Are people cleaning indoor air just by being there?

High levels of reactive molecules labelled ‘detergents of the atmosphere’ can be generated inside, by us.

People in countries across the world spend the vast amount of their time indoors – at home, work, or in transit. These enclosed spaces offer little protection from atmospheric pollution, with a number of devices – for example, solid fuel stoves – even producing pollutants inside. 

When it comes to the outdoors, at least some of the chemicals we consider pollutants disappear thanks to natural conditions, such as rainfall and via chemical oxidation. The latter relies on hydroxyl radicals (OH), which are essentially cleaning products for the air itself.

Until recently, it was assumed these barely effect indoor conditions because they are created when UV light from the sun – heavily reduced inside – hits ozone and water vapour. Now a group of scientists at the Max Planck Institute for Chemistry have discovered that OH radicals can also be generated inside, simply because people and ozone are present. 

‘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,’ says Nora Zannoni, first author of the study published in the research magazine Science, and now working at the Institute of Atmospheric Sciences and Climate in Bologna, Italy.

The oxidation field is created by the reaction of ozone with oils and fats on our kin, with unsaturated triterpene squalene – accounting for around 10% of skin lipids there to protect and retain suppleness – particularly effective. A hot gas is released by the reaction, containing various gas phase chemicals, which react with the air to create substantial levels of OH. 

Earlier this year, it was found that indoor air pollution levels can be reduced by improving ventilation, but nitrogen dioxide does not appear to be lowered in this way.

Image credit: Valeria Smirnova



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1 year ago

I still can’t see how this works. Surely people add all sorts of chemicals and particles to the air aorund them in their homes and workplaces? If these OH radicals can break down at least some of the chemicals from our bodies and breath and whatever we bring into the building, then that is very good. But do they also wipe out all the toxic particulates around us that we are inhaling? Can someone here kindly explain the science a bit more for me please?

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