Scented wax melts, often marketed as safer alternatives to candles due to being flame and smoke-free, are not as safe for the indoor environment as initially believed, new research has shown.
Aroma compounds released from scented wax melts—cubes of wax that release a fragrance when melted in an electric wax warmer—can react with other compounds in the air indoors to form potentially toxic particles, according to a study in the journal Environmental Science & Technology Letters.
The study found that “despite being flame-free and smoke-free, scented wax melts can emit quantities of volatile organic compounds (VOCs) that are larger than those of traditional scented candles due to their higher fragrance concentration and the direct heating of wax, maximizing the melted wax surface area.”
In their study, the researchers observed 15 commercially available wax melts, both unscented and scented, in a home setting where each wax warmer left on for two hours.
Samples of air taken a few yards away from the wax melts both during and after the two-hours of use were found to contain airborne nanoparticles.
These were detected, the ACS said in a statement, “at levels that were comparable to previously reported levels for traditional, combustion-based candles.”
These particles pose a risk, they warned, as they’re small enough to pass through respiratory tissues and enter the bloodstream.
The study showed that compounds released from scented wax melts can “react with indoor atmospheric ozone to initiate new particle formation events, resulting in significant indoor atmospheric nanoparticle concentrations”
Such, the researchers warned, are “comparable to those emitted by combustion-based scented candles, gas stoves, diesel engines and natural gas engines.”
The research found that “scented wax melt-initiated NPF events can result in significant respiratory exposures, with nanoparticle respiratory tract deposited dose rates similar to those determined for combustion-based sources.”
Previous studies have shown that exposure to high levels of nanoparticles in the indoor environment can be tied to health risks, such as reduced cognitive function and an increased prevalence of childhood asthma, the ACS noted.
The new findings challenge the perception that scented wax melts represent a safer alternative to combustion-based aromatherapy.
Further research, the researchers wrote, is needed into “the toxicological properties of the newly formed nanoparticles to better understand their environmental health implications.”
The recent study comes as the global home fragrance market size, estimated to be valued at $11.12 billion in 2023, was forecast to grow at a compound annual growth rate of nine percent from 2024 to 2030, according to a report by Grandview Research.
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about air pollution? Let us know via science@newsweek.com.
Reference
Patra, S. S., Jiang, J., Liu, J., Steiner, G., Jung, N., & Boor, B. E. (2025). Flame-Free Candles Are Not Pollution-Free: Scented Wax Melts as a Significant Source of Atmospheric Nanoparticles. Environmental Science & Technology Letters, 12(2), 175–182. https://doi.org/10.1021/acs.estlett.4c00986
Read the full article here
