Didecyldimethylammonium chloride

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

other: Technical Assistance Document 3.12 of the Environmental Assessment Handbook, FDA.

GLP compliance:

no

Test type:

laboratory

Oxygen conditions:

aerobic

Soil classification:

other: loam

Details on soil characteristics:

-Nature: Loam
-Source: Heino, The Netherlands
-Sampling site: The soil was collected from below the litter layer
-Laboratory culture: No
-Method of cultivation: -
-Preparation of inoculum for exposure: Stones and plant fragments were removed by hand. After collection the soil was air dried for approximately 2 days and sieved through a 2 mm sieve.
-Pretreatment: No pretreatment, the soil was stored at room temperature in polyethylene bags until use in the experiment.
-Initial cell concentration:not applicable

Duration:

90 d

Initial conc.:

10 other: mg carbon/50 g soil

Based on:

other: carbon content

Humidity:

60%

Details on experimental conditions:

-Culturing apparatus: Slightly modified biometers described by Bartha and Pramer. Both the erlenmeyer and the side tube were closed with
Mininert valves to enable direct sampling from the side tube and to provide pure oxygen in the erlenmeyer. The erlenmeyer and the side tube
were fused together with an air-tight coupling so that the side tube and the erlenmeyer could be weighed separately.
-Number of culture flasks/concentration: 3
-Aeration device: -
-Measuring equipment: Dohrmann DC-190 NPOC apparatus
-Test performed in closed vessels due to significant volatility of TS: No
-Composition of soil: %OM: 2.4; % sand: 35.4; % silt: 49.3; % clay: 15.3
-CEC: 13.1 meq/100 g
-Additional substrate: No
-Test temperature: 22 +/- 3 degree C
-pH: 7.6
-Aeration of dilution water: No

Key result

% Degr.:

ca. 49

Parameter:

CO2 evolution

Sampling time:

114 d

Key result

DT50:

ca. 100 d

Type:

not specified

Remarks on result:

other: in loam soil

Transformation products:

not measured

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

not measured

There was 49% degradation of the test substance after 114 days. The test substance consists of ~50% didecyldimethylammonium chloride (active ingredient), ~20% 2-propanol and ~30% water. The presence of 2-propanol does not invalidate the use of this study for the evaluation of the biodegradability of the active ingredient. Biodegradation in this test is expressed as the ratio of carbon dioxide-carbon production to the carbon content of the product. The test substance contains 75% of didecyldimethylammonium chloride-carbon and 25% of 2-propanol-carbon. In the soil biodegradation test approximately 50% of the carbon is recovered as carbon dioxide within 114 days. The principal difficulty with this way of expressing biodegradability is that a fraction of the substrate will be transformed into biomass. Typically 50-90% of the carbon content is utilized for energy production, i.e. to support the energy-requiring processes of maintenance and growth of microorganisms. Only the energy-producing parts of the metabolic processes result in the immediate production of carbon dioxide. This implies most of the active ingredient is mineralized during the 114-day test period.

Conclusions:

The time required for 50% mineralization in soil is estimated 100 days.

Executive summary:

The soil degradation of the test substance (as 50% active ingredient in 20% 2-propanol and 30% water) was evaluated according to the Technical Assistance Document 3.12 of the Environmental Assessment Handbook, FDA. The substance was inoculated into samples of loam soil in modified biometers containing Erlenmeyer flasks under aerobic conditions and incubated for approximately 114 days. There was 49% degradation after 114 days in a loam soil. Biodegradation in this test was expressed as the ratio of experimental to theoretical carbon dioxide production. The carbon content in the test substance was as follows: 75% of the total carbon from DDAC and 25% from 2-propanol. In the soil biodegradation test, approximately 50% of the carbon was recovered as carbon dioxide within 114 days. The principal difficulty with this way of expressing biodegradability is that a fraction of the substrate will be transformed into biomass. Typically, 50-90% of the carbon content is utilized for energy production, i.e. to support the energy-requiring processes of maintenance and growth of microorganisms. Only the energy-producing parts of the metabolic processes result in the immediate production of carbon dioxide. This implies that a significant part of the active ingredient (ca. 50%) was mineralized during the 114 day test period (Van Ginkel and Pomper, 1994). 

Description of key information

Please note:A new better-quality biodegradation study is available under the biocides consortium for DDAC. LoA discussions are ongoing with the data owners and it is expected to be completed soon. Another dossier update will be submitted as soon as this study is made available. A brief summary of the data has been shared by the data owner (see below) to allow proceeding with risk assessment.

Based on the results of the study, the transformation showed a bi-phasic pattern; therefore the Single First Order Model (SFO) and the First-Order Multi-Compartment Model (FOMC) were compared. Based on the visual fit and x2 error, the transformation of [methyl-14C]DDAC met the requirements for the bi-phasic kinetic model (FOMC) well for all four soils. The transformation of the test substance can be considered to be rapid with DT50 values ranging from 10.3 to 17.7 days with the SFO model and 7.7 to 13.3 days with the FOMC model. The respective geometric mean DT50 values were determined at 27.87 and 20.80 days at 12 °C and 14.70 and 10.97 days at 20 °C respectively.

Considering that the test substance showed a bi-phasic pattern of degradation, the FOMC model-based geometric mean DT50 value of 20.80 days at 12 °C has been considered further for hazard/risk assessment.

Key value for chemical safety assessment

Half-life in soil:

20.8 d

at the temperature of:

12 °C

Additional information

Study 1:A new study was conducted to determine the soil degradation potential of the radiolabelled test substance, DDAC in soil according to OECD Guideline 307, in compliance with GLP. Based on the results of the study, the transformation showed a bi-phasic pattern; therefore the Single First Order Model (SFO) and the First-Order Multi-Compartment Model (FOMC) were compared. Based on the visual fit and x2 error, the transformation of [methyl-14C]DDAC met the requirements for the bi-phasic kinetic model (FOMC) well for all four soils. The transformation of the test substance can be considered to be rapid with DT50 values ranging from 10.3 to 17.7 days with the SFO model and 7.7 to 13.3 days with the FOMC model. The respective geometric mean DT50 values were determined at 27.87 and 20.80 days at 12 °C and 14.70 and 10.97 days at 20 °C respectively.To be updated, once the LoA is available.

 

Study 2:The soil degradation of the test substance (as 50% active ingredient in 20% 2-propanol and 30% water) was evaluated according to the Technical Assistance Document 3.12 of the Environmental Assessment Handbook, FDA. The substance was inoculated into samples of loam soil in modified biometers containing Erlenmeyer flasks under aerobic conditions and incubated for approximately 114 days. There was 49% degradation after 114 days in a loam soil. Biodegradation in this test was expressed as the ratio of experimental to theoretical carbon dioxide production. The carbon content in the test substance was as follows: 75% of the total carbon from DDAC and 25% from 2-propanol. In the soil biodegradation test, approximately 50% of the carbon was recovered as carbon dioxide within 114 days. The principal difficulty with this way of expressing biodegradability is that a fraction of the substrate will be transformed into biomass. Typically, 50-90% of the carbon content is utilized for energy production, i.e. to support the energy-requiring processes of maintenance and growth of microorganisms. Only the energy-producing parts of the metabolic processes result in the immediate production of carbon dioxide. This implies that a significant part of the active ingredient (ca. 50%) was mineralized during the 114 day test period (Van Ginkel and Pomper, 1994). 

Considering that the test substance showed a bi-phasic pattern of degradation, the FOMC model-based geometric mean DT50 value of 20.80 days at 12 °C has been considered further for hazard/risk assessment.