2,2,4-trimethylpentane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

There is in vitro genetic toxicity data available for 2,2,4-trimethylpentane. Additionally, data is available for structural analogue heptane and presented in the dossier. This data is read across to 2,2,4-trimethylpentane based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

The genetic toxicity tests listed below had negative results for 2,2,4 -trimethylpentane.

 

Genetic Toxicity in vitro – Bacterial reverse mutation assay (OECD 471)

Genetic Toxicity in vitro – Mammalian Chromosome Aberration Test (OECD TG 473)

Genetic Toxicity in vitro – Mammalian Cell Gene Mutation Test (OECD TG 476)

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study meets generally accepted scientific principles, acceptable for assessment.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

- no A-T base pair tester strains included (e.g. TA102 or E.coli); limited documentation

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

Deviations:

yes

Remarks:

- no A-T base pair tester strains included (e.g. TA102 or E.coli); limited documentation

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Target gene:

his-operon

Species / strain / cell type:

S. typhimurium, other: TA 98, TA100, TA1535, TA1537, TA1538

Details on mammalian cell type (if applicable):

no data

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9 liver microsomes from male Sprague Dawley rats treated with a single intraperitoneal injection of Aroclor 1254 5-days before sacrifice.

Test concentrations with justification for top dose:

20, 60, 560, 1670, and 5000 µg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: N-methl-N'-nitro-N-nitrosoguanidine

Remarks:

positive control for TA100 and TA1535 (5 µg/plate)

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

positive control for TA98 and TA1538 (50 µg/plate) Migrated to IUCLID6: in absence of S9-mix

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

positive control for TA1537 (75 µg/plate)

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

5000 µg/plate

Vehicle 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:

cytotoxicity

Remarks:

5000 µg/plate

Vehicle 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:

cytotoxicity

Remarks:

5000 µg/plate

Vehicle 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:

cytotoxicity

Remarks:

5000 µg/plate

Vehicle 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:

cytotoxicity

Remarks:

5000 µg/plate

Vehicle controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: strain/cell type: TA 98, TA100, TA1535, TA1537, TA1538

Remarks:

Migrated from field 'Test system'.

TA98: Revertants Test

Test substance	Test 1 (without S9)	Test 2 (without S9)	Test 1 (with S9)	Test 2 (with S9)
solvent control	22 -26	22 -26	22 -26	18 -20
2 -Nitrofluorene	1508 -1637	2131 -2282	-	-
2 -Aminoanthracene	-	-	2213 -2247	1913 -2020
7 µg/plate 2,2,4 -trimethylpentane	-	15 -27	-	24 -46
20 µg/plate 2,2,4 -trimethylpentane	140 -191	19 -23	145 -206	29 -31
60 µg/plate 2,2,4 -trimethylpentane	112 -124	19 -26	64 -117	24 -33
190 µg/plate 2,2,4 -trimethylpentane	37 -55	19 -24	17 -28	12 -25

Retest (test 2) of TA98 without and with S9 at dose levels for 7, 20 and 60 µg/plate evidenced no difference from solvent controls.

Observed 5 -10 fold increase of TA98 revertants without and with S9 at 20 and 60 µg/plate in initial test was not confirmed in retest of TA98 without and with S9 at dose levels 7, 20 and 60 µg/plate.

In all experiments, no increase in revertants for other frame shift strains (TA1537 and TA 1538) was observed. Therefore the in test 1 observed genotoxic effects of 2,2,4 -trimethylpentane in strain TA 98 were rather false positive.

Conclusions:

Interpretation of results::
negative

Under the test conditions, the experimental compound, 2,2,4-trimethylpentane, did not exhibit a positive response and is, therefore, considered not be mutagenic in this system.

Executive summary:

Under the test conditions, the experimental compound, 2,2,4 -trimethylpentane, did not exhibit a positive response and is, therefore, considered not be mutagenic in this system.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

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

Adequacy of study:

key study

Study period:

1982-1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions

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: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Principles of method if other than guideline:

No guideline stated; similar to OECD guideline 473; rat hepatocytes with intrinsic metabolic activity, therefore no metabolic activation system added, only 100 cells from each culture analyzed.

