Air Inside May Be More Polluted Than Outside Due to Chemical Products

Nanoparticles form when fragrances interact with ozone, which enters buildings through ventilation systems, triggering chemical transformations that create new airborne pollutants. 

“A forest is a pristine environment, but if you’re using cleaning and aromatherapy products full of chemically manufactured scents to recreate a forest in your home, you’re actually creating a tremendous amount of indoor air pollution that you shouldn’t be breathing in,” said Nusrat Jung, an assistant professor in Purdue’s Lyles School of Civil and Construction Engineering.

Nanoparticles can penetrate deep into the respiratory system and spread to other organs. Jung and fellow civil engineering professor Brandon Boor have been the first to study nanoscale airborne particle formation indoors and compare it to outdoor atmospheric processes.

“To understand how airborne particles form indoors, you need to measure the smallest nanoparticles—down to a single nanometer,” said Boor, Purdue’s Dr. Margery E. Hoffman Associate Professor in Civil Engineering. “At this scale, we can observe the earliest stages of new particle formation, where fragrances react with ozone to form tiny molecular clusters. These clusters then rapidly evolve, growing and transforming in the air around us.”

Even though it’s yet to be determined how breathing in volatile chemicals from these products impacts your health, the two have repeatedly found that when fragrances are released indoors, they quickly react with ozone to form nanoparticles. These newly formed nanoparticles are particularly concerning because they can reach very high concentrations, potentially posing risks to respiratory health.

Jung and Boor believe these findings highlight the need for further research into indoor nanoparticle formation triggered by heavily scented chemical products. 

“Our research shows that fragranced products are not just passive sources of pleasant scents — they actively alter indoor air chemistry, leading to the formation of nanoparticles at concentrations that could have significant health implications,” Jung said. “These processes should be considered in the design and operation of buildings and their HVAC systems to reduce our exposures.”