Inorganic contaminants: Salts and metals, which may be naturally occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining or farming.

Microbial contaminants: Viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock and wildlife.

Organic chemical contaminants: Synthetic and volatile organic chemicals, which are by-products of industrial processes and petroleum production, and may also come from gas stations, urban stormwater runoff and septic systems.

Pesticides and herbicides: May come from a variety of sources, such as agriculture, urban stormwater runoff and residential uses.

Radioactive contaminants: May be naturally occurring or br the result of oil and gas production and mining activities.