3-methylthiazolidine-2-thione

Endpoint summary

Description of key information

Repeated dose toxicity: subchronic (90 day) study oral (feed), rat (Wistar) m/f (similar to OECD 408):

NOAEL = 100 ppm corresponding to 7.91 mg/kg bw/d (males) and 9.78 mg/kg bw/d (females) (based on food consumption, body weight)

LOAEL = 500 ppm corresponding to 42.70 mg/kg bw/d (males) and 49.54 mg/kg bw/d (females) (based on food consumption, body weight)

LOAEL = 2500 ppm corresponding to 202.54 mg/kg bw/d (males) and 228.87 mg/kg bw/d (females) (based on mortality; clinical chemistry; urinalysis)

No specific target organ toxicity was identified, no classification as STOT RE Cat. 2 was triggered.

 

Repeated dose toxicity: subacute (6, 12, and 23 day) study oral (gavage), 50 mg/d, rat (Wistar), male:

NOEL ≥ 50 mg/kg/d (male, based on relative / absolute thyroid gland weight)

LOEL = 50 mg/kg/d (male, based on body weight)

 

Repeated dose toxicity: subacute (5 x 4hour exposure) study inhalation (vapour), 2108 resp. 2613 mg/m³, mice, rats, hamsters, and rabbits: NOECs ≥ 2108 mg/m³ air (mice, rats) resp. ≥ 2613 mg/m³ (hamsters, rabbits)

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted prior to GLP similar to OECD guideline 408 on the registered substance itself. The method is to be considered scientifically reasonable with minor deficiencies in documentation and performance, e.g. dosing intervals were chosen as 5-fold instead of 2-4-fold. Also, the original report is in German, which does however not affect the assessment of the study as the assessor is a native speaker.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

not applicable

GLP compliance:

no

Remarks:

test conducted prior to GLP implementation

Limit test:

no

Species:

rat

Strain:

other: SPF, Wistar-TNO W.74

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Züchter Winkelmann, Borchem
- Age at study initiation: 35-42 days
- Weight at study initiation: 50-60 g
- Housing: single in Makrolon cages Type II with dust-free wood granules
- Diet (e.g. ad libitum): Altromin R-powder feed (Altromin, Lage) ad libitum
- Water (e.g. ad libitum): tap water ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 ± 2°C

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Mixing appropriate amounts with (Type of food): Altromin R-powder feed (Altromin, Lage)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

3 months

Frequency of treatment:

continuously

Remarks:

Doses / Concentrations:
100, 500, 2500 ppm
Basis:
nominal in diet

No. of animals per sex per dose:

15

Control animals:

yes, plain diet

Positive control:

none used

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: after 1 and 3 months in 5 animals/sex/dose

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- 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: No data

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: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after 1 and 3 months
- Anaesthetic used for blood collection: Yes (diethylether)
- Animals fasted: No data
- How many animals: 5 animals/sex/dose
- Parameters erythrocyte and leukocyte count, thrombocyte count, hemoglobin, hematocrit, differential blood count, MCH, MCV, and thromboplastin time were examined.

CLINICAL CHEMISTRY: Yes / No / No data
- Time schedule for collection of blood: after 1 and 3 months
- Animals fasted: No data
- How many animals: 5 animals/sex/dose
- The following parameters were examined:
- Enzymes: Alkaline Phosphatase (ALP), Glutamate-Oxalacetate-Transaminase (GOT), Glutamate-Pyruvate-Transaminase (GPT), Glutamate-Dehydrogenase (GlDH)
- Substrates: Creatinine, urea, glucose, cholesterol, bilirubin, and total plasma protein

URINALYSIS: Yes
- Time schedule for collection of urine: 16h collection period after oral gavage of ca. 8 ml water
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- The following parameters were examined:
- semiquantitatively: glucose, blood, protein, pH value, ketobodies, bilirubin, urobilinogen, and microscopic sediment examination after centrifugation of urine
- quantitatively: protein according to Richterich (1968)

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER:
Thyroid function:
- Protein-bound iodine (PBI)
- Rectal determination of body temperature

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- Necropsy of rats which died during experimental phase:
Rats were necropsied and examined macroskopically. All dissected organs and possible changes were fixed in Bouins fixans and after ca. 30 h in 70% ethanol.
- Necropsy of rats which were sacrificed at the end of the experimental phase:
All surviving animals were anesthized with diethylether and killed via exsanguination. After necropsy animals were examined macroscopically. The weights of thyroid, thymus, heart, lung, liver, spleen, kidneys, adrenal glands, testicles resp. ovaries were determined.
Of each five male and female animals heart, lung, liver, spleen, kidneys, pituitary gland, thyroid, adrenal glands, testicles, epididymis, prostate, seminal vesicle, ovaries, uterus, salivary glands, pancreas, esophagus, stomach, intestines, lymph nodes, thymus, bladder, brain, eyes, aorta, trachea, skeletal muscles incl. nervus ischiadicus, bones and bone marrow were fixed in Bouins fixans and after 30h in 70% ethanol, parts of the liver of these animals were fixed in Formol-Ca.
The organs to bei weighted as well as brain, pituitary gland and testicles resp. ovaries were fixed in 10% buffered formaldehyde solution.

