The hazardous effects of air pollution are mainly caused by the tiny airborne particles present in the atmosphere. These particles can arise from cooking, burning candles, 3D printing, and humans being exposed to ozone.
In a new study, an international research team, including EPFL, has found that our bodies can also be the source of nanocluster aerosol emissions in places where the indoor air contains ozone. Whenever we encounter ozone, it reacts with lipids in our skin to create nanoparticles.
Previously, it was known that the human body emits particles through the skin, clothes, and respiratory activities. These particles were typically one micrometer in diameter or larger.
In this study, scientists discovered a previously unknown mechanism of particles production. They found that the particles are much smaller in size range – on the order of a few nanometers.
Ozone can be toxic at high concentrations. When it comes in contact with certain pollutants, it triggers the formation of nanocluster aerosols.
Scientists have studied this process in outdoor environments. In this study, scientists, for the first time, studied the process indoors.
Dusan Licina, a professor at EPFL’s Human-Oriented Built Environment Lab (HOBEL) in the School of Architecture, Civil and Environmental Engineering (ENAC), said, “Considerable efforts have been made to reduce indoor air pollution, such as by replacing gas stoves with induction ranges or by reducing the transport of outdoor pollutants indoors. That’s what led us to identify a new source of nanoparticle emissions: humans.”
Scientists ran experiments in a 22.5 m3 climate-controlled chamber occupied by human volunteers. The chamber was made from stainless steel. It was developed so that scientists could play with specific variables – such as temperature, humidity, and ozone levels – and measure how they affect the emission of human-derived nanocluster aerosols and the concentrations of other compounds.
In this study, scientists also learned the significance of the age of occupants and the type of clothing worn. At constant ozone concentrations, nanocluster aerosol emission rates were higher with a larger exposed skin surface area. They also found that teenagers are more likely to emit nanocluster aerosols than seniors and young adults.
Linia said, “Our study’s main contribution is that it shows, for the first time, that nanocluster aerosol emissions stem directly from skin lipid secretions in indoor areas where ozone is present. Although the specific health impacts of these particles are unknown, these particles can grow to larger particles which are linked to health issues due to their deep penetration into the human lung and even neuronal transport to the brain.”
“That’s significant enough to warrant further study into how ozone concentrations affect these emissions. It would also be interesting to see whether touching objects’ fingerprints we leave behind contribute to these emissions. Or if personal-care routines or even personal-care products play a role. In the meantime, the best thing we can do is to reduce levels of ozone in our buildings.”
- Shen Yang, Dusan Licina et al. Ozone Initiates Human-Derived Emission of Nanocluster Aerosols. DOI: 10.1021/acs.est.1c03379