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Air pollution is an environmental-health challenge that many developing and developed countries are struggling to deal with. The purpose of our study was to characterise the ambient air quality during the year 2019–2020 over two urban sites of DiepKloof and Vanderbijilpark which are located on the South African Highveld. The study characterised PM10, PM2.5, SO2, NO2 and O3. Findings were that PM10, PM2.5, SO2 and NO2 ambient concentrations predominantly peaked during the winter season in June, July and August with mean concentrations of 48.6 µg/m3, 29.2 µg/m3, 38.6 µg/m3 and 12.6 µg/m3, respectively for the DiepKloof site while for the Vanderbijilpark site, winter mean for PM10, PM2.5 and SO2 were recorded at 124 µg/m3, 50.7 µg/m3 and 22.1 µg/m3, respectively. The average daily pollutant concentrations of the majority of pollutants were elevated above the WHO air quality guideline limits. Analysis of variance showed the seasonal variations had a significant (all p-values less than 0.01) effect on the variability of pollutant concentrations in both sites. The study attributes these elevated ambient pollutant levels to industrial, domestic and vehicular emission sources that are scattered over the South African Highveld. The study also highlighted the impact of the first lockdown period in South Africa indicating that the first three-week lockdown had a significant (p-values less than 0.001) impact on the variability of pollutant concentrations in both Diep Kloof and Vanderbijlpark. The study also established that pollutant concentrations were more significantly affected by wind direction in the more industrialized Vanderbijlpark than in Diep Kloof. The study contributes towards air quality monitoring and management policy formulation both in South Africa and other African countries. Furthermore, the study contributes towards the academic body of knowledge. To curtail pollutant emissions governments have several options including tightening the air quality regulatory frameworks as well as establishing and supporting community-based air quality advocates. Air quality advocates can act as a conduit in raising general public awareness regarding the impact of air pollution on human health.