CSIRO Study Shows Declining PFOS but Persistent Heavy Metals in SA Dolphins

Overview of South Australian Marine Contaminant Study

A collaborative scientific study published on 12 March 2025 in the peer-reviewed journal Archives of Environmental Contamination and Toxicology, Volume 90, article number 15, has provided critical insights into the long-term trends of chemical contamination in South Australian marine environments. Co-authored by researchers Rebecca Souter, Damian Lettoof, Catherine Kemper, Lucy Woolford, Anne-Lise Chaber, Luciana Möller, Sam Gaylard, and Ikuko, the study analysed the bioaccumulation of per- and polyfluoroalkyl substances, known as PFAS, alongside heavy metals and metalloids in Indo-Pacific bottlenose dolphins (Tursiops aduncus) and common dolphins (Delphinus delphis). By evaluating tissue samples collected over three decades from the Adelaide Dolphin Sanctuary and the adjacent Port River Estuary, the research provides a rare, long-term dataset detailing how historical pollution and modern regulatory interventions translate into actual biological exposures in marine apex predators.

For Australian environmental consultants, property developers, infrastructure authorities, and local councils, these findings are highly relevant. Dolphins are widely recognised as key bioindicators of estuarine and coastal health because they occupy the top of the marine food web. Contaminants that enter coastal waters from industrial discharges, stormwater runoff, and groundwater migration accumulate in fish and marine invertebrates before reaching elevated concentrations in dolphin tissues through biomagnification. This study demonstrates that while national and state-level policy interventions have successfully driven down concentrations of legacy organic pollutants, historical heavy metal pollution remains a persistent, unmitigated threat to marine ecosystems. Consequently, site assessments and environmental audits in urban catchments must adapt to account for this complex, ongoing background contamination.

The transition from assessing individual chemical compliance to evaluating cumulative ecological risks is a key trend highlighted by this research. Regulators, including the South Australian Environment Protection Authority, are increasingly shifting their focus from isolated, site-specific soil or groundwater guidelines to broader aquatic ecological health. When urban developments, industrial operations, or infrastructure projects interact with sensitive coastal catchments, developers and councils must ensure that their environmental site assessments address the potential for cumulative toxicological impacts. Managing a single contaminant of concern in isolation is no longer sufficient if receiving marine environments are already burdened with multiple persistent stressors.

Key Findings: PFOS Declines and Heavy Metal Persistence

The technical methodology of the study involved screening hepatic (liver) tissue from dolphins retrieved from South Australian waters across two distinct temporal periods. The first period spanned from 1993 to 2015, capturing historical baseline exposures, while the second period covered 2021 to 2023, capturing modern environmental quality. In total, the researchers screened the tissue samples for 29 distinct PFAS compounds and 18 different metals and metalloids, providing a highly comprehensive analytical suite. This methodology allowed the authors to track how the chemical footprint of these apex predators has shifted following major national and international regulatory bans on persistent organic pollutants.

The analytical results identified 21 different PFAS compounds in the hepatic tissues of the analysed dolphins. Perfluorooctane sulfonate, commonly known as PFOS, dominated the organic contaminant profile, representing approximately 80 per cent of the total PFAS body burden. Crucially, the data revealed a statistically significant downward trend in total PFAS and PFOS concentrations in the 2021 to 2023 sampling cohort compared to the historical 1993 to 2015 baseline. This declining trend directly correlates with the voluntary phase-out of PFOS and perfluorooctanoic acid, known as PFOA, imports by major international manufacturers starting in 2002, as well as the progressive implementation of strict state-level bans on fluorinated firefighting foams across Australia over the last two decades.

While the reduction in PFAS concentrations highlights a major policy success, the legacy heavy metal data paints a far more concerning picture for environmental managers. The study recorded extreme concentrations of mercury in the liver tissues of the dolphins, with some individuals exhibiting levels up to 2350 mg/kg on a dry weight basis. Unlike the organic fluorine compounds, mercury, lead, and tin showed no corresponding downward trend over the 30-year study window, remaining highly persistent in the marine population. The extreme mercury concentrations are attributed to historical industrial discharges into the Port River Estuary and the wider Adelaide metropolitan coast, where metals remain locked in marine sediments, continually cycling through the local food web.

In addition to legacy contaminants, the research identified the emergence of short-chain PFAS mixtures in the tissues of the younger dolphin cohort. As long-chain compounds like PFOS have been restricted, industrial chemistry has pivoted towards short-chain alternatives. These short-chain compounds are highly water-soluble, exceptionally mobile in groundwater, and notoriously difficult to remediate using standard water treatment technologies. The co-occurrence of these mobile, modern synthetic chemicals alongside massive concentrations of legacy heavy metals like mercury and lead creates a highly complex toxicological profile, introducing additive or synergistic toxic effects that are not yet fully understood by environmental toxicologists.

Implications for Australian Environmental Site Assessments

The findings of this South Australian study carry significant implications for the application of national environmental policy frameworks, particularly the National Environment Protection (Assessment of Site Contamination) Measure and the PFAS National Environmental Management Plan. While the documented decline in PFOS concentrations confirms that regulatory phase-outs are translating into measurable ecological benefits, the persistence of mercury, lead, and tin at extreme levels within the Port River Estuary food web demonstrates that legacy contamination cannot be addressed through source-control measures alone. Sediment remediation, capping strategies, and long-term monitoring of receiving waters must remain central considerations for any infrastructure or redevelopment project located within historically industrialised coastal catchments.

For environmental consultants and property developers operating in South Australia, the study reinforces the need to treat estuarine sediments as a continuing source of bioavailable contamination rather than an inert historical record. Site assessments adjacent to the Port River, Barker Inlet, and comparable urbanised estuaries should consider sediment disturbance risks during dredging, piling, or stormwater outfall works, as remobilisation of buried metals can re-expose the aquatic food web to contaminants that have otherwise stabilised. Local councils and port authorities should also factor these findings into catchment management plans, ensuring that stormwater quality improvement devices and industrial trade waste controls account for both modern short-chain PFAS and legacy metal loads.

More broadly, the research signals a likely tightening of regulatory expectations around cumulative impact assessment. Proponents of coastal developments should anticipate increased scrutiny from the South Australian Environment Protection Authority regarding multi-contaminant exposure pathways, particularly where projects intersect with sensitive marine habitats such as the Adelaide Dolphin Sanctuary. Early engagement with regulators, robust baseline ecological sampling, and the integration of bioindicator data into environmental impact statements will become increasingly important for securing approvals and managing long-term liability under Australia’s evolving contaminated land and marine protection frameworks.

References and related sources

• Primary source: doi.org
• PFAS National Environmental Management Plan (NEMP)
• SA EPA

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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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