Didecyldimethylammonium chloride

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From January 26, 2004 to March 09, 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling: Soil samples were analysed for nitrate at the beginning and at the end of the exposure period

Vehicle:

yes

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: Soil was amended with Glucose at various concentrations i.e. 1, 10, 50, 100 and 200 micor mol per g soil


APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: Glucose: Talcum powder (1 :5) mixtures were added to the soils. CO2 evolution from the soil was measured every hour for 6 h

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Remarks:

-

Test temperature:

20 °C

Moisture:

43 %

Details on test conditions:

TEST SYSTEM
- Testing facility: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Speyer, Germany and Blgg Oosterbeek, The Netherlands
- Test container (type, material, size): Flasks made of glass (0.25 L)
- Amount of soil: 50 g
- No. of replicates per concentration: 3

SOIL INCUBATION
- Method: bulk / series of individual subsamples: Aerobic conditions

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Sandy loam; Fallow soil of garden in Offenbach, Rheinland Pfalz, Germany
- Soil taxonomic classification: Sandy loam
- Soil classification system: US Comprehensive Soil Classification System of the Soil Conservation Service
- pH (in water): 6.3±0.4
- Maximum water holding capacity (in % dry weight): 35.2 ± 3.4
- Cation exchange capacity (mmol/kg): 10± 2
- Storage (condition, duration): Stored in the refrigerator in polyetheylene bags until use in the experiment for 10 wk
- Initial microbial biomass as % of total organic C: 0.23

DETAILS OF PREINCUBATION OF SOIL (if any): Preconditioned by incubating the soil for 7 d at 20 at 10 % of its water holding capacity

Nominal and measured concentrations:

0, 50, 100, 200, 400, 800, 1600, 3200 and 6400 mg a.i./kg

Reference substance (positive control):

yes

Remarks:

Sodium nitrate

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

ca. 120 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Remarks on result:

other: 0.07-0.16 mg/g

Key result

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

ca. 70 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

nitrate formation rate

Details on results:

The activity of the microorganisms transforming nitrogen in soil was slightly inhibited at 50 mg a.i. /kg DDAC. The EC50 calculated was 120 mg a.i./kg with 95% confidence limits of 70 mg a.i./kg and 160 mg a.i./kg. The EC10, EC20 and EC80 of DDAC were 70, 80 and 160 mg a.i./kg respectively. (175, 200 and 400 mg of test substance)

Results with reference substance (positive control):

No data

Reported statistics and error estimates:

No data

The dose response relationship shows a normal pattern. According to the OECD guidelines the variation between the three control replicates should be less than 15 %. This criteria was met because the variation was less than 10 %. Therefore the test is considered valid. In soil not only formation of nitrate occurs but also reduction of nitrate to nitrogen gas by denitrifying
microorganisms. Decrease of the nitrate concentrations in the soil at DDAC concentration of 400 mg a.i. /kg and higher after 28 d is probably the result of the activity of these denitrifying microorganisms.  Denitrifying microorganisms are not affected by DDAC at concentrations ranging from 400 to 3200 mg a.i. /kg whereas the microorganisms responsible of the formation of nitrate are inhibited at these concentrations. The denitrifying microorganisms are inhibited at 6400 mg a.i./kg of DDAC because  after  28 d only a limited amount of the nitrate was removed.

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the EC50 and EC10 values for nitrogen transformation in soil was determined to be 120 and 70 mg a.i./kg, respectively.

Executive summary:

A study was conducted to evaluate the effects of test substance, DDAC (40% active) in soil microorganisms nitrogen transformation test, according to OECD Guideline 216, in compliance with GLP. The activities of the microorganisms mineralizing nitrogen-containing organic substances and nitrifying bacteria present in the soil exposed to various concentrations were compared to the control to calculate the inhibition in percentages. The microorganisms were exposed to the following test concentrations which was added to sandy loam: 50, 100, 200, 400, 800, 1600, 3200 and 6400 mg a.i./kg wet weight (ww). The soil samples were analysed for nitrate at the beginning (Day 0) and at the end of the exposure period (Day 28). Form the relation between the concentrations and the respective inhibition percentages, EC values have been determined. Nominal concentrations were used to calculate the EC values because nominal and actual concentration corresponded well. The activity of the microorganisms transforming nitrogen in soil was slightly inhibited at 50 mg a.i. /kg test substance. The EC50 calculated was 120 mg a.i. /kg with 95% confidence limits of 70 mg a.i. /kg and 160 mg a.i. /kg. The EC10, EC20 and EC80 of DDAC were 70, 80 and 160 mg a.i. /kg respectively (equivalent to 175, 200 and 400 mg of test substance). The test met the validity criteria, as the variation between the control replicates were less than 10%. Under the study conditions, the EC50 and EC10 values were determined to be 120 and 70 mg a.i./kg (nominal), respectively (Van Ginkel & Van der Togt, 2004).

Description of key information

Based on the study results, the 28-day EC50 and EC10 values for effects on nitrogen transformation in soil was considered to be 120 and 70 mg/kg soil dw (nominal). 

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:

120 mg/kg soil dw

Long-term EC10 or NOEC for soil microorganisms:

70 mg/kg soil dw

Additional information

A study was conducted to evaluate the effects of the test substance (40% active) on soil microorganisms nitrogen transformation according to OECD Guideline 216, in compliance with GLP. The activities of the microorganisms mineralizing nitrogen-containing organic substances and nitrifying bacteria present in the soil exposed to various concentrations were compared to the control to calculate the inhibition in percentages.Inhibition of microbial nitrogen transformation through nitrate measurement at beginning and end of the test on Day 28. Form the relation between the concentrations and the respective inhibition percentages, EC values have been determined. The dose response relationship showed a normal pattern. According to the OECD guidelines the variation between the three control replicates should be less than 15%. This criterion was met because the variation was less than 10%. Therefore, the test is considered valid. In soil not only formation of nitrate occurred but also reduction of nitrate to nitrogen gas by denitrifying microorganisms. Decrease of the nitrate concentrations in the soil at DDAC concentration of 400 mg a.i. /kg and higher after 28 d was probably the result of the activity of these denitrifying microorganisms. Denitrifying microorganisms were not affected by read across substance at concentrations ranging from 400 to 3200 mg a.i. /kg, whereas the microorganisms responsible of the formation of nitrate were inhibited at these concentrations. The denitrifying microorganisms were inhibited at 6400 mg a.i./kg of read across substance because after 28 d only a limited amount of the nitrate was removed. The activity of the microorganisms transforming nitrogen in soil was slightly inhibited at 50 mg a.i. /kg read across substance. The EC50 calculated was 120 mg a.i. /kg with 95% confidence limits of 70 mg a.i. /kg and 160 mg a.i. /kg. The EC10, EC20 and EC80 were 70, 80 and 160 mg a.i. /kg, respectively (Van Ginkel & Van der Togt, 2004).

The DDAC biocides assessment report for Product Type 8 conducted under Directive 98/8/EC (evaluating Competent Authority: Italy, June 2015, attached in Section 13 of the IUCLID dataset), reported an additional study on DDAC, apart from the above EQC study. This study resulted in a 28 d EC10 >1000 mg/kg dw and 28 d EC50 >1000 mg/kg dw for both carbon and nitrogen mineralization tested in two soils (sandy loam and low humic content sand). The RMS considered the lower value from the EQC study as the endpoint for the product authorisation.