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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented, published non-GLP study
Cross-reference
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Ten and Ninety-Day Toxicity Studies of 1,2-Dichloroethane in Sprague-Dawley Rats
Author:
Daniel FB, Robinson M, Olson GR, York RG &‌ Condie LW
Year:
1994
Bibliographic source:
Drug and Chemical Toxicology, 17:463-477

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Deviations:
not specified
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
1,2-dichloroethane was purchased from Aldrich Chemical Co. (Milwaukee, Wisconsin, USA); Lot. No. 0605 ML for the 10-day study and Lot. No. 9402 PL for the 90-day study. The purity was verified by GC/MS, and there were no detectable impurities.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Portage, MI, USA (10-day study); Charles River Laboratories, Raleigh, NC, USA (90-day study); viral antibody-free
- Age at study initiation: Approx. 8 weeks old
- Housing: Group-housed by sex in hanging polycarbonate cages containing hardwood chip bedding (10-day study); group-housed by sex in elevated wiremesh cages (90-day study)
- Diet: Purina Certified Rodent Chow 5002 (Ralston Purina Co., St. Louis, MO, USA), ad libitum
- Water: Deionized drinking water, ad libitum
- Acclimation period: 10 days

The rats were quarantined in a temperature and humidity controlled room on a 12 hour light-cycle for 10 days before treatment. Animals were individually identified by ear tag, and randomly assigned to vehicle and treatment groups using a computer-generated set of random numbers. A color coded identification card on each cage indicated the treatment group.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS
Dosing solutions were prepared fresh daily by appropriate dilution with corn oil from a stock solution. Animal dosages were determined weekly from individual body weights.

VEHICLE
- Justification for use and choice of vehicle: Corn oil is a standard vehicle for studies of this type.
- Amount of vehicle: A dosing volume of 1 mL/kg bw was used.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
No data
Duration of treatment / exposure:
1) 10 days
2) 90 days
Frequency of treatment:
Once daily
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
10-day study: 0, 10, 30, 100, and 300 mg/kg bw/d
Basis:
actual ingested
Remarks:
Doses / Concentrations:
90-day study: 0, 37.5, 75, and 150 mg/kg bw/d
Basis:
actual ingested
No. of animals per sex per dose:
10 animals
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The highest dose group was approximately 44 % of the LD50 for the rat (10-day study).
Positive control:
No

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS:
- Time schedule: Daily

BODY WEIGHT:
- Time schedule: Initially, on days 4 and 8, and at necropsy (10-day study); weekly (90-day study)

FOOD CONSUMPTION:
- Time schedule: Twice weekly

WATER CONSUMPTION:
- Time schedule: Twice weekly

OPHTHALMOSCOPIC EXAMINATION: (90-day study only)
- Time schedule: Prior to treamtent and during the last week on study
- Dose groups that were examined: All dose groups

HAEMATOLOGY:
- Time schedule for collection of blood: At necropsy
- Anaesthetic used for blood collection: Yes (pentobarbital, 60 mg/kg bw, i.p.)
- Animals fasted: Yes, for approx. 18 hours prior to sacrifice
- How many animals: 100 animals (10-day study), 80 animals (90-day study)
- Parameters examined: White and red blood cell count, haemoglobin concentration and haematocrit (10-day study); platelet count and white blood cell differentials were measured in addtion in the 90-day study.

CLINICAL CHEMISTRY:
- Time schedule for collection of blood: At necropsy
- Animals fasted: Yes, for approx. 18 hours prior to sacrifice
- How many animals: 100 animals (10-day study), 80 animals (90-day study)
- Parameters examined: Glucose, blood urea nitrogen, creatinine, cholesterol and calcium concentrations, and alkaline phosphatase, aspartate aminotransaminase, alanine aminotransaminase and lactate dehydrogenase activities (10-day study); total bilirubin, total protein, albumin, sodium and potassium concentrations were measured in addition in the 90-day study.

URINALYSIS: (90-day study only)
- Time schedule for collection of urine: During the final week
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined: Protein, glucose and bilirubin concentration and pH value and occult blood

OTHER:
At necropsy, the weights of the following organs were recorded: Brain, liver, spleen, lungs, thymus, kidneys, adrenal glands, heart and gonads
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (brain, liver, spleen, lungs, thymus, kidneys, adrenal glands, heart, gonads, skin, mandibular and mesenteric lymph nodes, mammary gland, thigh muscle, sciatic nerve, sternebrae, oesophagus, stomach, duodenum, jejunum, tongue, salivary gland, ileum, colon, caecum, rectum, pancreas, urinary bladder, seminal vesicles, prostate, uterus, nasal cavity/turbinates, pituitary gland, preputial or clitoral gland, Zymbal's gland, aorta, thyroid, parathyroids and any gross lesions)
Other examinations:
none
Statistics:
Males and females were considered separately in all statistical analyses. The high mortality rate in the 300 mg/kg bw/d group (10-day study) prevented any statistical comparison of controls with these groups. A one-factor analysis of variance (ANOVA) was used to analyze normally distributed measures: body weights, organ weights, organ weight ratios, food and water consumption, haematology and clinical chemistry. When a treatment effect was noted (p <=0.05), the difference between the control and the treatment groups was probed using Tukey's Multiple Comparison Procedure for the 10-day study or by Dunnett's t-test for the 90-day study. For those haematological and clinical chemistry measures which were not normally distributed, a nonparametric rank procedure, the Kruskal-Wallis test, was used to determine differences among the dose groups in the 10-day study. If a significant difference was reached (p <= 0.05), a Wilcoxon Rank Sum method was applied for multiple comparison of treatment groups. When the data was not normally distributed in the 90-day study, data transformations were performed. The data was then analyzed by an ANOVA and controls compared to treated groups by a Dunnett's t-test.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
10-day study

MORTALITY AND CLINICAL SIGNS
10/10 females and 8/10 males died at the highest dose level (300 mg/kg bw/d). There were no deaths in any other treatment group. No treatment-related clinical signs were noted.