HISTOPATHOLOGY: Yes
5 µm paraplast section were prepared from the fixed organs resp. organ samples and stained with hemalaun-eosin. Additional sections of the kidneys were stained via PAS reaction. 15 µm frozen sections of formol-fixed liver were stained with Oil Red O for fat determiantion. Bones were decalcified with sodium EDTA. Histological examinations were made on each five male and female animals of the control and high dose group.

Statistics:

Arithmetic means, standard deviations, upper and lower confidence limits with the confidence niveau of 1-α = 95% and 1-α = 99%. Values of the test and control groups were compared with the test for significance (U-Test) according to Mann, Whitney and Wilcoxon on the significance niveau α = 5% and α = 1% using the computer IBM-370/145. Establishing the random list was done using "Subprogram Randu" of the "Scientific Subroutine Package" by IBM on the computer IBM-370.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Appearance and behaviour were not influenced in male and female rats at dosages up to 2500 ppm. 2 males of the high dose group died during the course of the study.

Mortality:

mortality observed, treatment-related

Description (incidence):

Appearance and behaviour were not influenced in male and female rats at dosages up to 2500 ppm. 2 males of the high dose group died during the course of the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Growth was not influenced in the 100 ppm group. In the 500 and 2500 ppm group food consumption and body weight gain were diminished significantly (p<0.01) during the whole study duration.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Food consumption was not influenced in the 100 ppm group. In the 500 and 2500 ppm group food consumption and body weight gain were diminished significantly (p<0.01) during the whole study duration. A repellent effect of the test item cannot be excluded.

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Blood was not damaged by the test item in the groups up to 500 ppm. An intermittent influence on the leucocytes was noticed after one month in the 2500 ppm group, which could not be observed after 3 months.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

There were no treatment-related adverse effects to the liver or kidneys in dosages up to 500 ppm. An intermittent increase of the enzymes GOT and GPT, a decrease in plasma protein and persistent elevated urea concentration was noted in the 2500 ppm group.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

There was no indication on kidney damages in the dosage groups up to 500 ppm. At the 2500 ppm group elevated urea concentrations were noted.

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Necropsies and histopathological examinations gave no indications on treatment-related effects on any organs in groups up to 2500 ppm.

Gross pathological findings:

no effects observed

Description (incidence and severity):

Necropsies and histopathological examinations gave no indications on treatment-related effects on any organs in groups up to 2500 ppm.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Necropsies and histopathological examinations gave no indications on treatment-related effects on any organs in groups up to 2500 ppm.

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
No differences between control and dosage groups were observed regarding appearance and behaviour. During the course of the study two males of the 2500 ppm group died.


BODY WEIGHT AND WEIGHT GAIN
Male and female rats gained weight similarly to the ones from the control. The 500 ppm and 2500 ppm animals showed during the whole study a significantly (p<0.01) decreased body weight gain.


FOOD CONSUMPTION AND COMPOUND INTAKE
Details on food consumption and compound intake can be found in table 1, “any other information on results incl. tables”. Male and female rats consumed powder feed similarly to the ones from the control. The 500 ppm and 2500 ppm animals consumed approx. 10% resp. 45% less feed than control animals.


HAEMATOLOGY
Table 2a (“any other information on results incl. tables”) shows the results (mean values) of the blood analysis, table 2b the differential blood count after 1 and 3 months of treatment.
After 1 month, all treated females and the 100 ppm males did not differ relevantly from the control animals regarding erythrocyte and leukocyte count, thrombocyte count, hemoglobin, and haematocrit, as well as MCH and MCV. The males exhibited a significantly decreased thrombocyte (500 and 2500 ppm) and leucocyte count (2500 ppm). The 100 ppm animals did not differ from control regarding differential blood count and shape of the single cell types. In the 2500 ppm animals, the amount of neutrophile granulocytes with segmented nucleus was significantly elevated, in the females of the 500 ppm group and the 2500 ppm animals the leucocyte count was significantly decreased.
After 3 months, no significant differences were observed between all treated animals and control regarding blood analysis and differential blood count.


LIVER FUNCTION
Table 3 (“any other information on results incl. tables”) shows the results of the liver function related enzymes and total plasma protein. The values of the control and the 100 ppm group do not differ significantly. After 1 month, the 2500 ppm animals showed increased values of the transaminases GOT and GPT, significantly increased was only the GOT value of the males. Additionally, significantly decreased protein plasma levels were detected in the 500 ppm and 2500 ppm groups as well as increased ALP activities in the 2500 ppm males.
After 3 months, there were no treatment-related differences regarding ALP, GOT, GPT, GLDH and Bilirubin up to 2500 ppm. Total plasma protein was decreased in the 2500 ppm females.


