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Development of a Data Acquisition System for the Measurement of Residue Transfer Coefficient

Abstract

Surface residue transfer coefficients (SRTC’s) are used in the quantification of dermal exposure to chemicals (e.g., pesticides). A SRTC is the percentage of the chemical residue that transfers from a surface to the human skin during contact. This paper describes the design and construction of a data acquisition and control system used to measure these SRTC’s in a controlled apparatus. The system utilizes the PC-based LabVIEW software program to calibrate, monitor, and control contact time and pressure between a skin sample and a pesticide-laced surface via a pneumatic system. The data acquisition system records all sensor information over the user-specified contact time and pressure.

Introduction

In this paper, we present the progress of the design and construction of a data acquisition and control system used in an apparatus to measure surface residue transfer coefficients (SRTC’s). The apparatus is part of a larger research effort by the second author to understand and quantify young children’s dermal exposure to pesticides in and around home. STRC’s when combined with residue concentrations and contact date (i.e., frequency and duration of contact) will provide estimates of the mass loading of a chemical on the human skin over time. In general, the study of STRC’s provide a basis for better understanding of the dynamics of chemical transfer. Additionally, the apparatus and its associated data acquisition and control system can be used in the study of other chemicals (e.g., metals) and other exposure scenarios (e.g., contact with cleaning agents).

Previous attempts have been made to determine STRC’s of pesticides and other chemicals from various surfaces to the human skin by developing and employing techniques to perform the contact. Some of the techniques used in previous studies include PUF (polyurethane foam) and CDFA (California Department of Food and Agriculture) rollers 1, 2, the Drag Sled 3, wipe sampling 4, 5 and the foliar wash technique 6. Other residue transfer experiments have used adult human subjects to perform the dermal contact with surfaces. For example, human subjects wear cotton dosimeter clothing and act out scripted activities (Jazzercise) contacting treated carpets and floors 2, 7. Other times human hand presses, with the skin or with cotton gloves have been used to measure chemical transfer 8, 9.

These studies have produced residue transfer coefficients that range from 0.1% to 35%. The variation in residue transfer coefficients between studies is not surprising. In general, the surface residue transfer measurement techniques used lack reproducibility, consistency, and accuracy for a number of reasons. There is variation in the sampling devices (e.g., rollers, hand presses) and sampling media (e.g., polyurethane, cotton gloves) used. The sampling devices may produce varied contact pressures on the sampling surfaces and the sampling media may exhibit different absorption/adhesion characteristics. Previous studies also use varying contact times and lack detail in other experimental factors (e.g., environmental conditions and interactions between surfaces, chemicals and sampling media).

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Johnson, W., & Ferguson, A., & Hager, P., & Sanou, A., & Shenoda, D. (2006, June), Development Of A Data Acquisition System For The Measurement Of Residue Transfer Coefficient Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--1368