Smells like clean spirit? More like health issues.

Scented cleaners dominate the household care market, with citrus, pine and floral scents heavily associated with hygiene and sanitation.

That scent of cleanliness may come at a health cost, though, according to new research.

While COVID-19 made cleanliness a top priority in countless households, researchers worry about the unseen, little-understood risks of our growing obsession with cleanliness indoors.

In research that will be presented at the American Chemical Society’s fall meeting from Aug. 23 to 27, a team from Purdue University tested scented cleaning products in a tiny model house.

Using both conventionally scented and botanical essential oil-based products, the team found that scent compounds quickly react in the air to form nanoparticles.

These nanoparticles rapidly build up and travel deep into the lungs if inhaled, contributing to respiratory system irritation and inflammation, or even potentially entering the bloodstream.

Previous research has established that terpenes emitted by plants, such as pinene from pine trees, react with ozone to create airborne nanoparticles.

However, terpene levels are lower outdoors, so particle formation occurs slowly.

Using a scented product indoors has the same effect of releasing terpenes and creating nanoparticles as the fragrance compounds evaporate from surfaces or spray droplets.

Common terpenes in cleaning liquids like pinene, limonene (in lemon scent), thymol (or thyme) and linalool (lavender) are found at higher concentrations than those outdoors.

This causes the airborne terpene levels during cleaning to reach tens to hundreds of times higher and faster than those found in a forest.

In the tiny home model, mopping, spraying countertops and wiping surfaces with scented products formed billions or trillions of particles in a matter of minutes.

The products mostly formed nanoparticles or ultra-fine particles, no more than 1 to 30 nanometers wide, a size range often missed by at-home air quality monitors but that are detrimental to health by entering airways and lungs.

“Cleaning removes viruses and bacteria from surfaces, but it can also generate invisible air pollution,” lead study researcher Brandon Boor said.

“By the time you finish cleaning up an indoor space, you’ve already formed a lot of nanoparticles and inhaled them,” he added.

And using germicidal UV-C lamps to disinfect the air may make the problem worse by creating an environment rich for nanoparticles to form by interacting with oxygen in the air and generating ozone.

This increased ozone, combined with high terpene levels from scented products, increased particle formation.

Boor had previously looked into the impact of cleaning products and chemical disinfectants on indoor environments during the COVID-19 pandemic.

The earlier study found that the use of commercial cleaners was comparable to or exceeded that of inhalation of vehicle-associated aerosols.

While scented products are used to create the feeling of cleanliness, Boor said, “Clean air should not smell like highly concentrated citrus fruit. It should not really smell of anything.”

Instead of reaching for the lavender breeze counter spray or mopping with Pine-Sol, cleaners should use low-fragrance or fragrance-free products.

Running exhaust fans or opening windows while cleaning will also help ventilate the space.