KIDNEY FUNCTION
Results of the urine examinations after 1 and 3 months revealed no significant differences compared to control. In none of the examined rats glucose, keto bodies or bilirubin was found in the urine. Only in male rats after 3 months there were found protein- and blood-positive results, which are however dose-independent. The content of urobilinogen and pH value of the treated animals did not differ to a relevant extent from control, examination of sediment did not show a treatment-related influence.
The mean urea- and creatinine-concentrations as well as protein content in urine can be found in Table 4 (“any other information on results incl. tables”). Urea and creatinine-concentrations were in physiological range for animals dosed up to 500 ppm after one month and in all group after 3 months. Elevated urea was detected in the 2500 ppm group (only significant in males) after 1 month. Protein content in the urine was not elevated in any of the treated groups.


CLINICAL CHEMISTRY – OTHER
Blood sugar and cholesterol were determined not to be in pathological range in dosage groups up to 2500 ppm. Table 5 (“any other information on results incl. tables”) shows these results. All (significantly) deviating values in males and females are dose-independent, all values are within the normal range for animals of this age and hence not toxicologically relevant.


THYROID FUNCTION
The results of the determination of protein-bound iodine (PBI) after 4 and 9 weeks as well as 3 months can be found in Table 6 (“any other information on results incl. tables”). Decreased PBI values were determined only in males and females after one month and males after 3 months in the 2500 ppm group. , which were only significant in males. Additionally, after 9 weeks in males of the 100 ppm group an increased PBI value was found.
Body temperatures (also Table 6) were significantly decreased after one month in males and females in the 2500 ppm group. No deviations from control were found after 3 months. After one month in males and females of the 100 and 500 ppm and after 3 months in the 100 ppm males slightly elevated body temperatures were measured.


GROSS PATHOLOGY
Necropsy of rats which died during study:
Both perished males were necropsied. In one rat there were no distinct findings, the other rat showed bleedings in stomach and mucosa in the fundus and elevated content of air and liquids in the lung.

Necropsy of rats killed at the end of the study:
Necropsies of all animals gave no indications of a specific damage in all dosage groups.


ORGAN WEIGHTS
Tables 7a and 7b (“any other information on results incl. tables”) show the absolute and relative organ weights of thyroid, thymus, heart, lung, spleen, kidneys, adrenal glands and testicles resp. ovaries.
Organ weights of the 100 ppm males and females did not differ significantly from control. Deviations from control in the 500 and 2500 ppm groups compared to control were commonly decreased. Relative organ weights however were in the 2500 ppm group significantly increased, except thymus (males) and spleen, adrenal glands and ovaries (females). Furthermore, in the 500 ppm group the weights of thymus, heart, liver, spleen and kidneys were decreased, the ones of the testicles were increased.


HISTOPATHOLOGY: NON-NEOPLASTIC
Incidental finding in individual animals of various groups were: unspecific chronic pneumonia (control (2 animals), 2500 ppm (1)), Discharge of follicles in the spleen and progressed thymus involution (2500 ppm (1)), bilateral testicle atrophy (2500 ppm (1)), pituitary cyst (control (1), 2500 ppm (1)), unilateral dilatation of uterine horns (2500 ppm (2)), slight foreign body reaction in the greater omentum (2500 ppm (2)), slight phagocytosis of hematogen pigment in lymph nodes (2500 ppm (1)), unspecific inflammatory-cellular infiltration of the eye (control (1), 2500 ppm (3)) resp. traches (2500 ppm (1)).
The organs of the rats which died during the study were autolytically altered; other changes were not noted.

Dose descriptor:

NOAEL

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on the average food consumption and mean body weight of the animals in the mid of the study, this corresponds to 7.91 mg/kg bw/d (males) and 9.78 mg/kg bw/d (females).

Dose descriptor:

LOAEL

Effect level:

500 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: body weight; food consumption Based on the average food consumption and mean body weight of the animals in the mid of the study, this corresponds to 42.70 mg/kg bw/d (males) and 49.54 mg/kg bw/d (females).

Dose descriptor:

LOAEL

Effect level:

2 500 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: mortality; clinical chemistry; urinalysis; Based on the average food consumption and mean body weight of the animals in the mid of the study, this corresponds to 202.54 mg/kg bw/d (males) and 228.87 mg/kg bw/d (females).

Critical effects observed:

not specified

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Conclusions:

The study was conducted prior to GLP similar to OECD guideline 408 on the registered substance itself The method is to be considered scientifically reasonable with minor deficiencies in documentation and performance, e.g. dosing intervals were chosen as 5-fold instead of 2-4-fold. Hence, the results can be considered as sufficiently reliable to assess the repeated dose oral toxicity in rats.
3-methylthiazolidine-2-thione did not induce any relevant effects in male and female rats under the conditions of the test in the dosage of 100 ppm. Hence, the NOAEL can be set as 100 ppm, which corresponds based on feed intake determinations to 7.91 mg/kg bw/day in males and 9.78 mg/kg bw/day in females.

Executive summary:

In a subchronic toxicity study similar to OECD 408 3-methylthiazolidine-2-thione was administered to 15 SPF, Wistar-TNO W.74 rats/sex/dose in diet at dose levels of 0, 100, 500, 2500 ppm.

