Scented Products Cause Indoor Air Pollution On Par With Car Exhaust

An anonymous reader quotes a report from New Atlas: New research by Purdue University, the latest in a series of Purdue-led studies, examined how scented products -- in this case, flame-free candles -- are a significant source of nanosized particles small enough to get deep into your lungs, posing a potential risk to respiratory health Scented wax melts are marketed as a flameless, smoke-free, non-toxic alternative to traditional candles, a safer way of making your home or office smell nice. To assess the truth of these claims, the researchers comprehensively measured the nanoparticles formed when they warmed wax melts in their mechanically ventilated test house. The tiny house is actually an architectural engineering laboratory called the Purdue Zero Energy Design Guidance for Engineers (zEDGE) lab. Designed and engineered to test the energy efficiency of a larger building, it's full of sensors that monitor the impact of everyday activities on indoor air quality.

The researchers knew from their previous research that new nanoparticle formation was initiated by terpenes -- aromatic compounds that determine the smell of things like plants and herbs -- released from the melts and reacting with indoor atmospheric ozone (O3). They'd found that activities such as 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.

In the present study, heating the scented wax contributed significantly to the number of new particles formed in the indoor air, particularly 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 lighted candles (106 cm-3), gas stoves (105 - 107 cm-3), diesel engines (103 - 106 cm-3), and natural gas engines (106 - 107 cm-3). By comparison, there were no significant terpene emissions when unscented wax melts were heated. The researchers also examined respiratory tract deposited dose rates (RD), a useful way of studying 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). That's about 483 million particles per second. The majority of scented-wax-melt-formed particles were deposited in the upper airways. Their small size means they can migrate between cells and enter the bloodstream, potentially reaching organs such as the brain. The study was published in the journal Environmental Science & Technology Letters.

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