4-bromo-3,3,4,4-tetrafluorobut-1-ene

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Remarks:

Two-week Inhalation Toxicity Study

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

December 4 2001 - December 10 2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Study is well documented, but was not conducted according to national or international guidelines, and has a non-standard duration.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Principles of method if other than guideline:

- Principle of test: The purpose of this study was to assess the potential subchronic toxicity of exposure to the test item
- Short description of test conditions: Young adult male rats (10 rats/exposure concentration) were exposed to atmospheres containing 0 or 1000 ppm of the test item for 6 hours per day, over a 2-week period for a total of 9 exposures.
- Parameters analysed / observed: Body weight was determined daily, and food consumption was determined weekly. Clinical signs of toxicity were monitored throughout the study. Blood and urine samples were collected at the end of the exposure period from 10 rats/concentration for evaluation of clinical pathology and urinalysis parameters. Additional blood samples were collected from each rat for determination of thyroid hormone concentrations. After the last exposure, 5 rats/concentration for each of the 3 test substances underwent gross necropsy. Selected tissues were processed for histopathology and examined. In addition, a liver sample was collected from each rat for determination of hepatic β-oxidation activity. After an approximate 2-week recovery period, blood and urine samples were collected from all surviving rats for evaluation of clinical pathlology and urinalysis parameters. All surviving rats underwent gross necropsy, and selected tissues were processed for histopathology and examined.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-bromo-3,3,4,4-tetrafluorobut-1-ene

EC Number:

242-440-8

EC Name:

4-bromo-3,3,4,4-tetrafluorobut-1-ene

Cas Number:

18599-22-9

Molecular formula:

C4H3BrF4

IUPAC Name:

4-bromo-3,3,4,4-tetrafluorobut-1-ene

Test material form:

liquid

Test animals

Species:

rat

Strain:

other: Crl:CD®(IGS)BR

Details on species / strain selection:

Rats have historically been used in safety evaluation studies for inhalation toxicity testing. The Crl:CD®(SD)IGS BR rat was selected based on consistently acceptable health status and on extensive experience with the strain at the testing laboratory.

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc. Raleigh, North Carolina.
- Females (if applicable) nulliparous and non-pregnant: N/A
- Age at study initiation: approximately 9 weeks old
- Weight at study initiation: 273 - 326 grams
- Fasting period before study:
- Housing: Rats were housed singly in stainless steel, wire-mesh cages suspended above cage boards.
- Diet (e.g. ad libitum): PMI Nutrition International, Inc. Certified Rodent LabDiet® 5002 was available ad libitum except during exposure and fasting periods prior to necropsy.
- Water (e.g. ad libitum): tap water was available ad libitum
- Acclimation period: 6 day quarantine

DETAILS OF FOOD AND WATER QUALITY:
Water samples were analyzed for total bacterial counts, and the presence of coliforms, lead, and other contaminants.
Feed samples were analyzed for total bacterial, spore, and fungal counts. The attending laboratory technician confirmed no conditions were present that affected the validity of the study.
Certified animal feed is guaranteed by the manufacturer to meet specified nutritional requirements and not to exceed stated maximum concentrations of key contaminants, including specified heavy metals, aflatoxin, chlorinated hydrocarbons, and organophosphates. The presence of these contaminants below the maximum concentration stated by the manufacturer would not be expected to impact the integrity of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 1˚C
- Humidity (%): 50 ± 10%
- Air changes (per hr): Not provided.
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 10 December 2001 To: 04 January 2002

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: Air, and Nitrogen to sweep the vapor

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: All exposure chambers were constructed of stainless steel and glass (NYU style) with a nominal internal volume of 150 L, chosen so that the total body volume of the test animals did not exceed 5% of the chamber volume.
- Method of holding animals in test chamber: wire mesh cages
- Source and rate of air: Houseline air system, not rate provided
- Method of conditioning air: Not provided.
- System of generating vapor: heated glass flask with a Harvard Apparatus Model 22 Compact Infusion Pump
- Temperature, humidity, pressure in air chamber: 23 ± 2°C, relative humidity 50 ± 10%,
- Air flow rate: Not provided as separate value to air change rate.
- Air change rate: at least 12 air changes per hour
- Method of particle size determination: N/A
- Treatment of exhaust air: exhausted through a dry-ice cold trap, followed by an MSA charcoal/HEPA filter cartridge prior to discharge into the fume hood.

