The air in South African Highveld cities smells foul within the winter: here’s why

How bad is the standard of the air in Johannesburg?

In winter in parts of South Africa, there is usually a haze within the morning and evening from high levels of air pollution. However, occasionally, it’s possible to smell the pollution, as some South Africans did in mid-June 2022 in lots of areas of Gauteng province. The province is situated in what’s referred to as the Highveld – a high altitude inland area where major cities like Johannesburg are situated. The industrial Highveld is South Africa’s industrial heartland.

Pollution levels within the Highveld are sometimes unacceptably high – even when there’s no smell. The levels are mapped on the South African Air Quality Information System. In some areas pollution levels repeatedly exceed the National Ambient Air Quality Standards.

In Gauteng province, when the wind comes from the east or the southeast, where most industries are situated, residents can sometimes smell the pollution. It can herald hydrogen sulphide (H₂S), which smells like rotten eggs.

There are many sources of hydrogen sulphide, including industrial sources reminiscent of petrochemical plants, open solid mines, coal-fired plants and sewage treatment plants and natural sources. But there’s still an excellent deal of uncertainty about the sources of hydrogen sulphide in the world.

In the winter the particulate matter concentrations repeatedly exceed the national standards at lots of the monitoring stations across the region. For the smallest particles, the 24-hour average standard is 40μg/m³ and the annual average standard is 20μg/m³. Levels ought to be below these numbers. When the ambient levels exceed these numbers, air pollution is unacceptably high. From modelling studies, we see that these high levels are wide-spread across the Highveld.

Some small improvements have been seen in particulate matter concentrations since 2007. But they should not enough to achieve the national standards.

What’s the source of the pollution?

Much of it’s brought on by the burning of fossil fuels. Approximately 86% of South Africa’s primary energy supply is from fossil fuels. To improve air quality over the region, a concerted effort is required across sectors to diminish emissions. The essential sources are coal-fired power stations, industries, vehicles, prescribed burning, solid fuels for cooking and heating and waste burning.

Moving away from fossil fuel sources is a key aspect to improving air quality.

Air pollution levels at the bottom (ambient air pollution) generally have a seasonal cycle. In the Highveld, many pollutants have higher concentrations within the winter. This is due partially to the meteorology of the world. There may be very little rain in winter, and weather conditions are generally calmer. This can trap pollution near the bottom.

Also, air tends to recirculate over the region and accumulate pollution. And in winter, emissions increase because people burn wood and coal for cooking and heating, there are more grass fires, and conditions are dry and dusty.

Particulate matter is small solid or liquid particles within the air that contribute to air pollution. They include smoke and dirt, in addition to small particles created within the atmosphere from reactions of gaseous pollutants. Ambient particulate matter pollution is the leading environmental health risk globally.

Who is most vulnerable?

In South Africa, the ambient concentrations of particulate matter, nitrogen dioxide and sulphur dioxide, in addition to other pollutants, are regulated under the National Ambient Air Quality Standards. These standards were set at levels to guard human health, as all regulated pollutants have negative effects on health.

The people most vulnerable include those that have lung diseases reminiscent of asthma and chronic bronchitis, cardiovascular diseases, infants and young children, and other people over 65 years of age.

The air quality is especially bad in low-income settlements that burn solid fuels for cooking or heating because they’ll’t afford or aren’t connected to scrub energy. The particulate matter concentrations have been found to be higher in these communities than in other communities.

High levels of poor air quality across much of the Highveld region were the premise for the recent decision that confirmed the constitutional right of the country’s residents to an environment that isn’t harmful to their health.

Concerted and dedicated motion is required to enhance the air quality.

What is the impact on health?

Being exposed to air pollution affects people’s health.

South Africa’s annual average levels of particulate matter are generally lower than in another places on this planet, reminiscent of India. But when pollution levels exceed national standards, there may be an issue. It has been estimated that if positive particulate matter annual standards (20 μg/m³) were met across the country, 14,000 premature deaths might have been avoided in 2012.

At low concentrations there aren’t many health effects from hydrogen sulphide despite the smell. As concentrations increase, hydrogen sulphide can irritate the eyes, nose, throat and respiratory system. This happens at levels where the 24-hour average is above 100 ppb, which doesn’t appear to be the case in Gauteng. At very high levels (100 times where people can begin to smell it), hydrogen sulphide may cause lack of smell and more severe health effects. These levels are generally not reached within the ambient environment.

South Africa doesn’t have an ambient standard for hydrogen sulphide and only a couple of stations measure it. California regulates the one-hour average level of hydrogen sulphide at 30 ppb to minimise its odour. Measurements at ambient air quality stations on the Highveld that measure hydrogen sulphide have seen peaks at the extent where the smell could be detected, but not on the high levels where health can be seriously affected.

When people can smell the pollution, it reveals an issue that is frequently “invisible”. Many days, pollution levels are unacceptably high from pollutants reminiscent of particulate matter even when there’s no smell.