 

Appearance and behaviour were not influenced in male and female rats at dosages up to 2500 ppm. 2 males of the high dose group died during the course of the study.

Food consumption and growth were not influenced in the 100 ppm group. In the 500 and 2500 ppm group food consumption and body weight gain were diminished significantly (p<0.01) during the whole study duration. A repellent effect of the test item cannot be excluded.

Blood was not damaged by the test item in the groups up to 500 ppm. An intermittent influence on the leucocytes was noticed after one month in the 2500 ppm group, which could not be observed after 3 months.

Clinical analyses, necropsies as well as histopathological examinations revealed no indication on of treatment-related adverse effects to the liver in dosages up to 500 ppm. After one month an increase of the enzymes GOT and GPT as well as a decrease in plasma protein was noted in the 2500 ppm group. These differences compared to control could not be observed at the end of the study.

Urinalysis, clinical analyses,necropsies as well as histopathological examinations revealed no indication on kidney damages in the dosage groups up to 500 ppm. At the 2500 ppm group elevated urea concentrations were noted.

Blood sugar and cholesterol concentrations were in dosages up to 2500 ppm within the norm.

Thyroid function was not influenced by the test item in the dosage groups up to 100 ppm.

Necropsies and histopathological examinations gave no indications on treatment-related effects on any organs in groups up to 2500 ppm.

Dosages of 100 ppm of the test item were tolerated under these conditions without any effects.

 

The LOAEL is 500 ppm, based on changes in body weight and food consumption. The NOAEL is 100 ppm.

 

This subchronic toxicity study in the rat is acceptable, and satisfies scientifically sufficiently the guideline requirement for a subchronic oral study (OECD 408) in rats.

Reference 2

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study performed in a scientifically reasonable manner to examine the limited endpoints with some deficiencies in documentation, but the given data indicate that the results with regard to the examined endpoints can be considered reliable.

Qualifier:

no guideline followed

Principles of method if other than guideline:

50 mg were daily orally given to each 10 rats over a period of 6, 12, and 23 days

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

other: Wistar-II

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann animal breeder (Kirchborchen, Paderborn district) and Gierlich animal breeder (Bochum)
- Weight at study initiation: 160-210g
- Housing: macrolon cages, Type III
- Diet (e.g. ad libitum): Altromin R Standard diets (Altromin GmbH, Lage/Lippe) ad libitum
- Water (e.g. ad libitum): ad libitum

Route of administration:

oral: gavage

Vehicle:

other: Cremophor-water mixture

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Emulsion with Cremophor-water mixture

VEHICLE
- Amount of vehicle (if gavage): Total volume 10ml/kg

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

5, 12, 23 or days

Frequency of treatment:

once a day

Remarks:

Doses / Concentrations:
50 mg/kg
Basis:
other: nominal by gavage

No. of animals per sex per dose:

10 mals / dose

Control animals:

yes, concurrent vehicle

Positive control:

50 mg/kg ethylene thiourea

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: on day 0, 6, 12, 19 and 23 (up to sacrifice of the respective grop)

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER: weight of thyroid glands at sacrifice

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, thyroid glands

Statistics:

Thyroid glands were weighed and their relative weights as well as the body weights were compared statistically with the help of a distribution-free total ranking test based on WILCOXON (Biometrics 3, 119, 1947).

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

reduced body weight compared to vehicle control

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

thyroid gland weight comparable to control

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Details on results:

As can be seen in the table (average values of the body weights and the thyroid gland weights), the increase in body weight of the rats treated with N-Methyl-2-thion-thiazolidine or ethylene thiourea was significantly lower (p <0.01 or p <0.05) than with the control animals after the first week of treatment.
A statistical comparison of the relative thyroid gland weights of the animals treated with ethylene thiourea showed that the thyroid gland weights were significantly (p <0.01) higher after 6-day treatment and after 23-day treatment than with the control animals. On the other hand, there was no significant difference between the thyroid gland weights of the animals treated with ethylene thiourea and those of the control animals after the 12-day treatment. The thyroid gland weights of the animals treated with N-Methyl-2-thion-thiazolidine were not significantly different after 6-day treatment and 23-day treatment from the thyroid gland weights of the control group. After 12-day treatment, the thyroid gland weight of the animals treated with N-Methyl-2-thion-thiazolidine was significantly lower (p <0.05) than with the control animals. This significance nevertheless arises purely mathematically through the random higher relative thyroid gland weight of the 10 control animals killed after the 12-day treatment. The relative thyroid gland weights which appear to be significantly lower are therefore not to be attributed to the treatment with N-Methyl-2-thion-thiazolidine.
If one compares the relative thyroid gland weights of the rats treated with N-Methyl-2-thion-thiazolidine, it appears that these weights were practically the same after 6-day treatment, after 12-day treatment and after 23-day treatment and also agreed with the thyroid gland weights of the control animals after 6-day treatment and after 23-day treatment.
On the basis of the results of these examinations, it can be said that there was no influence on the thyroid gland weights with the continuous application of 50 mg N-Methyl-2-thion-thiazolidine/kg body weight for up to 23 days.