TEST ATMOSPHERE
- Brief description of analytical method used: The atmospheric concentration was determined at approximately 30-minute intervals by gas chromatography.
- Samples taken from breathing zone: yes, via sampling port.

VEHICLE (if applicable) - N/A

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Atmospheric concentration of the test substances was determined from a standard curve derived from gas standards. Standards were prepared prior to the first and sixth exposures, and were refrigerated during the remainder of the exposure days. Standards were prepared by injecting known volumes of test item liquid into bags that contained known volumes of air. Distribution of the test item in the test chambers was determined prior to initiation of the first exposure, and was found to be homogenous.

Duration of treatment / exposure:

14 days

Frequency of treatment:

9 exposures over 14 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

1 000 ppm

Doses / concentrations 2

Dose / conc.:

0 ppm

No. of animals per sex per dose:

10 rats/exposure concentration

Control animals:

yes, sham-exposed

Positive control:

No

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Not specified
- Time schedule: N/A

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: before and after each exposure, with group clinical observations made during exposures.

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Not specified

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Not specified

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Not specified

HAEMATOLOGY: Yes
- Time schedule for collection of blood: 11 days after initiation of study
- Anaesthetic used for blood collection: light carbon dioxide anesthesia
- Animals fasted: Yes - overnight prior to collection
- How many animals: all animals in study
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: 11 days after initiation of study
- Animals fasted: Yes - overnight prior to collection
- How many animals: all animals in study
- Parameters checked in table [No.2] were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: 11 days after initiation of study
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table [No.3] were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: prior to exposure, 3 times during each exposure, and after each exposure
- Dose groups that were examined: all animals in study
- Battery of functions tested: rats were checked for an alerting response to an auditory stimulus

IMMUNOLOGY: No

BRONCHOALVEOLAR LAVAGE FLUID (BALF): No

LUNG BURDEN: No

OTHER: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see table 4 & 5)

Other examinations:

THYROID FUNCTION: Blood was collected from all animals following the last exposure. Serum was prepared and stored between -65 and -85°C until analyzed for thyroid hormone concentrations. Serum thyroxine (T4), triiodothyronine (T3), and thyroid stimulating hormone (TSH) concentrations were measured using commercially available radioimmunoassay (RIA) kits.

β-OXIDATION ACTIVITY: The first 5 rats from each group had their livers removed, weighed, and then a portion was homogenized (1 gram tissue/4 mL buffer) in homogenization buffer (50 mM Tris-HCl, 50 mM Trizma-base, 0.25 M sucrose, and 5.4 mM EDTA, pH 7.4). Hepatic peroxisomes were prepared using differential centrifugation. The resulting peroxisomal pellets were resuspended in the homogenization buffer, aliquoted, and stored between -65 and -85˚C until analyzed for peroxisomal β-oxidation activity. The peroxisomal suspensions were diluted to a protein concentration of approximately 0.5 mg/mL. Peroxisomal β-oxidation activity was determined using [14C]palmitoyl CoA as the substrate. The protein content of the peroxisomes was determined before and after analysis by the Biorad method. Final rate calculations were made using the post-assay protein concentrations.


RECOVERY CLINICAL PATHOLOGY:
Due to the presence of systemic toxicity, and alterations in clinical pathology parameters at the end of dosing, complete clinical pathology evaluations, excluding plasma fluoride, were performed at the end of the recovery period (test day 25). Blood was collected for plasma fluoride, but was not evaluated.

