There are many sources of pollution in our waters. In addition to point sources such as sewage and industrial waste, a great deal of water pollution comes from non-point sources such as agricultural runoff, and stormwater drainage. Common water pollutants include pesticides, lead, arsenic and polychlorinated biphenyls (PCBs). Since human life depends on clean water, the protection of our water sources from these and other pollutants is one of the EPA's most important challenges. Under the Clean Water Act, the Agency regulates discharges of pollutants into the waters of the United States and sets effluent standards. The EPA also works with state and local authorities to control the pollution from non-point sources.

Recommended EPA Web pages

• What Contaminants May Be Found in Drinking Water?
  This page discusses the different ways in which ground water and drinking water can become contaminated.
• Drinking Water Contaminants
  This page lists current drinking water standards (Maximum Contaminants Levels) for regulated contaminants.
• Drinking Water Contaminant Candidate List and Regulatory Determinations
  The Safe Drinking Water Act requires EPA to establish a list of contaminants to aid in priority-setting for the Agency's drinking water program.

Air Pollutants
Aerosols, Asbestos, Carbon Monoxide, Chlorofluorocarbons (CFCs), Criteria Air Pollutants, Ground Level Ozone, Hazardous Air Pollutants (HAPs), Lead, Mercury, Methane, Nitrogen Oxides (NOx), Particulate Matter (PM), Propellants, Radon, Refrigerants, Sulfur Oxides (SOx), Volatile Organic Compounds (VOCs)

Biological Contaminants

Carcinogens

Chemicals
Benzene, Chlorofluorocarbons (CFCs), Chromated Copper Arsenate (CCA), Dichloroethylene (DCE), Dioxins, Endocrine Disruptors, Ether, Ethylbenzene, Furans, Halons, Hazardous Air Pollutants (HAPs), Heavy Metals, Hydrochlorofluorocarbons (HCFCs), Inorganic Cyanides, Ketones, Methane, Methyl Bromide, Methyl Chloride, Methyl-T-Butyl-Ether (MTBE), Nitrogen Oxides (NOx), Organic Cyanides, Particulate Matter (PM), Perchloroethylene (PCE), Phthalates, Polychlorinated Biphenyls (PCBs), Radioactive Substances, Radionuclides, Styrene, Sulfur Hexafluoride (SF6), Sulfur Oxides (SOx), Toluene, Trichloroethylene (TCE), Volatile Organic Compounds (VOCs)

Microorganisms
Coliform, Cryptosporidium, Viruses

Ozone

Radiation
Ionizing Radiation, Radiation Detection, Radiation Exposure, Radiation Protection, Radioactive Substances, Radionuclides, Radon

Soil Contaminants
Acetone, Arsenic, Barium, Benzene, Cadmium, Chloroform, Cyanide, Lead, Mercury, Polychlorinated Biphenyls (PCBs), Tetrachloroethylene, Toluene, Trichloroethylene (TCE)

Toxic Substances
Persistent Bioaccumulative Toxic Pollutants (PBTs), Persistent Organic Pollutants (POPs), Toxicological Profiles

Water Pollutants
Arsenic, Contaminated Sediment, Disinfection Byproducts, Dredged Material, Lead, Microbial Pathogens