Occupational dermal exposure to chemicals is known to cause a variety of skin diseases and, in the UK, the Health and Safety Executive has estimated that there are 85,000 cases of work-related skin disease at any one time. In addition, many hazardous chemicals can pass through the skin and add to inhalation exposure.

Against this background there has been considerable effort to develop quantitative methods of assessing exposure. Fenske conveniently grouped the various sampling techniques into three categories: surrogate skin techniques which rely on a collection medium placed against the subject’s skin; removal techniques where substances deposited on the skin are removed, generally by washing or wiping; and fluorescent tracer techniques that rely on the measurement of UV fluorescence from materials deposited and retained on the skin. Each of these categories of methods measures slightly different aspects of dermal exposure and has its own strengths and weaknesses. All these procedures measure mass of material on the skin surface.

However, to date, there has been little work on the biological relevance of dermal exposure sampling techniques. For example, uptake through the skin is driven by diffusion, which, in turn, is driven by the concentration of the material on the skin. In many instances, the concentration on the skin is also a better indicator of the potential of a chemical to cause direct damage to the skin. Mass may therefore not be the most appropriate measure of dermal exposure. In addition, surrogate skin samplers almost invariably retain a much higher proportion of any chemical contact than the skin. While removal techniques and fluorescent tracers tend to look at what is left on the skin rather than what can damage or penetrate the skin.

This paper will discuss the rationale for radical changes in the design of ‘surrogate skin’ dermal exposure samplers to chemicals. In addition it will describe the development and preliminary laboratory testing (funded by the Health and Safety Executive) of a prototype ‘surrogate skin’ dermal exposure patch sampler. This has been designed to measure the concentration of liquids on skin surfaces and incorporates a diffusion barrier. The diffusion barrier allows the sampler to measure concentration of contact rather than simply mass and liquid retention properties closer to those of human skin than standard patch surfaces.