Many of us dream of running in a pristine environment where the cool air gently glides across our face as we pause for a revitalizing drink of water from the fresh mountain stream. The birds merrily chirp as we inhale the crystal clear air and fill our lungs with life-giving oxygen. Unfortunately, for many of us, this is just that—a dream. The reality is that we live and exercise near large metropolitan cities, where we may be exposed to many pollutants.

All across the world, millions of people lace up their running shoes to run, jog, or walk around parks, in the streets, and on tracks. In their pursuit of health and fitness, many are exposing themselves to dangerous air pollutants. The air carries not only life-giving oxygen, but lethal pollutants such as ozone, carbon monoxide, fine particles, sulfur dioxide, nitrogen dioxide, and lead, which at unhealthy levels, may lead to sickness or in extreme cases—death.

The connection between air pollution and exercise should concern all of us, especially those who are more vulnerable to air pollution. This group includes:

• Children

Asthmatics

Those with heart and lung disease

In order to make smart choices about outdoor activity, it is essential to understand the acceptable levels of pollutants (especially ozone) and how they are being measured for the benefit of the general public.

According to the Environmental Protection Agency (EPA), ozone is composed of three atoms of oxygen, is odorless and colorless. Not all ozone is bad; in fact the two levels of ozone, upper and lower are quite different. The upper level of ozone, which is found 10 to 30 miles above the Earth’s surface, provides protection from harmful ultraviolet rays, while the lower level of ozone, found near ground level can be very harmful. The EPA states that lower level ozone, also known as "Bad Ozone" is formed when pollutants emitted by cars, power plants, etc. react chemically in the presence of the sun (8).

In order to inform people of ozone levels the EPA created the Air Quality Index (AQI), a valuable tool for determining whether it is safe to exercise outdoors.

The AQI is an index for reporting daily air quality (3). It tells you how clean or polluted your air is, and what associated health concerns you should be aware of. The AQI focuses on health effects that can happen within a few hours or days after breathing polluted air. EPA uses the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, the EPA has established national air quality standards to protect individuals against dangerous health effects.

The AQI is a measuring tool that runs from 0 to 500. A higher AQI value indicates a greater level of air pollution and health danger. For example, an AQI value of 50 represents good air quality and 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, which is the level the EPA has set to protect public health. So, AQI values below 100 are generally thought of as safe. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as AQI values get higher.

The purpose of the AQI is to help you understand what local air quality means to your health. To make the AQI as easy to understand as possible, the EPA has divided the AQI scale into six categories, shown below:

Each category corresponds to a different level of health concern. For example, when the AQI for a pollutant is between 51 and 100, the health concern is "Moderate." Here are the six levels of health concern and what they mean:

• "Good" The AQI value for your community is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk.
  
• "Moderate" The AQI for your community is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of individuals. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.
  
• "Unhealthy for Sensitive Groups" Certain groups of people are particularly sensitive to the harmful effects of certain air pollutants. This means they are likely to be affected at lower levels than the general public. For example, children and adults who are active outdoors and people with respiratory disease are at greater risk from exposure to ozone, while people with heart disease are at greater risk from carbon monoxide. Some people may be sensitive to more than one pollutant. When AQI values are between 101 and 150, members of sensitive groups may experience health effects. The general public is not likely to be affected when the AQI is in this range.
  
• "Unhealthy" AQI values are between 151 and 200. Everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.
  
• "Very Unhealthy" AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.
  
• "Hazardous" AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected.

The EPA and others are working to make information about outdoor air quality as available to the public as information about the weather. A key tool in this effort is the AQI. EPA and local officials use the AQI to provide the public with timely and easy-to-understand information on local air quality and whether air pollution levels pose a health concern.

The AQI can serve as a powerful tool in protecting you and your family from the negative effects of pollution. But, there is further information regarding pollution and it’s effects on certain populations that should be understood also.

The EPA has gathered research regarding the effects of ozone on people through the use of controlled testing on human volunteers, animal research, and studies that compare health statistics and ozone levels within communities. These studies have been conducted in order to determine the effects of ozone on lung function. The following four groups of people have been identified as having high sensitivity to ozone.

Children.

Adults who are active outdoors.

People with respiratory disease.

People with unusual susceptibility to ozone.

CHILDREN: A SPECIAL RISK

Children may be more vulnerable to the effects of a number of air pollutants because their lungs are still developing and air pollution may cause or contribute to the development of chronic lung diseases. Children are especially vulnerable to pollution-caused lung problems during exercise because:

* For their size they breathe more, and faster, than adults.

* They are more active and more likely to play outdoors.

