Phosphonic acid, monoethyl ester, sodium salt (1:1)

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:

21 Mar 2001

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

Qualifier:

according to guideline

Guideline:

other: Commission Directive 87/302/EEC: "Activated Sludge Respiration Inhibition Test", Official Journal of the European Communities No. L133/118-122, dated May 30, 1988.

GLP compliance:

yes (incl. QA statement)

Remarks:

Hessisches Ministerium für Umwelt, Landwirtschaft und Forsten

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

4545 mg test item (content of sodium ethyl phosphonate: 22.1% w/w) were filled up to 200 mL with deionized water to achieve a concentration of nominal 5 g/L of the active ingredient sodium ethyl phosphonate.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Origin: supplied by the sewage plant GroB-Zimmern, Germany
- Pretreatment: The sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3g dry material
per litre, were made up with tap water. The pH of the activated sludge was determined to be pH 7.8. To this mixture, 50 mL synthetic sewage feed per litre was added daily, starting one day prior to use, and the sludge was kept at room temperature under continuous aeration until use. Immediately before use, the dry weight of the activated sludge was determined, and diluted to 3g/L with tap water. The pH of the activated sludge was determined to be 7.8.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19 °C

pH:

7.3 - 8.4

Dissolved oxygen:

6.8 - 7.3 mg O2/L

Nominal and measured concentrations:

control, 10, 32, 100, 320, and 1000 mg/L (active ingredient: AE C529354, nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: glass flasks of approximately 1 litre volume filled with 500 mL test solution
- Aeration: with compressed air (approximately 0.6 litre per minute)
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Intervals of water quality measurement: The pH and the oxygen concentrations were determined at the start and at the end of the incubation period in all treatments. The water temperature was measured in one control medium at the start and the end of the incubation period.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: equivalent to EC50 >4524 mg AEC529354 technical concentrate 22.1%/L

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: equivalent to EC50 >4524 mg AEC529354 technical concentrate 22.1%/L

Details on results:

All results are based on concentrations of the active ingredient sodium ethyl phosphonate (content of 22.1% w/w in test item). In comparison to the inoculum controls the respiration rate of the activated sludge was not or only slightly inhibited by 0.4% to 7.1% up to the highest tested concentration of 1000 mg sodium ethyl phosphonate/L. Concentrations exceeding 1000 mg sodium ethyl phosphonate/L nominal were not tested.

Results with reference substance (positive control):

EC50 (3h) = 6.8 mg/L (95% CL: 4.4 - 9.5 mg/L)

Table 1: Influence of AE C529354; technical concentrate,based on active ingredient sodium ethyl phosphonate, on oxygen consumption of activated sludge

Flask	Treatment	Concentration of a.i. [mg/L]	Oxygen consumption [mg O2/L min]	Inhibition %	pH-values		Oxygen concentration [mg O2/L]
					start	end	start	end
1	Control	-	0.440	-	7.8	8.4	6.9	7.3
10	Control	-	0.463	-	7.7	8.4	7.0	6.8
Mean			0.452
% deviation			5
5	Test item	1000	0.450	0.4	7.3	8.3	6.9	7.2
6	Test item	320	0.440	2.7	7.3	8.3	7.0	7.3
7	Test item	100	0.450	0.4	7.3	8.3	7.0	6.9
8	Test item	32	0.420	7.1	7.4	8.4	6.9	7.1
9	Test item	10	0.430	4.9	7.4	8.4	7.0	6.8

Table 2: Validity criteria for OECD 209.

Criterion from the guideline	Outcome	Validity criterion fulfilled
The blank controls (without the test substance or reference substance) oxygen uptake rate should not be less than 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour.	The blank controls oxygen uptake rate was 22 and 23.15 mg O2 per gram dry weight of suspended solids in an hour	Yes
The coefficient of variation of oxygen uptake rate in control replicates should not be more than 30% at the end of definitive test.	The coefficient of variation of oxygen uptake rate in control replicates was 3.6%	Yes

 

Validity criteria fulfilled:

yes

Remarks:

see Table 2 in 'any other information on results incl. tables'

Description of key information

EC20 and EC50 (3 h) > 1000 mg a.i. (Fosetyl-Sodium)/L for activated sludge (OECD 209) (equivalent to >4524 mg Fosetyl-Sodium technical concentrate 22.1%/L)

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

A GLP study according to OECD 209 on toxicity to microorganisms was performed with Fosetyl-sodium (technical concentrate; 22.1%; Code: AE C529354 00 TK22 A101, containing 22.1% w/w Fosetyl-Sodium) under static conditions.

The study was designed to assess the toxicity of the test item to bacteria. The method assesses the effect on microorganisms by measuring the respiration rate under defined conditions in the presence of different concentrations of the test item. Mixed population of aquatic microorganisms (activated sludge) were exposed to Fosetyl-Sodium; technical concentrate at nominal concentrations of 10, 32, 100, 320 and 1000 mg test item/L. The respiration rate of each mixture was measured after an aerated incubation period of 3 hours. Two controls without test item were included in the test design, one at the start and the other at the end of the test series. Each batch of activated sludge is checked using 3.5-dichlorophenol as reference substance (tested rates: 3.2, 10 and 32 mg/L).

All results are based on concentrations of the active ingredient sodium ethyl phosphonate (content of 22.1 % w/w in test item). In comparison to the inoculum controls the respiration rate of the activated sludge was not or only slightly inhibited by 0.4% to 7.1% up to the highest tested concentration of 1000 mg/L. Based on measured inhibition rates, the 3-hour EC20 and EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg sodium ethyl phosphonate/L less than 20% inhibition was noted. Nevertheless, the 3-hour EC20 and EC50 are clearly higher than 1000 mg sodium ethyl phosphonate/L (equivalent to > 4524 mg Fosetyl-Sodium technical concentrate 22.1%/L) under the present test conditions.