[Carcinogenic risk assessment of chemicals]

Assessment of human cancer risk associated with any particular specified chemical exposure required a complicated scientific procedure, starting with careful review of all pertinent information on the chemical, derived from experimental, epidemiological and clinical studies. It is generally agreed within the scientific community that there are four steps or components which are typically involved in carcinogenic risk assessment. The first step, which is referred to as hazard identification, entails a qualitative evaluation of data concerning the potential of the chemical to produce a carcinogenic effect in man. The second step, exposure assessment, is the process of measuring or estimating real or hypothetical human exposure to the chemical of interest. The third step, dose-response assessment, is the evaluation of both hazard and exposure information to estimate the mathematical probability that the carcinogenic potential associated with the agent in the human population under defined conditions of exposure. In the final step, referred to as risk characterization, all relevant information from the first three steps is integrated to characterize the carcinogenic risk associated with expected human exposure to the chemical of interest. The process of carcinogenic risk assessment, therefore, relies strongly upon the availability and quality of information on the chemical of interest. In conclusion, risk assessment is defined as a scientific procedure or logical frame-work to assess or infer the risk level of risk profile of the agent of interest in man on the basis of existing information. The execution of any given risk assessment, however, may be hampered by involvement of various uncertainties resulting from deficiencies or critical gaps in the necessary information on the chemical. On such occasions, it is necessary to make assumptions on the basis of the prevailing scientific thought concerning carcinogenic process, to take account of these uncertainties, so that risk assessment can still be completed. Therefore, risk assessment is regarded as a complex mixture of currently available data on the chemical of interest (Specific Information) and assumptions or inference rules based on the prevailing scientific thought on chemical carcinogenesis (General Information). From these points of view, the common ground for risk assessment can be divided into two categories. The first one is the issue of the specific information necessary for assessment, which includes the methodology of data production and the system of data distribution.(ABSTRACT TRUNCATED AT 400 WORDS)