consistently rank air pollution as a major environmental concern. The
state of our air is an important factor in the quality of life in
Australian cities. It affects the health of the community and directly
influences the sustainability of our lifestyles and production methods.
Quality Section of the Department of the Environment, Water, Heritage
and the Arts seeks to protect and improve urban air quality through
national action to reduce emissions of major air pollutants. The
Department's focus is on those sectors that make the greatest
contributions to adverse air quality as well as those pollutants that
continue to pose threats to the environment and human health.
action can relate to the implementation of relevant national standards
and strategies and a common approach to monitoring air quality, research
to inform air quality policy and community education on air quality
National policies and programmes relate principally to the reduction of emissions from three sectors:
National initiatives aim to reduce the impact of road transport on
environment quality, urban amenity and human health. People's is also targeted, including promotion of bicycle use for short journeys.
and dispersed sources of pollution, such as heating with wood, back
yard burning and domestic appliances, are small but numerous, and as the
National Pollutant Inventory shows, can be significant sources of air
pollutants. Another emerging issue is .
- Industry: Emissions from larger industries are reported under the and are subject to State/Territory control programmes.
Bacteria and viruses
Bacteria are ubiquitous
in the air and general environment. They can cause adverse human health
effects and deterioration of building materials when they proliferate
in indoor environments (Stetzenbach 1998). The health effects of
bacterial exposure in indoor air will depend on the species and the
route of exposure.
The bacteria in
building air can come from airborne sources from the wind’s action on
soil and vegetation, compost, municipal landfills, sewage sludge, etc.
They can also be a direct result of human activity, such as breathing,
coughing and sneezing, or they may colonise the ductwork of the cooling
systems, the water cooling towers (eg Legionella spp) or interior building materials and furnishings such as wallboard, wallpaper and flooring (Bates 2000).
In indoor environments, bacteria usually grow in areas with standing water such as water spray and condensation areas of air conditioning systems (Stetzenbach 1998).Dirty
or poorly maintained air handling systems can become contaminated over
time by bacterial populations that thrive on moisture-laden surfaces
caused by water condensation. Legionella is probably the most common group of bacteria mentioned in association with airconditioning systems (see below).
Viruses are important
airborne organisms and a significant contributor to occupational
absenteeism. Examples of important viruses include the causative agent
of the common cold (rhinoviruses) and the flu (influenza viruses types
A, B, C, etc). The spread of these illnesses can be aided by inadequate
ventilation levels within a building (Stuttard 1996). Viruses cannot
multiply outside the human host, but can survive and remain infective
for extended periods in the warm recirculating airspace of the modern
Routine testing for
airborne viruses is expensive and not generally recommended. However a
useful correlation between the levels of some airborne bacteria,
particularly the Micrococcus group, and poor ventilation levels has been
noted, and these can thus be used as an indicator of potential
cross-infection problems (Stuttard 1996).
Legionella bacteria are
common microorganisms of concern. They occur naturally in small numbers
within soil and water. However, the danger occurs when the bacteria are
present in warm, moist environments such as cooling towers in
air-conditioning plants, where they can multiply rapidly. Evaporative
air conditioning units such as those used in homes and many business
premises are not a likely source of legionella infection.
infections are contracted outdoors, but predominantly in areas
associated with cooling tower systems used to treat indoor air.
Legionella infection control must therefore be included in discussions
about indoor air quality. Legionella outbreaks have been recorded as a
result of building air inlet pipes being positioned directly underneath
air outlet pipes (Bates 2000).
As noted in the State of the Environment
report (DEST 1996), inhalation of droplet aerosols (very fine droplets
of water) containing legionella bacteria can cause legionnaire’s
disease. Sources of droplet aerosols include spray drifts vented from
cooling towers into the atmosphere.
Poorly maintained spa
pools can also be a source of legionella infection. Spas are normally
heated to about 37°C and use air and water jets to produce turbulence.
These conditions result in rapid growth of undesirable organisms,
including legionella. These organisms may be transmitted readily to
humans by inhalation of the aerosols created by the air and water jets.
In recent years there
have been reports of legionnaire’s disease cases associated with the use
of potting mix. Australian studies have found legionella species
present in over 70% of commercial potting mix samples. The route of
transmission of the bacterium from potting mix is not clearly
established and is the subject of further studies.
is a rare form of pneumonia with a relatively high mortality rate of up
to 20%. It represents 1% of pneumonia cases in Australia, with around 180 cases a year reported nationally. The most serious outbreak in Australia occurred in 1987 in Wollongong,
when 44 cases were reported and 10 deaths resulted. Early symptoms
resemble those of flu and include headache, fever, chills, muscle aches
and pains and generally a dry cough followed by shortness of breath.
Other body systems can sometimes be affected, resulting in diarrhoea,
mental confusion and kidney failure. Legionnaire’s disease can be a very
serious illness, particularly in the elderly, heavy smokers, people
with respiratory diseases and people with an immune deficiency.
Currently, there is no
vaccine for preventing legionnaire’s disease and total eradication is
impossible because legionella is widespread in the environment. Instead,
control measures aim to prevent exposure by preventing the growth of
legionella in cooling towers, warm water systems and spas. Control
mechanisms consist of regular maintenance, including chemical treatment.
The Australian Commonwealth,
States and Territories do not have a common regulatory approach to the
control of legionella. The National Environmental Health Forum (NEHF)
has produced guidelines for the control of legionella (see below). The
NEHF publication Water No. 1 Guidelines for the Control of Legionella includes an appendix on the regulatory approaches by Australian States and Territories.
AS/NZS 3666.3:2000 outlines a performance-based approach to the maintenance of cooling water systems and for the control of Legionella
spp and other microorganisms in such systems. This approach combines
automatically regulated water treatment with monitoring, assessment and
control strategies to help create a low-risk environment in the cooling