"Explain pollution to a visitor from another planet."

Pollution is contamination by a chemical or other agent that renders part of the environment unfit for intended or desired use. These uses also and very importantly include all wildlife and ecological requirements to sustain life in all its natural forms.

Pollution damages the Earth's land, water and air. It results in contamination of the earth's environment with materials that interfere with human health, the quality of life, and the natural functioning of ecosystems (living organisms and their physical surroundings).

Pollution is usually caused by human actions, but can also be the consequence of natural disasters. Pollution can also occur from disruption or damage to wastewater collection and treatment infrastructure due to severe natural events like hurricanes or flooding. Most types of pollution affect the immediate area surrounding the source, and reduce as you move away from the source.

Pollution is often caused by the garbage that people throw on the ground or into oceans, lakes or rivers.

Pollution exists in many forms and affects many different aspects of the Earth's environment. Some main types of pollution are:-

- Water pollution is a serious global problem and the largest water pollution problem is from sewage contaminating watercourses.

- Air pollution arising from many sources, and is bad in cities. Car transport emissions causes a lot of the air pollution we see. But did you know that air pollution also can exist inside homes and other buildings? Poor ventilation causes about half of the indoor air pollution problems. Air pollution contributes to the greenhouse effect.

- Highway vehicles, and shipping, are major contributor to air pollution worldwide.

- Photochemical air pollution is commonly referred to as 'smog'. Urban air pollution is often caused by a photochemical, and is commonly known as smog.

- Radioactive pollution results from inadequate nuclear safety.

- Light pollution, includes light trespass, over-illumination and astronomical interference.

- Noise is a form of pollution as well but is unlike the others as it is transient; once the pollution stops, the environment is free of it.

Recently, there has been a heightened interest in the intercontinental transport of pollution. European pollution has been tracked to Asia, as well as the Arctic.

Pollution control involves higher production costs for the industries concerned, but failure to implement adequate controls may result in irreversible environmental damage and an increase in the incidence of diseases such as cancer.

Pollution can be achieved by reducing or eliminating waste at the source by modifying production processes, promoting the use of non-toxic or less-toxic substances, implementing conservation techniques, and re-using materials rather than putting them into the waste stream. But even with these new laws air pollution is still on the increase overall throughout the world. This is especially so in the developing countries.

We should all do what we can to minimize pollution and become 'green'.