* Like adults during exercise, mouth breathing is common.

* Sports and outdoor activity at school are most likely to occur when smog levels are highest.

When ozone levels reach a national PSI level of 200 (0.20 parts per million), children exercising outdoors experience respiratory irritation and a decline in lung function. Therefore, they should avoid calisthenics, soccer, tag, running, competitive swimming, basketball, tennis and other strenuous exercise outdoors. In a field study (6) of children during normal activities at summer camp, lung function measurements were taken before, during and after ozone levels reached above .12 ppm on four days and .18 ppm on one day. Lung function failed to return to its pre-episode level for many days after the ozone episode had passed.

When ozone levels are high, substitute intense exercise with activities such as recreational swimming, archery, low-intensity weight training, or stationary bike riding.

Should the ozone level reach a national PSI reading of 235 (0.275 ppm), all outdoor sports and games involving physical activity should be suspended as significant respiratory tract irritation is likely to occur at this ozone level.

Air quality has improved over the last 20 years, but air pollution is still an important health problem in many areas across the country, including most cities. The two most common pollutants are ozone (smog) and particulate matter (pollen, soot, dust, etc.). Children are very sensitive to the effects of air pollution. Children breathe more rapidly than do adults, and inhale more pollution per pound of body weight than adults. Therefore, their lungs have a greater chance for being exposed to harmful air pollutants. While exercising, children breathe more heavily and air pollution can be inhaled more deeply into the lungs.

When children have a cold or are exercising, they often breathe through their mouths, taking in more pollutants than if the air was filtered through their noses. Because children's lungs are still developing, repeatedly breathing in polluted air may contribute to permanent lung damage (2).

You can help protect the children in your care from the harmful effects of air pollution by:

• Not conducting outdoor activities on days when the air quality index in your area is 100 or above. In communities where air pollution is a problem, local radio and television stations and newspapers report this index.
• Scheduling outdoor activities for the early morning on smoggy days, especially in the summer. In many communities, summer smog levels peak in mid to late afternoon on hot days (over 90 degrees) when the air is stagnant.
• Conducting outdoor activities away from areas with heavy traffic (2).

The Centers for Disease Control and Prevention (CDC) recently released a study indicating that the decreased citywide use of automobiles in Atlanta during the 1996 Summer Olympics led to improved air quality and a large decrease in childhood emergency room visits and hospitalizations for asthma. Atlanta’s inner-city children on Medicaid seemed to benefit the most from this Olympic experiment in city transportation planning, showing 42% decrease in asthma-related emergency room visits.

Asthma is a serious public health dilemma in the United States and a leading cause of life threatening childhood illness. It’s estimated that among children 18 years of age and younger, 6.9% of them may have asthma (7). "Many studies have shown a link between high air pollution days and worsening asthma symptoms which may lead to emergency room visits. But the impact of citywide transportation changes on air quality and childhood asthma had not been previously studied," said Michael Friedman, MD, epidemiologist in CDC’s environmental health program and lead author of the study.

The study compared data on the number of emergency medical visits for asthma and nonasthma-related conditions during the Olympic Games to a four-week period before and after the Olympics. Although some Atlanta residents left the city during the Olympics, the total number of emergency medical visits did not change during that period, while the number of emergency visits related to asthma decreased considerably. The study statistically linked the prolonged improvements in ozone and particulate matter pollution to a drop in emergency visits for asthma. The study also found that traffic pattern changes, rather than weather changes, seemed to account for most of the improved air quality in Atlanta.

"Our study is important because it provides evidence that decreasing automobile use can reduce the burden of asthma in our cities and that citywide efforts to reduce rush-hour automobile traffic through the use of public transportation and altered work schedules is possible in America," said Friedman.

Asthma is a very complicated disease with many possible causes. Air pollution resulting from automobile congestion is only one factor that may trigger an asthma event requiring emergency care. Therefore, efforts to decrease automobile emissions and improve air quality may not help everyone’s asthma. But this study demonstrates that the reduction of these emissions may have a significant impact on the overall public health burden of asthma, especially in the inner cities (7).

HOW AIR POLLUTION AFFECTS YOUR BODY

Our lungs are among the body's primary points of contact with the outside world. We breathe in an estimated 15,000 liters of air, approximately 6 to 10 liters every minute, drawing life-giving oxygen across 600 to 900 square feet of surface area in tiny sacs inside the lung. Oxygen is necessary for our muscles to function. In fact, the purpose of physical activity is to improve the body's ability to deliver oxygen. As a result, when we exercise, we may increase our intake of air by as much as ten times our level at rest.

