• Air Quality: Sulphur dioxide (SO2) levels decreased by 50.3% from 1975 to 1993; Nitrogen dioxide (NO2) levels decreased by 32.7% from 1977 to 1993; ground-level ozone (smog) decreased by 18.5% from 1979 to 1993; and particulate matter (soot) levels declined by 23.6% from 1975 to 1991. Between 1986 and 1995 alone, carbon monoxide concentrations decreased by 37%. Sources: "Index of Leading Environmental Indicators," Pacific Research Institute for Public Policy and "Six Principal Pollutants -- Carbon Monoxide," U.S. Environmental Protection Agency Office of Air and Radiation. Contact: Erin Schiller @ 415/989-0833, Web: http://www.ideas.org.
  
  
• Oil Spills: The amount of oil spilled in U.S. waters has declined from 15 million gallons per year in the mid 1970s to two million gallons in 1992, a decrease of 86%. Source: "Twenty-Five Years of Environmental Progress at a Glance," Environmental Protection Agency.
  
  
• Water Quality: Phosphorus, fecal coliform and dissolved oxygen levels in rivers and streams exceeding local standards declined between 1974 and 1990. 75% of America's streams and rivers, 82% of its lakes and 87% of its estuaries were considered safe for swimming in 1990. Source: "Index of Leading Environmental Indicators," Pacific Research Institute for Public Policy. Contact: Erin Schiller @ 415/989-0833, Web: http://www.ideas.org.
  
  
• Forests: The average volume of standing timber is approximately one-third greater than it was in 1952. In the eastern United States, the average volume per acre has nearly doubled. Today forest growth exceeds harvest by nearly 40%. The volume of forest growth in 1986 was close to 350% greater than it was in 1920. Sources: "Talking Points on the Economy -- Environmental Series," The National Center for Public Policy Research and "Sustainability -- It's a Fact," Forests Today and Forever. Contact: David Ridenour @ 202/543-4110, e-mail: EarthDay@nationalcenter.org, Web: http://www.nationalcenter.org/eptftalk.html.
  
  
• Lead: Lead emisssions have decreased by 98% since 1970. Since 1978, the average blood-lead levels have decreased by 75%. Source: "Twenty-Five Years of Environmental Progress at a Glance," Environmental Protection Agency.

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