In 2012, CRC CARE identified and prioritised contaminants of emerging concern (CECs) for contaminated site assessment, management and remediation. The priority contaminants are the perfluorinated chemicals perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), methyl tertiary-butyl ether (MTBE), benzo[a]pyrene (B[a]P), weathered hydrocarbons, and polybrominated diphenyl ethers.

CRC CARE completed literature reviews for these CECs in 2013–14 (see CRC CARE Technical Reports 24, 29 and 32). Based on the findings, CRC CARE started developing guidance for PFOS/PFOA, MTBE and B[a]P in consultation with industry, regulators and experts in 2015.

CRC CARE has developed risk-based guidance for the assessment, management and remediation of site contamination that is contaminant specific. Human health screening levels (HSLs) and ecological screening levels (ESLs) have been generated for the contaminants.

The guidance is consistent with the National Environment Protection (Assessment of Site Contamination) Measure (ASC NEPM), which focuses on the assessment of contamination. The guidance is also intended to be implemented in a manner consistent with the National Water Quality Management Strategy (eg ANZECC & ARMCANZ,¹ NHMRC,² NHMRC & NRMMC³).

The guidance is also intended to complement the National Remediation Framework (NRF), which harmonises guidance and best practice for remediation and management of contaminated sites across Australia.

Contaminants of emerging concern

Methyl tertiary-butyl ether

MTBE is not used as an additive for petrol in Australia, although it may be present at levels up to 1% in imported fuels. There are sites at which MTBE contamination occurred before the introduction of the Fuel Quality Standards Act 2000 and the Fuel Quality Standards Regulations 2001, and so contamination of groundwater at legacy sites is an important consideration.

When it enters the environment through soils, MTBE preferentially enters groundwater or surface waters because of its high water solubility and low affinity to soils. Consequently, limited international guidance is available for MTBE in soil and soil vapour. If MTBE is present in surface waters, it will readily volatilise. For aquatic species, MTBE has relatively low acute and chronic toxicity, with marine species generally showing a greater sensitivity.

MTBE has a low odour threshold, which makes drinking water unpalatable at MTBE concentrations well below those that would affect human health. A screening level based on aesthetics can therefore be used to assess groundwater that is, or may be used for, potable and nonpotable purposes.

The CRC CARE guidance provides a risk-based approach for assessing potentially contaminated sites, and for managing and/or remediating groundwater contamination. Published in CRC CARE Technical Report 36, Guidance on the assessment, remediation and management of methyl tertiary-butyl ether, it comprises:

• an odour-based screening level in water
• ecological screening levels that have been derived using a methodology based on ANZECC & ARMCANZ¹ and ASC NEPM
• contaminant-specific considerations for site investigations, including developing the conceptual site model (CSM).

Benzo[a]pyrene

B[a]P is a ubiquitous environmental contaminant, particularly in urban areas. It tends to be of greater concern in soil and sediment matrices than in groundwater or surface water because of its very low solubility. B[a]P is persistent in the environment and does not readily degrade, making B[a]P-contaminated soils and sediments difficult and costly to remediate.

The NEPM provides health investigation levels (HILs) and ESL values for B[a]P. There is some concern that these values may be overly conservative. This is because the bioavailability of B[a]P (and hence toxicity to human and ecological receptors) can be reduced, given the tendency of B[a]P to sorb to organic sorb fractions, the age of contamination, soil properties and other factors. Using bioavailability or bioaccessibility measures to derive site-specific criteria for organic contaminants is not well established, and this guidance provides information on the current status to assist decision making.

Further, the NEPM provides ESLs for B[a]P based on the (now outdated) Canadian soil quality guidelines. The CRC CARE guidance reviews several newly available studies and applies Australian methodology (ie ANZECC & ARMCANZ¹) to generate ESLs that are more reliable.

To understand the implications of HIL and ESL exceedances for some contaminated sites, and the risks posed by B[a]P contamination to human and ecological receptors, it is important to develop a site-specific CSM. The CRC CARE guidance – see Technical Report 38, Guidance on the risk-based remediation and management of benzo[a]pyrene – details the potential sources, potential receptors and exposure pathways by which receptors may contact B[a]P.

For situations where B[a]P-contaminated media needs remediation, guidance on developing a remediation strategy is provided. Typical response actions will include no action, re-use, in situ or ex situ treatment, containment or institutional controls, or excavation (soil) / extraction (groundwater) and offsite disposal. Because of the recalcitrance of B[a]P in soil material, treatment options can be limited, making it difficult to reach the low concentrations indicated by the HILs and ESLs. In these circumstances, consideration of the bioavailability of B[a]P becomes important, because this may mean that higher soil concentrations are acceptable.

Perfluorooctanesulfonate and perfluorooctanoic acid

PFOS and PFOA belong to a large group of compounds called per-and poly-fluoroalkyl substances (PFAS). All PFAS are highly persistent, bioaccumulative, and potentially toxic to humans and the environment. They have been found at concentrations of potential concern at a number of sites, particularly where firefighting foams have been used. PFOS is listed as a persistent organic pollutant under the Stockholm Convention.

Industry and public awareness of PFAS both in Australia and internationally is growing rapidly. PFOS contamination is reported frequently in the media, with concerns being raised regarding the possible health risks to humans who may have been exposed.

Information surrounding the occurrence, fate and toxicity of PFAS in the Australian context is limited and incomplete, apart from some hotspots. Because of the persistence and difficulty of treating PFAS contamination, there is also considerable uncertainty about how such contamination can be managed and remediated.

In 2014, when this project started, there were no recognised criteria in Australia for protecting human health and ecological systems, making it difficult to determine the risk posed by contamination. CRC CARE was advised by its Project Advisory Group to invite relevant stakeholders to act as consultants to the project. A large consultation forum was developed comprising regulators, industry and experts, which helped to develop the draft guidelines for PFOS and PFOA in 2015.

The purpose of the CRC CARE guidance is to provide a consistent, risk-based approach to the assessment, management and remediation of PFAS contamination in Australia, specifically:

• HSLs and ESLs for PFOS and PFOA contamination in soil, groundwater, surface water and sediment
• a framework and discussion about applying these screening values
• a risk-based approach to managing and remediating PFOS and PFOA contamination.

In June 2016, enHealth, the peak environmental health body in Australia, selected the European Food Safety Authority health reference values for PFOS (and perfluorohexane sulfonate [PFHxS] combined) and PFOA as interim measures (see the enHealth statement [PDF 114KB]). A review of the enHealth position concluded that this was appropriate, given that Food Standards Australia New Zealand (FSANZ) was to conduct a further review.

In April 2017, FSANZ released recommended total daily intakes for PFOS and PFOA, which now take precedence. FSANZ published additional trigger points that should be used when comparing measurements in homegrown produce and food consumption (eg fruits, vegetables, fish, crustaceans, meat, honey, milk, poultry, eggs). In March 2017, before the FSANZ publication, CRC CARE published its interim guidance, with caveats to indicate that the guidance would be revised following the pending FSANZ work.

The CRC CARE guidance has been updated and will be published following a review by the Project Advisory Group, which includes representatives from regulatory agencies and industry.

What is in the PFAS guidance?

The revised guidance focuses on PFOS and PFOA, which are the most well understood PFAS, and are those most commonly encountered in the environment and in wildlife. Limited information is available for other PFAS compounds. Work on PFOS by both enHealth and FSANZ also considers PFHxS; and therefore, the CRC CARE guidance on HSLs states that PFOS and PFHxS exposures should be combined.

In developing ESLs, the guidance uses Australian methodologies as per ASC NEPM 2013 and the National Water Quality Management Strategy.¹ After the project commenced, the Australian Government Department of the Environment and Energy (DoEE) joined the CRC CARE consultation forum as observers. DoEE started to develop freshwater guideline values for PFOS and PFOA in 2015. CRC CARE continued to develop soil and marine water guideline values, and to provide further guidance on the application of all ESLs. DoEE issued some interim guidance, drawing on the draft CRC CARE guidance document.

