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. 2025 May 23;11(21):eads7908.
doi: 10.1126/sciadv.ads7908. Epub 2025 May 21.

Personal care products disrupt the human oxidation field

Nora Zannoni  1 , Pascale S J Lakey  2 , Youngbo Won  3 , Manabu Shiraiwa  2 , Donghyun Rim  3 , Charles J Weschler  4   5 , Nijing Wang  1 , Tatjana Arnoldi-Meadows  1 , Lisa Ernle  1 , Anywhere Tsokankunku  1 , Gabriel Bekö  4 , Pawel Wargocki  4 , Jonathan Williams  1   6
Affiliations

Personal care products disrupt the human oxidation field

Nora Zannoni et al. Sci Adv. .

Abstract

People generate hydroxyl radicals (OH) in the presence of ozone via the ozonolysis of skin-emitted alkenes. In this study, we found that the application of personal care products (PCPs) including fragrances and body lotions suppresses the human oxidation field. Body lotion hampers the generation of 6-methyl-5-hepten-2-one, a key OH precursor, while many volatile ingredients of PCPs enhance OH loss in the gas phase. Although fragrances contain terpenes capable of generating OH through ozonolysis, the much larger amount of ethanol solvent acts as a large OH sink. We combined a multiphase chemical kinetic model and a computational fluid dynamics model to demonstrate how the concentrations of the reactive components develop in the indoor environment. These findings have implications for the indoor chemistry of occupied spaces and human health.

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Figures

Fig. 1.
Fig. 1.. Lotion case study.
Four young adult volunteers wearing a body lotion occupy the chamber. Ozone (40 ppb) is mixed with chamber air starting at 240 min. (A) OH reactivity. (B) Phenoxyethanol concentration. (C) 6-MHO concentration. (D) OH and O3 concentrations. All measured variables are reported in red, calculated variables are in black, and modeled results are in blue. Equations 2 and 3 for calculating the OH reactivity and OH concentrations, respectively, are shown in Materials and Methods (Supplementary Materials). The OH concentration was estimated with the steady-state method. The cyan lines represent the simulated conditions of no lotion being applied during the experiment. The estimated uncertainties on the measurements are 48% (OH reactivity), 10 to 50% (phenoxyethanol and 6-MHO), 35% (calculated OH concentration; shaded gray area), and 2% (O3).
Fig. 2.
Fig. 2.. Fragrance case study.
In part i of the fragrance case study, four young adult volunteers wearing a complex fragrance, including ethanol as a carrier, occupy the chamber. The fragrance was applied on the back of the hands of two volunteers before entering the chamber in the morning (O3-free condition) and before entering the chamber in the afternoon (O3 condition). (A) OH reactivity. (B) Ethanol concentration. (C) Sum of monoterpene (MT) concentrations. (D) OH and O3 concentrations. Red lines represent the measured values, while black lines represent the calculated values, and blue lines represent the values obtained from the kinetic model simulations. The OH concentration was estimated with the steady-state method. Cyan lines are used to indicate the resulting values from the kinetic model simulations for the case when no fragrance is applied. The estimated uncertainties on the measurements are 48% (OH reactivity), 10 to 50% (phenoxyethanol and 6-MHO), 35% (calculated OH concentration; shaded gray area), and 2% (O3).
Fig. 3.
Fig. 3.. Fragrance case study.
In part ii of the fragrance case study, four young adult volunteers wearing a complex fragrance, including ethanol as a carrier, occupy the chamber. In contrast to Fig. 2, the fragrance was applied on the back of the hands of two volunteers while in the chamber. (A) OH reactivity. (B) Ethanol concentration. (C) Sum of monoterpene concentration. (D) OH and O3 concentrations. Measured values are reported in red, calculated values are reported in black, and simulated values with the kinetic model are reported in blue. The OH concentration was estimated with the steady-state method. The cyan lines indicate the model results for the case of no fragrance being applied during the experiment. The estimated uncertainties on the measurements are 48% (OH reactivity), 10 to 50% (phenoxyethanol and 6-MHO), 35% (calculated OH concentration; shaded gray area), and 2% (O3). “O3 in” indicates the start of O3 generation, while “O3 decreased” indicates the end of O3 generation.
Fig. 4.
Fig. 4.. Fragrance case study.
In part iii of the fragrance case study, sensitivity simulations performed using the KM-SUB-Skin-Clothing model showing the impact of a fragrance containing only linalool on (A) OH reactivity, (B) linalool concentrations, and (C) OH concentrations. The red dotted line represents the measured O3 concentration during the fragrance experiment. The blue line and the dashed cyan line represent the results from the sensitivity simulations, with and without fragrance, respectively. “O3 in” indicates the start of O3 generation, while “O3 decreased” indicates the end of O3 generation.
Fig. 5.
Fig. 5.. Distribution of the human OH field when a lotion or a fragrance is applied in the room.
Human OH field with lotion (A and B) and fragrance (C and D). Spatial distributions of OH reactivity and gas-phase species under two conditions: (A) and (B) represent the scenario where lotion was applied to the exposed skin of four occupants, observed at 60 and 600 s, respectively, after O3 was introduced into the room from a perforated inlet on the floor. (C) and (D) depict the scenario where a fragrance was applied to the back of the hands of two occupants sitting in the chamber, observed at 40 and 90 s, respectively, after the fragrance application.
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