Parts Per Trillion (ppt)
The unit of measurement used for PFAS contamination levels, equivalent to one drop in 20 Olympic swimming pools.
Parts per trillion (ppt, or ng/L) is the standard measurement unit for PFAS in water. At these ultra-trace levels, advanced analytical methods like EPA Method 533 or 537.1 are required for detection. The EPA's health advisory for PFOA and PFOS has dropped from 70 ppt (2016) to 4 ppt (2024), reflecting growing understanding of health risks at extremely low concentrations.