Revised National Environment Protection Measures standards for gases.

On 18 May 2021 the National Environment Protection (Ambient Air Quality) Measure (NEPM) was amended to update the ambient air quality pollutant concentration standards for nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O3).

The NEPM amendment accounts for the latest scientific advice about the health impacts of these pollutants and includes the following changes (Refer to Table: NEPM standards in 2021):

  • 1-hour and annual NO2 standards as well as the 1-hour and daily SO2 standards strengthened.
  • 1-hour and 4-hour average O3 standards and annual average SO2 standard removed.
  • 8-hour average O3 standard established. The exceptional events rule that applies to the particle standards will also now apply to O3 given the linkages between elevated O3 levels and fire events. The rule will exclude O3 exceedance days determined as being directly associated with an exceptional event when assessing compliance with the 8-hour standard.
  • single day exceedances allowed for all gases, including carbon monoxide, removed.

No changes were made to the standards for PM10 or PM2.5 in this update to the NEPM. For more information on the updates to the NEPM, refer to the National Environment Protection Council (NEPC) website.

NEPM standards in 2021

Pollutant Averaging period Old NEPM >New NEPM Change<
Concentration (pphm)
Photochemical oxidants (as ozone) (O3) 1-hour 10 - Removed
4-hour 8 - Removed
8-hour - 6.5 a Established e
Nitrogen Dioxide (NO2) 1-hour 12 8 Reduced e
Annual 3 1.5 Reduced
Sulfur dioxide (SO2) 1-hour 20 10 b Reduced e
1-day 8 2 Reduced e
Annual 2 - Removed
Concentration (ppm)
Carbon monoxide (CO) 8-hour 9 9 No change e
Concentration (µg/m3)
Particulate matter ≤10μm in diameter (PM10) 1-day 50 50 No change e
Annual 25 25 No change
Particulate matter ≤2.5μm in diameter (PM2.5) 1-day 25 25 c No change e
Annual 8 8 d No change

– Not applicable

  1. The exceptional event rule now allows 8-hour ozone exceedances to be classified as an exceptional event, which are those events directly influenced by smoke from bushfires or hazard reduction burns. This data should still be reported, and the exceptional events described. However, when assessing compliance against the annual goals, these exceedances shall be excluded.
  2. The 1-hour average SO2 standard will further reduce to 7.5 pphm from 2025.
  3. The goal for daily average PM2.5 will be 20 µg/m3 from 2025. The goal will provide a framework for continuous improvement and facilitate a review of the PM2.5 standard.
  4. The goal for annual average PM2.5 will be 7 µg/m3 from 2025. The goal will provide a framework for continuous improvement and facilitate a review of the PM2.5 standard.
  5. No allowable exceedance day for this standard.

Effect of new standards

The new NEPM standards came into force part-way through the year during 2021. For the NSW annual air quality statement 2021, it has been assumed that the new and more stringent standards would apply for the whole year. But for the purpose of assessing the impacts of the changes, the relevant elevated pollutant levels for 2021 are compared against both new and old standards below.

There were 5 days in 2021 with ozone levels recorded over the new 8-hour ozone standard at one or more stations in New South Wales. There would have been only one exceedance day when compared to the older 1-hour standard and three exceedance days when compared to the older 4-hour standard. The extent of the exceedances would also have generally been lesser with the older standards, in that fewer stations would have been impacted.

Number of stations which recorded ozone levels over the old and new NEPM standards by calendar day during 2021

Date Number of monitors exceeding standard Exceptional event?*
1-hour average 4-hour average 8-hour average
23/01/2021 0 3 4 No
24/01/2021 0 0 6 No
25/01/2021 1 5 8 No
09/10/2021 0 0 1 Yes
21/12/2021 0 2 2 No
Total days above standard 1 3 5  

Note: *The exceptional events rule only applies to the new NEPM ozone standard, which is applied to the 8-hour average. An exceedance day determined to be impacted by bushfires or planned burns is deemed exceptional.

There were no recorded values over the new 1-hour or annual average NO2 standards in 2021. This is also true for the older standards as they are less stringent.

There was a single 1-hour average level of 12.3 pphm recorded over the new 1-hour SO2 NEPM standard of 10 pphm, at Muswellbrook on 4 February 2021. If the previous 1-hour standard of 20 pphm were applied to this recorded level, there would have been no exceedance of the standard.

All other 1-hour and 24-hour SO2 values recorded in New South Wales in 2021 would have remained below both the old and new NEPM standards in 2021.