration between many national, regional and local government agencies
The AQI tells you how clean or polluted the air is, and what associated health effects might be a concern. Local affiliates of the EPA calculate the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
The AQI runs from 0 to 500, the higher the AQI value, the greater the level of air pollution and the greater the health concern. An AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality. An AQI value of 100 generally corresponds to the national air quality standard for the pollutant level which the EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory (7).
Despite all this information the resounding sentiment is that Americans should NOT stop exercising outdoors. Rather, athletes should keep their distance from cars and check air-quality forecasts before venturing out. One particular study from Hong Kong , China , another highly polluted city, found that the health risk from air-pollution may in fact be reduced for those who exercise outdoors regularly (8). Several recommendations from the American Lung Association include; train early in the day or in the evening; avoid midday or afternoon exercise, and avoid strenuous outdoor work, if possible, when ozone smog or other pollution levels are high; avoid congested streets and rush hour traffic; pollution levels can be high up to 50 feet from the roadway; make sure teachers, coaches and recreation officials know about air pollution and act accordingly. Lastly and most important, do be aware of the quality of the air you breathe (4).
Lastly, it should be noted that many American's walk to, ride their bike, or take public transportation work everyday. If there were more people doing this then we would not have to worry as much about the negative health affects of exercise.
Alex Mroszczyk-McDonald MS IV
University of Vermont College of Medicine
Team MAP Member
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References
• Mittleman , MA . Air pollution, exercise, and cardiovascular risk. N Engl J Med. 2007 Sep 13;357(11):1147-9.
• www.acsm.org American College of Sports Medicine accessed September 24, 2007
• Devlin RB, Ghio AJ, Kehrl H, Sanders G, Cascio W. Elderly humans exposed to concentrated air pollution particles have decreased heart rate variability. Eur Respir J Suppl 2003;40:76s-80s
• American Lung Association http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35356 accessed Sept 24, 2007 http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=36292 accessed September 23, 2007
• Brook RD , Franklin B, Cascio W, et al. Air pollution and cardiovascular disease: a statement for healthcare professionals from the Expert Panel on Population and Prevention Science of the American Heart Association. Circulation 2004;109:2655-2671.
• Brook R. D., Rajagopalan S., Jerrett M., Burnett R. T., Kaufman J. D., Miller K. A., Sheppard L. Air Pollution and Cardiovascular Events
N Engl J Med 2007; 356:2104-2106
• www.airnow.com accessed September 24, 2007
• Wong CM, Ou CQ, Thach TQ, Chau YK, Chan KP, Ho SY, Chung RY, Lam TH, Hedley AJ. Does regular exercise protect against air pollution-associated mortality? Prev Med. 2007 May;44(5):386-92. Epub 2007 Jan 8.
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