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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Long-term terrestrial toxicity studies are available for a range of soil organisms for the read-across substance CAS 100545-48-0. In summary, no toxic effects to soil organisms could be attributed with certainty to the read-across substance.

Soil invertebrates

The chronic earthworm reproduction study was performed to OECD Guideline 222 methodology using nine concentrations of the read-across substance ranging from 0.1 to 1000 mg/kg dry soil (Bangert, 2017). All validity criteria were met. No effects were seen on earthworm survival. All concentrations showed inhibition of reproduction ranging from 5.7 % to 25.9 % compared to the control; however, due to the high variability in biological observations, the inhibition of juvenile production did not increase regularly. Therefore, a determination of an EC10 was not possible. Inhibition of juvenile production was less than 50 % in all treatments; therefore the EC50 is stated as being higher than the highest tested concentrations. The lowest concentration producing a significant effect (32 mg/kg nominal concentration) was chosen as the LOEC. The NOEC was set as the next lowest concentration (10 mg/kg), although in the absence of a clear dose-response relationship it is unclear whether the effects on reproduction were due to the test substance treatment. It is unlikely that toxic effects are seen at the limit of solubility of the test substance in soil porewater or that the substance is available for uptake by earthworms. The results of this study are used qualitatively in the hazard assessment.

 

Terrestrial Plants

The OECD Guideline 208 study was conducted to determine the effects of the read-across test substance on the seedling emergence and seedling growth of four dicotyledonous and two monocotyledonous species (Ripperger, 2018). No statistically significant differences could be determined for the parameter seedling emergence and post-emergence mortality.

Statistically significant effects on shoot dry weight could be detected forLolium perenneat 1.0, 10.7 and 23.4 mg test item/kg dw. The statistically significant difference to the control at 1.0 mg test item/kg dw was considered by the laboratory as not treatment-related, since the replicate values were still within the control range and no significant effects were detected at the higher concentrations of 2.2 and 4.84 mg test item/kg dw. The highest inhibition on shoot dry weight compared to the control was determined forAllium cepawith 34.8 % at 10.7 mg test item/kg dw. Shoot dry weight is a variable parameter and some degree of non-treatment related differences may be detected across the wide range of species and replicates. The laboratory suggests a LOEC of 1 mg/kg (13% difference from the control), but the test substance would be considered as "enhancing" the shoot weight as the mass is actually higher than the control. This is unlikely, but more likely due to natural biological variability. Even at 23.4 mg/kg there is essentially no effect, which attests to the variability of this biological parameter. The dose-response curve is very irregular for this species and parameter and the results are discussed qualitatively in the hazard assessment. It is concluded that toxicity in terrestrial plants following exposure to the read-across substance is unlikely.

Soil Microorganisms

The key study corresponding OECD 216 guideline was performed to GLP using the read-across substance (Chastenet, 2018). The rate of nitrate formation in treated samples compared with the rate in the controls, and the percent deviation of the treated from the control were calculated. No dose-response relationship could be observed and the EC10, EC50 values could not be calculated. No inhibitory effect was observed up to 401.6 mg test item/kg soil dry weight 28 days after application. The NOEC is therefore considered to be equal to or greater than 401.6 mg test item/kg soil dry weight. In compliance with guideline OECD 216, the study can be regarded to be valid, since the variation of nitrate-N content between replicate control samples was less than 15%. It is concluded that no toxicity was observed following exposure to the read-across substance CAS 100545 -48 -0.

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