The 1,900 new power plants called for in U.S. President Bush’s energy plan pose a big threat to air quality in places where smog is already bad, experts say. They are also concerned about moves by the Bush administration to end efforts by former President Clinton to force dozens of dirty, old coal-powered plants to install modern pollution-control equipment. Last week, the administration began a series of public hearings on its proposal to ditch the “new source review” rules that require the older plants to make the changes. Meanwhile, Vice President Dick Cheney is hitting the road this week to try to rally support for the energy plan he helped to produce, even as drops in fuel prices across the country are undercutting the administration’s claim that the country is in the midst of an energy crisis.