Friction-Mediated Transfer of Low Molecular Weight Chemicals from Consumer Mats to Fabrics: Insights for Dermal Exposure.

Despite widespread recognition of dermal exposure to hazardous compounds transferred from consumer products, limited information exists on the friction-mediated transfer of low molecular weight (LMW) chemicals. These chemicals, readily soluble in skin secretions, may pose prolonged dermal exposure risks. To address the knowledge gap, we investigated the frictional transfer of chemicals (formamide, benzothiazole, p-bis(2-hydroxyisopropyl)benzene (pHPB), and bis(2-ethylhexyl) terephthalate (DEHT)) from mats to rubbing fabrics under dry and skin-secretion conditions to simulate clothing-mediated dermal exposure. Gas-phase emissions were also measured. Under dry conditions, transfer efficiencies inversely correlated with molecular weights, namely, for formamide (0.072-0.4%), benzothiazole (0.047-0.072%), pHPB (0.0054-0.035%), and DEHT (0.00037-0.0083%). Skin secretions facilitated friction-mediated chemical transfer, with the extent of facilitation correlating with log Kow. Sweat increased formamide accumulation 5.6-9.0-fold, while sebum boosted DEHT transfer up to 110-fold. Chemical transfer was amplified under intensified mechanical conditions (duration, load, and sliding speed) and modulated by mat surface roughness. In 30 min exercise simulations, formamide (an LMW chemical) transfer efficiency through friction (0.16-1.6%) was comparable to that through gas-phase emission (0.026-0.23%). These findings indicate that frictional contact is a significant pathway for LMW chemical transfer from mats to clothing, providing critical insight for dermal exposure.