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Description of key information

Skin sensitization:
- Bühler Assay, guinea pig (Pirbright White) m/f, OECD 406, on ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol’ (Key study): non-sensitizing
- Bühler Assay, guinea pig (Hartley) m/f, OECD 406, on ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol’ (Supporting study): non-sensitizing
- Bühler Assay, guinea pig (Hartley) m/f, OECD 406, on ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol’ (Supporting study): non-sensitizing
- Bühler Assay, guinea pig (Hartley) m/f, OECD 406, on ‘5-(dodecyldithio)-1,3,4-thiadiazole-2(3H)-thione’ (5%) (Supporting study): non-sensitizing
- Bühler Assay, guinea pig (Hartley) m/f, OECD 406, on ‘5-(dodecyldithio)-1,3,4-thiadiazole-2(3H)-thione’ (undiluted) (Disregarded study): sensitizing

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1993-03-11 - 1993-04-22
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-Guideline study without deviations on ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol’.
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Umweltministerium Baden-Württemberg, Stuttgart, Germany
Type of study:
Buehler test
Justification for non-LLNA method:
There was a OECD 406 available which had been performed in 1993. It fulfills all the criteria and there was no need to do further animal testing (LLNA)
Species:
guinea pig
Strain:
other: Pirbright White
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Interfauna, Süddeutsche Versuchstierfarm, Tuttlingen, Germany
- Age at study initiation: younger than 1 year
- Weight at study initiation: 333 g (males), 273 g (females), mean values
- Housing: individually in Macrolon cages (area 780 cm²)
- Diet: Raiffeisen-Ringfutter, dry food 52/P (Raiffeisen Kraftfutterwerk Kehl, Germany), ad libitum
- Water: community tap water supplemented with 20 mg/100 mL L-ascorbic acid and 100 mg/100 mL citric acid, ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-22
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12 / 12
Route:
epicutaneous, occlusive
Vehicle:
other: Pilot study: sesame oil (Carl Roth GmbH&Co., item No. 9335); Main study: unchanged (no vehicle)
Concentration / amount:
Pilot study: 12.5 %, 25 %, 50 %, 100 %
Main study: 100 % for induction and challenge
Route:
epicutaneous, occlusive
Vehicle:
other: Pilot study: sesame oil (Carl Roth GmbH&Co., item No. 9335); Main study: unchanged (no vehicle)
Concentration / amount:
Pilot study: 12.5 %, 25 %, 50 %, 100 %
Main study: 100 % for induction and challenge
No. of animals per dose:
Pilot study: 2
Main study: 10 (5 males and 5 females)
Details on study design:
PILOT STUDY:
- No. of exposures: 1
- Exposure period: 6 h
- Site: clipped and covered by occlusive bandage
- Concentrations: 0.3 mL of 0%, 12.5%, 50%, 100%
- Evaluation: 1, 24, 48 and 72 h after application

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3
- Exposure period: 6 h
- Test groups: test substance
- Control group: untreated
- Site: clipped area of 4x6 cm² of the left flank (24 h before application), covered with occlusive bandage made of an impermeable plastic tape and an elastic gauze
- Frequency of applications: every 7 days
- Duration: 14 days
- Concentrations: 100% (0.3 mL)

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: day 28
- Exposure period: 6 h
- Test groups: test substance
- Control group: test substance
- Site: clipped area of 4x6 cm² of the right flank (24 h before application), covered with occlusive bandage made of an impermeable plastic tape and an elastic gauze
- Concentrations: 100% (0.3 mL)
- Evaluation (hr after challenge): 24 and 48 h after application
Challenge controls:
No information available.
Positive control substance(s):
not specified
Remarks:
No positive control substance recorded.
Positive control results:
Not applicable.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
100%
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 100%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
100%
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 100%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
100%
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 100%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
100%
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 100%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.
Group:
positive control
Remarks on result:
not measured/tested

Result of pilot study:

Skin reactions:
Time after application
Concentration Animal No. 1 h 24 h 48 h 72 h
12.50% 1 none none none none
2 none none none none
25.00% 1 none none none none
2 none none none none
50.00% 1 none none none none
2 none none none none
100.00% 1 none none none none
2 none none none none
control 1 none none none none
2 none none none none

None of the animals died or showed signs of toxicological symptoms. The behaviour pattern was not different to that of non treated guinea pigs (control).

