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PFAS — Per- and Polyfluoroalkyl Substances

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PFAS HOME
Navigating This Website
About ITRC
Fact Sheets
1 Introduction
2 Naming Conventions and Use
2 PFAS Chemistry and Naming Conventions, History and Use of PFAS, and Sources of PFAS Releases to the Environment overview
2.1 Environmental Significance
2.2 Chemistry, Terminology, and Acronyms
2.3 Emerging Health and Environmental Concerns
2.4 PFAS Reductions and Alternative PFAS Formulations
2.5 PFAS Uses
2.6 PFAS Releases to the Environment
3 Firefighting Foams
3 Firefighting Foams Overview
3.1 Foam Formulations
3.2 AFFF Characteristics
3.3 Mechanisms for Release to the Environment
3.4 AFFF Fate and Transport
3.5 Forensic Analysis of AFFF
3.6 AFFF Procurement and Inventory
3.7 Foam Systems and Operations
3.8 Emergency Firefighting Operations
3.9 Immediate Investigative and Cleanup Actions
3.10 AFFF Disposal
3.11 Firefighting Foam System Replacement
3.12 Federal, State and International Regulations and Guidance
3.13 Foam Research and Development
4 Physical and Chemical Properties
4 Physical and Chemical Properties Overview
4.1 Challenges and Limitations Related to PFAS Physical and Chemical Properties
4.2 Physical Properties
4.3 Chemical Properties
5 Fate and Transport
5 Environmental Fate and Transport Processes Overview
5.1 Fate and Transport Introduction
5.2 Phase Partitioning
5.3 Media-Specific Migration Processes
5.4 Transformations
5.5 PFAS Uptake into Aquatic Organisms
5.6 PFAS Uptake into Plants
6 Occurrence
6 Media-Specific Occurrence Overview
6.1 Air
6.2 Soil and Sediment
6.3 Groundwater
6.4 Surface Water
6.5 Biota
7 Health Effects
7 Human and Ecological Health Effects of select PFAS Overview
7.1 Human Health Effects
7.2 Ecological Toxicology
8 Basis of Regulations
8 Basis of Regulations Overview
8.1 Introduction
8.2 Regulatory Programs
8.3 Differences in the Available Regulations, Advisories, and Guidance Regulatory
9 Site Risk Assessment
9 Site Risk Assessment Overview
9.1 Human Health
9.2 Ecological Risk Assessment
9.3 Uncertainty
10 Site Characterization
10 Site Characterization Overview
10.1 Site Characterization Issues Relevant to PFAS
10.2 Initial Steps
10.3 Site Investigation
10.4 Data Analysis and Interpretation
10.5 Source Identification
11 Sampling and Analysis
11 Sampling and Analytical Methods Overview
11.1 Sampling
11.2 Analytical Methods/Techniques
11.3 Data Evaluation
11.4 Source Identification
12 Treatment Technologies
12 Treatment Technologies Overview
12.1 Overview
12.2 Field-Implemented Liquids Treatment Technologies
12.3 Field-Implemented Solids Treatment Technologies
12.4 Incineration
12.5 Limited Application and Developing Liquids Treatment Technologies
12.6 Limited Application and Developing Solids Treatment Technologies
12.7 Integrated Remedial Solutions
12.8 Sustainability of PFAS Treatment
12.9 Improving Evaluation of PFAS Treatment Technologies
13 Stakeholder Perspectives
13 Stakeholder Perspectives Overview
13.1 Stakeholder Concerns
13.2 Specific Tribal Stakeholder Concerns
13.3 Stakeholder Resources
14 Risk Communication
14 Risk Communication Overview
14.1 Role of Risk Perception: Public Stakeholders and Decision Makers
14.2 Risk Communication Challenges
14.3 Risk Communication Planning and Engagement Tools
15 Case Studies
15 Case Studies Overview
15.1 Site Characterization Case Studies
15.2 Treatment Case Studies
15.3 Risk Assessment Case Study
15.4 Risk Communication Case Studies
16 Surface Water Quality
16 Surface Water Quality
16.1    Introduction
16.2 Protection of Human Health
16.3 Protection of Biota
16.4 Sampling and Analysis
16.5 Surface Water Foam
Additional Information
References
17 Additional Information
17 Additional Information Overview
17.1 Additional Information for Media-Specific Occurrence
17.2 Additional Information for Human Health Effects
17.3 Additional Information for Risk Assessment
Acronyms
Glossary
Acknowledgments
Team Contacts
Document Feedback
ITRC & Environmental Justice/Diversity Equity & Inclusion

 

PFAS — Per- and Polyfluoroalkyl Substances
HOME

1 Introduction

A PFAS introduction Video is available.

