Scented Products Cause indoor Air Pollution on Par With Car Exhaust

Using scented products indoors alters the air chemistry, generating as much pollution as car exhaust does outside, according to a new study. Researchers warn that breathing in these tiny particles could have serious health consequences.

Indoor Air Pollution from Common Household Items

When you hear or think about “air pollution,” you likely associate it with things like factories and car exhaust. That’s pollution that’s out there – outside your home. But have you considered how you may be contributing to indoor air pollution within your own living space by using seemingly harmless products like scented, non-flammable candles?

New research from Purdue University, part of a series of Purdue-led studies, examined how scented products – in this case, flameless candles – are a significant source of nanosized particles small enough to get deep into your lungs, potentially risking respiratory health.

“A forest is a pristine environment, but if you’re using cleaning and aromatherapy products filled with chemically manufactured scents to recreate a forest in your home, you’re actually creating a tremendous amount of indoor air pollution that you shouldn’t be breathing in,” said Nusrat Jung, an assistant professor in Purdue’s Lyles School of Civil and Construction Engineering and co-author of the study.

Scented Wax Melts and Nanoparticles: A Closer Look

Scented wax melts are marketed as a flameless, smoke-free, non-toxic alternative to traditional candles, a safer way to make your home or office smell nice. To assess the truth of these claims, the researchers comprehensively measured the nanoparticles formed when they heated wax melts in their mechanically ventilated test house. The small house is actually an architectural engineering lab called the Purdue Zero Energy Design Guidance for Engineers (zEDGE) lab. Designed to test the energy efficiency of a larger building, it’s filled with sensors that monitor the impact of everyday activities on indoor air quality.

“To understand how airborne particles form indoors, you need to measure the smallest nanoparticles – down to a single nanometer,” said Brandon Boor, associate professor of civil engineering at Purdue and the study’s other corresponding author. “At this scale, we can observe the earliest stages of new particle formation, where fragrances react with ozone to form tiny molecular clusters.”

Previous studies had shown the researchers that terpenes – aromatic compounds that give plants and herbs their scent – triggered the formation of new nanoparticles when released from the melts and reacted with indoor atmospheric ozone (O3). They had found that activities like mopping the floor with a terpene-rich cleaning agent, using a citrus-scented air freshener, or applying scented personal care products like deodorant inside the zEDGE house resulted in pulsed terpene emissions to the indoor air within five minutes. Conversely, using essential oil diffusers or peeling citrus fruits caused a more gradual increase in terpenes.

Heating Scented Wax and Increased Nanoparticle Formation

In the current study, heating the scented wax significantly contributed to the number of new particles formed in the indoor air, especially those smaller than 100 nanometers (nm). The resulting atmospheric concentrations were over one million nanoparticles per cubic centimeter (106 cm-3), which is comparable to concentrations emitted by traditional lit candles (106 cm-3), gas stoves (105–107 cm-3), diesel engines (103–106 cm-3), and natural gas engines (106–107 cm-3).When they heated unscented wax melts, they observed no significant terpene emissions.

The researchers also examined respiratory tract deposited dose rates (RD), a useful way to study air pollution that measures the number of particles deposited in the respiratory tract over time. They found that the new particle formation triggered by using scented wax melts indoors produced a median RD for 1.18 to 100 nm particles of 29 billion per minute (2.9 x 1010 min-1), or about 483 million particles per second. Most of the particles formed by the scented wax melts were deposited in the upper airways. Their small size allows them to migrate between cells and enter the bloodstream, potentially reaching organs like the brain.

The Need for Further Research on Inhaled Terpenes

Scientists have started exploring the impact of inhaling terpenes on human health, but they still have much more to discover, and only further research will uncover these effects.
For now, though, the study’s findings can inform building design and ventilation systems.

“Our research shows that fragranced products are not just passive sources of pleasant scents – they actively alter indoor air chemistry, leading to the formation of nanoparticles at concentrations that could have significant health implications,” said Jung. “We should consider these processes in designing and operating buildings and their HVAC [heating, ventilation, and air conditioning] systems to reduce our exposure,” said Jung.

Read the original article on: New Atlas

Read more: China’s Global Leadership Reverses Air Pollution Trends