Hexaammonium wolframate

Endpoint summary

Description of key information

No skin sensitisation data of sufficient quality are available for ammonium metatungstate (target substance). However, data are available on the ammonium paratungstate, sodium metatungstate and sodium tungstate (source substances), which were used in the weight-of-evidence for read-across approach. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.

None of the read-across substances produced evidence of skin sensitisation (delayed contact hypersensitivity) in any of the test animals in two Guinea Pig Maximisation Tests (GPMT) performed according to OECD Guideline 406. Based on lack of skin sensitisation reported in assays performed with the read-across substances, ammonium metatungstate is not expected to be a skin sensitiser.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

1998-03-24 to 1998-04-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Well documented, scientifically sound study that was conducted in accordance to GLP and OECD guideline 406 with no deviation to the protocol.

Justification for type of information:

1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Ammonium paratungstate
Target: Ammonium metatungstate
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR

Reason / purpose for cross-reference:

read-across: supporting information

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:

1999 guinea pig sensitisation study was available of good quality. Therefore, there is no need to conduct a LLNA study as the guinea pig sensitisation study scientifically fulfills the endpoint. The OECD 406 method provides sensitisation information likely to arise from exposure to test substance via intradermical injection and/or epidermical application to guinea pigs. The guinea pig sensitisation test detects chemicals with moderate to strong sensitisation potential, as well as those with relatively weak sensitisation potential. In such methods activity is measured as a function of challenge-induced dermal hypersensitivity reactions elicited in test animals compared with controls. In addition, guinea pigs have been the animal of choice for predictive sensitisation tests for several decades (way before the LLNA became the test of choice).
The existing guinea pig data submitted here is of good quality as clear results are presented in this robust summary and test methodology followed OECD 406 guidelines, and conducted under GLP. This study it is considered acceptable according to page 266 in ECHA's Chapter r7a on Guidance on Information Requirements and Chemical Safety Assessment.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: D. Hall, Newchurch, Staffs, UK.
- Age at study initiation: 4 to 7 weeks
- Weight at study initiation: 349 to 424 g
- Housing: Groups of 5 in suspended metal cages with wire mesh floors.
- Diet (e.g. ad libitum): Harlan Teklad 9600 FD2 SQC ad libitum. Hay was given thrice weekly.
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.5 to 23.5
- Humidity (%): 40 to 59
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12 artificial light (0700 - 1900)

IN-LIFE DATES: From: 1998-03-24 To: 1998-04-24

Route:

intradermal and epicutaneous

Vehicle:

other: Alembicol D

Concentration / amount:

-Induction Intradermal: 10% w/v in Alembicol D.
-Induction topical application: 75% w/v in Alembicol D.
-Topical challenge: 75 and 37.5% w/v in Alembicol D.

Route:

epicutaneous, occlusive

Vehicle:

other: Alembicol D

Concentration / amount:

-Induction Intradermal: 10% w/v in Alembicol D.
-Induction topical application: 75% w/v in Alembicol D.
-Topical challenge: 75 and 37.5% w/v in Alembicol D.

No. of animals per dose:

ten test animals and 5 control

Details on study design:

RANGE FINDING TESTS: From preliminary investigations 75% w/v in Alembicol D was the maximum practical concentration and did not give rise to irritating effects.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: single
- Exposure period: 48 hrs
- Test groups: 2
- Control group: 1
- Site: interscapular area
- Frequency of applications: Once
- Concentrations: Intradermal - 10% w/v in Alembicol D
Topical - 75% w/v in Alembicol D

INDUCTION INTRADERMAL INJECTIONS:
A 40 x 60 mm area of dorsal skin on the scapular region of the test animal was clipped free of hair. Three pairs of intradermal injections were made into a 20 x 40 mm area within the clipped area. Injectables for the test animals were prepared as follows: 1) Freud's complete adjuvant was diluted with an equal volume of water for irrigation. 2) Ammonium paratungstate, 10% w/v Alembicol D. 3) Ammonium paratungstate 10% w/v in a 50:50 mixtureof Freund's complete adjuvant and Alembicol D.

