This article is part one of a three-part review that draws attention to the exposure of a large segment of the public to metal-containing compounds, potentially resulting in their unintentional absorption through the skin. Of course, both finished products and ingredients, including metal compounds, are designed to be biologically inactive and non-toxic, and are formulated to minimize their absorption. However, present knowledge of percutaneous absorption and pharmacokinetics teach that such criteria cannot be viewed in absolute terms.
The regulatory designation of cosmetics implies that they are trivial substances to be rubbed, poured, sprinkled or sprayed on, or otherwise applied to the human body with the intent to cleanse, beautify, promote attractiveness or alter the body's appearance without affecting its structure or function.17 While this makes them appear trivial, providing a certain level of comfort with respect to potential dermal toxicity, published information neither confirms nor refutes their assumed dermal bioavailability of zero.