There are any number of substances where there’s little doubt that they can cause cancer even at minuscule doses, just at similarly low rates. Get enough data a

There are any number of substances where there’s little doubt that they can cause cancer even at minuscule doses, just at similarly low rates. Get enough data and you will find that a single whiff of tobacco smoke (or any other smoke) can cause cancer. The “lowest dose linked to cancer” is the result of our ability to measure such effects, not anything intrinsic to the harm these substances do. That’s specific for cancer. For other forms of toxicity, the concept of “maximum safe dosage” does make sense when the dose/effect relationship is not linear. Pharmaceuticals, for example, can be entirely benign at small dosages yet lethal if you overdose.