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Scented volatile chemical products (sVCPs) are frequently used indoors. We conducted field measurements in a residential building to investigate new particle formation (NPF) from sVCP emissions. State-of-the-art instrumentation was used for real-time monitoring of indoor atmospheric nanocluster aerosol (NCA; 1–3 nm particles) size distributions and terpene mixing ratios. We integrated our NCA measurements with a comprehensive material balance model to analyze sVCP-nucleated indoor NCA dynamics. Our results reveal that sVCPs significantly increase indoor terpene mixing ratios (10–1,000 ppb), exceeding those in outdoor forested environments. The emitted terpenes react with indoor atmospheric O3 and initiate indoor NPF, resulting in nucleation rates as high as ∼10^5 cm^–3 s–1 and condensational growth rates up to 300 nm h^–1; these are orders of magnitude higher than those reported during outdoor NPF events. Notably, high particle nucleation rates significantly increase indoor atmospheric NCA concentrations (10^5–10^8 cm^–3), and high growth rates drive their survival and growth to sizes that efficiently reach the deepest regions of the human respiratory system. We found sVCP-nucleated NCA to cause respiratory exposures and dose rates comparable to or exceeding those from primary aerosol sources such as gas stoves and diesel engines, highlighting their significant impact on indoor atmospheric environments.
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Flame-Free Candles Are Not Pollution-Free: Scented Wax Melts as a Significant Source of Atmospheric Nanoparticles
Scented wax melts are being popularized as a safer, nontoxic alternative to traditional candles and incense for indoor aromatherapy. We performed field measurements in a residential test house to investigate atmospheric nanoparticle formation from scented wax melt use. We employed a high-resolution particle size magnifier-scanning mobility particle sizer (PSMPS) and a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) for real-time monitoring of indoor atmospheric nanoparticle size distributions and terpene mixing ratios, respectively. Our findings reveal that terpenes released from scented wax melts react with indoor atmospheric ozone (O3) to initiate new particle formation (NPF) events, resulting in significant indoor atmospheric nanoparticle concentrations (>10^6 cm^–3) comparable to those emitted by combustion-based scented candles, gas stoves, diesel engines, and natural gas engines. We show 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. Our results challenge the perception of scented wax melts as a safer alternative to combustion-based aromatherapy, highlighting the need for further research on the toxicological properties of the newly formed nanoparticles to better understand their environmental health implications.
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- Award ID(s):
- 1847493
- PAR ID:
- 10632937
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Environmental Science & Technology Letters
- Volume:
- 12
- Issue:
- 2
- ISSN:
- 2328-8930
- Page Range / eLocation ID:
- 175-182
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acs.estlett.4c00986
