Registration Dossier

Administrative data

Description of key information

The toxicity of 1,2-dichloroethane was investigated in several oral studies in rats and mice for 90 days (Daniel et al., 1994), 2 years (Alumot et al., 1976) and 13 weeks (Morgan et al., 1990; NTP, 1991; Munson et al., 1982) and inhalation studies in rats and mice (Heppel et al., 1946; Spencer et al., 1951; Hofmann et al., 1971; Maltoni et al., 1980/Spreafico et al., 1980) and in guinea pigs, rabbits, cats, dogs, and monkeys (Heppel et al., 1946; Spencer et al., 1951), resulting in overall NOAELs or NOAECs of 37.5 mg/kg bw/d for the oral route and 41.1 mg/m³ for the inhalation route.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
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
Reason / purpose:
reference to other study
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
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.
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
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
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.
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.
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
Critical effects observed:
not specified
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.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
37.5 mg/kg bw/day

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records
Reference
Endpoint:
chronic toxicity: inhalation
Remarks:
combined repeated dose and carcinogenicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: According to OECD guideline and GLP
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
no
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Fischer 344/DuCrj
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan, Inc., Kanagawa, Japan
- Age at study initiation: 6 weeks old
- Weight at study initiation: 120 ± 5 g
- Housing: Individually in stainless steel wire hanging cages (150 mm x 220 mm x 176 mm)
- Diet: Commercial pellet diet (CRF-1, Oriental Yeast Co., Ltd., Tokyo, Japan), ad libitum
- Water: Sterilised water, ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 23 ± 2 degree C
- Humidity: 55 ± 10 %
- Air changes: 12 ± 1 air changes/hour
- Photoperiod: 12 hours dark / 12 hours light
Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: no data
Details on inhalation exposure:
Airflow containing 1,2-dichloroethane vapor at a target concentration for rats of 10, 40 or 160 ppm was prepared by a vaporization technique. The saturated vapor-air mixture was generated by bubbling clean air through liquid 1,2-dichloroethane in a temperature-regulated glass flask (25 degree C), and by cooling it through a thermostatted condenser at 18 degree C. The airflow containing the saturated vapor was diluted with clean air, and then warmed to 25 degree C in a thermostatted circulator which served to stabilize the vapor concentration by complete gasification of 1,2-dichloroethane. The flow rate of vapor-air mixture was regulated with a flow meter, further diluted with humidity- and temperature-controlled clean air in a spiraling line mixer, and then supplied to the inhalation exposure chambers. Four inhalation exposure chambers of 7600 L in volume were used in this study. Each exposure chamber accommodated 100 individual cages for 50 males and 50 females.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Chamber concentrations of 1,2-dichloroethane were monitored by gas chromatography every 15 min, and maintained constant at 10.0 ± 0.1, 39.8 ± 0.6 and 159.7 ± 2.1 ppm for the exposure of rats throughout the 2-year exposure period.
Duration of treatment / exposure:
104 weeks, 6 hours per day
Frequency of treatment:
5 days per week
Remarks:
Doses / Concentrations:
0, 10, 40, or 160 ppm (0, 41.1, 164.5 or 658.1 mg/m³)
Basis:
nominal conc.
No. of animals per sex per dose:
50 animals
Control animals:
yes, concurrent no treatment
Details on study design:
Groups of 50 male and 50 female rats were exposed to airflow containing 1,2-dichloroethane vapor at a target concentration of 10, 40, or 160 ppm for rats for 6 h/d, 5 d/wk and for 104 wk (2 years). Fifty rats of both sexes, serving as concurrent controls, were handled in the same manner as the 1,2-dichloroethane-exposed groups, but were exposed to clean air in the inhalation exposure chambers. The lowest exposure concentration of 10 ppm was selected in consideration of the OEL of 10 ppm for 1,2-dichloroethane. Selection of the highest concentrations of 160 ppm for rats was based on both subchronic toxicity and body weight decrement from a preliminary 13-weeks inhalation exposure study conducted at the JBRC. All rats died during the first week of 13-weeks exposure to 320 ppm, but 13-weeks exposure to 160 ppm did not cause any deaths, overt toxic signs or body weight decrements. Therefore, the highest exposure concentration of 160 ppm was predicted not to exceed the MTD from the results of the 13-weeks inhalation exposure study.
Positive control:
none
Observations and examinations performed and frequency:
The animals were observed daily for clinical signs and mortality. Body weights and food consumption were measured once a week for the first 14 wk, and every 4 wk thereafter.
Sacrifice and pathology:
All the rats which died or were killed in a moribund state during the 2-year exposure period, or survived to the end of the 2-year period received complete necropsy. Urinary parameters were measured from urine sampled with Ames Reagent Strips in the last week of the 2-year exposure period. For haematology and blood biochemistry, the surviving animals were bled under ether anaesthesia at terminal necropsy after they were fasted overnight. The blood samples were analyzed on an automatic blood cell analyzer for haematology, and an automatic analyzer Hitachi 705 and a flame analyzer Hitachi 750 for blood biochemistry. Organs were removed, weighed, and examined for macroscopic lesions at the necropsy. Tissues for microscopic examinations were fixed in 10 % neutral buffered formalin and embedded in paraffin. Tissue sections 5 µm thick were prepared and stained with haematoxylin and eosin.
Other examinations:
none
Statistics:
Incidences of neoplastic lesions were analyzed for a dose response relationship indicated by a significant positive trend by Peto’s test, and for a significant difference from the concurrent control group by Fisher’s exact test. Incidences of non-neoplastic lesions and urinary parameters were analyzed by Chi-square test. Survival curves were plotted according to the Kaplan- Meier method, and the log-rank test was used to test statistical significance of the difference between any 1,2-dichloroethane-exposed rat group of either sex and the respective control. Body weight, organ weight, haematological and blood biochemical parameters were analyzed by Dunnett’s test. When tumor incidences were increased in a dose-related manner as indicated by Peto’s test and when the tumor incidence in each of the exposed groups was increased but not statistically significant as compared with the concurrent, matched-control group by Fisher’s exact test, the borderline increase in the tumor incidence was tested as to whether or not it was biologically meaningful, using a range of minimum and maximum tumor incidences in the JBRC historical control data.
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):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
MORTALITY, BODY WEIGHT, FOOD CONSUMPTION AND CLINICAL OBSERVATIONS:
There was no significant difference in the survival rate at any time point of the 2- year exposure period between any exposed group of either sex and the respective control. At the end of the 2-year exposure period, the survival rates of the 0 (clean air as control), 10, 40 and 160 ppm exposure groups were 74, 70, 64 and 74 % for males, and 70, 82, 74 and 76 % for females, respectively. Neither growth rate nor food consumption was suppressed in any exposed group of either sex as compared with the respective control. The body weights of the 0, 10, 40 and 160 ppm exposure groups at the end of 2-year exposure period were 434 ± 46, 459 ± 59, 448 ± 41 and 467 ± 85 g for males, and 317 ± 46, 329 ± 41, 33 ± 45 and 336 ± 56 g for females, respectively. Incidences of subcutaneous masses, which were found in the breast, back, and abdominal and perigenital areas by clinical observation, tended to increase in the exposed groups of both sexes. No exposure-related change in any haematological, blood biochemical or urinary parameter was found in any exposed group of either sex.

HISTOPATHOLOGY:
For carcinogenicity please refer to IUCLID5 chapter 7.7
No exposure-related, non-neoplastic lesions were observed in any exposed group of either sex.
Dose descriptor:
NOAEL
Effect level:
658.1 mg/m³ air (nominal)
Sex:
male/female
Basis for effect level:
other: no adverse effects observed except of carcinogenicity
Critical effects observed:
not specified
Conclusions:
1,2-dichloroethane was shown to be carcinogenic after inhalation exposure to rats for a period of 2 years.
Executive summary:

