Particulate matter sources and effects
Everyone is affected by the quality of air that we breathe, and has an
interest in ensuring the ongoing availability of safe, clean air. For the most
part, Australians enjoy clean air which has been getting cleaner in recent
decades. The NSW Environmental Protection Authority (EPA) reported that:
In terms of overall air quality in New South Wales, it has
improved significantly since the 1980s. We have seen a steady decline in the
order of 20 to 40 per cent in some of the key pollutants such as ammonia,
carbon monoxide, lead and sulphur dioxide as well as the oxides of nitrogen and
volatile organic compounds.
It was clear throughout the inquiry, however, that air pollution is
still a significant problem for certain parts of the Australian population. The
Commonwealth Scientific and Industrial Research Organisation (CSIRO) provided a
definition of air pollution for the committee:
Air pollution refers to the presence in the atmosphere of
chemicals, particulates, or biological materials that cause discomfort,
disease, or death to humans, damage other living organisms such as food crops,
or damage the natural environment or built environment. Examples of air
pollutants include particulates, oxides of sulphur and nitrogen, carbon
monoxide, volatile organic compounds, toxic metals (such as lead), ground-level
ozone, and odours.
Particulate matter (PM) refers to everything in the air that is not a
gas; with the PM and air mixture referred to as aerosol. It includes both solid
particles and vapours (liquid particles). Particulate matter is highly
heterogeneous in size and composition. PM is often chemically active in the
environment and in humans, can be transported long distances in the atmosphere,
and can influence weather and climate.
The total mass of PM in the air is referred to as TSP (total suspended
The particles of most concern for human health are those than can enter the
lungs, namely particles less than 10µm (1µm
= 1 thousandth of a millimetre) in diameter (PM10) and
particles less than 2.5 µm
in diameter (PM2.5).
There are many sources of particulate matter included natural and
anthropogenic sources. In Australia PM load naturally fluctuates due to
airborne dust, sea salt, and smoke from bushfires. PM is categorised as primary
or secondary depending on its source.
Primary particles originate from both anthropogenic and natural sources.
Natural sources are derived from processes that occur naturally in the earth
system, such as bubbles bursting on the sea surface which release sea salt
aerosol into the atmosphere, wind-blown dust, and smoke from naturally lit
bushfires. Anthropogenic sources result from human activity and include: dust
associated with agriculture, mining, urban developments, and road traffic;
smoke from deliberately lit bushfires, prescribed burning, and household wood
heaters; emissions from vehicle exhaust, industrial processes, and commercial
activities; and spray drift from aerial application of agricultural and
Secondary particles are formed by chemical reactions in the atmosphere
that result in gases being converted to particles, which are also known as
secondary aerosols. These conversions lead to the production of a large number
of very small particles (nucleation) and the growth in size of existing
These processes are represented graphically below:
Figure 1 – Schematic of atmospheric aerosol sources
It was put to the committee that the combination of natural and
anthropogenic sources makes the controlling of emission of PM challenging.
An example of the interplay between natural and anthropogenic sources in
the production of PM is provided by the Sydney Particulate Study which
demonstrated that local urban sources (motor vehicles, wood combustion, and
industrial sources) may contribute less than fifty per cent of the fine
particle mass in Sydney, with background sources (dust, smoke, sea salt,
biogenic) comprising the remainder.
The sources of different sizes of PM are as follows:
PM10 – 2.5 primarily is derived from suspension or
re-suspension of dust, soil, and other material from roads, farming, mining,
and dust storms but also includes sea salt, pollen, mould, and spores;
PM2.5 primarily is derived from direct emissions from
combustion processes, such as petrol and diesel vehicles, wood burning, coal
burning for power generation, and industrial activities such as smelters,
cement plants, paper mills, and steel mills; and
PM0.1 results from combustion related sources and
atmospheric photochemical reactions.
On-road motor vehicles and off-road engines such as generators, mining,
earthmoving equipment and ships were cited to the committee as the main sources
of anthropogenic particulate pollution in Australia.
