FILE - In this Oct. 25, 2013 file photo, petroleum coke, or petcoke, is watered down where it is stored along the Calumet River on Chicago's southeast side. The Pollution Control Board is scheduled to meet Thursday, Jan. 23, 2014, in Chicago to consider Gov. Pat Quinn's proposed emergency regulations for petroleum coke. Quinn says he's responding to complaints from Chicago residents that petroleum coke piling up on the city's southeast side is a health and environmental threat. (AP Photo/Charles Rex Arbogast, File)

Environmentalists are planning to take billionaires Charles and David Koch to court, alleging the brothers' companies are responsible for polluting Chicago's Southeast Side with the black, thick dust known as petroleum coke -- or petcoke, a byproduct of the oil refining process.

ThinkProgress reported this week that the Natural Resources Defense Council (NRDC) and Southeast Environmental Task Force (SETF) have given a 90-day notice of an intention to sue Koch-owned companies including KCBX Terminals over the pollution associated with their petcoke storage facilities located along the Calumet River in a low-income, partially industrial Chicago community.

In a press release, the groups said the lawsuit stems from neighbors complaining that the dust spewing from the facilities' large, uncovered petcoke piles has polluted the river, "invaded" their homes and blackened area skies.

"People are complaining about finding dust from these sites inside their homes," Peggy Salazar, SETF executive director, said in a statement. "Black dust is coating their houses and probably their lungs. This has to stop. And hopefully this suit will achieve that."

On Wednesday, the Chicago City Council approved regulations that ban new petcoke storage facilities from opening up in the city, but do not require the shutdown of the three sites currently in operation.

The Chicago Tribune reports the storage sites will be newly required to report how much petcoke and coal they ship through the city on a quarterly basis. They will also need to enclose their piles within two years and cannot expand their operations.

Mayor Rahm Emanuel's office described the ordinance as the toughest petcoke regulations in the nation, but environmental groups pushing for an outright ban disagree.

“It is the city’s ultimate obligation to protect its residents,” Salazar said Wednesday, according to the Northwest Indiana Times. “We don’t believe they did that here.”

Most of the petcoke in Chicago is shipped in from the nearby BP refinery in Whiting, Indiana, which is tripling their output of the dangerous dust after expanding their facility. Petcoke can cause health problems like coughing, wheezing and shortness of breath, in addition to aggravating existing respiratory conditions like asthma, according to the Chicago Department of Public Health.