FOOD AND WATER CONSUMPTION
Total food and water consumption was not significantly affected in either sex.

BODY AND ORGAN WEIGHTS
Final body weight and weight gain in treated animals were not significantly different from controls in either sex. The relative organ weights for males exposed to 100 mg/kg bw/d had significantly greater liver weights relative to controls. The two low dose groups (10 and 30 mg/kg bw/d) produced no significant differences in relative organ weights.

HAEMATOLOGY
The results of the haematology analyses for exposed female and male rats indicated no parameter significantly different from concurrent control values.

CLINICAL CHEMISTRY
Only a single parameter was significantly different from control values; males at 100 mg/kg bw/d had increased serum cholesterol levels.

GROSS AND HISTOPATHOLOGICAL FINDINGS
The only gross pathological finding consistently noted in the early deaths of high dose animals (300 mg/kg bw/d) was a diffuse reddening of the lungs. Animals in these groups were not histopathologically examined due to protocol limitations. The only microscopic change consistently noted at 100 mg/kg bw/d was inflammation of the mucosal and submucosal layers of the forestomach of minimal severity. A majority (60 %) of both sexes had a similar change. All other changes were considered spontaneous and not treatment related.


90 daystudy

MORTALITY AND CLINICAL SIGNS
There were no compound-related deaths or clinical signs of toxicity at any treatment level.

FOOD AND WATER CONSUMPTION
Average weekly food consumption in all treatment groups was comparable to controls, except males at 150 mg/kg bw/d had a total food consumption that was significantly less than controls.

BODY AND ORGAN WEIGHTS
In females, body weights were comparable in all groups. However, there was a significant decrease in final body weight in males in the 150 mg/kg bw/d group. In females, relative liver and kidney weights were increased at 150 mg/kg bw/d with relative kidney weights also being increased at 75 mg/kg bw/d. In males, adrenal and testes relative weights were significantly increased at 150 mg/kg bw/d while the relative weights of brain, kidneys, and liver were significantly increased at 75 and 150 mg/kg bw/d.

OPHTHALMOSCOPIC EXAMINATIONS
There were no significant ocular changes observed at the terminal ophthalmoscopic examination.

HAEMATOLOGY
In females, RBC's, lymphocytes, haemoglobin, and haematocrit were significantly decreased while platelets, WBCs, neutrophils and monocytes were increased at 150 mg/kg bw/d. Eosinophils were decreased in the 75 mg/kg bw/d group. In males, haemoglobin and haematocrit values were decreased In the 75 and 150 mg/kg bw/d groups while platelets were increased only in the high dose group.

CLINICAL CHEMISTRY
There were a few statistically significant differences in clinical chemistry values. In females, potassium levels were increased and albumin levels decreased in the 75 and 150 mg/kg bw/d groups, while in males, alkaline phosphatase activity was increased in these same two groups.

URINALYSIS
There was no treatment-related alteration in the urinalysis data of either sex.

GROSS AND HISTOPATHOLOGICAL FINDINGS
Few gross lesions were noted at the terminal sacrifice and most had a single incidence. None of the changes present showed a dose-response relationship and none were considered to be of toxicological significance. Few microscopic lesions were observed in the tissues examined. The findings noted were considered spontaneous background changes.

Effect levels

Dose descriptor:
NOAEL
Effect level:
37.5 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: 90-day study, conservative NOAEL

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
A NOAEL of 37.5 mg/kg bw/day was established for the 90-day study
Executive summary:

Male and female Sprague-Dawley rats (10 rats/sex/group) received 1,2 -dichloroethane in corn oil by oral gavage (1 mL/kg bw) for 10 or 90 consecutive days. The doses for the 10-day study were 0, 10, 30,100, or 300 mg/kg bw/d; the 90 -day study doses were 0, 37.5, 75, and 150 mg/kg bw/d. Concurrent control animals were treated with the vehicle, corn oil, only.

In the 10-day study, 10/10 female animals and 8/10 male animals died in the high dose group. No further incidences of mortality were observed. Final body weights and body weight gain along with haematology and clinical chemistry findings were not different from controls. The only relative organ weight which was significantly different was the liver weight in males exposed to 100 mg/kg bw/d. The main histopathological lesion exhibited was multifocal to diffuse inflammation of the mucosal and submucosal layers of the forestomach in the 100 mg/kg bw/d dose group. This change was minimal in both males and females.

In the 90-day study, there were no treatment-related effects pertaining to clinical observations. Body weight gain and total food consumption were significantly decreased in high dose males. There were slight but significant differences in haemoglobin, haematocrit, red blood cell count, platelets, albumin, and alkaline phosphatase values in the 75 and/or 150 mg/kg bw/d groups in one or both sexes as compared to concurrent controls. In males, relative brain, kidney, and liver weights were significantly increased at 75 and 150 mg/kg bw/d. There were also differences in spleen, adrenal, and testes weights (absolute and/or body weight relative). In females, absolute and/or relative kidney and liver weights were significantly increased at 150 mg/kg bw/d (liver) and at 75 and 150 mg/kg bw/d (kidney). There were no apparent treatment-related effects pertaining to mortality, ophthalmology, gross pathology, or histopathology.

Based on these results, a NOAEL of 37.5 mg/kg bw/d was established for male and female Sprague-Dawley rats in the 90-day oral (gavage) toxicity study.