Fragrant Smell After Cleaning May Actually Pollute Indoor Air, Researchers Warn

Fragrance Compounds React with Indoor Ozone
Generate Tens of Billions to Trillions of Nanoparticles

Particles Sized 1–30 nm Penetrate Lungs
Researchers: "Recommend Fragrance-Free Products and Ventilation"

A recent study has found that scented cleaning products can actually generate invisible ultrafine particles indoors.

According to Science Daily on the 26th (local time), a research team led by Professor Brandon Boor at Purdue University in the United States reported at the American Chemical Society (ACS) fall conference that compounds emitted from scented cleaning products can react with indoor ozone to produce large quantities of nanoparticles.

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The research team explained that not only conventional cleaning agents, but also products using plant-based essential oils, release fragrant compounds into the air. When these substances encounter ozone, very small particles are formed, some of which can enter deep into the lungs through breathing.

Professor Boor stated, "The amount of nanoparticles inhaled due to the reaction between fragrance ingredients released during cleaning and indoor ozone can be similar to, or even greater than, the exposure experienced while standing next to a busy roadway." He added that while the particle components themselves are different from those found in traffic pollution, the overall quantity of inhaled particles could be higher.

The research team has been studying the impact of cleaning products and chemical disinfectants on indoor air quality since the COVID-19 pandemic. During this process, they noted that a significant number of cleaning and disinfectant products contain strong fragrances.

Professor Boor commented, "Clean air should not necessarily smell intensely like citrus." He added, "In fact, truly clean air should have hardly any noticeable scent at all."

'Fragrance Compounds' in Cleaning Products... Increase in Indoor Ultrafine Particles

Terpenes, such as pinene emitted by pine trees (volatile aromatic compounds produced by plants), can react with ozone to form fine particles. Outdoors, terpene concentrations are low, and such reactions tend to occur relatively slowly.

However, the situation was different indoors. When scented cleaning products are sprayed or wiped, fragrance compounds evaporate from the droplets and surfaces, releasing terpenes into the air.

Cleaning products commonly use substances such as pinene, limonene (which gives a lemon scent), thymol (derived from thyme), and linalool (a lavender scent compound). During cleaning, indoor terpene concentrations can reach levels tens to hundreds of times higher than those measured in forests.

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To simulate real-life conditions, the research team used standard liquid cleaning agents with fragrances and plant-based disinfectant sprays and wipes in an experimental home on the Purdue University campus. They recreated everyday cleaning scenarios in areas with kitchens, wooden floors, and bathrooms.

As a result, even ordinary cleaning actions—such as mopping floors or spraying and wiping counters—generated tens of billions to trillions of particles, depending on the product. Most of these particles were nanoparticles or ultrafine particles, measuring only 1 to 30 nanometers (nm) in size. Because the particles were so small, they were unlikely to be detected by typical home air quality monitors. Immediately after cleaning, indoor ultrafine particle levels could temporarily exceed outdoor concentrations.

Researchers: "Ultrafine Particles May Affect the Respiratory System and Bloodstream"

Particles of this size can deposit throughout the respiratory tract, reaching deep areas of the lungs. The researchers stated that these particles could potentially cause respiratory irritation or inflammation, and some may even enter the bloodstream.

The speed of particle formation was also rapid. Only a few minutes were needed for particles to be generated and grow after the fragrance compounds encountered ozone. Professor Boor said, "By the time you finish cleaning, many nanoparticles may already have been created, and you may have already inhaled some of them."

The research team recently investigated the combined use of scented surface cleaners and germicidal far-ultraviolet (UV-C) lamps. Experimentally, the UV lamp increased ozone concentrations in the air to about 20–40 ppb as it reacted with oxygen.

As more terpenes were released from cleaners in this elevated-ozone environment, nanoparticle formation became more active. The researchers observed that the amount of particles a person could inhale under these conditions would also increase.

The research team advised that choosing products with little or no fragrance and not using multiple scented products simultaneously can help reduce exposure. When cleaning, they recommend turning on an exhaust fan or opening windows for ventilation, and avoid using ozone-generating devices at the same time as scented cleaning products.

Professor Boor emphasized, "While cleaning removes viruses and bacteria from surfaces, it may also be creating invisible air pollution at the same time. Even if you cannot see dust or smoke in the air, particles are still being formed."

This content was produced with the assistance of AI translation services.