Paracelsus And PFAS

A half a millennium ago the Renaissance Physician Philosopher Parcelsus wrote "only the dose makes the poison."  Modern day Government Risk Assessors apply Paracelsus's wisdom to the contamination of soil and water by determining the largest dose of a chemical at which no adverse effect on humans or other organisms is observed.  That "dose" is usually measured in parts per billion which is roughly equivalent to a drop of water in a swimming pool.  All of this risk assessing takes time.  In the meantime confusion and outright panic can reign.

Which brings us to PFAS, a family of dozens of chemicals which we are coming to learn have been used in a wide range of products.  Over the past few years we've developed the ability  to detect PFAS in parts per trillion.  We're finding they are more ubiquitous in the environment than we would have hoped, albeit usually at infinitesimally small concentrations.