p-(trifluoromethoxy)phenyl isocyanate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

OCT 2019 - AUG 2020

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

For the registered substance 4-trifluoromethoxy phenyl isocyanate (CAS No. 35037-73-1), the water
molecules will react with free isocyanate groups to generate carbon dioxide and primary amines
which forms 4-trifluoromethoxy aniline (CAS No. 461-82-5), that is a hydrolysis product of 4-
trifluoromethoxy phenyl isocyanate. Thus, in this endpoint the hydrolysis product is tested. For details of hydrolysis process please refer to section 13 "expert statement".

Analytical monitoring:

yes

Details on sampling:

A stock solution was prepared to give the desired series of test concentrations. 100.9 mg of the test item were added to a 1 litre portion of dilution water and stirred for 0.5 h on a magnetic stirrer. The solution was apparently solved and was clear without visible particles (no Tyndall-effect was observed). The pH was measured to be 7.8.

Vehicle:

no

Details on test solutions:

To produce the different test item concentrations appropriate amounts of the stock solution were diluted with dilution water to a volume of 500 mL. 50 mL of the prepared solutions were taken per replicate and 0.5 mL of dilution water containing 5 daphnids was given to all replicates resulting in the final nominal concentrations. For each test item exposure concentration and for the control exposure 4 replicates were prepared.

Test organisms (species):

Daphnia magna

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

14.4 °dH (= 257 mg/L CaCO3)

Test temperature:

18 - 22 °C

Details on test conditions:

The main test was conducted as a static test with the test medium unchanged throughout the duration of the test.

During the test a temperature range of 18 - 22 °C was maintained in the test vessels, with a maximum temperature fluctuation of +/- 1 °C in each individual test.

The temperature, the pH and the oxygen values were measured at the beginning and end of the test. In order to avoid any potential impairment of the test system, an additional replicate was used at the beginning of the test. Measurements at the end of the test were performed using replicate 1 of the test concentrations and the control vessels.

Reference substance (positive control):

yes

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

7.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.67 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Conclusions:

The EC50 after 24 h was 7.3 mg/L. The EC50 after 48 h was 0.67 mg/L.

Executive summary:

The short-term toxicity of 4-trifluoromethoxyaniline towards aquatic invertebrates was tested according to OECD Guideline 202 and under GLP. The daphnids (Daphnia magna) were exposed to a range of concentrations, nominally 0.018, 0.040, 0.088, 0.19, 0.43, 0.94, 2.1, 4.5 and 10 mg/L of 4-trifluoromethoxyaniline dissolved in dilution water. Auxiliaries used to prepare the test media was an magnetic stirrer.

Observations were made on the swimming ability and the percentage immobilised, respectively, after 24 and 48 hours of exposure. The following values were determined: EC50 (24h): 7.3 mg/L and EC50 (48h): 0.67 mg/L.

Description of key information

Short term toxicity to aquatic invertebrate, 2020:OECD 202, EU Method C.2; Daphnia magna; EC50 (48h): 0.67 mg/L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

0.67 mg/L

Additional information

The hydrolysis product of TFMOPI, Trifluormethoxyaniline, was tested in an acute toxicity test with Daphnia magna for 24h, resulting an EC50 of 19.6 mg/L.

 

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.