December 2024 update to the Australian Drinking Water Guidelines – Questions and Answers

The primary purpose of the December 2024 update to the Guidelines was to action a number of minor amendments and corrections to the Guidelines. Many of the edits focused on consequential amendments to align content in the Guidelines with updated advice on microbial water quality that was published in September 2022. At the time of that update to Chapter 5 and Appendix 3, it was noted that a number of consequential changes would need to be actioned to ensure consistency throughout the rest of the Guidelines. Minor edits were also made to introduce the concept and clarify the purpose of microbial health-based targets and other guideline values provided in the Guidelines. Any new text added as part of this update is based on existing content and/or concepts mentioned elsewhere in the Guidelines.

In addition, a number of edits to correct minor errors and improve clarity and consistency in the Guidelines have been made (for example, editorial edits, typographical errors, formatting errors, consistent terminology or updates to terminology to reflect current practice).

The main amendments actioned in this update of the Guidelines include:

• updating disinfection information sheets to align with the log₁₀ reduction values (LRVs) published for microbial health-based targets in Chapter 5
• updating criteria for pH and turbidity associated with validated disinfectant LRVs and consistent referencing in related information sheets to align with advice in Chapter 5 and Appendix 3
• ensuring consistent guidance on maintaining residual disinfection in the distribution network.

This version also corrects an inconsistency in the microbial water quality guidance that was published in the September 2022 update.  

The issue related to errors in the explanatory text and footnotes in several places in Chapter 5 and Appendix 3 of the Guidelines. The text in these sections describes the process used by NHMRC and the Water Quality Advisory Committee (the Committee) to derive the microbial health-based targets, in particular an LRV treatment target derived for the protozoa Cryptosporidium. This correction did not affect the final LRVs and did not change the recommendations in the Guidelines.

Details of the edits and corrections that have been made to the Guidelines as part of this update are included in Table 1 of the Public Notice at Appendix A of the Administrative Report.

The NHMRC Environmental Health section was responsible for updating the Guidelines, with advice and oversight from the Water Quality Advisory Committee. A Microbial Subgroup was established to work with NHMRC on the consequential amendments. Details on membership of the Subgroup are provided in the Administrative Report for this update.

NHMRC consulted the Environmental Health Standing Committee (enHealth) Water Quality Expert Reference Panel (WQERP) regarding the proposed amendments and corrections before seeking advice from the Council of NHMRC. More details of the development of the consequential edits for this update are provided in the Administrative Report.

Under section 14B of the National Health and Medical Research Act 1992 (NHMRC Act 1992), public consultation can be dispensed with if the Council of NHMRC is satisfied that proposed amendments to Guidelines raise issues that are of minor significance only.

In March 2023 NHMRC advised the Council of NHMRC of the inconsistency in the microbial water quality guidance (refer to Question 2). The proposed corrections were reviewed and supported by the Committee and the jurisdictional experts on WQERP. On 30 March 2023 the Council of NHMRC advised the CEO that the proposed corrections to the Guidelines were of minor significance and that public consultation was not required prior to making the updates.

For the consequential edits, NHMRC worked with the Microbial Subgroup to compile a list of proposed amendments. The scope of this activity was to only include minor consequential edits to align the Guidelines with the 2022 updated guidance on microbial water quality, and other minor edits that improved clarity and consistency of the Guidelines. The full Committee reviewed and confirmed the proposed minor amendments. If any unresolved issues were raised about a proposed amendment, the amendment in question was removed from this update, for consideration in the future.    

The refined list of proposed amendments was considered and reviewed by the NHMRC Legal team as well as the Water Quality Advisory Committee, WQERP and then finally by the Council of NHMRC. All agreed that the amendments as part of this update were of minor significance and do not change technical outcomes (including the final LRVs), the overall health-based target recommendations, underlying health advice or current practice, and serve to clarify the original intent of the guidance on microbial water quality that was published in September 2022.  

On 30 November 2023, the Council of NHMRC advised the NHMRC CEO that as the proposed changes to the Guidelines were of minor significance only, public consultation could be dispensed with in accordance with section 14B of the NHMRC Act 1992, and the Guidelines could be issued as amended.

Under Regulation 9 of the National Health and Medical Research Council Regulation 2016, NHMRC is required to issue a public notice about proposed Guideline amendments. NHMRC published a Public Notice on the NHMRC website on 22 December 2023 (about the proposed consequential amendments) and 28 April 2023 (about the corrections) to the Guidelines. The Public Notices included a brief summary of the proposed amendments and justification of why public consultation was not required. These Public Notices are included at Appendix A and B in the Administrative Report for this update.

Health-based targets provide quantifiable metrics for defining the safety of drinking water. In the Guidelines, health-based targets are based on health outcomes translated into performance targets for microbiological parameters, guideline values for chemical parameters and a reference value for radiological activity. A new figure (Figure 1.3) has been added to Chapter 1 of the Guidelines to show health-based targets for microbial, chemical and radiological parameters that are included in the Guidelines. It supports new text added to Chapter 1 (Section 1.3.2) that introduces the concept of microbial health-based targets and other guideline values and is based on existing content in Chapter 5.

A new subsection in the introductory chapter has been included in this update (Section 1.3.5) to provide a comprehensive summary of the health-based targets provided in the Guidelines. This section is intended to strengthen and clarify guidance and information on radiological water quality that was updated in the Guidelines in January 2022. The new text is based on existing information and has been included in the Introduction (Chapter 1) clarifying that water quality characteristics covers all types of health-based targets (microbiological and chemical as well as radiological).

The updated Guidelines (Version 3.9) are now published and available from Australian Drinking Water Guidelines.

The Guidelines undergo a rolling revision to ensure they represent the latest scientific evidence on good quality drinking water. Proposed updates and reviews are prioritised by NHMRC with advice from the Water Quality Advisory Committee.

The Guidelines have previously only been accessible in a downloadable PDF format. As NHMRC aims to follow and meet the Web Content Accessibility Guidelines (WCAG 2.2 AA), the Guidelines have now been published in a HTML format to ensure web accessibility. This will also allow the Guidelines to be updated more easily.

A PDF version of the Guidelines will continue to be made available for download while more sustainable options for generating PDF versions of the Guidelines are explored.

Feedback on accessibility or issues with the digital version of the Guidelines is welcomed—please send any feedback to water@nhmrc.gov.au.