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Per- and Polyfluoroalkyl Substances (PFAS)

Final reports from the Per- and Polyfluoroalkyl Substances (PFAS) 28-Day toxicity studies TOX-96 and TOX-97 are now available.

Background Information

Per- and polyfluoroalkyl substances, or PFAS, are a large group of manufactured compounds widely used to make everyday products more resistant to stains, grease, and water. For example, these chemicals are used to keep food from sticking to cookware, make stain-resistant sofas and carpets, waterproof clothing and mattresses, and may also be used in some food packaging, as well as in some firefighting materials. Because they help reduce friction, they are also used in a variety of other industries including aerospace, automotive, building and construction, and electronics.

As a class, PFAS contains thousands of chemicals. Humans can be exposed to PFAS through a variety of ways. Ingestion—particularly through drinking water—is the main way individuals or communities are exposed, but recent studies suggest that other exposure pathways, including inhalation and skin absorption, also contribute.

NTP Studies

NTP is working to assess the potential health effects of PFAS through a large research effort with multiple facets including experimental animal and cell-based test systems, literature review, and computer modeling, among others.

What did the studies find?

See table below for the most up-to-date information on the variety of projects taking place at NTP.

Study Description Status Findings & Supporting Files
Toxicology Research
28-Day Toxicity Studies Study in rats comparing toxicity of short- and long-chain carboxylates (n = 4) and sulfonates (n = 3) Completed Findings:
  • Long- and short-chain PFAS affected the same organ systems—the liver and thyroid hormone
  • Higher doses of short-chain PFAS were needed to have similar effects on liver and thyroid hormone when compared to long-chain PFAS
Supporting files:
2-Year Toxicity and Carcinogenicity Studies Comparison of cancer/toxicity outcomes in rats with lifetime exposure to PFOA, and those with only post-weaning exposure to PFOA Ongoing Supporting files:
  • Data tables for PFOA 2-year study
  • Technical Report 598: Anticipated fall 2019 for public comment and peer review
Toxicokinetic Studies An evaluation of chemical clearance from the body, known as toxicokinetics, for seven PFAS chemicals in rats Ongoing Findings:
  • The clearance of short-chain PFAS was quicker than with long-chain PFAS
  • PFAS concentrations were generally higher in the liver than in the brain
Supporting files:
  • Huang et al. 2019
  • Huang et al., in preparation (8:2 fluorotelomer alcohol): Anticipated fall 2019
  • Dzierlenga et al., in preparation (Carboxylates): Anticipated fall 2019
Immunotoxicity Studies Rat and cell-based studies to determine the potential of PFAS to impact immune system function Completed Findings:
  • In rats, one type of PFAS known as PFDA had adverse effects in liver
  • In human cell lines, exposure to PFOA and PFOS suppressed the release of a certain type of immune signaling molecule; both types of PFAS may be using a different mechanism to achieve this suppression
Supporting files:
Neurotoxicity Studies Cell-based studies in rat neuron-like cells to evaluate potential neurotoxicity of four PFAS Completed Findings:
  • Certain PFAS could impact neurodevelopment by targeting neuron cell differentiation
  • PFAS alterations to the cells differed among the four PFAS tested
Supporting files:
Mitochondrial Toxicity Studies Cell-based studies of 16 PFAS to evaluate the potential to inhibit rat mitochondria function Completed Findings:
  • The 16 PFAS tested altered mitochondrial function
  • Long-chain PFAS were more potent than short-chain PFAS in inhibiting mitochondrial function
Supporting files:
Health Effects Assessment
2016 NTP Monograph Literature-based systematic review of PFAS’ impacts on the human immune system Completed Findings:
  • PFOA and PFOS are immune hazards to humans based on evidence from human and animal studies
Supporting files:
Responsive Evaluation and Assessment of Chemical Toxicity (REACT) Program
REACT PFAS An approach using cell-based tests comparing individual PFAS to identify common or overlapping patterns of toxicity; enables a class of chemicals to be screened for wide range of biological effects Ongoing Supporting files:

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