Oxenford Air Quality Community meeting questions answered
The former Department of Environment and Science (DES) launched an investigation into air quality in Oxenford in 2020 in response to community concern. The results were released in the Oxenford Air Monitoring Investigation Report. The below questions were raised by community members in relation to the investigation and report.
Why was monitoring only done for PM2.5 and below?
The Oxenford monitoring investigation was designed to determine whether quarry dust emissions posed a health risk to surrounding residents. Studies to date confirm that particles less than 2.5 micrometres in diameter (PM2.5) are most associated with adverse health effects. This is due to the particulate size and its ability to travel deep into human lungs. It was determined that monitoring for PM2.5 was most appropriate for assessing any health risk to the community.
PM2.5 also best matched the respirable particle fraction (particles less than 4 micrometres in diameter, or PM4) on which crystalline silica guidelines for workplace exposure are based. It was not possible to monitor respirable particles (PM4) in the Oxenford investigation as sampling equipment for long-term continuous outdoor particle monitoring is designed to measure PM2.5, not PM4.
Why was only one monitoring site used in the investigation?
The monitoring equipment used for the study required a secure location approximately the size of a car space with no overhanging trees or other structures that could hinder clear sky exposure. The location of the site also had to be within a reasonable distance to the quarry to measure any potential impact from the source. Additionally, the site required access to a power source to run a small air pump and had to be easily accessible by DES officers to replace sample filters and carry out periodic maintenance.
Establishing a second site was hampered by community concerns about COVID-19 and a lack of suitable locations. Given the health concerns of the community, the decision was made to continue the investigation with the one monitoring location and avoid delaying the start of the monitoring program.
Why was the monitoring site located to the west of the quarry and not in the direction of homes on the eastern side?
The site to the west of the quarry complies with the requirements of Australian/New Zealand Standard AS/NZS 3580.1.1 Guide to siting air monitoring equipment. This location was also chosen due to its proximity to other air emission sources with the potential to impact overall air quality.
For a pollutant such as crystalline silica with just one main emission source (the quarry), an estimate of likely pollutant concentrations in areas not monitored can be made based on the frequency of winds blowing from the source to that area compared to the frequency of winds blowing from the source towards the monitoring site. Wind measurements indicate that areas to the east can be downwind of the quarry up to three times more often than the monitoring site. Using the above approach, annual average PM2.5 crystalline silica concentrations in areas to the east of the quarry would not be expected to exceed 0.06 μg/m3, or 20 per cent of the Environment Protection Authority (EPA) Victoria annual guideline.
What are the impacts of long-term respirable crystalline silica (RCS) exposure, even in small amounts?
Queensland Health were consulted on the above question and provided information to support the following response.
In the absence of Queensland or national ambient criteria for crystalline silica, measured respirable (as PM2.5) crystalline silica concentrations were compared against the annual assessment criterion in EPA Victoria's Protocol for Environmental Management: Mining and Extractive Industries (PEMMEI)5. The criterion in this document was adopted from the California EPA Office for Environmental Health Hazard Assessment Reference Exposure Levels (RELs) for respirable crystalline silica. A chronic REL is an airborne level of a chemical at or below which no adverse health effects are anticipated in individuals indefinitely exposed to that level. That is, they are applicable to a life-time exposure. RELs are developed from the best available published scientific data, based solely on health considerations.
Why were the monitoring results compared against workers guidelines?
There is insufficient data on the health effects of some pollutants in outdoor or community exposure settings, or non-occupational exposure, to determine appropriate health protection guidelines. In these circumstances, it is necessary to base the assessment of community health risks on health guidelines developed for occupational (worker) exposure. This was the case for asbestos and crystalline silica in the Oxenford investigation (2021).
Asbestos
In the absence of Queensland or national ambient criteria for asbestos, the results of asbestos monitoring at Oxenford were compared with the asbestos criterion in Safe Work Australia’s Workplace Exposure Standards for Airborne Contaminants. A key finding was the absence of asbestos fibres in any of the samples taken in the Oxenford community downwind of the quarry following blasting events.
Respirable Crystalline Silica
There are no Queensland or national criteria for ambient (i.e. non-occupational) respirable crystalline silica concentrations applicable to community exposure. For protection of human health from emissions of air from mining and extractive industries, the EPA Victoria has adopted an annual average criterion of 3 μg/m3 for crystalline silica present in the PM2.5 fraction. Measured PM2.5 crystalline silica concentrations at the Oxenford monitoring site were compared against the EPA Victoria annual assessment criterion to assess the potential for health impacts on the community surrounding the Oxenford quarry operations.
Where can I access the guidelines used in the assessment of the results?
Each of the monitored pollutant levels were compared against recognised air quality criteria (listed in Table 1). Details on how the criteria were selected are available in the full report.
| Pollutant | Source of Criteria |
|---|---|
| PM2.5 | Queensland Environmental Protection (Air) Policy 2019 Environmental Protection Act 1994 |
|
Crystalline silica (in PM2.5 fraction) | Protocol for Environmental Management: Mining and extractive industries Environment Protection Authority Victoria |
| Deposited dust | Application requirements for activities with impacts to air Air Impacts Guideline - Environmental Protection Act 1994 |
|
Asbestos * occupational exposure standard (not ambient) | Health Monitoring – Guide for asbestos Safe Work Australia |
Did you see the same spikes in measured respirable crystalline silica at other monitoring stations in South East Queensland as you did at the Oxenford monitoring site?
Referring to Figure 6 on page 12 of the report.
Crystalline silica is not routinely monitored at DES air quality monitoring stations in South East Queensland (SEQ). Therefore, DES is unable to confirm the presence of elevated crystalline silica levels at other SEQ monitoring sites during the two region-wide windblown dust events in August 2020. However, there was a consistent pattern of high particle levels recorded at all DES air monitoring network sites in SEQ on 20 August 2020 and 22 August 2020.
While crystalline silica levels were elevated in samples collected at Oxenford in the 7-day periods commencing 15 August 2020 and 22 August 2020 compared to other sampling periods, it is noteworthy that these 7-day average PM2.5 crystalline silica concentrations were still less than 10 per cent of the annual average guideline value.
Did JGI Quarry activities impact on the monitoring data?
The available monitoring data did not indicate any significant contribution from JGI Quarry operations to particle levels at the monitoring location and therefore JGI Quarry impacts were not evaluated in detail.
The magnitude and duration of PM2.5 and PM10 concentrations measured at the monitoring site during the investigation period (April to September 2020), regardless of the source, were not cause for concern regarding human health when compared against the relevant health guideline.