Every living thing pollutes. Life is a chemical reaction, where input chemicals such as food and oxygen are converted into growth or motion. The reaction bi-products are waste or pollution.
The only way to totally eliminate pollution is to eliminate life — not a particularly appealing option. However, a system of world-wide population control could stem the increase of pollution, allowing residents of our planet to enjoy a high quality of life.
Is pollution bad? From an anthropocentric point of view, we might say “yes”. To do so, however, would deny our dependence on pollution. In the Earth’s original atmosphere, there was very little oxygen. Oxygen is believed to have formed as pollution from plant life. Without this pollutant, animals such as humans would likely not exist now.
However, it is reasonable to worry about other chemicals that threaten our quality of life. We call such chemicals pollutants, regardless of whether they form naturally or anthropogenically (man-made). Many of the natural sources are weak emissions from large area sources, such as forests or swamps. Anthropogenic sources are often concentrated at points, such as at the top of smoke stacks (Fig. 19.1). Such high concentrations are particularly hazardous, and been heavily studied.