Scented Volatile Chemical Products: Emerging Indoor Pollutants Driving Rapid Atmospheric Nanoparticle Formation and Growth

SATYA PATRA, Nusrat Jung, Brandon E. Boor, Purdue University

     Abstract Number: 34
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Scented volatile chemical products (sVCPs), increasingly popular for indoor fragrance applications, are emerging pollutants of significant concern due to their role in indoor atmospheric nanoparticle formation and associated respiratory health risks. We conducted comprehensive indoor field measurements in a residential test house to investigate new particle formation (NPF) driven by sVCP emissions, specifically focusing on terpene-rich products, including air fresheners, personal care products, cleaning products, and scented wax melts. Using advanced instrumentation, including a particle size magnifier–scanning mobility particle sizer (PSMPS) and a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS), we measured real-time nanoparticle size distributions down to 1 nm and terpene concentrations in the indoor air. Our results consistently showed that sVCP use considerably elevates indoor terpene mixing ratios (10–1000 ppb), significantly exceeding levels observed in outdoor forest environments (<10 ppb). These terpenes react readily with indoor ozone, initiating intense NPF events characterized by particle nucleation rates approaching 10⁵ cm^-3 s^-1 and condensational particle growth rates as high as 300 nm h^-1, orders of magnitude greater than typical outdoor NPF events. Consequently, indoor nanoparticle concentrations frequently reached 10⁶–10⁸ cm^-3 during indoor sVCP use, comparable to or even surpassing nanoparticle emissions from known combustion-based aerosol sources such as candles, gas stoves, and diesel engines. Importantly, the rapid particle formation and growth associated with sVCP usage substantially enhance nanoparticle inhalation exposure, yielding respiratory tract deposited dose rates similar to or greater than those from traditional combustion-based indoor aerosol sources. Our findings demonstrate that sVCPs significantly impact indoor air quality, underscoring the urgent need for expanded toxicological evaluation and greater consideration of sVCP emissions in indoor environmental management and regulatory frameworks.