The European Food Safety Authority (EFSA) and the World Health Organization (WHO), with the support of the International Life Sciences Institute, European Branch (ILSI Europe), organized an international conference on 16-18 November 2005 to discuss how regulatory and advisory bodies evaluate the potential risks of the presence in food of substances that are both genotoxic and carcinogenic. The objectives of the conference were to discuss the possible approaches for risk assessment of such substances, how the approaches may be interpreted and whether they meet the needs of risk managers. ALARA (as low as reasonably achievable) provides advice based solely on hazard identification and does not take into account either potency or human exposure. The use of quantitative low-dose extrapolation of dose-response data from an animal bioassay raises numerous scientific uncertainties related to the selection of mathematical models and extrapolation down to levels of human exposure. There was consensus that the margin of exposure (MOE) was the preferred approach because it is based on the available animal dose-response data, without extrapolation, and on human exposures. The MOE can be used for prioritisation of risk management actions but the conference recognised that it is difficult to interpret it in terms of health risk.

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Cyclic volatile methyl siloxanes (cVMSs) are highly volatile and have an unusual combination of physicochemical properties, which are unlike those of halocarbon-based chemicals used to establish criteria for identification of persistent organic pollutants (POPs) that undergo long-range transport (LRT). A transparent quantitative weight of evidence (QWoE) evaluation was conducted to characterize their properties. Measurements of concentrations of cVMSs in the environment are challenging, but currently, concentrations measured in robust studies are all less than thresholds of toxicity. The cVMSs are moderately persistent in air with half-lives ≤11 d (greater than the criterion of 2 d) but these compounds partition into the atmosphere, the final sink. The cVMSs are rapidly degraded in dry soils, partition from wet soils into the atmosphere, and are not classifiable as persistent in soils. Persistence in water and sediment is variable, but the greatest concentrations in the environment are observed in sediments. Based upon the measurements that have been made in the environment, cVMSs should not be classified as persistent. Studies in food webs support a conclusion that the cVMSs do not biomagnify, a conclusion that is consistent with results of toxicokinetic studies. Concentrations in air in remote locations are small and deposition has not been detected. Taken together, evidence indicates that traditional measures of persistence and biomagnification used for legacy POP are not suitable for cVMS. Refined approaches used here suggest that cVMSs are not classifiable as persistent, bioaccumulative, or toxic. Further, these chemicals do not undergo LRT in the sense of legacy POPs.

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