A report by the US Office of Management and Budget concludes that the value of reductions in hospitalization and emergency room visits, premature deaths and lost workdays resulting from improved air quality were estimated between $120 billion and $193 billion from October 1992 to September 2002.

By comparison, industry, states and municipalities spent an estimated $23 billion to $26 billion to retrofit plants and facilities and make other changes to comply with new clean air standards.

Read the full report:
http://www.whitehouse.gov/omb/inforeg/2003_cost-ben_final_rpt.pdf