If someone told us there was an insidious problem within our society that killed 3,000 people per year we would be outraged and determined to do something about it. This problem is not about car fatalities, shark attacks, inactivity or drug overdoses…its simply air pollution.
The Australian Institute of Health and Welfare estimated that urban air pollution was responsible for more than 3,000 premature deaths in 2003. Over the past 14 years the air quality had improved markedly but could easily be reversed with our ongoing reliance on coal fired power generation and the population growth so dependent on the increasing use of motor vehicles.
Still, it has been reported that long-term city dwellers could have their lives reduced by 72 days for men and 65 days for women as a result of continually breathing in fine particles. This is an interesting statistic given more people are now moving back to live and work in the city.
In a Scottish study 30 healthy men who rode their bikes daily to and from work while exposed to diesel fuel emissions presented with constricted blood vessels and reduced action of an enzyme responsible for breaking blood clots in the heart. In another study competitive cyclists who were exposed to different levels of air pollution (ozone) while exercising, decreased their endurance by approximately 30% and their lung function by 22%.
A 2010 study in the Netherlands estimated that short daily trips cycling in polluted cities can reduced their life expectancy from .8 to 40 days.
Even the Sydney Morning Herald in August 2014 reported in a lead article: “Sydney’s air kills more people than car accidents”.
Sydney air consists of two different types of air pollution. Primary pollutants include carbon monoxide, sulphur oxide, nitrogen oxides, hydrocarbons and particles from dust, smoke and soot.
Secondary pollutants include those that come directly from our environment including sunlight, moisture and other pollutants that react with the primary pollutants.
Outdoor pollution is strongly related to industry and population density. Major contributors to carbon monoxide include cars, buses, truck, planes and the combustion of fossil fuels.
Vehicle pollution accounts for approximately 70% of our poor air quality. While the pollution from cars has reduced over the past 20 years, there has been an increase in diesel-powered vehicles. It is the tiny soot particles from these diesel exhausts that are now causing some of the biggest problems. These very small particles can find their way into our bloodstream where they can contribute to clot formation and hardening of the blood vessels.
Is this a problem given the dramatic increase in outdoor fitness sessions, active transport, leisure time and free-living physical activities?
We actively encourage children and adults alike to go outside and walk more, cycle more and run more either in a structured fitness session, active transport, outdoor household activities or free-living activity.
Globally, 52% of people live in urban areas while in developed countries this figure increases to 78%. This means that exercising outdoors might increase exposure to urban air pollution and could affect the positive benefits of being physically active.
Different forms of active transport is also affected by exposure to air pollution. For example, cyclists travelling in the bike lane in major urban areas might be exposed to smaller particle matter than pedestrians, possibly due to their proximity to the traffic. It is also possible that commuters in buses and cars in these urban areas are also being exposed to poorer air quality because they sit in an environment of limited circulating ventilation.
Walkers, bikers and runners who exercise in urban environments before work, at lunchtime or after work could also be placed at risk. When we leave home and start exercising our breathing increases up to 15 times more than at rest, which allows more fine polluting particles to progress deeper down our respiratory system.
Short-term symptoms to pollution exposure include: sore throat, coughing, scratchy throat, headache, chest pains and watery eyes. Just because we don’t experience any of these symptoms doesn’t mean that we are exempt from the problem.
The effects of this exposure to air irritants while moving at low intensities might be minimal to our health but it does affect our overall physical performance. The greatest decrease in performance and health is when exercising at high intensities.
There are a number of physiological changes that take place when exercising in a polluted environment. When exercising at low intensities we tend to still breathe through our nose, which filters many of the airs irritants. Once the intensity increases there is an increase in breathing through the mouth increasing the pollutant dose into our lungs. The small hairs in our nasal passage generally filter air before it gets into the lungs.
The faster breathing rate increases the proportion of fine particles that move down the airways and are not exhaled easily. This can cause an inflammation of the lung tissue that can affect the airway antioxidant defences and increase airway resistance by constricting the air passages, making it harder to breathe.
At the beginning of exercise we start to breathe faster and deeper and then as a means of trying to protect our lungs we start to breathe less, trapping gases in the airway dead space and setting up a potential competition for blood between the skeletal muscles and the muscles responsible for breathing. Our air passages tighten and our breathing becomes much more laboured. Our cardiovascular and respiratory systems start to strain in an attempt to feed our muscles with the required amount of oxygen they are demanding.
The ingestion of these fine particles can also affect the cardiovascular system.
Carbon monoxide has a strong affinity for haemoglobin found on the red blood cell. Carbon monoxide has a 200-250 times greater affinity for haemoglobin (Hb) than oxygen reducing the oxygen carrying capacity of the blood.
As we need oxygen to burn fuel for the supply of energy the heart must beat faster (heart rate) and with more blood (stroke volume) in order to get the required amount of oxygen to the tissues.
If the blood and the oxygen don’t reach the tissue there is a chance of tissue hypoxia or lack of oxygen to the cells.
When oxygen delivery to the cells is reduced there is an increase in the production of free radicals, which causes the cells to become inflamed impairing their basic functions.
The effects of air pollution can last for hours even after the exercise session has finished.
In those with existing coronary heart disease exposure to air pollution can potentially cause myocardial infarctions, irregular heartbeats as well as affect the lining of the arteries.
Overall exposure to air pollution in our urban environments should always be a consideration when planning outdoor activities, particularly when the session is intense.
Low levels of fitness and obesity further increase the potential risks from exercising in a polluted environment.
We should always limit our exposure to polluted air in all our physical activities.
Some risk management strategies might include: being aware of the pollen count or pollution levels forecast on the day of exercise, pre treatment for asthmatics to protect against the reduced oxygen levels, exercising in the morning and avoiding mid and late afternoon, exercise as far away from traffic or industry as possible, exercise close to trees and gardens, wear a mask, identify people at risk, avoid smoky areas before the session starts, exercise indoors if the air quality is too poor, always avoid morning and afternoon rush hours, select the days to exercise at a higher intensity e.g. Sundays, exercise at low to moderate levels of intensity on poor air quality days, stay indoors or reduce the time outdoors, limit any exercise on polluted days, if cycling or walking don’t get behind polluting vehicles.
Those bike couriers delivering goods around town with their masks on might not be so geeky after all…