A review paper by Olwenn Martin and colleagues published on July 1, 2013 in Environmental Health assesses the historical development of default uncertainty factors and questions their adequacy for assessing the safety of exposure to single substances and mixture of chemicals. The authors demonstrate that currently employed uncertainty factors in chemical risk assessment do not represent worst-case scenarios, but at best adequate scenarios for exposures to single chemicals. In addition, variability within the human population remains largely unquantified and neither the challenges posed by the lack of statistical power in animal experiments, nor mixture effects are sufficiently addressed.

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FPF report “Uncertainty factors in chemical risk assessment