[Toxicological significance of biological markers]. / Significato tossicologico degli indicatori biologici.

ABSTRACT

Biological monitoring or, simply, biomonitoring (BM), refers to the periodic measurement of biological markers, or biomarkers (BMKs), in human fluids and tissues to assess the interaction (absorption, early health effects, susceptibility) between physical, chemical or biological agents and the human organism. The primary aim of BM in the workplace is to integrate environmental monitoring data and detect early, reversible biochemical or functional changes in workers exposed to chemicals before they become clinically relevant. BM also contributes to the assessment of chemical risk to workers, as individuals or as a group. Biomarkers are generally divided into three main types biomarkers of exposure (BME), response/effect (BMR), and susceptibility (BMS). Other, more specific types of biomarkers are those of internal dose (BID), those of biologically effective dose (BED) and early biomarkers of disease (EBD). It is not always easy, however, to allocate a given BMK--such as the measurement of cytochrome P450 phenotype in subjects exposed to organic solvents--to one or the other type. Biomonitoring provides several advantages over environmental monitoring or health surveillance. For example, it allows an estimate of inter- and intra-individual variability in the absorption, distribution and excretion of chemicals. It also allows the detection of reversible changes before the appearance of a clinically relevant occupational impairment or disease. For these reasons, BM has become a routine procedure in occupational health practice throughout the world. Even the widely acknowledged, recently updated Code of Ethics for Occupational Health Professionals, a milestone in occupational health practice, only provides the basic ethical principles associated with biological monitoring. The aim of the present paper is to survey the various types of BMK available today with two main objectives: to discuss their toxicological significance and highlight the substantial differences that exist between their use in the practice of occupational health and in medical research. The development of new, more valid and reliable BMKs is strongly dependent on the understanding not only of the toxicokinetic and toxicodinamic mechanisms of chemicals, but also of the various susceptibility factors involved, whether genetic or environmental. It is hoped that the concurrent use of BMKs of different types may improve chemical risk assessment in workers, both individually and as a group.