Pollution

It's been said before, but here's one of the many lists of motor vehicle pollutants that's doing the rounds:


 * Nitrogen oxides: These are created when vehicle engines burn nitrogen that is present in the air and nitrogen compounds found in fossil fuels. Nitrogen oxides can irritate airways, especially your lungs.
 * Carbon monoxide: This gas is produced by incomplete combustion of gasoline and diesel fuel. All engine exhaust contains a certain amount of carbon monoxide, but the amount will increase if your vehicle engine is poorly maintained. Carbon monoxide decreases the ability of your blood to carry oxygen.
 * Volatile organic compounds (VOCs): These are a large family of carbon-containing compounds that evaporate easily. Engine exhaust contains a number of different VOCs. Some of them, such as benzene and 1,3-butadiene, are cancer-causing agents, although the risk at current levels in the environment is small.
 * Fine particulate matter: These tiny particles contain many substances, including metals, acids, carbon, and polycyclic aromatic hydrocarbons. Some of these particles are emitted in vehicle exhaust, while others are formed in the atmosphere through chemical reactions between the various pollutants found in exhaust. Particulates are known to aggravate symptoms in individuals who already suffer from respiratory or cardiovascular diseases.
 * Ground-level ozone: This is not emitted directly by vehicle engines, but is formed by chemical reactions between nitrogen oxides and VOCs. These reactions are stimulated by sunlight, and this is why concentrations of ground-level ozone are higher during the summer months. Ground-level ozone irritates airways and can trigger reactions in people who have asthma.
 * Ground-level ozone should not be confused with the ozone layer in the stratosphere, which provides protection from the sun's ultraviolet rays.

The air pollution from road traffic causes two types of effects on health:
 * Acute Effects: These effects occur rapidly (in a few hours or days) following exposure to high levels of pollutants. In certain cases, air pollution may worsen symptoms for people with existing heart and lung conditions. Scientific research carried out in Canada and in other countries has shown that the number of deaths and hospitalizations related to respiratory and cardiac conditions increases when the levels of ground-level ozone or fine particulate matter increase.
 * Chronic Effects: These occur over time following extended exposures (months or years). Scientific studies in Europe have shown that children living in areas with higher traffic density have more respiratory symptoms than other children.