A new report by the Environmental Protection Agency says ozone levels are falling in 19 Eastern states where bad air is common in the summer. The reduction reflects what agency officials describe as a significant decline in emissions of nitrogen oxides, whose reaction with sunlight, other weather conditions and volatile organic chemicals can make the air hard to breathe in the warmer months. The report says that last year, nitrogen oxide emissions from power plants and other large sources of combustion in the 19 states... were 30 percent below 2003 levels and 50 percent below those of 2000. The result,...