Air pollution trends

• notice the general increase in concentrations prior to 1970
• after 1970, notice the general decline in pollution concentrations
• in 1970, the Clean Air Act of 1970 was passed
• the Clean Air Act was updated in 1990
• clean air standards are established by the EPA, though many states have their own standards that are more strict than the federal standards.

image adopted from Meteorology Today by C. Donald Ahrens  © 1994 West Publishing Company