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

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 October 2017 to 21 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 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

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 no.: 10013913; purity: > 99.9 %, according to certificate of analysis

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Details on test solutions:

A stock solution of 100 mg test item/L was prepared by dissolving 100 mg test item into 1000 mL test water by intense stirring for 10 minutes. Adequate volumes of this stock solution were diluted with test water to prepare the test media of the desired test concentrations: 100, 45.5, 20.7, 9.4, 4.3, 1.9 and 0.9 mg test item/L. In the control, test water was used without addition of the test item.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

Female Daphnia magna (Straus), clone 5, of 2.25 to 18.75 hours of age was used for the test. The daphnids were bred in the testing facility under similar temperature and light conditions as used in the test. The daphnids in the stock culture were fed at least on all working days with green algae (Desmodesmus subspicatus) freshly grown. The cultivation of the parental daphnids was performed in Elendt M4 medium. Acclimatisation was not necessary, since the test was performed in the same medium as the culturing. The test organisms were not first brood progen and were not fed during the study period.

Study design

Test type:

static

Water media type:

other: Elendt M4 medium

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

2.5 mmol/L (= 250 mg/L) as CaCO3

Test temperature:

20.0 to 20.1 °C at test start; 19.5 °C at test end

pH:

7.4 to 8.7 at test start; 7.9 to 8.0 at test end

Dissolved oxygen:

9.3 to 9.7 mg/L at test start; 9.2 to 9.4 mg/L at test end

Nominal and measured concentrations:

100, 45.5, 20.7, 9.4, 4.3, 1.9 and 0.9 mg test item/L, and a control with Elendt M4 medium only.

Details on test conditions:

Pre-experiments were performed to determine a suitable concentration range and to establish suitable methods to prepare the test solutions. Glass beakers of 100 mL volume containing approximately 60 mL of test medium. The test vessels were covered with a lid to reduce the loss of water due to evaporation and to avoid the entry of dust into the solutions. The water temperature, pH-values and dissolved oxygen concentrations were determined at test start and test end in each treatment group. Twenty daphnids were introduced per control and test concentration, divided into 4 groups of 5 animals, each group in 60 mL test medium. The mobility of the daphnids was determined by visual observation after 24 and 48 hours. Those animals that are not able to swim within 15 seconds after gentle agitation of the test beaker were considered to be immobile (even if they could still move their antennae).

Reference substance (positive control):

yes

Remarks:

The reference item potassium dichromate is tested at least twice a year in the testing facility to demonstrate satisfactory test conditions.

Results and discussion

Effect concentrations

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.33 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% CI not determinable

Details on results:

After 48 hours of exposure no immobilisation of the test animals was observed in the control. At the lowest test concentration of 0.9 mg test item/L one daphnid was immobile. Three daphnids were immobile at 1.9 mg test item/L. Beginning with 4.3 mg and up to 100 mg test item/L all daphnids were immobile. The 48-hour NOEC was determined to be 0.9 mg test item/L and the 48-hour LOEC was determined to be 1.9 mg test item/L. The 48-hour EC10, EC20 and EC50 values were calculated to be 1.44, 1.702 and 2.33 mg test item/L respectively. The confidence intetrvals for these endpoints could not be determinable. All reported results refer to nominal values since the concentrations of the test item were within ± 20% of the nominal concentrations during the test. At the start of the test, 106% of the nominal test concentrations were found (average of all test concentrations). After 48 hours test duration, 104% of the nominal value was determined (average of the nominal concentrations of 20.7, 9.4, 4.3, 1.9 and 0.9 mg test item/L), and so during the test the daphnids were exposed to a mean of 105% of nominal.

Results with reference substance (positive control):

In the most recent study performed at the testing facility, nominal concentrations of 0 (control), 0.125, 0.25, 0.5, 1.0 and 2.0 mg potassium dichromate/L were used. The resulting 24-h EC50 value was determined to be 1.48 mg test item/L, indicating that the sensitivity of the daphnids was consistent with the level proposed by the OECD 202 guideline.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The 48-hour EC10, EC20 and EC50 values were calculated to be 1.44, 1.702 and 2.33 mg test item/L respectively. The confidence intetrvals for these endpoints could not be determinable. The initial concentrations and the maintenance of the exposure concentrations during the test were verified. All reported results refer to nominal values since the concentrations of the test item were within ± 20% of the nominal concentrations during the test.

Executive summary:

The toxic effect of the test item 2 -methyl-4 -isothiazolin-3 -one hydrochloride to Daphnia magna was assessed in a 48 hours static concentration-response test. Nominal test concentrations of 100, 45.5, 20.7, 9.4, 4.3, 1.9 and 0.9 mg test item/L and a control (Elendt M4 only) were tested based on the results of a range-finding study. Twenty daphnids were introduced per control and test concentration, divided into 4 groups of 5 animals per test vessel. The water temperature, pH-values and dissolved oxygen concentrations were determined at test start and test end in each treatment group and the mobility of the daphnids was determined by visual observation after 24 and 48 hours of exposure. The initial concentrations and the maintenance of the exposure concentrations during the test were verified. All reported results refer to nominal values since the concentrations of the test item were within ± 20% of the nominal concentrations during the test.

The 48-hour EC10, EC20 and EC50 values were calculated to be 1.44, 1.702 and 2.33 mg test item/L respectively. The confidence intetrvals for these endpoints could not be determinable. The 48-hour NOEC was determined to be 0.9 mg test item/L and the 48-hour LOEC was determined to be 1.9 mg test item/L.