Statistics:

Significance was judged at p < 0.05. Statistical parameters are described in table 7.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Description (incidence and severity):

There were no test substance-related effects for body weight or weight gain in males exposed to 1000 ppm. Males exposed to 1000 ppm of had significantly higher body weight gain during test days 4-7, and over the interval of test days 0-11. Since there were no adverse, test substance-related effects on organ weight or on the clinical condition of the animal, the higher weight gain for rats exposed to 1000 ppm was considered to be spurious. (Table 7)

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Description (incidence and severity):

Males exposed to 1000 ppm had significantly higher food efficiency during test days 0-7 due to the significantly higher body weight gain during this interval. Since there were no adverse, test substance-related effects on organ weight or on the clinical condition of the animals, the higher weight gain and food efficiency for rats exposed to 1000 ppm were considered to be spurious. (Table 8)

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Rats exposed to 1000 ppm had minimally increased reticulocytes (group mean was 126% of control group mean) at test day 11. This change indicates a minimal increase in red cell turnover; however there was no effect on red cell mass parameters, so the changes were considered non-adverse. At test day 25 (after 14 days of recovery), reticulocytes in rats previously exposed to H-25111 were similar to control group values. Rats exposed to 1000 ppm had no other significant changes in hematology or coagulation. (Tables 9 & 10)

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

(Table 11)

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There were no compound-related organ weight effects at either sacrifice in animals exposed to the test item

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Gross observations noted were sporadic across groups and were not test substance-related.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no compound-related microscopic observations for the test item

Effect levels

Key result

Dose descriptor:

NOEL

Effect level:

> 1 000 ppm

Based on:

test mat.

Sex:

male

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

Table 7: Mean Body weights of male rats

Days on test	Mean body weight males (1000ppm)
Exposure phase
0	299.7 12.8 (10)
1	301.9 12.8 (10)
2	311.6 15.2 (10)
3	317.9 17.1 (10)
4	326.1 16.5 (10)
7	347.8 20.5 (10)
8	250.8 21.2 (10)
9	356.9 22.7 (10)
10	361.2 23.7 (10)
11	333.7 22.3 (10)
Recovery Phase
14	373.4 33.2 (5)
18	401.7 40.2 (5)
21	420.5 38.1 (5)
25	404.3 47.9 (5)

 

Table 8: Food Consumption

Animal #	Food Cons. g/anm/day Day 7	Food Cons. g/anm/day Day 14	Food Cons. g/anm/day Day 21	Food Cons. g/anm/day Day 25
653804	16.8
653805	24.4
653806	28.6
653807	30.3
653808	24.6
653809	32.7	30.9	37.7	28.8
653810	27.5	20.0	23.3	12.9
653811	27.7	23.6	27.6	22.3
653812	30.8	26.6	31.5	23.0
653813	27.2	23.2	20.5	24.4

 

ABBREVIATIONS FOR HEMATOLOGY & CLINICAL CHEMISTRY:

General:

CS - clotted specimen

NT - not taken or not performed
QNS - quantity not sufficient for testing

> - greater than < - less than

 

Individual Hematology Values:

RBC - erythrocyte count
HGB - hemoglobin concentration HCT - hematocrit
MCV - mean corpuscular volume MCH - mean corpuscular hemoglobin

MCHC - mean corpuscular hemoglobin concentration RDW - red cell volume distribution width

RETIC - absolute reticulocyte count PLT - platelet count
WBC - total leukocyte count

ANEU - absolute neutrophils
ALYM - absolute lymphocytes
AMON - absolute monocytes
AEOS - absolute eosinophils
ABAS - absolute basophils
ALUC - absolute large unstained cells Poik - poikilocytosis

Poly - polychromasia
PLT MORPH - platelet morphology

CLSE - severe platelet clumping noted CLSL - slight platelet clumping noted

LPO - occasional large NAN - no abnormalities

 

Individual Coagulation Values:

PHEM - plasma hemolysis PLIP - plasma lipemia PICT - plasma icterus

platelets notednoted

PT - prothrombin time
APTT - activated partial thromboplastin time

 

Individual Serum and Plasma Chemistry Values:

