Hydrocarbon with some hydrogen atoms replaced by chlorine and fluorine atoms. Chemically and thermally stable, CHCs are noncombustible synthetic solvents with several industrial applications. Some examples are the manufacture of synthetic solvents and insecticides. They endanger the environment by they are poisons that have persistence in the environment because of their chemical stability , and tendency to dissolve with water into the atmosphere. CHCs concentrate in animal fat and attack heart and liver tissue. It can cause an anesthetic or narcotic effect. Sunlight on chlorinated hydrocarbons forms chlorine monoxide, which breaks down ozone in our atmosphere. This allows cancer-causing ultraviolet (UV) rays to reach the earth’s surface by causing large ‘holes’ in the ozone layer . Refer also to chlorofluorocarbon and chlorofluoromethane.