tert-pentyl 2-ethylperoxyhexanoate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Details on sampling:

A sample of each mixture is poured into a BOD bottle (following the order of preparation). An oxygen electrode is inserted into the bottle. The oxygen concentration is measured every minute during a period of 10 min.

Vehicle:

no

Details on test solutions:

N-Allylthiourea solution
Following the guideline, a 2.32 g/L solution of N-allylthiourea (ATU) was prepared. Addition of 2.5 mL of this solution into a final volume of 500 mL gives a final concentration of 11.6 mg/L (0.1 mM) of ATU known to be sufficient to cause 100 % inhibition of 1.5 g/L of suspended solids.

Introduction of the test item
The test item was directly introduced into the flasks, as its low solubility did not allow preparation of a stock solution.


Nitrification inhibitor (ATU):
Chemical name: N-Allylthiourea
CAS number: 109-57-9
EC number: 203-683-5
Date of reception in the test facility: 03/01/11
Expiration date of the test item: 03/01/11
Batch number/supplier: 10J130009 / VWR
Characteristics: white to light yellow crystals
Empirical formula: C4H8N2S
Purity: 99 %
Molecular weight: 116.18 g/mol.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The inoculum comes from the activated sludge of the biological domestic wastewater treatment plant from Abidos. The effluent, obtained one days before seeding the flasks, is centrifuged at approximately 20 °C for 10 min at 1000 g; the base is re-suspended in ultra-pure water in order to keep the concentration unchanged with respect to the sample. The amount of dry material in the inoculum, is determined by dessiccation at 105 °C until a constant weight. From this result the amount of wet sludge can be calculated in order to obtain an activated sludge with a mixed liquor suspended solids level of 4 g/L (+/- 10%). The inoculum is preconditioned (aeration). Every day, synthetic sewage feed are added until the day the flasks are inoculated.

Value of suspended solids was 5.11 g/L. Then a dilution was performed to obtain 3 g/L. This level corresponds to a concentration of 1.5 g/L in the final test medium.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

incubated at 20 +/- 2 °C

Dissolved oxygen:

The dissolved oxygen concentrations are determined electrochemically using an oxygen electrode (WTW Stirrox G) and meter (WTW OXI 538).

Nominal and measured concentrations:

The test item was directly introduced into the flasks in order to obtain concentrations from 50 to 1000 mg/L (50, 105.7, 223.6, 472.9 and 1000 mg/L) with a factor of 2.11.

Details on test conditions:

The tests are carried out in 500 mL flasks, with the following repartition:
- 16 ml of synthetic sewage feed
- adequate volume of test item and ultra-pure water for different concentrations
- 250 ml of sludge suspension

At T0, the first control (control1) without item is prepared. Then every 15 min. the others vessels with different concentrations of item are prepared in turn. Finally, the second control (control 2) is prepared.

All suspensions are aerated and stirred during 3 hours and incubated at 20 +/- 2 °C without light. Then a sample of each mixture is poured into a BOD bottle (following the order of preparation). An oxygen electrode is inserted into the bottle. The oxygen concentration is measured every minute during a period of 10 min.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

480 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Details on results:

See tables below.
EC10 were also determined, however calculations are considered not reliable.

Results with reference substance (positive control):

See tables below

TERT-AMYL PEROXY-2-ETHYLHEXANOATE INHIBITION RATE

 

Nominal concentrations (mg/L)	T0	T = 180 (min.)	Taux de respiration (O2 mg/L/h)	% inhibition
Control 1	7,4	1,1	47,3	-
Control 2	7,5	1,4	45,8	-
50	7,5	1,3	41,3	11,1
105,7	7,5	1,5	40,0	14,0
223,6	7,3	1,2	40,7	12,5
472,8	7,3	1,4	39,3	15,4
1000	7,6	2,1	36,7	21,1

 

 

TERT-AMYL PEROXY-2-ETHYLHEXANOATE + ATU INHIBITION RATE Oxygen measurements (mg O2 /L) at 3 hours

