Zero exposure--a goal for environmental and occupational health?

Humans live on chemicals, and no exposure to any chemicals is incompatible with life. Chemicals produced by different organisms are in no basic way different from the man-made chemicals, and often chemicals are produced by both. Natural chemicals include the most potent acutely toxic chemicals known, and also include very potent mutagens and human carcinogens. Thus the fact that a chemical is 'natural' does not mean that it is any safer than a man-made chemical, and the fact that a chemical is man-made does not make it any more harmful than 'natural' chemicals. Exposure to chemicals varies widely, to a large variety of chemicals people are exposed from the environment, via drinking water, food and inhaled air and exposure e.g. at the work-place is only quantitatively different from the exposure of the general public. Zero exposure is meaningless without an operational definition. It is a major challenge to the society to determine what is the safe exposure level to different chemicals, and for chemicals for which no exposure level is safe, to define the acceptable risk, and in both cases, make sure that the exposure limits thus determined are complied with.