Main study:

Body weight (g) on day
Animal Number -5 0 7 14 21 28 29 30
Test Group Males 11 332 380 425 479 510 590 587 587
12 367 433 461 518 530 580 585 586
13 329 372 400 457 479 613 624 623
14 335 378 418 431 458 530 544 545
15 329 378 416 472 507 566 547 546
mean 338 388 424 391 497 576 577 577
Females 16 200 247 240 272 320 418 425 425
17 243 300 337 394 416 518 500 503
18 300 310 314 385 412 508 507 510
19 244 265 310 355 389 452 455 455
20 212 260 275 348 359 485 470 469
mean 240 276 295 351 379 476 471 472
Control Group Males 21 265 305 330 355 418 481 502 505
22 327 359 400 150 479 576 567 570
23 348 384 412 474 499 552 558 558
24 327 335 370 437 458 531 545 545
25 349 400 449 515 540 647 646 647
mean 323 357 392 386 479 557 564 565
Females 26 280 325 350 410 447 500 507 510
27 289 332 368 424 450 519 530 528
28 265 312 350 391 428 442 500 499
29 337 353 370 399 432 402 468 470
30 352 395 441 480 516 528 565 567
mean 305 343 376 421 455 478 514 515
Interpretation of results:
not sensitising
Remarks:
Criteria used for interpretation of results: EU-GHS
Conclusions:
The study was conducted according to OECD Guideline 406 and is considered as valid. The control group also showed no skin reactions.
As no animal in the test group showed any skin reaction after application of the test substance a classification is not required, neither according to EU Directive 67/548/EEC nor according to EC Regulation 1272/2008. The test item can be regarded as non-sensitising.
Executive summary:

The test substance (1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol) was tested in a GLP study according to OECD Guideline 406 for its sensitising potential in order to determine whether there is any specific (sensitising) or non-specific (irritant) stimulating potential of the test substance (Biochem, Grunert, 1993). In a pilot study the test item was tested dermally, occlusive and thinned to 12.5 %, 25 %, 50 % and 100 % in sesame oil over a period of 6h with a single exposure. Each dose group consisted of 2 guinea pigs (Pirbright White, age < 1a), an area of 4 cm x 6 cm was clipped and exposed to 0.3 mL of the test item, the post-exposure period was 72 h. Additionally, a control group was not exposed to the test item. After 1 h, 1 d, 2 d and 3 d the treated skin was checked for irritation. At no time point and in no animal any skin reactions were observed. Therefore, the undiluted test item was chosen for the main study. In the main study, a test group and a control group consisting each of 10 guinea pigs (5 males / 5 females) were used. The test group was exposed occlusive during the induction phase three times (day 0, 7, 14) over 6 h to 0.3 ml the test item onto 4 cm x 6 cm clipped skin. The control group was not exposed to the test item but was treated the same way regarding clipping and the occlusive bandage. After two weeks free from all treatment the test item was applied similar to the induction phase on day 28 to both groups (test animals as well as control animals) over 6 h. 24 h and 48 h after the challenge skin readings were performed. No animal, neither control nor test group, exhibited any skin reaction. Therefore, the substance can be regarded as non-sensitising.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Skin sensitisation

There is one key study available to evaluate the skin sensitisation potential of the target substance '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol'.

