Humans produce their own oxidation domain. Where did it come from and why?

Statistics show that we spend 90% of our lives indoors – at home, in the office or on transportation. In such conditions, we are exposed to many chemicals from different sources, such as pollutants or pathogens (bacteria and viruses).

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The air we breathe is naturally purified by hydroxyl radicals (OH) – highly reactive molecules also known as “air cleaners,” which are formed by the reaction of UV rays, ozone and water vapor. But in confined spaces, the process is not very effective. The sun’s rays are largely filtered through glass windows, and it is assumed that the concentration of hydroxyl radicals is much lower indoors than outdoors, and ozone entering from outside is the main oxidizing agent of chemical pollutants in the air.

It has been discovered that high levels of OH radicals can be generated indoors – simply due to the presence of humans and ozone. Show it to the team Led by the Max Planck Institute for Chemistry In collaboration with scientists from the USA and Denmark. Details are described in the magazine Sciences.

Nora Zannouni, lead author of the study, says:

It was surprising to discover that we humans are not only the source of reactive chemicals, but that we are also able to transform them ourselves. The strength and shape of the oxidation field is determined by how much ozone is present, where it penetrates, and how the ventilation of the interior space is formed.

What is the oxidation domain?

The oxidative field is formed by the interaction of ozone with the oils and fats on our skin, especially squalene, which makes up about 10% of the skin’s lipids, protecting it and ensuring its elasticity. This reaction releases several gas-phase chemicals that contain double bonds, which react further in air with ozone, generating large amounts of hydroxide radicals. These squalene degradation products have been individually characterized and quantified using proton transfer mass spectrometry, flash gas chromatography and mass spectrometry systems.

The experiments were conducted at Denmark Technical University (DTU) in Copenhagen. Four subjects were placed in a special climate-controlled room under standard conditions. To understand what the human-induced redox field looks like, we combined the results of a detailed multiphase kinetic model from the University of California, Irvine with a computational fluid dynamics model from Penn State University. The scientists examined how the human-generated OH field changed under different aeration and ozone conditions, apart from those tested in the laboratory. It was clear from the results that OH roots were present in abundance and formed strong spatial gradients.

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a. Manabu Shiraywa of the University of California, Irvine says:

Our modeling team is the first and currently the only group that can integrate chemical processes between skin and indoor air, from molecular to room scales. The model shows the measurements – why OH is generated from interactions with the skin.

The new discovery also has implications for our health – currently, chemical emissions of many materials and home furnishings are tested separately before they are put up for sale. However, it is also advisable to perform the test in the presence of humans and ozone.