20 million: People who celebrated the first Earth Day, in 1970.

1: Giant hole discovered by scientists in 1985 in the Earth’s ozone layer, which protects the Earth from harmful ultraviolet radiation.

2nd (hand): The federal Environmental Protection Agency announces in 1993 that secondhand smoke contaminates indoor air, posing serious health risks to nonsmokers.

4,000: Number of school buses planned for retrofits in 2003 through Clean School Bus USA program, removing 200,000 pounds of pollution in 10 years.

Source: Federal Environmental Protection Agency

http://www.epa.gov/earthday/history.htm