How will the WHO’s Global Air Quality Guidelines affect Australia?

At its meeting on 15 April 2021, the National Environment Protection Council (NEPC) agreed to vary the National Environment Protection (Ambient Air Quality) Measure (AAQ NEPM), incorporating a number of changes to standards for pollutants (click here to read our discussion of the AAQ NEPM Review).  Standards were revised for ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2).  NEPC’s media release highlighted that the revised NO2 standards are tighter than the World Health Organization (WHO) guidelines and reflective of the most recent health evidence emerging about the health impacts of NO2.


Ministers also agreed to commence a further review of the O3, NO2 and SO2 standards in 2025, noting that reviews of the PM2.5 and annual PM10 particle standards are also planned, stating this will provide an opportunity to review the standards in line with the available evidence at that time, including any updates to the World Health Organization guidelines.


WHO Guidelines Update

Subsequently, in September 2021, the World Health Organization published new guidelines for O3, NO2, SO2, PM2.5, PM10 and CO.  These new guidelines are summarised and compared to the standards in the AAQ NEPM in the table below.


Pollutant Averaging Period New WHO Guideline AAQ NEPM Standard
PM2.5 (µg/m3) Annual 5 8
24-hour 15 a 25 b
PM10 (µg/m3) Annual 15 25
24-hour 45 a 50 b
O3 (µg/m3) Peak Season 60
8-hour 100 a 139.1 b
NO2 (µg/m3) Annual 10 31
24-hour 25 a
1-hour 200 c 164 b
SO2 (µg/m3) 24-hour 40 a 57 b
CO (mg/m3) 24-hour 4 a
8-hour 10 c 11.25 b
Table Notes:

a 99th percentile (i.e. 3–4 exceedance days per year).

b Not to be exceeded limit.

c Certain guidelines for NO2, SO2 and CO (short averaging times) were not re-evaluated and remain valid.


Where directly comparable, the new WHO guidelines are considerably lower than the AAQ NEPM standards, especially for annual NO2, PM2.5 and PM10.  It is important to note that the shorter-term WHO guidelines (i.e., those with 24-hour and 8-hour averaging periods) are 99th percentile limits, whereas the AAQ NEPM standards are 100th percentile limits allowing no exceedances.


What does it mean to your operations?

WHO notes that its guidelines are neither standards nor legally binding criteria.  WHO provides the guidelines to offer guidance in reducing the health impacts of air pollution based on expert evaluation of current scientific evidence.  Governments use the guidelines and supporting materials in different ways depending on a range of factors.  WHO recommends that governments should consider their unique local conditions before adopting the WHO guidelines.


In Australia, we have tended to have regard to the WHO guidelines when making decisions about air quality standards.  However, we also consider input from a range of stakeholders, state and territory governments and a range of other factors and data sources.  This has ultimately resulted in the magnitude and form of the AAQ NEPM standards being different from the WHO guidelines.


However, we do expect the tighter WHO guidelines will put downward pressure on future AAQ NEPM standards when they are reviewed in 2025.


Operators of facilities that emit these pollutants to air would be wise to consider how any future changes to the standards might affect the viability of their operations, especially facilities with significant combustion emissions.  Pragmatic future-proofing might involve a review of the potential air quality impacts of relevant facilities to establish the extent of any issues that might arise under the new AAQ NEPM standards or WHO guidelines.  For some facilities that review will show that operational changes or enhanced abatement may be required to ensure that the new AAQ NEPM standards can be met.


The landscape for tolerance of air quality impacts in Australia appears to be changing, and doing so quickly, and industrial operators would be prudent to keep a close eye on this to avoid unexpected (and avoidable) surprises in future license reviews or other interactions with environmental authorities.


How can Katestone help you?

Katestone’s fit-for-purpose studies have supported numerous proposed industrial, infrastructure and agricultural developments. Katestone has assisted its clients to reduce emissions whilst improving operations and mitigating operational risks. We assist our clients with the management of air quality, odour, greenhouse gas emissions and climate change associated with planned or existing operations.


Our clients benefit from studies that quantify the potential impacts on air quality across the lifetime of a project. We have also contributed significantly to the development of air quality management policies and legislation throughout Australia by conducting targeted research and analysis.


References 2021. [online] Available at: <> [Accessed 5 August 2021]. 2021. [online] Available at: <> [Accessed 5 August 2021]. 2021. [online] Available at: <> [Accessed 5 August 2021].

World Health Organization. 2021 [online]‎. WHO global air quality guidelines: particulate matter (‎PM2.5 and PM10)‎, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. World Health Organization. Available at: <>. License: CC BY-NC-SA 3.0 IGO [Accessed 2 December 2021].


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