Dose descriptor:

NOEL

Effect level:

>= 50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: relative / absolute thyroid gland weight for up to 23 days

Dose descriptor:

LOEL

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: body weight

Critical effects observed:

not specified

Table: Average values of the body weights and the thyroid gland weights

Compound applied	Body weights in g after days					Thyroid gland weights in mg
	At start	6	12	19	23	Absolute	relative
N-Methyl-2-thion-thiazolidine	138	168**	-	-	-	12	8.7
Control	138	180	-	-	-	11	8.0
Ethylene thiourea	138	162**	-	-	-	19	13.8**
N-Methyl-2-thion-thiazolidine	138	164	177**	-	-	12	8.7*
Control	138	175	195	-	-	14	10.1
Ethylene thiourea	138	164	180**	-	-	16	11.6
N-Methyl-2-thion-thiazolidine	138	165	176	185	203**	11	8.0
Control	138	178	200	222	230	12	8.7

Conclusions:

The study was performed in a scientifically reasonable manner to examine the limited endpoints with some deficiencies in documentation, but the given data indicate that the results with regard to the examined endpoints can be considered reliable. Hence, the results are considered sufficiently reliable to study the effect of N-Methyl-2-thion-thiazolidine on body weight and thyroid gland of rats. The examined 50 mg/kg turned out to be the LOEL resp. NOEL. The result can be used to support the resultes derived from the available 90 day study.

Executive summary:

The daily administration of 50 mg N-Methyl-2-thion-thiazolidine/kg body weight in a Cremophor-water mixture to groups of 10 rats each during a period of 6,12 and 23 days did not lead to swelling of the thyroid. The increase in body weight of the rats treated with

N-Methyl-2-thion-thiazolidine o

r ethylene thiourea was significantly lower (p <0.01 or p <0.05) than with the control animals after the first week of treatment.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

7.91 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

There is a Klimisch 2 study similar to OECD 408 on rats available. According to the guideline, the results from the TG 408 should be used for hazard identification and risk assessment, indicating that the guideline is generally suitable for human risk assessment and the rat may serve as an adequate model for humans, of course with adequate uncertainty factors which will be considered when delineating DNELs. The study was designed to provide a sufficient statistical power, the observed effects were dose-dependent, and there were no reasons to believe that the results are not biologically plausible or not relevant for humans. Further, there are two other studies available with either a shorter exposure duration or application route, indicating that the presented NOAEL (for males, the one for females was found to be higher) is the most conservative one. For Annex VIII of REACH only a 28-day study is required with the most relevant application route for human risk assessment is required, unless a reliable sub-chronic (90 days) or chronic toxicity study is available, provided that an appropriate species, dosage, solvent and route of administration were used. The oral route was considered as most relevant as it allows best an assessment of general systemic effects. The available study exceeds with regard to exposure duration the actual requirements, giving more reliable information on the effects of repeated exposure due to the prolonged exposure. So, the tonnage-driven data requirements can be considered as fully met, and in summary the database is of high quality.

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: inhalation

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to REACH Annex VIII column 1 (8.6.1), the following study for repeated dose toxicity is required: Short-term repeated dose toxicity study (28 days), one species, male and female, most appropriate route of administration, having regard to the likely route of human exposure. Further, according to column 2, the short-term toxicity study (28 days) does not need to be conducted if i.a. a reliable sub-chronic (90 days) or chronic toxicity study is available, provided that an appropriate species, dosage, solvent and route of administration were used.
There is a suitable Klimisch 2 oral toxicity study available, conducted in a scientifically reasonable manner similar to OECD 408 and assessing the toxicological properties of 3-methyl-1,3-thiazolidine-2-thione after oral gavage over 90 days.
In general, the oral route is the most suitable one to assess systemic effects in humans, which is the main aim of this endpoint. The dermal or inhalative route is only scientifically relevant in case of considerable exposure, any route-specific toxicological mode of action or local effects, whereas sufficient information on the latter can be gained via irritation tests (REACH No. 8.1. or 8.2).
According to REACH Annex VIII column 2 (8.6.1), testing by the inhalation route is appropriate if exposure of humans via inhalation is likely taking into account the vapour pressure of the substance and/or the possibility of exposure to aerosols, particles or droplets of an inhalable size.
The substance is a solid which is not manufactured, handled or distributed as a powder but only in a pelleted form. Hence, exposure of humans to any dust can be excluded. Further, the substance has a boiling point of 341-344°C and consequently a rather low vapour pressure of 2.2 x 10E-04 hPa at 25°C. So, the exposure to 3-methyl-1,3-thiazolidine-2-thione via inhalation of vapour can be disregarded as no vapour will be formed during handling. Also, the substance is not distributed as e.g. aqueous solution, so the formation of inhalable droplets or aerosols can furthermore be excluded.

