Testing POU RO Systems for Reduction of PFOA and PFOS
By Rick Andrew
There’s been quite a bit of media and political attention focused on groundwater and drinking water contaminated by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). 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. These chemicals have historically been used industrially as emulsifiers in the manufacturing of fluoropolymers. Because of their unique ability to withstand water, grease and high temperatures, PFOS and PFOA have been used in very specific applications demanding these characteristics, including paper and cardboard food packaging, insecticides, electronics, stain repellants, paints, plumbing tape, firefighting foam and non-stick cookware coatings.
Production of PFOA and PFOS was phased out in the early 2000s. By this time, large quantities of these chemicals had been released into the environments surrounding the locations where they were manufactured. Investigations into these environments have detected PFOA and PFOS in the drinking-water supplies in Hoosick Falls (NJ) Decatur (AL) Oscoda (MI) and Little Hocking (OH) as well as others near former manufacturing locations. 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 also revealed detectable levels of PFOA and PFOS in drinking-water supplies across the county.
Given the widespread usage of these chemicals (including usage in non-stick cookware coatings) it is not surprising that PFOA and PFOS have been detected at low levels in blood samples of the general US population. These contaminants are readily absorbed by the body; once ingested they tend to concentrate primarily in the blood serum, liver and kidneys. Within the body, PFOA and PFOS have a half-life of 2.3 years and 5.8 years, respectively. Because of this relatively long half-life, repeated exposure at very low levels can result in accumulation in the body at levels that result in adverse health outcomes.
Epidemiological studies of workers exposed to high levels of PFOA and PFOS, and residential populations near manufacturing facilities, have demonstrated a positive association between serum concentrations and increased cholesterol, decreased bilirubin, low birth weight, immunological effects and cancer. In addition to the epidemiological studies, animal studies of rats, mice and monkeys exposed to PFOA and PFOS have shown increased liver weight, liver hypertrophy, necrosis, developmental/neurodevelopmental delays, decreased spleen weight and delayed puberty.
Testing reduction of PFOA and PFOS
NSF has developed NSF Protocol P473 covering reduction of PFOA and PFOS because of the increasing concerns related to those chemicals being detected in drinking-water supplies. It specifies a test method and reduction criteria for establishing claims of PFOA and PFOS reduction for POU RO systems. Building on the American national standard for POU RO systems, the basic test methodology for NSF P473 is based on the protocol for health effects contaminant reduction under NSF/ANSI 58 for RO systems.
The test method is designed to address treatment only by the RO membrane. It involves testing for seven days under a variety of usage scenarios. For example, the test method for typical RO systems with storage tanks includes drawing small volumes of water from the storage tank when sampling, as well as completely emptying the tank when sampling, at different points in the test. The entire test period utilizes an inlet pressure of 50 psi. This testing does not include any assessment of treatment capacity, because the basis of treatment for an RO system making claims of PFOA and PFOS reduction is assumed to be rejection by the membrane. For these reasons, reduction claims are tested on systems that have the pre- and post-filters removed. 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 chemicals 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 were based on a review of US EPA occurrence data generated under US EPA’s UCMR3 monitoring samples from 2013 to 2015. The level 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.
For PFOA, the challenge water concentration was developed from private well and public water-supply sampling in Hoosick Falls. 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, based on using Hoosick Falls monitoring sample results, 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.
NSF P473 establishes a total combined maximum allowable treated water concentration of PFOS and PFOA of 0.07 µg/L, which is 0.07 parts per billion or 70 parts per trillion (see Table 1). This level is based on a US EPA Health Advisory issued in 2016 (see https://www.epa.gov/ground-water-and-drinking-water/drinking-water-health-advisories-pfoa-and-pfos). 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.
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 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 parts per trillion concentrations required by the US EPA Health Advisory level as specified in NSF P473.
Similar to all of the NSF/ANSI Drinking Water Treatment Units standards, NSF P473 includes requirements for product literature, which are based on those of 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. 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 Table 2.
A scientific approach
Throughout the development of NSF P473, the focus was consistently on protection of human health and an approach founded in sound science. Using US EPA’s Health Advisory (issued in 2016) as a basis for contaminant levels, specifying analysis by the latest and most sophisticated and capable analytical instruments and relying on a proven scientifically grounded testing protocol combine to make NSF P473 a very robust tool for establishing contaminant reduction capabilities of POU RO systems. This focus on human health and foundation in science, which are core principles for all of NSF’s work, benefits all stakeholders.
NSF P473 allows manufacturers to establish consumer confidence for those end users seeking to treat their water for potential contamination by PFOA and PFOS. Further, regulators can direct those end users with concerns about PFOA and PFOS in drinking water to POU treatment systems that meet the requirements of NSF P473. The benefits of NSF P473 are there for all.
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