INDUCTION TOPICAL APPLICATION:
Six day after the injections, the same 40 x 60 mm intrascapular area was clipped and shaved free of hair and the site was pre-treated by gentle rubbing with 0.5 mL per site of 10% w/v sodium lauryl sulphate in petroleum. Twenty-four hours later a 20 x 40 mm patch of Whatman No. 3 paper was saturated with approximately 0.4 mL of ammonium paratungstate, 75% w/v in Alembicol D. The patch was placed on the skin of test animals and covered by a length of impermeable plastic adhesive tape. This in turn was firmly secured by elastic adhesive bandage wound round the torso of the animal and fixed with "Sleek" impervious plastic adhesive tape. The dressing was left in place for 48 hours.

B. CHALLENGE EXPOSURE
- No. of exposures: Single
- Day(s) of challenge: 2 wks after the topical induction application
- Exposure period: 24 hrs
- Test groups: One group of 10 animals
- Control group: One grooup of 5 animals
- Site: Left flank of each animal
- Concentrations: 0.2 mL of ammonium paratungstate, 75% w/v in Alembicol D to an anterior site on the flank and 37.5% w/v in Alembicol D to a posterior site.
- Evaluation (hr after challenge): 24 and 48 hrs

INDUCTION CONTROLS
During the induction phase, the control animals were treated similarly to the test animals with the exception that the test substance was omitted from the intradermal injections and topical application.
CHALLENGE:
The control and test animals were challenged topically two weeks after the topical induction application using ammonium paratungstate, 75 and 37.5% w/v Alembicol D. Hair was removed by clipping and then shaving from an area on the left flank of each test animal. A 20 x 20 mm patch of Whatman No. 3 paper was saturated with approximately 0.2 mL of ammonium paratungstate, 75% w/v in Alembicol D was applied to an anterior site on the flank.Ammonium paratungstate, 37.5% w/v Alembicol D was applied in a similar manner to a posterior site. The patches were sealed to the flank for 24 hours under strips of "Blenderm" covered by "Elastoplast" wound round the trunk and secured with "Sleek".

Challenge controls:

Animals were challenged topically two weeks after the topical induction application using ammonium paratungstate, 75 and 37.5% w/v Alembicol D. Hair was removed by clipping and then shaving from an area on the left flank of each test animal. A 20 x 20 mm patch of Whatman No. 3 paper was saturated with approximately 0.2 mL of ammonium paratungstate, 75% w/v in Alembicol D was applied to an anterior site on the flank. Ammonium paratungstate, 37.5% w/v in Alembicol D was applied in a similar manner to a posterior site. The patches were sealed to the flank for 24 hours under strips of "Blenderm" covered by "Elastoplast" wound round the trunk and secured with "Sleek".

Positive control substance(s):

yes

Remarks:

Hexy cinnamic aldehyde (HCA), Benzocaine and 2-mercaptobenzothiazole (MBT)

Positive control results:

In this study HCA produced evidence of skin sensitization (delayed contact hypersensitivity) in all of the ten animals, thus confirming the sensitivity and reliability of the experimental technique.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

approximately 0.2 mL Alembicol

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

No dermal reactions seen in any of the control animals

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

approximately 0.2 mL Alembicol

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

No dermal reactions seen in any of the control animals

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.1 ml of 10% APT (w/v) in Alembicol D

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No dermal reactions seen in any of the test animals

Remarks on result:

no indication of skin sensitisation

Remarks:

Challenge with APT, 75% w/v in Alembicol

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.1 ml of 10% APT (w/v) in Alembicol D

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No dermal reactions seen in any of the test animals

Remarks on result:

no indication of skin sensitisation

Remarks:

Challenged with APT, 75% w/v in Alembicol

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.1 ml of 10% APT (w/v) in a 50:50 mixture of Freund's complete adjuvant and Alembicol D

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No dermal reactions seen in any of the test animals

Remarks on result:

no indication of skin sensitisation

Remarks:

Challenge with APT, 37.5% w/v in Alembicol

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.1 ml of 10% APT (w/v) in a 50:50 mixture of Freund's complete adjuvant and Alembicol D

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No dermal reactions seen in any of the test animals

Remarks on result:

no indication of skin sensitisation

Remarks:

Challenged with APT, 37.5% w/v in Alembicol

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

HCA, 10% v/v in Alembicol D

No. with + reactions:

10

Total no. in group:

10

Clinical observations:

Dermal reactions seen in all ten test animals. Dryness and sloughing of the epidermis.

