Two of the sampling location must be locations furthest from the treatment facility. Volatile organic compounds are used in a variety of applications. Some are used as solvents of oils, greases, waxes, resins, lacquers, rubbers, and other similar materials. Others are used in aviation fuel, as fuel additives, pesticides, insecticides, paint and finish removers, and fumigants. Many are also used in the manufacture of polymers, protective coatings, perfumes, plastics and other organic synthesis.
Toxicological studies indicate that some of the volatile organics are health risks.
The groundwater can become contaminated with these substances from leaking underground fuel and solvent storage tanks, agriculture practices, and improper waste disposal. Virtually all pesticides are toxic to man to some degree. The environmental impact of these pesticides vary because some decompose or biodegrade quickly while others remain stable and intact for long time periods. Polychlorinated biphenyls or PCB's are compounds that were widely used as coolants, insulating material, and lubricants in electrical equipment like transformers and capacitors. PCB's are highly toxic, damaging to the ecology, and very persistent.