Eskom, South Africa’s biggest polluter, is struggling to curb its highest particulate emissions in two decades after its Kendal power plant was damaged during a strike.

The emissions, which cause respiratory disease, were about 0.5kg/MWh sent out in the six months to 30 September, Eskom said in its interim results presentation on Thursday. The 2018 strike resulted in damage to the plant’s anti-pollution equipment.

“The last two years has been the worst we have seen in 20 years and it’s just from one power station,” Deidre Herbst, Eskom’s environmental manager, said in an interview. “It’s not acceptable, but all the other power stations are reporting well.”

Air pollution is becoming a key issue in South Africa. Residential areas near Eskom’s 15 coal-fired power stations have pollution levels that rival the most contaminated cities on the planet. Environmental activists are suing the government over breaching the constitutional right to clean air because of emissions from Eskom and chemicals company Sasol.

Efforts are being made to repair the equipment, Herbst said. The plant cannot be taken offline in its entirety because the utility is struggling to supply South Africa with sufficient power.

Kendal is designed to produce about 4GW of electricity.  — Reported by Loni Prinsloo and Antony Sguazzin, (c) 2019 Bloomberg LP