According to statistics urban air pollution is linked to up to 2 million premature deaths world-wide each year.
The World Health Organisation (WHO) air pollution database collected data on the outdoor (or ambient) air quality of 1600 cities from 91 countries. The database revealed that unsurprisingly, as the most populated city in South Africa, Johannesburg is highly polluted with the Highveld and the Vaal listed as priority area. Durban may have one of the best air pollution ratings but it is still above the global average.
Take a look at South Africa's air pollution stats: