Just when we environmental old-timers were just getting used to talk about PFAS concentrations in the low parts per trillion range, EPA has moved us squarely into uncharted territory. EPA has released new, interim, lifetime drinking water health advisories of 4 parts per quadrillion for PFOA and 20 parts per quadrillion for PFOS. I’ll just note a couple of points: 
- I think it sort of charming that EPA still states the health advisories in the units of parts per trillion (0.004 ppt for PFOA and 0.020 ppt for PFOS,…