How do chemicals, hazardous wastes, oils, etc contribute to pollution and water quality?

Hazardous, or toxic, waste is the potentially dangerous byproduct of a wide range of activities, including manufacturing, farming, water treatment systems, construction, automotive garages, laboratories, hospitals, and other industries. The waste may be liquid, solid, or sludge and contain chemicals, heavy metals, radiation, pathogens, or other materials. Even households generate hazardous waste, from items such as batteries, used computer equipment, and leftover paints or pesticides.

Toxic waste can harm people, animals, and plants, whether it ends up in the ground, in streams, or even in the air. Some toxins, such as mercury and lead, persist in the environment for many years and accumulate over time. Humans or wildlife often absorb these toxic substances when they eat fish or other prey.

In the past, many hazardous wastes were only loosely regulated, allowing substantial contamination of communities and the environment. In the U.S., toxic waste has been overseen by the federal Environmental Protection Agency (EPA) since 1976, as well as state departments of environmental protection. The EPA now requires that hazardous waste be handled with special precautions and be disposed of in designated facilities. Many towns have special collection days for household hazardous waste.