2-methyl-2H-isothiazol-3-one hydrochloride

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 24 July 2017 to 20 December 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-Methyl-4-Isothiazolin-3-One Hydrochloride

Cas Number:

26172-54-3

Molecular formula:

C4H5NOS.HCl

IUPAC Name:

2-Methyl-4-Isothiazolin-3-One Hydrochloride

Test material form:

solid

Details on test material:

Analytical grade is identical to the technical grade

Specific details on test material used for the study:

Batch: 10013913
Purity: > 99%
Expiry date: 30 November 2018

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Source: Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK (aeration stage).
Preparation of inoculum for exposure: Washed twice by settlement and re-suspension in mineral medium (to remove any excessive amounts of dissolved organic carbon).
Pretreatment: Washed sample maintained on continuous aeration in the laboratory at a temperature of approximately 21°C and used on day of collection.
Concentration of sludge: 30 mg/L.

Duration of test (contact time):

29 d

Initial test substance concentration

Initial conc.:

31.6 mg/L

Based on:

test mat.

Remarks:

equivalent to 10 mg carbon/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium prepared as recommended in OECD 301 Guideline.
- Test temperature: Between 22 and 24°C.
- pH: 7.4.
- pH adjusted: Yes.
- Aeration of dilution water: Yes (CO-free air).
- Suspended solids concentration: 30 mg/L.
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 2 / 31.6 mg/L
- Method used to create aerobic conditions: CO2-free air bubbled through at 30 to 100 mL/min and stirred continuously by magnetic stirrer.
- Details of trap for CO2: Two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH.
- Measuring equipment: Shimadzu TOC analyzers.

SAMPLING
- Sampling frequency: CO2 absorber sampled on days 0, 2, 6, 8, 10, 14, 21, 28 and 29.
- Sample storage before analysis: Analysed immediately.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes (duplicate).
- Abiotic sterile control: No.
- Toxicity control: Yes.
- Procedure control: Yes, (duplicate).

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

Preliminary investigational work indicated that the test item did not adsorb to filter matrices or to activated sewage sludge.

Test performance:

No unusual observations.

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

28 d

Details on results:

All validation criterion given in the OECD Test Guideline 301B were satisfied: The total CO2 evolution in the inoculum control vessels on Day 28 was 33.80 mg/L. The IC content of the test item suspension in the mineral medium at the start of the test was below 5% of the TC content. The difference between the values for CO2 production at the end of the test for the replicate vessels was < 20%.

The test item attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Test Guideline 301B. However, care should be taken in the interpretation of these results as the test item was considered to have exhibited an inhibitory effect at the test concentration employed in the study (10 mg carbon/L) as the toxicity control vessel did not pass the validation criteria.

BOD5 / COD results

Results with reference substance:

Sodium benzoate attained 69% biodegradation after 14 and 28 days thereby confirming the suitability of the inoculum and test conditions.

Any other information on results incl. tables

Percentage biodegradation values in CO₂evolution test

Time (days)	% Biodegradation
	Test item	Procedure control	Toxicity control
0	0	0	0
2	0	23	0
6	0	37	1
8	0	70	0
10	0	83	0
14	0	69	0
21	0	78	0
28	0	78	0
29*	0	69	0

* Day 29 values corrected to include any carry-over of CO₂detected in absorber 2

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Test Guideline 301B. However, care should be taken in the interpretation of these results as the test item was considered to have exhibited an inhibitory effect at the test concentration employed in the study (10 mg carbon/L).

Executive summary:

A study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium. The test item, at a concentration of 10 mg carbon/L (the lowest concentration recommended for OECD 301B) , was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at 22 to 24°C for 28 days. The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

The test item attained 0% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Test Guideline 301B. However, care should be taken in the interpretation of these results as the test item was considered to have exhibited an inhibitory effect at the test concentration employed in the study as the toxicity control vessel did not pass the validation criteria for the test item to be considered non-inhibitory.