Understanding Cape Town’s air quality

The right to clean air is a basic human right. The quality of air is a key factor affecting the health of a city as air pollution represents a major health risk to residents. Air pollution is broadly defined as any change in the environment that is caused by substances emitted into the atmosphere from any activity. This change can have a negative effect on human health or well-being, or on the composition, resilience and productivity of natural or managed eco-systems.

Three main types of air pollutants are measured and reported on by the City of Cape Town, as follows: 

  • Nitrogen dioxide (NO2)
  • Sulphur dioxide (SO2)
  • Particulate matter (PM10)

Nitrogen dioxide, a brownish-coloured gas, is mainly produced as a result of burning fossil fuels. Some NO2 is found naturally in the atmosphere and is produced by lightning, plants, soil and water. In Cape Town, motor vehicle emissions, and the burning of industrial and domestic fossil fuels are sources of NO2. Human health is affected by NO2, with increased likelihood of respiratory problems due to the air pollutant inflaming the lining of the lungs and reducing immunity to lung infections. Wheezing, coughing, colds, flu, and bronchitis can be a result of this. Children with asthma and older people with heart disease are most at risk.

Sulphur dioxide, a strong-smelling pollutant, is emitted predominantly by coal-fired power stations. Diesel engines are also significant sources of SO2. Industrial activities processing materials containing sulphur are additional contributors.  In Cape Town the primary source of SO2 is from vehicle emissions and industrial activities. SO2 irritates the nose, throat and airways, causing coughing, wheezing, shortness of breath, or a tight feeling around the chest. People with asthma or similar conditions are most at risk.

Particulate matter consists of the tiny particles in the air, such as soot, dust, smoke, pollen, ash, aerosols and droplets of liquid. PM10 refers to particulates that are smaller than 10 microns in size. The most common sources of PM10 in Cape Town are diesel-vehicle emissions, wood and fuel-burning, and dust from construction activities and unpaved roads and verges. The small size of PM10 enables the matter to be inhaled easily by humans. Constant inhaling of PM10 may adversely affect human health through lung irritation and aggravating lung disorders and diseases such as asthma and tuberculosis. Cardiovascular problems are also linked to PM.

Standards and guidelines

The National Ambient Air Quality Standards (NAAQS) were released in 2009 by the Department of Environmental Affairs. The standards contain requirements in terms of acceptable levels of pollutants permitted in ambient air and are outlined in Table 8. All municipalities are required to meet these national standards by developing and implementing air quality management plans. The aim of air quality management plans is to improve air quality, thus decreasing environmental and human health risks.

NAAQS were set using epidemiological studies on the impacts of air pollution on human health. An estimate of air pollution exposure for a community can be determined by comparing the monitored ambient air quality against national standards. If the comparison exceeds national standards, it is indicative of possible health risks and impacts. Thus, enforcement of compliance with air quality limits in terms of the Air Quality Act is a major contributor to effective air quality management.