A UK research study has found that hazardous chemicals commonly found in aerosols, such as those produced by cooking and cleaning, can be ‘protected’ in 3D structures formed by surfactants, causing them to last longer in the air.

Led by the University of Birmingham in collaboration with the University of Bath and the Central Laser Facility at the Science and Technology Facilities Council, the new study was published in Accounts of Chemical Research and funded mainly by the Natural Environment Research Council.

The team examined how one surfactant component, oleic acid, formed complex structures at the nanoscale, and how this affected the interaction of oleic acid with other chemicals in the air.

Experiments were conducted on increasingly complex mixtures of surfactants to establish the impact of a wide range of aerosol components, the University of Birmingham said on its website on 12 September.

“Aerosols are commonly created by everyday activities such as cooking and cleaning, and with modern life seeing people spending on average 90% of their time indoors, there is an urgent need to understand how indoor aerosols are processed. Oleic acid is known to self-organise into a range of 3D nanostructures, some of which are highly viscous and can delay the ageing and thus the breakdown of key chemical components in aerosols,” Prof Christian Pfrang from the University of Birmingham, who led the work, said.

“Our complex multi-scale experimental studies intimately linked to tailored computational modelling indicate that these surfactant structures may offer an effective shield for harmful chemicals common in aerosols which could persist in the atmosphere for longer and travel much further.”

By combining laboratory and computational studies the researchers established that harmful, reactive materials could be shielded inside aerosol particles and underneath highly viscous (honey-like) shells, potentially extending the atmospheric residence times.

A wide range of experimental studies were conducted to investigate self-organisation in particles levitating in the air as well as in thin films on solid surfaces and floating on water (representing the surface of aqueous droplets which are most commonly found in the atmosphere).

These self-organised aerosols were then analysed, following the structure on the nanoscale with small-angle X-ray scattering and chemical behaviour with Raman microscopy. Complementary computer models were developed by the team to understand how surfactants could organise themselves in the atmosphere.

The researchers found that surfactants could organise themselves into different kinds of 3D structures when mixed with other aerosol components found in the atmosphere. This self-organisation significantly reduced the reactivity of the chemicals, which increased their lifetime. A crust of product material could form on the surface of the particles, protecting hazardous materials and extending the time they could persist in the atmosphere.

“The crucial question now is, how important are these processes that we have carefully quantified in the laboratory in real-life conditions … we have started to collect aerosol samples for analysis from areas where high concentrations of surfactants are to be expected, such as students’ kitchens,” Prof Pfrang said.

“More research is needed to understand how these structures act both outdoors and indoors, what this means for the quality of the air we breathe, and the impact this may have on human health.”

In the meantime, Prof Pfrang recommended opening a window while cooking and cleaning to improve ventilation.