Ethylene

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP, near guideline study, published in peer reviewed literature, limitations in design and/or reporting but otherwise adequate for assessment.

Justification for type of information:

N/A

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1988

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

only a single bacterial strain was used.

Principles of method if other than guideline:

Modified Ames assay reported.

GLP compliance:

not specified

Type of assay:

other: Modified Ames test

Test material

Test material information

Constituent 1

Reference substance name:

Ethylene

EC Number:

200-815-3

EC Name:

Ethylene

Cas Number:

74-85-1

Molecular formula:

C2H4

IUPAC Name:

ethene

Details on test material:

- Name of test material (as cited in study report): Ethene
- Physical state: gas
- Source: AGA Specialgas, Stockholm
- Analytical purity: 99.5%

Specific details on test material used for the study:

not specified

Method

Target gene:

not specified

Species / strain

Species / strain / cell type:

S. typhimurium TA 100

Metabolic activation:

with and without

Metabolic activation system:

Aroclor-induced rat liver S9

Test concentrations with justification for top dose:

0.5-20% (up to 200,000 ppm)

Vehicle / solvent:

not specified

Controls

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: 1 µg benzo(a)pyrene and 1 µg 2-nitrofluorene

Remarks:

with and without metabolic activation

Details on test system and experimental conditions:

EXPOSURE SYSTEM
- Dynamic flow-through exposure system
- Ethene (ethylene): diluted with air in a mixing chamber to 0.5-20% concentration. The gas was passed into an exposure chamber containing 3 bacterial plates and out to the ventilation system through a carbon filter. The internal air of the exposure chamber was kept at 34°C.
- The air and gases are dry, but the atmosphere in the exposure chamber becomes saturated with water (~85% humidity) due to the humidity of the agar plates.
- IR-detection was used to analytically measure the concentration of ethylene within each cylinder.
- Measurements of the gas concentrations were calculated from the gas concentration in the cylinder and from the dilution factors.
- No actual measurement of the gas concentrations during mutagenicity experiments was performed.

METHOD OF APPLICATION: in agar (plate incorporation)
- 0.1 mL of a 14 hr (overnight) bacterial culture was mixed with 0.5 mL phosphate buffer or a metabolic activation system (0.5 mL S9-mix, containing 20 µL S9) in 2 mL soft agar containing traces of biotine and histidine. This was poured onto minimal glucose agar plates. When the agar was solid, three plates (without lids) were placed in the exposure chamber, and three control plates (with lids) were placed in the 37°C incubator. Three flow rates were used, 250, 500, and 1000 mL/min.
- After 6 or 7 hours exposure to the gas stream, the bacteria plates were removed from the exposure chamber and placed in the incubator. Some experiments were performed with longer exposure times.
- The number of revertant colonies was counted after 48-60 hr.
- Control experiments: bacteria plates exposed to pure air in the exposure chamber for 6-7 hr prior to incubation.

Rationale for test conditions:

not specified

Evaluation criteria:

Toxicity was assessed by examination of the background lawn of bacteria: sparse background growth on the plate was classed as slightly toxic and a very sparse background growth indicated toxicity.

Statistics:

As the number of spontaneous revertants can vary from day to day variation and only one dose was tested per day, the increase in the number of revertants on exposed plates compared to non-exposed plates was computed for each dose.

Results and discussion

Test results

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

1 µg benzo(a)pyrene and 1 µg 2-nitrofluorene gave approximately 740 and 500 revertants per plate with and without S9, respectively.

Remarks on result:

other: not specified

Any other information on results incl. tables

The mean increment of revertants from control experiments (n=8) was ~37%±17% due to mutagenic contaminants in the compressed air or to enhanced growth that would also result in the production of more spontaneous mutants. No mutagenic effect was demonstrated with ethylene concentrations up to 20% in air when tested with flow rates of 250, 500, and 1000 mL/min for 7 hours with or without metabolic activation.

Applicant's summary and conclusion

Conclusions:

Interpretation of results:
negative with metabolic activation
negative without metabolic activation

Ethylene is not mutagenic when tested at concentrations of 0.5 to 20% in air for 7 hours in Salmonella typhimurium strain TA100.

Executive summary:

A dynamic flow-through exposure system was designed for mutagenicity studies of gaseous substances, including ethylene. Salmonella typhimurium strain TA100 was used to test ethylene concentrations from 0.5 to 20% in air with flow rates of 250, 500, and 1000 mL/min. Exposure was 7 hours with and without metabolic activation.

No mutagenic effects were demonstrated with or without metabolic activation.