Skin sensitisation

Skin sensitisation

Administrative data

Purpose flag:

key study

Study result type:

read-across from supporting substance (structural analogue or surrogate)

Study period:

From 2001-11-29 to 2002-04-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

Chlorine dioxide (ClO2) is an unstable gas which must be stabilized with water. After skin contact, the ClO2 in aqueous solution is rapidly reduced in chlorite and chloride (see § 7.1). Therefore, it is considered as relevant to use the structurally close metabolite, sodium chlorite, to evaluate the sensitising potential of ClO2 according to a read-across approach.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report Date:

2002

Materials and methods

Test guideline

Qualifier:

according to

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Remarks:

and EU Method B.6 (Skin Sensitisation)

Deviations:

no

Methods:

in vivo

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Type of study:

Guinea pig maximisation test

Test materials

Identity of test material same as for substance defined in section 1 (if not read-across):

no

Test material identityopen allclose all

Test material identity 1

Identifier:

CAS number

Identity:

7758-19-2

Test material identity 2

Identifier:

EC number

Identity:

231-836-6

Test material identity 3

Identifier:

IUPAC name

Identity:

sodium chlorite

Details on test material:

- Test material: Sodium chlorite (31% solution)
- Lot/Batch No: 6624 (Atofina)
- Physical state: colorless liquid
- Purity: 31.12 % 
- Preparation of test substance for application:
a) for induction: In 0.9% NaCl
b) for challenge: In 0.9% NaCl
- Stability under test conditions: no data
- Storage condition of test material: at room temperature and protected from light

Test animals

Species:

guinea pig

Strain:

Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Saint-Aubin-les-Elbeuf, France.
- Age at study initiation: 1 – 3 months old
- Weight at study initiation: Mean body weight males: 380 ± 31 g; females: 355 ± 13 g.
- Housing: housed individually in polycarbonate cages with stainless steel lid (48 cm x 27 cm x 20 cm)
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days before the beginning of the study.

-other: sex: Male and female (nulliparous and non-pregnant)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22° ± 2°C
- Humidity (%): 30 to 70%
- Air changes (per hr): approximately 12 cycles/hour of filtered, non-recycled air
- Photoperiod (hrs dark / hrs light): 12h dark / 12h light

IN-LIFE DATES: no data

Test system

Traditional sensitisation test

Route of induction exposure:

intradermal and epicutaneous

Route of challenge exposure:

epicutaneous, occlusive

Vehicle:

water

Concentration:

Concentrations used for induction: 
- intradermal injections (day 1): 0.031 % sodium chlorite (i.e. a 0.1 % solution of a 31 % solution of sodium chlorite)
- topical application (day 8): 1.55% sodium chlorite

Concentrations used for challenge: 
- 0.31 % sodium chlorite (i.e. a 1 % solution of a 31 % solution of sodium chlorite)

No. of animals per dose:

Thirty guinea pigs were allocated to two groups: a control group of five males and five females and a treated group of ten males and ten females.

Details on study design (Traditional tests):

RANGE-FINDING TESTS:
A preliminary test was conducted in order to determine the concentrations to be tested in the main study.
By intradermal route (tested concentrations: 5%, 1% and 0.1% (w/w), i.e. 1.55%, 0.31% and 0.031% sodium chlorite):
- 24 hours before treatment, the dorsal region of the animals was clipped,
- intradermal injections of the dosage form preparations (0.1 mL) were performed in the interscapular region,
- cutaneous reactions were evaluated approximately 24, 48 hours and 6 days after the injections.
By cutaneous route (tested concentrations: 100%, 50%, 10%, 5%, 1% and 0.5% (w/w), i.e. 31%, 15.5%, 3.1%, 1.55%, 0.31% and 0.155% sodium chlorite):
- 24 hours before treatment, both flanks of the animals were clipped and shaved,
- the filter paper of a chamber (Finn Chamber) was fully-loaded with a dosage form preparation. The chamber was then applied to the clipped area of the skin (one concentration per flank). The chamber was held in place by means of an occlusive dressing for 24 hours,
- cutaneous reactions were evaluated 24 and 48 hours after removal of the dressings.

In order to respect the criteria for the selection of concentrations (the concentration should be well-tolerated systemically and locally, intradermal injections should cause moderate irritant effect but no necrosis or ulceration of the skin), concentration chosen for the main study was 0.1% (w/w) (i.e. 0.031% sodium chlorite).
In order to respect the criteria for the selection of concentrations (the concentrations should be well-tolerated systemically and locally, cutaneous application for the induction should cause at most weak or moderate skin reactions or be the maximal practicable concentration, cutaneous application for the challenge phase should be the highest concentration which does not cause irritant effect), concentration chosen for the topical application of the induction phase (day 8) was 5% (w/w) (i.e. 1.55% sodium chlorite). For the challenge application (day 22), it was 1% (w/w) (i.e. 0.31% sodium chlorite).

