Butyl carbamate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Based on the negative results in the AMES studies, butyl carbamate is not expected to have any genotoxic potential.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From November 07, 1989 to November 16, 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Purity: > 99%.
Appearance: clearless crystals

Target gene:

Histidine

Species / strain / cell type:

other: S. Typhimurium TA 98, TA 100, TA 1535, TA 1537, TA 1538

Additional strain / cell type characteristics:

other: histidine auxotrophic mutants

Remarks:

amino acid-dependent strains

Metabolic activation:

with and without

Metabolic activation system:

(NADP+)-cytochrome p450 dependent mixed function oxidase enzymes of the liver (S-9)

Test concentrations with justification for top dose:

From 4 µg/plate to 10000 µg/plate
3 plates per condition

Vehicle / solvent:

DMSO (100µL)

Untreated negative controls:

yes

Remarks:

plate without mutagen

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

benzo(a)pyrene

other: 2-aminoanthracene

Details on test system and experimental conditions:

Mutagenicity test:
Top agar is prepared for the Salmonella strains by mixing 100 mL agar (0.6% agar, 0.5% NaCl) with 10 mL of a 0.5 mM histidine-biotin solution. The following ingredients are added (in order) to x mL of molten top agar at 45°C:
- 0.1 mL of an overnight nutrient broth culture of the bacterial tester strain
- 0.1 mL test compound solution
- 0.5 mL S-9 Mix (if repuired) or buffer
After mixing, the liquid is poured into a petridish with minimal agar (1.2% agar, Vogel-Bonner E medium with 2% glucose). After incubation for 48 to 72 hours at 37°C in the dark, colonies (his+ revertants) are counted.

Rationale for test conditions:

Toxicity experiments and dose range finding

Evaluation criteria:

Number of his+ revertants

Statistics:

The number of colonies per plate with each strain as well as mean values of 3 plates, corrected to the next whole number

Key result

Species / strain:

other: S. Typhimurium TA 98, TA 100, TA 1535, TA 1537, TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

Under the study conditions, the test substance was not mutagenic in Salmonella typhimurium (bacterial reverse mutation assay).

Executive summary:

A study was conducted to determine the mutagenic potential of the test substance according to OECD Guideline 471 (bacterial reverse mutation assay), in compliance with GLP. Five S. typhimurium strains (i.e. TA 98, TA 100, TA 1535, TA 1537, TA 1538) were exposed to the test substance for 48 to 72 h, at concentrations of 4 to 10000 µg/plate (with 3 plates per condition). At the end of the incubation period, the number of His+ revertants was counted. The test subtance did not cause a significant increase in the number of revertant colonies with any of the tester strains, either in the absence or presence of metabolic activation. Positive and negative (vehicle) controls gave expected results; the experiment was therefore considered valid. Under the study conditions, the test substance was not mutagenic in Salmonella typhimurium (Muller, 1989).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Based on the negative results in the in vivo micronucleus study, butyl carbamate is not expected to have any genotoxic potential.

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

5 Feb 2020 - 23 March 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

2016

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

mammalian erythrocyte micronucleus test

Species:

mouse

Strain:

NMRI

Details on species / strain selection:

source: Charles River Laboratories, Sulzfeld, Germany

Sex:

female

Details on test animals or test system and environmental conditions:

Housing: single
Cage Type: Makrolon Type II / III, with wire mesh top
Bedding: granulated soft wood bedding
Feed: 2018C Teklad Global 18% protein rodent diet
(certified), ad libitum
Water: tap water, ad libitum
Environment: temperature 22 + 2°C
relative humidity approx. 45-65%
artificial light 6.00 a.m. - 6.00 p.m.
ventilation: at least eight air changes per hour

Route of administration:

oral: gavage

Vehicle:

PEG 400

Details on exposure:

The animals received the test item, the vehicle or the positive control item once orally

Duration of treatment / exposure:

once by gavage

Frequency of treatment:

single administration

Post exposure period:

24 and 48 h

Dose / conc.:

