Outdoor air pollutants
People with asthma have more sensitive airways and their lungs respond more
to the effects of air pollutants such as particles, sulphur dioxide, nitrogen
oxides and ozone. Outdoor pollutants not especially associated with asthma
include carbon monoxide and lead. Carbon monoxide is more likely to affect
people with heart disease than people with asthma. Lead has become much less of
a problem as an air pollutant since most vehicles now run on unleaded petrol.
Airborne particles
Particles suspended in air are a complex mixture of solids and aerosols and
their composition and size depends largely on their source, which can be natural
(from pollens, bacteria and fungi) or man-made (primarily from combustion
sources such as power stations, petrol-and diesel-powered motor vehicles, wood
heaters, fireplaces and incinerators).
Respirable particles (PM10, particles with diameters less than 10
micrometre) and fine particle (PM2.5, particles with diameters less
than 2.5 micrometres) have been attracting recent attention, largely because
they can penetrate and be retained in the deepest structures of the lung.
Sulphur dioxide
Although natural sources such as volcanoes contribute to ambient levels of
sulphur dioxide, the combustion of sulphur-containing fossil fuels is the
primary source of this gas.
Nitrogen oxides
The major source of nitrogen oxides is the combustion of fossil fuels in
power stations and motor vehicles. In sunlight, nitric oxide rapidly changes
into the secondary pollutant, nitrogen dioxide, although high temperatures (for
example, in power plants and gas heaters and stoves) can also lead to nitrogen
dioxide being emitted directly.
Ozone
Ozone is a highly reactive gas formed in the lower atmosphere by chemical
reactions between nitrogen oxides, oxygen and volatile organic compounds in the
presence of sunlight. The pollutants produced are referred to as ‘photochemical
smog’ and ozone is the most important pollutant in this group. Ozone in the
upper atmosphere is protective by screening out ultraviolet rays.
Air quality standards
In 1998, the National Environment Protection Council made a National
Environment Protection Measure (NEPM) for outdoor air quality which sets
national air quality standards for the six major pollutants: particles (PM10),
sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and lead. These
standards have been set to protect human health.
Ambient air quality goals recommended by the National Health and Medical
Research Council are shown in Appendix 1.
Table 2 NEPM air quality standards and goals
(Note: Table 2 only available on this website)
Pollutant |
Averaging Period |
Maximum Concentration |
Goal within 10 years - Maximum allowable exceedances
|
| Carbon monoxide |
8 hours |
9.0 ppm |
1 day per year |
| Nitrogen dioxide |
1 hour
1 year
|
0.12 ppm
0.03 ppm |
1 day per year
none |
| Photochemical oxidants (as ozone) |
1 hour
4 hours |
0.10 ppm
0.08 ppm |
1 day per year
1 day per year |
| Sulfur dioxide |
1 hour
1 day
1 year |
0.20 ppm
0.08 ppm
0.02 ppm |
1 day per year
1 day per year
none
|
| Particles (as PM10) |
1 day |
50 mg/m3 |
5 days per year |
| Particles (as PM2.5) * |
1 day
1 year |
25 μg/m3
8 μg/m3 |
No limit |
|
|
Air quality index
The Air Quality Index is calculated by converting the measured pollutant
concentrations into index values. The lower the index is, the better the quality
of our air. There are five categories in the index: Very Good (0-33), Good
(34-66), Fair (67-99), Poor (100-149), Very Poor (>150). Air quality is quite good in
most Australian cities with only occasional incidences of exceeding the particle
and ozone standards.
Table 3 City Specific comparison of criteria air pollutants and
compliance to NEPM standards (2000-2001) with number of exceedances in brackets
(Note: Table 3 only available on this website)
Pollutant |
NEPM
Standard |
Highest Measured |
|
Melbourne |
Sydney |
Brisbane |
Perth |
Adelaide |
Hobart |
Canberra |
|
Cabon Monoxide |
8 hour
9.00 ppm |
4.97 (0) |
8.00 (0) |
2.70 (0) |
4.80 (0) |
7.00 (0) |
3.10 (0) |
5.83 (0) |
|
Particles as PM10 |
1 day
50 mg/m3 |
53.00 (1) |
64.10 (2) |
86.8 (5) |
39.60 (0) |
No Data |
69.00 (6) |
56.40 (1) |
|
Ozone |
4 hour
0.08 ppm |
0.07 (0) |
0.14 (5) |
0.09 (1) |
0.08 (0) |
No Data |
No Data |
0.05 (0) |
1 hour
0.10 ppm |
0.08 (0) |
0.16 (3) |
0.12 (1) |
0.09 (0) |
No Data |
No Data |
0.05 (0) |
|
Nitrogen Dioxide |
1 hour
0.12 ppm |
0.07 (0) |
0.08 (0) |
0.06 (0) |
0.07 (0) |
No Data |
No Data |
0.04 (0) |
1 year
0.03 ppm |
0.02 (0) |
0.01 (0) |
0.01 (0) |
0.02 (0) |
No Data |
No Data |
0.01 (0) |
|
Sulphur Dioxide |
1 hour
0.20 ppm |
0.06 (0) |
0.03 (0) |
0.08 (0) |
0.08 (0) |
0.08 (0) |
No Data |
No Data |
1 day
0.08 ppm |
0.01 (0) |
0.01 (0) |
0.01 (0) |
0.01 (0) |
0.02 (0) |
No Data |
No Data |
1 year
0.02 ppm |
<0.01 (0) |
<0.01 (0) |
<0.01 (0) |
<0.01 (0) |
<0.01 (0) |
No Data |
No Data |
|
|
