Pollution is mainly a byproduct of human activity. Industrial manufacturing, the use of automobiles, power production, mining and war are all significant sources of environmental pollution.
Pollution can be roughly divided into several groups. Air pollution is caused by the release of particulate matter and chemicals into the air, usually by way of gases. Soil pollution is caused by the dumping or accidental spill of chemicals or toxic materials into landfills and waterways. Water pollution is caused by sewage discharge and industrial waste water discharge as well as chemical dumping and spills. Radioactive contamination is a byproduct of the creation and use of nuclear power and nuclear weapons.
A leading source of air pollution is carbon dioxide emissions from the use of motor vehicles. Other major contributors are the byproducts of industrial processes like mining, manufacturing, construction and certain aspects of agriculture. Power production by way of burning coal is also a significant contributor to air pollution. Soil pollution comes from a wide variety of human sources such as the spraying of pesticides and herbicides, dumping of heavy metals and hospital wastes, and fuel spills. Chemicals and toxins can also leach into the soil through landfills. Many of these same sources also cause pollution of ocean waters.