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PFAS — Per- and Polyfluoroalkyl Substances

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PFAS Home Page
About ITRC
Navigating This Website
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 and Products
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, Sediment, and Biosolids
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 Risk Assessment
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 Forensics and Source Identification
11 Sampling and Analysis
11 Sampling and Analysis 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 Air Treatment Technologies
12.6 Limited Application and Developing Liquids Treatment Technologies
12.7 Limited Application and Developing Solids Treatment Technologies
12.8 Integrated Water Treatment Solutions
12.9 Sustainability of PFAS Treatment
12.10 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
15.5 Surface Water Quality 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
16.6 Effluent Limits for PFAS
16.7 Surface Water/Groundwater Interaction
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
References
Acronyms
Glossary
Acknowledgments
Team Contacts
Document Feedback
ITRC & Environmental Justice/Diversity Equity & Inclusion

 

PFAS — Per- and Polyfluoroalkyl Substances
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Glossary

A

Adsorption
The mechanism whereby ions or compounds within a liquid or gas adhere to a solid surface upon contact. The term also refers to a method of treating wastes in which activated carbon is used to remove organic compounds from wastewater.

Anion
A negatively charged ion.

Arithmetic mean
The sum of a collection of numbers divided by the number of numbers in the collection, commonly referred to as the “average”.

B

Biochar
A carbon-rich, porous solid synthesized by heating biomass, such as wood or manure, in a low-oxygen environment (pyrolysis).

Biomaterials
Materials derived from plants or animals created for use as sorption materials.

C

Cation
A positively charged ion.

Coagulation
The process of destabilizing a colloid or suspension that unbalances the forces that separate the particles, often by neutralizing the charges on the particles and allowing the particles to clump or settle.

E

Electro precipitation/electrocoagulation
The use of an electrical current to enhance the coagulation and precipitation of ionic compounds. The electrical current may attract the compounds to an anode or cathode, or create coagulating ions from a sacrificial anode, or both.

Empty Bed Contact Time (EBCT)
A measure of the time during which water to be treated is in contact with the treatment medium in a contact vessel, assuming that all liquid passes through the vessel at the same velocity. EBCT is equal to the volume of the empty bed divided by the flow rate (Sacramento State University 2019).

F

Flocculation
A process in which the suspended particles of a destabilized colloid or suspension form groups or clumps (known as a “floc”). Coagulation and flocculation work together to separate solids and liquids containing colloids and suspensions.

Fluorotelomer substance
A polyfluoroalkyl substance produced by the telomerization process.

G

Geometric mean
The central tendency or typical value of a set of numbers, derived by multiplying the numbers in a set then finding the nth root of the product, where “n” is the number of values in the set.

H

Head
The part of a molecule that is a charged functional group attached at one end of the carbon chain tail.

I

Incineration
Thermal destruction process typically characterized by oxidation at temperatures in excess of 1,000°C.

Isomers
Chemicals with the same chemical formula, but different molecular structures.

M

Membrane fouling
Loss of production capacity of a membrane due to accumulation of compounds or biogrowth on the membrane.

Micelles
Particles in which long hydrocarbon tails, repelled by the water molecules and attracted to each other, make up the interior, whereas the negatively charged heads coat the surface and interact with the surrounding water molecules and positive ions (Ege 1999).

Mineralization/decomposition/destruction
The breakdown of a chemical compound into its constituent elements and carbon dioxide and water.

Moiety
A specific group of atoms within a molecule that is responsible for characteristic chemical reactions of that molecule (Helmenstine 2019).

O

Organoclays
A naturally occurring clay mineral that is organically modified to incorporate cations and enhance the sorption capability.

P

Perfluorinated chemical
Subset of PFAS. Have carbon chain atoms that are totally fluorinated. Examples are perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) (Buck et al. 2011).

Perfluoroalkyl substance
Fully fluorinated alkane (carbon chain) molecule. They have a chain (tail) of two or more carbons atoms with a charged functional group (head) attached at one end.

Permeate
The water treated by a membrane filtration technology, which has passed through the membrane, and from which PFAS have been removed. The contaminants not passing the membrane accumulate in the filtrate, which also does not pass through the membrane.

Polyfluorinated chemical
Subset of PFAS. Have at least one carbon chain atom that is not totally fluorinated (Buck et al. 2011).

Polyfluoroalkyl substance
The molecule has a nonfluorine atom (typically hydrogen or oxygen) attached to at least one, but not all, carbon atoms, while at least two or more of the remaining carbon atoms in the carbon chain tail are fully fluorinated.

Polymer
Large molecules formed by combining many identical smaller molecules.

R

Reactivation
The process of treating regenerated GAC to restore treatment properties.

Redox
Chemical reduction-oxidation processes and conditions that can result in the alteration of a chemical compound.

Regeneration
The act of restoring some of the sorption capacity of a sorptive media (that is, activated carbon or ion exchange) by removing the adsorbed matter. For carbon, regeneration is a thermal oxidation process.

S

Sorption
Removal of a compound from solution by solid phase constituents. This term is often used when the mechanism of removal (adsorption, absorption, or precipitation) is unknown. (Thompson and Goyne 2012).

