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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). The read-across category justification document is attached in IUCLID section 13.


The toxicity of the substances of the MDI category to algae has been determined on the basis of current OECD 201 guideline studies on the three boucutendary/source substances and representative substances of the category. More specifically, the potential aquatic toxicity of the tested substances was determined from exposures to a water accommodated fraction (WAF), as recommended in the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD, 2019).Acute fish tests are available for the following substances of the category:


4,4-MDI, pMDI, mixed isomers MDI/PIR, 4,4-MDI/1,3-BG/TPG/PG, 4,4-MDI/DPG, and 4,4-MDI/DPG/HMWP


The data show that all LL50 and NOEL values obtained for all the tested substances of the category are greater than 100 mg/L.


An additional test with 4,4’-MDI/DPG/HMWP – monomer-depleted substance, from which the mMDI constituent was removed (by vacuum distillation) showed a 72-hour algae ErL50 value of greater than 100 mg/L.These studies have been supplemented by recently performed algal growth inhibition studies (according to guideline OECD 201) on the (transient) transformation compounds, i.e. 4,4’-MDI and 4,4’-MDA mono-ureas (Chapter 2.2.2) (Neuhahn et al, 2019). Both compounds did not show toxic effects against algae (ErL50/NOELr and EC50/NOEC values above 100 mg/L respectively).
Thus, the data support that MDI substances are not toxic to freshwater green algae. The available data are reliable and therefore adequate for classification and risk assessment purposes. Additional testing is not warranted.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

Values are expressed in Loading Rate (ErL50)

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