Hydroquinone

Endpoint summary

Additional information

In accordance with the decision on substance evaluation pursuant to article 46(1) of Regulation (EC) No 1907/2006 for hydroquinone, a soil micro-organisms toxicity study has been performed according to the OECD TG 216 and under GLP. The 28d EC10 and EC50 were estimated at 19.5 and 60.1 mg hydroquinone/kg dry soil, respectively. The NOEC was determined as 10.0 mg hydroquinone/kg dry soil.

Concerning the other terrestrial endpoints, in accordance with column 2 of REACH Annexes IX and X, testing on toxicity to terrestrial organisms does not need to be conducted because of the following conclusions:

• During the manufacture, industrial uses, professional use and consumer use of hydroquinone, there is no intentional release of hydroquinone to the soil. Therefore, direct exposure of the soil compartment is unlikely.
• Indirect exposure of the soil compartment via sludge application to land is considered as very limited because hydroquinone is readily biodegradable and has a low adsorptive potential (log Koc = 50 L/kg).
• Indirect exposure of the soil compartment via aerial deposition is considered as very limited because hydroquinone has a very low volatility (Vapour pressure = 0.0032 Pa at 25°C and Henry’s Law constant = 4.7927 E-06 Pa-m³/mol at 25°C).
• Hydroquinone is not persistent and has a low potential to partition to soil. Therefore, it is not of particular concern for soil compartment.
• The chemical safety assessment performed with combined EU tonnage volumes and the equilibrium partitioning method results in RCR values for agricultural soil below 0.2. These results do not indicate the need to investigate further the effects to terrestrial organisms.
• Normally, micro-organism testing alone would not be considered sufficient for the derivation of the PNECsoil, but can be considered as part of a Weight-of-Evidence approach. If an assessment factor of 1000 is applied to the EC50 obtained in the soil micro-organisms toxicity study, a PNECsoil of 60.1 µg/kg soil (dw) is derived. This PNECsoil is higher than the PNEC derived by the Equilibrium partitioning method, i.e. 0.64 µg/kg soil (dw). Therefore there is no indication of risk from the available soil toxicity test.