Further, there is a supporting subacute study available, in which mice, rats, hamsters, and rabbits were exposed to the via a electrical heating pot artificially created vapours 5 times for 4 hours, which is not relevant for real life handling. Exposure was daily to 2108 resp. 2613 mg/m³. According to ECHA’s guidance document R.8, the standard respiratory volume of e.g. the rat is 1.15 m³/kg/d. Based on a 4h exposure, this corresponds to a dose of five times 404.0 resp. 500.8 mg/kg. No symptoms of poisoning occurred on the 5th day of testing or during the 14-day post-observation time with the animals. In the available 90 day oral (feed) study, the NOAEL was set as 100 ppm, which corresponds based on feed intake determinations to 7.91 mg/kg bw/day in males and 9.78 mg/kg bw/day in females. Even with an assessment factor of 3 for the extrapolation of subacute to subchronic study duration, the determined value for inhalation toxicity is much higher than the oral NOAEL, clearly indicating that additional inhalation testing would not provide any relevant additional information.

In consequence, the available 90 day oral toxicity study similar to OECD 408 is sufficient to cover this endpoint, no repeated dose testing via inhalation route needs to be performed and can consequently be waived due to animal welfare.

Reference 2

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study performed in a scientifically reasonable manner to examine the limited endpoints with some deficiencies in documentation, but the given data indicate that the results with regard to the examined endpoints can be considered reliable.

Principles of method if other than guideline:

The animals were exposed to the vapours 5 times for 4 hours. After the exposure, the animals were observed 14 days long.

GLP compliance:

no

Remarks:

test conducted prior to GLP implementation

Limit test:

no

Species:

other: mice, rats, hamsters, rabbits

Strain:

other: NMRI mice, Wistar-II rats, Syrian gold hamsters and albino rabbits

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann animal breeder (Kirchborchen, Paderborn district) and Gierlich animal breeder (Bochum)
- Weight at study initiation: 160-210g (rats), 25-31g (mice), 60-75g (hamsters), 3.5-4.3kg (rabbits)
- Housing: macrolon cages, Type III (rats, mice, hamsters), individually in standard rabbit cages (Manufacturer: E. Pluppins, Hamburg) (rabbits)
- Diet (e.g. ad libitum): Altromin R Standard diets (Altromin GmbH, Lage/Lippe) (mice, rats), ssniff full diet feed for hamsters (Intermast GmbH, Bockum-Hövel) (hamsters), Höing rabbit feed (rabbits) ad libitum
- Water (e.g. ad libitum): ad libitum

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

not specified

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: electrical heating pot (vapour)
- Exposure chamber volume: 20L cylinder (dust) / 0.4m³ chamber (vapour)

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph with the help of a nitrogen detector (vapour)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

gas chromatography

Duration of treatment / exposure:

The animals were exposed to the vapours 5 times for 4 hours.

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
2108 mg / m³ air
Basis:
other: analytical conc. for mice, rats

Remarks:

Doses / Concentrations:
2613 mg / m³ air
Basis:
other: analytical conc. for hamsters, rabbits

No. of animals per sex per dose:

Total number for single dose: 20 mice, 10 rats, 5 hamsters, 2 rabbits

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days
- Other examinations performed: clinical signs

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes

BODY WEIGHT: Yes

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, mucous membranes of eye and nose, cornea

Clinical signs:

no effects observed

Description (incidence and severity):

No symptoms of poisoning occurred on the 5th day of testing or during the 14-day post-observation time with the animals.

Mortality:

no mortality observed

Description (incidence):

No symptoms of poisoning occurred on the 5th day of testing or during the 14-day post-observation time with the animals.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

A slight reduction of body weight was to be reported after the 5-day exposure with rats and hamsters. Normal body weight increases occurred again during the 14-day post-observation time with these animals.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

no changes on the cornea

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Description (incidence and severity):

Changes also did not appear on the mucous membranes of the nose or eyes or on the cornea.

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Details on results:

Concentrations of 2108 mg/m³ air were borne by male and female rats and mice with a 5 x 4hour exposure and concentrations of 2613 mg/m³ air by male and female hamsters and rabbits. No symptoms of poisoning occurred on the 5th day of testing or during the 14-day post-observation time with the animals. Changes also did not appear on the mucous membranes of the nose or eyes or on the cornea after a once-only four-hour exposure or after a 5x four-hour exposure. A slight reduction of body weight was to be reported after the 5-day exposure with rats and hamsters. Normal body weight increases occurred again during the 14-day post-observation time with these animals.

