By Rick Andrew
One of the hot topics in the world of drinking water (especially in the area of drinking water treatment) is perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). These compounds are not naturally found in the environment, are extremely persistent in water and soil, and are considered to be emerging contaminants by US EPA. PFOA and PFOS are man-made chemicals that have been used as emulsifiers in the manufacturing of fluoropolymers. Because of their unique ability to withstand water, grease and high temperatures, PFOS and PFOA have historically been widely used in a number of industrial and consumer applications, including paper and cardboard food packaging, insecticides, electronics, stain repellants, paints, plumbing tape, firefighting foam and probably the most familiar application, non-stick cooking surfaces.
Prior to phasing PFOA and PFOS out of production in the early 2000s, large quantities of these chemicals were released into the environment during the manufacturing processes. Since then, they have been detected in the drinking water supplies in cities surrounding the various PFOA and PFOS manufacturing facilities, such as Hoosick Falls, NY, Decatur, AL, Oscoda, MI and Little Hocking, OH, among others. Recent water supply monitoring data from US EPA’s Unregulated Contaminant Monitoring Rule 3 (UCMR3), which was promulgated in 2012, has also revealed detectable levels of PFOA and PFOS in drinking water supplies across the county.
Additionally, PFOA and PFOS have been detected at low levels in blood samples of the general US population. Once ingested, these contaminants are readily absorbed by the body and tend to concentrate primarily in the blood serum, liver and kidneys. Epidemiological studies of workers exposed to high levels of PFOA and PFOS and residential populations near manufacturing facilities have shown a positive association between serum concentrations and increased cholesterol, decreased bilirubin, low birth weight, immunological effects and cancer. 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. 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.
A new protocol
In response to this increasing focus of concern, NSF has developed NSF Protocol P473 covering reduction of PFOA and PFOS in drinking water, which includes criteria for establishing PFOA and PFOS reduction capability for POU activated carbon and RO systems. The basic test protocol methodologies for NSF P473 are based on organic contaminant reduction protocols under NSF/ANSI 53 for activated carbon systems and for health effects contaminant reduction under NSF/ANSI 58 for RO systems. The NSF P473 test protocol uses a mixture of both PFOA and PFOS as the contaminant challenge. The result is that there is one test for PFOA and PFOS reduction in which both contaminants are added to the challenge water in the same test.
The influent challenge levels for PFOS set in NSF P473 were based on a review of US EPA occurrence data arising from US EPA’s UCMR3 monitoring samples from 2013 to 2015, setting the level for PFOS at the expected value at which 99 percent of the population will be exposed to waters of lower concentration. (This influent challenge level is 1.0 µg/L, or 1.0 part per billion, PFOS.) Influent challenge levels for PFOA were based on private well and public water supply sampling in Hoosick Falls, setting the level at the expected value at which 90 percent of the population will be exposed to waters of lower concentration.
This approach, based on Hoosick Falls’ monitoring sample results, leads to an influent concentration that is higher than the maximum concentration 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. To create the challenge water in the laboratory, PFOS and PFOA are added by weight in a ratio of five parts PFOA to 10 parts PFOS to achieve the total influent concentration of 1.5 µg/L or 1.5 parts per billion of PFOS plus PFOA for the test (see Table 1).
NSF P473 establishes a total level of PFOS and PFOA added together of 0.07 µg/L, which is 0.07 parts per billion or 70 parts per trillion, as the maximum allowable treated water concentration. This level is based on a US EPA Health Advisory issued earlier in 2016 (see https://www.epa.gov/ground-water-and-drinking-water/drinking-water-health-advisories-pfoa-and-pfos). US EPA takes into account a variety of toxicological studies and risk assessments and incorporates a margin of protection for sensitive populations when developing these health advisories.
Analysis of PFOA and PFOS
The method of analysis for PFOA and PFOS is specified in Annex E of NSF P473. Essentially, the method involves direct injection of the samples into a liquid chromatography/mass spectrometry (in an LC/MS/MS system) in electrospray negative ionization mode. Basically, this is a highly sophisticated instrument used to positively identify and quantify PFOA and PFOS at the very, very low parts-per-trillion concentrations required by NSF P473, based on the US EPA Health Advisory level.
Reduction and product literature
Product literature requirements under NSF P473 are very similar to those under NSF/ANSI 53 for activated carbon systems and NSF/ANSI 58 for RO systems. Activated carbon systems must have installation, operation and maintenance instructions that meet the criteria included in NSF P473. These criteria are based on those in NSF/ANSI 53 and NSF/ANSI 58. The protocol also includes requirements for information included on system data plates, replacement element packaging and performance data sheets for activated carbon systems. RO systems are required by NSF P473 to include specific information in the installation, operation and maintenance instructions, as well as in the systems performance data sheet. The actual claim described under NSF P473 is PFOA/PFOS reduction. The protocol requires that the claim be described (per Table 2) on the performance data sheet of conforming POU treatment systems.
As US EPA issued the Health Advisory for PFOA and PFOS earlier in 2016 and the extent of the contamination of the drinking water supply became better understood, a need arose for an accepted test protocol to verify the capability of POU systems to treat drinking water for reduction of PFOA and PFOS. In response to this need, NSF leveraged already established testing protocols under NSF/ANSI 53 and NSF/ANSI 58 to quickly and scientifically adapt them and develop NSF P473. This new NSF P473 will allow manufacturers to establish consumer confidence for those end users seeking to treat their water for potential contamination and allow regulators to potentially direct those end users with concerns about PFOA and PFOS in drinking water to POU treatment systems that meet the requirements of NSF P473.
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