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Estimating Contaminant Dose for Intermittent Dermal Contact: Model Development, Testing, and Application

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Abstract:Assessments of aggregate exposure to pesticides and other surface contamination in residential environments are often driven by assumptions about dermal contacts. Accurately predicting cumulative doses from realistic skin contact scenarios requires characterization of exposure scenarios, skin surface loading and unloading rates, and contaminant movement through the epidermis. In this paper we (1) develop and test a finite-difference model of contaminant transport through the epidermis; (2) develop archetypal exposure scenarios based on behavioral data to estimate characteristic loading and unloading rates; and (3) quantify 24-hour accumulation below the epidermis by applying a Monte Carlo simulation of these archetypal exposure scenarios. The numerical model, called TTDERM, allows us to account for variable exposure times and time between exposures, temporal and spatial variations in skin and compound properties, and uncertainty in model parameters. Using TTDERM we investigate the use of a macro-activity parameter (cumulative contact time) for predicting daily (24 hour) integrated uptake of pesticides during complex exposure scenarios. For characteristic child behaviors and hand loading and unloading rates, we find that a power law represents the relationship between cumulative contact time and cumulative mass transport through the skin. With almost no loss of reliability, this simple relationship can be used in place of the more complex micro-activity simulations that require activity data on one- to five-minute intervals. The methods developed in this study can be used to guide dermal exposure model refinements and exposure measurement study design.

The United States Environmental Protection Agency though its Office of Research and Development partially funded the research described here under IAG DW-988-38190-01-0 to Lawrence Berkeley National Laboratory through the US Department of Energy under Contract Grant DE-AC03-76SF00098.
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Citation:Riley, W. J., T. E. Mckone, and E. A. Cohenhubal. Estimating Contaminant Dose for Intermittent Dermal Contact: Model Development, Testing, and Application. RISK ANALYSIS 24(1):73-85, (2004).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Exposure Measurements & Analysis Branch
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Product Type: Journal
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Published: 02/01/2004
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Bullet Item Estimating Contaminant Dose for Intermittent Dermal Contact: Model Development, Testing, and Application
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Related Entries:
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Bullet Item Human Exposure Measurements Children's Focus
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