EPA Researchers Develop a Chemical Category-Based Approach to Prioritize PFAS for Data Collection
Published October 24, 2024
Per- and polyfluoroalkyl substances (PFAS) are widely used, human-made chemicals that are found in water, air and soil across the nation and around the globe. Scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful effects for human health and the environment. Though there are thousands of PFAS that have been introduced to the environment, only a handful have been characterized for their potential toxicity, leaving the vast majority unstudied.
Congress directed EPA to develop a process to prioritize which PFAS should be subject to additional research based on their potential for human exposure, toxicity and other available information. The Toxic Substances Control Act (TSCA) requires reporting, record-keeping, testing requirements and restrictions for chemicals of concern, including PFAS.
To help meet these requirements, EPA researchers developed a chemical category-based approach to help prioritize PFAS for further data collection efforts. Rather than assessing each PFAS individually, closely related PFAS could be grouped together into chemical categories. An earlier version of the category-based approach was used by the agency to develop the National PFAS Testing Strategy.
“This prioritization effort is critical as it facilitates the agency’s ability to determine which substances to consider first based on consistent parameters,” said EPA’s Center for Computational Toxicology and Exposure Director, Rusty Thomas. “The data EPA provides on PFAS can help states, Tribes and other public health officials make informed decisions and prevent adverse health outcomes.”
In the categorization approach, EPA researchers created a wide array of candidate PFAS using the structural definition of PFAS that was applicable to several TSCA activities. Each PFAS was then assigned into a primary category using structure classifications that were aligned with the categories defined by the Organisation for Economic Co-operation and Development (OECD). The primary categories were then further broken down into smaller categories based on characteristics that are important in toxicity and how long they last in the human body. Finally, the researchers examined how structurally similar the chemicals were in each category and determined whether to break down the category further. Structurally similar chemicals tend to have similar health effects at similar exposure levels.
The researchers ultimately developed over a hundred categories. The categories were prioritized for data collection based on various considerations including availability of toxicity data, detection by monitoring efforts in the different states that may indicate exposure and other considerations. Researchers then chose specific PFAS from the high priority categories based on how representative they were to others in the category and the ability to identify plausible manufacturers/importers that could be responsible for additional data collection.
“Overall, by selecting high priority categories and the most representative PFAS, we are able to save valuable resources while advancing the science to understand the potential human health risks from PFAS,” said EPA research chemist Grace Patlewicz.
The methods developed for categorizing the PFAS landscape in this work provide an essential foundation to help the EPA address the many challenges associated with evaluating the environmental and human health impacts of this class of chemicals.
You can watch a recording of the November 14, 2024, webinar about this PFAS Categorization effort in the EPA’s Computational Toxicology Communities of Practice webinar series. This recorded webinar and recordings of previous webinars are accessible on the Computational Toxicology Communities of Practice webpage.
Learn More About the Science
Read the recent EPA publication.