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Air Quality Monitoring Network

In its "State of the Environment" report of 1998, the CMC implemented the guidelines and air quality banding system as adopted in the United Kingdom. This was as the result of extensive research by the UK’s Department of the Environment’s "Expert Panel on Air Quality Standards" (EPAQS) which is linked with
health advice from the UK’s department of Health’s "Committee on the Medical Effects of Air Pollutants" (CMEAP). The guideline system used in South Africa is at present under review.

It is important to note that these standards include a "safety margin".

The UK Standards and explanation thereof are detailed below as taken from the AEAT WEb site.

Standards for air pollution are concentrations over a given time period that are considered to be acceptable in the light of what is known about the effects of each pollutant on health and on the environment. They can also be used as a bench mark to see if air pollution is getting better or worse.

An exceedence of a standard is a period of time (which is defined in each standard) where the concentration is higher than that set down by the standard. In order to make useful comparisons between pollutants, for which the standards may be expressed in terms of different averaging times, the number of days on which an exceedence has been recorded is also given in many of the tables.

The standards adopted in the UK are the National Air Quality Standards, part of the National Air Quality Strategy adopted by the government in January 2000. A summary of these standards is given in the table below.


Summary of objectives of the UK National Air Quality Strategy


Pollutant
Standard
concentration measured as
Objectives To be achieved by
benzene 5ppb
(16.25µg/m3)		 running annual mean 16.25µg/m3 (5ppb) 31st December 2003
1,3-butadiene 1ppb
(2.25µg/m3)		 running annual mean 2.25µg/m3 (1ppb) 31 December 2003
Carbon monoxide 10 ppm
(11.6 mg/m3)		 running 8-hour mean 11.6 mg/m3 (10 ppm) 31 December 2003
Lead 0.25µg/m3 annual mean 0.5 µg/m3 31 December 2004
0.25 µg/m3 31 December 2008
Nitrogen dioxide* 150ppb
(287µg/m3)		 1 hour mean 200µg/m3 (105ppb),
not to be exceeded more than 18 times a year		 31 December 2005
    40µg/m3 (21ppb), annual mean 31 December 2005
Nitrogen Oxides**       30µg/m3 (16ppb), annual mean 31 December 2000
Ozone 50ppb
(100µg/m3)		 running 8-hour mean 100µg/m3 (50ppb),
daily maximum of running 8-hour mean, not to be exceeded more than 10 times per year		 31 December 2005
Particles (PM10) 50µg/m3 24-hour mean 50µg/m3,
not to be exceeded more than 35 times a year		 31 December 2004
    40µg/m3,
annual mean		 31 December 2004
Sulphur dioxide 100ppb
(266µg/m3)		 15 minute mean 266µg/m3 (100ppb),
not to be exceeded more than 35 times a year		 31 December 2005
    350µg/m3 (132ppb),
1 hour mean, not to be exceeded more than 24 times a year		 31 December 2004
    125µg/m3 (47ppb),
24 hour mean not to be exceeded more than 3 times a year		 31 December 2004
    20µg/m3 (8ppb), annual mean 31 December 2000
    20µg/m3 (8ppb), winter mean
(1 October to 31 March)		 31 December 2000
ppm = parts per million; ppb = parts per billion; µg/m3 = microgrammes per cubic metre *The objectives for nitrogen dioxide are provisional **Assuming NOx is taken as NO2.

Details of the "banding" System are described below
  SULPHUR DIOXIDE (15 minute average)
CATEGORY RANGE
(µg/m3)		 HEALTH EFFECT
LOW <266 Unlikely that anyone would show adverse effects
MODERATE 267 to 526 Little evidence to suggest that those suffering from asthma would be significantly affected. This figure was accepted by the EPAQS as the lowest level at which clear, though rather small, effects have been described.
HIGH 527to 1050 The WHO has suggested that exposure to 1050µg/m3 may lead to significant narrowing of the airways for asthma sufferers. For most people the effect would not be large. Exposure to such concentrations may add to the effect of exposure to other pollutants and allergens and this asthmatics need to be warned that they may need to increase their medication.
VERY HIGH >1050 More asthmatics may experience adverse effects and should be encouraged to ensure they have adequate supply of their "reliever inhaler"

NITROGEN DIOXIDE (1 hour average)
CATEGORY RANGE
(µg/m3)		 HEALTH EFFECT
LOW <287 Very unlikely that anyone would show adverse effects
MODERATE 288 to 564 Studies of volunteers, including asthmatics, do not provide evidence that significant effects on health are likely. Some increase in the response of the lung that produce narrowing of the airways has been recorded. Again the studies are inconclusive and the effects small
HIGH 564 to 752 Studies have shown small direct effect on indices of lung function. In addition there is evidence from epidemiological studies of the effect of mixtures of pollutants with nitrogen dioxide in this range, that adverse effects on health may occur. Should effects occur, those with pre-existing disease of the heart or lungs would be likely to be at risk (see below)
VERY HIGH >752 Those suffering from long standing diseases of the heart and lungs should be aware that their condition may worsen as concentrations of nitrogen dioxide move into the "very high" band. Individuals suffering from asthma dot not appear to be at such increased risk on exposure to nitrogen dioxide as they are on exposure to sulphur dioxide.

PARTICULATE MATTER (24 hour average)
CATEGORY

 RANGE
(µg/m3)
 HEALTH EFFECT
LOW <50 25µg/m3 (ie from 25µg/m3 to 50µg/m3), a city with a population of 1 million could expect one more admission to hospital for treatment of respiratory disease.
MODERATE 50 to
75		 For an increase in concentration of 25µg/m3  (ie. from 50µg/m3 to 75µg/m3), a city with a population of 1 million could expect one more admission to hospital for treatment
of respiratory disease.
HIGH 75 to
100		 For an increase in concentration of 25µg/m3  (ie from 75µg/m3 to 100µg/m3), a city with a population of 1 million could expect one more admission to hospital for treatment
of respiratory disease.
VERY HIGH >100 Those suffering from disease of the heart and lungs may experience a worsening
of their symptoms and should if necessary, consult their doctor. A great majority of people may experience no effect at all.

CARBON MONOXIDE (8 hour average)
CATEGORY RANGE µg/m3 HEALTH EFFECT
LOW <11600 "Low" levels of air pollution.
MODERATE 11700 to 16240 This level of exposure leads to a saturation of haemoglobin of about 2.5%. At this level there is some evidence to show that those with angina and other heart diseases may experience a more rapid onset of chest pain on exercise.
HIGH 16340 to 22000 "High" levels of air pollution. Exposure to 20 ppm ( 22 000 µg/m3) of carbon monoxide leads to a saturation of 4.5%. At these saturations it has been shown that there is a reduction in peak exercise capacity of healthy subjects and a reduction in the time needed for anginal pain to appear on exercise in those with heart disease. Whether such patients are likely to take sufficient exercise to reveal these effects is questionable but they should be aware that such effects may occur.
VERY HIGH >22000 As concentrations of carbon monoxide rise above 20 ppm ( 22 000 µg/m3) then so the percentage saturation of haemoglobin will increase. Effects on those with heart disease become more likely. It should be recalled that sufficient outdoor exposure to reach these levels of saturation is unlikely.



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