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Environmental fate & pathways

Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08 June, 2005 to 24 February, 2006
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study was conducted according to the OECD guideline 301B as well as in compliance with GLP.
Justification for type of information:
Direct read-across from C16 TMAC to Cetrimonium chloride is claimed as valid because they are both trimmoniums sharing a common alkyl chain length n=16. C16 TMAC is also known as the cetrimonium ion, exhibts properties and effects consistent with a category of quaternary ammonium compounds known as the alkyl trimoniums. C16 TMAC is commonly known as the cetrimonium ion. In pure form QACs also contain an anion such as chloride, bromide or methosulfate. When in solution the substances will be dissociated and the anion the QACs were once associated with will be irrelevant. See attached justification.
The test substance used is named as cetrimonium chloride.
according to guideline
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Physical state: Slightly yellowish liquid- Analytical purity: 28.9%- Lot/batch No.: DEGE115035- Storage condition of test material: Room temperature- Other: Total organic carbon content- 21.9%
Oxygen conditions:
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Source of inoculum/activated sludge: Municipal sewage treatment plant, D-31137 Hildeshheim- Initial cell/biomass concentration: 1.0E+7 to 1.0E+8 CFU/L
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- Composition of medium: Mineral nutrient solution according to ORCD 301 B/CO2 evolution test.
- Test temperature: 22 ± 2°C.- pH:
- Aeration of dilution water: 30 to 100 mL/min.

- Culturing apparatus: 5 litre brown glass bottles.
- Number of culture flasks: 2 for test substance and 1 for reference material.
- Details of trap for CO2: 100 mL flasks to absorb CO2 in the Ba(OH)2 solution.

- Sampling frequency: Three times a week during the first 10 d and thereafter twice a week until the Day 28.- Other: On the Day 28, 1 mL of 37% HCI added to flasks in order to eject all the remaining CO2 and last sampling was carried out on the Day 29.

- Inoculum blank: Yes
Reference substance:
acetic acid, sodium salt
at concentration of 30 mg/L = 10.2 mg carbon/L
% degradation (CO2 evolution)
ca. 93.5
Sampling time:
28 d
Details on results:
With the test substance, the 10% level (beginning of biodegradation) was reached by one replicate after 7 d and the pass level of 60% was reached after 17 d. The other replicate reached the 10% level after 12 d and 60% after 19 d. The biodegradation came to 92% and 95% respectively after 28 d. Hence, the mean biodegradation extent of the test substance can be calculated to be 93.5% within 28 d after acidification (mean value of two test vessels).
Results with reference substance:
The functional control reaches a biodegradation rate of more than 60% after 10 d.

Table 1: Biodegradation of the test substance in comparison to the functional control and toxicity control.


Biodegradation (%) on Study day (d)






Test substance,
1streplicate 30 mg/





Test substance,
2nd replicate 30





Functional control
35 mg/L





Toxicity control
30 mg/L test
substance + 35
mg/L reference






- The total CO2 evolution in the inoculum blank at the end of the test was 40 mg/L.

- The biodegradation of the reference substance reached the pass level of ≥60% by Day 14.

- The biodegradation of the toxicity control reached the pass level of 25% after 14 d.

- The difference of extremes of replicate values of removal of the test substance at the end of the 10-d-window was less than 20%.

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable
Under the test conditions, the test substance was readily biodegradable after 28 d.
Executive summary:

A guideline study was conducted to determine the ready biodegradability of C16 TMAC according to the CO2 -evolution test method (modified Sturm test). Sodium acetate was used as a functional control to check the activity of the test system. The control achieved 60% biodegradation after 10 days. The toxicity control, containing both the test and the reference substance, achieved 43% biodegradation within 14 days. The test substance in the toxicity control did not inhibit biodegradation of the reference substance. With C16 TMAC, the 10% level (beginning of biodegradation) was reached by one replicate after 7 days and the pass level of 60% was reached after 17 days. The other replicate reached the 10% level after 12 days and 60% after 19 days. Within 28 days 92 and 95% biodegradation was observed in the two replicate samples, mean biodegradation was 93.5%. Under the test conditions, the substance was readily biodegradable.

Description of key information

Under the test conditions, the test substance was readily biodegradable after 28 d.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:

Additional information