0 mg/kg bw (total dose)

Remarks:

negative control

Dose / conc.:

125 mg/kg bw (total dose)

Remarks:

low dose group

Dose / conc.:

250 mg/kg bw (total dose)

Remarks:

mid dose group

Dose / conc.:

500 mg/kg bw (total dose)

Remarks:

high dose group

No. of animals per sex per dose:

6 females

Control animals:

yes, concurrent vehicle

Positive control(s):

40 mg/kg bw Cyclophosphamide

Tissues and cell types examined:

Evaluation of the slides was performed using NIKON microscopes with 100x oil immersion objectives. At least 4000 polychromatic erythrocytes (PCE) per animal were analysed for micronuclei. To describe a cytotoxic effect the ratio between polychromatic and normochromatic erythrocytes was determined in the same sample and expressed in polychromatic erythrocytes per total erythrocytes. The analysis was performed with coded slides.

Evaluation criteria:

The study is considered valid as the following criteria are met:
- the concurrent negative control is considered acceptable for addition to the laboratory historical control database (should ideally be within the 95% control limits of the distribution of the historical negative control database)
- at least 5 animals per group could be evaluated.
- the appropriate number of doses and cells were analysed.
- PCE to erythrocyte ratio is not less than 20% of the negative control.
- The positive control shows a statistically significant increase of micronucleated PCEs compared to the negative control and is compatible to those in the historical positive control database.

Statistics:

Statistical significance at the five per cent level (p < 0.05) was evaluated by means of the non-parametric Mann-Whitney test using the validated statistical program RScript Wilcoxon_2.Rnw.
The Holm-Bonferroni Adjustment method was used to correct for the Familiywise error rate of multiple comparisons.

Key result

Sex:

female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

clinical The observed systemic toxicity at the tested doses is indicative for a systemic distribution of the test item. Thus, bioavailability of the test item under the tested conditions is assumed.

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

After treatment with the test item the number of PCEs was not substantially decreased as compared to the mean value of PCEs of the vehicle control thus indicating that Butyl carbamate did not exert any cytotoxic effects in the bone marrow. In comparison to the corresponding vehicle controls there was no biologically relevant or statistically significant enhancement increase in the frequency of the detected micronulclei at any preparation interval after administration of the test item and with any dose level used.
The concurrent positive control (40 mg/kg b.w. cyclosphosphamide administered orally) was used as positive controldid which induced a substantial increase in cells with micronuclei, demonstrating the test procedure is valid.

Executive summary:

In conclusion, it can be stated that under the experimental conditions reported, the test item Butyl carbamate did not induce micronuclei as determined by the micronucleus test with bone marrow cells of the mouse. Therefore, Butyl carbamate is considered to be non-genotoxic in this in vivo micronucleus assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

In vitro:

A study was conducted to determine the mutagenic potential of butyl carbamate according to OECD Guideline 471 (bacterial reverse mutation assay), in compliance with GLP. Five Salmonella typhimuriumstrains (i.e. TA 98, TA 100, TA 1535, TA 1537, TA 1538) were exposed to the test substance for 48 to 72 h, at concentrations of 4 to 10000 µg/plate (with 3 plates per condition). At the end of the incubation period, the number of His+ revertants was counted. The test substance did not cause a significant increase in the number of revertant colonies with any of the tester strains, either in the absence or presence of metabolic activation. Positive and negative (vehicle) controls gave expected results; the experiment was therefore considered valid. Under the study conditions, the test substance was not mutagenic to any of the strains of S. typhimurium (Muller, 1989).

In vivo:

the test item Butyl carbamate did not induce micronuclei as determined by the micronucleus test with bone marrow cells of the mouse. Therefore, Butyl carbamate is considered to be non-genotoxic in this in vivo micronucleus assay.

Justification for classification or non-classification

In absence of positive results in the AMES study and in vivo micronucleus study, butyl carbamate no classification needs to be applied according to the CLP criteria (EC 1272/2008).