GLP compliance:

not specified

Type of assay:

in vitro mammalian chromosome aberration test

Target gene:

not applicable

Species / strain / cell type:

hepatocytes: rat liver (RL4) cells

Details on mammalian cell type (if applicable):

The rat liver cell line, RL4, an epithelial-type cell line, was derived in this laboratory following the procedure described by Williams et al. (1971). RL4 was initiated in 1978 from a 10-day-old Wistar rat as described in Dean and Hodson-Walker (1979).

Metabolic activation:

not applicable

Metabolic activation system:

not necessary, liver cells

Test concentrations with justification for top dose:

2.5, 5, 10 µg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Tween 80/ethanol

Untreated negative controls:

not specified

Negative solvent / vehicle controls:

yes

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

cyclophosphamide

ethylmethanesulphonate

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: 22 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 22 hours + 2 hours fixation


SPINDLE INHIBITOR (cytogenetic assays): colcemid
STAIN (for cytogenetic assays): Giemsa


NUMBER OF REPLICATIONS: no data


NUMBER OF CELLS EVALUATED: 100 cells from each culture

Evaluation criteria:

Significant or dose-related increase in chromosome damage.

Key result

Species / strain:

hepatocytes: Rat liver (RL4) cells

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not specified

Positive controls validity:

valid

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

There was no significant or dose-related increase of chromosome damage in any of the cultures exposed.

Table: Metaphase chromosome analysis of RL₄cells

	0 µg/ml	2.5 µg/ml	5.0 µg/ml	10.0 µg/ml	1.0 µg/ml 7,12-dimethylbenzanthracene
Polyploidy (% cells)	3.7	2.0	2.7	1.3	1.5
Chromatid gaps (% cells)	1.3	1.7	1.0	2.3	6.0
Multiple aberrations (% cells)	-	-	-	-	0.5
Severe damage (% cells)	-	-	-	-	0.5
Chromatid aberrations (% cells)	0.3	-	-	-	4.0
Chromosome aberrations (frequency per cell)	-	-	-	-	-
Chromatid gaps (frequency per cell)	0.013	0.017	0.010	0.027	0.085
Chromatid breaks (frequency per cell)	0.003	-	-	-	0.005
Chromatid exchange (frequency per cell)	-	-	-	-	0.05
Chromosome breaks (frequency per cell)	-	-	-	-	0.005
Chromosome exchange (frequency per cell)	-	-	-	-	-

Conclusions:

Interpretation of results::
negative

This study examined the potential for the test substance Heptane to cause chromosomal aberrations in rat liver RL4 cells. Cells were exposed to concentrations of 0, 2.5, 5, and 10 ug/ml of test substance, and then examined for chromosomal aberrations including polyploidy, chromatid gaps, and chromatid exchanges. The positive control substance was 7,12 -dimethylbenzanthracene. A significant increase in chromatid gaps (7) was seen at the 10 ug/ml concentration. Though greater than the solvent control frequency, this was not accompanied by an increase in any other aberrations and is not considered to be treatment related. Under the conditions of this study, the test material was not clastogenic.

Executive summary:

This study examined the potential for the test substance Normal-Heptane to cause chromosomal aberrations in rat liver RL4 cells. Cells were exposed to concentrations of 0, 2.5, 5, and 10 ug/ml of test substance, and then examined for chromosomal aberrations including polyploidy, chromatid gaps, and chromatid exchanges. The positive control substance was 7,12 -dimethylbenzanthracene. A significant increase in chromatid gaps (7) was seen at the 10 ug/ml concentration. Though greater than the solvent control frequency, this was not accompanied by an increase in any other aberrations and is not considered to be treatment related. Under the conditions of this study, the test material was not clastogenic.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

yes

Remarks:

- using microtiter plates

GLP compliance:

not specified

Type of assay:

mammalian cell gene mutation assay

Target gene:

thymidine kinase

Species / strain / cell type:

human lymphoblastoid cells (TK6)

