1,1,1-trichloroethane

Genetic toxicity: in vitro

Administrative data

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: Tests conducted on behalf of NTP according to rigorous protocol. Not GLP. Only a 4 hour exposure time was used.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

2000

Reference 2

Reference Type:

publication

Title:

Evaluation of the L5178Y Mouse Lymphoma Cell Mutagenesis Assay: Intralaboratory Results for Sixty-Three Coded Chemicals Tested at Litton Bionetics, Inc.

Author:

MYHR-BC; CASPARY-WJ

Year:

1988

Bibliographic source:

ENVIRON-MOL-MUTAGEN 12(SUPPL13) 103-194

Reference 3

Reference Type:

publication

Title:

Evaluation of the L5178Y Mouse Lymphoma Cell Mutagenesis Assay: Intralaboratory Results for Sixty-Three Coded Chemicals Tested at SRI International

Author:

MITCHELL-AD; RUDD-CJ; CASPARY-WJ

Year:

1988

Bibliographic source:

ENVIRON-MOL-MUTAGEN 12(SUPPL13) 37-101

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

No 24 hour expousre period, only 4 hours. No record was made as to whether colonies were large or small (colony size is believed to be related to the type of mutation).

GLP compliance:

no

Type of assay:

mammalian cell gene mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

1,1,1-trichloroethane

EC Number:

200-756-3

EC Name:

1,1,1-trichloroethane

Cas Number:

71-55-6

Molecular formula:

C2H3Cl3

IUPAC Name:

1,1,1-trichloroethane

Details on test material:

Coded aliquot from Radian Corporation

Method

Target gene:

thymidine kinase locus: tk+tk- to tk-tk-

Species / strain

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

Litton Bionetics, Inc: TK+/- heterozygote clone 3.7.2C of L5178Y mouse lymphoma cells obtained in 1977 form the Food and Drug Administration (Washington DC). Structure confirmed in 1985.

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

from livers of Aroclor 1253-onduced male Sprague-Dawley rats or Syrian hamsters

Test concentrations with justification for top dose:

SRI International 0, 0.21, 0.26, 0.33, 0.41, 0.51, 0.64, 0.80 μL/mL with and without S9
Litton Bionetics Inc 0, 0.0078, 0.0156, 0.0313, 0.0625, 0.125, 0.25, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5

Vehicle / solvent:

Dimethylsulfoxide

Controls

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Remarks:

methylcholanthrene, ethylmethanesulphonate

Evaluation criteria:

All data were evaluated statistically for both trend and peak responses. Both responses had to be significant (P<0,05) for the result to be considered positive. A single significant response led to a ‘questionable’ conclusion, and the absence of both a trend and a peak response resulted in a ‘negative’ decision.

Results and discussion

Test results

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

ambiguous

Remarks:

negative result without metabolic activation, negative and positive results with metabolic activation

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

The results of the test conducted at SRI International gave overall negative results with and without metabolic activation (a positive result with metabolic activation which occurred at toxic dose levels was not repeatable). However, in the second laboratory (Litton Bionetics Ltd) there was an equivocal result in the presence of metabolic activation. Two trials with metabolic activation gave positive results, a third trial was only positive at a level associated with precipitation and a fourth trial was negative; overall the results were therefore deemed to be equivocal.

Any other information on results incl. tables

Table 1: SRI International  Induction of TFT resistance, Mutant fraction

Concentration (μL/mL)	Trial 1 –S9		Trial 2 –S9		Trial 3 –S9		Trial 1 +S9		Trial 2 +S9
	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction
0 (DMSO)	4	74	2	28	4	28	3	57	4	41
0.21			2	41	3	24	2	38	3	37
0.26	2	51	2	29	3	22	2	37	3	37
0.33	2	30	2	35	3	27			3	35
0.41	1	20	2	28	3	35	2	41	3	35
0.51	2	33			3	23	2	71	3	45
0.64	Toxic		Toxic		Toxic		2	106*	Toxic
0.80			Toxic
Ethyl methanesulfonate 500 μg/mL	3	751*	3	542*	3	558*
Methylcholanthrene     5 μg/mL							3	349*	3	291*

Table 2: Litton Bionetics Inc Induction of TFT resistance, Mutant fraction

Concentration (μL/mL)	Trial 1 –S9		Trial 2 –S9		Trial 3 –S9		Trial 1 +S9		Trial 2 +S9		Trial 3 +S9		Trial 4 +S9
	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction	No	Average mutant fraction
0 (DMSO)	3	21	4	26	4	54	3	38	4	49	4	33	4	24
0.0078							2	44
0.0156							2	57
0.025									3	68
0.0313							2	62*
0.05	3	18	3	21	3	48			3	59	3	32
0.0625							2	44
0.1	3	13	3	19	3	55			3	69	3	30	3	29
0.125							2	49
0.2	2	14	2	24	3	59			3	83*	3	42	3	31
0.25							2	82*
0.3					3	52			3	98*	3	32	2	28
0.4	toxic		3	28	3	60			3	104*	3	49	2	27
0.5 P			toxic		2 ^a	84	toxic		toxic		3^a	49*	3	26
Ethyl methanesulfonate 500 μg/mL	3	1,084*
Ethyl methanesulfonate 250 μg/mL			3	375*	3	788*
Methylcholanthrene     5 μg/mL							2	419*	3	371*	3	318*	3	218*

P – precipitation present

* statistically significant p0.05 versus solvent control

Applicant's summary and conclusion

Conclusions:

The potential for 1,1,1-trichloroethane to induce gene mutations was assessed using the mouse lymphoma assay in two independent laboratories at concentrations up to 0.64 μL/mL, following 4 hours exposure with and without metabolic activation; no test was conducted without metabolic activation for 24 hours. In one laboratory the results were negative, in the second laboratory the results with metabolic activation were deemed to be equivocal.

Executive summary:

The potential of 1,1,1-trichloroethane to induce gene mutations in mouse lymphoma cells (L5178Y) was assessed in two separate laboratories. 

In each laboratory the test item was tested in two independent experiments, with and without a metabolic activation system.  Cell cultures were exposed to control or test item for 4 hours and plates were incubated for 10 to 12 days and the number of colonies counted.  Experiments were conducted both with or without activation at concentrations between 0.21 and 0.64 µg/mL and 0.0078 and 0.5 µg/mL.  The trials were run several times, due to some equivocal, but not repeatable, results.  No test was conducted for 24 hours without metabolic activation.

The potential for 1,1,1-trichloroethane to induce gene mutations was assessed using the mouse lymphoma assay in two independent laboratories at concentrations up to 0.4 μL/mL, following 4 hours exposure with and without metabolic activation; no test was conducted without metabolic activation for 24 hours. In one laboratory the results were negative, in the second laboratory the results with metabolic activation were deemed to be equivocal.