trans-1,4-bis(isocyanatomethyl)cyclohexane

Short-term toxicity to fish

Administrative data

Endpoint:

short-term toxicity to fish

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
It is technically not feasible to perform aquatic toxicity studies due to rapid degradation of the study. In a hydrolysis study, 1,4-H6XDI was shown to rapidly disappear when dissolved in an aqueous solution. The speed at which this happens appears to be dependent on the pH, as at pH 4 the test item could only be detected at very low concentrations within the first 30 minutes, but was completely absent at later time points, while at pH 7 and pH 9 a gradual decrease was measured. At pH 7, the concentration of 1,4-H6XDI decreased to 25% of the start concentration after 3 hours, and became undetectable after 20 hours (no measurements in between), at pH 9 the concentration decreased below 10% after approximately 2.5 hours. These results indicate rapid hydrolysis. Since 1,4-H6XDI could not be detected, it is concluded that 1,4-H6XDI reacts with itself and/or hydrolysis/degradation products in all aquatic media, forming a complex mixture of numerous, high molecular weight products. This property precludes performance of relevant and reliable aquatic toxicity studies and therefore this study is waived.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 19 February 2016 to 23 June 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

2008

Deviations:

yes

Remarks:

Tier 2 study was performed at 1 instead of 3 temperatures in the preferred range of 10-70°C. Reason: very fast hydrolysis. Hydrolysis at temperatures above room temperature could not be analytically monitored due to methodological limitations.

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

yes

Remarks:

see above

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Version / remarks:

2008

Deviations:

yes

Remarks:

see above

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

UPLC-MS

Details on sampling:

PREPARATION OF THE SAMPLES
- Test item was spiked to the buffers using a solution of the test item in acetonitrile (2000 mg/L).
- Target concentration: 10 mg/L
- For each sampling time, duplicate sterile HPLC glass vials were filled with test solution.
- The vessels were placed in a temperature controlled environment in the dark.
- Blank buffers containing a similar content of co-solvent were treated similarly as the test samples (at t=0).

SAMPLING DETAILS
Samples for analysis were taken immediately after preparation (t=0) and at several sampling points after t=0.

pH MEASUREMENTS
The pH of the test solutions (except for the blanks) was determined at least at the beginning and at the end of the test (if appropriate).

Buffers:

Buffer pH 4: 16.7% 0.01 M sodium acetate and 83.3% 0.01 M acetic acid in water.

Buffer pH 7: 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide.

Buffer pH 9: 0.01 M boric acid and 0.01 M potassium chloride in water adjusted to pH 9 using 1 N sodium hydroxide.

Details:
- Sodium azide content in each buffer: 0.0009% (w/v)
- Kind of water: tap water purified by a purification system (Milli-Q, Millipore)

Details on test conditions:

TYPE OF TEST
The test item is known to be highly reactive with water. Therefore no preliminary test was conducted.
The Tier 2 study was performed.

TEST SYSTEM
- Sterilisation method: Each buffer was filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman) and transferred into a sterile vessel.
- Measures to exclude oxygen: nitrogen gas was purged through the sterile buffers for 5 minutes prior to preparation of the blank and test solutions.
- Measures taken to avoid photolytic effects: the test vessels were kept in the dark.

TEST MEDIUM
Identity and concentration of co-solvent: acetonitrile. The volume of the co-solvent was < 1% of the sample volume. Nominal concentrations were not corrected for the spiking volume.

ACTUAL TEMPERATURES
pH 4: 20.4°C ± 0.9°C
pH 7: 21.5°C ± 0.2°C
pH 9: 21.3°C ± 0.2°C

Duration:

0.7 h

pH:

4

Temp.:

20.4 °C

Remarks:

The concentration at t=0 was measured to be below the limit of detection.

Duration:

19.77 h

pH:

7

Temp.:

21.5 °C

Initial conc. measured:

9.2 mg/L

Remarks:

mean (n=2) conc.

Duration:

2.33 h

pH:

9

Temp.:

21.3 °C

Initial conc. measured:

7.3 mg/L

Remarks:

mean (n=2) conc.

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Preliminary study:

not conducted

Test performance:

pH 4
9 sampling times from 0 h to 0.7 h. Test item (max. 0.45 mg/L) was detected in one of the samples taken at 0.13 h, at 0.20 h and at 0.28 h. No test item was detected in all other samples. This indicated fast hydrolysis that could technically not be monitored.

pH 7
16 sampling times from 0 h to 19.77 h. The concentration decreased from 9.23 mg/L (at t=0) to 2.4 mg/L (at 3.13 h) and to a concentration below the limit of detection (at t=19.77 h).
Lineair regression curve (log. rel. conc. vs time ) over the time period from 0 to 3.13 h: Y = -0.167X + 1.87 (r=0.949).
Plot of the data points and the curve: see attachment

pH 9
13 sampling times from 0 h to 2.33 h. The concentration decreased from 7.48 mg/L (at t=0) to 0.55 mg/L (at t=2.33 h).
Lineair regression curve (log. rel. conc. vs time): Y = -0.271X + 1.52 (r=0.592)
Plot of the data points and the curve: see attachment
Linear relationship was not obtained. The results should be seen as estimated.

RECOVERIES
- Recovery is the concentration analysed at t=0 relative to the nominal concentration.
- The mean (n=2) recovery at pH 7 and pH 9 was calculated (see table below).
- The mean recovery for pH 7 fell within the criterion range of 90-110%.
- The mean recovery for pH 9 fell within the acceptable range for non-labelled chemicals of 70-110%.
- The concentrations analysed in the test samples were not corrected for recovery.

Transformation products:

not specified

Details on hydrolysis and appearance of transformation product(s):

no data

pH:

4

Temp.:

20.4 °C

Duration:

0 h

Remarks on result:

not determinable because of methodological limitations

Remarks:

The conc. at t=0 was below the limit of detection.

% Recovery:

92

pH:

7.1

Temp.:

21.5 °C

Duration:

0 h

% Recovery:

73

pH:

9

Temp.:

21.3 °C

Duration:

0 h

Key result

pH:

4

Temp.:

20.4 °C

Remarks on result:

not determinable because of methodological limitations

Key result

pH:

7

Temp.:

21.5 °C

Hydrolysis rate constant:

0.384 h-1

DT50:

2 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9

Temp.:

21.3 °C

Hydrolysis rate constant:

0.624 h-1

DT50:

1 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: see remark below

Details on results:

(Pseudo-)first order was not demonstrated for pH 9. Taken the low coefficient of correlation of 0.592 (obtained for all logarithms of the relative concentrations against time) and the obvious high variety in data points (see attachment), it was concluded that there is no linear relationship at pH 9 between the logarithms of the relative concentrations and time. Since the model for pseudo-first order was used for calculation of the half-life time, the result should be interpreted as an estimated value.

Conclusions:

The substance is hydrolytically unstable at pH 4, pH 7 and pH 9.
The half-life time of the substance at ca. 20°C at pH 7 and pH 9 was determined to be 2 hours and 1 hour, resp.
The half-life time of the substance at 20°C at pH 4 could not be determined due to fast hydrolysis.

Executive summary:

The hydrolysis test at pH values normally found in the environment (pH 4, 7 and 9) was performed in a GLP-compliant study according to EC C.7, OECD 111 and EPA OPPTS 835.2120.

Tier 2 study was performed at room temperature (i.e 20°C). Very fast hydrolysis at pH 4 which could not be monitored. The half-life time of the substance at 20°C at pH 4 could therefore not be determined.

The half-life time of the substance at ca. 20°C at pH 7 and pH 9 was determined to be 2 hours and 1 hour, respectively.