Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: comparable to guideline study with acceptable restrictions

Data source

Reference
Reference Type:
publication
Title:
Percutaneous Penetration of 2-Phenoxyethanol through Rat and Human Skin.
Author:
Roper, C.S. et al.
Year:
1997
Bibliographic source:
Food and Chemical Toxicology 35:1009-1016

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Deviations:
yes
Remarks:
Data from a minimum of four replicates per test preparation are required. However, due to the limited supply of human skin, only three replicates were run.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 2-Phenoxy[1-14C]ethanol; synthesized by the Environmental Safety Laboratory, Unilever Research, Coleworth House, UK
- Radiochemical purity (if radiolabelling): > 99%
- Specific activity (if radiolabelling): 3.74mCi/mg
Radiolabelling:
yes
Remarks:
14C

Test animals

Species:
other: rat and human skin
Strain:
Wistar
Details on test animals and environmental conditions:
Male rats (28 - 35 days old) were received from the Comparative Biology Centre, The Medical School, University of Newcastle upon Tyne.
Human skin samples were obtained at operation (breast, leg and abdomen). No further details published.

Administration / exposure

Type of coverage:
other: uncovered and covered
Vehicle:
other: methanol
Duration of exposure:
E. g. sampling time:
Rat: Static diffusion cell: 0, 20, 40, 60 and 90 minutes, then hourly from 2 to 8 hr, and finally at 10, 12, and 24 hr.
Flow-through diffusion cell: hourly from 2 to 8 hr, and finally at 10, 12, and 24 hr.
Individual cells for determination of unabsorbed material (surface wash): 0, 1, 4, 8 and 24 hr.
Human: Studies with human skin were carries out in the flow-through diffusion cell in a similar manner to those with the rat skin. 2-Phenoxyethanol was applied to the skin surface (2560 nmol; 1.32 µCi) in 10 µl methanol. Receptor fluid was only collected to 6 hours post application and cells dismantled at 0, 1 and 6 hours to determine distribution. Human skin remains viable for longer periods of time in the flow-through system, but because of the limited supply of human skin from each donor only the early absorption profile was defined.
Doses:
Volume applied: 10 µL/diffusion cell

Rat:
Static diffusion cell: 1556 nmol (0.81 µCi)
Flow-through diffusion cell: 5290 nmol (2.73 µCi)
Human:
Flow-through diffusion cell: 2560 nmol (1.32 µCi)


No. of animals per group:
Rat: 7 rats (uncovered, static diffusion cell); 6 rats (covered, static diffusion cell); Unspecified numbers of rats (uncovered, flow-through diffusion cell)
Human: 3 donor skin samples
Control animals:
no
Details on study design:
Size of test site: Static diffusion cell: 0.79 cm²; Flow-through diffusion cell: 0.64 cm²
Details on in vitro test system (if applicable):
Receptor fluid (static: 50% aqueous ethanol; flow-through: modified Earle’s medium (= MEM) with penicillin/streptomycin)

- surface wash
- stratum corneum
- residual skin

Individual cells were dismantled at 0, 1, 4, 8, and 24 hours for determination of unabsorbed material (surface wash), material associated with the stratum corneum (tape strippings) and material associated wit the epidermis and upper dermis. Separation of the surface wash, stratum corneum and residual skin was carried out: Each cell was washed six times with 2.5ml aliquots of 3% Teepol (v/v), the rinsings were pooled. Tissue swabs were used to dry the skin; these wee analysed by liquid scintillation counting together with the Teepol washing (= unabsorbed material). Radioactivity associated with the sides of the cell or the occlusive device (if used) was included as unabsorbed material. The swabbed skin was tape stripped with Scotch tape (3M) using five pieces (1.5 x 1.5 cm) per cell. The strippings, analysed by liquid scintillation counting, were deemed to be material associated with the stratum corneum. The remaining skin (epidermis and upper dermis) was mixed with 1 ml Biolute S (Zinsser Analytic) tissue solubilizer and incubated at 50°C for 3 hours an then analyzed by liquid scintillation counting.

Results and discussion

Signs and symptoms of toxicity:
not examined
Dermal irritation:
not examined
Total recovery:
Static (24 h):
Total recovery was 67.6% (uncovered skin)
Total recovery was 102.6% (covered skin)

Flow-through (24 h):
Total recovery was 51.0% (uncovered skin)
Percutaneous absorptionopen allclose all
Dose:
static, uncovered
Parameter:
percentage
Absorption:
ca. 64 %
Remarks on result:
other: 24 h
Remarks:
rat; 64 ± 4%
Dose:
static, covered
Parameter:
percentage
Absorption:
ca. 99 %
Remarks on result:
other: 24 h
Remarks:
rat; 98.8 ± 7.0%
Dose:
flow-through, uncovered
Parameter:
percentage
Absorption:
ca. 43 %
Remarks on result:
other: 24 h
Remarks:
rat; 43 ± 3.7%
Dose:
flow-through, uncovered
Parameter:
percentage
Absorption:
ca. 59 %
Remarks on result:
other: 24 h
Remarks:
human; 59.3 ± 7.0%

Applicant's summary and conclusion

Conclusions:
2-Phenoxyethanol was rapidly absorbed through rat skin mounted in both the static and flow-through diffusion cell with either aqueous ethanol or MEM as receptor fluid. The stratum corneum did not appear to be a good barrier to 2-phenoxyethanol penetration. Occlusion increased the permeability coefficient of 2-phenoxyethhanol in the static cell. The permeability profile and amount absorbed were similar for human and rat skin in the flow-through system with tissue culture medium. The mass balance recovery of 2-phenoxyethanol in the unocccluded studies was low; static diffusion 68% and flow-through diffusion cell 51% at 24 hr, due to the high evaporation, as confirmed by only 7.5% remaining on the aluminium foil at 24 hr. The losses from the skin decreased proportionally throughout the experiment due to the penetration of 2-phenoxyethanol into the skin and receptor fluid.