Toxic. Liquid. Migratory.
NAPL is not a type of pollutant. The term instead refers to the physical and chemical properties of a pollutant. For example, PCBs, chlorinated solvents, mercury, and coal tar can occur as NAPL when released into the environment in liquid form. The liquid nature of NAPL means it can easily move through the water. NAPL can appear oily, float on the surface, or sink to the bottom. It is created when producing common goods like dry cleaning fluid, gasoline, and fuel oils.

NAPL poses a serious risk to public health, in large part because its liquid nature makes it possible for NAPL to flow into drinking water supplies.