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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
Remarks:
Type of genotoxicity: chromosome aberration
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: Study was conducted prior to GLP and guidelines but sufficient data is available for the interpretation of results.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1979
Report Date:
1979

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
GLP compliance:
no
Type of assay:
chromosome aberration assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
epichlorohydrin, lot #TB 09157-3, >99.8% purity

Chromatographic Analysis:
Propylene dichloride 0.03% (wt.)
cis-1,3-dichloropropene 0.08% (wt.)
2,3-dichloropropene 0.07% (wt.)
B-chloroallyl alcohol 0.01% (wt.)

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
Groups of 10 male and 10 female Fischer 344 rats were exposed. by inhalation to 0, 5, 25 or 50 ppm of epichlorohydrin in the air for 6 hours/day, 5 days/week for 4 weeks. There were 26 and 27 days of exposure for males and females, respectively, during this interval. The animals were individually caged and kept in the exposure chamber during both the exposure and nonexposure intervals. Food was removed during the exposure periods, but was otherwise freely available. Water, via an automatic water system, remained available at all times. These animals were exposed simultaneously
with those in the 90-day subchronic study. Therefore, additional details of the exposure generation and monitoring are presented in that report.

Administration / exposure

Route of administration:
inhalation: vapour
Vehicle:
not applicable
Details on exposure:
These animals were exposed simultaneously with those in the 90-day subchronic study. Therefore, additional details of the exposure generation and monitoring are presented in that report.
Duration of treatment / exposure:
Groups of 10 male and 10 female Fischer 344 rats were exposed. by inhalation to 0, 5, 25 or 50 ppm of epichlorohydrin in the air for 6 hours/day, 5 days/week for 4 weeks. There were 26 and 27 days of exposure for males and females, respectively, during this interval. These animals were exposed simultaneously with those in the 90-day subchronic study. Therefore, additional details of the exposure generation and monitoring are presented in that report.
Frequency of treatment:
Groups of 10 male and 10 female Fischer 344 rats were exposed. by inhalation to 0, 5, 25 or 50 ppm of epichlorohydrin in the air for 6 hours/day, 5 days/week for 4 weeks. There were 26 and 27 days of exposure for males and females, respectively, during this interval.
Post exposure period:
On the day following the last exposure (approximately 18 hours), the rats were injected intraperitoneally with colchicine four hours prior to sacrifice, and the bone marrow cells were processed.
No. of animals per sex per dose:
10 male and 10 female Fischer 344 rats/dose level
Positive control(s):
no positive control

Examinations

Tissues and cell types examined:
Bone marrow cells were processed. Slides were coded, randomized, and evaluated by three accredited medical technologists. The methods used for the scoring and analysis followed the criteria set by Buckton and Evans (1973). The mitotic index was determined as the percentage of cells in metaphase, based on the observation of 500 cells.

Buckton, K. E. and H. J. Evans. Methods for the Analysis of human chromosome aberrations. World Health Organization, Geneva (1973).
Details of tissue and slide preparation:
Bone marrow cells were processed. Slides were coded, randomized, and evaluated by three accredited medical technologists. The methods used for the scoring and analysis followed the criteria set by Buckton and Evans (1973). The mitotic index was determined as the percentage of cells in metaphase, based on the observation of 500 cells.

Buckton, K. E. and H. J. Evans. Methods for the Analysis of human chromosome aberrations. World Health Organization, Geneva (1973).
Evaluation criteria:
Authors followed the criteria set by Buckton and Evans (1973).

Buckton, K. E. and H. J. Evans. Methods for the Analysis of human chromosome aberrations. World Health Organization, Geneva (1973).
Statistics:
The results of the abnormal cells were analyzed using Fisher's exact probability test (Siegel, 1956) with the animal as the unit. The data were further analyzed using the Wilcoxon test as modified by Haseman and Hoe1 (1974) to take into account the multiple abnormalities in some animals. Mitotic index was analyzed (Steel and Torrie ) using a one-way analysis of variance.

Haseman, J. K. and D. G. Hoel. (1974). Tables of Gehan's generalized Wilcoxon test with fixed point sensoring. J. Stat. Comp. and Simulation 3: 117-135.

Seigel, S. (1956). Nonparamentric Statistics for the Behavioral Sciences. McGraw-Hill Book Company, Inc., New York, New York, pp. 96-104.

