Risk assessment of new and existing chemical substances

According to the Technical Guidance Document (TGD) for risk assessment of new and existing chemical substances (EC 2003), smdies conducted with human volunteers are strongly discouraged as they are problematic from an ethical point of view and results from such smdies should be used only in justified cases (e.g., tests which were conducted for the authorization of a medical product or when effects in already available human volunteer smdies with existing substances have been observed to be more severe than deduced from prior animal testing). However, the potential differences in sensitivity of human smdies and smdies in animals should be taken into account in the risk assessment, on a case-by-case basis. 

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