Exposure and effect monitoring: a critical appraisal of their practical application

The prerequisite for the use of biomarkers of exposure as indicators of health risk is that the relationship between the biomarker and the health effects and the representation in time of the biomarker level are known. Some exposure biomarkers may be applied for the quantitative assessment of the amount of exposure. In this task, the half-time of the parameter measured is crucial, since it determines what length of time of exposure the result reflects. For reliable assessment of the exposure the species (e.g. metal, oxide or salt) has to be known. For some chemicals the estimation of exposure from biomonitoring is based on several studies with uniform results and is quite reliable, while for others the uncertainty is wide. Exposure biomarkers have been successfully used in the identification of exposed individuals and follow-up of exposure. For example, macromolecule adducts and mutagenicity in urine have been successfully applied to the identification of workers exposed to carcinogens and as indicators of changes of exposure. Biomarkers of renal effects of cadmium, lead effects on haemoglobin synthesis and organophosphate effects on cholinesterase activities have been well validated and are widely used in routine monitoring activities. However, effect markers for lead and cadmium offer little advantage over the analysis of the chemical itself and where accurate metal analysis is readily available, they have a limited use today. For the analysis of chromosomal aberrations, limited data are available suggesting that elevated frequencies may indicate a carcinogenic risk. In several instances, genotoxic effect monitoring has been used to identify groups of people exposed to hazardous chemicals and in the follow-up of improvements in industrial hygiene.