Transcutaneous metal absorption following chemical burn injury

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

The bioavailability of metals, which are known as important contact allergens, is decisive for the development and the maintenance of contact dermatitis. The aim of this study was to evaluate the percutaneous penetration of metal powders of cobalt (Co), nickel (Ni) and chromium (Cr) and the effect of skin lesions on skin absorption. In vitro permeation experiments were performed using the Franz diffusion cells with intact and damaged human skin. Physiological solution was used as receiving phase and metal powders (Co, Ni and Cr) dispersed in synthetic sweat at pH 4.5 were applied as donor phase to the outer surface of the skin for 24h. The amount of each metal permeating the skin was analysed by electro-thermal atomic absorption spectroscopy (ETAAS). Donor solution analysis demonstrated that metals were present as ions. Measurements of metals skin content were also exploited. Median Co and Ni concentrations found in the receiving phase were significantly higher when Co and Ni powders were applied on the abraded skin than after application on the intact skin (3566 and 2631ngcm(-2) vs. 8.4 and 31ngcm(-2), respectively). No significant difference was found in Cr permeation through intact and damaged skin. The measurement of metals skin content showed that Co, Ni and Cr concentrations were significantly higher in the damaged skin than in the intact skin. Co and Ni ions concentrations increased significantly when the donor solutions were applied on the damaged skin, while Cr ions concentrations did not increase. This study demonstrated that Co and Ni powders can permeate through damaged skin more easily than Cr powder, which has probably a stronger skin proteins binding capacity. Therefore, our results suggest that is necessary to prevent skin contamination when using toxic substances because a small injury to the skin barrier can significantly increase skin absorption.

The biokinetics of inorganic cobalt in the human body

This paper reviews information on the biological behavior of inorganic cobalt in humans and laboratory animals and proposes a model of the systemic biokinetics of inorganic cobalt in adult humans. The model was developed as part of an effort to update the models of the International Commission on Radiological Protection (ICRP) for addressing intakes of radionuclides by workers but is also applicable to environmental or medical exposures to inorganic forms of radiocobalt. The model can be used in conjunction with any respiratory, gastrointestinal, or wound model that provides predictions of the time-dependent feed of cobalt to blood. In contrast to the ICRP's current systemic model for cobalt, which is a simple open catenary system, the proposed model is constructed within a physiologically realistic framework that depicts recycling of cobalt between blood and tissues and transfer from blood to excretion pathways. Compared with the ICRP's current model, the proposed model yields similar predictions of whole-body retention but substantially different predictions of the systemic distribution of cobalt as a function of time after uptake to blood.

In vitro percutaneous absorption of cobalt

OBJECTIVES

To evaluate skin absorption of cobalt powder in an in vitro system. Experiments with volunteers show that cobalt powder can permeate through the skin, but there are no data with regard to the mechanism or the amount of permeation.

METHODS

Skin permeation was calculated by the Franz diffusion cell method with human skin. A physiological solution was used as receiving phase and the cobalt powder was dispersed in synthetic sweat. The amount of metal passing through the skin was analysed by electro-thermal atomic absorption spectrometry (ETAAS). Parallel polarographic analysis (differential pulse polarography-DPP) allowed evaluation of cobalt present as ions (Co(2+)) in donor and receiving phases. Measurements of cobalt skin content were also performed.

RESULTS

Evaluation of metal in the receiving phase allowed us to demonstrate the permeation of cobalt through the skin. Steady-state flow of percutaneous cobalt permeation was calculated as 0.0123+/-0.0054 microg cm(-2) h(-1), with a lag time of 1.55+/-0.71 h.

CONCLUSIONS

The experiments show that cobalt powder can pass through the skin when applied as a dispersion in synthetic sweat, oxidising metallic cobalt into ions, which permeate the skin. These experiments show for the first time how cobalt can permeate the skin.

[Methods to measure the cutaneous transfer of radionuclides across the intact or lesioned epidermis, application to radiotoxicology]

Although skin contamination by radionuclides is the most common cause of nuclear workers accidents, few studies dealing with the penetration of radioactive contamination through the skin are available. This work is a review of experimental methods that allow to assess transfer of radionuclides through the skin in occupational conditions, with or without skin trauma. The first section describes the different methods applied for skin transfer assessment of chemicals used in pharmacology. Major radionuclide contamination accidents can be associated with skin traumas. Thus, the second section describes the adaptation of these methods to radiotoxicology. Finally, the third section is an in vivo investigation of cobalt transfer (57CoCl2) through undamaged and damaged skin which simulates different industrial accident conditions (excoriation, acid or alcalin burn, scalding, branding).