Dermal exposure assessment.

Assessing dermal exposure is a complex task. Even the most commonly used methods face fundamental problems and there are large gaps in the documentation and validation of sampling methods. Still larger uncertainties exist regarding strategies for measurement. We propose a strategy based on a conceptual model and which draws on the considerable insight gained for airborne contaminants, including EN 689 for assessing exposure by inhalation. The vast amount of air sampling data has provided good insight into the statistical properties of short-term and long-term exposure levels, which is essential for designing cost-effective exposure studies. For surface and skin contaminants an understanding of the distribution types and parameter values is only beginning to emerge. Transport rates away from the skin contaminant layer determine the 'memory' of a dermal sample and measurement principles are proposed depending on these rates. It is argued that uptake is the ultimate dermal exposure metric for risk assessment and should be the basis for devising dermal occupational exposure limits.