Public health scientist here. PhD in toxicology blah blah. Wasn't expecting to see this thread here. I spend a lot of time calculating risk from environmental toxicants, where risk is a function of toxicity times exposure. Toxicity is the probability of harm per unit of exposure. Exposure is a combined behavioral and physiological effect of duration, frequency, concentration, route, bioavailability, uptake, etc. The Prob 65 labels provide a slight clue to the consumer about toxicity, but says nothing about exposure. When I see a Prob 65 label, it is in theory a heads up to avoid unnecessary exposure. However, in practice, it doesn't really inform my personal or professional life.