There are many sources of air pollution. In fact, the EPA has recently listed the greenhouse gas carbon dioxide as an air pollutant - so even as we breathe, we are 'polluting' the air. Of course, breathing is not a major source of CO2 - the combustion of fossil fuels ranks number one in that category.

Fossil Fuels

The single largest source of air pollution comes from the combustion of fossil fuels. In 2007 alone, the United States consumed 1,127,998,000 short tons of coal to produce electricity, make coke, for residential use, and for industrial use. Of this, 1,045,141,000 tons of coal were burned to produce electricity.

In 2007, the US also consumed 23,047,229,000,000 cubic feet of natural gas, and 6,736,961,000 barrels of oil for fuels such as gasoline, diesel, and jet fuel.

Coal-burning, electricity-generating power plants alone emitted 2,516,580,000 tons of carbon dioxide, 9,042,000 tons of sulfur dioxide, and 3,650,000 tons of nitrogen oxides into the atmosphere. Recall that sulfur dioxide and nitrogen oxides create acid rain.

The following chart depicts the total US greenhouse gas emissions for 2007, in millions of metric tons.

U.S. Greenhouse Gas Emissions by Gas, 2007
U.S. Greenhouse Gas Emissions by Gas, 2007


The global carbon dioxide gas emissions in 2007 is estimated to be about 30 billion metric tons.

World CO2 emission by country, 2006
World CO2 emission by country, 2006



Other Air Pollutants

Through the combustion of fossil fuels, other chemicals besides CO2, sulfur dioxide, and nitrogen oxides are emitted. Here are a few important ones that are of health concern.

  • Mercury
    • released into the atmosphere by combustion of coal (65% of all anthropogenic mercury) or by volcanic eruptions
    • in 2003 alone, 48 tons (44 million grams) of mercury was estimated to have been released by burning coal
    • mercury is a bio-accumulator, which means it builds up in concentration through the food chain; thus shellfish, tuna, and even freshwater fish (like trout) will have a high mercury content
    • mercury is highly poisonous - it will damage the brain, the kidneys, and the liver, and long-term exposure can cause severe diseases

  • Arsenic
    • released into the atmosphere by combustion of coal; natural occurrences in groundwater
    • an estimated 225 pounds of arsenic are released by a single coal-fired power plant each year
    • arsenic is extremely poisonous and carcinogenic; exposure to 50 parts per billion in water will cause cancer in one out of every 100 people

  • Heavy Metals
    • a single 1000 MW coal-fired power plant on average emits 5.2 tons of uranium and 12.8 tons of thorium; both are radioactive elements. This is over 100 times more radiation than a nuclear power plant of comparable size emits.
    • an estimated 114 pounds of lead and 4 pounds of cadmium are released by a single coal-fired power plant each year

  • Ozone and smog
    • nitrogen oxides and volatile organic compounds (both emitted by burning fossil fuels) combine in the presence of sunlight, forming ground-level ozone, which causes respiratory problems such as asthma
    • this combination usually occurs in urban areas and in areas downwind from large power plants; EPA estimates that 48% of Americans live in areas having unhealthy air from smog