A plan to cut air pollution dramatically in Houston by 2007 was approved by the U.S. EPA yesterday. If successful, the plan will bring the city into compliance with the federal Clean Air Act for the first time. The plan lowers speed limits, mandates stricter vehicle exhaust testing, and calls for a 90 percent decrease in industrial nitrogen oxide emissions, among other measures. Regional EPA Administrator Gregg Cooke praised it as “the most innovative and technically advanced air plan ever devised,” but some environmental groups expressed doubt that the plan would succeed in cleaning up the city’s notoriously icky air. Houston surpassed Los Angeles as the smoggiest city in the U.S. in 1999 and 2000, and will probably come in a close second this year.