Point-source pollutants include toxic chemicals, heavy metals, nutrients, organic matter, bacteria, viruses and airborne particulates. Impacts vary widely. Many pollutants poison wildlife and can be extremely hazardous to humans. Others can disrupt animal reproductive systems, damaging species populations and disrupting ecosystems. Nutrient pollution, often resulting from agricultural runoff, can cause toxic algae blooms and depletion of dissolved oxygen in waterways. Bacteria and viruses can cause disease in wildlife, plants and humans. In most cases, significant levels of pollution disrupt ecosystems, leaving them less suitable for supporting life.
Sewage treatment effluent and storm drain discharge are two major forms of point-source pollution in cities and towns. During sewage treatment, most solids, heavy metals, chemicals, bacteria, viruses and nutrients are removed, leaving an effluent that still contains some pollutants. This effluent is usually released directly into public waterways. In many cities, storm drains do not link to treatment facilities, but rather drain directly into waterways. Storm drain runoff can contain industrial chemicals, petrochemicals from roads, fertilizers, pesticides and any number of other pollutants that may be dumped into the drain. These sources can lead to significant pollution levels in local rivers and lakes.
The Environmental Protection Agency regulates industrial point-source pollution in the United States and prescribes treatment requirements for individual industries. Most industrial pollutants are toxic metals, such as lead and mercury, and toxic organics such as pesticides, solvents, dioxins and petrochemicals. Industrial sources are the second leading point-source contaminators, after municipalities. Oil spills represent a significant form of industrial pollution. Industrial point-source pollution is usually damaging to plant and animal species, and it disrupts ecosystems. Many industrial pollutants can remain in the environment for decades or longer.
Point-source air pollution is a product of large-scale industrial facilities such as power plants, refineries, paper mills and chemical processing operations. Under the Clean Air Act, the EPA regulates emissions of six key air pollutants: particulate matter, sulfur dioxide, carbon monoxide, lead, nitrogen dioxide and ozone. Although EPA regulations have helped to significantly reduce air pollution, sulfates from coal-fired power plants remain a significant source of airborne particulates and acid rain.