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Sodium 2-biphenylate (CAS 132-27-4) is not stable at environmentally relevant conditions. On contact with water the substance dissociates forming NaOH and the conjugate acid 2-phenylphenol (CAS 90-43-7). The determined dissociation constant (pKa) of 2-phenylphenol (CAS 90-43-7) is 9.5. Thus a dissociation of sodium 2-biphenylate and formation of 2-phenylphenol at environmental relevant pH of 5 - 9 can be expected. Dissociation is the main degradation pathway for sodium 2-biphenylate. Sodium 2-biphenylate will most probably not exist in the environment and thus persistency of the target substance can be excluded. The degradation of the conjugate acid 2-phenylphenol was tested in a study following OECD 301B. Ready biodegradability was demonstrated for 2-phenylphenol. Based on the CO2evolution a biodegradation rate of 70.8 – 75.7% was determined (test substance concentration 0.2 mg/L and 1 mg/L, respectively). A rapid degradation in sewage treatment plants (STP) can be expected and the amount of substance released by STP effluent is presumably negligible.

The experimentally determined water solubility ofSodium 2-biphenylate is > 1000 g/L at pH 13.6 and 20 °C. However, as indicated above the substance will dissociate on contact with water. At environmental relevant pH the uncharged form 2-phenylphenol prevails. The measured water solubility range of 2-phenylphenol at pH 5-9 was 0.53 – 0.64 mg/L (at 20 °C). Due to the relatively low water solubility in combination with the rapid biodegradation an accumulation in natural water bodies can be excluded. Sodium 2-biphenylate and 2-phenylphenol have a low adsorption potential. A Koc of 529.3 L/kg for sodium 2-biphenylate was estimated by calculation based on the experimentally determined log Pow of 2.95. A comparable adsorption coefficient of 347 L/kg was determined in an experimental study on 2-phenylphenol. The determined Koc values indicate a moderate mobility in soil. Furthermore, an accumulation in air and the subsequent transport to other environmental compartments is not anticipated due to the low vapour pressure of Sodium 2-biphenylate as well as2-phenylphenol (VP: 1.2 Pa and 0.906 Pa at 20 °C, respectively).

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