SHEM - serum hemolysis SLIP - serum lipemia SICT - serum icterus

AST - aspartate aminotransferase ALT - alanine aminotransferase SDH - sorbitol dehydrogenase

ALKP - alkaline phosphatase BILI - total bilirubin

BUN - urea nitrogen CREA - creatinine CHOL - cholesterol TRIG - triglycerides GLUC - glucose

TP - total protein ALB - albumin

GLOB - globulin
CALC - calcium
IPHS - inorganic phosphorous

NA - sodium
K - potassium

CL - chloride
PHEM - plasma hemolysis from blood sample for fluoride determination PLIP - plasma lipemia from blood sample for fluoride determination PICT - plasma icterus from blood sample for fluoride determination PFLU - plasma fluoride

 

Table 9: Hematology

 

Male, Group IX - 1000 ppm - Day 11

Animal #	RBC X10^6/µL	HGB g/dL	HCT %	MCV fL	MCH pg	MCHC g/dL	RDW %	RETIC X10^3/µL	PLT X10^3/µL	WBC X10^3/µL	ANEU X10^3/µL
653804	7.26	14.0	43.9	60.5	19.3	32.0	12.2	250.8	1322	15.30	2.14
653805	7.98	15.6	47.0	58.8	19.6	33.3	11.8	217.0	1091	08.90	1.39
653806	7.71	14.7	46.5	60.3	19.1	31.7	13.3	299.4	1143	11.70	1.64
653807	7.80	14.3	45.1	57.8	18.4	31.8	12.4	246.8	1380	09.86	1.73
653808	7.90	15.4	46.9	59.4	19.4	32.7	12.1	248.2	1364	11.34	2.57
653809	6.82	14.5	44.1	64.6	21.2	32.8	13.0	256.0	1441	12.19	2.37
653810	7.71	14.8	45.6	59.2	19.2	32.4	12.5	214.9	1488	08.82	2.59
653811	7.45	14.6	45.4	60.9	19.6	32.2	12.0	245.4	1607	08.72	1.14
653812	7.97	15.1	47.1	69.1	19.0	32.2	13.2	250.4	1411	15.93	3.68
653813	7.78	15.3	48.6	62.5	19.6	31.4	12.2	283.0	1469	13.01	2.74

Male, Group IX - 1000 ppm - Day 25

Animal #	RBC X10^6/µL	HGB g/dL	HCT %	MCV fL	MCH pg	MCHC g/dL	RDW %	RETIC X10^3/µL	PLT X10^3/µL	WBC X10^3/µL	ANEU X10^3/µL
653809	7.49	15.2	47.6	63.6	20.2	31.8	13.5	16.01	894	13.96	2.43
653810	CS	CS	CS	CS	CS	CS	CS	CS	CS	CS	CS
653811	7.46	14.2	45.2	60.5	19.0	31.4	12.8	221.2	1297	10.32	1.55
653812	8.14	14.9	48.1	59.0	18.3	31.0	13.1	213.1	1587	15.22	2.82
653813	7.82	15.3	49.0	62.7	19.6	31.3	13.0	223.9	1482	13.05	2.10

 

Male, Group IX - 1000 ppm - Day 11

Animal #	ALYM X10^3/µL	AMON X10^3/µL	AEOS X10^3/µL	ABAS X10^3/µL	ALUC X10^3/µL	Poik	Poly	PLT MORPH
653804	12.45	0.36	0.09	0.13	0.12	NAN	1+	NAN
653805	7.01	0.20	0.11	0.10	0.08	NAN	1+	NAN
653806	9.45	0.21	0.12	0.17	0.11	NAN	1+	NAN
653807	7.75	0.20	0.07	0.05	0.06	NAN	2+	NAN
653808	8.43	0.13	0.06	0.09	0.07	NAN	1+	NAN
653809	9.40	0.18	0.11	0.06	0.07	NAN	2+	NAN
653810	5.87	0.24	0.06	0.03	0.04	NAN	1+	NAN
653811	7.21	0.18	0.10	0.04	0.05	1+	1+	NAN
653812	11.61	0.32	0.09	0.12	0.11	1+	1+	NAN
653813	9.70	0.19	0.20	0.09	0.08	NAN	2+	NAN

