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A study was conducted in order to identify possible mutagic activities of EP-2 and was performed according to OECD guideline 471 and EU method B13/14.

In a preliminary toxicity test, Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 and Escherichia coli strain WP2uvrA were treated at EP-2 concentrations in the range of 0.15 - 5000 µg/plate to determine the dose range to be tested.

The same bacterial strains were treated with EP-2 in the presence and in the absence of metabolic activation (S9 -mix) both in the plate incorporation and in the pre-incubation assay with test concentrationsin the range of 5 - 5000 µg/plate and 0.5 - 5000 µg/plate, respectively. The tester strains without treatment or treated at the vehicle (acetone) alone served as negative controls and appropriate positive controls (with and withot S9 -mix) were examined in the same assays.

Results revealed counts of revertants in the normal range for vehicle control plates. All of the positive control chemicals used in the assays induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

In the first experiment (plate incorporation assay), EP-2 caused a visible reduction in the growth of the bacterial background lawn in all of the tester strains, both in the presence and absence of S9 -mix, initially at 500 µg/plate. In the second experiment (pre-incubation assay), EP-2 caused a visible reduction in the growth of the bacterial background lawn to all of the tester strains, with and without metabolic activation, initially at 150 µg/plate. Thus, EP-2 is cytotoxic at concentrations of 500 µg/plate and 150 µg/plate onwards in the plate incorporation assay and the pre-incubation assay, respectively.

No test item precipitate was observed on the plates at any concentration tested either in the presence or in the absence of metabolic activation.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of EP-2 either with or without metabolic activation or exposure method used. It is therefore concluded that EP-2 (O,O-diethyl phosphorochloridothioate) is

non-mutagenic under the conditions of this test.

In addition, in the IUCLID4 dataset on O,O-diethyl phosphorochloridothioate, the results of an AMES test in Salmonella typhimurium are presented and it is stated that the results indicated that the test was negative both in the presence and in the absence of metabolic activation. Thus, O,O-diethyl phosphorochloridothioate is not mutagenic in this in vitro assay.


Short description of key information:
An Ames-Test was performed on EP-2 (O,O-diethyl phosphorochloridothioate) accoring to OECD 471 and EU method B13/14. Results revealed that EP-2 is non-mutagenic both in the presence and in the absence of metabolic activation at either concentration tested in both the pre-incubation assay and plate incorporation assay. The test further showed that EP-2 is cytotoxic at concentrations of 500 µg/plate and 150 µg/plate onwards in the plate incorportation assay and the pre-incubation assay, respectively.

In addition, in the IUCLID4 dataset on O,O-diethyl phosphorochloridothioate, it is stated that the results of an AMES test in Salmonella typhimurium indicated that the test was negative both in the presence and in the absence of metabolic activation. Thus, O,O-diethyl phosphorochloridothioate is not mutagenic in this in vitro assay.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification