On January 16, 2019, European Food Safety Authority (EFSA) published a final document on ‘Genotoxicity assessment of chemical mixtures.’ The draft document, prepared by the EFSA Scientific Committee (SC), was published in June 2018 and subjected to a public consultation that closed in September 2018 (FPF reported).

As a first step, “a mixture should be chemically characterized as far as possible,” EFSA SC suggests. For a “fully defined chemical mixture,” the presence or absence of any substances known to be genotoxic in vivo would determine whether this mixture poses a genotoxicity concern or not, respectively.

For an incompletely defined mixture, the first option to be considered would be the “experimental testing of the unidentified fraction” in vitro. If this is not feasible, then the whole mixture should be tested. In the case of “clearly negative results” of in vitro testing, the mixture “does not raise concern for genotoxicity.” Positive in vitro result(s) should be followed up by an in vivo study.

If an in vivo study delivers negative results, then “the possible limitations of in vivo testing should be weighed in an uncertainty analysis before reaching a conclusion of no concern with respect to genotoxicity.” Positive in vivo results would lead to a conclusion that “the mixture does raise a concern about genotoxicity.”


EFSA (2019). “Genotoxicity assessment of chemical mixtures.EFSA Journal 17:e05519

EFSA (2019). “Outcome of the public consultation on the draft statement on genotoxicity assessment of chemical mixtures.EFSA Supporting Publications 16:1539E