People Produce Reactive Chemicals That Alter Their Indoor Air Chemistry

High levels of OH radicals can be generated indoors simply due to the presence of people and ozone, according to a study published in Science.

Before now, it has been assumed that the concentration of OH radicals is significantly lower indoors than outdoors and that ozone pouring in from outside is the primary oxidant of indoor airborne chemical contaminants.

The study led by the Planck Institute for Chemistry in cooperation with researchers from the USA and Denmark found that high concentrations of OH radicals were found when people were exposed to ozone in a climate-controlled chamber and were a product of a reaction with the skin oil squalene.

The experiment was conducted at the Technical University of Denmark (DTU) in Copenhagen and included four test subjects kept in a special climate-controlled chamber under standardized conditions. First, ozone was introduced to the chamber air inflow in an amount that was not toxic to people but was representative of larger indoor levels. The researchers then measured the OH levels before and during the volunteers’ stay, both with and without ozone.

The researchers found that the oxidation field is generated by the reaction of ozone with oils and fats on our skin, in particular, the unsaturated triterpene squalene, which makes up around 10% of the skin lipids that shield and maintain the suppleness of our skin, was discovered to react with ozone to produce an oxidation field.

As a result of this reaction, several gas phase compounds with double bonds are released into the atmosphere, which further interacts with ozone to produce significant amounts of OH radicals. Furthermore, the researchers individually characterized and quantified the squalene degradation products using proton Transfer Reaction Mass Spectrometry and fast gas chromatograph-mass spectrometry systems.

“The discovery that we humans are not only a source of reactive chemicals, but we are also able to transform these chemicals ourselves was very surprising to us,” says Nora Zannoni, first author of the study published in the research magazine Science and now at the Institute of Atmospheric Sciences and Climate in Bologna, Italy. “The strength and shape of the oxidation field are determined by how much ozone is present, where it infiltrates, and how the ventilation of the indoor space is configured,” adds the scientist from Jonathan Williams’ team.

These new findings have health implications for humans. Many materials and furnishings are currently evaluated for chemical emissions before being sold. However, Williams recommends testing with people and ozone. According to Williams, oxidation activities can generate respiratory irritants like 4-oxopentanal (4-OPA) and other OH radical-generated oxygenation species and tiny particles near the respiratory system, harming children and the elderly.


Source: Science Daily

Journal source: Science