Achieving tap water with <0.06 ppb Chromium(VI) may be wasteful

Using the numbers from the EWG study, 0.06 parts per billion chromium(VI) may be a safe level for drinking water. To put this in perspective, the concentration of you, in the pool of roughly 6.9 billion people inhabiting this earth, is about 0.14 parts per billion.   A regulation that banned quantities of chromium(VI) above 0.06 ppb would ban infinitesimal quantities of chromium(IV) from our water supply.  While such a ban may be a good idea, ultimately the decision on how to regulate chromium(VI) should be based on a cost benefit analysis.  With that in mind, the cost of controlling chromium(VI) below 1 ppb based on currently available technologies could be enormous.   It may turn out that even though chromium(VI) cannot be considered safe above 0.06 ppb, it is just not practical or efficient to control such small quantities of chromium(VI) in the face of more imminent threats to our health.