Causes of Air Pollution

Air pollution is one of the most visible forms of pollution. Anyone who's seen the brownish-yellow sky over a city, or dark smoke belching from the tail pipe of a bus or industrial smoke stack knows what it looks like. It's effects are not always so obvious, and range from contaminated rain to ozone levels to global warming. There are also health concerns, making air pollution a serious environmental concern.

Air pollution is essentially the introduction of particles into the atmosphere that does not belong there. Particulate matter, tiny pieces of contaminants, which because they are lighter than air become airborne. They might then rise high into the air to travel on the winds, or float near ground level. This is a result of both the kind of pollutant and where it is released. Car exhaust, for example, starts much lower than industrial smoke. Air pollution does not have to be man made chemicals. The desertification of wilderness areas releases extra dust and sand into the air that also causes many of the problems associated with chemical air pollution.

Air pollution may be caused by various natural and anthropogenic processes. Below are listed some of the main air pollution causes.

NATURAL:

• Volcanic activities – volcanic eruptions emit a serious of toxic gases (including sulfur and chlorine) as well as particulate matter (ash particles) but are usually restricted to localized areas;

• Winds and air currents – can mobilize pollutants from the ground and transport them over large areas;

• Wildfires – add to the atmosphere smoke, carbon monoxide as well as particulate matter (containing organic contaminants such as PAHs) and could affect significant areas although in general are restricted and may be contained;

• Microbial decaying processes – microorganisms which are present in any environment have a major role in natural decaying processes of living organisms as well as environmental contaminants; this activity results in the natural release of gases especially methane gas;

• Radioactive decay processes – for example radon gas is emitted due to natural decay processes of Earth’s crust which as potential to accumulate in enclosed spaces such as basements;

• Increasing temperatures – contribute to an increase in the amounts of contaminants volatilizing from pollution soil and water into air.

ANTHROPOGENIC:

• Mining and smelting – emit into the air a variety of metals adsorbed on particulate matter that is suspended in the air due to crushing & processing of mineralogical deposits;

• Mine tailing disposal – due to their fine particulate nature (resulting after crushing and processing mineral ores) constitute a source of metals to ambient air which could be spread by wind over large areas;

• Foundry activities – emit into the air a variety of metals adsorbed on particulate matter that is suspended in the air due to processing of metallic raw materials (including the use of furnaces);

• Various industrial processes may emit both organic and inorganic contaminants through the following mechanisms:

1. Accidental spills and leaks of stored chemicals
2. Handling and storage of chemicals – especially of volatile inorganic chemicals

• Transportation – emits a series of air pollutants (gases – including carbon monoxide, sulfur oxides and nitrogen odides - and particulate matter) through the tailpipe gases due to internal combustion of various fuels (usually gases such as opxides of carbons, of sulfur, of nitrogen, as well as organic chemicals as PAHs)

• Construction and Demolition activities – pollute the air with various construction materials. Of special threat is the demolishion of old buildings which may contain a series of banned chemicals such as PCBs, PBDEs, asbestos.

• Coal Power Plants – by burning coal they may emit a series of gases as well as particulate matter with metals (such as As, Pb, Hg) and organic compounds (especially PAHs);

• Heating of buildings – emits a series of gases and particulate matters due to burning of fossil fuels;

• Waste Incineration – depending on waste composition, various toxic gases and particulate matter is emitted into the atmosphere;

• Landfill disposal practices – usually generate methane due to intensification of natural microbial decaying activity in the disposal area;

• Agriculture – pollute the air usually through emissions of ammonia gas and the application of pesticides/herbicdes/insecticides which contain toxic volatile organic compounds;

• Control burning in forest and agriculture management – includes controlled burning that will emit gases and particulate matter (similar to wildfires described above)

• Military activities – may introduce toxic gases through practices and training;

• Smoking – emits a series of toxic chemicals including a series of organic and inorganic chemicals, some of which are carcinogenic;

• Storage and use of household products such as paint, sprays, varnish, etc that contains organic solvents which volatilize in the air (hence the smell we all feel while using them);

• Dry cleaned clothes - may retained and emit in the atmosphere small amounts of chlorinated solvents (such as PCE) or petroleum solvents that have been used by the dry cleaners; this could eventually create a health risk if the clothes returned from the dry cleaners are stored in enclosed indoor spaces.