Carcinogenicity and chronic toxicity of 1,2- dichloroethane were examined by inhalation exposure of groups of 50 F344/sex/dose to 1,2- dichloroethane vapor or clean air as control for 6 h/d, 5 d/wk and 104 wk. The rats were exposed to 0, 10, 40 or 160 ppm (v/v) ( equivalent to 0, 41.1, 164.5 or 658.1 mg/m³) 1,2- dichloroethane. The 2-year exposure produced a dose-dependent increase in incidences of benign and malignant tumors, including subcutaneous fibroma, mammary gland fibroadenoma and peritoneal mesothelioma in male rats; subcutaneous fibroma and mammary gland adenoma, fibroadenoma and adenocarcinoma in female rats. No exposure-related change in the incidence of non-neoplastic lesions or in any haematological, blood biochemical or urinary parameter occurred in any exposed rat group. The types of tumors and their target organs found in this study were consistent with those observed in rats and mice administered 1,2 - dichloroethane by gavage in a NCI study. Selection of the exposure concentrations was considered appropriate with reference to the maximum tolerated dose for the highest doses and an occupational exposure limit of 1,2- dichloroethane for the lowest dose.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
41.1 mg/m³

Additional information

Oral route

In the key study by Daniel et al. (1994), male and female Sprague-Dawley rats received 1,2-dichloroethane in corn oil by gavage for 10 or 90 consecutive days. The doses for the 10-day study were 0, 10, 30, 100, and 300 mg/kg bw/d; the 90 -day study doses were 0, 37.5, 75, and 150 mg/kg bw/d. There were ten animals per sex per dose group. Concurrent controls were treated with the vehicle, corn oil, only.

In the 10-day study, all female animals died in the high dose group and only 2/10 males survived. Final body weights and 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 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 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. 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 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. Thus, a NOAEL of 37.5 mg/kg bw/d was established for the 90-day study.

In a comprehensive standard 13-week drinking water study comprising three strains of rats (Fischer 344, Osborne-Mendel and Sprague-Dawley rats) and concentrations of 500 to up to 8000 mg/L, corresponding to doses of about 50 and 730 mg/kg bw/d, respectively, no substance related mortalities, no clinical signs of toxicity and no abnormalities of blood-chemical parameters, were evident in all five dose groups of either sex. Minimal histological lesions appeared only in female F344 rats as a dose dependent increase in renal tubular regeneration. Increases in the absolute and relative weights of kidneys and livers were observable throughout (p<0.05 or <0.01). Body weight gain and water consumption were reduced in a dose-related manner, the latter by 50 - >60 % at maximum in all strains (Morgan et al. 1990; NTP 1991). The test substance caused minimal toxicity in all three rat strains. The NOAEL was determined by the selected top concentration of 8000 mg/L corresponding to doses of about >= 500 mg/kg bw/d.

In a 13-week gavage study conducted in F344 rats, equivalent 1,2-dichloroethane doses between 18 and 480 mg/kg bw/d (5d/wk) produced substantially higher toxicity than in the drinking-water study, demonstrated by pronounced clinical signs of intoxication (tremor, hypersalivation, ruffled fur and dyspnoea) and high mortality (90 -100 % at the higher dose levels). No substance-related abnormalities of blood-chemical parameters, and histopathological organ changes were detectable, including renal tubular regeneration, except minimal to mild hyperplasia and inflammation of the mucosa of the forestomach in the second highest dose group of males (p<0.05) and necrosis of the thymus and cerebellum in the second highest dose group of males and in the highest dose group of females (p<0.05). Increases in the absolute and relative kidney and liver weights were observed in all dose groups to a different extent (Morgan et al., 1990; NTP 1991). The NOAEL was assumed to be 120 and 150 mg/kg bw/d for male and female F344 rats, respectively, based on treatment-related effects in the forestomach and clinical symptoms. A LOEL was at 18 -30 mg/kg bw/d, the lowest dose tested, based on significant increases in liver and kidney weight in females and males, respectively, which was considered as biologically relevant, but not pathological.

