* Water: detergents, fertilizer, raw sewage, prescription medication, pesticides, herbicides, heavy metals, PCBs
* Soil: heavy metals, herbicides, pesticides, PCBs
* Air: particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, asbestos, ground-level ozone, lead (from aircraft fuel, mining, and industrial processes)
The EPA maintains a list of priority pollutants for testing and regulation.