Non-Monotonic Dose Responses

NON-MONOTONICTypical dose responses in toxicology studies are monotonic, meaning that as the dose increases, so does the effect. Non-monotonic dose responses (NMDRs) go against predictable or typical dose-response patterns where the dose-response curve changes direction within the range of doses examined. “U” and inverted “U” shapes are non-monotonic curves.

While NMDRs can theoretically occur, and some have been observed with crop protection products, the biological significance with respect to adverse effects has not been established. It is likely that such observations simply reflect natural variation in responses within the test system or the living beings examined. Moreover, studies claiming NMDRs often suffer from methodological shortcomings, have not been reproduced consistently between different laboratories and have questionable results due to lack of toxicological significance.

Current data requirements for crop protection products include a sufficient range of dose levels and parameters to characterize potential risk to human health and the environment as well as to account for possible NMDRs. Therefore, changes in testing for them are not required.

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