Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From January 18th to 22nd, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Version / remarks:
April, 2004
GLP compliance:
no
Remarks:
No GLP test but carried out in GLP compliant facility.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
In the study two sample were tested:
- P4S3 solid about 100 % w/w
- P4S3 resin 10 % w/w (containing 53.11 % water)
Radiolabelling:
no

Administration / exposure

Vehicle:
unchanged (no vehicle)
Duration of exposure:
22 hours
Doses:
8 mg of the powder and about 16 mg of the paste taking in account the percentage of water (4 replicates each, sampled after 0.5, 9 and 22 hours: total 12 samples for solid and 12 samples for resin).
A negative control (skin disc without test compound) was incubated in parallel to assess potential analytical interference.
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: Female donor 68 age years
- Ethical approval if human skin: Caucasian.
- Type of skin: human abdominal skin.
- Preparative technique: cryopreserved dermatomized
- Thickness of skin (in mm): 0.410- 0.500 mm
- Membrane integrity check: before starting the study, i.e. one hour at least after the skin discs were mounted on the diffusion cells, the TEWL was measured with an evaporimeter placed at the top of each diffusion cell. All skin discs exhibited a TEWL value below 15 g/m2 h and were included in the study.

PRINCIPLES OF ASSAY
- Diffusion cell: Franz-type diffusion cells.
- Receptor fluid: sodium chloride solution at 9 g/l in water containing 5 % (w/v) bovine serum albumin (total amount of receptor fluid: 2 ml)
- Static system: yes
- Test temperature: 32 °C ± 1
- Incubation method: at 0.5, 9 and 22 hours, one aliquot of receptor liquid (200 µl) was removed, transferred in labelled tubes and stored at -80 °C until analysis. At 0.5 and 9 hours, the volume removed from receptor compartment was renewed by the same volume of fresh receptor liquid to maintain a constant volume. After 22 hours of incubation, the skin surface was cleaned in order to remove the excess of the test item not penetrated: rinsing of the skin surface with carbon disulfide (2 x 0.5ml) and cleaning once with one dry pad. The rinse and the pad were put together in an identified tube stored at - 80 °C. The epidermis and the dermis (not separated) were put in identified tubes and stored at - 80 °C.
- Data treatment: for each condition, the mean (in µg/g) and the standard deviation were calculated. The cumulated amount of phosphorous in the receptor compartment was then calculated and expressed in µg. This amount was compared with the amount available in the donor compartment taking into account the percentage of phosphorous in P4S3 (55.8 %) and the ratio was expressed as percentage of the theoretical dose.

Results and discussion

Percutaneous absorption
Key result
Time point:
22 h
Dose:
P4S3 solid about 100 % w/w
Parameter:
percentage
Absorption:
ca. 1.8 %

Any other information on results incl. tables

Phosphorus concentration in receptor fluid after topical application of P4S3 in powder (100 %) or P4S3 formulated in paste (at 10 %)

After incubation of P4S3 on human skin, very small amounts of phosphorous were observed in the receptor fluid from 0.5 hours of incubation: 1.23 µg/g when P4S3 was applied as powder (i.e., at 100 %) and 0.821 µg/g when P4S3 was applied as paste (formulation at 10% in a resin). An increase of the diffusion of phosphorus across the skin was observed between 0.5 and 22 hours. After 22 hours of incubation, the amount of phosphorous in fluid receptor reached 40.3 µg/g when P4S3 was applied as powder (i.e., at 100 %) and 3.32 µg/g when P4S3 was applied as paste (formulation at 10 %).

Cumulated amount of phosphorous in receptor fluid and percentage of theoretical applied dose after topical application of P4S3

The cumulated amount of phosphorous after 22 hours of incubation was 85.4 µg and 7.13 µg when P4S3 was applied at 100 % and 10 %, respectively, representing 1.8 % and 1.63 % of the amount of phosphorous available in the donor compartment.

Conclusion

Human abdominal skin was used to evaluate the skin diffusion of phosphorous sesquisulfide using Franz-type diffusion static cells as in vitro model. After incubation of P4S3 on human skin, small amounts of phosphorous were observed in the receptor fluid from 0.5 hours of incubation. The cumulated amount of phosphorous after 22 hours of incubation represented 85.4 µg when P4S3 was applied as powder (i.e., at 100 %) and 7.13 µg when P4S3 was applied as paste (formulation at 10 % in a resin). In conclusion, a diffusion of phosphorous sesquisulfide through human skin has been observed with a maximal absorption that represented 1.8 % of the theoretical applied dose.

Applicant's summary and conclusion

Conclusions:
Experimental dermal absorption of Tetraphosphorus trisulphide (solid 100 % w/w) during 22 h of exposure was 1.8 %.
Executive summary:

Tetraphosphorus trisulphide was applied as powder or formulated in a resin on human abdominal skin for up to 22 hours in order to investigate the diffusion of phosphorous sesquisulfide across the skin. Franz-type diffusion static cells were used as in vitro model. The receptor fluid was sampled at 0.5, 9 and 22 hours for the quantification of phosphorous according to a ICP-MS method previously validated. After incubation of P4S3 on human skin, small amounts of phosphorous were observed in the receptor fluid after 0.5 hours of incubation. The cumulated amount of phosphorous after 22 hours of incubation represented 85.4 µg when P4S3 was applied as powder (i.e., at 100 %) and 7.13 µg when P4S3 was applied as paste (formulation at 10 % in a resin).

In conclusion, a diffusion of Tetraphosphorus trisulphide through human skin has been observed with a maximal absorption that represented 1.8 % of the theoretical applied dose.

After 22h of exposure the dermal absorption of pure P4S3 solid and of P4S3 contained into the resin at a concentration of 10 % w/w were respectively 1.8 % and 1.63 %.

Note: the only use of Tetraphosphorus trisulphide is in the production of matches where it is contained into a resin at a concentration of about 10 % w/w. The risk assessment for Tetraphosphorus trisulphide is based on the data obtained in this study using the absorption of P4S3 as resin during 0.5 h, corresponding to the value of 0.4 % .