We don’t generally think of scented waxes as a source of air pollution. However, scented wax “melts” may expose you to pollution levels comparable to those from traffic and industrial emissions, according to new research.

A recent study published in Environmental Science & Technology Letters found that scented wax melts produced air particle concentrations similar to those from traditional candles, gas stoves, and diesel and natural gas engines—although wax melts don’t emit the same pollutants.

These particles have been linked to health risks such as asthma and atherosclerosis.

Wax melts, also known as wickless candles, are small, often scented pieces of wax that release fragrance when heated.

Vaporous fragrances, also known as terpenes, inside these wax melts cause airborne nanoparticles to form at approximately six times the rate of outdoor pollution sources.

“Scented wax melts are not traditional candles,” Aidan Charron, associate director of Earth.org, who was not involved in the study, told The Epoch Times.

Regular candles burn with a flame, while scented wax melts release fragrance when melted in a wax warmer.

About 29 billion nanoparticles per minute can be deposited in the deeper part of the lungs while scented wax melts are being actively melted, the researchers estimated. That is 2,000 times the rate of normal indoor air exposure.

Unscented wax melts didn’t release significant terpenes or trigger new particle formation.

Smoke-Free, But Not Emission Free

The study investigated the air quality effects of scented wax melts and found that within two hours of indoor use, air pollution levels could surpass an entire day of outdoor nanoparticle inhalation.

Scented wax melts are marketed as a cleaner, safer alternative to traditional candles because they’re flame-free and produce no visible smoke or soot.

The study found that wax melts, compared with traditional candles, released risky airborne particles faster, posing an inhalation risk.

Different fragrances of wax melts carry different risks. Citrus and floral or lavender scents caused larger particle growth, which lasted longer in the air, whereas minty scents such as peppermint and eucalyptus produced fewer particles because of weaker reactions with ozone.

Laura Markwardt, a building biology environmental consultant at Home Biome, who wasn’t part of the study, told The Epoch Times that both fragrance nanoparticles and outdoor pollution affect health. However, they vary in their context and concentration.

Unlike outdoor pollution, which tends to disperse, fragrance nanoparticles can accumulate indoors, leading to prolonged exposure in enclosed spaces with limited ventilation, she said.

Terpenes Can Reach Deep Into the Lungs

The researchers observed that particle formation started within minutes of turning on the wax warmer. The concentrations of these nanoparticles remained elevated while the wax was warmed and even after it was turned off.

According to the study, most of these particles will settle in the upper respiratory tract, but some can breach its barrier to enter the bloodstream and reach organs such as the liver and brain.

In a previous study, the same team found that scented products—such as essential oil diffusers, citrus-scented air fresheners, cleaning products, personal care sprays, and peeling citrus fruits—also produced airborne nanoparticles.

A previous study found that it took only 20 minutes for exposure to indoor scented products to match or exceed levels from diesel engines and propane gas stoves.

“Research shows these extremely small particles can bypass the body’s natural defense mechanisms, entering directly into the bloodstream through the lungs and reach organs throughout the body, including the brain,” Markwardt said. “When these chemicals are in nanoparticle form, their ability to penetrate deeply into the body appears to be enhanced.”

Studies have linked these airborne particles to inflammation, increased risk of atherosclerosis, and worsening asthma.

Natural terpenes can also contribute to indoor air pollution by reacting with ozone to form secondary pollutants such as formaldehyde, which can irritate the eyes and airways.

Other scented everyday items may also pose inhalation risks. A study on d-limonene, a citrus terpene found in air fresheners, shows that it rapidly reacts with indoor ozone, creating airborne particles.

Should We Avoid Fragrances?

Reducing the use of fragranced products can lower exposure to terpenes and, therefore, health risks.

“People commonly report symptoms including headaches, asthma attacks, dizziness, memory issues, irritability, and skin reactions after exposure to fragranced products,” Markwardt said.

Some people react to both natural citrus oils and synthetic versions. Those who are sensitive to only synthetic fragrances can consider using natural terpenes to create scents.

“Peeling an orange releases terpenes in their natural context, alongside other compounds that may have balancing effects,” Markwardt said. “In contrast, synthetic fragrances often contain higher concentrations of isolated terpenes or synthetic variations, mixed with undisclosed ingredients, leading to more complex, potentially problematic exposures.”

Markwardt said that when looking for safer alternatives to scented products, including candles, it’s important to understand that both synthetic and natural fragrances can release volatile compounds into the air.

She recommends removing or minimizing scented products in your daily environment, especially those with synthetic fragrances.

“These products can contribute to indoor air pollution and may affect respiratory health, hormone function, and overall well-being, particularly with long-term exposure,” Markwardt said.

Check ingredient labels to see whether products contain synthetic or natural fragrances. Avoid products containing synthetic fragrances such as phthalates or benzyl acetate. Look for labels such as “phthalate-free,” “100 percent natural fragrance,” or “made with essential oils.” However, these are not guaranteed to be pure.

Markwardt suggests trying time-tested approaches that are gentler on indoor air quality. Although they are subtler in scent, they eliminate chemical exposure.

Try simmering herbs such as rosemary or cinnamon sticks on the stovetop or placing dried citrus peels and fragrant herbs in bowls around your home. As for candles, she said that unscented beeswax candles may be a safer option.