Updated ANZG Default Guideline Values for PFOS Introduce Bioaccumulation Assessment Requirement

Overview

Water Quality Australia has published the final ANZG Toxicant Default Guideline Values for perfluorooctane sulfonate (PFOS), delivering a significant change to how freshwater ecological risk assessments are conducted across Australia. The updated 99 per cent species protection value for PFOS in freshwater has increased from 0.00023 micrograms per litre to 0.013 micrograms per litre — a rise of nearly two orders of magnitude from the previous interim guidance.

While this relaxation reduces the number of sites likely to exceed the freshwater ecological screening threshold, the update introduces a new requirement that has practical implications for contaminated site practitioners. The guideline now mandates that site-specific assessments account for bioaccumulation pathways when PFOS is detected in surface water or groundwater that discharges to ecological receptors.

Key details

The revised default guideline value of 0.013 micrograms per litre for 99 per cent species protection replaces the previous interim value that had been applied since the original ANZG 2018 framework was published. The new value is based on an expanded toxicological dataset that includes additional chronic toxicity studies across a broader range of aquatic species, providing a more robust statistical basis for the species sensitivity distribution.

The previous interim value of 0.00023 micrograms per litre was widely recognised as overly conservative, frequently triggering exceedances at sites where ecological risk was considered low. Many contaminated site assessments identified PFOS concentrations above this threshold in surface water and groundwater, leading to requirements for detailed ecological risk assessments that may not have been warranted by the actual site conditions.

However, the updated guideline introduces a bioaccumulation assessment requirement. Where PFOS is detected above the default guideline value, assessors must now evaluate secondary poisoning pathways — the potential for PFOS to bioaccumulate through aquatic food chains and affect higher-order predators such as fish-eating birds, mammals, and reptiles. This shifts the assessment from a simple water quality comparison to a more complex ecological risk evaluation.

Australian context

The PFAS National Environmental Management Plan (NEMP) Version 3.0 references the ANZG default guideline values as the primary screening criteria for ecological risk assessment at PFAS-contaminated sites. The updated PFOS value will directly affect how practitioners apply the tiered assessment framework prescribed under the NEMP.

Under the previous interim value, many sites with low-level PFOS detections in surface water or shallow groundwater discharging to waterways were flagged for further ecological investigation. The revised value will reduce the number of sites requiring detailed Tier 2 or Tier 3 ecological risk assessments for PFOS alone, potentially streamlining the assessment process for some contaminated land projects.

However, the bioaccumulation pathway requirement adds a new layer of complexity. Practitioners conducting ecological risk assessments at sites near waterways, wetlands, or other sensitive ecological receptors must now explicitly address whether PFOS concentrations could lead to harmful accumulation in aquatic biota. This requires an understanding of site-specific food chain dynamics and may necessitate tissue sampling of aquatic organisms to quantify bioaccumulation factors.

State environmental regulators in New South Wales, Victoria, Queensland, and South Australia have historically applied the ANZG values as default screening criteria in their contaminated land frameworks. The updated value should be adopted consistently across jurisdictions, though practitioners should verify the implementation timeline with each relevant state EPA.

Practical implications

Environmental consultants should update their screening criteria tables to reflect the revised PFOS freshwater guideline value immediately. Reports and risk assessments that reference the previous interim value of 0.00023 micrograms per litre will need to be reviewed if they are still active or subject to regulatory audit.

For sites where PFOS concentrations in surface water previously exceeded the interim value but fall below the new 0.013 micrograms per litre threshold, practitioners should assess whether previously triggered ecological investigations can be revised or closed out. This may reduce ongoing monitoring and assessment costs for site owners.

Conversely, the bioaccumulation pathway requirement means that sites with PFOS detections above the new guideline value will face a more demanding assessment process. Consultants should ensure their ecological risk assessment methodologies include bioaccumulation modelling or tissue sampling capabilities, as regulators will expect these pathways to be explicitly addressed.

Laboratories providing PFAS analytical services should confirm that their limits of reporting for PFOS in water are sufficiently low to enable meaningful comparison against the new guideline value. A limit of reporting at or below 0.004 micrograms per litre is recommended to provide adequate resolution around the 0.013 micrograms per litre threshold.

References and related sources

• Water Quality Australia — ANZG Toxicant Default Guideline Values
• Australian Government DCCEEW — PFAS National Environmental Management Plan

How iEnvi can help

iEnvi provides specialist ecological risk assessment and PFAS site characterisation services. Our team assists property developers, industrial operators, and government agencies with applying updated screening criteria to contaminated land assessments.

• Contaminated land assessment
• Remediation and risk management
• Ecology and biodiversity

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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.

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