Pollution is the introduction of any substance into an environment that causes harm, whether it be physical, chemical or biological. This can happen in a variety of ways, including through the disposal of waste, by burning fossil fuels or through the use of hazardous chemicals. The contaminant can be either a solid, liquid or gas and may also include radiation and electromagnetic waves.
Many types of pollution are caused by the disposal of chemicals into the environment by factories and agribusinesses. Other forms of pollution are caused by burning fossil fuels, and by air, water or land pollutants that travel into the atmosphere. These atmospheric pollutants can then fall back to earth as acid rain, contaminating soils and oceans.
Most people are exposed to a variety of types of air pollutants that can cause negative health impacts. Fine and ultrafine particulate matter (PM2.5) enters the lungs, and travels into the bloodstream, where it can affect major organs such as the lungs, heart and brain. Prolonged exposure to PM2.5 can lead to disease and even death. Air pollutants are also a significant contributor to climate change.
The most common forms of air and water pollution are the result of human activity. Industrial emissions, such as carbon dioxide, methane and nitrous oxide, contribute to air pollution. The addition of these gases into the atmosphere can reduce the amount of sunlight that reaches earth, leading to an increase in global temperatures. Water and air pollution can also be caused by toxic chemical spills, which can harm humans and wildlife. Pollution has a disproportionate impact on the poorest people because polluting industries and toxic waste sites often are located near populations with less economic and political power.