Environmental Protection Agency Opens Public Comment Period for Draft Toxicological Review of PFNA

The Environmental Protection Agency (EPA) has opened a 60-day public comment period on the draft Integrated Risk Information System (IRIS) Toxicological Review of Perfluorononanoic Acid (PFNA, CASRN 375–95–1) and Related Salts. This draft document prepared by the Center for Public Health and Environmental Assessment (CPHEA) within EPA's Office of Research and Development (ORD), precedes a contracted peer review. Comments received will be shared with the external peer reviewers. A public meeting organized by ERG, an EPA contractor, will be held during Step 4 of the IRIS Process to discuss the draft report. Public comments and feedback from the meeting will be considered by the external peer reviewers. The deadline for submitting comments is May 7, 2024.

Background and Proposed Reference Doses

In 2018, EPA announced its intention to assess five members of the per- and polyfluoroalkyl substance (PFAS) class using IRIS. The Agency had previously established Reference doses (RfDs) for perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) and proposed RfDs for perfluorohexane sulfonate (PFHxS) and perfluorodecanoic acid (PFDA).

EPA has now proposed an RfD for perfluorononanoic acid (PFNA), that is in the mid-range compared to the other PFAS assessed by IRIS. The proposed RfD for PFNA, set at 7x10^-9 milligrams per kilogram per day (mg/kg per day), is significantly more stringent than the final RfDs for PFBA and PFHxA established in 2022 and 2023.

While RfDs generated by IRIS do not have direct legal implications, EPA may use them for regulatory risk assessments.

Concerns

Perfluorononanoic acid (PFNA) and its related salts are part of the group of per- and polyfluoroalkyl substances (PFAS). These synthetic compounds, which do not occur naturally, have found widespread use in consumer goods and industrial processes over the past several decades due to their resistance to heat, oil, stains, grease, and water. Concerns regarding PFNA and other PFAS arise from their resistance to hydrolysis, photolysis, and biodegradation, which leads to their persistence in the environment.

PFNA, commonly used in the production of fluoropolymers, can be found in various products such as carpets, food contact papers, cleaning and polishing products.

Health Effects of PFNA Exposure

Human epidemiologic studies have examined connections between PFNA exposure and several health outcomes, including fetal growth restriction, liver serum biomarkers, antibody responses, infectious diseases, sensitization and allergic responses, semen parameters, reproductive hormones, pubertal development, thyroid hormones, neurodevelopment, serum lipids, cardiovascular disease, metabolic effects, time to pregnancy, female reproductive responses, and urinary effects.

However, with the exception of reduced birth weight and increased serum ALT in adults, the ability to make conclusive judgements about these associations based on human evidence is limited.

Available evidence suggests potential immune, thyroid, neurodevelopmental, and cardiometabolic effects from oral exposure to PFNA under specific exposure conditions but is not sufficient to draw definitive conclusions. Medium-reliability epidemiological studies indicate potential immunosuppression, primarily related to prenatal and childhood exposures, resulting in reduced antibody responses following vaccinations. The evidence is insufficient to conclude that PFNA can cause immunotoxicity.