[JURIST] The US Environmental Protection Agency [official website] said Wednesday that a stricter air quality rule [PDF text; press release] on ground-level ozone and smog will go into effect in May, requiring some 345 US counties [map, PDF] to reduce air pollution in order to come into compliance with the new standard. The revisions [fact sheet, PDF] to the National Ambient Air Quality Standards For Ozone were based on the results of over 1,700 studies showing that the old standards on smog levels still created a risk of negative health effects. Counties that do not comply with the new standards include the cities of Los Angeles, Jacksonville, El Paso, and Cleveland.

The EPA has the power to monitor ozone levels under the Clean Air Act [text]. The EPA is required to review ozone standards every five years, and the standards were last adjusted in 1997. AP has more.