Propanoic acid, 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-

Endpoint summary

Description of key information

The substance caused skin sensitization in guinea pigs as determined in a GLP-compliant study according to OECD testing guideline 406. No data on respiratory sensitization are available.

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:

9-NOV-1999 - 20-DEC-1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

(1993)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The study was conducted in 2000, when the GPMT was an international accepted and recommended method to assess sensitizing potential.

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Stability under test conditions: Stable in PEG 400 and in a 1:1 (v/v) mixture of FCA/physiological saline for at least 2 h

Species:

guinea pig

Strain:

other: Ibm: GOHI; SPF-quality

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: RCC Ltd. Biotechnology & Animal Breeding Division, CH-4414 Füllinsdorf / Switzerland.
- Age at study initiation: 5 - 7 weeks.
- Weight at study initiation: 337 - 371 g.
- Housing: individually in Makrolon type-4cages.
- Diet: pelleted standard Nafag Ecosan 845 25W4, guinea pig breeding/maintenance diet (containing Vitamin C), ad libitum.
- Water: tap water, ad libitum.
- Acclimation period: 1 week.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 40 - 70
- Air changes (per hr): 10 - 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Route:

intradermal

Vehicle:

polyethylene glycol

Concentration / amount:

50 %

Day(s)/duration:

day 0

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

0.3 mL; 100 %

Day(s)/duration:

day 8 / 48 h

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

polyethylene glycol

Concentration / amount:

50 %

Day(s)/duration:

day 21 / 24 h

No. of animals per dose:

Pretest: 3 animals.
Main test: 10 animals in treatment group, 5 animals in control group.

Details on study design:

RANGE FINDING TESTS:
Pretest:
Intradermal Injection:
Four intradermal injections (0.1 mL/site) of a 1:1 mixture of FCA/physiological saline were made in the shaved neck of one guinea pig. One week later intradermal injection (0.1 mL/site) was made into the clipped flank of the same guinea pig at concentrations of 100 %, 75 % and 50 % of the test article in PEG 400. Dermal reactions were assessed 24 h later. Based on the results a concentration of 50 % was selected for intradermal induction in the main study.
Epidermal Application:
Four intradermal injections (0.1 ml/site) of a 1:1 mixture of FCA/physiological saline were made in the shaved neck of two guinea pigs. One week later, 4 patches were saturated with the test article at concentrations of 100 %, 75 %, 50 % and 25 % in PEG 400, respectively. The patches were applied to the clipped and shaved flanks of each of the two animals under occlusive conditions. The exposure period was 24 h. After removal of the patches the skin was examined for signs of irritation.
According to results of the pretest for intradermal injection (induction) in the main study a concentration of 50 % of test article in vehicle was selected. Undiluted (100 %) test article was selected for epidermal induction, and 50 % in vehicle for epidermal challenge.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2;
Intradermal: three pairs of intradermal injections (1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline, the test article, at 50 % in PEG 400 and the test article at 50 % in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline; 0.1 mL/site)
Epidermal: undiluted test article one week after intradermal injections.
- Exposure period: epidermal application was performed for 48 h.
- Test groups: 10 males.
- Control group: 5 males.
- Site: dorsal skin from the scapular region.

B. CHALLENGE EXPOSURE (TWO WEEKS AFTER INDUCTION)
- No. of exposures: 1.
- Day(s) of challenge: 1.
- Exposure period: 24 h.
- Test groups: 10 males.
- Control group: 5 males.
- Site: flank.
- Concentrations: 50 % test article in vehicle.
- Evaluation (hr after challenge): approximately 25 and 48 hours after challenge.

Challenge controls:

PEG 400

Positive control substance(s):

yes

Remarks:

2-Mercaptobenzothiazole (independently performed, report attached)

Positive control results:

Validation of sensitivity of the Maximization-Test was performed from 1998-12-01 to 1999-01-08 (RCC Project 903407). In accordance to OECD 406, 2-Mercaptobenzothiazole was selected as a positive control. The intradermal induction of sensitization was performed with a 5 % dilution of the test article in mineral oil and in an emulsion of FCA/physiological saline. The epidermal induction of sensitization was conducted under occlusion with the test article at 50 % in mineral oil. Two weeks after the epidermal induction application the challenge was completed by epidermal application of the test article at 10 % in mineral oil under occlusive dressing. The animals of the control group were induced with mineral oil and FCA/physiological saline and challenged similarly to those of the test group. Cutaneous reactions, i.e. erythema and eschar, as well as edema formation were evaluated at 24 and 48 hours after removal of the dressing.
90 % (at the 24-hour reading) and 100 % (at the 48-hour reading) of the animals of the test group were observed with very slight to moderate/severe erythematous reactions after treatment with a non-irritant test article concentration of 10 % in mineral oil. No skin reactions were observed in the control group.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0 %

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no skin irritations were observed

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50 %

No. with + reactions:

7

Total no. in group:

10

Clinical observations:

positive reactions consisted of discrete/patchy to intense erythema and swelling of the skin

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

0 %

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no skin irritations were observed

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50 %

No. with + reactions:

7

Total no. in group:

10

Clinical observations:

positive reactions consisted of discrete/patchy to moderate/confluent erythema

Details on skin reactions after the challenge procedure

Reading time point	24 h			48 h
	positive	total	% positive of total	positive	total	% positive total
Control group (induced without test article)
challenged with the test item 50 % in PEG 400	0	5	0	0	5	0
challenged with PEG 400	0	5	0	0	5	0
Test group (induced with test article)
challenged with the test item 50 % in PEG 400	7	10	70	7	10	70
challenged with PEG 400	0	10	0	0	10	0

Remark:

No toxic symptoms and no mortality were observed in the animals.

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

In order to assess the cutaneous allergenic potential, a Maximization-Test was performed in 15 (10 test and 5 control) male albino guinea pigs, in accordance with OECD Guideline No. 406 and the Directive 96/54/EEC, B.6. The intradermal induction of sensitisation in the test group was performed in the nuchal region with a 50 % dilution of the test article in PEG 400 and in an emulsion of Freund's Complete Adjuvant (FCA) / physiological saline. The epidermal induction of sensitisation was conducted for 48 hours under occlusion with the undiluted test article one week after the intradermal induction. The animals of the control group were intradermally induced with PEG 400 and FCA/physiological saline and epidermally induced with PEG 400 under occlusion. Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test article at 50 % in PEG 400 and PEG 400 alone under occlusive dressing. Cutaneous reactions were evaluated at 24 and 48 hours after removal of the dressing. Seven out of 10 test animals showed discrete/patchy to intense erythema and swelling (at the 24-hour reading) and discrete/patchy to moderate/confluent erythema (at the 48-hour reading) after the challenge treatment at 50 % (w/w) in PEG 400. No skin effect was observed in the control group.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is considered to be classified for skin sensitization in category 1B under Regulation (EC) No. 1272/2008.