'1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol' was tested in a GLP study according to OECD Guideline 406 for its sensitising potential in order to determine whether there is any specific (sensitising) or non-specific (irritant) stimulating potential of the test substance (Biochem, Grunert, 1993). In a pilot study the test item was tested dermally, occlusive and thinned to 12.5 %, 25 %, 50 % and 100 % in sesame oil over a period of 6h with a single exposure. Each dose group consisted of 2 guinea pigs (Pirbright White, age < 1a), an area of 4 cm x 6 cm was clipped and exposed to 0.3 mL of the test item, the post-exposure period was 72 h. Additionally, a control group was not exposed to the test item. After 1 h, 1 d, 2 d and 3 d the treated skin was checked for irritation. At no time point and in no animal any skin reactions were observed. Therefore, the undiluted test item was chosen for the main study. In the main study, a test group and a control group consisting each of 10 guinea pigs (5 males / 5 females) were used. The test group was exposed occlusive during the induction phase three times (day 0, 7, 14) over 6 h to 0.3 ml the test item onto 4 cm x 6 cm clipped skin. The control group was not exposed to the test item but was treated the same way regarding clipping and the occlusive bandage. After two weeks free from all treatment the test item was applied similar to the induction phase on day 28 to both groups (test animals as well as control animals) over 6 h. 24 h and 48 h after the challenge skin readings were performed. No animal, neither control nor test group, exhibited any skin reaction.

In the first supporting study, the dermal sensitisation potential of the structurally similar short-chain homologue ‘1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol' (CAS No. 91648 -65 -6) was evaluated in Hartley-derived albino guinea pigs following OECD Guideline 406, EPA OPPTS 870.2600 and EU Method B.6 (Rodabaugh, 2006). Ten male and ten female guinea pigs were topically treated with 100 % (as received) test material once per week, for three consecutive weeks. Following a 2-week rest period, a challenge was performed whereby the 20 test and 10 previously untreated (naive) challenge control guinea pigs were topically treated with 100 % (as received) test material. Challenge responses in the test animals were compared with those of the challenge control animals. An α-Hexylcinnamaldehyde (HCA) positive control group consisting of ten HCA test and ten HCA control guinea pigs was included in this study. The animals were treated as above with the HCA test animals receiving 5 % w/v HCA in ethanol for induction and 2.5 % and 1.0 % w/v HCA in acetone for challenge. Following challenge with 100 % test material, dermal reactions in the test animals were limited to scores of 0 to ±. Dermal reactions in the challenge control animals were limited to scores of 0. Group mean dermal scores were noted to be slightly higher in the test animals as compared with the challenge control animals. Following challenge with 2.5 % w/v HCA in acetone, dermal scores of 1 were noted in 2/10 HCA test animals at the 24- and 48-hour scoring intervals. Dermal reactions in the remaining HCA test animals were limited to scores of 0 and ±. Dermal reactions in the HCA challenge control animals were limited to scores of 0. Group mean dermal scores were noted to be higher in the HCA test animals as compared with the HCA challenge control animals. Following challenge with 1.0 % w/v HCA in acetone, a dermal score of 1 was noted in 1/10 HCA test animals at the 24-hour scoring interval. Dermal reactions in the remaining HCA test animals were limited to scores of 0 and ±. Dermal reactions in the HCA challenge control animals were limited to scores of 0. Group mean dermal scores were noted to be higher in the HCA test animals as compared with the HCA challenge control animals.

In another supporting study on the short-chain homologue with CAS 91648 -65 -6 (including topical range-finding study prior to the induction phase), the test was conducted following EPA OPPTS 870.2600 and OECD Guideline 406 (Smedley, 2003). The substance was applied at a volume of 0.3 mL to the backs of 10 male and 10 female guinea pigs. Test concentrations were selected as followed: 100 % during the induction phase, 75 % during the challenge phase (on induced and non-induced animals), 75 % and 50 % during the rechallenge phase (on induced and non-induced animals). On the day prior to test material exposure, the hair was removed from each of the animals’ backs. The test preparations were applied into 25 mm test chambers and then applied to the clipped surface as quickly as possible. The chambers were occluded with elastic wrap which was secured with adhesive tape to prevent removal of the chamber. Approximately six hours later the binding materials were removed. The test sites were wiped with gauze moistened in mineral oil, followed by dry gauze, followed by gauze moistened in deionized water, followed by dry gauze, to remove test article residue.This procedure was carried out once per week for 3 weeks (induction phase). A primary challenge was then carried out 2 weeks later using the same application procedure as used in the induction phase. This procedure was carried out in the induced animals and in a further group of naive animals. A rechallenge application was then carried out one week after the primary challenge. Scoring was conducted at 24 h (1st reading) and 48 h (2nd reading) following the primary challenge and the rechallenge phases. 2 animals showed positive skin reactions in the test group (75 % substance concentration) at the 2nd reading. The same observation was recorded at the first and second readings of the rechallenge in the test group with 50 % and 75 % test concentrations, respectively. One female had transient incidences of entire body reddened and warm to the touch (days 8 to 12), faeces small in size and decreased food consumption (day 8). Since these findings were transient in nature and limited to just one animal, these findings are not considered to be test article related. The sensitisation study animals gained weight during the test period and generally appeared in good health. Hexylcinnamaldehyde (HCA) was used as positive control. Following challenge with this substance, HCA test animals were noted to have a stronger dermal response than was observed in the corresponding HCA control animals (4 out of 10 animals showed a positive response at 48 h at the 2.5 % dose level). The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitisers.

