Biological exposure and/or effect limits, facts, fallacies and uncertainties: general principles.

When looking for facts, fallacies and uncertainties of the use of biological exposure limits one has at first to discuss the general principles of biological monitoring (BM) and biological effect monitoring (BEM) because they determine the validity of the data that underpin the biological exposure limits. A difference between countries in preferred BM-methods can be observed. The terminology is still confusing: in addition to BM and BEM, biomonitoring and biological markers also are used. There are a number of problems in respect of the inter- and intra-individual variability in internal exposure and effect at similar exposure levels due to differences in for example, physical workload, body composition and genetics. Toxicokinetic models based on data from individual workers should be developed in order to get information on the variability and the cause of this. Both kinetics and dynamics may be sex-dependent. To date, BM methods have been tentatively suggested for only about 10 per cent of the regulated industrial chemicals. BM and BEM programmes yield important extra information on exposure and health risk, not to be gained by environmental monitoring alone.