Reference values and action levels of biological monitoring in occupational exposure

The primary objectives of biological monitoring are (1) to prevent health impairment, (2) to assist in the assessment of risk, and (3) to evaluate the effectiveness of environmental controls. An efficient way to achieve these objectives would be to enforce the compliance of biological exposure standards at the workplace. However, biological monitoring should be viewed in the total context of control and prevention of work-related diseases, and not merely to comply with permissible standards. Biological monitoring depends very much on the conditions that the chemical is absorbed and how it is metabolised. Genetic diversity could therefore contribute to significant differences in this aspect. Furthermore, many of the reference values established have so far not been fully validated and therefore their usefulness is rather limited. This paper reviews and illustrates using some recent findings to show that biological reference values are influenced not just by the above mentioned issues, but also factors such as (1) health and nutritional status of the exposed population, (2) social and cultural factors, and (3) climatic conditions. Caution has to be taken when considering having an action level for some of the biological reference value. Biological reference values set without considering people, technology, and working conditions would be fraught with difficulties in implementation.