1,2,4-triazole-3-thiol

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

The following deviations from the guideline were documented:
• Partly the flasks for IC measurement were not measured directly, they were stored in the fridge at 5.6 - 9.6 °C instead of 4 °C. The flasks are closed and CO2 content can-not change. This is considered as uncritical concerning the outcome of the study.
• Temperature range was 19.2 – 20.5 °C instead of 20.0 – 24.0 °C. As degradation of the positive control was in the normal range this is considered as uncritical concerning the outcome of the study.

Deviations:

yes

Remarks:

see Version/ remarks

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

1,2,4-triazole-3-thiol

EC Number:

221-656-6

EC Name:

1,2,4-triazole-3-thiol

Cas Number:

3179-31-5

Molecular formula:

C2H3N3S

IUPAC Name:

4H-1,2,4-triazole-3-thiol

Test material form:

solid: crystalline

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, 67435 NW-Lachen-Speyerdorf.
Date of collection: 09. Aug. 2019, batch no: E20190809.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

84.3 mg/L

Based on:

test mat.

Details on study design:

Sampling
From each front scrubber flask, 10 samples were taken in order to determine the emitted CO2 (on day 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The result-ing change in the volume of the front flask was considered in the calculation of emitted CO2 (see also chapter 8.3.1).
On day 28, 5 mL HCl 2 M was added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.
CO2 Determination
Analyses of the emitted CO2 were made by IC measurement using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each sample was measured in duplicate or triplicate, respectively (depending on the variation between the measured values). The carbon analyser was calibrated with freshly prepared reference solutions containing potassium hydro-gen phthalate (TC), sodium hydrogen carbonate and sodium carbonate (IC). Quality control samples were measured daily.

Reference substance

Reference substance:

aniline

Results and discussion

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

5.4

Sampling time:

28 d

Any other information on results incl. tables

1.1.1    Degradation Values

In the following table, the percentage biodegradation is presented:

Table8.3‑b     Degradation values in %

Day	Positive Control 1	Positive Control 2	Positive Control Mean	Test 1	Test 2	Test Mean	Abiotic Control	Toxicity Control
2	-0.1	0.1	0.0	0.8	1.6	1.2	0.2	0.6
4	19.6	2.5	11.1	1.4	2.0	1.7	0.6	15.0
7	50.5	48.5	49.5	2.4	2.9	2.6	0.4	39.8
9	67.2	63.8	65.5	3.3	3.6	3.5	0.7	44.5
11	79.3	70.5	74.9	3.5	3.5	3.5	0.6	44.0
14	91.7	87.5	89.6	3.9	2.9	3.4	0.5	45.0
18	95.7	90.9	93.3	3.9	4.6	4.3	0.5	43.0
23	106.7	104.7	105.7	3.3	4.2	3.8	-0.4	45.6
29	104.7	102.9	103.8	4.6	6.1	5.4	0.0	42.2

 

Because the values of day 29 are the sum of the IC values in both scrubber flasks, an increase (IC values in flasks B of the test higher than in those of the control) or a decrease (IC values in flasks B of the test lower than in those of the control) of degradation can be observed.

As the measured IC values in the abiotic control are very low, measurement uncertainties lead to negative degradation values while in fact no degradation has taken place.

1.1     Validity

All validity parameters and values are presented in the following table:

Table9.2‑a     Validity

Parameter	Criterion	Found	Assessment
IC content of test item solution in medium	< 5% of TC	0.36 %	valid
CO2emitted by the controls	< 70 mg/L	5.7 mg/L	valid
Difference within replicates	< 20%	1.5 %	valid
Degradation of positive control > 60%	≤14 days	8 days	valid
Degradation in the toxicity flask on day 14	> 25%	45.0 %	non - toxic

 

 

 

 

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

All validity criteria were met.
Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test item showed very good correspondence.
Degradation values of more than 100 % were calculated. This is due to the fact that the measurement errors of test flasks and control flasks add up when using the equation proposed in the guideline.
As degradation in the toxicity flask was 45.0 % after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 84.3 mg/L”.
Ready biodegradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10 %. Therefore, the test item 3-Mercapto-1,2,4-triazole can be considered as “not readily biodegradable”. Degradation missed the pass level of 60 % within 28 days, though. Therefore, the test item is considered as “not ultimately biode-gradable within 28 days”, as well
No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.

Executive summary:

The test item3-Mercapto-1,2,4-triazolewas tested using a concentration of nominally 20 mg organic carbon/L3-Mercapto-1,2,4-triazolein test medium following OECD 301B and EU-Method C.4-C.

 

Aniline was chosen as positive control.

Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.

All validity criteria were met. Degradation of the positive control surpassed the pass level of 60 % after 8 days.

 

The following data were determined for the test item3-Mercapto-1,2,4-triazole:

10-day-window:                                                         not detected
degradation at the end of 10-day-window                              none
degradation at the end of the test                                            5 %
pass level following guideline:60 % at the end of 10-day-window for pure substances

                         respective 60 % at the end of the test for mixtures

 

Therefore, when applying the 10-day-window, the test item3-Mercapto-1,2,4-triazole is not readily biodegradable following OECD 301B and EU C.4-C respectively. As degradation missed the pass level of 60% in the course of the test, 3-Mercapto-1,2,4-triazoleis considered as not ultimately biodegradable , as well.