[Pathology caused by microdoses of chemical substances].

Improvement in environmental conditions in industry is producing a progressive reduction in the dose of absorbed substances. This has repercussions on the work of the occupational health physician, who now has to face a new set of problems, problems which at the same time offer occasions for further research in risk assessment of chemical agents. The most obvious finding, which has perhaps been handled more systematically, concerns the change in occupational diseases, whence the need to extend designs and protocols of health surveillance. The expected effects of occupational exposure to low doses of a chemical fall within the category of what may be defined as long-term effects, carcinogenic effects and, above all, effects involving systems or apparatuses that are sensitive to low doses but over long periods, such as, for example, the immune and the reproductive systems. This new situation than has repercussions on biological monitoring: in the first place on the problem of setting reference values and on the study and control of confounding factors; secondly, on the predictivity of the biological indicators used. In some cases, in fact, the indicators of dose that the occupational health physician has learnt to use and on which his approach to prevention his based, proved to be no longer predictive in such new exposure situations.