There are a number of indoor pollutants and emission sources that may be
harmful to human health but are, in many cases, not regulated. Some of these
are tabulated below:
MAJOR EMISSION SOURCES
House dust, domestic animals, insects
Fire retardant materials, insulation
Metabolic activity, combustion activities, motor vehicles in
Fuel burning, boilers, stoves, gas or kerosene heaters, tobacco
Particle board, insulation, furnishings
People, animals, plants, air conditioning systems
Outdoor air, fuel burning, motor vehicles in garages
Adhesives, solvents, building materials, volatilization,
combustion, paint, tobacco smoke
Re-suspension, tobacco smoke, combustion products
Polycyclic aromatic hydrocarbons
Fuel combustion, tobacco smoke
Outdoor air, trees, grass, weeds, plants
Soil, building construction materials
Soil, plants, foodstuffs, internal surfaces
Outdoor air, fuel combustion
It was argued to the committee that there is a need to explore what
standards or regulations may need to be put in place as building energy
efficiency increases in order to balance efficiency gains against potential
health costs, as energy efficiency gains often come at the cost of reduced
Health impacts of poor air quality
There is a substantial body of evidence indicating that particulate
matter has negative impacts on human health – regardless of the size of
A study published in the Lancet in 2012 found 'ambient particulate matter
pollution' to be the ninth leading cause of global disease burden.
The National Health and Medical Research Council-funded Centre for Air Quality
and Health Research and Evaluation (CAR), reported to the committee that:
People exposed to the short-term bursts or long-term higher
levels of particulate pollution suffer a range of adverse effects, including:
Increased risk of deaths, particularly due to heart and lung
Increased risk of hospitalisation for heart and lung diseases;
Increased risk of asthma attacks.
It was reported to the committee that the 'main properties of PM that
determine its environmental and health risks are: concentration; size
distribution; structure; and chemical composition.'
The effects on health vary substantially between geographic settings, partly as
a result of variation in the chemical composition of the particulates, which is
dependent on their local sources.
The committee learnt that the size of the PM was the principal
determinant of how deeply it is inhaled into the human respiratory system, with
smaller particles able to penetrate further into the lungs.
As most particles with a diameter >10µm
are generally filtered by the nose and throat, PM10 is typically
used as the threshold value for studies on the effects of PM on human health.
The relative distribution of PM in the human respiratory system is represented
in figure two.
Figure 2 - Deposition of different sized particles in
different segments of the respiratory system
Furthermore, it was argued by the CSIRO that:
Epidemiological studies have concluded that there is a
statistically significant relationship between fine particles and human health
effects, such as decreased lung function, increased respiratory symptoms,
increased chronic obstructive pulmonary disease, increased cardiovascular and
cardiopulmonary disease, and increased mortality. Recent research has
identified a strong link between PM2.5 and life expectancy.
The committee heard that there were particularly high health risks
associated with PM2.5:
PM2.5 is believed to be the most health-hazardous air
pollutant, responsible for 10 to 20 times as many premature deaths as the next
worst pollutant, ozone. Just as 'every cigarette is doing you damage', every
gram of wood smoke or other particle emissions is also causing health problems.
Wood smoke is more hazardous than cigarette smoke – in tumour initiation tests
it was found to cause 12 to 30 times as many cancers as the same amount of
cigarette smoke. The estimated health cost of a kg of PM2.5 emissions in Sydney
is more than $235.
There is also some evidence to suggest that ultrafine particles (UFPs) –
particles less than 0.1µm
in diameter – can be harmful to human health. It was reported by CAR that:
Epidemiological evidence about the adverse health effects
attributable to exposure to UFPs, as distinct from the effects of other
particles (measured as PM10 and PM2.5) is limited at
present. However, toxicological studies in animals and humans have shown
diverse effects on cardiovascular, blood, respiratory and brain function.
Further evidence is required to establish the relevance of these toxicological
findings to population health and hence to gauge the importance of control
measures specifically targeting UFP emissions.
The committee heard that indoor air quality is also critical to human
health, but has not been investigated as fully as the impacts of ambient air
quality which is monitored and controlled to some extent.
A 2002 paper from the Journal of Exposure Analysis and Environmental Epidemiology
found that people in Canada in the United States of America spent only between
six and seven per cent of their time out of doors with the rest either in
buildings or vehicles.
Safe levels of exposure
The committee heard, that at least for some pollutants, there is no safe
level of exposure:
Of importance is that the new evidence not only supports the
previous scientific conclusions but also indicates that the effect can occur at
air pollution concentrations lower than those used to establish the existing
WHO health guidelines, particularly into relation to PM 2.5 and PM 10. So far
no limit of exposure where there is no impact has been identified.
