PFOA and PFOS Reduction
By Rick Andrew
Detection of per- and polyfluoroalkyl substances (PFAS) continues to occur in drinking and source waters. These compounds are synthetic, man-made chemicals that are highly persistent and slow to degrade in the environment. They are considered to be emerging contaminants by US EPA. The two most common are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). These chemicals, historically used in the manufacture of fluoropolymers, have a unique ability to withstand water and grease, as well as high temperatures. This makes them especially useful for certain applications, including paper and cardboard food packaging, insecticides, electronics, stain repellents, paints, plumbing tape, firefighting foam and non-stick cookware coatings.
Production of PFOA and PFOS was phased out in the early 2000s, by which time large quantities of these chemicals had been released into the environments surrounding the locations where they were manufactured. PFOA and PFOS were added to US EPA’s Unregulated Contaminant Monitoring Rule 3 (UCMR3), which was promulgated in 2012. Monitoring activity conducted under UCMR3 has revealed detectable levels of PFOA and PFOS in drinking water supplies across the country.
I need look no further than my home state of Michigan to see recent additional cases of detection in source water. In late July, about 3,100 residents of Parchment, MI (near Kalamazoo) were advised to stop drinking their water because high levels of PFAS had been detected in their source water. Some samples had been measured at concentrations in excess of 1,500 ppt (parts per trillion), compared to the US EPA Health Advisory concentration of 70 ppt.1 Then in early August, the Michigan Department of Health and Human Services issued an emergency ‘Do Not Eat’ fish consumption advisory covering the Huron River in parts of Oakland, Livingston and Washtenaw counties.2 (This one really hits close to home because the affected area of this river passes within about 200 yards of my house.)
NSF Joint Committee at work
These two cases are reflective of just the last few weeks, in just one state. This trend of detecting PFAS in drinking water and source water continues to grow nationally, with more and more issues and affected water systems coming to light with seemingly increasing frequency. Amidst these continuing discoveries, the NSF Joint Committee is moving forward with developing standards for verification of POU and POE technology performance for reduction of PFOA and PFOS. At the recent meeting of the NSF Joint Committee on Drinking Water Treatment Units on May 9, the committee unanimously voted to establish requirements in the NSF/ANSI DWTU Standards for reduction of PFOA and PFOS by activated carbon, by anion exchange resin and by POU RO.
The requirements (including test protocols) for evaluation of activated carbon and anion exchange resin will be added to NSF/ANSI 53, while the POU RO requirements for reduction of PFOA and PFOS will enhance NSF/ANSI 58. The contaminant reduction test protocols for activated carbon and POU RO will be based very closely on the protocols previously developed by NSF for NSF P473 Drinking Water Treatment Units – PFOA & PFOS. The protocol for anion exchange resin will be based very closely on the protocol for reduction of perchlorate by anion exchange resin that currently exists in NSF/ANSI 53.
Test protocols for reduction
NSF P473 specifies test methods and reduction criteria for establishing claims of PFOA and PFOS reduction for activated carbon systems and POU RO systems. Building on the American National Standards, the basic test methodology for NSF P473 is based on the protocol for chemical reduction under NSF/ANSI 53 for activated carbon systems and the protocol for health effects contaminant reduction under NSF/ANSI 58 for POU RO systems. This approach facilitates the transition of these test methods from P473 to NSF/ANSI 53 and NSF/ANSI 58. NSF P473 specifies the concentration of PFOA and PFOS in the challenge water, as well as the level of treatment that is required. The test includes mixture of both PFOA and PFOS as the contaminant challenge. This means that there is one test for reduction of both. The challenge water concentration for PFOS set in NSF P473 is based on a review of US EPA occurrence data generated under US EPA’s UCMR3 monitoring samples from 2013 to 2015.
The level for PFOS was set at the expected value at which 99 percent of the population will be exposed to waters of lower concentration, which is 1.0 µg/L, or 1.0 part per billion, PFOS. For PFOA, the challenge water concentration was developed from private well and public water supply sampling in Hoosick Falls, NY, one of the sites where contamination by PFAS has been investigated. The level was set at the expected value at which 90 percent of the population will be exposed to waters of lower concentration. The result of this approach was that the challenge concentration is higher than the maximum concentration detected under US EPA’s UCMR3 occurrence data from 2013 to 2015. This influent challenge value is 0.5 µg/L, or 0.5 parts per billion, PFOA.
NSF P473 establishes a total combined maximum allowable treated water concentration of PFOS and PFOA of 0.07 µg/L, which is 0.07 ppb, or 70 ppt. This level is based on the previously mentioned US EPA Health Advisory issued in 2016.3 To develop this level, US EPA considered a number of toxicological studies and risk assessments. They also incorporated a margin of protection for sensitive populations. See Figure 1 for the reduction requirements specified by NSF P473.
PFOA and PFOS are analyzed under a special method that is specified in Annex E of NSF P473. This method utilizes direct injection of samples into a liquid chromatography/mass spectrometry (LC/MS/MS) system in electrospray negative ionization mode. This highly sophisticated instrumental approach is necessary to accurately identify and quantify PFOA and PFOS at the very, very low ppt concentrations required by the US EPA Health Advisory level, as specified in NSF P473.
Product literature requirements
Similar to all of the NSF/ANSI Drinking Water Treatment Units standards, NSF P473 includes requirements for product literature. These requirements are based on those of NSF/ANSI 53 for activated carbon systems and NSF/ANSI 58 for RO systems. They include specific informational content that must be present in the system’s installation, operation and maintenance instructions. The protocol also includes requirements for specific information to be included in the system’s performance data sheet. Because the requirements of P473 are aligned with those of NSF/ANSI 53 and NSF/ANSI 58, the transition of PFOA/PFOS reduction requirements into those standards will be a smooth one. The actual contaminant reduction claim under NSF P473 is PFOA/PFOS reduction. The protocol requires that this claim be described in the system’s performance data sheet as indicated in Figure 2.
Evolving the standards
NSF P473 was developed in a highly scientific manner through a streamlined protocol development process. This approach facilitated the rapid roll out of certified products in the marketplace. Because P473 is similar in philosophy to and consistent in requirements with the NSF/ANSI DWTU Standards, the NSF Joint Committee on Drinking Water Treatment Units has a clear path to incorporate these requirements into NSF/ANSI 53 and NSF/ANSI 58. All of these efforts help manufacturers provide equipment to end users that can be relied upon with confidence to be an excellent solution to a contamination problem that is continuing to be detected in more and more water supplies across the United States and beyond.
- https://www.michigan.gov/mdhhs/0,5885,7-339-73970_ 71692-474469–,00.html
About the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org