1,2-dichloroethane given to male and female B6C3F1 mice for 13 weeks via the drinking water at doses of up to 8000 mg/L, corresponding to about 4200–4900 mg/kg bw/d, caused minimal to moderate organ toxicity, only observed in the kidneys of male animals and characterised by hyaline urinary cylinders, dilatation of the tubules and focal mineralisation in the renal papilla of all dose groups. In the highest dose group of females, 9/10 animals died (NTP 1991). A NOAEL for males was established based on renal tubular regeneration: 0/10 (contr.), 1/10 (500 mg/L), 2/10 (1000 mg/L), 2/10 (2000 mg/L), 8/10 (4000 mg/L), and 9/10 (8000 mg/L). For females, the NOAEL was about 2500 mg/kg bw/d, based on mortality. The test substance caused minimal toxicity. A NOAEL of 2000 ppm was established by the authors, corresponding to about 780 mg/kg bw/d for male mice. The LOEL of about 240 -250 mg/kg bw/d was based on absolute and relative increases in kidney weights already evident in 500-mg/L groups and considered as substance-related, but not yet pathological.

Another 13-week drinking-water study on male and female CD1-mice, which mainly focused on immunotoxic aspects and comprised other parameters not generally covered in a standard study, gave equivocal evidence of adverse effects on both humoral and cell-mediated immunity at concentrations of 20, 200, and 2000 mg/L (Munson et al., 1982): There was a dose-dependent declining trend in haemagglutination titer which was not statistically significant (p<0.05). The NOAEL referring to immune responsiveness was the highest dose tested, correspondingly about 190 mg/kg bw/d, while the NOEL was assumed to be 24 mg/kg bw/d, based on the absence of depression of body weight gain.

In a non-standard oral study, which included mating intervals of treated females with untreated males, average doses of 12.5 and 25 mg /kg bw/d were administered with especially fumigated and preserved feed (250 and 500 ppm, respectively) to male and female locally bred rats for two years. No impairment of feed consumption and body weight development was observed. By 14 months, all animals including controls began to suffer from chronic respiratory disease causing mortality rates to increase. Examination of liver weights, hepatic fat content and various serum parameters did not support any effect on liver and kidney function (Alumot et al., 1976).

According to the results of this study, the NOAEL was defined to be greater than 25 mg/kg bw/d. In the previous range-finding study, no effects but slight increases in hepatic total fat and in triglycerides (p<0.05) were found after feeding of about 80 mg/kg bw/d for 7 weeks (Alumot et al., 1976). Due to relevant deficiencies and based on the availability of more relevant gavage studies, this study was not taken into account for risk assessment.

Inhalation route

Carcinogenicity and chronic toxicity of 1,2-dichloroethane were examined by inhalation exposure of groups of 50 F344 rats and 50 BDF1 mice of both sexes to 1,2-dichloroethane vapor or clean air as control for 6 h/d, 5 d/wk and 104 wk (Nagano, 2006). The rats were exposed to 0, 10, 40 or 160 ppm (0, 41.1, 164.5 or 658.1 mg/m³), while the mice were exposed to 0, 10, 30 or 90 ppm (0, 41.1, 123.4 or 370.2 mg/m³). The 2-year exposure produced a dose-dependent increase in incidences of benign and malignant tumors, including subcutaneous fibroma, mammary gland fibroadenoma and peritoneal mesothelioma in male rats; subcutaneous fibroma and mammary gland adenoma, fibroadenoma and adenocarcinoma in female rats; and bronchiolo-alveolar adenoma and carcinoma, endometrial stromal polyp, mammary gland adenocarcinoma and hepatocellular adenoma in female mice. No exposure-related change in the incidence of non-neoplastic lesions or in any haematological, blood biochemical or urinary parameter occurred in any 1,2-dichloroethane-exposed rat or mouse group. The types of tumors and their target organs found in this study were consistent with those observed in rats and mice administered 1,2 -dichloroethane by gavage in a NCI study. Selection of the exposure concentrations was considered appropriate with reference to the maximum tolerated dose for the highest doses and an occupational exposure limit of 1,2-dichloroethane for the lowest dose (see also carcinogenicity section). A NOAEL of 41.1 mg/m³ was established based on mortality in female mice.

Several other early subchronic to chronic inhalation studies realised largely consistent results after exposure to concentration levels ranging from 100-400 ppm (approx. 400 and 1600 mg/m³, respectively) for about 15 weeks, 7h/day, and 5d/wk (Heppel et al., 1946), for 17 weeks, 6h/day, and 5day/wk (Hofmann et al., 1970), and for more than 40 weeks, 7h/day, and 5day/wk (Spencer et al., 1951). The studies partly including several rat strains of either sex (Wistar, SD, Osborne-Mendel)

comprised clinical, blood-chemical and microscopic/histopathological examinations, the latter mostly limited to main organs.