Details on mammalian cell type (if applicable):

- Type and identity of media: RPMI 1640 medium supplemented with 15% heat-inactivated horse serum

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

with Aroclor induced-rat liver homogenate

Test concentrations with justification for top dose:

5 % v/v TMP in DMEM medium, administered undiluted or as 50 % (1:1 saturated to normal medium)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMEM medium

Untreated negative controls:

yes

Remarks:

with and without S9

Negative solvent / vehicle controls:

yes

Remarks:

DMEM medium

Positive controls:

yes

Remarks:

for S9 activated cultures

Positive control substance:

benzo(a)pyrene

Remarks:

15 µM

Untreated negative controls:

yes

Remarks:

with and without S9

Negative solvent / vehicle controls:

yes

Remarks:

DMEM medium

Positive controls:

yes

Remarks:

for non-activated cultures

Positive control substance:

ethylmethanesulphonate

Remarks:

0.2 mM

Details on test system and experimental conditions:

see "any other information on materials and methods"

Key result

Species / strain:

human lymphoblastoid cells (TK6)

Metabolic activation:

with and without

Genotoxicity:

negative

Remarks:

TMP did not induce significant increases in the mutation frequency at the thymidine kinase locus.

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cell survival in TMP-saturated medium with and without metabolic activation was greater than 50-60 %.

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

The elevated mutation frequencies of positive control compounds were as expected.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
Cell survival in positive control treated cultures was 40 or 30% for benzo(a)pyrene and EMS, respectively

Remarks on result:

other: all strains/cell types tested

Conclusions:

Interpretation of results:
negative

Based on the study design there is no incidence of increased genetic toxicity caused by the test substance.

Executive summary:

Based on the study design there is no incidence of increased genetic toxicity caused by the test substance.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

The genetic toxicity tests listed below had negative results for 2,2,4-trimethylpentane.

 

Genetic Toxicity in vivo - Unscheduled DNA Synthesis Test with Mammalian Liver Cells (OECD TG 486)

Link to relevant study records

Reference

Endpoint:

in vivo mammalian cell study: DNA damage and/or repair

Remarks:

Type of genotoxicity: DNA damage and/or repair

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 486 (Unscheduled DNA Synthesis (UDS) Test with Mammalian Liver Cells in vivo)

Deviations:

yes

Remarks:

- limited documentation

GLP compliance:

not specified

Type of assay:

unscheduled DNA synthesis

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, N.Y.)
- Weight at study initiation: 200-300 g
- Assigned to test groups randomly: yes
- Fasting period before study: no
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): controlled
- Humidity (%): controlled
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

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

Duration of treatment / exposure:

one single dose

Frequency of treatment:

sinlge treatment

Post exposure period:

2, 12, 24 and 48 hours after dosing

Remarks:

Doses / Concentrations:
500 mg/kg
Basis:
nominal conc.

No. of animals per sex per dose:

3 males/ time period

Control animals:

yes

Positive control(s):

dimethylnitrosamine (DMN), dissolved in water
- Route of administration: orally
- Doses / concentrations: 10 mg/kg

Tissues and cell types examined:

hepatocytes

Details of tissue and slide preparation:

see "any other information on materials and methods"

Statistics:

One-way analysis of variance was performed on UDS and S-phase data with multiple treatment groups. S-phase data were adjusted by square root transformation. Treatment means were compared to control means by Dunnett's multiple comparison test. Level of significance was <0.05.

Key result

Sex:

male

Genotoxicity:

negative

Remarks:

TMP did not induce unscheduled DNA synthesis in hepatocyte cultures from rats treated in vivo.

Toxicity:

no effects

Remarks:

Mean cell viabilities in preparations of hepatocytes were: 84 % at 2-12 hours after administration of 500 mg/kg TMP.

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

see "Remarks on results"

Mean cell viabilities in preparations of hepatocytes were: 85 % at 24 hours after administration of water (negative control) and 84 % at 2-12 hours after administration of 500 mg/kg TMP.

