Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2006

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: oil/water emulsion containing 10 % TiO2
Details on test material:
- Name of test material (as cited in study report): Titanium dioxide (two Titanium Dioxide Formulations T-Lite SF-S and T-Lite SF also were oil/water emulsions and each contained 10% titanium dioxide corresponding to about 6wt.% titanium. The titanium dioxide particles in T-Lite SF-S were needle-like with dimensions of 30– 60 x 10nm and coated with silica (2–5 wt.%) and methicone (4.5–6.5%). The titanium dioxide particles in T-Lite SF had the same dimensions as in T-Lite SF-S but were coated with methicone (3.5–5.5%) only.
- Substance type: inorganic
- Physical state: solid; in this study an oil/water emulsion was used
- Analytical purity:
- Other: The titanium dioxide particles were present as aggregates mostly up to 200 nm but partly also with a size up to 1 µm. Aggregates and agglomerates
of titanium dioxide particles were present only in the water phase. The stability, concentration and the homogeneous distribution of the zinc oxide and titanium dioxide in the formulations were confirmed by analysis.
Radiolabelling:
no

Test animals

Species:
pig
Strain:
other: Pietrain-Deutsche Landrasse-Hybrid
Sex:
not specified
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: BASF Agricultural Station, Offenbach, Germany
- Age at study initiation: 5 month

Administration / exposure

Type of coverage:
other: diffusion cell
Vehicle:
physiological saline
Duration of exposure:
up to 24 h
Doses:
The test formulations were applied to 1cm² exposed skin at nominal doses of 4 mg/cm² for 24 hours corresponding to nominal doses of about 400 µg/cm² of zinc oxide or titanium dioxide or to nominal doses of 360 and 240 µg/cm² of zinc or titanium, respectively.
No. of animals per group:
The test formulations were applied to 3 skin preparations from each pig in parallel experimental setup.
Control animals:
no
Remarks:
: in vitro testing
Details on study design:
Full thickness skin samples (epidermis and dermis) of visually intact skin from the lateral abdominal region of 5-month old domestic pigs were dermatomed to a thickness of around 500 µm using a Accu-Dermatome GA 630 (Aesculap, Germany). The samples were mounted in modified Franz static dermal penetration cells (Laboratory Glass Apparatus Inc., USA or BASF AG) consisting of an upper donor compartment and a lower receptor compartment with the external surface of the stratum corneum facing the donor chamber.
Physiological saline containing 5% bovine serum albumin was used, because it represents physiological conditions. BSA was expected to increase solubility by providing a sink for metal ions by protein binding (scavenging). The receptor chambers were filled with approximately 4 ml of the receptor fluid and the cells were placed on a magnetic stirrer (Variomag Telemodul 20C/40C, H+ P Labortechnik, Germany) in a water bath (Haake, Germany) maintained at 32+/-1 °C. Each skin sample was checked for integrity by measuring its electrical resistance with a LCR bridge (LCR 400, Thurlby Thandar Instruments, England) prior to testing. The skin absorption studies were performed with three pigs per test formulation, and the test formulations were applied to three (TiO2) skin preparations from each pig in a parallel experimental setup. The test formulations were applied to 1 cm2 exposed skin at nominal doses of 4mg/cm2 for 24 h corresponding to nominal doses of about 400 µg/cm2 of titanium dioxide or to nominal doses of 240 µg/cm2 of titanium, respectively.
Samples of receptor fluid were taken at various time intervals (3, 6, 12 and 24 hours) after application of the test formulation to the skin and retained for analysis. The skin was removed from the diffusion cell and put onto parafilm. Titanium was removed from the skin preparations by washing with sponge pieces dipped into soap solution, and subsequent tape stripping was used to remove titanium together with the superficial layers of the stratum corneum.
The pools of tape strips, the skin remaining after tape stripping, and all retained receptor fluid samples were acid-treated and analyzed for titanium by atomic spectroscopy (AS). Depending on the concentration of the samples, inductively coupled plasma-atomic emission spectrometry (ICP-AES, Varian Vista Pro, Wavelength: 336.122nm, external calibration, linear range 0.05–10mg/l) or -mass spectrometry (ICP-MS, Agilent 7500c, mass isotope: Ti 47, internal standard
Rh 103. Linear range 0.1–50 µg/l) was applied for Ti analyses.
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: Full thickness skin samples (epidermis and dermis) of visually intact skin from the lateral abdominal region of 5-month old domestic pigs of the Pietrain—Deutsche Landrasse—Hybrid strain, supplied by BASF Agricultural Station, Ovenbach, Germany, were dermatomed to a thickness of around 500µm using a Accu-Dermatome GA 630 (Aesculap, Germany).
- Ethical approval if human skin: n.a.
- Type of skin: see above
- Preparative technique: Accu-Dermatome
- Thickness of skin (in mm): 0.5
- Membrane integrity check: Each skin sample was checked for integrity by measuring its electrical resistance with a LCR bridge
- Storage conditions: the samples were mounted in modified Franz static dermal penetration cells;
- Justification of species, anatomical site and preparative technique: not reported

