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About Search. Enable Autosuggest. Previous Chapter. Regulatory Toxicology. In: Klaassen CD. Klaassen C. Curtis D. Accessed September 23, Download citation file: RIS Zotero.
Legal and Regulatory Toxicology
Reference Manager. Autosuggest Results. Expand All Sections. For relatively common types of disease, incidences are between 1 percent leukemia and 10 percent breast cancer in Swedish women. Once data are collected they are used to formulate toxicological assessments. Toxicological health assessments aim at identifying the potential adverse effects that a substance may cause in humans. This includes a description of the nature of these effects, their likelihood of occurrence, and their extent or severity.
The process of toxicological assessment is usually divided into four steps National Research Council , European Commission The first step of hazard identification aims at determining the inherent properties of a substance in order to identify the types of adverse effects to be included in further analysis. The second step is dose-response assessment. The purpose of the dose-response assessment is to describe the relationship between the size of the dose and the response in the exposed. This is essential, because a high dose of a substance with low toxicity can be lethal, while a very low dose of a substance with high toxicity may be harmless.
See Figure 1. The choice of a toxicological management strategy may depend on whether the dose-response relationship is considered to be linear from zero exposure or if a threshold dose is anticipated. A threshold dose is a dose under which no adverse effects are expected. A benchmark dose BMD is obtained by fitting a dose-response model to data, and from that model estimating a dose that corresponds to a predetermined change in the toxicological response investigated.
The low-level change in response compared to background associated with the BMD is commonly termed the benchmark response level BMR. Continuous dose-response data or incidence data may be used as a basis for these calculations.
In the latter case, the BMD is generally defined as a 1 percent to 10 percent change in the incidence of the effect compared to background. See Figure 2. Critical effect is the adverse effect that occurs at the lowest dose. The third step is exposure assessment.
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This aims at determining the likelihood of exposure and estimates the magnitude and duration of the doses, as well as the potential exposure routes. The final step is risk characterization, which involves comparing the exposure data to the dose-response information in order to characterize the risk in qualitative and if possible quantitative terms.
Conclusive dose-response data are rarely available in humans, and therefore risk characterization often involves extrapolation from animal data to assess human risk. Absent contrary evidence, it is generally presumed that the effects seen in the test species under experimental conditions are relevant to humans. This presumption is supported by the fact that common test species are physiologically similar to humans. In environmental risk assessment the same basic procedure applies. Extrapolation is made from experimental data a limited number of single species to the ecosystem millions of species and multiple exposures interacting.
Extrapolation of data is hampered by scientific uncertainty. The presumptions used to overcome gaps of knowledge in assessment involve value judgments.