Hiệu ứng bất lợi y tế (s) có thể được coi là để trở về hai loại (xem Phần ): Những người coi để có một ngưỡng, được biết đến hiệu ứng As''threshold''(như vậy ảnh hưởng như, ví dụ như, cơ quan cụ thể, thần kinh, miễn dịch, không genotoxic gây ung thư, sinh sản, phát triển), và Những người nào có cho Được coi là để trở Một số rủi ro ở cấp nào, biết as''non-ngưỡng hiệu ứng''(như vậy ảnh hưởng như, ví dụ như đột biến, genotoxicity, genotoxic gây ung thư) . Mặc dù nó là không thể,. | 6 Standard Setting Non-Threshold Effects Carcinogenicity Adverse health effect s can be considered to be of two types see Section those considered to have a threshold known as threshold effects effects such as . organ-specific neurological immunological non-genotoxic carcinogenicity reproductive developmental and those for which there is considered to be some risk at any exposure level known as non-threshold effects effects such as . mutagenicity genotoxicity genotoxic carcinogenicity . Though it is not possible to demonstrate experimentally the presence or absence of a threshold differences in the approach to the hazard assessment of threshold effects versus non-threshold effects have been adopted widely. The distinction in approaches is based primarily on the premise that simple events such as in vitro activation and covalent binding may be linear over many orders of magnitude . that these events occur even at very low exposure levels. However a simple pragmatic distinction on this basis is increasingly problematic as it is likely that there is a threshold for a number of genotoxic effects. In the hazard assessment process described in detail in Chapter 4 all effects observed are evaluated in terms of the type and severity adverse or non-adverse their dose-response relationship and the relevance for humans of the effects observed in experimental animals. At present there is no clear consensus on an appropriate methodology for the hazard characterization of non-threshold effects. Cancer risks have traditionally been assessed by a quantitative extrapolation by mathematical modeling of the experimental dose-response data to estimate the risk at much lower human exposure levels . low-dose risk extrapolation. The outcome of low-dose extrapolation is the resulting lifetime cancer risk associated with estimated exposure for a particular population. It should be recognized that such low-dose risk estimation is uncertain. Owing to this uncertainty .
