Rooms with scents of citrus, pine, or flowers are often perceived as clean, but such aromas can actually indicate chemical processes occurring in the air. Research has shown that aromatic compounds released by both conventional cleaning agents and products based on essential oils can quickly react indoors and form nanoparticles. When inhaled, some of these tiny particles can penetrate deep into the lungs.

Nanoparticle Formation During Cleaning

During cleaning and disinfecting surfaces, the concentration of terpenes and terpenoids can rapidly increase (10–1000 ppb), often exceeding levels found in forests. These compounds react with indoor oxidants, especially ozone, leading to the intensive formation and growth of nanoparticles. The recorded rates of nucleation and particle growth are significantly higher than typical outdoor values, resulting in temporary indoor nanoparticle concentrations of 10⁵–10⁸ cm⁻³. Rapid particle growth allows them to reach sizes that efficiently deposit throughout the human respiratory tract, leading to inhaled doses comparable to or even exceeding those from exposure to vehicle emissions.

The Impact of Scented Products

Scented cleaning products release terpenes when aromatic compounds evaporate from sprayed droplets or cleaned surfaces. Such liquids often contain compounds like pinene, limonene, thymol, and linalool. Their concentration during cleaning can be tens or even hundreds of times higher than outdoors. Common actions like mopping floors, spraying products on countertops, and wiping surfaces with scented products can generate billions or trillions of particles—their number depends on the product used. Most of these are nanoparticles or ultrafine particles measuring 1–30 nanometers, which are often not detected by household air quality sensors.

The Role of Ozone and Additional Factors

Using scented cleaning agents together with devices that generate ozone (such as bactericidal UV lamps) creates especially favorable conditions for nanoparticle formation. Experiments have shown that indoor ozone concentrations can rise to 20–40 parts per billion, comparable to outdoor ozone levels. When both ozone and terpenes are present at high levels, nanoparticle formation becomes even more intense.

Recommendations for Reducing Exposure

To minimize the impact of secondary air pollution during cleaning, it is recommended to:

• Use products with low fragrance content or that are fragrance-free.
• Avoid using multiple scented products at the same time.
• Turn on exhaust fans or open windows for ventilation.
• Do not use scented cleaning agents together with ozone-generating devices, such as UV lamps.

Conclusion

Scented volatile chemical products, including plant-based cleaning agents and disinfectants, are widely used indoors and are a major source of reactive organic emissions. Their role in shaping indoor atmospheric chemistry and nanoparticle formation is still not fully understood. While cleaning and disinfecting surfaces removes viruses and bacteria, it can also create invisible air pollution—even when there is no visible dust or smoke. These findings highlight the importance of ventilation, air purification, and improving product formulations to reduce the impact of secondary pollutants.