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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source substance is the cyclic epsilon-caprolactam, which converts in aqueous solution to the linear 6-aminocaproic acid by hydrolytic ring-opening (Tirrell et al., 1975). Hence, 6-aminocaproic acid will be present regardless whether epsilon-caprolactam or 6-aminocaproic acid was used as test material. Moreover, hydrolysation of epsilon-caprolactam to 6-aminocaproic acid is to be expected in aquatic environmental systems, which allows the read across between the two test materials.

Cited literature:
M. V. Tirrell, G. H. Pearson, R. A. Weiss and R. I. Laurence: An Analysis of Caprolactam Polymerisation. Polymer Engineering and Science, May, 1975, Vol. 15, No. 5, Pages 386 - 393.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance epsilon-caprolactam, CAS 105-60-2, which was used in the most current acute toxicity test with Daphnia magna (reference 6.1.3-1), had a analytical purity of 99.9 %. No information on impurities is available. The target substance 6-aminocaproic acid, CAS 60-32-2, had a purity of >= 98 % (w/w). Thus, the purity of the test materials is comparable.

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data i.e. acute toxicity studies with Daphnia magna were available for epsilon-caprolactam. Epsilon-caprolactam was tested in an study according to OECD 202. This study revealed an EC50 of > 1000 mg/L. The information given on epsilon-caprolactam is considered to be sufficient to cover the required endpoint information for the target substance 6-aminocaproic acid.
Reason / purpose:
read-across source
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
mobility

Description of key information

In a read across with the source substance epsilon-caprolactam (CAS 105-60-2), the EC50 (48h) of the target substance 6-aminocaproic acid (CAS 60-32-2) was determined to be >1000 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
1 000 mg/L

Additional information

No data on toxicity to aquatic invertebrates were available for the substance 6-aminocaproic acid (CAS 60-32-2) itself. Therefore, a read across to the close structural analogue epsilon-caprolactam (CAS 105-60-2) was conducted.

Key study

In a static GLP-compliant study according to OECD guideline 202 with the structural analogue epsilon-caprolactam (CAS 105-60-2), the EC50 (48h) of the test item was determined to be >1000 mg/L (reference 6.1.3-1).

Conclusion

The toxicity of 6-aminocaproic acid (CAS 60-32-2) to aquatic invertebrates was assessed in a read across to the structural analogue epsilon-caprolactam (CAS 105-60-2). Based on the most current and reliable information (reference 6.1.3-1), the EC50 (48h) of the target substance 6-aminocaproic acid (CAS 60-32-2) was determined to be > 1000 mg/L.