Warringah freeway upgrade: air quality monitoring

How to read the charts

The charts are interactive and best viewed in full screen mode. Select the desired season at the top of the page. Select the menu in the top right-hand corner to enter full screen mode. Hover over the graphs to view more information relating to the data, for example the exact date and value of the data point. To exit full screen mode click escape or move to the top of the screen to display and select the X.

For the KOALA/PurpleAir charts, select or deselect the stations displayed along the bottom of the chart to display them individually or together. The KOALA/PurpleAir co-located with the Cammeray Main AQM is displayed initially.

Cammeray Main Monitor

Data from the Cammeray Main AQM for particles (dust) is available from 15 June 2022 and presented through to the end of August 2024. Particles measured in the PM10 µm (micrometer) fraction are displayed below, however, a comprehensive analysis and overview of PM10 and PM2.5 µm fractions comparing KOALA and Cammeray AQM data is available on request by emailing [email protected]. The light-blue area displays the upper and lower readings recorded across the Sydney region and the darker blue line displays the results from the Cammeray Main AQM.

Observed exceedance

On 10 January 2023, a period of highly elevated PM10 concentrations was recorded at Cammeray when the daily average PM10 level (78.9 µg/m3) exceeded the national standard (50 µg/m3).  The daily PM2.5 level on this day was the highest recorded at Cammeray (13.9 µg/m3), though well below the national standard (25 µg/m3). When compared with other AQMs in the Sydney region, and broadly across New South Wales, no other stations recorded an exceedance for daily average PM10 (or daily average PM2.5) on this day.

Hazard reduction burns (HRBs) during 2023 resulted in the PM10 levels reaching the national standard on three occasions, 11 and 14 September and 19 December. On all three occasions, Sydney wide readings were higher across the region than levels recorded at Cammeray. PM2.5 levels during the HRBs on the 11 and 14 September were almost twice the national standard (48 µg/m³ and 47 µg/m³, respectively), slightly above the national standard on 12 September (29 µg/m³), and just at the national standard on 19 December (25.1 µg/m³).

Particulate matter trends at the Cammeray main monitor

Daily PM10 averages at the Cammeray Main AQM followed the Sydney region except for one instance where elevated PM10 particles were recorded. Days when the top three highest daily average PM10 levels were observed at the Cammeray were in summer. The first highest, observed on 10 January 2023, was when elevated PM10 at Cammeray was clearly distinguishable when compared with the Sydney region. The station recorded its highest ratio of PM10/PM2.5 on this day, which means that PM10 comprised a significant portion of coarse particle mass and that PM2.5 or fine particle component was minimal during this event. While similar ratios of PM10/PM2.5 was observed elsewhere in Sydney, an exceedance of PM10 was only recorded at Cammeray on this day. The second and third days with the highest daily averages at Cammeray were on 12 and 13 February 2023.  The observed particle levels on these days were lower at Cammeray when compared with observations elsewhere in the Sydney region.

An upward trend of elevated particles can be seen as the seasons move from cooler to warmer, with the top three recoded levels for PM10 recorded in summer. There was an increase of about 5 µg/m3 by summer, with the mean winter daily average of 9.4 µg/m3, and mean summer daily average of 14.2µg/m3. This trend is likely driven by a combination of factors including meteorology and emission sources. For instance, statistics from the Bureau of Meteorology indicated that rainfall during the winter and spring seasons in 2022 were above the climate average, while rainfall in December 2022 was 42% below the climate average. Also, wind patterns observed at Cammeray indicate ocean influence during the warmer months increases the possibility of sea salt adding to PM10 levels.

Note, the Cammeray AQM PM10 data was invalidated due to an instrument fault for the period 15 September 2023 – 2 November 2023. No PM10 exceedances of the national standard were recorded across the Sydney region over this period. There were no instances where PM10 levels recoded at the Cammeray AQM exceeded the Sydney regional levels over 2023.

Portable monitors – KOALAs/PurpleAirs

The KOALA and PurpleAir AQMs are indicative instruments that do not have the same accuracy, precision or stability as more sophisticated compliance instruments (such as the Cammeray Main AQM). Most optical methods, like the KOALAs and PurpleAirs, do not detect larger particles well and are best suited for PM2.5, and even then, can be affected by high humidity. While this means the PM2.5 data from these AQMs cannot be directly compared to National Standards (Ambient Air Quality NEPM), it is valuable for indicating any local air pollution, assessing trends within and between locations, and as tools for community education and awareness around the management of air quality.

The charts present seasonal time series graphs, separated by season, that display daily PM2.5 averages for the transect of 10 KOALAs/PurpleAirs deployed for the Warringah Freeway Upgrade Project. The graphs show events of elevated PM2.5 levels, and where daily averages greater than 25 µg/m³ were recorded at one or more sites, these cases have been classified into two types: 

• Local events​ are isolated to at least one location in the KOALA/PurpleAir network, but not the entire network of 10 AQMs.  
• Regional events​ are where more than one station peak simultaneously across the entire network.  

The KOALA/PurpleAir AQMs’ responses to different aerosol emission sources have not been investigated for the purposes of this project. Generally, the KOALAs/PurpleAirs will reflect increased levels of particulates due to woodsmoke, bushfires or hazard reduction burning, or when meteorological conditions such as strong inversions trap pollution and humidity under a warm layer of air. Events flagged as local or regional events may be attributed to any of the above causes. The KOALAs/PurpleAirs are less responsive to larger particles such as marine aerosols and dust. As such, data from the KOALAs/PurpleAirs cannot be attributed to dust events or sea salt without extensive investigation using complementary monitoring techniques (such as the Cammeray Main AQM).

• Air quality standards following the National Environment Protection (Ambient Air Quality) Measure (NEPM) are based on 24-hour averages, so data reported in 30- and 60 -minute intervals may go above guidelines while still adhering to the NEPM standards. Short-term spikes in particulates can occur due to sudden gusts of wind which carry dust or sea salt, dust storms and bushfires or hazard reduction burning in the Sydney basin. 
• You can follow the activity guide produced by the Department of Planning and Environment for advice on how to change your daily activities based on air quality indicators.
• See information on protecting yourself from air pollution on the NSW Health site,