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

HCA, 10% v/v in Alembicol D

No. with + reactions:

10

Total no. in group:

10

Clinical observations:

Localised dermal reactions (restricted to a small area of the challenge site), dryness and sloughing of the epidermis, thickening, dryness and sloughing of the epidermis

Remarks on result:

positive indication of skin sensitisation

INDUCTION:

Dermal reactions seen following the induction applications were:

- Intradermal injections - necrosis was recorded at all sites receiving Freund's Complete Adjuvant in test and control animals.

- Slight to well-defined irritation was seen in test animals at sites receiving ammonium paratungstate, 10% w/v in Alembicol D and slight irritation was observed in control animals receiving Alembicol D.

Topical application - slight to well-defined erythema was observed in test animals following topical application with ammonium paratungstate, 75% w/v in Alembicol D.

- Slight erythema was seen in most of the control guinea-pigs.

CHALLENGE:

There were no dermal reactions seen in any of the test or control animals, therefore all ten test animals gave negative responses.

BODYWEIGHTS:

Bodyweight increases were recorded for all guinea-pigs over the period of the study.

CLINICAL SIGNS:

No signs of ill health or toxicity were recorded.

Interpretation of results:

GHS criteria not met

Conclusions:

In this study, Ammonium paratungstate did not produce evidence of skin sensitization (delayed contact hypersensitivity) in any of the ten test animals.

Executive summary:

No skin sensitiation data of sufficient quality were available specifically on ammonium metatungstate (target substance). However, skin sensitisation data are available on ammonium paratungstate (source substance), which are used for read-across. Due to similar water solubility for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate to estimate of potential toxicity for this endpoint. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

supporting study

Study period:

1998-03-24 to 1999-04-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study was performed according to OECD Guideline for Testing of Chemicals No. 406 "Skin Sensitization" and GLP.

Justification for type of information:

1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Tungstate
Target: Ammonium metatungstate
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

A 1999 guinea pig sensitisation study was available of good quality. Therefore, there is no need to conduct a LLNA study as the guinea pig sensitisation study scientifically fulfills the endpoint. The OECD 406 method provides sensitisation information likely to arise from exposure to test substance via intradermical injection and/or epidermical application to guinea pigs. The guinea pig sensitisation test detects chemicals with moderate to strong sensitisation potential, as well as those with relatively weak sensitisation potential. In such methods activity is measured as a function of challenge-induced dermal hypersensitivity reactions elicited in test animals compared with controls. In addition, guinea pigs have been the animal of choice for predictive sensitisation tests for several decades (way before the LLNA became the test of choice).
The existing guinea pig data submitted here is of good quality as clear results are presented in this robust summary and test methodology followed OECD 406 guidelines, and conducted under GLP. This study it is considered acceptable according to page 266 in ECHA's Chapter r7a on Guidance on Information Requirements and Chemical Safety Assessment.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: D. Hall, Newchurch, Staffs, UK.
- Age at study initiation: 4 to 7 weeks
- Weight at study initiation: 419 to 527 g
- Housing: Five suspended metal cages with wire mesh floors.
- Diet: Vitamin C enriched guinea-pig diet (Harlan Teklan 9600 FD2 SQC) - ad libitum. Hay was given thrice weekly.
- Water: ad libitum.
- Acclimation period: 12 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.5 to 23.5
- Humidity (%): 40 to 59%
- Air changes (per hr): 15/hr
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1998-03-24 To: 1998-04-24

Route:

intradermal

Vehicle:

other: Distilled water

Concentration / amount:

Induction intradermal injection: 5% w/v in sterile water for injection.
Induction topical application: 75% w/v in distilled water.
Topical challenge: 5 and 2.5% w/v in distilled water.

Route:

epicutaneous, occlusive

Vehicle:

other: Distilled water

Concentration / amount:

Induction intradermal injection: 5% w/v in sterile water for injection.
Induction topical application: 75% w/v in distilled water.
Topical challenge: 5 and 2.5% w/v in distilled water.

No. of animals per dose:

10 animals.

Details on study design:

RANGE FINDING TESTS: The intradermal and topical irritancy of a range of dilutions of the test substance was investigated to identify where possible (a) concentrations of the test substance that would produce irritation suitable for the induction phase of the main study and (b) a maximum non-irritant concentration by the topical route of administration for the challenge phase.
Animals for these investigations were pre-treated with an intradermal injection of Freund's complete adjuvant, 50:50 with water for irrigation (Ph. Eur.), approximately two weeks prior to the start of the preliminary investigations.


