Concerns about the potential public health hazards of human exposure to per- and polyfluoroalkyl substances (PFAS) continue to increase as scientists learn more about these chemicals. The large number of PFAS compounds–over 4,000–present considerable challenges. The available toxicity and epidemiology data are currently limited to the evaluation of only a few chemicals. Different PFAS compounds have different physical and chemical characteristics that may result in different toxicities, bioavailabilities, and fate and transport characteristics.
PFAS (per- and polyfluoroalkyl substances) are used in a number of consumer products for their waterproof, greaseproof, stain-proof and nonstick properties and for industrial purposes (e.g., fire-fighting foam). As a result, PFAS chemicals are found in the food, water, air, and bodies of people around the world.
Of the thousands of PFAS in existence, the few that have been thoroughly studied show adverse impacts on the endocrine, immune, and metabolic systems. The following discussion of health effects is limited to those PFAS substances that have been studied. More research is clearly needed to better understand the potential health effects of all PFAS substances.
The health effects of perfluoroctane sulfonic acid (PFOS), perfluoroctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA), for example, have been studied more widely than other per- and polyfluoroalkyl substances (PFAS). Some, but not all, studies in humans with exposure to PFAS have shown that certain PFAS may:
- Affect growth, learning, and behavior of infants and older children
- Lower a woman’s chance of getting pregnant
- Interfere with the body’s natural hormones
- Increase cholesterol levels
- Reduce the immune response
- Increase the risk of cancer
- Change liver function
- Increase the risk of pregnancy-induced hypertension/preeclampsia
- Increase the risk of thyroid disease
These effects are observed at relatively low amounts. Health effects observed in human epidemiological studies are also supported by some research using mice and rats. Evidence also suggests the increased possibility of kidney and testicular cancer at higher PFOS and PFOA concentrations. The current data, however, support noncancer effects occurring at lower exposures than required to cause cancer effects. Scientists are still learning about the health effects of exposure to mixtures of PFAS.
Studies show that approximately 99 percent of the people in the United States have been exposed to PFAS and have PFAS in their blood, especially PFOS and PFOA. While both PFOA and PFOS are no longer manufactured in the United States, they can still be found in products manufactured in other countries. Blood concentrations of PFAS have decreased since the production and use of PFOS and PFOA in the United States have decreased.
Health Effects of Different PFAS
While many of the same effects are observed for the entire family of PFAS chemicals studied, it appears that different adverse health impacts may be dominant in different PFAS. Critical information may come from investigating whether exposure to structurally similar PFAS causes similar health effects. Differences in mobility, fate and persistence in the environment, as well as
the ability to treat PFAS contamination in air, soil, and water across the complex family of PFAS, are expected to contribute to differences in potential exposure routes and resulting health risks to humans.
Currently, long-chain PFAS are generally thought to be more toxic in humans than shorter-chain PFAS. However, much less is known about the toxicities of short-chain PFAS. Short-chain PFAS appear to be as persistent in the environment as long-chain PFAS and are generally more mobile in soil and water. Environmental and human exposure to short-chain PFAS are expected to increase over time due to increased production and their use as substitutes for long-chain PFAS.
PFAS Levels and Guidance
There are no federal regulatory levels set for PFAS, although some states have established their own guidance and screening levels. In 2016, the EPA issued a recommended Lifetime Health Advisory (HA) of 70 parts per trillion (ppt) for individual and combined PFOA and PFOS in drinking water. The EPA has made it a priority to conduct a new toxicity assessment for GenX chemicals and an updated toxicity assessment for PFBS to facilitate hazard characterization. Toxicity values for these replacement chemicals will help inform risk management decisions. The EPA plans to release final toxicity values for GenX chemicals and Perfluorobutane Sulfonic Acid (PFBS) in 2019. Toxicity values for five other PFAS are under development.