The investigation has been aimed at the genetically conditioned increased sensitivity to occupational hazards. Special attention should be paid to population's genetic differentiation at setting up hygienic standards and interpretation of results of biological absorption tests. As problems related to genetically conditioned increased sensitivity to hazards are particularly significant in the countries with the population's considerable biochemical differentiation or considerable rate of the so called biochemical deficits, therefore the problem gets more intense as more immigrants from Asiatic and African countries are employed in European industries. In the authors' opinion, correctly arranged pre-employment studies should reduce the number of poisonings in chemical industry.