ABSTRACT
Three types of biological indicators are used to assess exposure, effect and susceptibility. However, there are no clear distinctions between them. As a rule, biological media like blood and urine, alveolar air and tissue (hair and fingernails) or individual cells (e.g., skin or inner organs) may be used to measure a toxin concentration in potentially exposed individuals (Diabaté 2008; Vine 1994), and to study their reaction. Ideally, indicators would be applied that are capable of providing a reliable link between the concentration of a toxin in a specific compartment of the organism and a related health effect. It would be even better to have an indicator that helps to anticipate an undesirable physiological reaction or a disease, and that could differentiate between the toxic agent alone and related consequences from nutritional and physiological factors (sex and age), lifestyle (nutrition, hygiene, etc.), behaviour, and differences in individual susceptibility. This would be most helpful since these characteristics may lead to significant differences in individual resilience and physiological reaction. Unfortunately, no such indicator exists today, and all bio-assays and sophisticated cell tests are not yet capable of delivering such simple answers. Yet, biological indicators are still the best option to evaluate the health of a given population. The toxicokinetic properties of a toxin need to be known before selecting an appropriate indicator (c 2). To give a simple example, blood tests to assess arsenic are possible, but not very reliable, whereas urine tests present the method of choice.
