6,8-Dioxabicyclo[3.2.1]octan-4-one, (1S,5R)-

Endpoint summary

Additional information

No terrestrial toxicity data are available with the registered substance. 

In accordance with Column 2 of REACH Annex X, there is no need to further investigate the effects of Cyrene™ in a short- or long-term terrestrial toxicity to invertebrates/higher plants study because, as indicated in guidance R.7.11.6 (ECHA 2017), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio is well below 1 and therefore the risk is already adequately controlled and further testing is not justifiable.

If Cyrene™ is released to water, the relevant form of the substance under dilute environmental conditions, is the Gem Diol (please refer to IUCLID Section 4, CSR Section 1.4 and the attached report in Section 13 of IUCLID for further discussion on formation of the Gem Diol). Due to water and moisture being present in soil, the Gem Diol is the relevant form for the terrestrial compartment.

Cyrene™ is highly water soluble (measured water solubility of ≥560 g/l; this value is applicable to both the Cyrene™ and Gem Diol forms). Both Cyrene™ and its Gem Diol form have low potential for bioaccumulation and low potential for adsorption based on log K_ow <3 (-1.52, measured; this value is applicable to both the Cyrene™ and Gem Diol forms) and low log K_oc (0.23, calculated based on the log K_ow)) and are readily biodegradable (measured data). No toxicity was observed in short-term aquatic toxicity tests. Long-term toxicity data predicted by QSAR estimates that effects would only occur at extremely high concentrations, well in excess of the highest test concentrations required by the relevant OECD test guidelines, and well in excess of environmentally relevant concentrations.

There is no reason to expect any specific mechanism of toxicity beyond narcosis. Therefore, the occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies would be considered unlikely. In addition, the binding behaviour of the Gem Diol is not triggered by any other mechanisms, for example it is not an ionising or surface active substance, nor a substance that will bind chemically with soil components. The aquatic compartment is therefore the most relevant and aquatic toxicity data are available.

Cyrene™ and its Gem Diol form are classed as Hazard Category 1 for the terrestrial environment (Table R.7.11-2 of ECHA guidance R7.c, 2017) based on there being no indication for high adsorption or high persistence of the substance in soil (the substance is readily biodegradable) and no indication that the substance is very toxic to aquatic organisms (EC/LC₅₀ not <1 mg/l).

 

In this situation, the approach for screening assessment is to conduct a PEC/PNEC screen based on the equilibrium partitioning method. If the PEC/PNECscreen is <1, no toxicity testing for soil organisms needs to be conducted. The PNECscreen(EQPM) for the Gem Diol is derived from the algal NOEC, generating a PNECsoil value of 16 mg/kg dwt.  Based on the exposure assessment of the registered substance, the highest PEC/PNECscreen(EQPM) for the Gem Diol is 9.36E-3.

 

Overall, it is concluded that the risk characterisation conclusion is sufficiently conservative and therefore further testing is not considered necessary.

In addition, there is very little difference in the properties of the registered substance (Cyrene™) and the Gem Diol form, therefore the assessment would not differ between the two forms.

 

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 7, 9 and 10 of the Chemical Safety Report.

 

References

ECHA (2017). Guidance on Information Requirements and Chemical Safety Assessment. Chapter R.7c: Endpoint specific guidance. Version 3.0 June 2017.