PFAS proficiency testing: better measurement, better management

PFAS proficiency testing: better measurement, better management

PFAS (per- and polyfluoroalkyl substances) are toxic synthetic chemicals known to have potential health and environmental impacts. PFAS are highly resistant to degradation and are very mobile. They are also ubiquitous because of their use in common industrial products such as firefighting foams and nonstick coatings.

In Australia, PFAS have been the subject of recent considerable interest to communities near sites known or believed to be affected by PFAS contamination. These complex contaminants are challenging to measure in the environment and significant discrepancies in laboratory results have been reported. An assumption of measurement reliability and comparability is inherent in the environmental management framework. Guidance, regulation and site assessment can only be effective if the associated data are reliable and comparable. Confidence in the reliability and comparability of the data is vital to deciding the best approach to managing each case.

Proficiency testing (PT) refers to the ‘evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons’1 and provides an independent assessment of performance for participating laboratories. It is a widely accepted approach for improving comparability between laboratories, and it can offer insights into the reasons for variability in analytical results from a variety of methods or laboratories. This knowledge is also of value to anyone who uses and relies on laboratory analysis data, in particular consultants, regulators, auditors, site managers, toxicologists and researchers.

PFAS proficiency testing in Australia

In 2013, the National Measurement Institute (NMI) identified PFAS PT as a significant gap in Australian analytical methodology for environmental measurement.2 At that time, PT for PFAS was only available through a small number of schemes run occasionally by commercial overseas providers, where local needs might not always align with those of Australia. NMI, with the support of CRC CARE and EPA Victoria, responded to this gap by developing and implementing Australia’s first PFAS PT program.

Significant technical challenges had to be overcome in establishing this new national capability, such as the development of innovative sample preparation methods to ensure homogeneity and stability in challenging matrices, and the investigation of factors affecting analysis results. End-user education through national workshops forms an integral part of the NMI PFAS PT program. The program has generated much interest and support from the Australian environment sector.

The first Australian PFAS PT study3 was conducted in 2015. This study compared data for PFOS (perfluorooctane sulfonate) and PFOA (perfluorooctanoic acid), the 2 best known PFAS, in soil and water samples. NMI conducted a follow-up study in 2016,4 expanding the matrices tested to include biota. A 2017 study will focus on expanding the number of compounds under consideration.

A key decision in the design of every PT program is the level of contamination to target for the samples provided to program participants. The levels chosen need to address contaminant levels commonly encountered in practice, as well as threshold levels recommended in local guidance. Practical considerations such as the number of participating laboratories able to achieve meaningful results at those levels also need to be considered. For example, the 2015 study concentrated on the 2 matrix types of greatest interest, while using a range of samples that would reflect both typical environmental background levels as well as the higher concentration levels that might be found in contaminated sites.

Close up photo of equipment

Equipment used for PFAS analysis

Photo: National Measurement Institute

A strong emphasis on education and dissemination of study findings to end users beyond the laboratory is a key feature of the Australian PFAS PT program. A workshop has been held after each study to communicate the significance of the results, so that end users across the country can share their views in live discussion on the future gaps that should be addressed by NMI’s ongoing PT program.

Findings to date

There has been strong uptake of this initiative by laboratories in Australia and overseas, with 11 laboratories participating in the first study and 24 in the second. The 2016 study included 15 participants from Asia, Europe and North America. Two key indicators of performance, z-scores and En-scores, are related to the difference between an individual laboratory result and the sample value assigned by the study administrator. Some improvement in laboratory performance is apparent between 2015 and 2016, with the percentage of satisfactory z-scores increasing from 79% to 92%. There was little change in the percentage of satisfactory En-scores. The limited data available from 3 international studies suggest that laboratory performance in the Australian studies is at least comparable.

Montage of steps involved in study

The NMI study AQA 17-08 is currently under way

Photo: National Measurement Institute

Workshop discussions indicate that key technical concerns for end users include:

  • the degree and causes of variability between results from different extraction or analysis methods
  • whether the type of calibration standards used by laboratories can affect the result and, if so, by what amount
  • availability of high-quality standards and any consequent effects on laboratory results
  • identifying and addressing the compounds and matrices most likely to be of significance in the future.

These questions have been partly addressed by data from the 2015 and 2016 studies; outstanding issues will continue to be considered in upcoming studies.

Impact of PFAS proficiency testing

The development of an Australian capability for PFAS PT will have a positive impact on the full range of organisations involved in dealing with PFAS contamination. High-quality, transparent proficiency studies provide government policy makers and regulators with the confidence that compliance against environmental guidelines can be assessed and demonstrated. Laboratories have a means for independent comparison of their results against those of their peers; they can use the study results to improve their analysis performance and accuracy. The wider environment sector benefits through an improved understanding of how to use measurement data for their purposes. Auditors and consultants have greater confidence in the recommendations they make based on laboratory data, and site managers are better able to decide the optimal approach for dealing with contamination. Finally, and perhaps most importantly, all of these will ultimately build community trust and confidence in government and industry decisions.


  1. International Organization for Standardization. ISO/IEC 17043:2010Conformity assessment – general requirements for proficiency testing, ISO, Geneva, 2010.
  2. CRC CARE. Analytical methods for priority and emerging contaminants – a literature review, CRC CARE Technical Report 24, CRC CARE, Adelaide, 2013.
  3. National Measurement Institute. PFOS/PFOA in water and soil, proficiency study AQA 15-03, NMI, North Ryde, 2015.
  4. National Measurement Institute. PFOS/PFOA in fish, soil and water, proficiency test report AQA 16-06, NMI, North Ryde, 2016.
Published September 2017 Issue 18