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Administrative data

Description of key information

Effects on target organs: 
- heart muscle toxicity observed at 50 mg/kg bw in rats (DRF study prior to OECD 422)
- mortality observed at 150 mg/kg bw in rats (DRF study prior to OECD 422)

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non guideline dose range finding study, not conducted in accordance with GLP. Raw data available.
Qualifier:
no guideline followed
Guideline:
other: 14d-Dose Range Finding Study
Principles of method if other than guideline:
The main objective of the study is to assess whether rats tolerate the test substance at offered concentration by gavage in order to select dose levels in an adequate form of administration for subsequent studies.
GLP compliance:
no
Limit test:
no
Species:
rat
Strain:
other: Crl:WI(Han)
Sex:
male/female
Route of administration:
oral: gavage
Vehicle:
corn oil
Duration of treatment / exposure:
two weeks
Frequency of treatment:
once daily
Remarks:
Doses / Concentrations:
0, 50, and 150 mg/kg bw
Basis:
nominal in water
No. of animals per sex per dose:
four
Control animals:
yes
Observations and examinations performed and frequency:
Mortality
A check for moribund and dead animals will be made twice daily from Monday to Friday and once daily on Saturday, Sunday and public holidays.

Clinical signs
Animals will be checked daily for any abnormal clinical signs before the administration, as well as, within 2 hours and within 5 hours after the administ

Food consumption
Food consumption will be determined on study day 3, 7, 10 and 14 and calculated as mean food consumption in gram per animal and day.

Drinking water consumption
Drinking water consumption will be determined on study day 3, 7, 10 and 14 and calculated as mean water consumption in gram per animal and day.

Body weight
Body weight will be determined before the start of the administration period in order to randomize the animals. During the administration period the body weight will be determined on day 0, 3, 7, 10 and 14. The difference between the body weight on the respective day of weighing and the body
weight on day O will be calculated as body weight change.

CLINICAL PATHOLOGY
Blood samples will be taken from fasted animals by puncturing the retrobulbar venous plexus under isoflurane anesthesia. Blood sampling and examination will be carried out in a randomized sequence.
Sacrifice and pathology:
Necropsy
All animals will be sacrificed by decapitation under isoflurane anesthesia. The exsanguinated animals will be necropsied and assessed by gross pathology, special attention being given to the reproductive organs. Animals which die intercurrently or are sacrificed in a moribund state will be necropsied as soon as possible after their death and assessed by gross pathology

Organ weights
The following weights will be determined in all animals sacrificed on schedule:
1. Anesthetized animals
2. Adrenal glands
3. Heart
4. Kidneys
5. Liver
6. Spleen

Organ/Tissue fixation
The following organs or tissues will be fixed in 4% buffered formaldehyde solution:
1. All gross lesions
2. Adrenal glands
3. Heart
4. Kidneys
5. Liver
6. Spleen
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):
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Dose descriptor:
LOAEL
Effect level:
50 mg/kg bw/day (nominal)
Sex:
male/female
Critical effects observed:
not specified

50 mg/kg bw

findings:

salivation in 3/4 males and females

piloerection in 4/4 males and females

food consumption

decreased over entire study period in all males and in females from study days 3 to 14

water consumption

NAD

body weight

decreased in males on study days 7, 10 and 14 as well as in females on study days 7 and 14

body weight change

decreased in males and females over the entire study period

organ weights

absolute terminal body weights: decrease in males and females

adrenal glands and heart: relative weight increased in males

kidneys: relative weight increase in males and females

liver: relative weight increase in males and females

gross lesions

NAD

microscopic lesions

necrosis/fibrosis of the myocard of the heart in 2/4 male and 214 female animals mostly in the septal area

150 mg/kg bw

findings

premature death in 1/4 males on study day 6

poor general condition in 3/4 males and 4/4 females

salivation 2/4 males and 3/4 females

limbs paresis 1/4 males and 2/4 females

ataxia in 1/4 males and 2/4 females

unsteady gait in 1/4 males

all animals were sacrificed in moribund state on study day 6

food consumption

decreased in males and females from study days 0 to 3

water consumption

NAD

body weight

decreased in males on study day 3

body weight change

decreased in males from study day 0 to 3

gross lesions

forestomach erosion/ulcer in 4/4 males and females

grandular stomach erosion/ulcer in 1 /4 males

enlarged liver 4/4 males and females

discoloration of spleen 4/4 males and females

microscopic lesions

necrosis/fibrosis of the myocard of the heart in all male and female animals mostly in the septal area

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
50 mg/kg bw/day
Study duration:
subacute
Species:
rat

Additional information

The repeated dose toxicity of TMDC was investigated in a dose range finding (DRF) study. TMDC induced target organ toxicity and should be classified as harmful after prolonged exposure (STOT RE cat. 2 and R48/22, respectively).

Four males and four females per dose groups were treated at dose levels of 50 and 150 mg/kg bw. At 50 mg/kg bw clear toxic effects including necrosis/fibrosis of the myocard of the heart mostly in the septal area of the animals was observed, which could be linked to the administration of TMDC.

The reported study clearly demonstrates that TMDC induces specific target organ toxicity.

The reported study is to be used as bridging study to justify the weight of evidence approach for the hazard assessment of TMDC. Since other dicycans as PACM (CAS 1761-71-3) or DMDC (CAS 6864-37-5) were found to cause specific target organ toxicity, the same was expected for TMDC. The obtained study result confirms TMDC as a target organ toxic agent, thereby supporting the proposed weight of evidence approach.

Further, the study itself qualifies to be used as key study for regulatory purposes (classification and labelling). The reduced number of animals used in this study or the non-GLP status is of less relevance, because the same results can be expected for a regular OECD 422 study. The obtained study result is sufficient to classify TMDC as harmful after repeated exposure with the target organs liver, kidney, skeletal and heart muscle (see also dossiers of PACM, CAS 1761-71-3 and DMDC, CAS 6864-37-5).


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The data on TMDC is limited to one dose range finding study for OECD 422, in which four animals were used per sex and dose group. Clear toxicity on target organs could be identified. No further animal testing is necessary.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: heart

Justification for classification or non-classification

Based on these results TMDC should be classified with STOT RE, category 2 according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

According to Directive 67/548/EEC this corresponds to a classification as harmful: danger of serious damage to health by prolonged exposure if swallowed (Xn, R48/22).