Air pollution from coal-fired power plants is linked with asthma, cancer, heart and lung ailments, neurological problems, acid rain, global warming, and other severe environmental and public health impacts.

Coal has long been a reliable source of American energy, but it comes with tremendous costs because it is incredibly dirty. The same chemistry that enables coal to produce energy—the breaking down of carbon molecules—also produces a number of profoundly harmful environmental impacts and pollutants that harm public health. Air pollution and global warming are two of the most serious.

When coal burns, the chemical bonds holding its carbon atoms in place are broken, releasing energy. However, other chemical reactions also occur, many of which carry toxic airborne pollutants and heavy metals into the environment.

This air pollution includes:

Mercury: Coal plants are responsible for 42 percent of US mercury emissions, a toxic heavy metal that can damage the nervous, digestive, and immune systems, and is a serious threat to the child development. Just 1/70th of a teaspoon of mercury deposited on a 25-acre lake can make the fish unsafe to eat. According to the Environmental Protection Agency’s (EPA) National Emissions Inventory, US coal power plants emitted 45,676 pounds of mercury in 2014 (the latest year data is available).

Sulfur dioxide (SO2): Produced when the sulfur in coal reacts with oxygen, SO2 combines with other molecules in the atmosphere to form small, acidic particulates that can penetrate human lungs. It’s linked with asthma, bronchitis, smog, and acid rain, which damages crops and other ecosystems, and acidifies lakes and streams. US coal power plants emitted more than 3.1 million tons of SO2 in 2014.

Nitrogen oxides (NOx): Nitrous oxides are visible as smog and irritate lung tissue, exacerbate asthma, and make people more susceptible to chronic respiratory diseases like pneumonia and influenza. In 2014, US coal power plants emitted more than 1.5 million tons.

Particulate matter: Better known as “soot,” this is the ashy grey substance in coal smoke, and is linked with chronic bronchitis, aggravated asthma, cardiovascular effects like heart attacks, and premature death. US coal power plants emitted 197,286 tons of small airborne particles (measured as 10 micrometers or less in diameter) in 2014..

According to a new study by University of California, Berkeley the least expensive way for the Western U.S. to reduce greenhouse gas emissions enough to help prevent the worst consequences of global warming is to replace coal with renewable and other sources of energy that may include nuclear power.

The experts reached this conclusion using SWITCH, a highly detailed computer model of the electric power grid, to study generation, transmission and storage options for the states west of the Kansas/Colorado border. The model will be an important tool for utilities and government planners.

"Decarbonization of the electric power sector is critical to achieving greenhouse gas reductions that are needed for a sustainable future," says Daniel Kammen, Distinguished Professor of Energy in UC Berkeley's Energy and Resources Group. "To meet these carbon goals, coal has to go away from the region."

While some previous studies have emphasized the high cost of carbon taxes or caps, the new study shows that replacing coal with more gas generation, as well as renewable sources like wind, solar and geothermal energy, would result in only a moderate increase to consumers in the cost of electric power – at most, 20%. They estimate a lower ratepayer cost, Kammen said, because the evolution of the electrical grid over the next 20 years – with coordinated construction of new power plants and transmission lines – would substantially reduce the actual consumer cost of meeting carbon emission targets.

Burning coal, a non-renewable resource, produces around 20% of the world's greenhouse gases, but also releases harmful chemicals into the environment such as mercury, sulfur dioxide, nitrogen oxides and sulfuric acid, responsible in some areas for acid rain and respiratory illness.