In another supporting study, the skin sensitisation study was conducted using a similar procedure to that described in the current OECD Guideline 406 (Morris, 1994). The read-across substance (CAS No. 50530-43-3), 5 % dilution in base oil (EX-80/90 BO), was applied at a volume of 0.3 mL to the backs of 10 male and 10 female guinea pigs. The test article was left in contact with the skin for 6 hours. This procedure was carried out once per week for 3 weeks (induction phase). A primary challenge was then carried out 2 weeks later using the same application procedure as used in the induction phase. This procedure was carried out in the induced animals and in a further group of naive animals. A rechallenge application was then carried out one week after the primary challenge. Scoring was conducted at 24 and 48 h following the primary challenge and the rechallenge phases. Following primary challenge with the test material, as received, the incidence of grade 1 responses in the test group (4 of 20) was compared to that of the naive control group (3 of 10). The incidence and severity of these responses in the test group were essentially comparable to those produced by the naive control group indicating that sensitisation to the test material had not been induced. Following concurrent primary challenge using the vehicle EX-80/90 BO (base oil), as received, the incidence of grade 1 responses in the test group (6 of 20) was compared to that of the naive control group (3 of 10). The incidence and severity of these responses in the test group were essentially comparable to those produced by the naive control group indicating that sensitisation to EX-80/90 BO (base oil) had not been induced.

Finally, in a disregarded study, the skin sensitisation test was conducted using a similar procedure to that described in the current OECD Guideline 406 (Morris, 1994). The read-across substance (CAS No. 50530-43-3) was applied at a volume of 0.3 mL to the backs of 10 male and 10 female Guinea Pigs. The test article was left in contact with the skin for 6 hours. This prodedure was carried out once per week for 3 weeks (induction phase). A primary challenge was then carried out 2 weeks later using the same application procedure as used in the induction phase. This procedure was carried out in the induced animals and in a further group of naive animals. A rechallenge application was then carried out one week after the primary challenge. Scoring was conducted at 24 and 48 h following the primary challenge and the rechallenge phases. The incidence of grade 1 responses in the test group (2 of 20) was compared to that of the naive control group (0 of 10). The incidence and severity of these responses in the test group were greater than those produced by the naive control group indicating that sensitisation to the test material had been induced. The incidence of grade 2 responses in the test group (3 of 20) was compared to that of the naive control group (0 of 10). The incidence and severity of these responses in the test group were again greater than those produced by the naive control group confirming that sensitisation to the test material had been induced.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Skin sensitisation

According to the classification criteria outlined in section 3.4.2.2 (Guidance on the Application of CLP criteria, 2012), if there is evidence in humans that the substance can lead to sensitisation by skin contact in a substantial number of persons, or if there are positive results from an appropriate animal test, the classification as Skin Sensitiser is assigned.

Referring to non human data, significant skin sensitising effects are described if redness occured in ≥ 15 % of the test animals (Buehler occluded patch test). Based on the available key information, this substance does not meet the requirement under EU CLP (Regulation (EC) No. 1272/2008) for classification as a skin sensitiser.The substance is not sensitising.