L-cystine dihydrochloride

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24.04.2017 to 24.05.2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: sewage plant for mainly domestic sewage in Neustadt, Germany
- Storage length: 7 days before the main test
- Preparation of inoculum for exposure: The inoculum was filtrated, washed with tap water (2x), then washed with and re-suspended in test medium. It was then aerated until use. The dry matter was determined as 4040 .g suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium used. Prepared according to OECD 301.
- Test temperature: 20.1 - 21.5°C
- pH: 7.53 - 7.83
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: 25 g dry material/L

TEST SYSTEM
- Culturing apparatus: 1500 mL flasksottles
- Apparatus blanks: 2, containing mineral medium only
- Blank controls: 2, containing mineral medium and inoculum
- Positiv control: 2, containing positiv control, mineral medium and inoculum
- Test flask: 2, containing test item, mineral medium and inoculum
- Abiotic control: 1, containing test item, mineral medium and HgCl2
- Toxicity control: 1, containing test item, positiv control, mineral medium and inoculum
- Measuring equipment: Emitted CO2 was trapped in 0.25 NaOH

SAMPLING
- Sampling frequency: on days 0, 2, 4, 8, 10, 14, 18, 23 and 29

Reference substance:

other: Aniline (Phenylamine)

Key result

Parameter:

% degradation (CO2 evolution)

Value:

87

Sampling time:

28 d

Details on results:

The threshold for ready biodegradability defined as 60% within 10 days after reaching a level of 10% was fullfilled. Therefore, the test item can be considered as ready biodegradable.

Results with reference substance:

Degradation behaviour of the positive control was normal. Abiotic degradation reached 1.2%.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test item is considered to be ready biodegradable. The pass level for ready biodegradability of 60 % removal in a 10-day window was fulfilled. The biodegradation percentage at the 28 day mark was 87%.

Executive summary:

The ready biodegradability of the test item was determined with a non adapted activated sludge over a test period of 28 days in a test design according to OECD 301 B and Regulation (EC) No. 440/2008 Method C.4 -C. The test item was tested at a inital concentration of 20 mg organic carbon/L. The evolved CO2 was trapped in 0.25 M NaOH. Abiotic degradation reached 1.2%. The test item is considered to be ready biodegradable. The pass level for ready biodegradability of 60 % removal in a 10-day window was fulfilled. The biodegradation percentage at the 28 day mark was 87%

Description of key information

The test item is considered to be ready biodegradable, since the pass level for ready biodegradability (removal of 60% in a 10-day window) was fulfilled (reference 5.2.1-1).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradation test was conducted according to the test method OECD 301 B (reference 5.2.1-1). The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the CO2 evolution during exposure. All validity criteria of the study were met. The percentage biodegradation of the test item reached 87% after 28 days. The pass level for ready biodegradability is the removal of 60% within a 10-day window and therefore, the test item is considered to be ready biodegradable.