This afternoon I asked Google to define pollution. There were many definitions given but most of them focused on the following aspects:

• Caused by the actions of man
• Changes the natural environment
• Contamination of a natural resource
• Degrade the natural quality of the environment
• Harmful to the environment
• Harmfully affect the health, survival, or activities of humans and other living organisms
• Impairing the quality of the environmental resources and reducing amenities.
• Impurities and waste in the environment
• Occurs when the rate of materials entering the natural environment exceeds natural levels.
• Offends the senses of sight, taste, or smell, or cause a health hazard
• The results of activity that is detrimental to beneficial use by plants, animals or humans of water, air or land
• Usefulness of the natural resource is usually impaired by the presence

These definitions varied from source to source, depending on what aspect the author wanted to focus on pollution. Ag schools were concerned about farm run-off, the EPA about air and water pollution, environmentalists about general environmental degradation. All of them were incorrect in certain contexts but were correct in others.

Taking all those definitions together one could define pollution as follows:

Any activity that produces a result that is obnoxious to another person or group.

The pollution might be largely psychological or it might have impacts on our resources. There might be a need to regulate pollution or prohibit people from engaging in certain activities. That is a political question that needs to be answered by our political system.

Let's break down this definition further.

Any activity – Literally any activity produces a change on the environment whether or not we are conscience of it. Yet, the change might be so small compared to the natural environment around us that it doesn't appear as pollution. Turning on your car releases dozens of toxic and non-toxic but polluting substances like carbon dioxide.

Produces a result – Activites of any sort inevitably produce is a result. But is that result obnoxious and essentially intolerable on the other hand? Starting a car up might release pollution but is it really pollution in a forest of trees where the trees have a far greater impact then starting up a car?

Obnoxious - It's annoys somebody or has a negative impact on their lives or livelihood. There are a variety of degrees and people can disagree with the obnoxiousness of any specific pollutant.

Another person or group – Pollution doesn't typically occur to the person who is polluting. It usually impacts another individual who believes an act is essentially intolerable. You wouldn't be riding your snowmobile if you felt that the 2-stroke engine exhaust

With pollution context is everything. It must be perceived as pollution (see the Psychology of Pollution) and it must have a negative impact on an area. Wood smoke in a rural area where there is few sources of pollution might not be pollution unless it becomes at a level that is essentially intolerable.