The ruling clears up the remaining legal issues over EPA’s action that were left unresolved by the Supreme Court -- which earlier this year unanimously reversed a decision by a lower court to strike down the standards. Specifically, the D.C. Circuit found that EPA had not overstepped its legal authority, and that the standards were not arbitrary or capricious.

The decision comes amid mounting evidence of the dangers of fine particulates in the air (which frequently originate from vehicle engines, power plants, or wood fires) and ozone pollution. A study released earlier this month from the Journal of the American Medical Association found that long-term exposure to fine particulates significantly increases the risk of lung cancer. Other studies have shown that ozone exposure not only aggravates childhood asthma, but can also cause it. Now it is up to EPA to enforce the standards so that we will be protected from this damaging pollution in reality and not just legally in the courtroom.

As the Washington Post editorializes, President Bush could help by stopping efforts within his administration to weaken enforcement actions against heavy-polluting, older coal-fired power plants.