Bromochloromethane

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Test method equivalent or similar to OECD Guideline 413.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1960

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

yes

Remarks:

(Only two dose concentrations were tested in males).

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Bromochloromethane

EC Number:

200-826-3

EC Name:

Bromochloromethane

Cas Number:

74-97-5

Molecular formula:

CH2BrCl

IUPAC Name:

bromo(chloro)methane

Details on test material:

- Name of test material (as cited in study report): bromochloromethane
- Analytical purity: >99%

Test animals

Species:

rat

Strain:

not specified

Sex:

male/female

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

CHAMBER DESCRIPTION: 1700-liter capacity water-sealed chambers.

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

114 days

Frequency of treatment:

7h/day, 5 days/week.

Doses / concentrations

Remarks:

Doses / Concentrations:
400 ppm (females), 500 ppm (males and females) and 1000 ppm (males and females)
Basis:
nominal conc.

No. of animals per sex per dose:

500 and 1000 ppm-dose groups: 20 animals/sex/group.
400 ppm-dose group: 10 females.

Control animals:

yes, concurrent no treatment

Details on study design:

Since it was evident that female rats were the only group which was significantly affected by exposures to 500 ppm, it was deemed desirable to expose another group of female rats to 400 ppm to observe their response.

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

BODY WEIGHT: Yes
- Time schedule for examinations: The animals were weighed twice a week until it was evident that growth was essentially normal and once a week thereafter.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at study termination.
- Animals fasted: Yes.
- How many animals: on representative animals of the unexposed group and the 1000 ppm dose group.
- Parameters checked in table [No.3] were examined: RBC, WBC and differential count of Neutrophils, Lymphocytes, Monocytes and Eosinophils.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at study termination.
- Animals fasted: Yes
- How many animals: on representative animals of all dose groups and control groups.
- Parameters checked in table [No. 2] were examined: blood bromide, blood urea-nitrogen (BUN) and blood non-protein-nitrogen (NPN).

Sacrifice and pathology:

SACRIFICE: all rats were fasted overnight and killed by decapitation the day following their last exposure.
GROSS PATHOLOGY: Yes (see table No. 1). After gross pathological examination was made, the lungs, heart, liver, kidney, spleen and testes were removed and weighed.
HISTOPATHOLOGY: Yes. Portions of the lungs, heart, liver, kidney, spleen, testes, pancreas and adrenals were examined microscopically.

Statistics:

The "t" test was used to determine the significance of the organ weight differenes. A probability (P) of 0.05 or less was considered as significant.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Bromide blood levels were elevated in males exposed at ≥500 ppm and females exposed at ≥ 400 ppm.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Increase in weight of the liver in males exposed at ≥500 ppm and females exposed at ≥400 ppm.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

In males and females exposed to 1000 ppm.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Females in the ≥500 ppm groups and males in the 1000 ppm group.

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
Animals exposed to bromochloromethane were normal in appearance and activity.

BODY WEIGHT AND WEIGHT GAIN
The average body weight and growth of the exposed animals were normal.

HAEMATOLOGY
Hematological values were within normal limits.

CLINICAL CHEMISTRY
Blood bromide levels were elevated in females exposed to ≥400 ppm and in males exposed to ≥500 ppm.

ORGAN WEIGHTS
A small increase in weight of the liver was noted in males exposed to 500 ppm. Nevertheless, since no pathological changes were seen in the 500 ppm-dose group, it probably indicates that the organ was only under slight stress. The average liver weight in females exposed to 500 ppm was high. The average liver and kidney weights were elevaded in males and females exposed to 1000 ppm.

GROSS PATHOLOGY
Fatty and enlarged livers were seen grossly when female rats exposed to 1000 ppm were sacrified. Organs of exposed males appeared normal at autopsy.

HISTOPATHOLOGY: NON-NEOPLASTIC
A very slight proliferation of the bile duct epithelium with very slight portal fibrosis and inflammation was seen in males exposed to 1000 ppm. There was some cloudy swelling of the parenchymal cells in the midzonal areas spreading to the central areas of the lobule. Numerous parenchymal cells in the midzonal area and portal area contained many small vacuoles. Slight pathological changes were seen in females exposed to 500 ppm: bile duct epithelial proliferations and very slight portal fibrosis, together with occasional large and small vacuoles in parenchymal cells of the midzonal areas. Similar changes to those described for male rats were seen in females exposed to 1000 ppm, in addition of some portal fibrosis in the liver.

Effect levels

1

Dose descriptor:

NOAEC

Effect level:

500 ppm

Based on:

test mat.

Sex:

male

Basis for effect level:

other: histopathology (pathological changes in the liver) (equiv. to 2645.88 mg/m3)

2

Dose descriptor:

NOAEC

Effect level:

400 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

other: histopathology (pathological changes in the liver) (equiv. to 2116.71 mg/m3)

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1. Summary of Terminal Average Body and Organ Weights of Animals Receiving Repeated 7-Hour Exposures to Bromochloromethane (CH2BrCl).

