The role of permissible limits for hazardous airborne substances in the working environment in the prevention of occupational disease.

Recognized limits of permissible exposure to hazardous airborne substances adopted by different countries for industrial health protection may differ by a factor of 10. A Joint ILO/WHO Committee on Occupational Health in 1969 was unable to recommend a single set of values as international standards for more than a few toxic agents. The greatest differences are in the tolerance limits employed in the USA and in the USSR. The reasons for this substantial disagreement are discussed in this paper and are explained in terms of fundamental differences in the psychophysiological criteria employed to establish safe limits between the maintenance of good health and the development of a significant threat to the health. Some practical implications in the selection of permissible limits of exposure by developing countries are discussed in relation to living standards, endemic disease, climate, and geographical situation.