An endurance athlete can process as much as twenty times the normal intake. Mouth breathing during exercise bypasses the nasal passages, the body's natural air filter.
These facts mean that when we exercise in polluted air, we increase our contact with the pollutants, and increase our vulnerability to health damage.

The interaction between air pollution and exercise is so strong that scientists typically use exercising volunteers in their research. Research has found that air pollution can reduce breathing ability, cause chest pain, coughing, wheezing and other physical irritation.

Air pollution can interfere with the workings of the lungs, heart and other organs. As mentioned earlier, it can aggravate asthma and other chronic lung and heart diseases,

and may weaken the lung's defenses against infection

MINIMIZE YOUR RISK: MANAGE YOUR EXERCISE

The news isn't all bad. You can minimize your exposure to air pollution by being aware of pollution and by following some simple guidelines:

Watch The Calendar

Ozone tends to be worst during the May-to-September "smog season." Be especially conscious of smog levels during warm weather. In warm areas, smog can be a problem at any time of the year. Carbon monoxide pollution levels also are related to the weather, as well as to altitude. In the western U.S., the highest carbon monoxide levels are found in the winter months (1).

Consider the time

Since sunlight and time are necessary for ozone smog formation, the highest levels of ozone typically occur during the afternoon. Since carbon monoxide is produced primarily by motor vehicles, the highest carbon monoxide levels usually occur during rush hour or during other traffic congestion situations.

Charting Air Quality

Area officials use a simple scale to forecast and report on smog levels. Depending on where you live, it may be called the Air Quality Index (AQI) or Pollutant Standards Index (PSI). Current air quality is reported as a percentage of the federal health standard for a pollutant. If the current index is above 100, air pollution exceeds the level considered safe.

If ozone smog levels are above 100, children, asthmatics and other sensitive groups should limit strenuous exercise. Even otherwise healthy people should consider limiting vigorous exercise when ozone levels are at or above the health standard.

If the index is above 200, corresponding to an ozone pollution level of 0.20 parts per million (ppm), the pollution level is judged unhealthy for everyone. At this level, air pollution is a serious health concern. Everyone should avoid strenuous outdoor activity, as respiratory tract irritation can occur.

Fitness enthusiasts should be aware of air pollution in their area and take precautionary measures to minimize their risk. Tune in to the weather reports. Television and newspaper weather reports usually include air quality updates, using the AQI or the PSI to rate pollution levels. If the index is under 100 for ozone or carbon monoxide, then go ahead and exercise and breathe heartily. Levels of 100 to 199 are considered not safe. At levels above 200, the air is considered very unhealthful and exercise enthusiasts should take their workouts indoors or take a break until the weather improves. Exercise in the early morning or late evening hours, well before or after rush hour. The following are a few more helpful tips:

* 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.

* Ensure teachers, coaches and recreation officials know about air pollution and act accordingly.

* Alter the intensity of the workout by reducing running speed or by reducing the number of repetitions and sets in weight training workouts. During high smog days, it’s safer to concentrate on technique workouts rather than high intensity workouts that would demand high amounts of oxygen. It’s also advised to take long rest breaks during your training session (4).

* Avoid contact with cigarettes or cigars. Secondary cigarette smoke is loaded with carbon monoxide and nicotine. These substances have been found to be detrimental to both health and sports performance (4, 5).

The positive benefits of exercise far outweigh the negatives. Use your common sense and take the advice of the environmental professionals in your local area. Refrain from engaging in strenuous outdoor activity when local officials issue health warnings. Don't take air pollution lightly, it can be extremely harmful!

For more information related to air quality and the environment, contact:

U.S. Environmental Protection Agency (EPA)
1200 Pennsylvania Avenue, NW
Washington, DC 20460

(202) 260-2090

web site: www.epa.gov
________________________________________________________________________

6. South Coast Air Quality Management District, www.aqmd.gov/smog/inhealth.html

7. Journal of the American Medical Association (JAMA). 21 February 01, www.cdc.gov/od/oc/media/pressrel/r010221.htm

8. What You Need to Know About Ozone and Your Health, EPA-452/K-99-001, July 1999
http://www.epa.gov/oar/oaqps

Rob Wilkins, originally from Linden, New Jersey, is a Technical Sergeant in the US Air Force stationed at AFTAC, Patrick Air Force Base, Cocoa Beach, Florida. Wilkins is also a Special Assistant to the International Federation of Bodybuilders (IFBB) and a recipient of the IFBB Gold Medal (Oct ’00). To contact Wilkins e-mail him at waaszup@yahoo.com.