“If the court agrees with groundWork, big sulfur-dioxide emitters like Eskom and Sasol will have to act immediately to reduce their pollution,” the organization, which is being represented by lawyers from the Centre for Environmental Rights, said in a statement. “This will requite significant capital expenditure.”

South Africa relies on coal for most of its power, with Eskom running some of the world’s biggest coal-fired power plants and spending tens of billions of dollars building two more. Albi Modise, a spokesman for the Department of Environmental Affairs, declined to comment.

The limit of 1,000 milligrams of the pollutant per normal cubic meter is significantly more lax than standards in China and India, according to groundWork. The group said sulfur dioxide leads to increased incidences of low birth weights and still births and contributes to acid rain.

About 25 facilities in the country are affected by the legislation, ranging from plants operated by Eskom and Sasol to coal boilers at the operations of paper and pulp producers Sappi Ltd. and Mondi Ltd., groundWork said in its founding affidavit.