Aminocaproic acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

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 acute toxicity tests with algae, had an analytical purity of 99.9 %. The target substance 6-aminocaproic acid, CAS 60-32-2, had a purity of >= 98 % (w/w) . Thus, the purity of both test materials is comparable.

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data i.e. acute toxicity studies with algae were available for epsilon-caprolactam. Epsilon-caprolactam was tested in an study according to OECD 201. This study revealed an EC50 (growth rate) of > 1000 mg/L and an EC10 (growth rate) 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 for cross-reference:

read-across source

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Description of key information

In a read across with the source substance epsilon-caprolactam (CAS 105-60-2), the NOEC (72h) and the EC50 (72h) of the target substance 6-aminocaproic acid (CAS 60-32-2) were determined to be 1000 mg/L and >1000 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 000 mg/L

EC10 or NOEC for freshwater algae:

1 000 mg/L

Additional information

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

Key study

The study was performed as GLP guideline test according to OECD 201 with the structural analogue epsilon-caprolactam (CAS 105-60-2). By use of a static procedure and Pseudokirchneriella subcapitata as test species, a NOEC (72h) of 1000 mg/L and an EC50 (72h) >1000 mg/L were derived.