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Emerging Contaminants

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What are Per- and Polyfluoralkyl 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 heat, oil, stains, and their nonstick characteristics. They are commonly used in products like cookware, waterproof clothing, furniture, and food packaging.  Due to their widespread use, most people have been exposed to PFAS. There is evidence that continued exposure above specific levels to certain PFAS may cause adverse health effects.  On April 10, 2024, EPA announced the final drinking water standards or Maximum Contaminant Levels (MCLs) to limit six PFAS compounds in drinking water.  An 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 cost feasibility.  

  • Perfluorooctanoic Acid (PFOA) – 4.0ppt
  • Perfluorooctane Sulfonate (PFOS) – 4.0ppt
  • GenX Chemicals – 10ppt
  • Perfluorononanoic acid (PFNA) – 10ppt
  • Perfluorohexane sulfonic acid (PFHxS) – 10ppt,
  • The rule also regulates mixtures of GenX chemicals, PFNA, PFHxS and Perfluorobutane sulfonic acid (PFBS) with a Hazard Index calculation to determine if the combined levels of these PFAS pose a potential risk to human health.

 

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 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).

 
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, EPA updated the  Health Advisory Levels for PFOA to 0.004 ppt and 0.02 ppt for PFOS.  EPA also issued final Health Advisory Levels of 10 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 consider 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.  It is important to note the updated Health Advisory Levels for PFOS and PFOA are below current reliable detection capabilities of existing testing equipment.

 

 
1,4-dioxane is a colorless, flammable liquid often used as a solvent or solvent stabilizer in the manufacture and processing of polyethylene terephthalate (PET), cotton, textile products, automotive coolant, cosmetics, shampoos, and other products. It mixes easily with water and degrades slowly.  The chemical is classified as a likely carcinogen.  

 

 
Bis(2-ethylhexyl) phthalate is a colorless viscous liquid that is soluble in oil, but not in water and used as a plasticizer in manufacturing of articles made of polyvinyl chloride (PVC).  EPA’s drinking water limit is 6 ppb.

 

 

Durham County Utilities is committed to complying with all regulations, remaining in compliance with the National Pollutant Discharge Elimination System (NPDES) Permit, and continuing to monitor all commercial and industrial users that discharge to the Triangle Wastewater Treatment Plant (TWWTP).