MAIN STUDY:

- INDUCTION SCHEDULE:
Intradermal route:
Day 1: six injections were made into the dermis of a 4 cm x 2 cm clipped interscapular area using a needle (0.50 x 16 mm diameter). Three injections of 0.1 mL were made into each side of this interscapsular region.
Cutaneous route:
As the test item was shown to be irritant during the preliminary test, a topical application with sodium lauryl sulphate was not necessary on day 7.
Day 8: a pad of filter paper (~8 cm2) was fully loaded with the test item at the concentration of 5% (w/w) (i.e. 1.55% sodium chlorite) and was then applied to the interscapular region of the animal of the treated group. The pad was held in place for 48 h.

- CHALLENGE SCHEDULE
On day 22, the animals received an application of the test item and vehicle. The filter paper of a chamber (Finn Chamber®) was fully loaded with the test item at the concentration of 1% (w/w) (i.e. 0.31% sodium chlorite) and was then applied to the clipped area of the skin of the posterior right flank. The vehicle was applied to the posterior left flank. The chambers were held in contact with the skin for 24 h by means of an adhesive allergenic waterproof plaster.

Challenge controls:

5 animals/sex were used as control animals and were treated with water.

Positive control substance(s):

yes

Remarks:

Mercaptobenzothiazole (as a separate study)

LLNA

Concentration:

Not applicable

No. of animals per dose:

Not applicable

Details on study design (LLNA):

Not applicable

Statistics:

Not applicable

Results and discussion

Positive control results:

No data

Traditional sensitisation test

Results of test (except LLNA)open allclose all

Results of test (except LLNA) 1

Reading:

1st reading

Hours after challenge:

24

Group:

test group

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No cutaneous reactions were observed.

Results of test (except LLNA) 2

Reading:

2nd reading

Hours after challenge:

48

Group:

test group

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No cutaneous reactions were observed.

Results of test (except LLNA) 3

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Results of test (except LLNA) 4

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Results of test (except LLNA) 5

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

No. with + reactions:

10

Total no. in group:

10

Results of test (except LLNA) 6

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

No. with + reactions:

10

Total no. in group:

10

LLNA

Disintegrations per minute (DPM):

Not applicable

Any other information on results incl. tables:

Table 7.4.1/1: Detailed information including induction/challenge/scoring schedule for skin sensitisation test Guinea pig maximisation test (GPMT)
Inductions	GPMT			Observations/Remarks
	day of treatment		application
Induction A	0		intradermal
Induction B	0		topical
challenge	22		topical
scoring 1	23			No reactions were observed
scoring 2	24			No reactions were observed
Table 7.4.1/2: Result of skin sensitisation test
		Number of animals with signs of allergic reactions / number of animals in group
		Negative control			Test group	Positive control
scored after 24h		0/10			0/20	10/10
scored after 48h		0/10			0/20	10/10

Applicant's summary and conclusion

Conclusions:

No delayed contact hypersensitivity in guinea pigs was observed.

Executive summary:

In a skin sensitisation study, Sodium chlorite 31% solution at the concentration of 1% was administered to guinea pigs by intradermal injections. This study was performed according to OECD 406 and in compliance with the Good Laboratory Practice.

It is considered as relevant to use the structurally close metabolite, sodium chlorite, to evaluate the sensitising potential of the chlorine dioxide according to a read-across approach. In fact, the chlorine dioxide (ClO2) is an unstable gas which must be stabilized with water. After skin contact, the ClO2 in solution is rapidly reduced in chlorite and chloride (see § 7.1).

Intradermal injections of Sodium chlorite were performed on day 1 at the concentration of 0.1% (w/w) in 0.9% NaCl, concentration which causes moderate irritant effect but no necrosis or ulceration of the skin. Topical application of Sodium chlorite was performed on day 8 at the concentration of 5% (w/w) in 0.9% NaCl, concentration which causes weak skin reactions.

For all groups of animals (negative and positive control groups and test substance group, challenge was performed on day 22 by a topical application of Sodium chlorite at the concentration of 1% (w/w) in 0.9% NaCl, i.e. the highest concentration which does not cause irritant effect.

The animals were observed at least once a day during the study in order to check for clinical signs and mortality

No clinical signs and no death were noted during the study. No cutaneous reactions (erythema or edema) were observed after the challenge application.

The Sodium chlorite 31% solution at the concentration of 1% (i.e. 0.31% sodium chlorite) does not induce delayed contact hypersensitivity in guinea pigs. Therefore, at concentrations where skin irritation/corrosion is not observed, the chlorine dioxide is not considered as a skin sensitiser according to a read-across approach with the sodium chlorite.

Under the test conditions, the chlorine dioxide is not classified as skin sensitiser according to the criteria of the Annex VI to the Regulation (EC) n° 1272/2008.

This skin sensitisation study is classified as acceptable. It does satisfy with the guidelines requirements for a skin sensitisation study (OECD 406) in the guinea pigs.

Interpretation of results:

not sensitising