When the sun shines on a coal plant, it can burn up to 20 times hotter than the Sun Dome

It was the dawn of the coal-burning age in the United States.

But today, many of America’s coal-fired plants are under review for their emissions of carbon dioxide, mercury and other pollutants.

Coal plants that don’t comply with new rules on mercury, sulfur dioxide and other air pollutants are often fined by the EPA, which has been accused of overreach.

Here are some key moments in the history of the air that is blowing through America’s power plants.

– July 23, 1950: A coal plant near Clarksburg, Tenn., emits more than 1 million pounds of mercury and nearly 1 million tons of sulfur dioxide, according to the U.S. Department of Labor.

– December 21, 2010: A large coal plant in West Virginia emits up to 18 million pounds per year of mercury, the EPA says.

– November 30, 2017: A small coal plant on the East Coast emits up 25 million pounds in mercury, while a larger coal plant emits more 15 million pounds.

– March 20, 2018: A new coal plant is being built in Pennsylvania, which emits nearly 18 million tons, the agency says.

The EPA has ordered coal plants in the U, S. West and West Virginia to stop releasing mercury and sulfur dioxide to the air, but the plants have not complied.

– April 4, 2018