What is air pollution?
Air pollution occurs when activities by humans causes the release of substances, vibrations, noise, light or heat into the surrounding environment, where these emissions cause harm to people and wildlife or damage to property or amenities used by people.
In terms of substances, these usually take the form of chemicals, particulate matter and biological materials.
What are the causes of air pollution?
Although air pollution can be caused by natural means such as dust, animals, volcanic activity, wildfires and radioactive decay of the Earth, the main sources of harmful gases, smoke and dust that are emitted to the atmosphere by human activities are; power stations, waste incinerators, motor vehicles, quarries, landfills, fumes from solvents, military activities and industrial processes.
The quality of air can be made worse by certain weather conditions. One of the most common scenarios is a temperature inversion when polluted air may be trapped at ground level under a layer of warm air on a calm, sunny day. This is the cause of extreme smog in places like Los Angeles, where the dirty air released by large numbers of cars becomes trapped by warm air above.
The main pollutants include sulphur and nitrogen oxides that are emitted by anything that is burning carbon based fossil fuels such as oil or gas. Carbon monoxide is a poisonous gas mainly emitted by vehicle exhaust fumes. Volatile Organic Compounds (VOCs) are also important, including gases like methane. A major source of them is paints and protective coatings. Particulate matter (tiny particles of solid or liquid suspended in gas) – again caused by the burning of fossil fuels in vehicles and power plants – is also significant. Carbon-dioxide, although occurring in natural quantities, is also released by respiration, combustion and cement mixing. Other pollutants released in lower quantities include Chlorofluorocarbons (CFCs – now banned from use), ammonia (from agricultural processes), radioactive pollutants (from nuclear processes and war), toxic metals (cadmium, lead, copper) and odours from sewage, rubbish or industrial processes.
What are the human health effects of air pollution? Does air pollution cause asthma?
There is lots of evidence to support the idea that air pollution is strongly linked to human health problems. This is especially the case in urban areas.
Particulate matter has been linked to heart disease, lung cancer, altered lung function, and asthma. Man made VOCs can cause eye, nose and throat irritation, headaches, nausea, damage to kidney, liver and the central nervous system. Although VOCs are not toxic in small amounts, the issue is of the long-term compounding effects of exposure. For this reason it is quite difficult to get hard evidence to support any links. Nitrogen dioxide is toxic by inhalation but this is rare. Of course, “smelly” odours are also very unpleasant and must therefore be classified as pollution, but whether this should be considered a legitimate health effect is another matter.
There is certainly a belief that air pollution contributes to increasing incidences of childhood asthma. Recent studies show a relationship, but like all research, it is an ongoing process of providing evidence to support the theory that is difficult to determine for sure because of the complex interaction of other causes of asthma such as genetic factors and allergies.
Noise pollution is another type of air pollution, but is discussed separately on this website.
What are the environmental effects of air pollution?
The most notorious environmental effect is the issue of climate change. Whilst recognising that there is a lot of argument against man-made climate change being true, the logic of how it might occur is as follows. Burning fossil fuels and the clearing of carbon sinks such as peat bogs and forests cause the release of carbon dioxide to the atmosphere. This atmosphere has a natural balance of so-called greenhouse gases including carbon dioxide, methane, CFCs, water vapour, nitrous oxide and ozone that keep the planet warm. The release of extra carbon dioxide causes a change in the delicate balance of these gases and traps heat that would normally escape back into space. This is the concept popularly termed as Global Warming.
Although climate change also happens naturally, nonetheless the possible effects are potentially damaging to humans and wildlife alike. For example, a change in weather patterns would affect agriculture and food production; melting ice-caps would cause sea-levels to rise and affect coastal and low-lying areas, reducing fresh water supply as well as destroying agriculture, urban areas and installations such as power stations. Animals would migrate to where they can survive best or else become extinct. And diseases such as malaria that are only found in hot areas would potentially become more pervasive.
Ozone layer depletion is another important effect. Ozone is a gas that forms a layer high up in the atmosphere and protects the Earth’s surface and human beings from the sun’s harmful ultraviolet light rays. These rays can cause skin cancers in humans. The main causes of this depletion are CFCs and other human-made gases like halons. Fortunately CFCs have been banned around the world, whereas not so long ago they were prevalent in aerosols, refrigerators, air conditioning and fire extinguishers.
Acid rain is another issue. Although rain water is naturally slightly acidic, when it reacts with oxides of sulphur and nitrogen it becomes even more acidic. This rain is very toxic to plants and so when it falls it can kill vast swathes of forest or vegetation. Also, when this acid filters through soil or freshwater, it releases other naturally stored metals such as lead and aluminium that themselves are toxic to fish and vegetation. Finally, the corrosive effect of the acid can cause damage to man-made structures made of alkaline rocks like limestone, or metal features.
Conclusion
Air pollution, along with water and land, is an increasingly important issue for human beings to face. Although the writing above may seem to show environmental effects to be greater than human health ones, one must realise that all of the environmental issues will and are affecting humans down the line. The secondary effects of something like climate change will affect our whole survival system in terms of food production, freshwater supplies and where or where not we can live. The health effects of those issues would be huge, even if climate change turns out to be a completely natural phenomenon!