Ключевые слова: air, air pollution, air quality, blue, climate change, co, colorado, conservation, denver, ecological, ecology, ecosystem, energy, engineering and technology, environment, environmental, environmental issues, environmentalism, global warming, greenhouse emissions, industrial, industry, north america, political and social issues, power, power plants, rocky mountain states, sky, smoke, smokestacks, united states, united states of america, us, usa, waste,