Per- and polyfluoroalkyl substances (PFAS) constitute a large family of fluorinated chemicals, exceeding several thousand that might be in commercial use or the environment, that vary widely in their chemical and physical properties. The persistence and mobility of some PFAS, combined with decades of widespread use in industrial processes, certain types of firefighting foams, and consumer products, have resulted in their being present in environmental media at trace levels across the globe. PFAS have relatively recently come to the attention of investigators and the public in large part due to the fact that until the early 2000s analytical methods to detect low levels of PFAS in the environment were available only in a few select research institutions. It was not until the early 2010s that these methods to detect a limited number of PFAS became widely available and had detection limits in water low enough to be commensurate with levels of potential human health effects. Toxicological studies have raised concerns regarding the bioaccumulative nature and potential health concerns of some PFAS. As a result, our understanding of PFAS and the risks they may pose is rapidly evolving.

Broadly speaking, PFAS are characterized as having carbon atoms linked to each other and bonded to fluorine atoms, by which the fluorination imparts properties to the molecule. The carbons may be partially fluorinated (polyfluorinated) or fully fluorinated (perfluorinated). Modifying characteristics, such as addition of a functional group, other substitutions (for example, chlorine), and partial fluorination, are described in Section 2.2 along with evolving definitions of PFAS.

This guidance document is designed specifically to support state and federal environmental staff, as well as others (including stakeholders, project managers, and decision makers), to gain a working knowledge of the current state of PFAS science and practice. Developed by a team of over 400 environmental practitioners drawn from state and federal government, academia, industry, environmental consulting, and public interest groups, it also provides a summary of the current understanding of all aspects of PFAS from a broad perspective. While every effort was made to keep the information accessible to a wide audience, it is assumed the reader has some basic technical background in chemistry, environmental sciences, and risk assessment. The document addresses the following questions:

Questions Document Sections
What are PFAS?
  • Naming Conventions and Use
  • Chemistry, Terminology, and Acronyms
  • PFAS Uses
  • PFAS Releases to the Environment
  • Firefighting foams (AFFF)
How do they behave in the environment?
  • Physical and Chemical Properties
  • Environmental Fate and Transport Processes
  • Media-Specific Occurrence
Why are we concerned about PFAS?
  • Human and Ecological Health Effects
  • Basis of Regulations
  • Site Risk Assessment
  • Surface Water Quality
How do we evaluate PFAS in the environment?
  • Site Characterization
  • Sampling and Analytical Methods
  • Case Studies
How do we remediate PFAS?
  • Treatment Technologies
What are the major concerns of communities and Tribes and
how do we share what we know about PFAS?
  • Stakeholder Perspectives
  • Risk Communication

The thousands of chemicals that make up the large family known as PFAS can be divided into two major classes: nonpolymers and polymers. This document focuses primarily on those nonpolymer PFAS that, to date, are most commonly detected in the environment, particularly the highly persistent perfluoroalkyl acids (PFAAs), some of the better-known replacements for phased-out long-chain PFAAs, and some of the “precursor” chemicals—PFAS that can break down to form PFAAs. These precursors include polyfluorinated alkyl substances and a subset of polymer PFAS known as side-chain fluorinated polymers (Washington et al. 2018). Many polymer PFAS, especially certain high–molecular weight fluoropolymers, are insoluble in the environment and not bioavailable, and therefore less of a concern to human and ecological health (Henry et al. 2018), so are not discussed in detail in this document. As this paragraph illustrates, it is important to be very clear about which PFAS is being discussed and what its particular physical and chemical properties are, and that is where this document begins.

The physical and chemical properties that make some PFAS persistent and mobile in the environment also make them particularly challenging to analyze and remediate. Analytical methods sensitive enough to detect environmentally relevant concentrations became widely available in the early 2010s. Although analyte lists continue to expand, currently available methods still only allow identification of a small fraction of the thousands of PFAS that have reportedly been created and used since the 1950s. As existing analytical methods improve and new, nontargeted analyses become commercially available, it is likely that additional PFAS and new release sites will be identified.

Concerns have been raised regarding human health and ecological risks associated with certain PFAS. These are based on widespread detections of some PFAS in humans and wildlife, evidence that certain PFAS bioaccumulate in individuals and bioconcentrate in the food chain, and studies reporting multiple toxicological effects in animals and potential health effects in humans. However, risk assessment of PFAS is hampered by the unique physical and chemical properties of many PFAS, which result in uncertainty in identifying sources and quantifying source area mass, complex fate and transport in the environment, poorly understood biological and chemical transformation pathways, and unique bioaccumulation processes. Moreover, the widespread presence of some PFAS in environmental media and the many potential PFAS sources also complicate interpretation of site data. Data evaluation methods to help distinguish between site-specific anthropogenic “background” PFAS, PFAS that are site-related, and PFAS from another nearby source are still being developed.

As with other emerging contaminants, our evolving understanding of PFAS and the volume of scientific studies makes it difficult for most environmental practitioners to stay current with the critical information about these chemicals. Meanwhile, public concern about PFAS has created pressure on state and federal agencies to take action, resulting in a patchwork of evolving regulatory approaches and regulatory standards, screening values, and guidance values. As with any new and evolving area of science, our knowledge is far from complete.  We have attempted to alert the reader to areas where information is still uncertain or conflicting interpretations exist.

Updated May 2021

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