Carbamodithioic acid, bis(mixed 2-ethylhexyl and 2-methylbutyl and pentyl) derivs., antimony (3+) salts

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Not Specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Justification for type of information:

JUSTIFICATION FOR WEIGHT OF EVIDENCE APPROACH: Analytical techniques sensitive enough to quantify test concentrations at the extremely low levels of solubility and predicted aquatic toxicity of the parent compound and/or possible degradation products are not available for this multi-constituent substance. Thus, a weight-of-evidence approach using read-across to a closely related compound and a valid QSAR model is considered sufficient to conclude the substance is expected to be very toxic to aquatic life.

JUSTIFICATION FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

The source chemical (ferbam) is an acceptable analog to represent the aquatic toxicity of the target chemical (tris[t-ethylhexl and/or 2-methylbutyl and/or pentyl(linear and branched)dithiocarbamoto-S,S']antimony(III)) since both substances are trivalent metal salts of dialkyldithiocarbamates and are expected to cause aquatic toxicity by the same mode of action.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

The source chemical and the target chemical are both trivalent metal salts of dialkyldithiocarbamates, with the former being a mono-constituent substance and the latter being a multi-constituent substance. This difference is not, however, expected to impact the validity of the analog approach.

3. ANALOGUE APPROACH JUSTIFICATION

A mode of action common to all dialkyldithiocarbamates, particularly those that are hydrophobic, is that these molecules are simply a way to bring carbon disulfide or reactive elementary sulphur to the site of action and interfere with metallo-enzymes (Aquatic Toxicology, 7 (1985) 145-164), resulting in inhibition of metabolism at various sites and in various processes. Given this mode of action, neither the iron present in the source chemical nor the antimony present in the target chemical are expected to participate in or differentially impact the aquatic toxicity of any reactive species that might be present.

4. DATA MATRIX

Water solubility and octanol-water partition coefficient (Kow) are of greatest importance with regards to aquatic toxicity of dialkyldithiocarbamates. With regards to these parameters, the two substances do differ, with the source chemical being more water soluble and possessing a lower Kow than the target chemical. Van Leeuwen, et. al. (Aquatic Toxicology, 7 (1985) 145-164) describe a relationship of increasing toxicity with increasing Kow, but excluded substances from their calculations which had Kow's so high and water solubilities so extremely low that the substance could not be tested with Daphnia magna because the neonates stuck to the organic surface layer formed, and died as a consequence, with no mortality otherwise observed. Thus, the toxicity of the source chemical can be considered representative of that portion of the soluble portion of the target chemical or its possible reactive degradation products.

Data source

Reference

Title:

Unnamed

Year:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Principles of method if other than guideline:

The assay was conducted in a temperature controlled room at 20 + 1 °C. The test solutions with an initial cell density of approximately 10E08 cells per 100 ml were added to 200 ml Erlenmeyer flasks, which were stoppered with a cotton plug and placed on a mechanical shaker under fluorescent light. The cells were counted in a model ZBI Coulter Counter, using a 70 micron aperture. The tests were carried out in triplicate. The composition of the medium used is given in Env. Pollut. (Series A), 37 (1985) 105-115.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Ferbam

EC Number:

238-484-2

EC Name:

Ferbam

Cas Number:

14484-64-1

Molecular formula:

C9H18FeN3S6

IUPAC Name:

iron(3+) tris(dimethyldithiocarbamate)

Details on test material:

Supplied by ICN

Specific details on test material used for the study:

Substance Name: Ferric dimethyldithiocarbamate (ferbam)
Purity: >95%

Sampling and analysis

Analytical monitoring:

not specified

Details on sampling:

No Data

Test solutions

Vehicle:

yes

Remarks:

Dimethylsulphoxide or Acetone

Test organisms

Test organisms (species):

Chlorella pyrenoidosa

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test conditions

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

2.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.33 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: toxicity to the inoculum

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The acute aquatic toxicity (96-hour EC50) of the read-across substance (ferbam) on Chlorella pyrenoidosa was 2.4 mg/L (growth rate) and 0.33 mg/L (toxicity to the inoculum), indicating that the substance is very toxic.

Executive summary:

In an OECD 201 Guideline study (GLP status not reported), the acute aquatic toxicity (96-hour EC50) of the read-across substance (ferbam) in Chlorella pyrenoidosa was 2.4 mg/L (growth rate) and 0.33 mg/L (toxicity to the inoculum), indicating that the substance is very toxic.