EPA issued the current air-quality standard for lead in 1978. The Clean Air Act requires the agency to review the standard every five years and issue new standards if it determines that they are required to protect public health. Periodic reviews of the scientific evidence of the health effects of airborne-lead exposure since 1978 have concluded that revisions to the standard were not necessary.

EPA released the first draft of the lead criteria document Dec. 2, 2005, summarizing the science that it will use in the forthcoming review of the lead standard. The document said that data collected since 1986 show that lead has toxic effects at much lower exposure levels than previously believed.

EPA is under court order to issue the final lead-criteria document by Oct. 1, 2006. The next draft of the lead-criteria document is due to be released in late May. EPA's initial staff recommendations are due Oct. 1, 2006, with final staff recommendations due in late July 2007.