Stabilization
A process to reduce mobility of compounds in the environment through physical or chemical means.

Surfactant
A surface-active agent that lowers the surface tension of a liquid.

T

Tail
The part of a molecule that is a chain of two or more carbon atoms.

Thermal desorption
Thermal treatment process intended to remove the contaminants from a solid medium (such as soil, sediment, carbon) and drive them into the vapor phase.

Z

Zwitterion
An ionic compound containing both positively and negatively charged groups with a net charge of zero.

Glossary Lookup List

Search:
(clear)
  • The mechanism whereby ions or compounds within a liquid or gas adhere to a solid surface upon contact. The term also refers to a method of treating wastes in which activated carbon is used to remove organic compounds from wastewater.
  • Air Force Center for Engineering and the Environment AMA American Management Association
  • A negatively charged ion.
  • The sum of a collection of numbers divided by the number of numbers in the collection, commonly referred to as the “average”.
  • A carbon-rich, porous solid synthesized by heating biomass, such as wood or manure, in a low-oxygen environment (pyrolysis).
  • Materials derived from plants or animals created for use as sorption materials.
  • A positively charged ion.
  • The process of destabilizing a colloid or suspension that unbalances the forces that separate the particles, often by neutralizing the charges on the particles and allowing the particles to clump or settle.
  • Empty Bed Contact Time: A measure of the time during which water to be treated is in contact with the treatment medium in a contact vessel, assuming that all liquid passes through the vessel at the same velocity. EBCT is equal to the volume of the empty bed divided by the flow rate (Sacramento State University 2019).
  • The use of an electrical current to enhance the coagulation and precipitation of ionic compounds. The electrical current may attract the compounds to an anode or cathode, or create coagulating ions from a sacrificial anode, or both.
  • A measure of the time during which water to be treated is in contact with the treatment medium in a contact vessel, assuming that all liquid passes through the vessel at the same velocity. EBCT is equal to the volume of the empty bed divided by the flow rate (Sacramento State University 2019).
  • A process in which the suspended particles of a destabilized colloid or suspension form groups or clumps (known as a “floc”). Coagulation and flocculation work together to separate solids and liquids containing colloids and suspensions.
  • A polyfluoroalkyl substance produced by the telomerization process.
  • The central tendency or typical value of a set of numbers, derived by multiplying the numbers in a set then finding the nth root of the product, where “n” is the number of values in the set.
  • The part of a molecule that is a charged functional group attached at one end of the carbon chain tail.
  • Thermal destruction process typically characterized by oxidation at temperatures in excess of 1,000°C.
  • Chemicals with the same chemical formula, but different molecular structures.
  •  
  • Particles in which long hydrocarbon tails, repelled by the water molecules and attracted to each other, make up the interior, whereas the negatively charged heads coat the surface and interact with the surrounding water molecules and positive ions (Ege 1999).
  • The breakdown of a chemical compound into its constituent elements and carbon dioxide and water.
  • A specific group of atoms within a molecule that is responsible for characteristic chemical reactions of that molecule (Helmenstine 2019).
  • Nonafluoro-3,6-dioxaheptanoic acid
  • A naturally occurring clay mineral that is organically modified to incorporate cations and enhance the sorption capability.
  • Subset of PFAS. Have carbon chain atoms that are totally fluorinated. Examples are perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) (Buck et al. 2011).
  • Fully fluorinated alkane (carbon chain) molecule. They have a chain (tail) of two or more carbons atoms with a charged functional group (head) attached at one end.
  • The water treated by a membrane filtration technology, which has passed through the membrane, and from which PFAS have been removed. The contaminants not passing the membrane accumulate in the filtrate, which also does not pass through the membrane.
  • Subset of PFAS. Have at least one carbon chain atom that is not totally fluorinated (Buck et al. 2011).
  • The molecule has a nonfluorine atom (typically hydrogen or oxygen) attached to at least one, but not all, carbon atoms, while at least two or more of the remaining carbon atoms in the carbon chain tail are fully fluorinated.
  • Large molecules formed by combining many identical smaller molecules.
  • The process of treating regenerated GAC to restore treatment properties.
  • Chemical reduction-oxidation processes and conditions that can result in the alteration of a chemical compound.
  • The act of restoring some of the sorption capacity of a sorptive media (that is, activated carbon or ion exchange) by removing the adsorbed matter. For carbon, regeneration is a thermal oxidation process.
  • Removal of a compound from solution by solid phase constituents. This term is often used when the mechanism of removal (adsorption, absorption, or precipitation) is unknown. (Thompson and Goyne 2012)
  • A process to reduce mobility of compounds in the environment through physical or chemical means.
  • A surface-active agent that lowers the surface tension of a liquid.
  • The part of a molecule that is a chain of two or more carbon atoms.
  • Thermal treatment process intended to remove the contaminants from a solid medium (such as soil, sediment, carbon) and drive them into the vapor phase.
  • An ionic compound containing both positively and negatively charged groups with a net charge of zero.

Updated September 2023.

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