A NOVEL LIGHTING SYSTEM FOR THE MEASUREMENT OF DERMAL EXPOSURE USING A FLUORESCENT DYE AND AN IMAGE-PROCESSOR

A video technique is described which uses a fluorescent dye as a tracer to quantify dermal deposition of chemicals such as pesticides. The subject stands inside a dodecahedral arrangement of ultraviolet (u.v.) strip-lights, which cause a given area of dye to fluoresce with a consistent intensity over a range of spatial and angular positions within the lighting field. A special algorithm and an additional point source light enable local compensation factors to be calculated to allow for the reduction of apparent surface areas, due either to the foreshortening of surfaces angled to the camera or to the inverse square law for surfaces further from the camera. Measurements on planar surfaces prove that the algorithm performs well in a large central region inside the dodecahedral lighting field. Field trials of the system show that although the free-standing apparatus is large and rather unwieldy, when fastened inside a box van it is practicable, portable and self-contained. It is suitable for measuring exposure arising from spraying operations and can be used, but with more limited success, in studies of dipping operations.