Upper Hunter Fine Particle Characterisation Study

The study aimed to determine:

• the major components of PM_2.5 particles that communities in Muswellbrook and Singleton are exposed to
• the relative abundance and sources of the identified components and
• if there are any weekly and seasonal changes in PM_2.5 particles in the Upper Hunter.

The project was jointly funded by the former 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.

Department 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.

PM_2.5 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 PM_2.5 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.

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

The Upper Hunter Air Quality Monitoring Network, comprising 14 air quality monitoring stations, was established in 2010 to address community concerns about air quality in the Upper Hunter. Higher levels of PM2.5 concentrations were measured in Muswellbrook during winter, prompting questions about the sources of fine particles in the Upper Hunter.

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 the Department of Climate Change, Energy, the Environment and Water commissioned a research study to better understand the composition and sources of fine particles in the Upper Hunter.

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

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

The chemical composition data was then analysed using an internationally recognised statistical technique called positive matrix factorisation (PMF) for identifying sources. In the first step, the PMF 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 PM_2.5 concentrations.

The factors and associated potential sources for Singleton, ranked by contribution to annual PM_2.5 concentrations, are:

The factors and associated potential sources for Muswellbrook, ranked by contribution to annual PM_2.5 concentrations, are:

PM_2.5 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.

The main goal of this study was to identify the particle sources that contribute to PM_2.5 in Singleton and Muswellbrook, as these particles have the greatest impact on public health. The bulk of coal dust emissions are coarser than PM_2.5. 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, unlike other studies carried out in Australia where soil fingerprints did not include black carbon. The black carbon in the soil fingerprints appeared with other elements 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 was 1 per cent of total PM_2.5 at Singleton, and 4 per cent of total PM_2.5 at Muswellbrook. These percentages were 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 during mining activity.

This study contributed significantly to improving the understanding of the composition of fine particles and the likely sources of the PM_2.5 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.

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 PM_2.5 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 PM_2.5 and mortality from all causes and cardiopulmonary causes.

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

Before the study began, the three local councils involved in the Upper Hunter Air Quality Monitoring Network were briefed on the study outline (PDF 29KB) on 21 and 28 November 2011.

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

• 1st progress report (PDF 623KB) - site commissioning and methods
• 2nd progress report (PDF 220KB) - summer sample collection
• 3rd progress report (PDF 317KB) - winter sample collection