Butyl carbamate

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

No activated sludge respiration inhibition study was available with the SoI. However, as per ECHA R.7b guidance, absence of microbial toxicity can also be inferred from biodegradation studies in the laboratory. The assumption is that the substance under investigation is not inhibitory to the micro-organisms when dosed in the test system is implicit in ready biodegradability testing (i.e., EC C.4A-F, OECD 301A-F (OECD, 1992) and OECD 310 (2006)). Therefore, if a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value and new testing can be avoided.
The SoI has been tested in a 301B ready biodegradation study and more than 25% biodegradation occurred within 14 days (or 33%, based on inorganic carbon). Therefore, the test substance was assumed not to inhibit microbial activity at the nominal tested concentration of 39.7 mg/L (Muckle, 2016).

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From May 12, 2016 to June 15, 2016

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

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch no.: #120039110
Appearance: colorless, solid
Composition: >95% Butyl carbamate; <5% n-Butanol
Purity: 93.5% (GC-MS TIC area%)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Specification: cctivated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly domestic sewage.
- Source and Pre-Treatment:
Source: the sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf. Date of collection: 13. Mai 2016, batch no: 20160513.
Pre-Treatment: the sludge 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 4840 mg suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

39.6 mg/L

Based on:

other: nominal concentration of 20 mg organic carbon/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

- The medium was prepared from the stock solutions. The stock solution of the positive control was prepared and its TOC was measured. The inoculum was taken from its source, washed, aerated and the dry matter was determined. The test vessels were filled with medium and inoculum. Then, all flasks were aerated for 96 hours with purified, CO2-free, moistened air to purge the system of CO2. On the day of the start of the test, CO2-free medium and inoculum was filled into the test flask.
- Experimental parameters:
Flask volume: 1500 mL
Apparatus blanks: 2, containing mineral medium only
Blank Controls: 2, containing mineral medium and inoculum
Positive control flasks: 2, containing positive control, mineral medium and inoculum
Test flasks: 2, containing test substance, mineral medium and inoculum
Abiotic: control 1, containing test substance, mineral medium and HgCl2
Toxicity control: 1, containing test substance, positive control, mineral medium and inoculum
Inoculum concentration: 25.0 mg/L
Temperature: 19.1 – 21.6 °C
Duration: 28 days
The test was performed with a nominal start concentration of 20 mg organic carbon/L.
- The emitted CO2 was trapped in 0.25 M NaOH. Two scrubbers containing 100 mL each were connected in series to the test vessels. The initial IC value of the 0.25 M NaOH was separately determined in each flask.
- Sampling: from each front scrubber flask, 10 samples were taken in order to determine the emitted CO2 (on day 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO2 (see also chapter 8.2.1). On day 28, 5 mL HCl 2 M was added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.
- CO2 Determination: analyses of the emitted CO2 were made by IC measurement using the carbon analyser TOC.

Reference substance:

aniline

Remarks:

positive control

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

made by IC measurement

Value:

28

Sampling time:

28 d

Remarks on result:

other: not readily biodegradable

Remarks:

(but no plateau was reached by the end of the test indicating an inherent biodegradation potential)

Details on results:

The following data were determined for the test substance:
- 10-day-window (day 14 – 24): degradation at the end = 22%
- degradation at the end of the test (28 days) = 28%
Pass level following guideline: 60 % at the end of the test for mixtures. As degradation didn’t reach the target of 60% within 28 days, the test substance was considered as not readily biodegradable. However, at the end of the test, no plateau of degradation was reached yet, indicating further biodegradation is possible.

NB. Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test substance showed very good correspondence. If degradation in the toxicity flask is below 25% after 14 days, the test substance can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 33% after 14 days, the test substance could be stated as “not toxic towards the inoculum in a concentration of 39.7 mg/L”.

Results with reference substance:

The degradation of the positive control was 63% after 10 days.

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

Under the study conditions, the biodegradation of the test substance in water was determined to be 28% after 28d; not readily biodegradable. Nevertheless, considering that no plateau of degradation was reached at the end of 28 days is indicative that the test substance is inherently biodegradable.

Executive summary:

A study was conducted to determine the biodegradation in water of the test substance, according to OECD guideline 301 B and EU Method C.4-C (CO₂evolution test), in compliance with GLP. The substance was tested in duplicate at the concentration of 20 mg organic carbon/L (corresponding to 39.6 mg test substance/L) for a duration of 28 d. Test and reference substances (positive control: aniline and toxicity control; test substance plus aniline) were added to the bottles containing the microbial organisms (domestic sludge) and mineral components followed by sampling on Day 0, 3, 6, 8, 10, 14, 17, 23 and 29 to measure the CO2 evolution. The amount of CO2 produced was determined by inorganic carbon (IC) measurement using the carbon analyser TOC. Each sample was measured in duplicate or triplicate depending upon the variation.The test substance revealed 28% biodegradation (based on IC) in the duplicate test bottles. No toxicity of the test substance was observed in the toxicity control at a concentration of 39.7 mg/L; i.e., there was 33% degradation after 14 days. Abiotic degradation was not observed. Degradation of the positive control was 63% after 10 days. All validity criteria were met.Under the study conditions,the substance was considered as 'not readily biodegradable' in a CO2 evolution test (Muckle, 2016). Nevertheless, considering that no plateau of degradation was reached at the end of 28 days is indicative that the test substance is inherently biodegradable.