Dose descriptor:

NOAEC

Effect level:

>= 2 108 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: mortality; body weight (rats, mice)

Dose descriptor:

NOAEC

Effect level:

2 613 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: mortality (hamsters, rabbits)

Dose descriptor:

LOEC

Effect level:

2 613 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: slight reduction of body weight after day 5 of exposure in hamsters and rabbits

Critical effects observed:

not specified

Table: Exposure conditions and results

N-Methyl-2-thion-thiazolidine / g		Concentration mg/m³ air / measured	Vaporizing Temperature / °C	Test duration / hours	Type of animal	Toxicol. Results after 14 days*
Inserted	vaporized
10.0	9.895	2108	200	5x4	Mice rats	0/0/20 0/0/10
10.0	9.880	2613	200	5x4	Hamsters rabbits	0/0/5 0/0/2

*1^stNumber = Number of dead animals

2^ndNumber = Number of animals with symptoms

3^rdNumber = Number of animals used

Conclusions:

The study was performed in a scientifically reasonable manner to examine the limited endpoints with some deficiencies in documentation, but the given data indicate that the results with regard to the examined endpoints can be considered reliable. Hence, the results are considered sufficiently reliable to study the effect of N-Methyl-2-thion-thiazolidine by inhalative exposure on rats, mice, hamsters and rabbits with regard to signs of poisoning or mortality. There were no relevant effects on the animals at vapiur concentrations of 2108 resp. 2613 mg/m³ air. The result can be used to support the results derived from the available oral 90 day study.

Executive summary:

When rats, mice, hamsters and rabbits were exposed to N-Methyl-2-thion-thiazolidine vapours for 4 hours at a time on five successive days, a concentration of 2108 mg/m³ air was borne by male and female rats and mice, and 2613 mg/m³ by rabbits. Symptoms of poisoning did not occur with the test animals on the 5 test days or during the 14-day post-observation time.

Changes also did not occur in the mucous membranes of noses and eyes or on the cornea after inhalation of dust and vapours, so NOECs were determined as ≥ 2108 mg/m³ air (mice, rats) resp. ≥ 2613 mg/m³ (hamsters, rabbits).

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to REACH Annex VIII column 1 (8.6.1), the following study for repeated dose toxicity is required: Short-term repeated dose toxicity study (28 days), one species, male and female, most appropriate route of administration, having regard to the likely route of human exposure.
Further, according to column 2, the short-term toxicity study (28 days) does not need to be conducted if i.a. a reliable sub-chronic (90 days) or chronic toxicity study is available, provided that an appropriate species, dosage, solvent and route of administration were used.
There is a suitable Klimisch 2 oral toxicity study available, conducted in a scientifically reasonable manner similar to OECD 408 and assessing the toxicological properties of 3-methyl-1,3-thiazolidine-2-thione after oral gavage over 90 days.
In general, the oral route is the most suitable one to assess systemic effects in humans, which is the main aim of this endpoint. The dermal or inhalative route is only scientifically relevant in case of considerable exposure, any route-specific toxicological mode of action or local effects, whereas sufficient information on the latter can be gained via irritation tests (REACH No. 8.1. or 8.2).
According to REACH Annex VIII column 2 (8.6.1), the appropriate route shall be chosen on the following basis: Testing by the dermal route is appropriate if: (1) inhalation of the substance is unlikely; and (2) skin contact in production and/or use is likely; and (3) the physicochemical and toxicological properties suggest potential for a significant rate of absorption through the skin.
Although inhalation of 3-methyl-1,3-thiazolidine-2-thione is unlikely, the latter conditions do not apply. Skin contact in production and/or use is unlikely as all identified process categories indicate no likelihood of exposure, i.e. use in closed process, no likelihood of exposure, all transfer is done in dedicated vessels or filling lines.
The physicochemical and toxicological properties do not suggest potential for a significant rate of absorption through the skin. Skin absorption is influenced by several factors, i.a.:
- Molecular weight: Less than 100 favors dermal uptake. Above 500 the molecule may be too large. With a molecular weight of 133.2351 g/mole, absorption is possible, possibly even favoured.
- LogPow: For substances with Log P values <0, poor lipophilicity will limit penetration into the stratum corneum and hence dermal absorption. Values <–1 suggest that a substance is not likely to be sufficiently lipophilic to cross the stratum corneum, therefore dermal absorption is likely to be low. Values between 1 and 4 are favourable for absorption. Since 3-methyl-1,3-thiazolidine-2-thione has a logPow of 0.59 at 20.3°C, dermal absorption may be possible, but less likely to occur.
- Water solubility: If water solubility is above 10,000 mg/l and the Log P value below 0 the substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum. Dermal uptake for these substances will be low. As stated above, log Pow is 0.59, and additionally, the substance was found to be rather soluble in water, i.e. 3.65 g/L (at 30°C and pH 4.7). Also here, dermal absorption may occur to a minor extent due to the moderate to high hydrophilicity of the compound.
- Skin irritation / corrosion: If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration. 3-methyl-1,3-thiazolidine-2-thione was not classified as irritant to the skin. Further, the substance does not need to be classified as irritating to the eye, which is in general considered to be more sensitive than the skin. Last but not least, in the available LLNA, no evidence of systemic toxicity or irritation was found. Therefore, no additional penetration enhancement must be considered.
In consequence, the available 90 day oral toxicity study similar to OECD 408 is sufficient to cover this endpoint, no repeated dose testing via dermal route needs to be performed and can consequently be waived due to animal welfare.

