As presented above, PFAS are found in many consumer products and in the environment, which has resulted in multiple potential routes of exposure to humans. However, a common route of exposure to PFAS compounds is through drinking water. Analytical techniques to identify PFAS are being developed as the U.S. Environmental Protection Agency (EPA) works to certify additional testing methods.
Testing Guidance
Under the Safe Drinking Water Act, EPA monitors unregulated contaminants in drinking water and adds new pollutants to the list of priority contaminants every five years. The Unregulated Contaminant Monitoring Rule (UCRM) requires systems to identify and collect data for drinking water contaminants in public water systems that do not have health-based standards. The EPA testing guidance supports the generation of data collected to determine exposure levels and inform regulatory needs.
In 2012, EPA published the third UCMR (UCMR 3) and listed PFAS, including PFOA and PFOS, as priority contaminants.
Prior to this, EPA announced the third Drinking Water Contaminant Candidate List (CCL 3) in February 2008 and included PFAS compounds.
UCMR 5 was published on March 11, 2021, and listed 30 chemical contaminants to be sampled between 2023 and 2025: 29 of the 30 chemicals included on UCMR 5 are PFAS. The proposed UCMR 5 will provide new data to improve EPA’s understanding of the frequency that PFAS are found in the nation’s drinking water systems and at what levels. Regarding the UCMR, EPA Assistant Administrator Radhika Fox said, “All people need access to clean and safe drinking water. One way that EPA is committed to keeping our communities safe is by addressing PFAS.”
On Oct. 18, 2021, EPA announced its comprehensive Strategic Roadmap to confront PFAS contamination. This Strategic Roadmap is centered on three main strategies:
- Increase investment in PFAS research.
- Leverage authorities to prevent the release of PFAS into the environment.
- Accelerate cleanup of PFAS contamination.
As PFAS are detected, EPA continues to advance its analytical methods. Method 537.1, published in 2018, guides the measurement of 18 PFAS in drinking water. Short-chain — carbon chain lengths of four to six — PFAS present physiochemical differences. In 2019, EPA introduced Method 533, a complement to 537.1, focusing on short-chain PFAS, bringing the total identifiable PFAS to 70 chemicals. Method 533 also analyzes for certain replacement PFAS that were used to replace PFOA and PFOS following their phase out.
Testing Techniques
When used together, EPA standards and recent laboratory methods can identify more than 70 PFAS compounds in drinking water. The two methods differ in the type of solid-phase extraction media used:
- Method 537.1 uses styrene-divinylbenzene (SDVB) media.
- Method 533 uses polystyrene divinylbenzene with a positively charged diamino ligand and isotope dilution.
The two methods also stipulate different holding times for the samples:
- Method 537.1 provides a 14-day time frame to extract the sample and 28 days for analysis.
- Method 533 provides 28 to extract the sample and 28 days for analysis.
Both techniques are analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/ MS) and Method 533 leverages MS/MS in multiple reaction monitoring (MRM) mode for enhanced selectivity.
Drinking water testing is complex, and the different methods require precision and skill. The analytical methods being used are Method 537.1, Method 533, total organofluorine and non-target analytical methods, such as liquid chromatography coupled to high resolution quadrupole time-of-flight mass spectrometry. Given the robust and comprehensive approaches to PFAS testing, EPA guidance provided is intended for use by skilled analysts.