Pilot Study to Assess the Quantitative Dermal Transfer Efficiencies of Solids for Multiple Transfer Pathways

Overview

Dermal transfer efficiency has been defined as the amount of material that moves from one surface to another following contact. The investigators propose to measure dermal transfer efficiency for the following pathways: (1) object to skin, (2) skin to skin, (3) skin to mouth, (4) clothing to skin, (5) gloves to skin, and (6) air to skin. First, the quantitative dermal transfer will be measured for the two selected test substances (lead, Tinopal) for each of these six pathways. The relative quantities of dermal transfer will also then be compared between the different transfer pathways (e.g., is skin to skin transfer greater or less than clothing to skin transfer?). And second, the pattern of transfer will be characterized semi-quantitatively (e.g., does dermal transfer occur consistently and evenly to the skin from different reservoirs?).

Each of the six transfer pathways will be tested and measured in a controlled, ventilated study chamber at the University of Minnesota's School of Public Health Industrial Hygiene Laboratory. To test each pathway, human volunteers will perform repeated contact activities using an identical protocol (e.g., identical number of contacts, type of material contacted, measured pressure of contact, measured time of contact, measured temperature and humidity) so that inter- and intra-individual variability can be characterized. The qualitative and quantitative sampling methods that will be used have been developed, tested, and published by researchers from the National Institute for Occupational Safety and Health (NIOSH) and other institutions such as ASTM. Specifically, quantitative transfer efficiencies will be measured using accepted wipe sampling protocols taken from several papers in the peer-reviewed literature. Semi-quantitative transfer patterns will be measured using fluorescent tracer intensity techniques that have also been presented in the peer-reviewed literature. The skin surface wipe samples will be sent to an accredited American Industrial Hygiene Association (AIHA) laboratory for analysis. These sampling results will allow the investigators to report the measured quantitative dermal transfer efficiencies of elemental metallic lead and Tinopal for each pathway in mass per square surface area of skin, and also calculate the relative transfer efficiencies in terms of percent transferred versus originally loaded. Fluorescent tracer maps will allow the investigators to demonstrate the patterns of transfer for each pathway using intensity of the tracer following transfer. Following this analysis, the investigators will then use the data to better inform the relative importance of the pathways in the conceptual model with respect to dermal exposure assessment and modeling efforts. These results are very important for improving the quality of workplace dermal exposure assessments and techniques. The current approaches are not well validated, and it is unknown if the results of existing dermal exposure models are accurate. It is expected that the results of this study will help to improve the protection of workers from certain dermal exposure hazards in the workplace by providing better inputs to the existing dermal exposure models, since it is not possible to collect exposure samples for each job task in the workplace.