Overview
On 15 June 2024, Water Quality Australia finalised and published a suite of significant updates and new additions to the toxicant Default Guideline Values (DGVs) under the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZG 2018). These changes replace several outdated values, some dating back to the ANZECC 2000 guidelines, with high-reliability thresholds derived using modern species sensitivity distribution (SSD) modelling via Burrlioz 2.0 software. The affected toxicants include atrazine in both freshwater and marine environments, cobalt in marine water, and a newly introduced DGV for fipronil in marine water.
For Australian environmental practitioners, these updates carry immediate and material consequences. The freshwater 95% species protection level for atrazine has been tightened nearly threefold, dropping from 13 µg/L to 4.5 µg/L. Marine atrazine limits have been tightened more than fourfold, from 13 µg/L to 3.1 µg/L. On the other side of the ledger, marine cobalt guidelines have been substantially relaxed from the ultra-conservative ANZECC 2000 values, a change that will remove a persistent source of false-positive exceedances for coastal infrastructure and port dredging projects. Together, these revisions represent the most consequential update to the ANZG aquatic ecosystem protection framework in several years.
The audience most directly affected includes contaminated land consultants preparing environmental site assessments near agricultural catchments or coastal receiving environments, environmental auditors reviewing surface water and groundwater monitoring data, water authorities managing discharge licences, and developers and legal advisors managing environmental risk on coastal or rural transactions. Understanding exactly what has changed, and why, is essential to avoid incorrect risk characterisation in assessments prepared from this date forward.
Key details of the June 2024 ANZG DGV updates
The revised atrazine freshwater DGVs reflect a material tightening across all species protection levels. The 95% species protection level, which applies to slightly to moderately disturbed ecosystems and is the most commonly used threshold in site assessment practice, has moved from 13 µg/L to 4.5 µg/L. The 99% species protection level, applicable to high-conservation-value or minimally disturbed systems, is now set at 2.1 µg/L. The 90% and 80% protection levels are 7.1 µg/L and 13 µg/L respectively. Notably, the former 95% protection threshold of 13 µg/L now corresponds to the new 80% protection level, which illustrates the magnitude of the regulatory shift for practitioners who have been screening against the previous interim value.
For marine atrazine, the revision is even more pronounced in proportional terms. The previous guideline of 13 µg/L, which was classified as an interim low-reliability value under ANZECC 2000, has been replaced with a high-reliability 95% species protection DGV of 3.1 µg/L. The 99% protection level is 1.2 µg/L, the 90% level is 4.8 µg/L, and the 80% level is 8.3 µg/L. The former marine guideline of 13 µg/L now sits below even the least protective 80% threshold in the new framework, meaning sites that previously appeared compliant against the old marine guideline may exceed all four new protection-level thresholds.
The marine cobalt revisions move in the opposite direction and represent equally significant change. Under ANZECC 2000, the marine cobalt guideline for 99% species protection was an extremely conservative 0.005 µg/L, and the 95% protection value was 1 µg/L. These values were derived from converted acute toxicity data and were widely regarded as generating chronic false-positive exceedances in natural marine environments where background cobalt concentrations routinely exceeded those levels. The new DGVs, grounded in modern chronic toxicity data including studies on bivalves and macroalgae, set the 95% species protection level at 6.1 µg/L and the 99% level at 1.6 µg/L. The 90% and 80% protection levels are now 12 µg/L and 27 µg/L respectively. The relaxation at the 99% level represents a 320-fold increase in the threshold, an extraordinary correction that reflects how poorly the legacy value represented actual biological risk.
The fipronil marine DGV is entirely new to the ANZG framework. No DGV previously existed for fipronil in marine water, leaving practitioners without a formal benchmark for estuarine monitoring and coastal runoff assessments. The new 95% species protection level is 0.01 µg/L. The 99% protection level is 0.003 µg/L, while the 90% and 80% levels are 0.02 µg/L and 0.04 µg/L respectively. These values reflect the well-established high acute and chronic toxicity of fipronil to aquatic arthropods, including crustaceans that are ecologically and commercially significant in Australian estuaries. The extremely low DGV highlights that even trace concentrations of fipronil in coastal receiving environments may constitute a risk to benthic invertebrate communities.
Australian context: how these DGV updates intersect with state and national regulatory frameworks
The ANZG 2018 guidelines do not operate as directly enforceable law in Australian jurisdictions, but they are explicitly adopted or referenced within the regulatory instruments that do. In New South Wales, the Contaminated Land Management Act 1997 and the Protection of the Environment Operations Act 1997 both underpin assessment and licensing frameworks that routinely draw on ANZG guideline values as screening criteria and ecological trigger levels. The NSW Environment Protection Authority’s guidelines for the assessment of sites under the CLM Act direct practitioners to use current ANZG values when characterising risks to aquatic receptors. Updated DGVs published on 15 June 2024 therefore flow into NSW practice immediately for any site assessment, remediation, and management.
References and related sources
- Primary source: www.waterquality.gov.au
- sers.net.au
- ANZG Water Quality Guidelines
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This is an iEnvi Machete news summary. Prepared by iEnvi to summarise the source article for contaminated land, groundwater, remediation, approvals and site risk professionals.
Published: 17 Jun 2026
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