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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50(96h): 4300 mg/L; NOEC(96h): 1000 mg/L (Chlorella vulgaris, freshwater, OECD 201) 
EC50(96h): 3230 mg/L (Skeletonema costatum, marine water, OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:
4 300 mg/L
EC50 for marine water algae:
3 230 mg/L
EC10 or NOEC for freshwater algae:
1 000 mg/L

Additional information

Acute toxicity test towards freshwater as well as marine water algae were investigated according to OECD Guideline 201 for the read-across substance m-tolylidene diisocyanate (both key studies). Furthermore, a QSAR prediction was performed for green algae as supporting information.

The freshwater algae Chlorella vulgaris was investigated for a test duration of 96 hours (Tadokoro, 1997). 15g/L of T-80 was added to alga medium and the medium was stirred for 24 hours. The solution was allowed to settle for 1 hour. The stock solution was diluted to desired concentrations. The nominal concentration range was 938 mg/L - 15000 mg/L. An initial cell number of 1x10E7 cells/mL was used and the temperature was held constant at 20 °C. At a test concentration of 1 g/L, only 2.8 % biomass inhibition was observed. This value can be considered as the No Observed Effect Concentration (NOEC; EC2.8). The EC50 was determined as 4300 mg/L, whereby the rapid hydrolysis rate of the test substance was taken into account.

The same test conditions were applied to the marine algae species Skeletonema costatum (Tadokoro, 1997). 10g/L of T-80 was added to enriched sea water medium and the medium was stirred for 24 hours. The solution was allowed to settle for 1 hour and filtered with no. 5C filter paper and 0.22 µm millipore filter to remove undissolved component and to sterilize the medium. Then the stock solution was diluted to desired concentration with sterilized enriched seawater to prepare test solutions (highest concentration was 5000 mg/L with 5 others diluted by a factor of 1.8). The initial number of cells was 10E3 cells/mL and the test temperature 20 °C. The EC50 was determined as 3230 mg/L, taken the rapid hydrolysis rate of the substance into consideration.

The prediction for long-term toxicity for aquatic organisms of the substance 2,4,6 -triisopropyl-m-phenylene diisocyanate was determined by the computer program ECOSAR v1.00 (EPIWIN software) by US-EPA (Chemservice S.A., 2011). The program uses an extensive set of structure-activity relationships (SARs) to estimate the toxicity of chemicals discharged to water. For green algae a Chronic Value (ChV) of 0.021 mg/L was predicted. No GLP criteria are applicable for the usage of this tool, but due to the fact that it is a scientifically accepted calculation method the estimations performed are reliable with restrictions and can be used for the chemical safety assessment.