No increase in UDS expressed as increase in NG or number of cells in repair was observed in hepatocytes isolated from male rats at 2, 12, 24, or 48 hours post-dose. A strong response was elicited by the DMN positive control, as expected.

Autoradiographic preparations of hepatocytes isolated from rats 24 hr after treatment with TMP revealed a significant increase in the number of cells in S phase (2.1% vs 0.35% in controls); this value dropped back to 0.55% at 48 hours. TMP also significantly increased RDS in mice at 24 hours; no 48 hour values were presented. However low serum alanine transaminase activity were observed at 24 and 48 hours after a single treatment with 500 mg/kg TMP indicating that TMP induced little if any hepatocellular necrosis which could trigger regenerative cell proliferation.

Following 11 consecutive daily treatments with 100 mg/kg/day TMP, a significant increase (p<0.05) in rat hepatic concentration of DNA (mg/g liver) was seen but the total hepatic DNA content per rat was comparable to controls. Liver weight relative to body weight was also comparable to controls. The demonstrated increase in RDS suggests that TMP may stimulate additive rather than regenerative cell proliferation but not of sufficient magnitude to significantly increase the total DNA content of the liver.

TMP was administered at a single 500 mg/kg concentration to evaluate UDS and RDS in conjunction with a multidose study for unleaded gasoline. When RDS was observed, a liver DNA content determination was performed in rats with treatment over 11 days to determine the type of proliferative response.

Conclusions:

Interpretation of results: negative

Based on this study design 2, 2, 4- trimethylpentane does not induce unscheduled DNA synthesis in vivo by unchanged application via gavage.

Executive summary:

Based on this study design 2, 2, 4- trimethylpentane does not induce unscheduled DNA synthesis in vivo by unchanged application via gavage.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

There is genetic toxicity data available for 2,2,4-trimethylpentane. Additionally, data is available for structural analogue heptane and presented in the dossier. This data is read across to 2,2,4-trimethylpentane based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

 

In Vitro

 

In vitro Gene Mutation Study in Bacteria

 

2,2,4 -trimethylpentane

A bacterial reverse mutation assay (Ames test) was conducted with 2,2,4-trimethylpentane following a protocol similar to OECD 471.Salmonella typhimurium strainsTA 98, TA 100, TA 1535, TA 1537 and TA 1538 were exposed to the test substance at 20, 60, 560, 1670, and 5000 µg/plate in the absence and in the presence of a metabolic activator. Cytotoxic effects were observed at 5000 µg/plate. Iso-octane did not induce mutations in the bacterial mutation test in either the absence or presence of metabolic activator in any strain tested. Under the test conditions, the experimental compound, iso-octane, did not exhibit a positive response and is, therefore, considered not be mutagenic in this system (Chevron Phillips, 1982).

 

In vitro Chromosome Aberration in Mammalian Cells

 

Heptane

The potential of n-heptane (CAS No. 142-82-5) to cause chromosomal aberrations in rat liver RL4 cells was tested with a method comparable to OECD 473. Cells were exposed to concentrations of 0, 2.5, 5, and 10 µg/mL of test substance for 22 h, and then examined for chromosomal aberrations including polyploidy, chromatid gaps, and chromatid exchanges. No cytotoxicity was observed. A significant increase in chromatid gaps was seen at 10 µg/mL. However, this effect was neither dose-dependent nor accompanied by an increase in any other aberration type, and therefore not considered to be treatment-related. Under the conditions of this study, the test material was not clastogenic (Shell Chemicals, 1983; Brooks et al., 1988).

In vitro Gene Mutation study in Mammalian Cells

 

2,2,4-trimethylpentane

2,2,4-trimethylpentane was tested in a mammalian cell gene mutation assay performed according to OECD 476. The test material was prepared by adding 2,2,4 -trimethylpentane at a final concentration of 5 % v/v in culture (DMEM) medium and stirred overnight at room temperature in a foil wrapped, capped parafilm-sealed bottle to saturate the medium. Human lymphoblastoid cells (TK6) were exposed to 100 or 50 % of this saturated DMEM medium with and without metabolic activation for 3 h and allowed for expression for 4 to 8 days. Both with and without metabolic activation, 2,2,4 -trimethylpentane did not induce significant increases in the mutation frequency at the thymidine kinase locus and cell survival in 2,2,4 -trimethylpentane-saturated medium was greater than 50-60 %. Based on the study design there was no incidence of increased genetic toxicity caused by the test substance (Richardson et al., 1986).

