Registration Dossier

Toxicological information

Genetic toxicity: in vitro

Currently viewing:

Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across based on grouping of substances (category approach)
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.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1980

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
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

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): n-pentane
- Substance type: C5 aliphatic
- Physical state: vapor
- Analytical purity: 98.7%
- Impurities (identity and concentrations): 0.6% cyclopentane, 0.4% isopentane, ~0.3% cis-pentane-2

Method

Target gene:
not reported
Species / strainopen allclose all
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 / 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:
50% , 25%, 10%, 8%, 5%, 2%, 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: no data
- Exposure duration: 6 hours
- Selection time (if incubation with a selection agent): 40 to 45 hours

SELECTION AGENT (mutation assays): histidine

NUMBER OF REPLICATIONS: no data

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 resultsopen allclose all
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: cytotoxic at concentrations of 25 and 50%
Vehicle controls validity:
not applicable
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1538
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
other: cytotoxic at concentrations of 25 and 50%
Vehicle controls validity:
not applicable
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
no data

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Because n-pentane was toxic at concentrations of 25 and 50%, 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. n-Pentane was toxic at concentrations of 25 and 50%, so additional tests were conducted to determine whether the compound was mutagenic at lower concentrations (1, 2, 5, 8 and 10%). Results show that n-pentane 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

n-Pentane

-

10

25

1

8

26

138

 

+

10

14

6

22

18

116

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

n-Pentane was not found to be mutagenic at any concentration after evaluation via an Ames test.
Executive summary:

The genetic toxicity in bacteria of n-pentane was evaluated via an Ames test. The statistical methods used were appropriate. The test conditions complied with the guideline requirements for this study type. 

 

n-Pentane 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 no information regarding GLPs was 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.