The U.S. Toxic Substances Control Act (TSCA) plays a critical role in regulating chemicals to safeguard human health and the environment. Its 2016 amendment expanded the U.S. Environmental Protection Agency’s (EPA's) authority to fill regulatory and data gaps, requiring testing and data collection for chemical exposures—including dermal exposures in workplaces.
Dermal chemical exposures may be prevalent in the workplace; however, assessing them is typically more challenging than evaluating inhalation exposures. Guidance on empirical measurement of dermal exposure is limited, and there are few standardized methods for estimating dermal exposures. Methods for identifying and quantifying dermal exposure include, but are not limited to, direct dermal removal methods (e.g., hand rinses and dermal wipes), interception methods (e.g., cotton gloves and dermal patches), surface sampling, and in situ methods (e.g., tracer materials and fluorescence techniques).
In 2021 EPA issued several test orders under Section 4 of TSCA to gather data on chemicals undergoing risk evaluation. These orders included requirements for dermal wipe sampling to assess occupational exposure. Two flame-retardant compounds, tetrabromobisphenol A (TBBPA) and triphenyl phosphate (TPP) were included in EPA’s 2021 TSCA Section 4 test orders for dermal exposure data. The TBBPA and TPP test orders requested recipient companies follow the general method EPA provided as well as procedures outlined by Estill et al. (2020), which was adapted from methodology published by La Guardia and Hale (2015). However, these methods had not been formally validated, and these studies did not evaluate factors affecting collection efficiency (i.e., the most appropriate wipe materials or number of times the skin should be wiped). These methodological gaps left test order recipients in need of a validated and reproducible method to produce robust data for submission to EPA.
An article published in the Journal of Occupational and Environmental Hygiene in March 2025 titled “Dermal wipe sampling method development and validation for semivolatile and nonvolatile flame-retardant compounds TBBPA and TPP for use in occupational exposure assessments” describes the work of a consortium of companies, two laboratories, and Integral Consulting to fill the methodological gap for these two chemicals. The analytical method study involved testing the recovery efficiency of the test compounds in 100% isopropanol from two wipe media (cotton and polyester-rayon blend) using gas chromatography mass spectrometry. The polyester-rayon wipes had a higher extraction efficiency than the cotton wipes. Samples taken from both materials were stable up to 28 days when refrigerated and had relatively high cumulative test compound recoveries, particularly for TBBPA. In a second study, the dermal wipe sampling method was tested and validated using porcine skin as a surrogate for human skin. A primary objective was to determine the wiping pattern and number of wipes needed to ensure high recovery of test material applied to skin. These studies provide a framework for validation of commercial analytical methods and dermal sample collection methods that should be applicable for other semivolatile and nonvolatile chemicals.
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