Cyclohexane, 1,3-bis(isocyanatomethyl)-

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, substance analogue 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. As 1,3-H6XDI also has two N=C=O groups and a saturated ring and cis/trans isomerism is not expected to have a significant influence on reactivity, it is expected to react in a similar way when dissolved in aqueous solution. 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:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The rationale to read across the data is attached in section 13.

Reason / purpose for cross-reference:

read-across source

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

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:

other: see "overall remarks"

Pseudo-first behaviour at pH 9 was not demonstrated. 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. This result is read across to 1,3-H6XDI.

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. This result is read across to 1,3-H6XDI.