Conceptual model for assessment of dermal exposure

Dermal exposure, primarily to pesticides, has been measured for almost half a century. Compared with exposure by inhalation, limited progress has been made towards standardisation of methods of measurement and development of biologically relevant exposure measures. It is suggested that the absence o f:a consistent terminology and a theoretical model has been an important ca use of this lack of progress. Therefore, a consistent terminology based on a multicompartment model for assessment of dermal exposure is proposed that describes the transport of contaminant mass from the source of the hazardo us substance to the surface of the skin. Six compartments and two barriers together with eight mass transport processes are described. With the model structure, examples are given of what some existing methods actually measur e and where there are limited, or no, methods for measuring the relevant ma ss in a compartment or transport of mass. The importance of measuring the c oncentration of contaminant and not mass per area in the skin contaminant l ayer is stressed, as it is the concentration difference between the skin co ntamination layer and the perfused tissue that drives uptake. Methods for m easuring uptake are currently not available. Measurement of mass, concentra tion, and the transport processes must be based an a theoretical model. Sta ndardisation of methods of measurement of dermal exposure is strongly recom mended.