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What’s that stench? Investigating two claims about air pollution in South Africa

Residents of Johannesburg, South Africa’s largest city, regularly find themselves holding their noses at the reek in the air. But are they also losing something far more serious – at least three years of their lives – to air pollution?

This article is more than 1 year old

  • One measure of air pollution is the level of fine particulate matter, or PM2.5, and by both WHO and local guidelines, South Africa scores above the recommended standard.

  • According to the latest data available, South Africa’s levels of PM2.5are four to six times higher than WHO guidelines, but vary greatly between areas.

  • Calculating life expectancy losses because of air pollution is a complex exercise, according to a number of experts. Figures are “best guesstimates” and should be treated with caution.

Residents of Johannesburg have long complained of a “foul smell” in the air, similar to “sulphur or rotting eggs”. In June 2022, the stench prompted media attention on air pollution in the country. 

Malawian news outlet the Maravi Post went further and claimed that high air pollution levels in Johannesburg had reduced life expectancy by 3.2 years.

The newspaper also claimed that one type of air pollutant in South Africa, fine particulate matter, or PM2.5, was “1.4 times higher than the guidelines set by the World Health Organization (WHO)”. 

Does available data support these claims? We checked.


South Africa’s PM2.5 level is 1.4 times above the levels recommended by the WHO.



According to Prof Harold Annegarn, a researcher and expert in air pollution from North West University in Potchefstroom, South Africa, the sulphuric stench wasn’t what the public should have been focusing on. What was truly harmful to health was the particulate matter and toxic gases that polluted the air from a variety of sources, he told Africa Check.

To understand levels of air pollution in South Africa, we need to start with the basics. What is air pollution and how do we measure it? 

Air pollution is a blanket term for a number of different particles and gases that can be found in the atmosphere. Ambient or outdoor air pollution contributes to a range of illnesses, like asthma, some cancers, and lung disease. One type, called fine particulate matter, or PM2.5, is especially dangerous to human health because the particles are very small. They have an aerodynamic diameter of 2.5 micrometres or less, small enough to enter the lungs and bloodstream. 

Dr Kristy Langerman is an expert on atmospheric science at the University of Johannesburg. She told Africa Check that unlike car accidents or other immediate causes of death, the health effects of air pollution built up over time. Living in an area with a lot of air pollution caused harm in the same ways as lack of exercise, stress or poor diet. 

Rather than air pollution being a direct, single cause, it was “almost always one of several contributing factors” that led to earlier death and health complications, Langerman said.

Mining industries, vehicle emissions and veld fires contribute to air pollution

Some of the tools used to measure air pollution include on-the-ground monitors and remote tools. Ground air monitors can accurately test the contents of air to measure pollution in specific locations. Remote tools like satellites can often capture data from larger geographic areas, but may be less accurate.

The South African Air Quality Information System (SAAQIS) manages air pollution information. It combines data from monitors in many locations to form a general picture of air pollution across South Africa. 

SAAQIS collects data on particulate matter. PM2.5 comes from many different sources. In South Africa, the key contributors are the mining and coal industries, vehicle emissions, burning biomass (like veld fires) and dust storms. 

No ‘safe’ level of air pollution

The WHO has published guidelines on the maximum levels of PM2.5 for countries. 

There was no “safe” level of air pollution, Annegarn told Africa Check, but the WHO guidelines estimated the level at which there were major health risks. The latest guidelines, from 2021, say that PM2.5 levels should not be above 5 micrograms per cubic metre (µg/m3) on average per year. 

Whether South Africa is 1.4 times above this level, as claimed, depends on who is measuring, where, and for how long. 

South Africa’s levels of PM2.5 higher than WHO guidelines and national standards

SAAQIS reports levels of PM2.5 across South Africa in real time, and publishes reports of averages over time. 

Real-time estimates, usually updated hourly, can change quickly due to weather and other factors. To get a more general picture of pollution levels, scientists take the average of these estimates over a longer period of time, usually a year. 

The latest available report from SAAQIS was published in 2020. It showed that in 2019, South Africa’s annual average PM2.5 levels were between 20µg/m3 and 30µg/m3, depending on the area. This was four to six times higher than the WHO guidelines – and also higher than South Africa’s national standard of 20µg/m3

SAAQIS was, according to Langerman, likely to provide the most accurate estimates available, because it was regularly updated and contained data from many sources. 

