What chemicals are toxic?
All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy. This founding principle of toxicology from Paracelcus (1493-1541 CE) is a useful point with which to begin. For any chemical or drug, there are low doses for which there are no effects, higher doses where the desired effects (for a drug) outweigh the toxic side effects, and toxic doses where the toxic side effects outweigh the therapeutic effects. These doses that define the low limits of the toxic effects are not absolute; they are different for every person. For example, alcohol has little effect at low doses, and has what some describe as therapeutic doses in the middle. But alcohol can be fatal at high doses. People of Asian descent are genetically less able to metabolize alcohol, and they suffer the toxic effects at markedly lower amounts than persons of European descent. In that sense, Asians would be described as sensitive and Europeans as resistant. The point is