 

Nominal concentrations (mg/L)	T0	T = 180 (min.)	Taux de respiration (O2 mg/L/h)	% inhibition
Control 1	7,8	2,3	36,7	-
Control 2	7,5	1,7	38,7	-
50	7,6	2,2	36,0	4,4
107,5	7,6	2,2	36,0	4,4
223,6	8,0	3,1	32,7	13,3
472,8	7,4	2,0	36,0	4,4
1000	7,8	2,8	33,3	11,5

Respiration rates recapitulation and EC50 for3 ,5-dichlorophenol

	Total Respiration without ATU		Heterotrophic Respiration with ATU		Nitrification Respiration by difference
Control	TR mg/L.h	CV %	HR mg/L.h	CV %	NR mg/L.h	CV %
C1	46,3		60,0		-13,7
C2	47,3	1,5	60,9	1,1	-13,6	-
Mean	46,8		60,5		-13,7
DCP (mg/L)	TR mg/L.h	% Inh.	HR mg/L.h	% Inh.	NR mg/L.h	% Inh.
0,098	44,0	6,0	59,1	2,2	-15,10
0,439	44,0	6,0	59,1	2,2	-15,10
1,975	38,4	17,9	59,1	2,2	-20,70	-
8,889	31,2	33,3	42,0	30,5	-10,80
40	7,2	84,6	9,3	84,6	-2,10
	Total Respiration		Heterotrophic Respiration		Nitrification Respiration
EC50 (mg/L)	9,80		15,0		ND

Respiration rates recapitulation, EC50 for TERT-AMYL PEROXY-2-ETHYLHEXANOATE

 

	Total Respiration without ATU		Heterotrophic Respiration with ATU		Nitrification Respiration by difference
Control	TR mg/L.h	CV %	HR mg/L.h	CV %	NR mg/L.h	CV %
C1	47,3		36.7		10.6
C2	45,8	2.3	38.7	3.8	7.1	28.0
Mean	46,6		37.7		8.8
Luperox 575 (mg/L)	TR mg/L.h	% Inh.	HR mg/L.h	% Inh.	NR mg/L.h	% Inh.
50	41,3	11,3	36,0	4,5	5,30	0,00
105,7	40,0	14,1	36,0	4,5	4,00	54,80
223,6	40,7	12,6	32,7	13,3	8,00	9,60
472,8	39,3	15,6	36,0	4,5	3,30	62,71
1000	36,7	21,2	33,3	11,7	3,40	61,58
	Total Respiration		Heterotrophic Respiration		Nitrification Respiration
EC50 (mg/L)	> 1000		> 1000		480

Validity criteria fulfilled:

yes

Conclusions:

EC50 for the test item was determined to be higher than the highest tested concentration: EC50 > 1000 mg/L

Executive summary:

The purpose of this study was to determine the effect of the test item on bacteria according to the OECD guideline 209 “Activated Sludge, Respiration Inhibition Test”. The effect is assessed by measuring the micro-organisms respiration rates on a sample of activated sludge during an incubation period of 3 hours. Three respiration rates were evaluated : total respiration rate, heterotrophic respiration rate (in presence of N-Allylthiourea) and nitrification respiration rate by difference between total and heterotrophic respiration rates.

EC50 of the reference item 3,5-dichlorophenol was 9.8 mg/L, between 2 and 25 mg/L for total respiration;15 mg/L, between 5 and 40 mg/l for heterotrophic respiration, but could not be determined for nitrification respiration.

EC50 for the test item was determined to be higher than the highest tested concentration: EC50 > 1000 mg/L

Description of key information

OECD 209, GLP, key study, validity 1:
EC50> 1000 mg/L
 

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

The toxicity of TERT-AMYL PEROXY-2-ETHYLHEXANOATE to microorganism was estimated in a study performed according to OECD 209 guideline and GLP requirements. EC50 for the test item was determined to be higher than the highest tested concentration: EC50 > 1000 mg/L