MAIN STUDY
A. INDUCTION INTRADERMAL EXPOSURE
- No. of exposures: Three pairs
- Test groups: 0.1 mL of FCA 50:50 with sterile water; 0.1 mL of test substance, 5% w/v in sterile water; 0.1 mL of test substance, 5% w/v in 50:50 mixture of FCA and sterile water for injection.
- Control groups: 0.1 mL of FCA 50:50 with sterile water, 0.1 mL of sterile water, and 0.1 mL of FCA 50:50 with sterile water.
- Site: Scapular area
- Concentrations: 5% w/v

MAIN STUDY
A. INDUCTION TOPICAL EXPOSURE
- No. of exposures: One
- Test groups: 0.4 mL of test substance, 75% w/v in distilled water
- Control group: Concurent no treatment.
- Site: Interscapular area
- Duration: 48 hours
- Concentrations: 75% w/v


B. CHALLENGE EXPOSURE
- No. of exposures: Single
- Test groups: 0.2 mL of test substance, 5% w/v in distilled water and 0.2 mL of test substance, 2.5% w/v in distilled water.
- Control group: Same as test group.
- Site: Anterior site on the flank and posterior site on the flank respectively.
- Concentrations: 5% w/v and 2.5% w/v respectively.
- Evaluation (hr. after challenge): two weeks

Challenge controls:

Control animals were not exposed within either induction period. Animals were exposed to the same concentrations of test substance as test animals.

Positive control substance(s):

yes

Remarks:

Hexyl cinnamic aldehyde (HCA), Benzocaine and 2-mercaptobenzothiazole (MBT)

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.1 mL of 2.5 and 5% w/v sodium tungstate in distilled water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no signs of ill health or toxicity were observed

Remarks on result:

other: see Remark

Remarks:

Reading: 1st reading. Hours after challenge: 24.0. Group: test group. Dose level: 0.1 mL of 2.5 and 5% w/v sodium tungstate in distilled water. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: no signs of ill health or toxicity were observed.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.1 mL of 2.5 and 5% w/v in distilled water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no signs of ill health or toxicity were observed

Remarks on result:

other: see Remark

Remarks:

Reading: 2nd reading. Hours after challenge: 48.0. Group: test group. Dose level: 0.1 mL of 2.5 and 5% w/v in distilled water. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: no signs of ill health or toxicity were observed.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

10%

No. with + reactions:

10

Total no. in group:

10

Clinical observations:

Localised dermal reaction (restricted to a small area of the challenge site); dryness sloughing of the epidermis

Remarks on result:

positive indication of skin sensitisation

Remarks:

Reactions in anterior site, exposed to HCA (as supplied) and posterior site, exposed to HCA, 50% in Alembicol D

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

Distilled water - 0.1 ml

No. with + reactions:

0

Total no. in group:

2

Clinical observations:

Slight irritation

Remarks on result:

no indication of skin sensitisation

CLINICAL SIGNS:

No signs of ill health or toxicity were recorded.

INDUCTION:

-Intradermal injections: Necrosis was recorded at most sites receiving FCA in test and control animals. Slight to well-defined irritation was seen in test animals at sites receiving the test substance, 5% w/v in sterile water for injection. No irritation was observed in control animals receiving sterile water for injection.

-Topical application: Slight to well-defined erythema was observed in test animals following topical application with the test substance, 75% w/v in distilled water. Slight erythema was seen in most of the control guinea-pigs.

CHALLENGE:

There were no dermal reactions seen in any of the test or control animals. All ten test animals gave negative responses.

Interpretation of results:

GHS criteria not met

Conclusions:

The test substance did not produce evidence of skin sensitization (delayed contract hypersensitivity) in any of the ten test animals under the conditions of the assay.

Executive summary:

No skin sensitisation data of sufficient quality were available specifically on ammonium metatungstate (target substance). However, skin sensitisation data are available on sodium tungstate (source substance), which are used for read-across. Due to similar water solubility and toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate for this endpoint. In addition, read-across is appropriate because the classification and labelling is similar for the source substance and target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, conservative for the target substance. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.

