But the traffic increase has slowed progress in reducing emissions further, and people in many areas still suffer from nitrogen-related air pollution, including small particulates that get sucked deep into the lungs, and ground-level ozone - a strongly irritant gas formed by the action of sunlight on reactive nitrogen.
Ms. PATTON: The Four Corners Power Plant and the Navajo Generating Station collectively discharge some 77, 000 tons of smog and haze-forming oxides of nitrogen each year, and that is comparable to the amount of pollution that would be discharged from some 80 million motor vehicles.