2. Hazardous environmental contaminants

A hazardous contaminant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. Environmental contaminants may cause long or short term damage by changing the growth of plant or animal species or by interferring with human amenities, comfort, health, or property values. Some hazardous contaminants are biodegradable and therefore will not persist in the environment in the long term. Contaminants with high persistence in the environment have to be cleaned or remediated to eliminate their potantial risks to sustained environmental health. Major sources of contaminants polluting soil, water, and air are: