Upper Hunter Fine Particle Characterisation Study

What is the Upper Hunter Fine Particle Characterisation Study?

The Upper Hunter Fine Particle Characterisation Study commenced in January 2012 to study the composition of fine particles 2.5 microns and smaller in diameter (PM2.5) in the Upper Hunter Valley towns of Singleton and Muswellbrook.

The study was undertaken to provide communities in Muswellbrook and Singleton with scientific information about what the fine particles are in their local environment.

The final report (UHFPCSFinal.pdf, 5.5MB) provides a full analysis and interpretation of the data collected during this study. A summary report (130722UHVPCSfact.pdf, 150KB) is also available.

What were the aims of the study?

The study aimed to determine:

  • the major components of PM2.5 particles that communities in Muswellbrook and Singleton are exposed to
  • their relative importance and
  • if there are any weekly and seasonal changes in PM2.5 particles in the Upper Hunter.

Who was involved in the study?

The project was jointly funded by the NSW Office of Environment and Heritage and NSW Health, with co-investment from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) as the lead researcher.

OEH staff conducted the sampling at each location. Researchers from CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO) led sample analysis, evaluation and the reporting of results.

Why did the study focus on PM2.5?

PM2.5 is associated with greater health risks than coarser particle pollution. While larger particles generally settle close to their source, smaller particles can remain suspended in the air and be carried over large distances, potentially causing impacts in areas far from their source.

The evidence is clear that long-term exposure to PM2.5 has a larger health effect than short-term exposure, suggesting that strategies that provide long-term reductions in particulate pollution are likely to produce the greatest health benefit.

Why did the study only look at air particles in Muswellbrook and Singleton?

The Upper Hunter Air Quality Monitoring Network (UHAQMN), comprising 14 air quality monitoring stations, was established in 2010 to address community concerns about air quality in the Upper Hunter.

The initial results from the first nine months of data from the UHAQMN (December 2010 to August 2011) showed some evidence of slightly elevated PM2.5 concentrations in Muswellbrook during winter.  Further information on the levels recorded is documented within reports available at www.environment.nsw.gov.au/aqms/uhaqmnmonitoring.htm

As there are multiple sources of PM2.5, including mining, coal-fired power generation, diesel vehicles, road and rail transport, solid fuel heaters and prescribed burning, NSW Health and OEH commissioned a research study to better understand the composition and sources of fine particles in the Upper Hunter. 

The study focused on the Muswellbrook and Singleton UHAQMN sites, as these are major population centres where elevated PM2.5 concentrations have been measured.

How was the study conducted?

Sampling was undertaken at the Upper Hunter Air Quality Monitoring Network sites in Singleton and Muswellbrook between January 2012 and December 2012.

Samples were collected for 24 hours every third day and analysed for organic carbon, elemental carbon, soluble ions, anhydrous sugars, elemental composition, black carbon and gravimetric mass.

The chemical composition of all the samples from each site was analysed using an internationally recognised technique called positive matrix factorisation (PMF).  PMF is widely applied internationally for identifying sources contributing to ambient pollution.

In the first step, the PMF statistical technique is applied to identify correlations between the concentrations of individual chemical species, grouping correlated species into 'factors'.  Factors have distinct chemical patterns or fingerprints.  In this study, eight factors were identified, with this number of factors found to provide the best explanation of the measured data.

Further analysis was then undertaken to identify the most likely source of emissions identified in each factor and the contribution that each source makes to the total PM2.5 concentrations.

What are the factors or chemical fingerprints identified and where do they come from?



Potential source

Factor 1:
wood smoke
Domestic wood heating
Factor 2:
Includes iron and black carbon in addition to copper, manganese, zinc and organic carbon. These species are found in both vehicle and industrial emissions.  Vehicle emissions include brake and tyre wear and fuel combustion emissions
Factor 3:
secondary sulfate
Occurs when gaseous sulfur dioxide emitted to the atmosphere during combustion of fossil fuels (e.g. power stations or motor vehicles) oxidises in the air, in the presence of sunlight, to form sulfuric acid. Ammonia that is emitted from biological production, such as livestock wastes and fertiliser neutralises the sulfuric acid to produce ammonium sulfate particles
Factor 4:
biomass smoke
Bushfires, hazard reduction
Factor 5:
industry aged sea salt
Sea salt and fossil fuel combustion, from sources such as industry and power stations
Factor 6:
Soil dust, fugitive coal dust
Factor 7:
sea salt
Sea salt particles are formed by waves breaking in the open ocean and from coastal surf breaks.  Given that these sea salt particles are very small they are able to be transported hundreds of kilometres inland.
Factor 8:
secondary nitrate
Fossil fuel combustion from sources such as motor vehicles and power stations

What did the study find?

The factors and associated potential sources for Singleton, ranked by contribution to annual PM2.5 concentrations, are:



Contribution of the factor to total annual PM2.5 mass at Singleton

Potential source

Secondary sulfate 20 ± 2% Local and regional sources of SO2 such as power stations
Industry aged sea salt 18 ± 3% Sea salt, local and regional sources of SO2 such as power stations
Vehicle/industry 17 ± 2% Vehicles, industry
Wood smoke 14 ± 2% Domestic wood heaters
Soil  12 ± 2% Soil dust, fugitive coal dust
Biomass smoke 8 ± 2% Wildfires, hazard reduction burns
Sea salt 8 ± 1% Sea salt
Secondary nitrate 3 ± 2% Motor vehicle NO2, power station NO2


The factors and associated potential sources for Muswellbrook, ranked by contribution to annual PM2.5 concentrations, are:



Contribution of the factor to total annual PM2.5 mass at Muswellbrook

Potential source

Wood smoke 30 ± 3% Domestic wood heaters
Secondary sulfate 17 ± 2% Local and regional sources of SO2 such as power stations
Industry aged sea salt 13 ± 2% Sea salt, local and regional sources of SO2 such as power stations
Biomass smoke 12 ± 2% Wildfires, hazard reduction burns
Soil 11 ± 1% Soil dust, fugitive coal dust
Vehicle/Industry 8 ± 1% Vehicles, industry
Secondary nitrate 6 ± 1% Motor vehicle NO2, power station NO2
Sea salt 3 ± 1% Sea salt 

Are there seasonal differences in the PM2.5 observed in Muswellbrook and Singleton?

PM2.5 levels are higher in the cooler months of the year from May to October. Wood smoke dominates at both sites during the winter, but to a greater extent at Muswellbrook.

In summer secondary sulfate and industry aged sea salt are the dominant factors. This is due to the higher contribution of fossil fuel combustion related particles and sea salt during these months, both of which represent large scale regional sources.

What contribution does coal dust make to PM2.5 levels in Muswellbrook and Singleton?

The main goal of this study was the identification of the particle sources that contribute to PM2.5 in Singleton and Muswellbrook, as these particles have the greatest impact on public health. The bulk of coal dust emissions are coarser than PM2.5. A study focused on the identification of a fugitive coal dust fingerprint would have involved the collection of coarser particles.

However in this study the soil fingerprints at both Singleton and Muswellbrook included black carbon. This contrasts to other studies carried out in Australia where soil fingerprints do not include black carbon.

The black carbon in the soil fingerprints in this study appears with other elements that are often associated with windblown dust. The black carbon in the soil fingerprint identified at Singleton and Muswellbrook may result from fugitive coal dust emissions. The amount of black carbon in the soil factor is 1 per cent of total PM2.5 at Singleton, and 4 per cent of total PM2.5 at Muswellbrook. These percentages are relatively low compared to the contributions of major sources. It should be noted that the black carbon in the soil fraction may also include particles from non-road diesel vehicle emissions that are re-suspended during mining activity.

How will the results of this study be used?

This study contributes significantly to improving the understanding of the composition of fine particles and the likely sources of the PM2.5 that the populations in Muswellbrook and Singleton are exposed to. The results from this study add to the evidence base that the NSW Government relies on to inform policies and programs aimed at reducing fine particle pollution.

The NSW Environment Protection Authority (EPA) Upper Hunter Air Particles Action Plan outlines a range of measures that are either in place or being developed to improve air quality in the Upper Hunter and better inform the public. The plan also restates the NSW Government’s commitment to improve the evidence base for action through monitoring and research.

The results and underlying data from this study will also be valuable to future studies in the region.

What are the health impacts of fine particles?

Exposure to particles is a health concern because they can pass through the throat and nose and enter the lungs, where they can cause respiratory and circulation problems, particularly in elderly people, children and people with existing health conditions.

According to the World Health Organisation (WHO), particulate matter affects more people than any other pollutant and its effects on health occur at levels of exposure currently being experienced by most urban and rural populations in developed countries (see WHO, Air quality and health fact sheet).

Short-term and long-term exposure to particulate matter is associated with mortality and morbidity from cardiopulmonary disease. Over the short-term, increases in 24-hour average concentrations of PM2.5 and PM10 are associated with mortality and hospitalizations from cardiovascular and respiratory diseases. In the longer term, a robust association has also been demonstrated between annual average PM2.5 and mortality from all causes and cardiopulmonary causes.

Do particles from different sources have different health impacts?

Currently, the evidence does not indicate that particles from difference sources should be treated differently.  Further research in this field is ongoing and the NSW Government will continue to keep a watching brief on emerging national and international evidence.

Progress reports and consultations

Prior to the commencement of the study, the three local councils involved in the UHAQMN were briefed on the study outline on 21 and 28 November 2011.


A series of progress reports were provided by the researchers throughout the sample collection process.

Related sites

Page last updated: 13 November 2015