Steel, R. G. and H. H. Torrie. (1960). Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc. New York.

Results and discussion

Additional information on results:
Two groups of samples--from the female animals exposed to 5 and 25 ppm--were inadvertantly destroyed during centrifugation of the cell preparations and were not available for evaluation. Slides of sufficient quality to score 200 cells per animal were obtained from 36 of the 40 male rats and from 14 of the 20 females. Slides from the remaining animals were not scorable. Mitotic indices on 500 cells from the females were not significantly different by analysis of variance between the control and exposed groups (p=0.645). The clustering of unscorable slides from the exposed females was thus probably not a manifestation of cytotoxicity. The frequencies of chromosomal aberrations overall were quite low. For the 5 ppm group of males the percentage of abnormal cells was less than half that of the unexposed males. While the group findings for males at 25 and 50 ppm were twofold higher than the controls, there was no consistent dose-response effect. There was fewer than one abnormal cell per animal for all groups, with no chromosome breaks or markers in any group of the males. The overall rarity of chromosomal aberrations makes it difficult to determine if the observations in the 25 and 50 ppm male groups were associated with exposure, or were rather inherent fluctuations, as seen in the results from the 5 ppm group when compared with the unexposed controls. Results of statistical analyses of the data from the males were as follows. The number of animals with aberrations was 4/18 for the pooled control and 5 ppm exposed groups, and 8/18 for the pooled 25 ppm and 50 ppm groups. These proportions were not significantly different by Fisher's test (p>0.10). Haseman's test, the most appropriate way to test multiple events in animals, had a calculated p value between 0.05 and 0.1. If the data are analyzed with each dosage group considered separately, there are no significant differences by any method. Thus all of the statistical tests confirmed that the differences in the males were not significant at the 5% level. However, there was a trend toward a higher total number of abnormal cells in the 25 and 50 ppm exposure groups of males. In contrast to the results of the males, there was no difference between the frequency of abnormal cells in the 50 ppm exposed females compared to the unexposed control group.

Any other information on results incl. tables

Results of statistical analyses of the data from the males were as follows. The number of animals with aberrations was 4/18 for the pooled control and 5 ppm exposed groups, and 8/18 for the pooled 25 ppm and 50 ppm groups. These proportions were not significantly different by Fisher's test (p>0.10). Haseman's test, the most appropriate way to test multiple events in animals, had a calculated p value between 0.05 and 0.1. If the data are analyzed with each dosage group considered separately, there are no significant differences by any method. Thus all of the statistical tests confirmed that the differences in the males were not significant at the 5% level. However, there was a trend toward a higher total number of abnormal cells in the 25 and 50 ppm exposure groups of males. In contrast to the results of the males, there was no difference between the frequency of abnormal cells in the 50 ppm exposed females compared to the unexposed control group.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): ambiguous
There was no ovserved increase in the frequency of chromosomal abberations in females and no significant difference in the frequency of chromosomal abberations in males.
Executive summary:

Groups of 10 male and 10 female Fischer 344 rats each were exposed to 0, 5, 25, or 50 ppm of epichlorohydrin in air for 6 hours/day, 5 days/week for 4 weeks. This was part of a larger subchronic study. In most cases, 200 cells were scored per animal for various chromosomal aberrations. The frequency of aberrations found for all groups was quite low. While the 25 and 50 ppm male groups showed a doubling over controls, there was no consistent dose-response effect observed in these males. In addition, the number of chromosomal aberrations observed in the 5 ppm exposed males was decreased to a greater extent than were the increases observed in either 25 or 50 ppm males as compared to their controls. Statistical analysis by Fisher's exact probability test, a modified Wilcoxon test, and analysis of variance indicated that the differences in the males were not significant at the 5% level. There was no observed increase in the frequency of chromosomal aberrations found in the female rats exposed to 50 ppm epichlorohydrin as compared to their controls.

The results of this study indicate that exposure of rats to epichlorohydrin by the inhalation route does not produce chromosomal aberrations at the same rate as reported for comparable doses administered orally or intraperitoneally to mice.

The bone marrow cytogenetic study in Fischer 344 male and female rats following 30 days of inhalation exposure to epichlorohydrin (HET-K-001710-(13)) was a supplement to a 90- day subchronic study (HET-K-001710-(11)). These studies were sponsored by the Manufacturing Chemists Association.