L-cystine dihydrochloride

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

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
No study with the target substance L-cystine dihydrochloride is available. However a study with L-cysteine hydrochloride is available and considered reliable. Since L-cysteine and L-cystine can be formed from one in the other, L-cysteine hydrochloride is considered to be a suitable source substance for read-across purpose..

2. SOURCE AND TARGET CHEMICAL(S)
No further information.

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data for short term toxicity to Daphnia magna, are available for L-cysteine hydrochloride. The study was conducted according to OECD guideline 202. This GLP study is considered reliable and well documented. Under oxidative conditions two L-cysteine molecules form disulfide bonds and L-cystine is formed. In the available study both substances were analytical determined. Measurements showed that over time the concentration L-cysteine decreased and L-cystine increased. The result presents the combined toxicity of both substances. Therefore, the information of the available study is considered to be sufficient to cover the required endpoint information for the target substance L-cystine dihydrochloride.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26.07.2016 to 01.08.2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The four test vessels of the control and test item group with aged medium (24 h after preparation) were pooled before sampling. Samples were deep -frozen. Prior to analysis the samples were slowly thawed and analysed undiluted.

Vehicle:

no

Details on test solutions:

A stock solution of 100 mg/L was freshly prepared by stirring the solution for 5 minutes with a magnatic stirrer.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna (Straus)
- Source: IBACON GmbH, Roßdorf, Germany
- Age of parental stock (mean and range, SD): Less than 24 hours old
- Feeding during test: no

ACCLIMATION
- Acclimation period: no

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

not specified

Test temperature:

19.5 - 20.0°C

pH:

7.53 - 7.83

Dissolved oxygen:

7.97 - 8.07

Salinity:

not specified

Conductivity:

not specified

Nominal and measured concentrations:

Nominal concentration: 100 mg/L
Recoveries were above 95% and therefore endpoints are based on nominal concentration.

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beaker
- Medium volume per beaker: at least 40 mL
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Medium renewal: after 24 h

OTHER TEST CONDITIONS
- Photoperiod: 16 h light and 8 h darkness

Reference substance (positive control):

yes

Remarks:

Potassium dichromate, experimental phase: 27 – 29 April 2016

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

There was no immobilisation observed in twenty daphnies exposed to either test item treated or control group. In addition to immobility, no abnormal behaviour or appearence of the test animals was detected.

Results with reference substance (positive control):

24h EC50: 1.00 mg/L (95 % confidence limits: 0.85 – 1.23 mg/L)

Reported statistics and error estimates:

No effects were observed therefore, no statistical evaluation was performed.

Validity criteria fulfilled:

yes

Conclusions:

In this 48-hour semi-static acute toxicity limit test with Daphnia magna the effects of the test item on the mobility was determined. The 48-h EC50 value was determined to be > 100 mg/L.

Executive summary:

The purpose of this study was to evaluate the influence of the test item on the mobility, respectively survival of Daphnia magna in a semi-static test system. Young Daphnia were exposed in an immobilisation test to aqueous test media containing the test item at 100 mg/L. Twenty Daphnia, divided into four groups of five animals each were exposed to the test item concentration or run as control for 48 hours. The 48-h EC50 value was determined to be > 100 mg/L.

Description of key information

The 48-h EC50 of the substance on Daphnia magna was determined to be > 100 mg/L.

Additional information

No data for short-term (acute) toxicity for daphnia for the target substance L-cystine dihydrochloride were available. Therefore read across was performed.

In the acute immobilisation test (reference 6.1.3-1) with Daphnia magna (STRAUS), the effects of the source substance were determined according to OECD Guideline for testing of chemicals, Guideline No. 202, adopted 13th April 2004. The study was conducted in a semi-static system as a limit test over a period of 48 hours with a nominal concentration of > 100 mg/L. The validity criteria of the test guideline were fulfilled. The EC50 value (48 hours) was determined to be > 100 mg/L.