Specie	Sex	Group	Ratio of survival	Final average body weight, g	Organ Weights, g/100 g body weight
					Lung	Heart	Liver	Kidney	Spleen	Testes
Rat	M	Unexposed control	19/20	341	0.55	0.31	2.46	0.68	0.29	0.87
	M	1000 ppm	17/20	306	0.56	0.32	3.20^d	0.75^d	0.32	0.85
	M	500 ppm	17/20	300	0.56	0.34	2.77^d	0.69	0.32	0.82
	F	Unexposed control	17/20	203	0.73	0.37	2.67	0.71	0.36
	F	1000 ppm	19/20	206	0.70	0.38	3.65^d	0.82^d	0.35
	F	500 ppm	19/20	210	0.70	0.38	3.05^d	0.75	0.38
	F	Unexposed control	12/12	215	0.64	0.39	2.70	0.76	0.28
	F	Air exposed control	12/12	220	0.64	0.34	2.77	0.75	0.32
	F	400 ppm	9/10	232	0.63	0.38	2.98^bb	0.78	0.25

Probability values (P): a = P > 0.05; b = P = 0.01-0.05; bb = P ≈ 0.045; c = P = 0.001-0.01; d = P < 0.001.

Table 2. Summary of Average Blood Bromide, Blood Urea-Nitrogen and Blood Non-Protein-Nitrogen Levels in Animals Exposed Repeatedly to the Vapours of Bromochloromethane in Air.

Specie	Sex	Months on exposure, day bled	Vapour conc. (ppm)	Blood Bromide			Blood Nitrogen
				No. of animals	Mg Br-/ 100 ml	Analytical method	No. of animals	Urea N	Total NPN
								mg/100 ml	mg/100 ml
Rat	M	4 Thurs.	0	3	8	W	2	14.8
	M	4 Thurs.	1000	3	122	W	2	13.9
	M	4 Thurs.	500	3	88	W	2	16.0
	F	4 Fri.	0	3	5	W	2	15.2
	F	4 Fri.	1000	3	122	W	2	15.9
	F	4 Fri.	500	3	83	W	2	18.7
	F	6 Wed.	0	3	0.9	S	8	20.8	48
	F	6 Wed.	400	3	73	S	3	12.9	47

*Analytical method for blood bromide:

W Wuth’s: Hepler, O.E., Manual of Clinical Laboratory Methods, Charles C Thomas, Springfield, Illinois, 1951.

S Shrader’s: Shrader, S.A., et al., Ind. Eng. Chem. Anal. Ed. 14:1 (1942).

Table 3. Average Terminal Hematological Values for Animals Receiving Repeated 7-Hour Exposures to Bromochloromethane.

Treatment	Sex	No. of animals	RBC x 10^6	WBC x 10^3	Differential Count (%)
					Neutrophils	Lymphocytes	Monocytes	Eosinophils
Unexposed control	F	5	8.8	16.9	14.2	82.9	0.4	3.0
1000 ppm	F	10	8.7	14.4	18.9	79.5	1.0	1.5

Applicant's summary and conclusion

Conclusions:

On the basis of the pathological changes observed in the liver, the inhalative NOAEC of bromochloromethane was established to be 500 ppm (2645.88 mg/m3) for males and 400 ppm (2116.71 mg/m3) for females.

Executive summary:

20 male and 20 female rats were exposed in 114 days to 500 and 1000 ppm. The exposures were for seven hours per day and given five days a week. Since it was evident that female rats were the only group which was significantly affected by exposures to 500 ppm, a 400 ppm-dose group was including only females was added. A fourth group was maintained in the animal quarters at all times as unexposed controls. The animals were weighed twice a week until it was evident that growth was essentially normal and once a week thereafter. Terminal hematological examinations were made on representative animals and all rats were subjected to gross pathological and histopathological examinations. Exposed animals were normal in appearance, activity and growth. Hematological values were within normal limits as were BUN levels. Blood bromide levels were found elevated in females exposed to ≥400 ppm and in males exposed to ≥500 ppm. Pathological changes in the liver were seen in males exposed to 1000 ppm of bromochloromethane: it was seen a very slight proliferation of the bile duct epithelium with very slight portal fibrosis and inflammation. Besides, there was some cloudy swelling of the parenchymal cells in the midzonal areas spreading to the central areas of the lobule and numerous parenchymal cells in the midzonal area and portal area contained many small vacuoles. Pathological changes in the liver were seen at a lower dose-level in females: females exposed to 500 ppm showed bile duct epithelial proliferations and very slight portal fibrosis, together with occasional large and small vacuoles in parenchymal cells of the midzonal areas. Similar changes to those described for male rats were seen in females exposed to 1000 ppm, in addition of some portal fibrosis in the liver. On the basis of the pathological changes observed in the liver, the NOAEC was established to be 500 ppm (or 2645.88 mg/m3) for males and 400 ppm (or 2116.71 mg/m3) for females.