2-chloro-5-(trifluoromethyl)pyridine

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vivo

Description of key information

CTF was not clastogenic in the mouse micronucleus test.

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental phase: 7 - 29 April 1983.

Reliability:

1 (reliable without restriction)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes (incl. QA statement)

Type of assay:

micronucleus assay

Species:

mouse

Strain:

C57BL

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and femal C57BL/6J mice (6-8 weeks old) were used for both phase I and Phase II of the study. The animals were supplied by the Animal Breeding Unit, Alderley Park, Macclesfield, Cheshire.
On arival the mice were housed ten per cage on mobile mouse racks and given food (Porton Combined Diet (PCD) supplied by Special Diets Services Ltd, Stepfield, Witham, Essex, UK) and filtered tap water (via an automated watering system) ad libitum.
The temperature of the animal cell was maintained in the range 20-26°C and a relative humidity range of 36-65%. Temperature and relative humidity were measured on a maximum and minimum thermometer and hygrometer respectively, and were recorded in the CTL Cleanside Temperature Record Book. Lighting was cycled with 12 hours light and dark each 24 hours. The animal cell was under negative pressure with respect to the access corridor and had approximately 22 air changes per hour.

Route of administration:

intraperitoneal

Vehicle:

Kraft Wesson Corn oil, supplied by Kraft Foods Ltd, Liverpool UK.

Details on exposure:

Dosing of the animals for the micronucleus test:
Animals were given a single dose, using doses equivalent to 80% or 50% of the LD50/7day by intraperitoneal injection. The lower dose level was used to ensure a test result in the event of deaths in the top dose and to allow the observation of a dose response, should the higher dose give a positive result.

Duration of treatment / exposure:

Single ip injection

Frequency of treatment:

once

Post exposure period:

24, 48 and 72 hours

Remarks:

Doses / Concentrations:
600 mg/kg i.p.
Basis:
other: based on 80% of i.p. LD50 (7day)

Remarks:

Doses / Concentrations:
375 mg/kg i.p.
Basis:
other: based on 50% i.p. LD50 (7 day)

No. of animals per sex per dose:

5 M and 5F (at the sampling times 24, 48 and 72 hours)

Control animals:

yes, concurrent vehicle

Positive control(s):

Cyclophosphamide
65 mg/kg i.p. in physiological saline
5M and 5F (at the sampling times 24, 48 and 72 hours)

Tissues and cell types examined:

Bone marrow from the femur

Details of tissue and slide preparation:

a) Femurs were removed and stripped of muscle
b) The iliac end of the femur was removed, and a fine paint brush wetted with a solutionn of albumen (6% w/v in saline) was dipped into the marrow canal.
c) 3 to 4 streaks of marrow suspension were then applied to appropriately labelled clean, dry microscopic slides.
d) The slides were allowed to air dry
e) The slides were then stained with polychrome methylene blue and eosin using a Ames Hema-Tek staining machine (Hema-Tek, Miles Laboratory Limited, Stoke Court, Stoke Pages, Slough, UK).
f) Slides were coded and scored blind.
g) 500 polychromatic erythrocytes were examined and the number containing micronuclei scored. The samples were also examined for evidence of cytotoxicity, which may be manifest in the ratio of different cell types in the bone marrow.

Evaluation criteria:

500 polychromatic erythrocytes were examined and the number containing micronuclei scored, for the test substance, control and positive control at the sampling times 24, 48 and 72 hrs. The samples were also examined for evidence of cytotoxicity, which may be manifest in the ratio of different cell types in the bone marrow. A statistically significant increase in polychromatic erythrocytes containing micronuclei is considered to be evidence of the clastogenic effect of the administered substance.

Statistics:

The results were analysed for significant difference from the control group using a one sided Student's 't' test.

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Positive controls validity:

valid

Table 1: Incidence of Micronuclei / 1000 Polychromatic Erythrocytes at Three Sampling Times

Group	Compound	Dose	Incidence of micronuclei/1000 cells
			24 hours	48 hours	72 hours
1	Control (corn oil)	10ml/kg	5.3	5.0	4.6
2	Cyclophosphamide	65mg/kg	45.8**	31.8**	5.6
3	CTF	600 mg/kg	5.3	4.5	4.5
4	CTF	375mg/kg	4.0	2.6	2.4

** Statistically significant difference p<0.01 Student's 't' Test (one-sided)

CTF gave negative results at all three sampling times when compared with the control. The test system positive control (cyclophosphamide) gave an elevated and statistically significant increase in micronuclei at the 24 hour and 48 hour sampling times. But had fallen to control values at the 72 hour sampling time. This type of response is expected for cyclophosphamide, and shows specificity of the system, as cyclophosphamide is short lived and therefore has a transient effect.

Conclusions:

Interpretation of results (migrated information): negative
CTF was not clastogenic in the mouse micronucleus test.

Executive summary:

CTF (2-chloro-5-trifluoromethylpyridine) is an intermediate in the manufacture of a herbicide.

CTF did not induce any statistically significant increase in the frequency of micronuclei when compared with control animals at any of the sampling times investigated.

Throughout the study the positive control substance cyclophosphamide showed the expected response.

These results indicate that CTF is not clastogenic in the mouse micronucleus test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vivo:

In a company communication 14 Sept 1982 (ICI Mond Division Medical Dept.) 2 -Chloro-5-(trifluoromethyl) pyridine (CTF) is stated to be not mutagenic in bacteria (Ames and E-Coli tests). No study report is available for these bacteria tests. However, in a well-reported mouse micronucleus study, CTF did not induce any statistically significant increase in the frequency of micronuclei when compared with control animals at any of the sampling times investigated.

Throughout the study the positive control substance cyclophosphamide showed the expected response.

These results indicate that CTF is not clastogenic in the mouse micronucleus test.

Justification for selection of genetic toxicity endpoint
Well conducted in-vivo mutagenicity test

Justification for classification or non-classification

CTF was not mutagenic in-vivo and therefore classification under CLP Regulation (EC) 1272/2008 is not justified.