Insights into the Dermal Absorption, Percutaneous Penetration, and Tissue Distribution of Quaternary Ammonium Compounds (QACs): Evidence from Human Skin Wipes and <i>In Vivo</i> Rat Models

Humans are frequently exposed to quaternary ammonium compounds (QACs) via direct dermal contact with disinfectants and personal care products. However, the dermal exposure, skin penetration, and tissue distribution behavior of QACs remain unclear. Herein, we used human skin wipe samples and an <i>in vivo</i> rat model to explore the dermal absorption, percutaneous penetration, and exposure behaviors of 19 QACs with different physicochemical properties. QACs were frequently detected in hand wipe samples (<i>n</i> = 99), with a median total concentration of 17,200 ng/m². Females had significantly higher (<i>p</i> < 0.05) skin exposure levels to QACs than males. The application of skin care products could contribute to the dermal exposure of QACs. The skin-permeable fraction of QACs in Sprague-Dawley rats ranged from 9.09% ± 0.97% to 25.2% ± 3.89% and from 9.53% ± 0.83% to 20.5% ± 1.44% in low- (1.7 μg/cm²) and high-dose (4.2 μg/cm²) groups, respectively. The skin accumulation and penetration behaviors of QACs were associated with their log <i>K</i>_ow values, molecular weights, and chain lengths, with varied correlations among different QAC categories. Fecal excretion was identified as the main elimination route for dermally adsorbed QACs. Exposure assessment emphasized the significance of dermal exposure to QACs.