Environmental problems such as global warming and a reduction in species diversity pose serious threats to human health and the environment on a global scale.  Air and water pollution also pose a threat to the environment.

Air pollution is the introduction of toxins into the atmosphere.  A clean atmosphere is essential to support life on earth.  Ozone depletion due to air pollution pose a serious threat to human health as well as to the earth’s ecosystems.  Examples of air pollutants are benzene, asbestos, toluene, cadmium, mercury, chromium, and lead compounds.

Apart from causing environmental problems, hazardous air pollutants are suspected to cause cancer or other serious health problems including reproductive defects.  In addition to breathing air toxins, some toxic air pollutants such as mercury can deposit into soil or surface waters.  These toxins are absorbed by plants and animals thus passing the toxins through the food chain.  Most air toxins are generated as a result of human activities.  Toxins from power plants, factories, refineries, building materials are  some of the examples for toxins from human made sources.  Some air toxins are also released from natural sources such as volcanic eruptions and forest fires.

The Office of Air and Radiation (OAR) which works under Environment Protection Agency of the U.S. government develops national programs, technical policies, and regulations for controlling air pollution and radiation exposure.