Joburg, Pretoria and the industrialised area to the east of the Highveld cities have the highest concentration of the air pollutant nitrogen dioxide (NO2) in the southern hemisphere, according to data from Nasa satellites.

Nasa, which has released a high-resolution global map that shows air pollution trends from satellite data between 2004 and 2014, said it showed a complex situation playing out between the two cities, neighbouring coal-power plants and the industrialised areas.

A study conducted by the State of Environment South Africa, which falls under the Department of Environmental Affairs, found that air quality in Gauteng had been influenced by rapid urbanisation associated with growth in industry, power generation, transportation systems and domestic fuel burning.

“A lack of adequate urban planning controls has led to industrial sources of air pollution in close proximity to densely populated areas,” said Nasa.

Dangerous gases like nitrogen dioxide are produced from burning fossil fuels, generated mainly by vehicle exhausts, the smokestacks of electricity power plants and industrial activity.

The Highveld region around Joburg and Pretoria saw a decrease in nitrogen dioxide from 2008, when all new cars were required to have better exhaust-emission controls.

“The heavily industrialised area just east of the two cities, however, shows both decreases and increases,” Nasa said.

Nasa’s global map depicts nitrogen dioxide as red blobs where levels are high. The only red blob on the whole African continent is in South Africa over the Highveld.

The effects of poisonous gases like NO2 and air pollution around these areas have made serious impacts on the health of residents, especially those living near industrial areas and mine dumps where such gases are released.

Early this year, Patricia Plaatjies, 61, of Diepkloof, Soweto, had told The Star she had been battling with a lung disorder since 2009.

“As you can see, I am now on an oxygen machine 16 hours a day. I have lived here for 45 years and we breathe in the dust and toxic air from the mine dumps. The water in the rivers is toxic and nothing has been done about it,” she said. “I worry for the future generations because this environment is not safe – and it’s not only me who is affected.”

Riverlea resident Charles van der Merwe said there had been a one-year-old child who had also been on oxygen because of the dangerous mine dust and toxic air. “In just one extension, there are nine people affected – children and the elderly – all of them are on oxygen machines.

“There are a lot of people around here who have asthma and lung conditions because of the bad air,” he had said.

In addition, the State of Environment South Africa found the health impacts of air pollutants like NO2 and carbon dioxide to be “numerous, varied and affect various areas of the human body”.

Air pollution from domestic sources such as coal, wood and paraffin have been described as having a major effect on people’s health.

In South Africa, this was confirmed in a study undertaken by theFund for Research into Industrial Development, Growth and Equity (Fridge) to assess the social and economic impacts of phasing out “dirty” fuels in South Africa.