The government and SA’s biggest science council challenged Greenpeace Africa’s claim that nitrogen dioxide (NO2) emissions from Eskom’s coal-fired power plants in Mpumalanga threatened the health of eight-million people living in Johannesburg and Pretoria.

Greenpeace Africa released a report on October 29 that identified Mpumalanga as the world’s biggest NO2 pollution hotspot.

It said easterly winds blew the pollution from the highveld to urban areas in Gauteng, regularly exposing its residents to “extreme and dangerous levels” of NO2. The pollutant raises the risk of respiratory problems, as it inflames the lining of the lungs and reduces a person’s immunity to infections.

Parliament’s portfolio committee on environmental affairs invited Greenpeace to present its findings as part of an inquiry it is conducting into air pollution and minimum emission standards, along with representatives from the department of environmental affairs and the Council for Scientific and Industrial Research (CSIR).

The CSIR’s Rebecca Garland said there was no question that Mpumalanga was a hotspot for NO2 emissions, but there was no evidence that it was the worst in the world or that people were breathing it in.

The satellite data used by Greenpeace Africa measured a column of NO2 in the troposphere over a three-month period to August 31 and did not take account of seasonal variations. The troposphere is the lowest layer of the earth’s atmosphere and extends up to 10km above the earth’s surface.

“We must separate emissions and what we breathe — we do not inhale what an airplane emits,” said Garland, emphasising that the report provided no evidence that NO2 pollution was transported from the troposphere above the highveld to the ground in cities in Gauteng.

The report created the impression that coal-fired power plants were the only source of NO2 emissions; however, it was also produced by vehicles and domestic burning of fossil fuels, she said.

High concentrations of NO2 at ground level had been observed at sites in Johannesburg with high traffic volumes, and this effect was muted at weekends when the number of vehicles on the roads fell, she said.

“It is imperative that we identify the sources and impacts correctly to apply correctly targeted measures to improve air quality,” she said.

The department of environmental affairs said current monitoring showed the levels of NO2 were within SA’s standards.

“Greenpeace is linking the tropospheric observation with ground level impact and this is incorrect,” it said in its submission to the committee.

Presenting an analysis on behalf of the department, Harold Annegarn from the University of the North West said there was nothing ground-breaking about Greenpeace’s claim that Mpumalanga was an NO2 emissions hotspot, as this had been known for over a decade.

Greenpeace Africa’s statement that residents of Johannesburg and Pretoria were exposed to extreme levels of NO2 were “false and intended to create alarm”, he said.

High emission levels do not automatically translate into elevated ground level exposure, he said.

“This is a fatal flaw and on this ground alone the Greenpeace media briefing should be totally discredited and rejected,” he said.

Greenpeace Africa’s Melita Steele said regardless of whether SA was the worst or the tenth worst NO2 polluter, it was clear there was a serious problem.

“When you have such significant air pollution in SA, the impact on lives cannot be in dispute,” she said.