PRINCIPLES OF ASSAY
- Diffusion cell: Diffusion cell modified Franz cell consisting of an upper donor compartment and a wide opening at the top and a lower receptor compartment.
- Receptor fluid: Physiological saline containing 5 % bovine serum albumin (BSA)
- Solubility of test substance in receptor fluid: Titanium dioxide is virtually insoluble in water. BSA was expected to increase solubility by providing a sink for metal ions by protein binding (scavenging).
- Static system: modified Franz static dermal penetration cells
- Flow-through system: n.a.
- Test temperature: 32+/- 1°C
- Humidity: no data
- Occlusion: no data
- Reference substance(s): no data

Results and discussion

Signs and symptoms of toxicity:
not examined
Remarks:
: in vitro absorption was investigated
Dermal irritation:
not examined
Remarks:
: in vitro absorption was investigated
Absorption in different matrices:
Mean total titanium recoveries were in the range of 90.4 and 99.4 % for the T-Lite SF and T-Lite SF-S formulations, respectively.
- Receptor fluid, receptor chamber, donor chamber (in vitro test system): 0 %
- Skin preparation (in vitro test system): 0.2 %
- Stratum corneum (in vitro test system): (i.e tape strips) 0-0.1%
Total recovery:
- 90.4% to 99.4 % for T-Lite SF and T-Lite SF-S, respectively
- Recovery of applied dose acceptable: yes
- Results adjusted for incomplete recovery of the applied dose: no data
- Limit of detection (LOD): 0.3 µg; The amounts of titanium found in the tape strips and skin preparations were in the order of the analytical determination limit.
- Quantification of values below LOD or LOQ: no data
Percutaneous absorption
Dose:
10 %
Parameter:
percentage
Absorption:
ca. 0 %
Remarks on result:
other: 24 h
Remarks:
no absorption of both formulations (T-Lite SF-S and T-Lite SF)
Conversion factor human vs. animal skin:
n.a.

Any other information on results incl. tables

Results show that the test substance was not able to penetrate porcine stratum corneum.

Applicant's summary and conclusion

Conclusions:
Results show that the titanium dioxide was not able to penetrate porcine stratum corneum.
Executive summary:

In the experiments with micro fine titanium dioxide formulations T-Lite SF-S and T-Lite SF, mean total recoveries of Ti ranged from 98% to 100% and 86% to 93% of the total Ti applied, respectively. Virtually the total amount of applied Ti could be removed from the skin surface by washing. The amounts of titanium found in the tape strips and skin preparations were in the order of the analytical determination limit. No Ti was found in the receptor fluid at any sampling time. The results show that titanium ions and titanium dioxide particles were not able to penetrate porcine stratum corneum. Therefore, from the absence of internal exposure we conclude that they do not pose a health risk.