Chemical risk assessment in toxicological perspective

Abstract

The discipline of toxicology is concerned with the health risks of human exposure to chemicals. According to the Paracelsus' paradigm toxicology is charged with describing the adverse effects of chemicals in a qualitative sense, and with evaluating them quantitatively by determining how much of a chemical is required to produce a substance specific. Taken together the intrinsic properties of an agent are described (hazard identification) and the amount of the chemical required to produce these (risk characterization) is determined. Since humans or organisms in the environment can be exposed via inhalation, skin contact or oral intake, the concentrations in the different environmental compartments, which result in human or environmental exposure, must be evaluated. Obviously risk characterization comprises the following elements: Hazard identification, i.e. a description of the agent's toxic potential. Dose-response, including information on the concentration above which the agent induces toxic effects to identify the no observable effect level (NOEL). Exposure assessment, in which the concentration of the agent in the relevant medium and time of exposure are evaluated. Based in this information difference between the NOEL and human exposure or the risk at a given exposure is determined. Humans may be exposed to chemicals in the air, water, food, or on the skin. From the concentrations of a chemical in these -different compartments the external daily exposure is estimated. The response to the chemical depends upon duration and route of exposure, the toxicokinetics of the chemical, the dose-response relationship and the susceptibility of the individual. Thus, the precise definition of the terms hazard, exposure, and risk is essential to understand toxicological evaluations (details on data requirements and procedures for risk assessment are given subsequently). Hazard: this qualitative term represents the intrinsic toxic properties of a -compound. The expression of hazard depends upon conditions of use and exposure. Dose: is determined by the concentration of the chemical and the time of exposure. Risk: is the likelihood of an adverse effect resulting from a given exposure. © 2010 Springer Science+Business Media B.V.