The graph shows the average annual PM₁₀ and SO₂ concentrations for the GCR compared to the national air quality standard (NAQS) (PM₁₀ = 50µg/m³; SO₂ = 19ppb). When either pollutant is less than 1, this means that pollution levels comply with the NAQS and that the air quality is not harmful to people. The average concentration for SO₂ was within NAQS for the assessed period (2000-2011), however PM₁₀ exceeded the standard for healthy air quality from 2005-2011.

The deterioration of air quality due to PM₁₀ concentration may be the result of the limited number of air quality monitoring stations prior to 2005 and the location of stations in areas of relatively good air quality. After 2005, there was an increase in the number of air quality monitoring stations across the GCR to include areas with poorer air quality, such as Ivory Park and Diepsloot.