约翰内斯堡的空气质量

How clean is the air in Johannesburg, South Africa?

Johannesburg, informally known as Joburg, or "The City of Gold", is the largest city in South Africa, and is classified as a megacity. It is one of the 50 largest urban areas in the world. The city is located in the mineral-rich Witwatersrand range of hills and is the centre of the large-scale gold and diamond trade. In 2019 the estimated population was just over 5 million people for the city and twice that for the metro area.

In the second quarter of 2021, Johannesburg was experiencing a period of “Moderate” quality air with a US AQI reading of 87. This is in accordance with recommendations from the World Health Organisation (WHO). The recorded levels of pollutants were as follows: PM2.5 - 29.4 µg/m³, PM10 - 47 µg/m³, nitrogen dioxide (NO₂) - 30.9 µg/m³ and sulphur dioxide (SO₂) - 7.5 µg/m³. With concentrations at these levels, you are advised to close doors and windows to prevent more polluted air from entering the house. And those of a sensitive disposition should avoid all types of outdoor activity until the air quality improves considerably.

Is the quality of air consistent throughout the year?

Looking back at historic figures from previous years, it can be seen that the air quality in Johannesburg is of “Moderate” quality for about 10 months of the year. This means that the recorded figures are between 12.1 and 35.4 µg/m³. In 2020, only June and July recorded worse figures of between 35.5 and 55.4 µg/m³ which classified it as being “Unhealthy for sensitive groups”.

Figures were recorded from 2019 with an average annual result of 25.3 µg/m³ and showed a slight improvement in 2020 with a mean figure of 22.3 µg/m³.

The air quality not only differs from month to month, but it can change daily, depending on the weather conditions and other factors. By glancing at the table published on the IQAir website (at the top of this page), the quality can be seen to change from day to day.

What can be done to improve the air quality in Johannesburg?

As far back as 2015, the technology company, IBM proposed forming a partnership with the Council for Scientific and Industrial Research (CISR) and the City of Johannesburg (COJ) to help tackle the problem of air pollution. Advanced technology such as the IoT (Internet Of Things) could be used to predict the repercussions of certain measures. Information from several sources including the City of Johannesburg, the City of Tshwane and the Vaal Industrial Triangle will be analysed and computer-generated forecasts made as to what would happen under certain circumstances.

IBM's advanced decision analytics together with IoT technologies, combined with cognitive computing to both ingest and learn from the huge amounts of “big data”, will help to create precise air pollution forecasting systems for the city. One major problem to overcome is the variety of sources of pollutant emissions, like those from vehicles, domestic fuel burning, veld fires, volatile organic compounds from trees and others that can lead to high levels of air pollution.

What causes the air to be polluted?

Air pollution has various sources, but most of the pollutants come from incomplete combustion processes in road traffic, industrial plants and power stations, and from private households. Particulate matter, which is defined as particles with a diameter of less than 2.5 micrometres (PM2.5), is considered to be the greatest problem to health because of its microscopic size.

At the same time, methane and ozone also have an impact on climate change. Reducing them is therefore beneficial not only for people’s health but also for climate change mitigation.

It is reported that one of the main problems facing Johannesburg is the fact that it used to be a mining town as is still surrounded by the dumping grounds the mines created. The other problem it caused was that many more people than were intended came to settle in the area which resulted in a huge increase in traffic volume and the problems associated with that.

How poor is the air quality in Johannesburg?

For the four million people in Johannesburg, their air means people die three years earlier than they would if they were living in Cape Town and breathing their cleaner air. For at least 50 per cent of the time, the air in Johannesburg is unsafe. This is due to a mixture of dust blown into the city, exhaust fumes from the nearly five million vehicles in Gauteng, fires in homes, and pollution from small industries and power stations.

Using pollution measurements from satellites, researchers have concluded that the air in Johannesburg is the worst in the country and costs people 3.23 years of their life. The second-worst place was Sedibeng district municipality, which is slightly south of Johannesburg, which includes an area where heavily polluting industries such as Sasol and ArcelorMittal are located. People in the Tshwane metro municipality which is north of Johannesburg, lose 2.82 years of their life through living in the city.

By contrast, the air in Cape Town is thought to be 90 per cent better than Johannesburg and does not detract from the average lifespan.

What impact does Johannesburg’s poor quality air have on our health?

In several of South Africa’s major cities, the air is often so polluted that it is killing them. Everybody is affected by this as we all have to breathe. It is estimated that the poor air quality in Johannesburg is robbing the lives of 54 people every day!

The data on what exactly is in the air has long been a secret between the regulators and those responsible for the emissions. However, this is not now the case. There is an established website (saaqis.environment.gov.za) where all information is now readily available for all to see. There is also an app that can be downloaded to a suitable smartphone for information “on-the-go”.

Children are particularly susceptible as they breathe faster than adults and are often more active. After a period of heavy exertion, the particles lodge deeply in the lungs. Any pollutants which are carried by the particles soon break away and start to poison the new host.