Mark Johnson, Focused Topic Meeting Chair

A SETAC North America Focused Topic Meeting (FTM) on “Estimating Environmental Hazard and Risks from Exposure to Perfluorinated and Polyfluorinated Alkyl Substances (PFAS)” is planned for 12–15 August 2019 at the Durham Convention Center in Durham, North Carolina, USA. Experts in the areas of exposure, chemistry, toxicity and risk assessment of PFAS are all encouraged to attend. Abstract submission is now open. Please visit the meeting PFAS FTM website to check deadlines for abstracts submission, registration and to review the agenda as it develops.

Understanding the risks from environmental releases and exposures to PFAS is an emerging area where many jurisdictions are taking differing approaches to the same questions. The term PFAS is being used to refer to a large class of more than 4,700 substances. PFAS are now found in many compartments of the environment, and there is a pressing need to identify an approach to characterize and measure them routinely, as well as assess their potential effects on human and ecological health. Further, while some are very persistent, many PFAS break down, reform and are highly dynamic in the environment. Additionally, toxic mechanisms of effect have not been well elucidated. Given the large numbers of potential forms, compounds and isomers, controlled laboratory testing of all possible PFAS in animals is impractical. A cohesive roadmap is needed to help develop a testing strategy to use new science to characterize potential effects in humans and the environment, which is why this FTM was organized.

The objective of the FTM is two-fold: 1) to review new and emerging information on PFAS chemical classification and grouping, environmental chemistry, detection technology, fate and transport, exposure potential, human health toxicity and ecological toxicity, and 2) to harness the expertise of eminent scientists in the field to formulate a roadmap to prioritize study of specific PFAS with the goal of developing a risk assessment approach that considers mechanistic (including computational) approaches for extrapolating exposure and effects across different scenarios, species and compounds within environmental pathways for exposure.

The FTM is therefore designed as a scientific exchange concerning approaches for addressing high visibility environmental challenges for a complex topic involving multiple stakeholders. The first two-and-a-half days will consist of expert platform presentations and poster sessions in the five key areas listed below, followed by one-and-a-half days of interactive breakout group deliberations that will address the following charge questions:

  1. Environmental Sources, Chemistry, Fate and Transport
    • What are primary sources or pathways of PFAS in the environment? Can we prioritize?
    • Are current analytical chemistry techniques adequate? What improvements could be made?
    • What chemical–physical properties are most useful in predicting fate and transport for PFASs?
    • How do we better characterize the range of PFAS potentially in the environment?
    • What technologies are available to separate PFAS from abiotic environmental media?
  1. Exposure Assessment
    • What are the key gaps in characterizing current and future exposures to PFAS from environmental contamination, product uses and indirect exposures (e.g., dusts, textiles, paints and coatings, food item transfer)?
    • What efforts might be made to address PFAS as a class or a group of sub-classes for the purpose of ecological and human exposure determination?
    • How should the issue of bioaccumulation of PFAS by human and ecological receptors be addressed in the near and longer term (e.g., empirical associations versus mechanistic models)? What research is needed?
    • How can effects-based monitoring be used in PFAS exposure assessment?
  1. Ecological Toxicity
    • What PFAS substances or sub-classes are most important to characterize adverse effects to aquatic and terrestrial organisms? How could mechanistic computational or in vitro high-throughput data inform this decision?
    • How can exposure potential be evaluated for different classes of vertebrates and invertebrates? What classes of organisms represent conservative models for exposure?
    • What approaches (e.g., quantitative structure–activity relationship [QSAR], read-across, microarray, adverse outcome pathway [AOP]) could be part of an efficient framework for assessing the ecological effects of the large number of PFASs of potential concern?
    • Are current testing methods or model species and predictive tools adequate to evaluate ecological toxicity of PFASs? If not, what are the priorities for method development?
    • What are appropriate approaches for assessing the ecological risks of PFAS mixtures?
    • Could an integrated approach to human health and ecological toxicity assessment be productively applied to the PFAS issue?
    • How can effects-based monitoring be used in PFAS ecotoxicity assessment?
  1. Human Toxicity
    • What PFAS substances or sub-classes are most important (prioritize) to characterize the toxicity to protect human health from environmental exposures?
    • What information currently exists on the mechanisms of PFAS toxicity (both for understanding endpoint-specific and toxicodynamics and toxicokinetics dose metrics) for PFASs and how do these mechanisms relate to compound structure?
    • What is the optimal feasible approach to characterize the toxicity of important PFASs to be used in a risk assessment context?
    • Are current testing models and predictive tools adequate to evaluate human health toxicity of PFASs? If not, what are the priorities for method development?
    • What are appropriate approaches for assessing the human health risks of PFAS mixtures?
    • What are the values and limitations of collecting human biomonitoring reference values for individual PFAS or a group of PFAS?
    • Could an integrated approach to human health and ecological toxicity assessment be productively applied to the PFAS issue?
    • How can effects-based monitoring be used in PFAS human health toxicity assessment?
  1. Risk Assessment and Characterization
    • What type of data could be used to estimate risk from PFAS mixtures in the environment to human and ecological receptors?
    • What criteria are needed to help understand biological half-lives and other key toxicokinetic characteristics among specific species and between genders (are current PBPK models sufficient)?
    • Could an integrated approach to human health and ecological toxicity assessment be productively applied to the PFAS risk assessment?
    • Can a toxic equivalency factor (TEF) approach be used in PFAS environmental (human and ecological) risk assessment? What data would be needed?
    • How can effects-based monitoring be used in PFAS environmental (human and ecological) risk assessment?

Capturing the discussions of trends in each of these charge questions is an essential outcome of this FTM. Therefore, the chairs of the breakout groups aim to prepare a monograph, collating contributions from volunteer participants, that will serve as a critical review in each area of environmental risk assessment and characterization. Hopefully the outcomes of the FTM will serve as a guide to prioritize further research and foster consensus-based risk assessment tools for environmental exposures and releases to PFAS.

Author’s contact information: mark.s.johnson.civ@mail.mil

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