“For toxicologists, “the dose makes the poison.” Any substance can be toxic in excess. Water, for instance, is lethal to humans in very high doses, and overhydration killed a runner in the 2002 Boston Marathon. But most people prefer to think of substances as either safe or dangerous, regardless of the dose. And we extend this thinking to exposure, in that we regard any exposure to chemicals, no matter how brief or limited, as harmful.”
