Radioactive contaminant permeation through skin: Current understanding.

Abstract

This review presents our current understanding on the permeation of radiochemicals through intact or slightly damaged skin from studies on human volunteers, experimental animals and radiological accidents involving contamination. The typical fractional absorption through intact skin for aqueous plutonium-239 in dilute nitric acid is < 0.1%. Permeation of americium-241, cobalt-60, manganese-54 and promethium-147 is < 0.1% and cesium-137 and strontium-90 is < 1 % as dilute nitrate/chloride solution for several hours of contact with skin. Permeation up to 1-2% were found for Pu and Am through chemically injured skin and up to 10% when complexed with chelating agents such as DTPA. Iodine-125 as iodide and 99mTcO4- (technicium-99 as pertechnetate) showed permeation up to 60% through intact pig skin. The results for uranium compounds are widely varying and inconclusive, ranging from almost insignificant penetration to nearly 50% in one study. Noticeable differences were found for the permeation results obtained for the same substance through in vivo and in vitro methods, and using different skin models. The permeability of radiochemicals through human skin is in general lower than that of commonly used animal skin models such as rat, rabbit and pig. Stratum corneum is the principal barrier preventing the radionuclide entry and its damage rapidly enhances the permeation, in some cases from insignificant level for intact skin to more than fifty percentage transfer for damaged skin. Mechanisms of transfer of radiochemicals through skin are poorly understood but different characteristics of the contaminant species such as hydrophobicity, water solubility and ionic size were found to influence their transport across skin.