title: Dermal uptake directly from air under transient conditions: advances in modeling and comparisons with experimental results for human subjects.
abstract: To better understand the dermal exposure pathway, we enhance an existing mechanistic model of transdermal uptake by including skin surface lipids (SSL) and consider the impact of clothing. Addition of SSL increases the overall resistance to uptake of SVOCs from air but also allows for rapid transfer of SVOCs to sinks like clothing or clean air. We test the model by simulating di-ethyl phthalate (DEP) and di-n-butyl phthalate (DnBP) exposures of six bare-skinned (Weschler et al. 2015, Environ. Health Perspect., 123, 928) and one clothed participant (Morrison et al. 2016, J. Expo. Sci. Environ. Epidemiol., 26, 113). The model predicts total uptake values that are consistent with the measured values. For bare-skinned participants, the model predicts a normalized mass uptake of DEP of 3.1 (μg/m2)/(μg/m3), whereas the experimental results range from 1.0 to 4.3 (μg/m2)/(μg/m3); uptake of DnBP is somewhat overpredicted: 4.6 (μg/m2)/(μg/m3) vs. the experimental range of 0.5-3.2 (μg/m2)/(μg/m3). For the clothed participant, the model predicts higher than observed uptake for both species. Uncertainty in model inputs, including convective mass transfer coefficients, partition coefficients, and diffusion coefficients, could account for overpredictions. Simulations that include transfer of skin oil to clothing improve model predictions. A dynamic model that includes SSL is more sensitive to changes that impact external mass transfer such as putting on and removing clothes and bathing.
authors.affiliation: Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, USA.
authors.forename: G C
authors.initials: GC
authors.lastname: Morrison
authors.affiliation: Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA.|Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Lyngby, Denmark.
authors.forename: C J
authors.initials: CJ
authors.lastname: Weschler
authors.affiliation: Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Lyngby, Denmark.
authors.forename: G
authors.initials: G
authors.lastname: Bekö
mesh_terms: D000328:Adult; D016902:Air Pollution, Indoor / Q000032:analysis*; D003020:Clothing; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D010795:Phthalic Acids / Q000032:analysis / Q000493:pharmacokinetics; D035842:Research Subjects; D012869:Skin Absorption; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D010795:Phthalic Acids; D055549:Volatile Organic Compounds; C032279:phthalic acid
keywords: Clothing; Dermal uptake; Exposure model; Phthalates; Skin lipids