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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

No toxicity observed in a short-term study (OECD 202) with Daphnia magna at loadings up to 1000 mg/L. In this study the test substance was stirred in water in the usual way (1000 rpm) prior to exposure to the daphnids.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
1 000 mg/L

Additional information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). Hence, data of the category substances can be used to cover this endpoint. Although 3 aquatic invertebrate studies are available, two of them are considered unreliable. These unreliable tests (Rhone-Poulenc, 1977) were done with 4,4'-MDI, as they mainly tested the hydrolysis product, 4,4'-MDA. In both studies acute toxicity values were found to be greater than 500 mg/L for Daphnia magna and Limnea stagnalis, respectively.

The study of Caspers et al (1986) was performed with polymeric MDI and contained two different experiments, following the OECD 202 protocol. In one experiment, PMDI was dispersed into water by high speed shearing (24,000 rpm) instead of the usual stirring (magnetic, 1000 rpm). This gave a 24h-EC50 of 129.7 mg/L, which was almost certainly due to the significantly increased production of 4,4'-methylenedianiline (MDA), a substance which is known to be relatively toxic to daphnids. It may be considered that the 24h-EC50 of 129.7 mg/L is irrelevant because the dispersing method used in this one experiment does not reflect a situation that might occur in the real environment. The second experiment used the normal stirring (1000 rpm) and gave a 24h-EC50 > 1000 mg/L. The result of the short-term toxicity test (24h-EC50 >1000 mg/L) (Caspers et al, 1986) was corroborated with the long-term mecocosm studies (Heimbach, 1993), where no effects were seen on zooplankton at loadings up to 10,000 mg/L. Although only a 24h value for aquatic invertebrates is available, this value is considered to be conclusive enough for this endpoint. Due to the rapid reaction with water (hydrolysis T1/2 = 20 days), any attempt to determine the aquatic toxicity, will be influenced by the toxicity of the hydrolysis products.