Hexahydro-2H-azepin-2-one, sodium salt

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

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
Please refer to the Read-across Statement attached in Section 13.2.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target substance is very prone to hydrolysis resulting in the formation of epsilon-caprolactam and sodium hydroxide. As hydrolysis of the target substance will inevitably occur both under physiological and under environmental conditions, the evaluation of the data of epsilon-caprolactam and sodium hydroxide is considered to be sufficient for hazard assessment. Thus, the toxicological behavior of BRUGGOLEN® C10 can be considered to be determined by the hydrolysis products caprolactam and caustic soda.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Target substance: sodium caprolactamate, CAS-No. 2123-24-2 (for detailed composition please refer to the Read-across Statement attached in Section 13.2)
Source substances: epsilon-caprolactam, CAS-No. 105-60-2 and sodium hydroxide, CAS-No. 1310-73-2

3. ANALOGUE APPROACH JUSTIFICATION
The justification of the read-across hypothesis is mainly based on the hydrolysis of the target substance into the source substances.
BRUGGOLEN® C10 is a combination of sodium caprolactamate (17 – 20 %) and epsilon-caprolactam (80 – 83 %). If diluted in water, sodium caprolactamate easily degrades to caprolactam and sodium hydroxide (caustic soda). Reason is the instability of the ionic N-Na-bond of the sodium caprolactamate.
Thus, the toxicological behavior of BRUGGOLEN® C10 can be considered to be determined by the hydrolysis products caprolactam and caustic soda.

4. DATA MATRIX
Please refer to the Read-across Statement attached in Section 13.2.

Reason / purpose for cross-reference:

read-across source

Duration:

96 h

Dose descriptor:

LC0

Effect conc.:

100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Description of key information

Fish toxicity, freshwater, acute > 100 mg/L

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L

Additional information

Data obtained by Read-Across from ε-caprolactam:

As a semistatic study with epsilon-Caprolactam (GLP) according OECD 203 performed at the Mitsubishi Chemical Safety Institute for the Ministry of Environment, Government of Japan with Medaka as test species resulted in a LC50 (96h) >100 mg/l. A supporting study by BASF (1987) according OECD 203 confirms this result: LC50 (96h) = 707 mg/l .

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Data obtained by Read-Across from sodium hydroxide:

At concentrations reported in publications and study reports, the toxicity has been assumed to be

due to hydroxide only, because at these effect concentrations the concentration of sodium is too low

to explain the effects. However, it should be realised that the results of toxicity tests with NaOH

depend on the buffer capacity of the test medium. In a highly buffered test medium the hydroxyl ion

will be neutralized and the observed toxicity will be low, while in a poorly buffered test medium the

pH will increase rapidly and therefore the observed toxicity will be relatively high (see also section

2.1). Besides the direct effects (pH change) NaOH could also have indirect effects. The pH change

could influence the speciation of other chemicals and therefore increase and/or decrease the toxicity

e.g. NH3 is more toxic than NH4 +.

A 24-hour toxicity test with Carassius auratus (goldfish) revealed an LC50 of 160 mg/l (Jensen,

1978). At 100 mg/l, which was equivalent to a pH of 9.8, no mortality was observed. A toxicity test

with a related species, Leuciscus idus melanotus, revealed an LC50 of 189 mg/l (Juhnke et al.,

1978). A 96-hour test with Gambusia affinis (mosquitofish) revealed an LC50 of 125 mg/l (Wallen,

1957). At 84 mg/l no effects on the fish were observed. The pH was 9 at 100 mg/l. Solutions of

NaOH in pond water started to be toxic to the fry of Lucioperca lucioperca L. (pike perch) at NaOH

concentrations of 35 mg/l and higher (Stangenberg, 1975).