Cyclopentane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable with restrictions because no information regarding GLPs was provided; however, the study closely followed OECD 471 and EEC B.13/14.

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable with restrictions because no information regarding GLPs was provided; however, the study closely followed OECD 471 and EEC B.13/14.

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

reference to other study

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS: not reported

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Because 2-methylbutane was somewhat toxic at concentrations of 10% and above, additional tests were conducted at lower concentrations to determine mutagenicity.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

The results of the Ames test with the highest non-toxic dose are presented below. The positive control was mutagenic in strains TA98 and TA100, and was slightly mutagenic in strain TA1535. 2 -methylbutane was somewhat toxic at concentrations of 10% and above, so additional tests were conducted to determine whether the compound was mutagenic at lower concentrations (1, 2, 5, and 8%). Results show that 2 -methylbutane is not mutagenic at the lower concentrations.

Compound	Metabolic activation	Concentration of Gas in the Desiccator (V/V) %	Average histidine revertants per plate
			TA1535	TA1537	TA1538	TA98	TA100
Negative control	-		15	12	10	29	138
	+		16	18	30	38	155
Positive control (methylene chloride)	-	2	34	10	16	234	900
	+	2	52	12	52	237	1066
2 -methylbutane	-	10	22	3	14	15	124
	+	10	10	6	16	22	124

Conclusions:

Interpretation of results: negative

2-methylbutane was not found to be mutagenic at any concentration after evaluation via an Ames test.

Executive summary:

This data is being read across from the source study that tested 2-methylbutane based on analogue read across.

The genetic toxicity in bacteria of 2 -methylbutane was evaluated via an Ames test. 2 -methylbutane was not found to be mutagenic at any concentration in both the presence and absence of S9 mix. This study is classified as reliable with restrictions, Klimisch score 2, because information regarding GLPs was not provided. However, the study closely followed OECD 471 and EEC B.13/14. The standard plate test was modified due to the gaseous nature of the chemicals; these modifications did not affect the overall study results. One of the strains used (TA1538) is not included in the current Guidelines, and only data from the highest dose was presented in the study report. 

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1980

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

Ames test was modified for the gaseous chemical (did not affect results); strain TA1538 is not included in current Guidelines; only data from highest dose presented

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

2-methylbutane

EC Number:

201-142-8

EC Name:

2-methylbutane

Cas Number:

78-78-4

Molecular formula:

C5H12

IUPAC Name:

isopentane

Details on test material:

- Name of test material (as cited in study report): isopentane
- Substance type: C5 aliphatic
- Physical state: vapor
- Analytical purity: 97.2%
- Impurities (identity and concentrations): 2.8% n-pentane

Method

Target gene:

not reported

Species / strain

Species / strain 1

Species / strain / cell type:

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

Additional strain / cell type characteristics:

other: histidine auxotrophs

Species / strain 2

Species / strain / cell type:

S. typhimurium TA 1538

Additional strain / cell type characteristics:

other: histidine auxotrophs

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-stimulated S9 mix

Test concentrations with justification for top dose:

10% v/v
8% v/v
5% v/v
2% v/v
1% v/v

Vehicle / solvent:

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

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

no

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: methylene chloride

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Preincubation period: not reported
- Exposure duration: 6 hours
- Selection time (if incubation with a selection agent): 40 to 45 hours

SELECTION AGENT (mutation assays): histidine

NUMBER OF REPLICATIONS: not reported

OTHER: The number of his+ revertants on each plate was counted and recorded.

Evaluation criteria:

The number of his+ revertants on each plate was counted and compared to the controls to determine mutagenicity.

Statistics:

not reported

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: cytotoxic at concentrations of 10% and above

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS: not reported

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Because 2-methylbutane was somewhat toxic at concentrations of 10% and above, additional tests were conducted at lower concentrations to determine mutagenicity.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

The results of the Ames test with the highest non-toxic dose are presented below. The positive control was mutagenic in strains TA98 and TA100, and was slightly mutagenic in strain TA1535. 2 -methylbutane was somewhat toxic at concentrations of 10% and above, so additional tests were conducted to determine whether the compound was mutagenic at lower concentrations (1, 2, 5, and 8%). Results show that 2 -methylbutane is not mutagenic at the lower concentrations.

Compound	Metabolic activation	Concentration of Gas in the Desiccator (V/V) %	Average histidine revertants per plate
			TA1535	TA1537	TA1538	TA98	TA100
Negative control	-		15	12	10	29	138
	+		16	18	30	38	155
Positive control (methylene chloride)	-	2	34	10	16	234	900
	+	2	52	12	52	237	1066
2 -methylbutane	-	10	22	3	14	15	124
	+	10	10	6	16	22	124

Applicant's summary and conclusion

Conclusions:

Interpretation of results: negative

2-methylbutane was not found to be mutagenic at any concentration after evaluation via an Ames test.

Executive summary:

The genetic toxicity in bacteria of 2 -methylbutane was evaluated via an Ames test. 2 -methylbutane was not found to be mutagenic at any concentration in both the presence and absence of S9 mix. This study is classified as reliable with restrictions, Klimisch score 2, because information regarding GLPs was not provided. However, the study closely followed OECD 471 and EEC B.13/14. The standard plate test was modified due to the gaseous nature of the chemicals; these modifications did not affect the overall study results. One of the strains used (TA1538) is not included in the current Guidelines, and only data from the highest dose was presented in the study report.