History of air quality reporting

Sydney's air quality has been monitored since the 1960s. Reporting has also evolved over time, moving to Air Quality Categories in 2020.


The devastating 2019-2020 Black Summer bushfires were the catalyst for substantial changes to how we present air quality data and communicate health advice and recommendations. In response to community feedback during the bushfires, we began reporting hourly averages of PM10 and PM2.5 instead of the rolling 24-hour average in February 2020.

Following bushfires, a major review of the Air Quality Index (AQI) concept and air quality health messaging was conducted. The review phase involved various Australian jurisdictions and the Environmental Health Standing Committee (enHealth). It included examining how AQIs are reported internationally with particular focus on particle measurements, as documented in this review report.

In November 2020, the review led to the AQI being replaced with the Air Quality Category (AQC), together with the introduction of a new health activity guide. Like the AQI, the AQC is based on the concentrations of criterion air pollutants as well as visibility. This approach reduced the number of air quality categories from 6 to 5, and changed the cut-off concentrations and thresholds for some pollutants. The new health activity guide provides detailed information on how to protect yourself from air pollution, with messaging that targets at-risk persons.


In June 1998, there were 2 major changes in relation to air quality and how it is reported:

  1. national standards were set for how air quality is measured (using 6 criteria air pollutants)
  2. national reporting process was introduced.

The 6 criteria pollutants measured to assess national standards are ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, particles as PM10 and particles as PM2.5 and lead.

In 2002, the then Environment Protection Authority began reporting on these pollutants to the national body. In 2006, the then OEH stopped monitoring lead as levels became undetectable. Read about the Air Quality Index and how it was calculated.

The old Regional Pollution Index (RPI) was replaced by an Air Quality Index (AQI) in 2008 based on the 5 criteria pollutants (as per national standards) plus visibility (as per a standard set by the then NSW Office of Environment and Heritage) at all sites in the air quality monitoring network. NOTE: All indexes for air quality data collected prior to 2008 were recalculated using the new AQI and are now reported in this format.

In response to community feedback during the 2019–2020 Black Summer bushfires, in February 2020 DPE began reporting hourly averages of PM10 and PM2.5 instead of the rolling 24-hour average. Later in November 2020, the AQI was replaced by the AQC approach.


In 1993, following a major review of monitoring needs, the NSW Government upgraded the monitoring network and extended it to the lower Hunter, Illawarra and western area of Sydney.

As a consequence of the expansion of the network, daily reporting of air quality was also reviewed, resulting in the reporting of a Regional Pollution Index (RPI). The RPI was produced for three regions in Sydney (Eastern Sydney, North Western Sydney and South Western Sydney) three sites in the lower Hunter (Newcastle, Wallsend and Beresfield) and three sites in the Illawarra (Wollongong, Kembla Grange and Albion Park).

Pre 1993

Sydney's air has been monitored for a range of pollutants since the 1960s. By the early 1980s, daily air quality reports were being released, based specifically on concentrations of ozone and fine particles. These Sydney Pollution Index (SPI) reports used a simple linear scale that reported pollution levels as low, medium or high. The SPI measured ozone and fine particles from 6am to 3pm. This reflected an emphasis on visible pollution and focused on daytime visibility as a measure of air quality.

At that time Sydney's population lived mainly east of Parramatta and in the south-western areas of Liverpool/Campbelltown. Monitoring was therefore concentrated in these areas.