In 2022, a team led by the Max Planck Institute for Chemistry discovered that high levels of OH radicals can be generated inside, simply due to the presence of people and ozone. This means: people generate their own oxidation field and change the chemistry of the inner air around them within their own personal space. Now, in a follow -up study again in cooperation with an international research team, they found that commonly applied personal care products substantially suppress the production of OH radicals of a human. These findings have implications for interior chemistry, the air quality of occupied spaces and human health, since many of the chemicals in our vicinity are transformed in this field.
- People inside generate an oxidation field consisting of hydroxyl radicals (OH). The oxidation field is generated by reaction of the ozone with oils and fats in our skin
- Researchers have now found that the application of personal care products, such as fragrances and body lotions, suppresses the human oxidation field.
- The body lotion makes it difficult to generate a key precursor of OH to act as a physical barrier between the air ozone and the scialene of the skin.
- A large amount of ethanol solvent in fragrances acts as an OH sink that leads to a reduction of the OH field generated by humans.
- Methods used: a multiphasic chemical kinetic model and a computational fluid dynamic model to demonstrate how the concentrations of the reactive components in the inner environment develop.
The interior environment contains multiple sources of chemical compounds. These include continuous emissions of housing materials such as furniture, floors and furniture, but also periodic intense emissions of human activities such as cooking, smoking and cleaning. Outdoor air chemicals can also enter interior environments through infiltration and ventilation. Ozone (or3) From outdoors you can react with interior compounds to create a complex chemical cocktail within the inner life space. Since people spend up to 90 percent of their time indoors, exposure to this wide range of chemical compounds for prolonged periods is a matter of concern, particularly because the human health impacts of many of these chemicals remain little known.
On the basis of its findings in 2022, the Jonathan Williams research group of the Max Planck Institute for Chemistry had a closer look on how the human oxidation field could be influenced by personal care products. “Since the human oxidation field influences the chemical composition of the air in the breathing area and near the skin, it affects our intake of chemicals, which in turn affects human health. Therefore, it is interesting to examine how personal care products can influence the strength and spatial extension of the self -generated field,” explains Jonathan Williams.
The experimental measurements made by the Max Planck team were supported by Manabu Shiraiwa and his team at the University of California (Irvine, USA) and the Donghyun Rim group of the State University of Pennsylvania.
“Our team adopted a unique approach to simulate chemical compounds near humans in the inner environment,” said Shiraiwa. “We develop a state-of-the-art chemical model that can simulate ozone reactions with human skin and clothing that can lead to the formation of semi-volatile organic compounds.”
“We apply a three -dimensional model of computational fluid dynamics to simulate the evolution of the oxidation field around the human occupants,” Rim said. “This integrated modeling approach highlights the impact of personal care products in the field of human oxidation.”
Personal care products affect the human oxidation field
First, the researchers examined how the application of body lotion affects chemistry in the periphery of proven people. Then they investigated, how the perfume applied to the skin affects the chemical composition of the inner air. For both cases, Williams and his team saw that the concentration of OH around the volunteers decreased. This means: decreased compared to the standard case without cosmetics, where ozone reacts on human skin to form gas phase products that react again in the air with ozone to do OH.
Regarding the perfume, the researchers explain the decrease of OH with the Ethanol Primary Perfume component: it reacts with OH, using it, since ethanol does not produce OH when it reacts with ozone.
“As for the body lotion, we can explain the decrease in two ways. One is that the phenoxietanol, a chemist in the body lotion, reacts with OH but does not generate OH with ozone. This is the same as the perfume with ethanol. The second explanation is simply that the body lotion is entered in the ozone path reacting with the broom in the skin, the atmospheric chemical affirms Jon Williams.
“The application of a fragrance and a lotion together showed that fragrances affect the reactivity and concentration of OH shorter time periodsWhile the lotions show more persistent effects, consisting of the emission rate of organic compounds of these personal care products, “summarizes Nora Zannoni, first author of the study published in the Research Magazine magazine Scientific advances. He currently works at the Institute of Atmospheric Sciences and Climate in Bologna, Italy.
Implications for interior chemistry
Although there are thousands of different fragrances and lotions in the market, there are some general conclusions valid for any product that the international research team draws based on their evidence:
After the new findings of this study, it would be expected that a fragrance applied inside supplies the personal field of human oxidation. In contrast to fragrances, lotions have more variable compositions. Despite their variable composition, they expect most of the lotions to suppress the human oxidation field due to a combination of dilution of the skin oil components and a reduced interaction between or3 and the skin. In addition, marketed lotions contain preservatives that act as antimicrobial agents. Widely used is phenoxietanol that contributes even more to suppress the human oxidation field by reacting with OH radicals as demonstrated experimentally in this study.
“If we buy a furnite cornniture sofa, the harmful emissions are tested before being put on sale. However, when we sit on the couch, we naturally transform some of these emissions due to the oxidation field that we generate. This can create many additional compounds in our breathing area whose properties are not well known or studied. Curiously, the body of the lotation and the perfume seem Jonathan.
These findings are part of the ICHEAR project (Human Emissions and Reactivity Project of the Indoor Chemical) that brought together a group of International Collaborating Scientists from Denmark (DTU), USA UU. (University of Rutgers) and Germany (MPI). The modeling was part of the Irvine Moccie project at the University of California and the State University of Pennsylvania. Both projects were financed by subsidies from the AP Sloan Foundation.
Additional information
Experimental configuration in a climatic camera
The experiments were carried out at the Technical University of Denmark (DTU) in Copenhagen in 2021. Four test subjects remained in a special camera controlled by the climate in standardized conditions. The ozone was added to the entrance of the chamber air in an amount that was not harmful to humans, but representative of the highest range of interior levels. The team determined the concentrations of OH indirectly quantifying the individual OH sources and the general loss rate of OH. The OH field was only generated when the ozone was present.
When combining air measurements from within the camera with model simulations, they calculated the effect of the lotion and fragrance in the human oxidation field.