Quaternary ammonium compounds, di-C12-18-alkyldimethyl, chlorides

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Transformation products:

not specified

Remarks:

Refer to the endpoint summary

Description of key information

The available soil biodegradation studies with the read across substances indicated that around 18-60% mineralisation was observed within 120-430 days. Therefore, a half-life of 500 days was concluded in the EU RAR report for the purpose of risk assessment. Based on read across approach, a similar half-life can be assumed for the test substance.

Key value for chemical safety assessment

Half-life in soil:

500 d

Additional information

No soil biodegradation study could be located on C12 -18 DAQ. Therefore, literature evidence on read across substances (C16-18 DAQ and C18 DAQ), which has been exhaustively reviewed in the frame of a European Risk Assessment (RAR) published in 2002 by German Authorities. Both the test and read across substances are di-alkyl dimethyl ammonium chloride compounds. C18 DAQ or C16-DAQ is structurally the same but only differs in containing a longer average alkyl chain length. Longer alkyl chains are expected to be less bioavailable which likely results in lower biodegradation rates. Using the available biodegradation and half-life results available for C16-18 (and C18) DAQ for read-across to C12-18 DAQ is therefore considered as a worst-case approach (Refer to the read across justification for details).

 

An overview of the soil biodegradation studies from the EU RAR report have been presented below: 

Degradation of 14C-C18 DAQ(CAS 107-64 -2) in sandy loam and loam mixed with digested sewage sludge was measured with a batch incubated flask method (Fieler, 1975a). The 14CO₂-production was approximately 48% after 55 weeks in both soils, when 50 mg C18 DAQ per kg dry soil were applied. Addition of 30 mg/L LAS reduced the 14CO₂production to 38% indicating complexation of the anionic LAS with the cationic DAQ. Degradation of 0.5 mg C18 DAQ/kg dry soil was measured in loam soil amended with or without digested sewage sludge and two other soils. The 14CO2-production after 62 weeks was as follows: ca. 27% in sandy loam and loam with sludge; ca. 18% in loam without sludge and silt loam. At concentrations of 5 and 50 mg/kg C18 DAQ degradation increased in all soils with highest results of 50 and 63% in sludge amended soils.  

Degradation ofC18 DAQin soils over a long period of 116 days was reported also from other tests (Weston, 1987). 0.1 mg C18 DAQ/kg dry soil was degraded to 18-27% based on 14CO2-production and at 1.0 mg/kg degradation was 34-38%.  

A comparable degradation test withC16-18 DAQ(CAS 92129-33-4) lasted 120 days (Weston, 1989). In sandy loam with sludge 0.1 mg C16-18 DAQ/kg dry soil showed 36 and 52% 14CO2-production. Corresponding values of 38 and 41% were derived with 1.0 mg/kg under the same conditions.  

Procter & Gamble (1992, unpublished study, cited in ECETOC 1993.) performed various studies on the biological degradation ofC18 DAQin soils using several types of dispersion of the substance. Aqueous dispersion resulted in about 35% 14CO₂-production after a mean test period of 118 days. The mean degradation of C16-18 DAQ as a solution with a solvent was below 15% after a mean test period of 184 days. In these cases, the majority of the test results were obtained between 130 and 169 days where the 14CO₂-production was less than 10%. Degradation results for C16-18 DAQ in lecithin emulsions were in between. 

In a 72-day study, no degradation of 14C-C16-18 DAQcould be observed under anaerobic conditions (Fieler, 1975b). No other study could find any evidence that C16-18 DAQ undergoes anaerobic degradation.  

Overall, the available soil biodegradation studies with the read across substances indicated that around 18-60% mineralisation occurred within 120-430 days. Therefore, a half-life of 500 days was concluded in the EU RAR report for the purpose of risk assessment. Based on read across approach, a similar half-life can be assumed for the test substance.