Reference 3

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

supporting study

Study period:

1990-10-09 to 1991-01-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Well documented, scientifically sound study conducted in accordance to GLP and OECD 406. The reliability of this study for this substance tested is a K1, but in application of read-across to a different substance, ECHA's guidance specifies that the score can be a maximum of a K2.

Justification for type of information:

1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Metatungstate
Target: Ammonium metatungstate
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR

Reason / purpose for cross-reference:

read-across: supporting information

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:

A 1991 guinea pig sensitisation study was available of good quality. Therefore, there is no need to conduct a LLNA study as the guinea pig sensitisation study scientifically fulfills the endpoint. The OECD 406 method provides sensitisation information likely to arise from exposure to test substance via intradermical injection and/or epidermical application to guinea pigs. The guinea pig sensitisation test detects chemicals with moderate to strong sensitisation potential, as well as those with relatively weak sensitisation potential. In such methods activity is measured as a function of challenge-induced dermal hypersensitivity reactions elicited in test animals compared with controls. In addition, guinea pigs have been the animal of choice for predictive sensitisation tests for several decades (way before the LLNA became the test of choice).
The existing guinea pig data submitted here is of good quality as clear results are presented in this robust summary and test methodology followed OECD 406 guidelines, and conducted under GLP. This study it is considered acceptable according to page 266 in ECHA's Chapter r7a on Guidance on Information Requirements and Chemical Safety Assessment.

Species:

guinea pig

Strain:

other: Himalayan, albino (SPF-quality)

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: BRL Ltd., Basel, Switzerland
- Age at study initiation: approximately 11 weeks
- Weight at study initiation: 343-460 grams
- Housing: Animals were housed in groups of two in cages with wire mesh floors.
- Diet: Animals had free access to standard guinea pig diet, including ascorbic acid (1600 mg/kg); LC 23-B, pellet diameter 4 mm (Hope Farms, Woerden, The Netherlands). In addition, once a week hay was provided (Broekman Institute, Someren, The Netherlands).
- Water: Tap water, diluted with decalcified water, was available ad libitum
- Acclimation period: At least five days before start of treatment under test conditions after physical examination.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The optimal temperature was 21 degrees C. Fluctuations from this were noted, but were not considered to have affected study integrity.
- Humidity (%): The optimal relative humidity was 55 %. Fluctuations from this were noted, but were not considered to have affected study integrity.
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Route:

intradermal and epicutaneous

Vehicle:

other: physiological saline (induction-intradermal injection) and distilled water (induction-epidermal application, and challenge)

Concentration / amount:

-Induction (intradermal): 1% (w/w) in physiological saline
-Induction (epidermal): 7.5% (w/w) in distilled water
-Challenge: 1, 2 and 5% (w/w) in distilled water
-Re-challenge: 0.5, 1 and 2% (w/w) in distilled water

Route:

epicutaneous, occlusive

Vehicle:

other: physiological saline (induction-intradermal injection) and distilled water (induction-epidermal application, and challenge)

Concentration / amount:

-Induction (intradermal): 1% (w/w) in physiological saline
-Induction (epidermal): 7.5% (w/w) in distilled water
-Challenge: 1, 2 and 5% (w/w) in distilled water
-Re-challenge: 0.5, 1 and 2% (w/w) in distilled water

No. of animals per dose:

Ten animals were assigned to the control group and twenty animals were assigned to the test substance group.

Details on study design:

RANGE FINDING TESTS:
Five female guinea pigs were used for a primary irritation test, one week before the main study. The objective of this study was to identify irritant test substance concentrations suitable for the induction phase of the main study. In addition, a suitable non-irritant concentration of the test substance, by the topical route of administration, was identified for the first challenge application. Any possible systemic toxic effects were evaluated for in the primary irritation experiment. The methods for the irritation study were as follows:
1. Intradermal injections:
Four intradermal injections (0.1 ml/site) were made into the clipped shoulder region of one guinea pig at a concentration of 5% (w/w) of the test substance in distilled water. The resulting dermal reactions were assessed 24 and 48 hours later.
-Erythema: scored according to the scale described below under epidermal applications.
-Necrosis: if present yes or no
-Diameter: (mm) of effect (erythema, necrosis or discolouration)
2. Epidermal applications:
The intradermally injected animal was also treated epidermally at the shaved left flank with 0.5 ml of a 50% (w/w) concentration of the test substance in distilled water using a Metalline patch mounted on Micropore tape and held in place with Coban elastic bandage. After 24 hours, the dressings and residual test substance were removed using a moistened tissue. The treated skin was assessed for erythema and edema 24 and 48 hours after bandage removal on a numerical basis according to the scale below.

