Perfluorinated Chemicals Data and Information

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Per- and Polyfluoroalkyl Substances (PFAS) Heath Advisory Levels and Maximum Contaminant Levels Additional Information

Per- and Polyfluoroalkyl Substances (PFAS)

PFAS are synthetic chemicals that have been manufactured and used by a broad range of industries since the 1940s. PFAS are used in many applications because of their unique physical properties such as resistance to high and low temperatures, resistance to degradation, and nonstick characteristics. They are commonly used in products like food packaging, dental floss, carpeting, water proof clothing and cookware.  PFAS have been detected worldwide in the air, soil, and water.

Due to their widespread use and persistence in the environment, most people in the United States have been exposed to PFAS. There is now evidence that continued exposure above specific levels to certain PFAS may cause adverse health effects.  In response, the EPA developed health advisory levels for the following PFAS compounds: Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS), Perfluorobutane Sulfonic Acid (PFBS) and GenX.  The EPA also issued draft Maximum Contaminant Levels on March 14, 2023 for PFOS and PFOA compounds.

Heath Advisory Levels and Maximum Contaminant Levels

PFAS timeline

What is a Health Advisory Level?

A health advisory level is one of the first steps in developing new drinking water standards and are not enforceable regulations. Instead, health advisory levels represent guidance provided by the EPA until formal regulations are established. A health advisory level is the minimum concentration of a compound which may present health risks to an individual over a lifetime of exposure (drinking 2.5 liters of water per day for 70 years). 

What do the Health Advisory Levels for GenX, PFOA and PFOS Mean?

The EPA first issued interim health advisory levels for PFOA and PFOS in 2016 at 70 parts per trillion (ppt) and GenX for 140 parts per trillion (ppt).  On June 15, 2022, the EPA updated the  Health Advisory Levels for PFOA to 0.004 ppt and 0.02 ppt for PFOS.  The EPA also issued final Health Advisory Levels of 10 parts ppt for GenX and 2,000 ppt for PFBS.  EPA’s lifetime health advisories identify levels to protect all people, including sensitive populations and life stages, from adverse health effects resulting from a lifetime of exposure to these PFAS in drinking water. They also take into account other potential sources of exposure to these PFAS from food, air and consumer products. In this calculation water is assumed to account for 20% of all exposure sources.  The updated Health Advisory Levels for PFOS and PFOA are also well below current reliable detection capabilities of existing testing equipment.

What is a Maximum Contaminant Level?

A Maximum Contaminant Level (or MCL) is the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to Health Advisory Levels as feasible using the best available treatment technology, approved EPA test methods and taking cost into consideration.  

On April 10, 2024, the EPA finalized MCLs for six PFAS including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS).  The MCLs for PFOA and PFOS are 4 ppt, which is the level that can be reliably measured.  The EPA also placed limits on any mixture containing one or more of PFNA, PFHxS, PFBS, and/or GenX Chemicals. For these PFAS, water systems would use a hazard index calculation to determine if the combined levels of these PFAS pose a potential risk (calculation should be below “1.0”).  Concentrations of these compounds in Raleigh’s drinking water have usually ranged from non-detectable to 4 ppt (PFOA) and non-detectable to 5.5 ppt (PFOS) and from non-detectable to 3.5 ppt (PFBS).  The hazard index calculation for Raleigh's drinking water is 0.0017

What is Raleigh Water Doing About This Issue?

Raleigh Water is committed to complying with all PFAS regulations and will continue to work with our industry partners and regulatory agencies to ensure our drinking water is safe.  We have been monitoring for the presence of PFAS since 2013, and have updated our data based on the most recent EPA approved test methods:

2022 Lab Results With Approved EPA Test Methods

2023 Lab Results With Approved EPA Test Methods

Archived Lab Results With Eurofins Test Methods

* Results are in units of nanograms per liter (ng/l), which is equivalent to parts per trillion (ppt)

Since low levels of PFAS are common throughout the environment, we share the same challenge as many other drinking water utilities throughout the United States.   In response, Raleigh Water staff have been optimizing our current treatment systems to improve PFAS removal and we are also evaluating new treatment technologies for potential installation in the future.  We will also look to better understand possible upstream sources of PFAS in our water supply watersheds through continued sampling and will work to limit these sources whenever possible. 



Edward Buchan


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Water TreatmentResource Recovery