Pressures are measured according to the common air pollutants which are measured against guidelines and standards which in turn determines the impact on the environment and on health (Grange, 1991).

CARBON MONOXIDE (CO)

Is released mostly by incomplete combustion processes from motor vehicles and the burning of fossil fuels. Suspended particles originate from burning fossil fuels, agriculture, untarred roads as well as mine dust. Mostly from sprays, mists, dust, grinding activities and land clearing

SULPHER DIOXIDE (SO₂ )

Mostly from combustion of coal and oil as well as petroleum refining, metal smelting and paper making and various other industrial processes. Sulphur dioxide and smoke are also known as classical smog. The measurements of SO₂ were discontinued for the last 6 or 7 years due to low readings. However the Soiling Index is still measured in Fordsburg and at the Traffic Department Headquarters.

NITROGEN DIOXIDE (NO₂)

Mostly from automobile engines, medical waste incinerators, fossil fuel combustion and a by-product in the manufacturing of fertilisers.

HYDROCARBONS (HC)

Mostly from vehicles and industrial processes .  Heavy Metals (including lead, mercury and cadmium) and Lead is mostly produced from the combustion of petrol, paint and lead smelting operations. Mercury is produced mostly from paper, chemical and paint manufacturing as well as pesticides and fungicides.

PHOTOCHEMICAL SMOG

Photo-chemical smog, mainly O₃ and NOx, are pollutants found in urban areas as a result of motor vehicles and stationary sources.