Environmental rights groups filed papers against the government on Friday over air pollution in Mpumalanga, saying the air quality has contributed to hundreds of premature deaths.

The so-called Highveld Priority Area, which includes much of Mpumalanga province and part of Gauteng, is the site of 12 coal-fired Eskom power plants, a Sasol oil refinery and coal-to-fuel plant owned by the company. It's also where almost all of South Africa's coal is mined.

A Greenpeace study for the third quarter of 2018 showed that Mpumalanga had the worst nitrogen dioxide emissions from power plants of any area in the world. Mpumalanga is also where Eskom has been building its Kusile coal-fired power station near Witbank.

GroundWork and Mpumalanga community organisation Vukani Environmental Justice Movement in Action, represented by the Centre for Environmental Rights, filed the case in the Pretoria High Court.

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In supporting documents, Head of Occupational and Environmental Medicine at the University of Illinois Professor Peter Orris said the pollution by the coal industry of Mpumalanga left populations there vulnerable to serious diseases.

"The high levels of air pollution in and around the Highveld Priority Area constitute an immediate and significant public health hazard that should be remedied to save lives and allow current and future generations of South Africans to live longer and healthier," said Orris.

The environmental justice groups are asking the court to declare the current levels of air pollution on the Highveld a violation of people's Constitutional rights, and to force government to take meaningful action to implement and enforce the Highveld Property Area.

The groups said they were forced to launch this case because of the repeated failure of government to enforce air quality laws.