Most air pollution is caused by the burning of fossil fuels, which include coal, oil, natural gas, and gasoline. Power plants burn these fuels to make electricity. Not only do fossil fuel power plants create air pollution, they also use lots of water (for cooling off), and remember, the coal and oil natural resources come from mining, which destroys animal and plant habitats.
Some of the gases produced from making electricity, like sulfur dioxide, nitrogen oxides, particulate matter and heavy metals, get in the environment and are harmful to human health, as well as plants and animals. Other gases, like carbon dioxide, contribute to the climate change. In fact, making electricity accounts for one-third of the total carbon dioxide emissions in the US, and continues to increase.
Sometimes I imagine I have my personal little pollution stream rising from my local power plant. As I click off a light in an empty room, or turn down the thermostat, I can see that stream getting smaller in my mind. Then I imagine other people doing the same thing to their little streams!