Major Air Pollutants

We all "know" that air pollution is bad for our health and have accepted a whole series initiatives imposed by the Government aimed at reducing it. We have accepted the banning of backyard burning. We have accepted the introduction of unleaded petrol and catalytic converters on our cars and many other engine design changes, even though they increased the cost of our cars. We have been grateful to find that these actions have actually resulted in some reductions of air pollution levels with both carbon monoxide and lead levels in the air falling to roughly one third their previous levels. They are continuing to fall but at a slower rate.

Although this fall is thought to have had a measurable effect on general health, it is still the sad fact that our air is continuing to make us sick. The main cause of this is thought to be the increasing levels of ozone, volatile organic chemicals, nitrous oxide and particulate matter present in the air we breathe.

The component of most concern appears to be fine particulate matter (PM2.5). A major source of fine particulate matter in city air is diesel exhaust which contains carbon particles carrying toxic and carcinogenic organic materials such as benzene, complex sulphur and nitrate containing organic materials and reactive ozone type compounds formed under the action of sunlight.

Particulate matter is known to cause increases in death rates and hospital admissions round the world. What is lacking is an understanding of the mechanism by which this happens and the Clinton administration provided $500-600 million per year over ten years to find out what is causing 15,000 premature deaths a year in the US and to " identify and evaluate … biological mechanisms by which PM causes death and disease in humans."

Other air pollution components which are not in significant decline and therefore in need of attention are the oxides of nitrogen, formed in ever greater quantities as car and truck engines become more efficient and sulphur dioxide from high sulphur fuels. Volatile organic compounds are under attack through a number of initiatives to limit release and decrease use.

International and local evidence is over-whelming that such air pollutants present a serious and costly health hazard. In September 2000, a ‘Lancet’ editorial reported a recent study across Austria, France and Switzerland, that showed the health costs of air pollution from traffic were 1.7% of the gross domestic product and exceeded the cost of motor vehicle accidents. Dr Dockery, author of the landmark ‘6-cities study’ in US, observes that the question is not whether particulates are harmful, but at what level, and the levels are much lower than previously thought.

A particularly clear indication of the extent to which vehicle based air pollution effects health was observed in Atlanta during the Olympic games in 1996. Over the games period, air pollution in Atlanta was reduced by about 20% with reductions in ozone, carbon monoxide, particulate matter and nitrogen dioxide. Over the same period hospital admissions for childhood asthma dropped by 44%, even though mould spores, the other potential major cause of asthma in Atlanta did not change significantly. Other, non respiratory, hospital admissions did not change markedly, showing the reduction was not caused by people leaving the city. In general, the pollution levels experienced in Atlanta over the whole of the study, before, during and after the games, were similar to those experienced in Sydney during the year. The RTA predicts that the M5East stack will cause increases in particulate matter and nitrogen dioxide in areas near the stack, similar to or greater than those experienced in Atlanta, It follows that the stack will cause increases in asthma attacks (and other respiratory illnesses) in those areas.

As many people die in Sydney from air pollution as die in road crashes. The only difference is they die slowly, and away from public view. Thousands regularly suffer breathing difficulties, increased asthma and heart conditions. Increased use of medication, hospitalisation and absenteeism are costs borne by the whole community, not just the individuals and families involved.

Almost all chemicals find their way into the air. But many are released in such small amounts that they are not a health concern. Some substances are so common and widespread they build up in the air and become a hazard to human health.

Exposure to air pollution can make your eyes water, irritate your nose, mouth and throat, and make you cough and sneeze. But more important, it can also worsen and may cause lung disease like asthma, bronchitis and emphysema. In some cases, it can even contribute to the premature death of people with heart and lung disease.

Health effects: Carbon monoxide interferes with the blood's ability to carry oxygen to the brain, heart and other tissues, and it is particularly dangerous for people with existing heart disease, and unborn or newborn children.

Ozone (O3) is the major harmful ingredient in smog. It is not emitted directly into the air but produced in the atmosphere when gases or vapours of organic chemicals called hydrocarbons combine with nitrogen oxide compounds in the presence of sunlight. Organic hydrocarbon gases, one of the raw ingredients of ozone, are released from a variety of sources related to human activities. Major sources include refineries, gas stations, motor vehicles, chemical plants, paints and solvents. Harmful ozone in the lower atmosphere should not be confused with ozone in the upper atmosphere, which protects us from ultraviolet radiation.

Health effects: Ozone reacts with lung tissue. It can inflame and cause harmful changes in breathing passages, decrease the lungs' working ability and cause both coughing and chest pains. Ozone air pollution, found at unhealthy levels in nearly all of the nation's major urban areas, may particularly affect millions of otherwise healthy Americans who, for currently unknown reasons, are especially sensitive to it. People who exercise are also more vulnerable to the effects of ozone, suffering symptoms and a reduced ability to breathe at relatively low ozone levels. Ozone pollution, even at low levels, has also been linked to increased hospital admissions and emergency room visits for respiratory problems.

Nitrogen dioxide (NO2) and related nitrogen oxides (NOx) are produced when fuel is burned, especially in power plants and motor vehicles. These oxides of nitrogen compounds contribute to ozone formation, and are a health problem themselves. NO2 also changes in the atmosphere to form acidic particles and liquid nitric acid.

Sulfur dioxide (SO2) is created when sulfur-containing fuel is burned, primarily in power-plants and diesel engines. Like NO2, sulfur dioxide can also change in the atmosphere into acidic particles and into sulfuric acid.

Health effects: Sulfur dioxide constricts air passages, making it a problem for people with asthma and for young children whose small lungs need to work harder than adult lungs. Even brief exposure to relatively low levels of sulfur dioxide can cause an asthma attack.

Particulate matter (PM) includes microscopic particles and tiny droplets of liquid. These particles come from the burning of fuels by industry and diesel vehicles and from earth-moving activities such as construction and mining.

Health effects: Larger particles can be stopped in the nose and upper lungs by the body's natural defences. The smallest particles escape the body's defences and go deep into the lungs, where they may become trapped. Exposure to particulate pollution can cause wheezing and other symptoms in people with asthma or sensitive airways. Particulate pollution has been linked to increased hospital admissions and emergency room visits for respiratory problems and to a substantial increase in premature deaths.

Lead (Pb) has been known as a poisonous substance for many years. Due to past major reductions and now the elimination of lead in gasoline, there has been a significant decrease in public exposure to lead in outdoor air. Remaining air pollution sources include lead smelters, incineration of lead batteries, and burning lead-contaminated waste oil. However, the most common sources of current lead exposure are indoors from old lead-containing paint and soil.

Health effects: Exposure to high levels of lead can damage the blood, brain, nerves, kidneys, reproductive organs and the immune system. Lower levels that are more commonly associated with current exposures can result in impaired mental functioning and development in children and raising blood pressure in middle-aged men. Lead accumulates in the body, so repeated small doses can be harmful.

In addition to these six pollutants for which air quality standards have been set, toxic air pollution, also referred to as hazardous air pollution, consists of those substances in the air which are known or suspected to cause cancer, genetic mutation, birth defects or other serious illnesses in people even at relatively low exposure levels. Toxic and cancer-causing chemicals can be inhaled directly or carried by small particles into the lungs. Millions of pounds of these chemicals are emitted into the air over our nation every year by motor vehicles and by both large and small industry.