It is food safety policy worldwide not to accept genotoxic carcinogenic compounds in food and feed. Consequently such chemicals will not be authorized as a food additive, a veterinary drug, or pesticide. In this regard the EU is however more strict than many non-EU countries in the Codex Alimentarius. It can be discussed that promoting carcinogens demonstrate safe levels through its treshold mechanism of action, and consequently a HBGV can be evaluated on the basis of the treshold value, e.g. a NOAEL and safety factors. In these cases also MRLs can be established.
As genotoxic carcinogens are not allowed in the EU, it seems at first sight not necessary to know how to evaluate their cancer risks (in an EU situation). On should be aware however that some contaminants and toxins are classified as genotoxic carcinogens, e.g. some aflatoxins. So a risk assessment procedure is needed to evaluate the risk of these chemicals in food or feed. That procedure differs from the approach where safe levels are derived from a treshold level.
The commonly used method to evaluate the health risk of a genotoxic carcinogen is based on the linear extrapolation of the lowest effect dose inducing tumours and the zero dose without effect. As it is assumed that one molecule of the chemical can activate the effect, more molecules will increase the risk accordingly. Using the linear relationship between dose and effect the health risk for a given dose level can be calculated. It should be noted that this a very conservative assumption, as it is known that molecular repair mechanisms and biochemical reactions will lower the factual risk. So, the method of linear extrapolation leads to an extremely conservative estimation of tumour promotion. But as the ALARA principle is the political background for the assessment of genotoxic carcinogens both in the EU and Codex Alimentarius, this worst case approach is globally supported.