Available evidence suggests that, at least for particulates
and for NO2, there is a linear dose response relationship over a
large range of exposure levels. This means that, even at levels below the
current targets, further health gains can be achieved by further reduction in
This position was supported by the Environment and Sustainable
Development Directorate of the Australian Capital Territory (ACT) who noted
'there is no safe threshold for particulate pollution at which health effects
do not occur.'
A number of submissions to the inquiry made similar points.
Populations most at risk
The health impacts of air quality are not shared equally by all people.
Certain groups of people, and certain geographies, are at a greater potential
risk than others. The populations who are at the greatest risk are those who
are exposed to the largest quantity of harmful particulates, and those who are
inherently more susceptible to exposure.
As noted above, the general Australian population enjoys comparatively
good air quality. According to World Health Organisation (WHO) analysis, annual
average PM2.5 totals in 2010 gave Sydney a rating of seven, the
Lower Hunter a rating of 8.2, New York 13, London 14, and Paris 23.
The committee notes, however, that these ratings are for relatively large urban
areas. Within these areas there are populations exposed to higher levels of air
pollution, and associated health risks. Populations most exposed to particulate
matter are those people living in close proximity to transport corridors and
industrial and agricultural pollution sources. The committee heard that:
The highly urbanised nature of Australia means that a high
proportion of the population are co-located with major transport corridors and
hence highly exposed to transport related emissions.
While air pollution is often considered to be an urban problem, rural
communities are also exposed to PM due to wind-blown dust smoke from controlled
burning, bushfires, wood heaters, and PM from mining and other activities.
The CSIRO noted that 'regional towns co-located with heavy industry (e.g., Gladstone,
Kalgoorlie, Mt Isa, Port Pirie);' are subject to higher risks from impacts of
It was further noted that 'Peri-urban populations (i.e. at the rural–urban
interface)... may be vulnerable to spray drift from agricultural and
The committee also received evidence that risk increases in areas where there
is poor dispersion due to a 'combination of meteorology, topography (e.g.
valleys), and location factors (e.g. coastal regions with land-sea breeze
It was reported to the committee that the segments of society who are
most inherently susceptible to poor air quality are:
Children and the elderly;
Those with pre-existing heart and lung disease; and
Socio-economically disadvantaged groups.
The committee heard that exposure to air pollution can negatively impact
One neglected area I want to highlight is the effect of
pollution during pregnancy. There is now strong evidence that exposure to
particulate matter during pregnancy reduces birth weight and shortens gestation
time. This includes a recent international study of three million births
worldwide and a study that I worked on of just under 1,000 mothers in Logan.
There is also evidence of association between pollution exposure during pregnancy
and stillbirth, and biological evidence of harm from studies finding greater
DNA damage in the placentas of mothers with higher pollution exposure. This
creates a potentially huge economic cost for Australia because we know that
babies born early or underweight spend more time in hospital as children and
have an increased risk of chronic disease in adulthood.
The Australian Medical Association (AMA) also noted that workers in
certain industries and occupations have a heightened risk of experiencing adverse
health impacts due to poor air quality.
There are a wide range of air quality issues that the committee has
considered in the course of its inquiry. On the broadest of levels, the
committee received evidence that global phenomena such as climate change have
consequences for air quality. The committee heard from the CSIRO that:
There is an important nexus between Australia's air quality
and a changing and increasingly variable climate because: a likely increase in
frequency and severity of bushfires and droughts would increase the PM levels
in urban and regional Australia; photochemical smog, which affects all
Australian cities, is influenced by air temperature as well as urban vegetation
and levels of ozone and increased air temperatures due to global warming are
likely to exacerbate the incident and severity of photochemical smog events in
Australian cities; and the effects of air pollution will be in addition to
other stressors that affect human health such as heat stress, with such
combined effects very likely to adversely affect the morbidity and mortality of
While the committee recognises the significant impact of broader
influences on air quality such as climate change and urbanisation, the majority
of evidence received during the course of this inquiry was concerned with more
local and immediate impacts. The committee received detailed evidence around
sources, health impacts, and risk factors in relation to three specific types
of air pollution: coal, diesel, and wood smoke. After a discussion of standards
and monitoring in Chapter 3, the remainder of this report discusses the
evidence and makes recommendations in relation to each of these major sources
of air pollution.
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