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Mode of Action Analysis / Human Relevance Framework

The available most sensitive NOAEL is 100 ppm in feed corresponding to 7.91 mg/kg bw/d (males) and 9.78 mg/kg bw/d, the LOAEL is 500 ppm corresponding to 42.70 mg/kg bw/d (males) and 49.54 mg/kg bw/d (females), based on food consumption and body weight changes. These effects do not give any indication on a possible mode of action and may also be attributable to the palatability of the test item in feed. A further LOAEL, based on mortality, clinical chemistry and urinalysis, was determined to be 2500 ppm corresponding to 202.54 mg/kg bw/d (males) and 228.87 mg/kg bw/d (females).

Based on the minor severity of the observed effects and the absence of any other test item related effects, it is rather impossible to hypothesize a concrete mode of action.

The associated findings are in detail:

An intermittent influence on haematology was observed, which could not be observed after 3 months: The males exhibited a significantly decreased thrombocyte (500 and 2500 ppm) and leucocyte count (2500 ppm). In the 2500 ppm animals, the amount of neutrophile granulocytes with segmented nucleus was significantly elevated, in the females of the 500 ppm group and the 2500 ppm animals the leucocyte count was significantly decreased. This may be considered as a transient adaption with minor severity and does not give any concrete indication on a possible MoA.

An intermittent increase after 1 month of the enzymes GOT and GPT, a decrease in plasma protein and persistent elevated urea concentration was noted in the 2500 ppm group. After 3 months, there were no treatment-related differences regarding ALP, GOT, GPT, GLDH and Bilirubin up to 2500 ppm. Total plasma protein was decreased in the 2500 ppm females.

This indicates an involvement of liver and kidney, which is not unusual taking into account the regular pathway of xenobiotic absorption (via portal vein), transformation (to a major extent in the liver) and excretion (via kidneys). These effects however must also be considered as minor severe, taking into account the transient nature of these findings resp. the fact that there was no histopathological evidence for the involvement of these organs. Also here, no distinct MoA could be identified.

Relative organ weights were in the 2500 ppm group significantly increased, except thymus (males) and spleen, adrenal glands and ovaries (females). Furthermore, in the 500 ppm group the weights of thymus, heart, liver, spleen and kidneys were decreased, the ones of the testicles were increased.

However, necropsies and histopathological examinations gave no indications on treatment-related effects on any organs in groups up to 2500 ppm.

So in consequence, no specific mode of action can be postulated, and even if the noted effects are relevant for humans, too, it can be postulated that a decreased number of leucocytes and thrombocytes could be considered as minor adaptive response, as well as the (transient) influences on GOT and GPT, bilirubin and plasma protein. Here, no definitive human relevance framework can be described due to the lack of any other effects securing any postulation, and no conclusion on biological plausibility can be drawn.

Despite the fact that no mode of action analysis can be performed, no data gap was identified here. The tonnage-driven data requirements under REACH were fully met, and the lack of severity of the observed effects does also not indicate any high hazard for humans and so does not trigger any further examinations.

Justification for classification or non-classification

Generally, according to Regulation (EC) No. 1272/2008, the LOAEL of 42.70 mg/kg bw/d (males) resp. 49.54 mg/kg bw/d (females) may trigger a classification as STOT RE Cat. 2 as it is generally below the guidance value of 100 mg/kg for subchronic studies.

 

Target organ toxicity (repeated exposure), as defined by the Regulation, “means specific, target organ toxicity arising from a repeated exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed are included. … Classification for target organ toxicity (repeated exposure) identifies the substance as being a specific target organ toxicant and, as such, it may present a potential for adverse health effects in people who are exposed to it”. Furthermore, “substances are classified as specific target organ toxicants following repeated exposure by the use of expert judgement”, and “3.9.2.7. Effects considered to support classification for specific target organ toxicity following repeated exposure...

... (c) any consistent and significant adverse change in clinical biochemistry, haematology, or urinalysis parameters;”

But also: “3.9.2.8. Effects considered not to support classification for specific target organ toxicity following repeated exposure

3.9.2.8.1. It is recognised that effects may be seen in humans and/or animals that do not justify classification. Such effects include, but are not limited to: ...

... (b) small changes in clinical biochemistry, haematology or urinalysis parameters and/or transient effects, when such changes or effects are of doubtful or minimal toxicological importance; ...

... (d) adaptive responses that are not considered toxicologically relevant;”

 

Based on the available information, a classification as STOT RE Cat. 2 is not considered necessary as will be outlined below.

The LOAEL of 42.70 mg/kg bw/d (males) resp. 49.54 mg/kg bw/d (females) is based on the noted effects on food consumption and body weight. These effects cannot be attributed to any specific effect on a possible target organ.

The next higher dosage level resulting in a further LOAEL based on mortality, clinical chemistry and urinalysis, was 2500 ppm which corresponds to 202.54 mg/kg bw/d (males) and 228.87 mg/kg bw/d (females). So irrespective of the nature and severity of the effects (minor severity, mostly transient, no histopathological confirmation of organ involvement, presumably of adaptive nature), the determined dose levels are more than two-fold higher than the guidance value for classification as STOT RE (100 mg/kg bw/d). Hence, no classification of 3-methylthiazolidine-2-thione as STOT RE is triggered.