But other platforms also have estimates for South Africa. Swiss company IQAir reported an average PM2.5 level of 21.6µg/m3 for 2019. The University of Chicago’s Air Quality of Life Index (AQLI), using satellite and ground monitoring data, put the 2019 average at 20.8µg/m3

Across all of these platforms, the average annual PM2.5 level for South Africa was more than 1.4 times the WHO guideline. 

PM2.5 estimates also vary greatly between and within cities. For example, IQAir found that in South Africa the lowest 2019 average was recorded in the Karoo, a desert area, with 4.3µg/m3, within WHO guidelines, while the highest average was in the town of Hartbeespoort, about 70 kilometres northwest of Johannesburg, with 60µg/m3

WHO guidelines ‘aspirational’ 

Although the WHO recommends maximum levels of pollutants like PM2.5, in reality few countries are able to meet these guidelines. 

The WHO estimates that almost all of the world’s population lives in areas with air pollution averages higher than the guidelines. Countries also develop their own national standards, which are often higher than the WHO’s. 

Annegarn told Africa Check that WHO guidelines were aspirational and did not account for other factors that governments needed to consider. 

The need to limit air pollution had to be balanced with “the socioeconomic realities of a country”, he said. For example, industries responsible for large-scale air pollution in South Africa also often provide employment to many. 

Some scientists believe that in many parts of South Africa, the WHO guidelines are not attainable

This claim therefore understates the facts.


According to recent studies, high air pollution levels in Johannesburg have reduced life expectancy by 3.2 years.



The Maravi Post would not direct us to the “recent studies” quoted in their article that showed high air pollution levels in Johannesburg had reduced life expectancy by 3.2 years.

But an internet search revealed that in 2019, South African newspaper the Mail & Guardian reported the same figure. It said the estimate came from the Air Quality Life Index (AQLI), a project at the University of Chicago in the US that estimates years of life lost due to air pollution. 

The AQLI includes estimates for Johannesburg over time. But the 3.2 years statistic no longer appears on their website because life expectancy estimates have changed since 2019. 

The AQLI uses WHO guidelines for PM2.5 to calculate life expectancy estimates. In 2021, when the WHO revised the guideline from 10µg/m3 to 5µg/m3, the AQLI estimates were changed to reflect this. 

With the revised WHO guidelines considered, the estimated life expectancy loss in Johannesburg for 2019 increased to 3.5 years. For 2020 – the latest available data – the figure is 3.6 years. And if South Africa’s national standards are used, this decreases to 2.1 years lost. 

The 3.2 years quoted by the Maravi Post is incorrect, drawing on old data and using estimates from before the WHO guidelines were adjusted. 

Estimate the result of complex calculation using satellite and on-the-ground data

The process of estimating life expectancy losses due to air pollution is challenging. The AQLI was developed by combining data from satellite imagery, computer models and ground monitors to estimate average PM2.5 levels around the world. Researchers also used mortality data from the WHO and global burden of disease research. 

All this data is used to calculate, on average, how many years of life a person living in a particular place could lose due to air pollution. Because of the complexity of this calculation, multiple experts told Africa Check that the estimates should be interpreted carefully. 

“Air pollution exposure and the health impacts of air pollution are incredibly complex,” Bianca Wernecke, an air pollution expert at the South African Medical Research Council (SAMRC), told Africa Check. 

While there was a lot of room for error, the AQLI researchers did consider various factors that might have threatened the accuracy of the results, she said. For example, using many different types of data to estimate PM2.5 levels should improve accuracy. 

The researchers also used what experts consider to be the best data available – SAAQIS monitoring data combined with satellite data from the US National Aeronautics and Space Administration (Nasa) and reputable health data from the WHO and the Institute for Health Metrics and Evaluation.

Despite these strengths, Wernecke told Africa Check that the life expectancy values were still “‘best guesstimates’ based on the resources available”. 

There is also uncertainty in trying to pinpoint specific locations, like cities. The AQLI is likely more accurate over larger areas. Even within Johannesburg, people living and working in different areas are exposed to varying levels of risk, which would have different effects on life expectancy. 

Dr Caradee Wright, a specialist scientist at the SAMRC, told Africa Check that she “would be extremely cautious” of these life expectancy estimates.

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