Threshold values in toxicology - useful or not?

In many fields of toxicology, numbers are used as threshold values, e.g. as "acceptable daily intake values" resulting in maximum permissible concentr ations in food or in animal feed by using "safety factors"; maximal admissi ble concentrations of toxic substances in the air at the workplace; cut-off values in analytical toxicology; limit values for biological specimens in the case of driving under the influence of drugs, guidance values for envir onmental specimens, etc. The philosophy behind these values must be wc ll u nderstood and they should only be applied to real cases by persons with eno ugh toxicological background. The bad use of these numbers in toxicology ca n have dramatic consequences. Especially in regulatory toxicology their use should be made with great care, Moreover, tremendous improvements in analy tical methodology, e.g. the decreasing of the limits of detection for many potentially toxic substances in recent years, should not end up in an overe stimation of risks to humans. To avoid these abuses: careful interpretation s of analytical findings by qualified toxicologists are of paramount import ance. The use and abuse of some of these threshold values will be outlined in several applications from analytical toxicology, risk assessment issues, forensic toxicology in post-mortem cases, as well as from the drugs and dr iving cases. Generally, if threshold values are considered as guidance valu es and not as the "absolute truth" in toxicology, they may be very useful i n the interpretation of toxicology data. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.