2-ethylhexyl mercaptoacetate

Endpoint summary

Description of key information

EHTG was tested in an OECD guideline 406 guinea pig maximization test (Clouzeau, 1994). EHTG concentrations for induction were: 25% EHTG in paraffin oil (intradermal injections; day 1); undiluted EHTG (topical application covered with occlusive dressing; day 8). For the challenge, undiluted EHTG was applied topically on day 22 and covered with an occlusive dressing. After the challenge application of EHTG, no cutaneous reactions were observed in the animals of the control group. A positive response characterized by a well-defined erythema was observed on the right flank of 10/20 and 5/20 treated animals after 24 and 48 hours, respectively. No oedema was noted. The reactions (very slight erythema) noted in 8/20 and 11/20 animals after 24 and 48 hours, respectively, were considered to be inconclusive evidence of sensitization. According to the maximization method of Magnusson & Kligman, EHTG induced positive skin sensitization cutaneous reactions in 10 out of 20 (50%) guinea pigs.

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:

From 10 September to 4 October 1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

Study performed before the implementation of the REACH regulation.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: centre d'elevage Lebeau, France
- Age at study initiation: not reported
- Weight at study initiation: mean: 430 +/- 22 g for males; 429 +/- 37 g for femlaes
- Housing: individually in polycarbonate cages (48 x 27 x 20 cm)
- Diet (e.g. ad libitum): "Guinea-pigs sustenance reference 106 diet" ad libitum
- Water (e.g. ad libitum): filtered by a Millipore membrane, ad libitum
- Acclimation period: at least 5 days before the beginning of the study


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 50 +/- 20
- Air changes (per hr): air filtered and non-recycled
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 10 September 1993 To: 4 October 1993

Route:

intradermal

Vehicle:

paraffin oil

Concentration / amount:

25%

Day(s)/duration:

Day 1

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Day(s)/duration:

D7

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Day(s)/duration:

D22

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

Control group: 10 animals (5 males and 5 females)
Treated group: 20 animals (10 males and 10 females)

Details on study design:

RANGE FINDING TESTS: conducted to define the concentrations to be tested in the main study.

Intradermal exposure:
24 hours before treatment: dorsal region clipped.
Intradermal administration of 0.1 mL of the test substance (TS) at increasing concentrations.
Evaluation of the potential cutaneous reactions 24 and 48 hours after injection.

Epicutaneous exposure:
24 hours before treatment: dorsal region clipped.
0.5 mL of each concentration applied to a gauze patch of approximately 4 cm2 for 24 hours by occlusive dressing (2 concentrations per animal).
Evaluation of the potential cutaneous reactions 24 hours after patch removal.


MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 1 intradermal, 1 epicutaneous
- Exposure period: epicutaneous: 48 hours
- Test groups:
Intradermal exposure
Three injections of 0.1 mL were injected into each side of the animal as follows:
. Freund's complete adjuvant (FCA) diluted to 50% with a NaCl solution
. TS at 25% in vehicle
. A mixture 50/50 (v/v) FCA diluted to 50% with a NaCl solution, and TS at 25% in vehicle

Epicutaneous exposure
Application of 0.5 mL of TS applied to the scapular region and held in place for 48 hours using adhesive dressing abd plaster. No residual TS was observed at removal of the dressing.

- Control group:
Intradermal exposure
Three injections of 0.1 mL were injected into each side of the animal as follows:
. Freund's complete adjuvant (FCA) diluted to 50% with a NaCl solution
. vehicle
. A mixture 50/50 (v/v) FCA diluted to 50% with a NaCl solution, and vehicle

Epicutaneous exposure
Application of 0.5 mL of vehicle applied to the scapular region and held in place for 48 hours using adhesive dressing and plaster.

- Site:
Intradermal exposure
6 injections in the clipped area (4 x 2 cm) in the scapular region

Epicutaneous exposure
On day 7, the same scapular area was clipped. As no irritation was elicited during the preliminary test, animals were treated with 0.5 mL of sodium
lauryl sulfate (10%) in vaseline to induce local irritations.

- Frequency of applications:
One intradermal injection and one epicutaneous application 8 days after on the same site.

- Duration:
Epicutaneous exposure: 48 hours


B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 22
- Exposure period: 24 hours
- Test groups:
0.5 mL of the TS on the posterior right flank (occlusive epicutaneous application)
0.5 mL of the vehicle on the posterior left flank (occlusive epicutaneous application)
- Control group:
Same treatment as test group
- Site: posterior right and left flanks
- Evaluation (hr after challenge): 24 and 48 hours after removal of the dressing

Challenge controls:

Vehicle was applied at the challenge application on the posterior left flank of both test and control groups of animals.

Positive control substance(s):

yes

Remarks:

dinitro 2,4 chlorobenzene

Positive control results:

The positive control (dinitro 2,4 chlorobenzene) at a concentration of 0.5% induced positive skin sensitization reactions in 100% of the Guinea-pigs. This test was conducted on July 1993.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0.5 ml undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No abnormalities

Reading:

1st reading

Hours after challenge:

48

Group:

negative control

Dose level:

0.5 ml undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No abnormalities

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.5 ml undiluted

No. with + reactions:

10

Total no. in group:

20

Clinical observations:

No abnormalities

Remarks on result:

positive indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.5 ml undiluted

No. with + reactions:

5

Total no. in group:

20

Clinical observations:

No abnormalities

Remarks on result:

positive indication of skin sensitisation

End of the induction period: On day 10, after removal of the dressing, slight irritation in the control and treated groups were observed at the intradermal injection sites. Challenge application: Table 1: Table of frequency of cutaneous observation in control and treated groups:

Group	Sex	Erythema score	Scoring
			24 hours		48 hours
			Left flank	Right flank	Left flank	Right flank
Control	Male	0	5/5	5/5	5/5	5/5
Treated	Male	0	10/10	-	10/10	1/10
		1	-	4/10	-	6/10
		2	-	6/10	-	3/10
Control	Female	0	5/5	5/5	5/5	5/5
Treated	Female	0	10/10	2/10	10/10	3/10
		1	-	4/10	-	5/10
		2	-	4/10	-	2/10

Interpretation of results:

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

Conclusions:

In the treated group, following cutaneous reactions were noted:
- very slight erythema in 8/20 animals after 24 hours and in 11/20 animals afer 48 hours,
- well-defined erythema in 10/20 animals after 24 hours and in 5/20 animals afer 48 hours.

Executive summary:

EHTG was tested in an OECD guideline 406 guinea pig maximization test. EHTG concentrations for induction were: 25% EHTG in paraffin oil (intradermal injections; day 1); undiluted EHTG (topical application covered with occlusive dressing; day 8). For the challenge, undiluted EHTG was applied topically on day 22 and covered with an occlusive dressing. After the challenge application of EHTG, no cutaneous reactions were observed in the animals of the control group. A positive response characterised by a well defined erythema was observed on the right flank of 10/20 and 5/20 treated animals after 24 and 48 hours, respectively. No oedema was noted. The reactions (very slight erythema) noted in 8/20 and 11/20 animals after 24 and 48 hours, respectively, were considered to be inconclusive evidence of sensitization. According to the maximization method of Magnusson & Kligman, EHTG induced positive skin sensitization cutaneous reactions in 10 out of 20 (50%) guinea pigs. 

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

According to REGULATION (EC) No 1272/2008 of 16 December 2008 and the available skin sensitization data, 2-ethylhexyl mercaptoacetate should be classified as skin sensitiser 1B.