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Ecotoxicological information

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The solubility of biphenyl-4,4'-diol in water is relatively low: 33.7 mg/L at pH 6.5 and 20 degrees C. The calculated logarithm of the n-octanol/water partition coefficient (log Kow) of biphenyl-4,4'-diol is 2.7, which lies below the bioconcentration trigger of 3.0 and indicates that biphenyl-4,4'-diol is unlikely to bioconcentrate to a significant extent in the tissues of aquatic biota from contaminated water. Measured adsorption coefficients ranging from 79 to 200 kg/L in soil and STP sludge are consistent with the relatively low calculated log Kow, in addition they also indicate that biphenyl-4,4'-diol in surface water is unlikely to partition preferentially to organic matter in sediments.

None of the uses of biphenyl-4,4'-diol involve direct application to surface water. The potential for unintended exposure of the aquatic compartment is therefore confined to biphenyl-4,4'-residues contained in treatment plant effluents discharged to surface waters.

A set of reliable (Klimisch 1) studies performed in accordance with relevant test guidelines and in accordance with the Principles of GLP addresses the aquatic toxicity of biphenyl-4,4'-diol. In these four studies (all conducted on behalf of the Ministry of the Environment of the Government of Japan), the following endpoints were obtained for aquatic organisms exposed to high purity (99.96% w/w) biphenyl-4,4'-diol:

Acute fish (O. latipes) 96 hour mortality LC50 (semi-static) = 12.8 mg/L (95% CI 9.58 to 17.0 mg/L), geometric mean measured.

Acute invertebrate (D. magna) 48 hour immobilisation EC50 (semi-static) = 1.76 mg/L (95% CI 1.47 to 2.11 mg/L), geometric mean measured.

Long-term invertebrate (D. magna) 21 day reproduction (semi-static) NOEC = 0.108 mg/L and EC50 = 0.390 mg/L (95% CI 0.350 to 0.437 mg/L), TWA measured. 21 day mortality LC50 = 1.30 mg/L (95% CI 0.792 to 2.15 mg/L), TWA measured.

Algal inhibition assay (P. subcapitata) 72 hour ErC50 (static) = 7.73 mg/L (95% CI not calculated), measured initial.

In a guideline- and GLP-compliant study of the toxicity of biphenyl-4,4'-diol to aquatic microorganisms associated with aerobic waste-water treatment processes, the three-hour EC50 based on inhibition of respiration of activated sludge, was >1000 mg/L, nominal, the highest concentration tested.