 

Male, Group IX - 1000 ppm - Day 25

Animal #	ALYM X10^3/µL	AMON X10^3/µL	AEOS X10^3/µL	ABAS X10^3/µL	ALUC X10^3/µL	Poik	Poly	PLT MORPH
653809	10.85	0.32	0.13	0.11	0.11	1+	1+	NAN
653810	CS	CS	CS	CS	CS	CS	CS	CS
653811	8.35	0.20	0.08	0.07	0.07	1+	2+	NAN
653812	11.76	0.32	0.08	0.15	0.09	1+	1+	NAN
653813	10.32	0.30	0.11	0.13	0.10	NAN	1+	NAN

 

Table 10: Coagulation

Animal #	PHEM	PLIP	PICT	PT	APTT
				(sec)	(sec)
Male, Group IX - 1000 ppm - Day 11
653804	None	None	None	15.4	17.7
653805	None	None	None	15.2	14.8
653806	None	None	None	15.3	19.9
653807	None	None	None	14.7	16.3
653808	None	None	None	14.7	17.7
Male, Group IX - 1000 ppm - Day 25
653809	None	None	None	14.9	19.4
653810	None	None	None	15.5	19.1
653811	None	None	None	14.8	17.7
653812	None	None	None	14.6	22
653813	None	None	None	14.7	21

 

Table 11: Clinical Chemistry

 

Male, Group IX - 1000 ppm - Day 11

	SHEM	SLIP	SICT	AST	ALT	SDH	ALKP	BILI	BUN	CREA	CHOL
				U/L	U/L	U/L	U/L	mg/dL	mg/dL	mg/dL	mg/dL
653804	None	None	None	101	48	23.1	228	0.1	15	0.27	58
653805	None	None	None	100	53	21.7	282	0.1	14	0.33	54
653806	Trace	None	None	105	40	16.3	181	0.1	14	0.32	79
653808	None	None	None	99	38	18.9	192	0.12	13	0.37	60
653809	None	None	None	94	46	18.8	274	0.14	17	0.32	47
653810	None	None	None	94	33	15	169	0.12	15	0.27	62

 

Male, Group IX - 1000 ppm H-25111 - Day 11
	PHEM	PLIP	PICT	PFLU (µg/mL)
653804	None	None	None	0.1
653805	None	None	None	0.1
653806	None	None	None	0.1
653807	None	None	None	0.1
653808	None	None	None	0.1

 

 

Male, Group IX - 1000 ppm - Day 25

Animal #	SHEM	SLIP	SICT	AST	ALT	SDH	ALKP	BILI	BUN	CREA	CHOL
				U/L	U/L	U/L	U/L	mg/dL	mg/dL	mg/dL	mg/dL
653809	TRACE	None	None	90	42	18.1	214	0.1	14	0.29	43
653810	TRACE	None	None	86	40	15.2	153	<0.10	17	0.3	52
653811	TRACE	None	None	82	32	13.9	186	0.1	15	0.36	79
653812	TRACE	None	None	82	34	16.1	120	<0.10	12	0.33	99
653813	TRACE	None	None	80	28	17.3	195	0.11	15	0.36	59

 

Male, Group IX - 1000 ppm - Day 25

Animal #	TRIG	GLUC	TP	ALB	GLOB	CALC	IPHS	NA	K	CL
	mg/dL	mg/dL	g/dL	g/dL	g/dL	mg/dL	mg/dL	mmol/L	mmol/L	mmol/L
653809	42	103	6.5	4.0	2.5	11.0	9.6	144.6	5.46	98.1
653810	21	91	6.3	4.1	2.2	10.8	8.6	143.7	5.40	97.8
653811	27	103	6.5	4.1	2.4	11.0	9.2	146.1	3.08	101.9
653812	84	108	6.9	4.2	2.7	11.4	8.0	147.0	5.32	99.8
653813	37	95	6.6	4.4	2.2	10.7	8.4	147.7	6.02	102.3