Four animals were shaved on the left flank and exposed to 0.05 ml of a 50%, 25%, 10% and 5% (w/w) test substance concentration in distilled water, occlusively administered by means of Square chambers mounted on Micropore tape and fixed in place by means of Coban elastic bandage. This procedure ensured the intensive contact of the test substance even if it was insoluble in the vehicle used. After 24 hours, the dressings and residual test substance were removed using a moistened tissue. The reaction sites were assessed for erythema and edema on a numerical basis according to the scale below, 24 and 48 hours after bandage removal. Immediately after the 24 hour skin reading the treated areas were shaved.

Erythema and eschar formation:
-No erythema: 0
-Slight erythema (barely perceptible: 1
-Well-defined erythema: 2
-Moderate erythema: 3
-Sever erythema (beet redness) to slight eschar formation (injuries in depth): 4
Oedema:
-No oedema: 0
-Slight oedema (barely perceptible): 1
-Well-defined oedema (edges of area well-defined by definite raising): 2
-Moderate oedema (raised approximately 1 millimeter): 3
-Severe oedema (raised more than 1 millimeter and extending beyond the area of exposure): 4

MAIN STUDY
A. INDUCTION EXPOSURE
Intradermal injections:
On day 1 an area of the dorsal skin from the scapular region (approximately 4 x 6 cm) was clipped free of hair. Three pairs of intradermal injections (0.1 ml/site) were made at the border of a 2 x 4 cm area in the clipped region as follows:
1. The test substance dissolved to 1% (w/w) with physiological saline.
2. Freunds' Complete Adjuvant, 50:50 with distilled water for injection.
3. The test substance, at twice the concentration used in (1), emulsified in a 50: 50 mixture of Freunds' Complete Adjuvant.
Note: Injection 1 was made at the left and right side near the cranial region and injection 3 was made on the left and right side near the caudal region. Injection 2 was made in the middle of the other injections on both sides.

Epidermal applications:
Seven days after the intradermal injections, the scapular area (approximately 6 x 8 cm) was clipped and shaved free of hair. A 2 x 4 cm patch of Metalline mounted on Micropore tape was applied with 0.5 ml of the test substance (7.5 % (w/w) in distilled water) and placed over the injection sites of the test animals. The Micropore tape was firmly secured, wrapped around the trunk of the animal and secured with Coban elastic bandage. After 48 hours, the dressings and residual test substance were removed using a moistened tissue. The epidermal application procedure ensured intensive contact of the test substance even if it was insoluble in the vehicle used.

The guinea pigs of the control group were treated as described above by the intradermal and epidermal inductions with the omission of test substance.

Reaction sites were assessed for erythema and edema immediately after removal of the dressings, using the numerical grading system described above under the "range-finding" test.

B. CHALLENGE EXPOSURE
The test and control guinea pigs were challenged two weeks after the epidermal induction application.
Hair was clipped and shaved from a 5 x 5 cm area on the left flank of each guinea-pig. The following series of 3 test concentrations and the vehicle were applied using Square chambers attached to Micropore tape:
1 = 5% in distilled water
2 = 2% in distilled water
3 = 1% in distilled water
4 = distilled water
A volume of 0.05 ml of each concentration or the vehicle was placed into a Square chamber. The patches were placed on the shaved area, the Micropore tape firmly secured around the trunk of the animals and held in place by Coban elastic bandage.
Note: Patches 3 and 4 were placed on the cranial side, while patches 1 and 2 were placed on the caudal side.

The dressings and residual test substance were removed after approximately 24 hours, using a moistened tissue. The sites were assessed for redness and swelling 24 and 48 hours after removal of the dressings, using the numerical grading system described below. The test sites were shaved with an electric razor after the first reading.
-no skin reaction: 0
-red spots (scattered reactions): 1
-moderate but confluent redness: 2
-redness and swelling: 3
-intense reddening and swelling: 4

RE-CHALLENGE:
A second challenge was performed one week after the first challenge, due to inconclusive results.
The method was similar to the first challenge on all animals, but the contralateral flank was applied. The following test substance concentrations (2%, 1% and 0.5%) and the vehicle were applied. These concentrations were decreased due to irritancy of the 5 % test substance concentration in the control animals.

