Key Short-Chain PFAS Not Carcinogenic, Not Hormone Disruptor

WASHINGTON (March 18, 2019) – Three new recently published studies supported by FluoroCouncil in the peer-reviewed journal Regulatory Toxicology and Pharmacology support the conclusion that perfluorohexanoic acid (PFHxA), a key short-chain perfluoroalkyl substance (PFAS), presents negligible risk to humans.  These articles offer the latest look at exposure, health effects, and hormone (endocrine) activity related to this particular PFAS, derived from products utilized in applications that are critical to modern life. The studies conclude that PFHxA is not carcinogenic, is not a selective reproductive or developmental toxicant, and does not disrupt hormone (endocrine) activity.

PFHxA is a substance used by regulators to assess the safety of the 6 carbon (C6) short-chain fluorotelomer-based products because it is either a break-down product and/or an impurity in these products. C6 fluorotelomer-based products are relied upon in today’s medical garments, first responder gear, class B firefighting foams, and high-performance textiles.

The first set of findings, published in January 2019, come from a critical review of relevant perfluorohexanoic acid (PFHxA) toxicology data, which supports the conclusion that PFHxA is not carcinogenic, is not a selective reproductive or developmental toxicant, and does not disrupt hormone (endocrine) activity. The evaluation includes epidemiology and toxicology data.

According to the peer-reviewed analysis:

“Sufficient data exist to conclude that PFHxA is not carcinogenic, is not a selective reproductive or developmental toxicant, and does not disrupt endocrine activity. Collectively, effects caused by PFHxA exposure are largely limited to potential kidney effects, are mild and/or reversible, and occur at much higher doses than observed for perfluorooctanoic acid (PFOA). These findings clearly demonstrate that PFHxA is less hazardous to human health than PFOA.”

Human exposure was covered in the January 2019 companion study and indicates that PFHxA currently poses minimal risk to the health of the general U.S. population. The findings also show that human exposure is low and infrequent. In addition, daily intake rates for infants exposed to PFHxA through breast milk, formula and baby food clearly demonstrate very high margins of safety for PFHxA.

According to the peer-reviewed analysis:

“PFHxA and related fluorotelomer precursors currently appear to present negligible human health risk to the general population and are not likely to drive or substantially contribute to risk at sites contaminated with PFAS mixtures. PFHxA may also represent a suitable marker for the safety of fluorotelomer replacement chemistry used today.”

Finally, a critical review of the potential endocrine activity of PFHxA published in November 2018 concluded that PFHxA would not be characterized as an endocrine (hormone) disruptor as defined by the World Health Organization (WHO). The weight of the evidence analysis evaluated the potential endocrine disruptor activity of PFHxA as defined by the WHO, and found that it did not induce adverse hormone (endocrine)-related effects.

According to the peer reviewed analysis:

Overall, PFHxA showed no endocrine effects in Japanese medaka, juvenile rainbow trout, chickens or re-productive parameters in northern bobwhite with no significant activity in rodent repeated-dose toxicity, life-time cancer, or reproductive and developmental studies. In vitro, there was weak or negative activity for T [thyroid] transport protein or activation of E [estrogen], A [androgen] or T [thyroid] receptors. PFHxA was also negative in vitro and in vivo for disrupting steroidogenesis.”

Further available data, much of which can be found here, conclude there is no indication of high bioaccumulation of PFHxA and that it does not become concentrated inside the bodies of living organisms.

How are these findings useful?
These peer-reviewed assessments should be used to help inform public health decisions related to PFHxA and C6 short-chain fluorotelomer-based products. The findings can also inform site-specific risk assessments, which are used to collect information about risks to human health or the environment. This information may be used to inform regulatory decisions as well as water treatment options or whether site cleanup is needed.

About PFHxA and short-chain PFAS
PFHxA is a potential impurity and break-down product of the C6 short-chain fluorotelomer-based products.  These products are relied on in today’s medical garments, first responder gear, certain fire-fighting foams, high-performance apparel and footwear used in extreme weather and temperatures, among a variety of other everyday applications. Because the fluorotelomer products themselves are widely understood to not present toxicity concerns and not be bioavailable, regulators use PFHxA to assess the hazard of the C6 short-chain fluorotelomer-based products.

You can access much of the available data on PFHxA on the FluoroCouncil website.