Source of Contamination	Contaminant	Typical Sites
Natural	Dissolved minerals	Mineral deposits, mineralized waters, hot springs, sea water intrusion
	Asbestos	Mine tailings, serpentine formations
	Hydrogen-sulfide	Subsurface organic deposits
	Radon	Most geologic formations
Commercial Businesses	Gasoline	Service stations' underground storage tanks
	Solvents	Dry cleaners, machine shops
	Toxic metals	Photo processors, laboratories, metal plating works
Municipal	Microbial agents, nutrients, and miscellaneous liquid wastes	Bacteria and virus contaminants from a variety of sources such as sewage discharges and storm water runoff, contributions from industrial dischargers, households, and septic tanks
Industrial	VOCs, industrial solvents, toxic metals, acids	Electronics manufacturing, metal fabricating and plating, transporters, storage facilities, hazardous waste disposal
	Pesticides and herbicides	Chemical formulating plants
	Wood preservatives	Pressure treating power poles, wood pilings, railroad ties
Solid Waste Disposal	Solvents, pesticides, toxic metals, organics, petroleum wastes, and microbial agents	Disposal sites which receive waste from a variety of industries, municipal solid wastes, wasted petroleum products, household waste
Agricultural	Pesticides (herbicides, fumigants, fungicides), fertilizers, concentrated mineral salts, microbial agents	Irrigated farm runoff, agriculture chemical applications, fertilizer usage, chemical storage at farms and applicators' air strips, agricultural produce packing sheds and processing plants, meat processing plants, dairies and feed lots
Disasters	Solvents, petroleum products, microbial agents, other hazardous materials	Earthquake, storm, or accident caused pipeline and storage tank failures and damage to sewage treatment and containment facilities; major spills of hazardous materials; flood water contamination of storage reservoirs and ground water sources