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Description of key information

Tungsten metal powder was deemed to be not sensitizing following a skin sensitisation study conducted on guinea pigs according to OECD Guideline 406.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation, other
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998-03-31 to 1999-04-07
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented OECD guideline study performed under GLP.
Qualifier:
according to
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 wks
- Weight at study initiation: 371 to 436 g
- Housing: In groups of five in suspended metal cages with wire mesh floors.
- Diet: ad libitum Vitamin C enriched (Harlan Teklad 9600 FD2 SQC). Hay was given thrice weekly.
- Water: ad libitum
- Acclimation period: 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16 to 25.5
- Humidity (%): 37 to 66
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light):12/12


IN-LIFE DATES: From: 1998-03-31 to: 1998-05-01
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
20% w/v in water
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No signs of ill health or toxicity were recorded.
Remarks on result:
no indication of skin sensitisation
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. No with. + reactions: 0.0. Total no. in groups: 10.0.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
Dose level:
20% w/v in water
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No signs of ill health or toxicity were recorded.
Remarks on result:
no indication of skin sensitisation
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No signs of ill health or toxicity were recorded..
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
No. with + reactions:
0
Total no. in group:
5
Remarks on result:
no indication of skin sensitisation
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. No with. + reactions: 0.0. Total no. in groups: 5.0.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
No. with + reactions:
0
Total no. in group:
5
Remarks on result:
no indication of skin sensitisation
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. No with. + reactions: 0.0. Total no. in groups: 5.0.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
10% hexyl cinnamic aldehyde (HCA) in Alembicol D - Not concurrent
No. with + reactions:
15
Total no. in group:
15
Clinical observations:
Dryness and sloughing of the epidermis
Remarks on result:
positive indication of skin sensitisation

RESULTS

Dermal reactions seen following the induction:

- Intradermal injections:

Necrosis was recorded at most sites receiving Freund's Complete Adjuvant in both test and control animals.

Slight irritation was seen in most test animals at sites receiving Tungsten metal powder (20% w/v) in sterile water. No irritation was observed in control animals receiving sterile water for injection.

Topical application:

Slight erythema was observed in most test animals following topical application with Tungsten metal powder, 70% w/v in distilled water. Slight erythema was also seen in most of the control guinea-pigs after topical application of distilled water alone.

- Dermal reactions elicited by the challenge applications:

No dermal reactions were seen in any of the test or control animals.

BODYWEIGHT

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:
Under conditions of this study, Tungsten metal powder did not produce evidence of skin sensitization (delayed contact hypersensitivity).
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 tungsten metal is a respiratory sensitiser, as well as negative responses observed in both the skin sensitisation and skin irritation animal studies, tungsten metal is not likely to be a respiratory sensitiser.

Justification for classification or non-classification

A skin sensitisation test of sufficient quality and tested in accordance with standard methodology was available for tungsten metal. The results of this study showed that tungsten metal did not cause skin sensitisation in Guinea Pigs. Therefore, no classification is warranted for the skin sensitisation endpoint. No respiratory sensitization study is available for tungsten metal. Therefore, classification cannot be made due to lack of data. However, this endpoint is not required for REACH registration.