 

2,2,4 -trimethylpentane was also tested in a Mouse Lymphoma Forward Mutation Assay performed according to a protocol similar to OECD TG 476. At concentrations ranging from 20 to 500 µg/mL (limit of solubility), 2,2,4 -trimethylpentane did not induce gene mutations in the mouse lymphoma L5178Y heterozygous TK+/-cells in the presence of metabolic activation, resulting in cytotoxicity at 165 µg/mL and above. Without metabolic activation, cytotoxicity at 500 µg/mL and an equivocal to weakly mutagenic response were observed (Chevron Phillips, 1982).

 

In Vitro Unscheduled DNA Synthesis in Mammalian Cells

 

2,2,4-trimethylpentane

The potential of 2,2,4-trimethylpentane to induce unscheduled DNA synthesis (UDS) as an indicator of genotoxicity was tested in rat hepatocytes in a study comparable to OECD TG 482. Primary cultures were prepared from hepatocytes isolated from a rat. After attachment to coverslips and acclimatisation, cells were treated with [3H] thymidine (10 µCi/mL) and undiluted 2,2,4 -trimethylpentane at 0.33, 1.00, 3.33 % (v/v). The cells were then incubated for 18 hours. The highest concentration of 3.33% v/v was lethal to cell cultures. At the lower concentrations, 2,2,4 -trimethylpentane did not induce unscheduled DNA synthesis in vitro by direct application to primary hepatocyte cultures. Based on the study design there was no incidence of increased genetic toxicity caused by the test substance (Loury et al. 1986).

 

In Vitro Sister Chromatid Exchange Assay in Mammalian Cells

 

2,2,4 -trimethylpentane

Human lymphoblastoid cells exposed to 2,2,4 -trimethylpentane for 3 h as described above were also tested for the induction of sister chromatid exchange (SCE) according to OECD TG 479. Following exposure, the cells were incubated in the dark in the presence of 5'Bromo-deoxyuridine (10 µM) for 36 h, and metaphases were analysed microscopically thereafter. Both with and without metabolic activation, 2,2,4-trimethylpentane did not induce an increased incidence of SCEs in TK6 cells (Richardson et al., 1986; Wilmer et al., 1981). No statistically significant increase in number of SCEs (with and without metabolic activation) was also observed.

 

In another study compliant with OECD TG 479, Chinese hamster Ovary (CHO) cells were exposed to 25, 84, 250 µg/mL iso-octane in DMSO and 1400 and 3500 µg/mL iso-octane without vehicle. No cell growth occurred at the 250 µg/mL, without activation. No statistically significant increase in number of SCEs (with and without metabolic activation) was also observed. Based on the study design there was no increased mutagenic response caused by 2,2,4-trimethylpentane in CHO cells with and without metabolic activation. (Chevron Phillips, 1982)

 

In Vivo

 

In Vivo Unscheduled DNA Synthesis Test with Mammalian Liver Cells

 

2,2,4 -trimethylpentane

As part of an unscheduled DNA synthesis (UDS) study performed in vitro, 2,2,4 -trimethylpentane was administered to rats and mice orally at a single dose of 500 mg/kg. Primary hepatocytes were isolated from livers at sacrifice times 2, 12, 28 or 48 hours post-treatment and cultures were evaluated for unscheduled and replicative DNA synthesis. 2,2,4 -trimethylpentane did not induce unscheduled DNA synthesis in hepatocyte cultures, and increases in replicative DNA synthesis were not of sufficient magnitude to increase the total DNA content of the liver (Loury et al., 1986).

Justification for classification or non-classification

The negative results of substance specific in vitro and in vivo genotoxicity assays and data from structural analogues do not warrant the classification of 2,2,4-trimethylpentane as genotoxic under the new Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).