The air we breathe

Waking up early in the morning to jog a few miles may leave people in an enviable fitness wake.

But when the air is constantly reported to be polluted from the toxic fumes that ruin the environment – what could it also do to the jogger’s health?

Air pollution can be sourced to cars or industry, and those in densely populated areas are constantly suffering noxious conditions.

Additionally, when temperatures are hot, or air movement is low, air quality can reach such a polluted concentration that it can severely hamper the jogger’s physical comfort.

Common air pollutants include carbon monoxide, sulphur oxides, nitrogen oxides, lead, ozone, peroxyacetyl nitrate, aerosols, soot, dust and smoke and some effects can not be seen until they are inside the body.

More than one pollutant present in the body has a powerful effect. Once breathed in, it can be detected immediately in the respiratory tract.

Nose hairs do hinder large particles and highly soluble gas from entering the body (99.9 per cent of inhaled sulphur is blocked by the nose), but smaller agents and particles with low solubility do get through.

Exercising itself is not efficient in air filtration: breathing through the mouth lets more pollutants reach the lungs. We breathe deeply when exercising, therefore inhaling more noxious fumes into the lungs.

Following the millions of pollutants into the body

When the body is exercising and breathing more deeply in urbanised areas where fresh air is scarce, pollution misses the body’s first line of defence against outside agents penetrating the body – the nose.

The lungs are one of the body’s first internal organs in contact with the outside world. We may drink about two litres of liquid a day, but the lungs take in 15,000 litres of air. That is about six to ten litres a minute from across 600 to 900 square feet area into tiny sacs inside the lungs.

One of the reasons to exercise is to improve the body’s ability to deliver oxygen to itself, and the body needs oxygen for muscles to function. Therefore, when we exercise we take in more of it. In fact, we inhale ten times as much than when we rest.

Some endurance athletes can possibly breathe in 20 times as much as when resting – but what no exerciser wants to do is bypass the nose.

Some studies suggest that exercising in polluted areas isn’t a good thing at all.

A study in the journal Circulation: Journal of the American Heart Association says that exercise should be completely avoided on hazy days.

Some researchers have suggested a link between pollution and increased risk of heart attacks.  The study conducted in Finland claim to be the first to examine heart strain during exercise. It revealed a decreased oxygen supply to the heart muscle when air pollution is high.

Senior researcher Dr Juha Pekkanen, of the National Public Health Institute, Unit of Environmental Epidemiology said: “People with heart disease were about three times more likely to have decreased oxygen supply to their heart muscle during exercise after periods of high level air pollution than when they were tested after periods of negligible air pollution.”

This study suggests that sufferers of heart disease should be more than vigilant to avoid days of high pollution. Oxygen has to travel to more places than the lungs.

The extent of pollutant damage

ACE (American Council on Exercise) Chief Exercise Physiologist Dr Cedric X. Bryant reports how far pollutants reach to cause different bodily damage.

In the short term, she reports, the main problems are an irritation of the upper respiratory tract causing respiratory discomfort and reduction in how much oxygen is carried in the blood.

Carbon monoxide (CO2) emission mostly affects exercise performance by being a stronger gas than air. Its capacity to bind to haemoglobin (COHb) reduces the blood’s ability to transport oxygen to the tissues.

However, very high levels of COHb would be needed to reduce exercise performance.

Sulphur oxides can influence through irritation of the upper respiratory tract, which can cause reflexive bronchoconstriction and increased airway resistance. Nose breathing can significantly reduce this affect, however.

Acute exposure to nitrogen oxide (NO2) has been observed to be extremely dangerous. High exposure to NO2 has not been fully studied, but it has been reported to be a leading cause in some fatalities.

Ozone (O3) is another particularly dangerous pollutant where it is thought to do its worst over a long period of time, such as several hours.  Such exposures lead to decrements in pulmonary (lung) function and increased subjective discomfort.

The resulting respiratory discomfort can limit performance when it is severe. Ozone has also been linked to eye irritation and nausea.

Aerosols can have a psychological effect by being an airway irritant. The most common aerosols are sulphates, sulphuric acids, nitrate aerosols and saturated and unsaturated aldehyde, most of which have a minimal effect.

Soot, dust, lead and smoke had not been tested.

Researchers at Beth Israel Deaconess Medical Centre and Harvard Medical School in Boston have stated that oxygen deprivation to the heart muscle has significant potential to be responsible for “adverse cardiac outcomes associated with poor air quality.”

Researchers studies 23 volunteers living in Helsinki, Finland, during the winter. Each was put on an exercise bicycle ‘ergometer’ for intervals over six months while their heart was monitored.

The team reported an increased risk of decreased oxygen to the heart after periods of increased fine and ultra-fine particles in the air.

The fine particles were mirrored on emissions from factory smokestacks, and the ultra-fine were a type of pollutants that are expels from exhaust pipes.

Dr. Murray A. Mittleman, director of cardiovascular epidemiology at Beth Israel, said: “It's better for heart patients to exercise in air-conditioned settings compared to the outdoors when pollution is high.”

Minimise risk to maximise health

Exposure to pollution can be avoided by following some simple rules, and those exercising in urbanised areas susceptible to air pollution should be extra cautious.

Training should be conducted early in the morning or in the evening when polluters, such as cars and factories, are expelling less fumes.

Therefore, avoid midday or afternoon exercise. Pollution levels reach their maximum in the afternoon. In fact, avoid congested streets and peak hour traffic altogether.

Smog is also at its worst between May and October. It pays to be extra alert at this time of year, and be particularly watchful in the heat of summer. Therefore, avoid combinations of high temperature, humidity and air pollution, especially.

If you exercise with others and have a coach or a teacher, make sure they are aware of the effects of air pollution and act accordingly.

Cigarette smoking before exercising is also very harmful.

Always be aware of the air you breathe. Weather reports often detail what the pollution levels are like outside. Valuable information can be sought from meteorologists to minimise the harmful effects of exercising in polluted areas.

Keep the amount of time spent in highly polluted areas to a minimum. The physiological (and psychological) effects of air pollution are dependent on the time and dose of it.

Exercise may increase the respiratory rate but it also aggravates contamination in the lungs, heart and blood stream. Activities should be planned taking daily and seasonal factors into consideration.

Exercise is good for you so try not to hinder its benefits by not paying attention to the pollution outside.

Further reading

American Lung Association
London Air Quality Network
BBC Weather Centre

 

You’ve read it. Now review it.