Influence of Temperature, Humidity, Personal Hygiene, and Clothing on the Ozonolysis of Skin Oil at the Skin’s Surface: Self Regulation

Reactions between skin oil and ozone are a substantial source of volatile organic compounds (VOCs) emitted from the human body, yet factors influencing these reactions and emissions have only recently begun to be investigated. In this study, we conducted single-person chamber experiments involving three volunteers to systematically assess the influence of various factors, including temperature, relative humidity (RH), personal hygiene (bathing frequency and clothing soiling), and clothing coverage. We found that chamber air temperature and RH, within the range of 22–31 °C and 40–70% respectively, had negligible effects on ozone-driven VOC emissions, likely due to the body’s regulation of its surface temperature and humidity. This finding contrasts with the pronounced RH dependence reported for ozone reaction with skin oil constituents or skin-oil-soiled materials in the absence of such surface regulation. Refraining from changing clothes for 3 days increased the total emissions of key products by ∼25%, while refraining from showering for 3 days showed minimal effect, likely because skin oil on body surfaces rapidly re-equilibrates. In addition, compared with wearing freshly laundered t-shirts and shorts, wearing clothing that covered more of the body decreased the summed surface yield by nearly 50%. These findings provide new insights into skin oil chemistry adjacent to the body, highlighting the body’s role in regulating the surface environment where exogenous chemistry occurs. The results suggest that a simple model that does not account for variations in bathing frequency, indoor air temperature, and humidity, might be sufficient to describe ozone-dependent dermal emission of VOCs.