For the first time, Colorado officials last week issued an ozone pollution alert for Denver, normally a clean-air haven this time of year. The city’s summer ground-level ozone problem is arising just as it is putting its winter carbon-monoxide pollution problem behind it. The region is one of the areas in the country growing most rapidly — many people are drawn, ironically, to its natural resources and clean mountain air — and Christopher Dann of the Colorado Department of Public Health and Environment attributed part of the new pollution problem to that growth: more vehicle exhaust, more industrial pollution, and more vapors from paint, gasoline, and cleaning fluids.