OTHER:
Prior to each treatment the test substance was weighed into small glass containers and distilled water or physiological saline was added (w/w). Homogeneity was obtained by using a mechanical stirrer.

In addition to the skin reactions the following observations and data were recorded:
-Mortality/viability: once daily
-Body weights: during acclimatisation and at termination of the study
-Toxicity symptoms: daily

Challenge controls:

Distilled water

Positive control substance(s):

yes

Remarks:

Positive control experiments were carried out once a year as a sensitivity check of the test system as used by the testing laboratory. The most recent test was carried out in April 1990 with Formaldehyde.

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

Formaldehyde 0.5%

No. with + reactions:

19

Total no. in group:

30

Remarks on result:

positive indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

1, 2, & 5%

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None of the experimental animals showed a positive skin reaction in response to the any of the concentrations tested in the second challenge

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.5, 1, & 5%

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None of the experimental animals showed a positive skin reaction in response to the any of the concentrations tested in the second challenge

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0.5, 1, and 2%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions were evident after the second challenge exposure

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

0.5, 1, & 2%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions were evident after the second challenge exposure

Remarks on result:

no indication of skin sensitisation

Range-finding irritancy study

No signs of systemic toxicity were observed during the primary irritation experiments. However body weight loss was noted in one of the five animals. The choice of distilled water as vehicle in the test was based on the following:

-The test substance suspended well in distilled water at the concentrations used.

-The test substance was stable in distilled water.

Main Study

Induction:

None of the experimental animals showed skin irritation after the 48 hours occluded epidermal induction exposure.

First challenge: All ten control animals showed skin reactions in response to the 5% test substance concentration. These reactions were characterised by red spots in six animals and by redness, swelling and brown/white discoloration as a sign of necrosis in the other four control animals. Two control animals also showed red spots in response to the 1% concentration. Nineteen, five and four experimental animals showed skin reaction in response to the 5%, 2% and 1% concentration, respectively. The reactions to the 5% concentration were characterised by red spots in seven animals and by redness, swelling and brown/white discoloration as a sign of necrosis, in twelve experimental animals. The reactions to the 2% and 1% concentrations were characterised by red spots.

Second challenge: No skin reactions were evident after the second challenge exposure in the control animals. None of the experimental animals showed a positive skin reaction in response to any of the concentrations tested in the second challenge.

Toxicity symptoms/mortality:

No symptoms of systemic toxicity were observed in the animals during the study. No mortality occurred during the study.

Body weights: The average body weight gain of experimental and control animals was similar. However, it should be noted that one experimental animal gained only 11 grams during the study period.

The results led to a skin sensitisation rate of 0%, which indicated that the test substance had weak sensitising properties in the test applying the rating of allergenicity.

Interpretation of results:

GHS criteria not met

Conclusions:

Sodium metatungstate was assessed for skin sensitisation potential in the "Guinea Pig Maximization Test". The results led to a sensitisation rate of 0 percent, which indicated that sodium metatungstate has weak sensitising properties in this test applying the rating of allergenicity described by Kligman A.M. (1966).

Executive summary:

No skin sensitisation data of sufficient quality were available specifically on ammonium metatungstate (target substance). However, skin sensitisation data are available on sodium metatungstate (source substance), which are used for read-across. Due to similar water solubility for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate to estimate of potential toxicity for this endpoint. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.

Reference 4

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Although no study data specifically evaluating the potential respiratory sensitisation effects are available, based on the lack of human case reports indicating that ammonium metatungstate is a respiratory sensitiser, as well as negative responses observed in both the skin sensitisation and skin irritation animal studies, ammonium metatungstate is not likely to be a respiratory sensitiser.

Justification for classification or non-classification

No skin sensitisation data are available for ammonium metatungstate; however, data are available of sifficient quality for ammonium paratungstate, sodium metatungstate and sodium tungstate (source substances) that reported negative results in two Guinea Pig Maximisation Tests. Therefore, based on weight-of-evidence from the available data of the read-across substances, ammonium metatungstate does not warrant classification for skin sensitisation.

No respiratory sensitisation study is available for ammonium metatungstate. Therefore, classification cannot be made due to lack of data. However, this endpoint is not required for REACH registration.