Chromium

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

In vitro absorption of metal powders through intact and damaged human skin

Author:

Larese Filon F, D'Agostin F, Crosera M, Adami G, Bovenzi M and Maina G

Year:

2009

Bibliographic source:

Toxicology in Vitro 23, 574-579

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

yes

Remarks:

(in addition to intact skin, also damaged skin was used)

Principles of method if other than guideline:

To carry out the experiments, the authors used the experience and protocols employed during the European project EDETOX (evaluations and predictions of dermal absorption of toxic chemicals), funded by EU.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Chromium

EC Number:

231-157-5

EC Name:

Chromium

Cas Number:

7440-47-3

Molecular formula:

Cr

IUPAC Name:

chromium

Details on test material:

- Name of test material (as cited in study report): Chromium powder (CAS 7440-47-3)

- Substance type: powder, APS<10 micron
- Physical state: powder
- Analytical purity: 99,8% (metals basis)
- Impurities (identity and concentrations): no data
- Composition of test material, percentage of components: no data
- Isomers composition: no data
- Purity test date: no data
- Lot/batch No.: no data
- Expiration date of the lot/batch: no data

- Stability under test conditions: no data
- Storage condition of test material: no data
- Other: Manufacturer: Alfa Aesar (karslruhe, Germany)

Radiolabelling:

no

Administration / exposure

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: human (surgical waste)
- Ethical approval if human skin: no data
- Type of skin: full thickness skin
- Preparative technique: Skin obtainead as surgical waste. Prior to freezing, subcutaneous fat was removed and hair shaved. In addition to intact skin, damaged skin was also prepared (skin abraded by drawing the point of a 19-gauge hypodermic needle across the surface; 20 marks in one direction and 20 perpendiculars).
- Thickness of skin (in mm): <1mm ; mean exposed skin area 3.92 cm2
- Membrane integrity check: Skin integry was checked before and after each experiment using electrical conductibility by means of a conductometer (Metrohm, 660 Conductometer, Herisau, Switzerland). The electrical conductance data (as µS) were converted to K[omega]cm-2. Cells with a resistance <3.95 ± 0.27 K[omega]cm-2were considered to be damaged.
- Storage conditions: Freezer -25 C for a period up to (but not exceeding) 4 months
- Justification of species, anatomical site and preparative technique: no data


PRINCIPLES OF ASSAY
- Diffusion cell: Franz diffusion cells
- Cr metal powder was suspended in a synthetic sweat solution with pH 4.5
- Receptor fluid: phosphate buffered saline (PBS) (pH 7.35)
- Solubility od test substance in receptor fluid: no data
- The chromium powder in synthetic sweat was added to the exposure chamber.
- Test temperature: 32 C
- Humidity: no data
- Occlusion: no data
- Reference substance(s): no data
- Other: At 24 h the dermal bathing solution was removed and Cr concentration in the receptor fluid was determined by electro-thermal atomic absorption spectrometry.
After the experiments the skin was stored in a freezer at -25 C. Before analysis, the skin membranes were dried for 24 h at room temperature. Then the exposed area was cut into sections, weighted and digested in 70% v/v HNO3

Results and discussion

Absorption in different matrices:

No significant differences were found when measuring Cr concentrations in the receiving cells after experiments with intact or damaged skin.
The amounts of Cr found in the damaged skin after removing the skin from the test cells were significantly higher compared with the amounts found in intact skin (62.1 µg/cm versus 14.4 µg/cm2 respectively).

AAS analyses showed that Cr was present as ions in the donor phase. The concentrations of the Cr ions were similar in experimental cells with either intact or damaged skin. The evaluation of metal ion percentage for Cr showed that the skin contained 99% of the Cr ions. The authors suggested that it was likely that the synthetic sweat solution (pH 4.5) was not efficient enough to oxidise more than a small fraction of metallic chromium to soluble Cr ions.

Percutaneous absorption

Remarks on result:

other:

Applicant's summary and conclusion

Conclusions:

The in vitro dermal absorption test showed no differences in the permeation of Cr metal through intact or damaged skin barriers. A high Cr concentration was found in the damaged skin, suggesting a strong binding of Cr to skin proteins. 99% of the total Cr(III) ions were observed in the skin. It can be concluded that the skin penetration properties of chromium are very low, even in the case of damaged skin.

Executive summary:

The percutaneous penetration of chromium metal powder, and the effects of skin lesions were studied in an in vitro model. Franz diffusion cells with intact and damaged human skin were used for the tests. Cr powder was dispersed in synthetic sweat at pH 4.5 and applied as donor phase to the outer surfce of the skin for 24 h. PBS (pH 7.35) was used for the receiving phase. The amount of metal permeating or bound to the skin was analysed by electro-thermal atomic absorption spectrometry. No significant differences were observed between Cr permeation through intact or damaged skin. 99% of the Cr ions were detected in the skin samples, indicating very low skin penetration properties of chromium.