 

Table 12: Thyroid Function & ß-Oxidation data

	β-Oxidation	TSH	Triiodothyronine (T3)	Thyroxine (T4)
Animal #	(nmol/min-mg protein)	(ng/mL)	(ng/dL)	(ng/dL)
653804	17.5	7.772	59.683	4.048
653805	16.5	4.469	85.695	4.993
653806	15.2	8.885	73.49	5.035
653807	15.4	5.779	79.156	3.696
653808	15.6	5.51	85.574	4.91
653809	a	7.656	64.098	5.141
653810	a	5.625	59.642	4.041
653811	a	4.586	70.28	4.89
653812	a	5.439	69.987	4.279
653813	a	5.285	83.285	4.765

FOOTNOTES:

1. a  Hepatic β-oxidation analyses were not performed on this animal.


2. b  Hepatic β-oxidation analyses for this animal was not reported due to missing identification on the sample tubes.

Applicant's summary and conclusion

Conclusions:

Rats exposed to 1000 ppm test item had no adverse change in hematology, coagulation, clinical chemistry, urinalysis, or fluoride parameters. The only treatment-related, but non-adverse, change in rats exposed to 1000 ppm was a minimal increase in reticulocytes, without an effect on red cell mass. Therefore, under the conditions of this study and for the parameters measured, the no adverse effect level for male rats was 1000 ppm, the only exposure concentration administered.

Executive summary:

Introduction

The purpose of this study was to assess the potential subchronic toxicity of exposure to the test item in adult rats. Young adult male Crl:CD®(IGS)BR rats (10 rats/exposure concentration) were exposed to atmospheres containing 1000 ppm test item for 6 hours per day, over a 2-week period for a total of 9 exposures.

 

Observations

Body weight was determined daily, and food consumption was determined weekly. Clinical signs of toxicity were monitored throughout the study. Blood and urine samples were collected at the end of the exposure period from 10 rats/concentration for evaluation of clinical pathology and urinalysis parameters. Additional blood samples were collected from each rat for determination of thyroid hormone concentrations. After the last exposure, 5 rats/concentration for each of the 3 test substances underwent gross necropsy. Selected tissues were processed for histopathology and examined. In addition, a liver sample was collected from each rat for determination of hepatic β-oxidation activity. After an approximate 2-week recovery period, blood and urine samples were collected from all surviving rats for evaluation of clinical pathlology and urinalysis parameters. All surviving rats underwent gross necropsy, and selected tissues were processed for histopathology and examined.

 

Results

There were no test substance-related, toxicologically significant effects on body weight, weight gain, food consumption, food efficiency, or clinical signs of toxicity in males exposed to the test item at 1000 ppm.

 

Exposed animals had no adverse changes in hematology, coagulation, clinical chemistry, urinalysis, or fluoride parameters. The only treatment-related, but non-adverse, change was a minimal increase in reticulocytes, without an effect on red cell mass.

 

There were no test substance related effects on organ weights or tissue morphology.

 

Test substance related changes in thyroid homeostasis were observed. Serum T3 and T4 concentrations were significantly decreased in rats following exposure. However, serum TSH was not affected. While these alterations suggest that the test item may be capable of modulating thyroid hormone homeostasis, these alterations may be transient effects since thyroid weight and histopathology were not affected.

 

Hepatic β-oxidation activity was similar to control in exposed rats.

 

Conclusions

The no-observed-effect level (NOEL) for this study is defined as the highest dose at which toxicologically important effects attributable to the test substance were not detected. Thus for this study, the NOEL is equivalent to the NOEL as defined by the United States Environmental Protection Agency (1985), and the no-observed-adverse effect level (NOAEL) as defined by the European Union (1994). Under the conditions of the study, the NOEL for the test item was 1000 ppm, the highest concentration tested.