3-(triethoxysilyl)propiononitrile

Endpoint summary

Description of key information

In a reliable study performed in accordance with OECD Test Guideline 406 (guinea pig maximisation test) with minor deviations, and in compliance with GLP, 3-(triethoxysilyl)propiononitrile is not considered to be a skin sensitiser (Harlan Laboratories, 2010)

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:

2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

A re-challenge is done after 16 not 7 days. Testing additional animals is strongly recommended when fewer than 20 test and 10 control guinea pigs have been used and it is not posible to conclude that the test substance is a sensitiser.

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

An LLNA study was not performed because the test method is not considered to be suitable for substances that contain silicon. Please refer to the attached document for further details.

Species:

guinea pig

Strain:

Dunkin-Hartley

Remarks:

Albino CRL:(HA)

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland GmbH, Stolzenseeweg 32-36, 88353 Kisslegg / Germany
- Number of Animals for Main Study /Pretest:15 males / 3 males
- Age at Pretest Start / Beginning of Acclimatization Period: 5-6 weeks
- Body Weight at Pretest Start: Pretest groups: 680 -715 g
- Body Weight at Beginning of Acclimation Period: Test and control group: 604 - 748 g
- Housing: Individually in Makrolon type-4 cages with standard softwood bedding (‘Lignocel’ J. Rettenmaier&Söhne GmbH&CoKG, 73494 Rosenberg / Germany, imported by Provimi Kliba AG, 4303 Kaiseraugst /Switzerland).
- Diet: Pelleted standard Provimi Kliba 3418 guinea pig breeding / maintenance diet batch nos. 44/09 and 52/09, containing Vitamin C (Provimi Kliba AG, 4303 Kaiseraugst / Switzerland), ad libitum. Results of analyses for contaminants are archived at Harlan Laboratories Ltd.
- Water: Community tap water from Füllinsdorf, ad libitum. Results of bacteriological, chemical and contaminant analyses are archived at Harlan Laboratories Ltd.
- Identification: By unique cage number and corresponding individual ear tag.
- Randomization: Selected by hand at time of delivery. No computer generated randomization program.
- Acclimation period: Twelve days for the control and test group under laboratory conditions after health examination. No acclimation period for the animals of the pretest. Only animals without any visible signs of illness were used for the study. A certificate of health was provided by the animal supplier at the animal delivery and included in the raw data.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Air-conditioned with ranges for room temperature 22 ± 3 °C
- Humidity (%): 30-70%
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12 hours light/ 12 hours dark
- Room temperature and humidity were monitored continuously and values outside of these ranges occasionally occurred, usually following room cleaning. These transient variations are considered not to have any influence on the study and, therefore, these data are not reported but are retained at Harlan Laboratories. Music was played during the daytime light period.

Route:

intradermal and epicutaneous

Vehicle:

other: Diethylene glycol dimethyl ether (glyme)

Concentration / amount:

Intradermal induction : 0.1 mL of 50% test substance in vehicle and in FCA/physiological saline
Epidermal induction: 0.3 mL of 100% test substance in vehicle

Day(s)/duration:

Day 1 for intradermal induction, Day 8 for epidermal induction/48h of application for the closed patch

Adequacy of induction:

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

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: Diethylene glycol dimethyl ether

Concentration / amount:

0.2 mL of the test item at 25% in vehicle (and vehicle alone)

Day(s)/duration:

Day 22/ 24h of application

Adequacy of challenge:

highest non-irritant concentration

No.:

#2

Route:

epicutaneous, occlusive

Vehicle:

other: Diethylene glycol dimethyl ether

Concentration / amount:

0.2 mL of the test item at 25% in vehicle (and vehicle alone)

Day(s)/duration:

Day 38/ 24h of application

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

15 (10 test and 5 control) male albino Dunkin Hartley guinea pigs

Details on study design:

The dose levels of 3-(triethoxysilyl)propiononitrile used in the main study were based on results from intradermal and epidermal pretests.
The intradermal induction of sensitization in the test group was performed in the nuchal region with a 50% dilution of the test item in diglyme and in an emulsion of Freund's Complete Adjuvant (FCA)/physiological saline. The epidermal induction of sensitization was conducted for 48 hours under occlusion with the test item at 100% (undiluted) one week after the intradermal induction. The animals of the control group were intradermally induced with diglyme and FCA/physiological saline and epidermally induced with diglyme under occlusion. Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test item at 25% in diglyme and diglyme alone under occlusive dressing. Sixteen days after the first challenge a second challenge was performed in the same way as the previous challenge using the test group only and the test item at 25% in diglyme applied on a naive skin site.

Challenge controls:

The animals of the control group were intradermally induced with diglyme and FCA/physiological saline and epidermally induced with diglyme under occlusion.