In line with these previous observations were those made in the comprehensive 18-months inhalation study by Maltoni et al. (1980)/Spreafico et al. (1980) on SD rats exposed to concentrations of 0, 5, 10, 50, or 150 (250) ppm [see also Carcinogenicity]. Further support was provided by another, special 2-year study including exposure of male and female SD rats to 50 ppm of neat 1,2-dichloroethane, 7 h/day, 5 days/wk (Cheever et al., 1990).

The toxicity profile of 1,2-dichloroethane elaborated in rats was further supplemented by more or less well founded, but on the whole reliable findings in other species including rabbits and guinea pigs (Heppel et al., 1946; Spencer et al., 1951; Hofmann et al., 1970), dogs (Heppel et al., 1946), and monkeys (Heppel et al., 1946; Spencer et al., 1951). Yet, other limited screening studies performed on cats (Heppel et al., 1946; Hofmann et al., 1970) and mice (Heppel et al., 1946) were available, but were dismissed here, because they appeared not to add new information to that known from the other results. All these investigations covered similar concentration ranges and exposure periods like those employed in the rat studies.

Marked signs of toxicity eventually associated with substantial reduction in survival were evident at a level of 200 ppm in rats (Heppel et al., 1946), guinea pigs, and monkeys (Heppel et al., 1946; Spencer et al., 1951), but not in rabbits and dogs (Heppel et al., 1946; Spencer et al., 1951). Contrary to Heppel et al. (1946), Spencer et al. (1951) reported less pronounced or no significant adverse effects in guinea pigs and rats, respectively, after prolonged exposure to 200 ppm, while this exposure level was missing in the work of Hofmann et al. (1970). In the study by Heppel et al. (1946), about 100 ppm produced no signs of toxicity in rats (strain not specified) receiving 74 exposures (about 15 weeks; 7 h/d, 5 d/wk), whereas already 200 ppm caused significant toxicity associated with early mortality in Osborne-Mendel and Wistar rats (<6 and < 27 days, respectively).

In principal, the toxicity profile was similar to that found after oral ingestion, including hepatic fatty degeneration and proliferative changes in the renal tubular epithelia, but, more often than not, involving lung damage, too, such as congestion and haemorrhage. The occurrence of deaths at toxic levels was very variable, either already within the time of 4 -9 exposures or also not until 27-44 or even beyond 70 exposures within the same treated group. The unequivocal cause of mortality was never clear, and deaths often came about quite unexpected and abruptly: post-mortem, they could not be related to the generally low degree of the organ lesions discovered. It was assumed that ultimately respiratory arrest and/or cardiovascular failure led to death.

In the long-term study by Maltoni et al. (1980), the top-exposure level had to be lowered after a few weeks due to overt signs of intoxication, which underlined that the critical atmospheric 1,2-dichloroethane exposure level was probably in the range of 200 ppm (approx. 800 mg/m³).

Conclusions from repeated studies by the oral and inhalation route

In conclusion, from the majority of investigations, the NOAEC of 41.1 mg/m³ after prolonged inhalation exposure was derived from the combined repeated dose/carinogenicity study by Nagano (2006). From the key study, the NOAEL of 37.5 mg/kg bw/d was established for the oral route (Daniel et al., 1994), based on slight but significant differences in haemoglobin, haematocrit, red blood cell count, platelets, albumin, and alkaline phosphatase values at higher dose levels. This value is estimated as very conservative since the effects are very slight, since the apparent NOAEL in the 2-year feeding study (Alumot et al., 1976) was defined by the top dose of 25 mg/kg bw/d (no treatment related effects occured) and since the value of 120 mg/kg bw/d from the 13 -weeks study (NTP) was usually considered as a NOAEL in various risk assessments.

Justification for classification or non-classification

The substance 1,2-dichloroethane is not classified regarding repeated dose toxicity according to the harmonised classification in Regulation 1272/2008 of the European Parliament and the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation 1907/2006.