The U.S. Environmental Protection Agency (EPA) has published summaries of “reference values” for health effects from the inhalation of five chemicals— manganese, benzene, toluene, ethylbenzene, and xylene. Each report describes the chemical, exposure potential and health effects, then provides in graphic and table form a compendium of inhalation reference values derived from a variety of sources, including the American Conference of Governmental Industrial Hygienists, Agency for Toxic Substances and Disease Registry and National Institute for Occupational Safety and Health. The reports do not establish new levels nor do they require use of any particular reference level in any specific circumstance. Each report contains commentary on health effects of the chemicals addressed. For example, the benzene report states, “it is repeated peak benzene exposures which have been deemed determinative of bone marrow toxicity with a greater potential for leukemia.”