Positive control substance(s):

yes

Remarks:

ALPHA-HEXYLCINNAMALDEHYDE at 1% (w/w) in PEG 300

Positive control results:

The sensitivity and reliability of the experimental technique employed was assessed by use of ALPHA-HEXYLCINNAMALDEHYDE which is recommended by the OECD 406 Guidelines and is known to have moderate skin sensitization properties in the guinea pig strain. The results from the most recent test run (Harlan Laboratories Study C50652, performed from 27-May-2009 to 20-Jul-2009) ) follow:
One out of 10 test animals showed skin reactions after the first challenge treatment with ALPHA-HEXYLCINNAMALDEHYDE at 1% (w/w) in PEG 300. No skin effect was observed in the control group. Eighty to ninety percent of the test animals showed discrete/patchy erythema at the 24- or 48-hour reading
after the second challenge treatment with ALPHA-HEXYLCINNAMALDEHYDE at 3% (w/v) in PEG 300. No skin effect was observed in the control group.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

25%

No. with + reactions:

1

Total no. in group:

5

Clinical observations:

Grade 2

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

0

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

25%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

25%

No. with + reactions:

5

Total no. in group:

10

Clinical observations:

Grade 1 in 3 animals, Grade 2 in 2 animals

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

25%

No. with + reactions:

4

Total no. in group:

10

Clinical observations:

Grade 1 in all animals

Remarks on result:

positive indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

0

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

25%

No. with + reactions:

1

Total no. in group:

10

Clinical observations:

Grade 1

Remarks on result:

no indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

0

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

25%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

24

Group:

positive control

Dose level:

3%

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

Grade 1

Remarks on result:

positive indication of skin sensitisation

Reading:

rechallenge

Hours after challenge:

48

Group:

positive control

Dose level:

3%

No. with + reactions:

9

Total no. in group:

10

Clinical observations:

Grade 1

Remarks on result:

positive indication of skin sensitisation

Table 1: Skin Reactions after the First Challenge Procedure

	After 24 hours Positive/Total % Positive of Total	After 48 hours Positive/Total % Positive of Total
Control Group 3-(TRIETHOXYSILYL) PROPIONONITRILE, 25% in diglyme (left flank)     Diglyme only	1/5 20       0/5 0	0/5 0       0/5 0
Test Group 3-(TRIETHOXYSILYL)PROPIONONITRILE, 25% in diglyme (left flank)   Diglyme only	5/10 50     0/10 0	4/10 40     0/10 0

 Table 2: Skin Reactions after the Second Challenge Procedure

	After 24 hours Positive/Total % Positive of Total	After 48 hours Positive/Total % Positive of Total
Test Group 3-(TRIETHOXYSILYL)PROPIONONITRILE, 25% in diglyme (left flank)   Diglyme only	1/10 10     0/10 0	0/10 0     0/10 0

Interpretation of results:

not sensitising

Conclusions:

In a guinea pig maximisation test study with adjuvant, conducted according to OECD Test Guideline 406 and in compliance with GLP (with minor deviations), 3-(triethoxysilyl)propiononitrile is not considered to be a skin sensitiser.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In the key skin sensitisation study available for 3-(triethoxysilyl)propiononitrile, conducted according to OECD Test Guideline 406 and in compliance with GLP, no toxic signs were evident in the guinea pigs of the control or test group. No deaths occurred.

The initial challenge indicated that 50% of the test animals had been sensitized at the 24-hour reading with the test item applied at 25% in diglyme while no skin reaction was observed in the same group treated with diglyme alone and in the control group treated identically to the test group during the first challenge procedure. The nature of the reactions at the 48 hours (fading or fully disappearing in three cases) suggests they may in fact be due to skin irritation.

The second challenge performed in the test group under identical conditions on a new test area showed that the responses were not reproducible in the guinea pigs reacting in the first challenge, even in the two strongest reacting animals (with grade 2): all test animals were devoid of any skin reactions, except one animal presenting a grade 1 at the 24-hour reading (no reaction anymore at the 48 hours) as it was already observed in the same animal in the first challenge.

Based on the results of the first and second challenge, it can be concluded that the skin reactions observed in the first challenge were of non-specific irritant and toxic origin and consequently irreproducible by rechallenging the test animals. This consideration is supported by the general opinion that even weak first challenge reactions which are truly of allergic origin can be reproduced, and that rechallenge normally acts as “booster” up-regulating both the frequency and intensity of elicited skin reaction in sensitized animals.

Therefore the test substance 3-(triethoxysilyl)propiononitrile is not considered to be a skin sensitiser under the conditions of the test.

Justification for classification or non-classification

Based on the available in vivo skin sensitisation study, 3-(triethoxysilyl)propiononitrile does not meet the criteria for classification as a skin sensitiser according to Regulation (EC) No 1272/2008. There are no data to suggest that classification as a respiratory sensitiser is required.