Zinc di(benzimidazol-2-yl) disulphide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

Please refer to attached QMRF and QPRF Documents

Principles of method if other than guideline:

Calculation of toxicity in Algae. Software used: ECOSAR 1.11 (EPISUITE) for chemical class "Imidazols"

GLP compliance:

no

Specific details on test material used for the study:

SMILES: c12nc(S)nc1cccc2

Analytical monitoring:

not required

Test organisms (species):

other: Algae

Water media type:

freshwater

Total exposure duration:

96 h

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.214 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: EC50 (acute value, QSAR)

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.205 mg/L

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: ChV (chronic value, QSAR)

Conclusions:

Using ECOSAR v1.11 the short- (EC50) and long-term (NOEC) toxicity values for algae were calculated to be 0.214 mg/L and 0.205 mg/L, respectively. The substance is within the applicability domain of the model.

Executive summary:

Using ECOSAR v1.11 the short- (EC50) and long-term (NOEC) toxicity values for algae were calculated to be 0.214 mg/L and 0.205 mg/L, respectively. The substance is within the applicability domain of the model.

The adequacy of a prediction depends on the following conditions:

a) the (Q)SAR model is scientifically valid: the scientific validity is established according to the OECD principles for (Q)SAR validation;

b) the (Q)SAR model is applicable to the query chemical: a (Q)SAR is applicable if the query chemical falls within the defined applicability domain of the model;

c) the (Q)SAR result is reliable: a valid (Q)SAR that is applied to a chemical falling within its applicability domain provides a reliable result;

d) the (Q)SAR model is relevant for the regulatory purpose.

 

For assessment and justification of these 4 requirements the QMRF and QPRF files were developed and attached to this study record.

Description of the prediction Model

The prediction model was descripted using the harmonised template for summarising and reporting key information on (Q)SAR models. For more details please refer to the attached QSAR Model Reporting Format (QMRF) file. 

 

Assessment of estimation domain

The assessment of the estimation domain was documented in the QSAR Prediction Reporting Format file (QPRF). Please refer to the attached document for the details of the prediction and the assessment of the estimation domain.

Description of key information

In this 72-h algal growth inhibition test with Raphidocelis subcapitata, the obtained results showed that the test item Zinc di(benzimidazol-2-yl) disulphide had significant toxic effects on the growth of Raphidocelis subcapitata. The 72-h EC10, EC20, EC50 for growth rate were determined to be 0.008, 0.014 and 0.034 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.034 mg/L

EC10 or NOEC for freshwater algae:

0.008 mg/L

Additional information

A Growth Inhibition Test according to OECD guideline 201 was conducted to determine the effect of the test item Zinc di(benzimidazol-2-yl) disulphide on the growth of the unicellular green algae species Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata) (TOXICOOP, 2018). Exponentially growing cultures of Raphidocelis subcapitata were exposed to nominal test item concentrations of 0.014, 0.041, 0.12, 0.37, 1.11, 3.33 and 10.0 mg/L. The analytically measured test item concentrations were not within the range of ± 20 % of the nominal over the test period of 72 hours. Therefore, exposure concentrations were calculated as the geometric mean of the measured concentrations. Corresponding calculated geometric mean measured concentrations were: 0.003, 0.005, 0.01, 0.06, 0.54, 2.26 and 7.27 mg/L. Concurrent control ran parallel in the test. The algal growth in relation to the untreated control culture was determined over a fixed test period of 72 hours and thus, over several algal generations. The 72-h EC10, EC20, EC50 for growth rate were determined to be 0.008, 0.014 and 0.034 mg/L, respectively. The 72-h LOEC values based on growth rate was determined to be 0.01 mg/L. The 72-h NOEC for growth rate was determined to be 0.005 mg/L. All validity criteria were met. The results are based on measured geometric mean test item concentrations.

A QSAR calculation using ECOSAR v1.11 determined short- (EC50) and long-term (NOEC) toxicity values for algae were calculated to be 0.214 mg/L and 0.205 mg/L, respectively.