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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
See read-across justification report under Section 13 ‘Assessment Reports’.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.

The similarities may be based on:
(1) a common functional group
(2) the common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or
(3) a constant pattern in the changing of the potency of the properties across the category

1. Both substances are inorganic salts of a monovalent cation from Group 1A of the periodic table, and triphosphoric acid. Thus, they share the Na+ or K+ cation and P3O105- anion.
2. As both substances contain the same anion, any sensitisation potential from the anion will be the same for both compounds.
3. Sodium and potassium are both group 1 alkali metals, the ionic charges are the same and the chemical behaviour will be similar. Potassium has a larger ionic radius and as penetration of the skin is largely governed by molecular size, the ability of potassium to penetrate the skin is likely to be less than sodium. As the chemical behaviour of both the anion and the cation will be similar and the dermal absorption of the cation is likely to be reduced, the negative results from pentasodium triphosphate can reliably be read across to pentapotassium triphosphate.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across justification report under Section 13 ‘Assessment Reports’.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across justification report under Section 13 ‘Assessment Reports’.

4. DATA MATRIX
See read-across justification report under Section 13 ‘Assessment Reports’.
Cross-reference
Reason / purpose for cross-reference:
read-across: supporting information

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report date:
2008

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Chemical structure
Reference substance name:
Pentasodium triphosphate
EC Number:
231-838-7
EC Name:
Pentasodium triphosphate
Cas Number:
7758-29-4
Molecular formula:
Na5P3O10 H5-xP3O10Nax (where x is approximately 5) 6H2O.Na5P3O10
IUPAC Name:
Pentasodium triphosphate
Details on test material:
- Name of test material (as cited in study report): Sodium tripolyphosphate (STPP)
- Physical state: White solid
- Storage condition of test material: Room temperature in the dark

In vivo test system

Test animals

Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan UK limit
- Age at study initiation:
- Weight at study initiation: 15-23g
- Housing: individually in suspended solid floor polypropylene cages
- Diet (e.g. ad libitum): certified rat and mouse diet ad libitum
- Water (e.g. ad libitum):mains tap water ad libitum
- Acclimation period: 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 25-30
- Humidity (%): 19-70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light):12/12


IN-LIFE DATES: From: 04/03/2008 To: 26/04/2008

Study design: in vivo (LLNA)

Vehicle:
other: 1% pluronic L92 in distilled water
Concentration:
1, 2.5 and 5%
No. of animals per dose:
4
Details on study design:
MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method:LLNA
- Criteria used to consider a positive response:Test material regarded as a sensitiser if at least one concentration of the test material results in a threefold or greater increase in HTdR incorporation compared to control values


TREATMENT PREPARATION AND ADMINISTRATION: Freshly prepared in 1% pluronic L92 in distilled water
daily application of 25µl of 1, 2.5 or 5% w/w test material
Positive control substance(s):
other: 2,4-Dinitrobenzenesulfonic acid, sodium salt

Results and discussion

Positive control results:
2,4-dinitrobenzenesulfonic acid, sodium salt in 1% pluronic L92 in distilled water
Concentration, Stimulation index, Result
1%, 1.80, Negative
5%, 4.32, Positive
10% , 11.98, Positive

In vivo (LLNA)

Resultsopen allclose all
Key result
Parameter:
SI
Value:
1.27
Test group / Remarks:
1% w/w in vehicle
Key result
Parameter:
SI
Value:
1.17
Test group / Remarks:
2.5% w/w in vehicle
Key result
Parameter:
SI
Value:
1.31
Test group / Remarks:
5% w/w in vehicle

Any other information on results incl. tables

Table 1. Results of the Local Lymph Node Assay.

Concentration (% w/w) in 1% pluronic L92 in distilled water

DPM

DPM/node

Stimulation index

Results

Vehicle

2501.00

312.63

n.a.

n.a.

1

3176.25

397.27

1.27

Negative

2.5

2938.16

367.27

1.17

Negative

5

3279.54

409.94

1.31

Negative

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test material was considered to be a non-sensitiser under the conditions of the test. The study is considered to be reliable and acceptable for use as a key study for read across to pentapotassium triphosphate (potassium tripolyphosphate).