Air Quality Monitoring
As part of its commitment to a healthier environment, the Alexandra
Renewal Project established an air quality station for the
ongoing monitoring of air pollution levels in Alexandra.
It is important to get an indication of the levels of air pollution
to which people are exposed and to look at seasonal variations in
pollution levels; to measure particulate pollution; ozone [O3] and
carbon monoxide [CO]. A weather station at the monitoring site is also
important.
The system operator (the Air and Noise Quality Division of the City
of Johannesburg), is responsible for accessing the data on a daily
basis, for analysing the data and for producing reports.
Levels of pollution are monitored for the following pollutants:
Potential sources and effects of pollutants:
|
INDICATOR |
SOURCE |
EFFECTS |
|
SO2 |
Mainly fossil fuel burning from coal fires for heating
and cooking purposes, and from industries that use boilers. There is also
a small amount of sulphur in diesel, which is in the process of being
reduced [the reduction started this year and will carry on next year]. |
High concentrations can give rise to severe bronchoconstriction and chemical bronchitis and tracheitis. Asthmatics,
the elderly, and
children are much more susceptible to these conditions. The long term effect is chronic bronchitis. |
|
NO
[primary pollutant]
and
NO2 [secondary pollutant] |
Major sources include fossil fuel burning [e.g. power
generation,
heating and motor vehicles] tobacco smoke, gas fired appliances and oil
stoves.
|
Lung oedema, increase in antioxidant metabolism,
increase in lung
enzymes associated with cell injury. Long term exposure can result in
emphysema like
structural changes such as thickening of the alveolar capillary membrane,
loss of ciliated epithelium, and formation of collagen at atypical points
of the lung. |
|
O3 |
This is a secondary pollutant. It is formed when solar
radiation
[UV light] reacts with NO2 and volatile organic compounds [non-methane
hyrocarbons]. The latter comes from motor vehicle emissions, coal burning
and natural sources. |
O3 is a powerful oxidant and can react with virtually
every class of biological substance [e.g. oxidation of sulfhydryl groups
and amino acids of
enzymes, co-enzymes, proteins and peptides, and oxidation of
polyunsaturated fatty acids to fatty acid peroxides]. Therefore, membranes
are targeted by O3. Cells or organelles may be extremely vulnerable. O3
damages all parts of the respiratory tract. |
|
CO |
CO is a product of incomplete combustion of
carbon-containing
materials [coal, wood, motor vehicle emissions, etc.] and is produced by
some industrial and biological processes. |
CO reacts with haemoglobin [this is the substance in
the blood which carries oxygen to form carboxyhaemoglobin]. The blood has
a much higher affinity for CO than for O2. The effects of high
concentrations are cardiovascular, neurobehavioural, fibrinolysis and
perinatal effects. |
|
Particulate matter
PM10
and
PM2,5 |
Particulate matter comes from unpaved roads, quarries
and combustion processes [e.g. coal burning, motor vehicle emissions,
industry]. It can be organic and/or
inorganic of nature, solids or liquid. The sizes are important:
PM10 - particles smaller than 10 microns diameter penetrate the lower
respiratory tract below the larynx [bronchi & bronchioli].
PM2,5 - particles smaller than 2,5 microns diameters penetrate deep into
the lungs; the alveoli. |
Decrease of pulmonary function, slower clearance of
particles
from the lungs, emphysema, carcinogenic effects. |
Through consistent monitoring, the baseline for the above
parameters has been determined for Greater Alexandra. The baseline is
then compared with the internationally accepted standards and
guidelines [i.e. the US Environmental Protection Agency Standards and
the World Health Organisation Guidelines], and with incoming data.
Where indicators exceed the baseline or the accepted standards and
guidelines, focused interventions can be identified and implemented to
address key pollutants at source and to improve air quality in
Alexandra through appropriate remedial actions.
|
