Miristalkonium chloride

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From May 16, 2007 to May 17, 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identity: Barquat MS 100
Chemical name: N-Alkyl(C12-C14)-N,N-dimethyl-N-benzylammonium chloride (ADBAC C12-C14)
Lot number: 612212
Expiry date: 21 December 2009
Purity: 99.1% C14 ADBAC, 0.6% Free amine, 0.4% Amine hydrochloride
Appearance: White powder
Storage conditions: Room temperature
Stability: The a.i., ADBAC, is hydrolytically and photolytically stable under the conditions of this study and has been shown to be stable in aqueous, alcohol and alcohol/aqueous solutions for extended periods, e.g. at least five years under standard laboratory conditions

Analytical monitoring:

no

Vehicle:

yes

Remarks:

Water

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Preparation of the microbial inoculum
A sample of activated sludge was obtained the day before the start of the test from Worlingworth Sewage Treatment Works, which treats predominantly domestic waste. In the laboratory, the samples were maintained under aerobic conditions at 20 ± 2ºC until required. The concentration of suspended solids in a homogenised sub-sample was determined on the day of collection and immediately before the start of the test. On the day of collection, an aliquot (10 mL) of the sludge was filtered through a dried and preweighed Whatman GF/C filter, which was then dried again at approximately 105ºC for at least one hour, allowed to cool in a desiccator and reweighed. The mixed liquor suspended solids (MLSS) content of the activated sludge was then calculated. Synthetic sewage (50 mL/L) was added to the stock of activated sludge, which was aerated overnight. On the day of the test, the MLSS content of the sludge was determined by filtering the sludge in triplicate, and adjusted to 4 g/L by the addition of tap water and the pH measured.

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

30 min

Remarks on exposure duration:

Control and test substance cultures exposure: 30 minutes

Test temperature:

19.7-20.1

pH:

7.4-7.7

Dissolved oxygen:

2.5-9.1% mgO2/L

Nominal and measured concentrations:

0.8, 2.4, 7.8, 25 and 80 mg/L - Test substance
3, 10 and 32 mg/L - Reference substance

Details on test conditions:

Dilution water
The dilution water used to prepare solutions of synthetic sewage, reference substance and mixtures was tap water that had been softened and purified using reverse osmosis, RO (Prima 4 reverse osmosis unit). This equates to Type IV water (ASTM D1193-06) and Grade 3 water (BS 3978).

Synthetic sewage
Synthetic sewage feed (stored at ca. 4ºC in the dark for no more than 5 days) for activated sludge was prepared by dissolving the following in one L of RO water:
peptone - 16.0 g
meat extract - 11.0 g
urea - 3.0 g
sodium chloride - 0.7 g
calcium chloride dihydrate - 0.4 g
magnesium sulphate heptahydrate - 0.2 g
di-potassium hydrogen phosphate - 2.8 g

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (3,5-DCP), Purity: 99.9% (product code 113610100, batch number A0229627) was obtained from ACROS Organics.

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

ca. 27.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Inhibition on respiration rate

Remarks on result:

other: 95% confidence limits: 23.4 – 31.7 mg/L

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

ca. 10.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Inhibition on respiration rate

Remarks on result:

other: 95% confidence limit: 9.2 – 12.9 mg/L

Results with reference substance (positive control):

The thirty-minute EC50 for 3,5-DCP (10.9 mg/L) fulfilled the validity criterion relating to sensitivity to inhibition (acceptable EC50 range 5 to 30 mg/L). The validity criterion relating to the respiration rates in the control (variation not greater than 15%) was also satisfied.

Validity criteria fulfilled:

yes

Conclusions:

Under study conditions, the  30 min EC50 of test substance was found to be 27.3 mg/L (95% confidence limits, 23.4 – 31.7 mg/L).

Executive summary:

A study was conducted to determine the effect of test substance, C14 ADBAC (purity: 99.1%), on the respiration rate of activated sludge according to the OECD Guideline 209 and EU method C.11, in compliance with GLP. Samples of activated sludge (suspended solids 1.6 g/L) fed with synthetic sewage, were exposed to the test substance at nominal concentrations of 0.8, 2.4, 7.8, 25 and 80 mg/L for 30 minutes. Their rates of oxygen consumption were determined and compared with those of controls, containing activated sludge and synthetic sewage alone, which were established at the beginning and end of the culture series. The reference inhibitor 3,5-dichlorophenol (3,5-DCP) was employed at 3, 10 and 32 mg/L, as a positive control. The specific respiration rate of the control culture established at the end of the test series (23.7 mgO2/g/h) was 102% of the rate of that established at the start (23.3 mgO2/g/h). The thirty minute 50% effect concentration (EC50) for 3,5-DCP was calculated to be 10.9 mg/L (95% confidence limits 9.2 – 12.9 mg/L). These results show that the test was valid and that the sample of activated sludge employed was sensitive to inhibition. Concentration-related inhibition of respiration rates was seen at test substance concentrations greater than 2.4 mg/L. The highest tested concentration (80 mg/L) caused 85% inhibition. The EC50 of test substance was calculated to be 27.3 mg/L (95% confidence limits, 23.4 – 31.7 mg/L). The EC20 and EC80 values were calculated to be 10.9 and 68.3 mg/L, with 95% confidence limits of 8.1 – 14.1 and 54.8 – 87.5 mg/L, respectively.  Under study conditions, the 30 min EC50 of test substance was found to be 27.3 mg/L (Barnes, 2007).

Description of key information

Based on the study results, the 30 min EC50 of test substance for inhibition of respiration rate of activated sludge was found to be 27.3 mg/L (nominal).

Key value for chemical safety assessment

EC50 for microorganisms:

27.3 mg/L

Additional information

A study was conducted to determine the effect of test substance, C14 ADBAC (purity: 99.1%), on the respiration rate of activated sludge according to the OECD Guideline 209 and EU method C.11, in compliance with GLP. Samples of activated sludge (suspended solids 1.6 g/L) fed with synthetic sewage, were exposed to the test substance at nominal concentrations of 0.8, 2.4, 7.8, 25 and 80 mg/L for 30 minutes. Their rates of oxygen consumption were determined and compared with those of controls, containing activated sludge and synthetic sewage alone, which were established at the beginning and end of the culture series. The reference inhibitor 3,5-dichlorophenol (3,5-DCP) was employed at 3, 10 and 32 mg/L, as a positive control. The specific respiration rate of the control culture established at the end of the test series (23.7 mgO2/g/h) was 102% of the rate of that established at the start (23.3 mgO2/g/h). The thirty minute 50% effect concentration (EC50) for 3,5-DCP was calculated to be 10.9 mg/L (95% confidence limits 9.2 – 12.9 mg/L). These results show that the test was valid and that the sample of activated sludge employed was sensitive to inhibition. Concentration-related inhibition of respiration rates was seen at test substance concentrations greater than 2.4 mg/L. The highest tested concentration (80 mg/L) caused 85% inhibition. The EC50 of test substance was calculated to be 27.3 mg/L (95% confidence limits, 23.4 – 31.7 mg/L). The EC20 and EC80 values were calculated to be 10.9 and 68.3 mg/L, with 95% confidence limits of 8.1 – 14.1 and 54.8 – 87.5 mg/L, respectively.  Under study conditions, the 30 min EC50 of test substance for inhibition of respiration rate of activated sludge was found to be 27.3 mg/L (Barnes, 2007).