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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The authors present the concentration of the beginning growth inhibition (EC3) of Scenedesmus quadricauda accounting for 10 mg/L determined on the basis of the biomass (Bringmann, 1959). In this weight of evidence approach m-toluidine, the hydrolysis product of m-tolyl isocyanate, is considered as toxic towards algae.

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Additional information

Despite the study was scored as not reliable, it provides evidence for the concentration range, at which effects towards algae might be expected and thus can serve as basis for a weight of evidence approach. As normally the concentration causing 50 % inhibition is used for assessment, the EC3 is lower and would thus be more conservative if used for the assessment. Furthermore, effective concentrations determined on the basis of the biomass are generally lower than respective values based on the growth rate yielding a more conservative assessment as well. An additional algal test would not provide new evidence to assess the hazard of the hydrolysis product of m-tolyl isocyanate (m-toluidine) towards aquatic life.

Isocyanates are known to rapidly hydrolyse under the formation of the corresponding amine as well as solid polyurea compounds *. However, the insoluble inert polyurea is not assumed to cause environmental hazards due to the reduced uptake of high molecular mass compounds, whereas the amine is assumed to be the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of isocyanates assuming the complete transfer of the isocyanate into the corresponding amine while neglecting the formation of a certain fraction ecotoxicological not active polyurea compounds. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment. * Bayer Industry Services (2004). 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany. Bayer Industry Services (2003). Isopropylisocyante: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.