Sodium O-isobutyl dithiocarbonate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

There are conclusive but not suffcient data for the classification of substance Sodium isobutyl xanthate with regard to mutagenicity/genetic toxicity. It is concluded that the substance Sodium isobutyl xanthate does not meet the criteria to be classified for human health hazards for Mutagenicity-Genetic Toxicity

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate. In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

only 4 bacterial strains tested

Qualifier:

according to guideline

Guideline:

EPA OTS 798.5265 (The Salmonella typhimurium Bacterial Reverse Mutation Test)

Deviations:

no

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9 mix- rat liver, Aroclor 1254 administered

Test concentrations with justification for top dose:

0.005%, 0.01%, 0.025%, 0.05%, 0.1% v/v

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: none

Untreated negative controls:

yes

Negative solvent / vehicle controls:

no

Remarks:

no solvent/vehicle used

Positive controls:

yes

Positive control substance:

other: in the abscence and presence of metabolic activation: 2-aminoanthracene (TA1535), benzo[alpha]pyrene (TA1537, TA100, TA98); in the abscence of metabolic activation: sodium azide (TA1535, TA100), 9-aminoacridine (TA1537), 2-nitrofluorene (TA98);

Remarks:

dicloromethane in a vapour phase (7.5% v/v) was included in each test without metabolic activation

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

NUMBER OF REPLICATIONS:3/ treatment

DETERMINATION OF CYTOTOXICITY

- Method: abscence or thinning of the background lawn of non-revertant colonies

EXPOSURE TO CS2:
Sets of solidified plates were placed, with lids removed, in stainless steel racks, designed to keep the plates separate and permit atmospheric circulation, inside stainless steel vessels. These vessels were then sealed and partially evacuated. Calculated volumes of carbon disulphide liquid were injected into the vessels via a septum and allowed to vaporize, producing atmospheres containing carbon disulphide at the nominal concentrations
mentioned above.Sterile air was admitted to the vessels in order to equilibrate the contents to atmospheric pressure, and the vessels with their contents were incubated at 37°C for 48 hours. After removal from the vessels, the plates were incubated for a further day in order to permit revertant
colonies to grow to a size large enough to be scored.

Evaluation criteria:

number of revertants/plate

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: yes, only at the highest concentration

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Carbon disulphide was examined for its mutagenic activity in four histidine-dependent auxotrophs ofSalmonella typhimurium, strains TA98, TA100, TA1535, TA1537. Agar plates, seeded with the tester strains, were exposed to the test material in vapour phase, in the abscence and presence of metabolic activation, in the following nominal concentrations: 0.005%, 0.01%, 0.025%, 0.05% and 0.1% v/v (nominal). These concentrations were selected following preliminary toxicity tests in strain TA 98. Carbon disulphide did not exhibit any mutagenic activity under the conditions of this test. No increases in revertants were obtained in any of the four tester strains following exposure to carbon disulphide at the concentrations tested. Inhibition of bacterial growth, observed as thinning of the background lawn of non-revertant cells and reduction in revertant colony numbers, occurred in all strains with carbon disulphide at a nominal concentration of 0.1 % v/v. The positive and negative controls were valid.
The study was performed according to the OECD Guidelines for Testing of Chemicals No. 471 (1983) and US EPA (TSCA) Guideline § 798.5265 (1985, amended 1987).

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Conclusions:

Interpretation of results (migrated information):
negative

No mutagenic activity of CS2 detected.Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate.
In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

Executive summary:

Carbon disulphide was examined for its mutagenic activity in four histidine-dependent auxotrophs of Salmonella typhimurium, strains TA98, TA100, TA1535, TA1537. Agar plates, seeded with the tester strains, were exposed to the test material in vapour phase, in the abscence and presence of metabolic activation, in the following nominal concentrations: 0.005%, 0.01%, 0.025%, 0.05% and 0.1% v/v (nominal). These concentrations were selected following preliminary toxicity tests in strain TA 98. Carbon disulphide did not exhibit any mutagenic activity under the conditions of this test. No increases in revertants were obtained in any of the four tester strains following exposure to carbon disulphide at the concentrations tested. Inhibition of bacterial growth, observed as thinning of the background lawn of non-revertant cells and reduction in revertant colony numbers, occurred in all strains with carbon disulphide at a nominal concentration of 0.1 % v/v. The positive and negative controls were valid. The study was performed according to the OECD Guidelines for Testing of Chemicals No. 471 (1983) and US EPA (TSCA) Guideline § 798.5265 (1985, amended 1987).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

No mutagenic activity of CS2 detected in the reliable study of Akzo Chemicals International BV 1992.Carbon disulphide was examined for its mutagenic activity in four histidine-dependent auxotrophs of Salmonella typhimurium, strains TA98, TA100, TA1535, TA1537.Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate.

No mutagenic activity of Isobutyl Alcohol detectedin the reliable study of Kreja L, Seidel H-J 2002.. Isobutyl Alcoholwas examined for its mutagenic activity inChinese hamster lung fibroblasts (V79)cell line.

Isobutyl Alcohol is both reagents used in the manufacture, as well as decomposition products of Sodium isobutyl xanthate. Therefore, the health effects of Isobutyl Alcohol need to be considered in the assessment of sodium isobutyl xanthate. In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

 

No mutagenic activity of Isobutyl Alcohol detectedin the reliable study ofShimizu H, et al.1985. Isobutyl Alcoholwas examined for its mutagenic activity in Salmonella typhimurium, strains TA98, TA100, TA1535, TA1537, and TA1538 and E. coli WP2 uvr A.

 

Isobutyl Alcohol is both reagents used in the manufacture, as well as decomposition products of Sodium isobutyl xanthate. Therefore, the health effects of Isobutyl Alcohol need to be considered in the assessment of sodium isobutyl xanthate. In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

 

In the reliable study of Engelhardt, D. et al.2000, oral gavage dose of 500, 1,000 or 2,000 mg/kg of isobutanol in mouse did not have any chromosome-damaging (clastogenic) effect, and there were noindications of any impairment of chromosome distribution in the course of mitosis.

Isobutyl Alcohol is both reagents used in the manufacture, as well as decomposition products of Sodium isobutyl xanthate. Therefore, the health effects of Isobutyl Alcohol need to be considered in the assessment of sodium isobutyl xanthate. In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

No evidence of induced chromosomal or other damage leading to the formation of micronuclei in erythrocytes of the bone marrow was detected after exposure of the mouse to CS2 via inhalationin the reliable study of Akzo Chemicals International BV 1992..

Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate.

Justification for selection of genetic toxicity endpoint
Negative in all test conducted.

Justification for classification or non-classification

Based on the hazard assessment of Sodium isobutyl xanthate in section 2.1 and 2.2. in IUCLID 5.4., available data for the substance and following the “Guidance on Information Requirement and Chemical Safety Assessment R.8. Characterisation of dose [concentration]- response for human health” andaccording to the criteria described in Directive 67/548 and in the CLP Regulation:

 

Directive 67/548	Mutagenicity-Genetic Toxicity Muta. Cat. 1; R46 May cause heritable genetic damage. Muta. Cat. 2; R46 May cause heritable genetic damage. Muta. Cat. 3; R68 Possible risk of irreversible effects.
CLP	Germ cell mutagenicity Muta. 1A Muta. 1B Muta. 2 H340: May cause genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. H341: Suspected of causing genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.

 

 

It is concluded that the substance Sodium isobutyl xanthate does not meet the criteria to be classified for human health hazards for Mutagenicity-Genetic Toxicity