air pollutants, as defined by the Clean Air Act, that present a threat to human health and/or the environment. Pollutants include asbestos, beryllium, mercury, benzene, etc. The creation of various monitoring programs set up by the Environmental Protection Agency, allow for the regulation of the required 188 hazardous air pollutants. [Journal of Atmospheric Environment, Volume36, Issue 11, April 2002, Pages 1783-1791] [Journal of Atmospheric Environment, Volume 30, Issue 20, October 1996, Pages 3443-3456]