A plan by South Africa’s state power utility to circumvent pollution controls at one of its two biggest coal-fired plants to enable it to bolster its generation capacity may lead to hundreds of deaths, according to the Centre for Research on Energy and Clean Air (CREA).

Eskom Holdings' application to partially bypass its flue-gas desulfurization unit at the Kusile station for just over a year could see it emit 280,000 extra tons of sulfur dioxide, while mercury emissions would jump 40%, the Helsinki-based pollution research nonprofit said in a report sent to Bloomberg News. It estimates that about 680 people could die as a result.

“The deaths are attributed to increased risk of stroke, ischemic heart disease, lung cancer, chronic obstructive pulmonary disease and lower respiratory disease,” CREA said.

Eskom, which the group previously named as the world’s biggest sulfur-dioxide emitter, runs 14 coal-fired plants, most of which are to the east of Johannesburg. A chimney collapsed at Kusile late last year, knocking 2 160 MW of capacity offline at a time when the utility is already subjecting South Africa to rotational power cuts that often last more than ten hours a day, prompting it to consider temporary repairs.

Kusile is Eskom’s newest plant and the only one that’s fitted with an FGD unit. The company has won approval from South Africa’s environment department to apply for permission through an expedited process to temporarily enable three of its six units to bypass the pollution-control equipment.

The CREA estimate of excess sulfur-dioxide pollution is in the “correct range,” Eskom said, citing its own calculations. Still, both assessments assume all units would operate uninterrupted around the clock, it said in an emailed response to questions. The utility isn’t obliged to report on mercury emissions and hasn’t calculated what they would be.

CREA’s calculations show that 250 people would die from air pollution over the year if the FGD unit was operating normally, while 930 will die if Eskom’s bypass application is approved.

The utility will make its own evaluation of the health impact of its plans and make those available next month.

“The operation of the temporary stacks is for a limited period,” it said, adding that the reduced power cuts “will have a positive environmental, economic and health impact for the whole country, including the communities around Kusile.”