The CRC CARE document is a comprehensive risk-based guidance for the assessment, management and remediation of PFOS- and PFOA-contaminated sites. The guidance comprises 5 parts.

Part 1: Background

• background to the guidance document
• an overview of PFAS, in particular PFOS and PFOA
• physicochemical properties
• overview of human health and ecological toxicity
• prevalence and behaviour of PFOS and PFOA in the environment
• overview of international guidance and criteria available (at the time of publication)
• current situation in Australia.

Part 2: Human health screening levels

• PFOS and PFOA toxicity in humans
• toxicokinetics of PFOS and PFOA in humans
• human health guideline values
• derivation of human health guideline values
• application of the human health guideline values.

Part 3: Ecological screening levels

• ecological receptors and ecotoxicity of PFOS and PFOA
• factors influencing toxicity, such as bioaccumulation and bioaccessibility
• guideline values for terrestrial and marine aquatic ecosystems
• derivation of ecological guideline values
• considerations in the application of guideline values.

Part 4: Application of human health and ecological screening values

• standalone summary of the human health and ecological guideline values and application information
• essential information to apply the human health and ecological guideline values (users can then refer to parts 2 and 3 for the technical detail and derivation process, if required).

Part 5: Risk-based management and remediation

• framework for the risk-based management and remediation of PFOS- and PFOA-contaminated soil, sediment and water, linking back to the human health and ecological guideline values
• development of a site-specific CSM for PFOS- and PFOA-contaminated sites
• aspects that should be considered in the management and remediation of PFOS- and PFOA-contaminated media.
• available technologies to treat PFOS- and PFOA-contaminated soil, sediment and groundwater, and applications of technologies.

Status of guidance development

The guidance for MTBE, B[a]P and flux has been published, and the guidance documentation for PFOS/PFOA is near completion and expected to be endorsed later in 2017. Following endorsement, all guidance can be downloaded at the CRC CARE website.

Opportunities and challenges

The development of guidance for CECs presented several opportunities and challenges. The development of guidance provides invaluable opportunities to integrate science and policy, taking into account the interests of stakeholders in government, industry and academia (and beyond). It is also a positive step towards national harmonisation of approaches, particularly for PFAS, about which there has been much contention in the media in the past 24 months.

The key challenge was the need to balance scientific and practical perspectives, given that knowledge about adverse effects on human health and the environment is still evolving (see Naidu et al^4,5). The guidance documents provide a collective view of the available science and application of Australian approaches on the development of human health and ecologically based criteria. The guidance emphasises that exceedance of HSLs and ESLs does not necessarily imply that the contamination poses an unacceptable risk, and that the HSLs and ESLs should not be used as remediation targets, since this could result in unnecessary remediation.

Given that the guidance is in the final stage of development, it is important that it is adopted by Australian jurisdictions. It is expected that the engagement of jurisdictions in the development of the guidance will pave the way for consistency in contaminated site practices at the national level.

References

1. Australian and New Zealand Environment and Conservation Council, Agriculture and Resource Management Council of Australia and New Zealand. National water quality management strategy, Australian and New Zealand guidelines for fresh and marine water quality, ANZECC & ARMCANZ, Canberra, 2000.
2. National Health and Medical Research Council. National water quality management strategy: guidelines for managing risk in recreational water, NHMRC, Canberra, 2008.
3. National Health and Medical Research Council, National Resource Management Ministerial Council. National water quality management strategy. Australian drinking water guidelines, NHMRC & NRMMC, Canberra, 2011.
4. Naidu R, Jit J, Kennedy B, Espana V. Emerging contaminant uncertainties and policy: the chicken or the egg conundrum. Chemosphere 2016;154:385–390.
5. Naidu R, Espana V, Liu Y, Jit J. Emerging contaminants in the environment: risk-based analysis for better measurement. Chemosphere 2016;154:350–357.