What are the current ground-level ozone standards in the United States?
In 1997, the U.S. Environmental Protection Agency revised its National Ambient Air Quality Standard for ground-level ozone. The new standard is 0.08 parts per million measured over eight hours. This replaced the old standard of 0.12 parts per million measured over one hour. Also, the average of the fourth highest concentration over a three-year period will determine whether an area is out of compliance.
