1,2-dichloroethane

Repeated dose toxicity: oral

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:

comparable to guideline study with acceptable restrictions

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

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

not specified

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,2-dichloroethane

EC Number:

203-458-1

EC Name:

1,2-dichloroethane

Cas Number:

107-06-2

Molecular formula:

C2H4Cl2

IUPAC Name:

1,2-dichloroethane

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 or test system 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 / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
10-day study: 0, 10, 30, 100, and 300 mg/kg bw/d
Basis:
actual ingested

Doses / concentrations 2

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.