Cleaners react with ozone, filling homes with lung-deep nanoparticles

That lemony, piney or floral smell after cleaning is usually associated with freshness. But new research suggests that the chemistry behind some scented cleaning products can also create an invisible form of indoor air pollution. Research presented by Purdue University scientists at the American Chemical Society’s Fall 2026 meeting found that fragrance compounds released during cleaning can react with ozone indoors, rapidly producing extremely small airborne particles. The findings add to earlier research showing that terpene-rich household products can undergo chemical reactions with ozone and generate secondary pollutants indoors.The chemistry starts with familiar fragrancesMany scented cleaning products contain compounds known as terpenes and terpenoids. Ingredients such as limonene, commonly associated with citrus scents, and pinene, found in pine fragrances, can evaporate into indoor air during and after cleaning.These chemicals are not necessarily harmful simply because they are present in a cleaning product.