Ozonation of Tobacco Smoke Contaminants Embedded in Indoor Deep Reservoirs

XIAOCHEN TANG, Nicolas Lopez-Galvez, Vi Rapp, Penelope Quintana, Hugo Destaillats, Lawrence Berkeley National Laboratory

     Abstract Number: 525
     Working Group: Indoor Aerosols

Abstract
Carpets represent approximately 50% of the US residential flooring market. In environments where smoking takes place regularly, carpets and other materials can become severely contaminated with thirdhand tobacco smoke (THS), leading to exposures by inhalation, dust ingestion and dermal contact. In this study, we assessed the efficacy of ozonation as an indoor remediation strategy, by evaluating how carpet serves as a sink and long-term source of THS, while protecting contaminants absorbed in deep reservoirs by scavenging ozone. Specimens from unused carpet that was exposed to smoke in the lab (“fresh THS”), and contaminated carpets retrieved from homes occupied by smokers over the previous 6 to 25 years (“aged THS”), were treated with 1,000 ppb ozone in bench-scale tests. The concentration of nicotine embedded in the carpet specimens was measured before and after the ozone treatment. Nicotine was partially removed from fresh THS specimens by volatilization and oxidation, but it was not significantly eliminated from aged THS samples. By contrast, most of the 24 polycyclic aromatic hydrocarbons (PAHs) detected in both samples were partially removed by ozone. One of the home-aged carpets was installed in an 18-m³ room-sized chamber, where its measured nicotine emission rate was 950 ng day^-1 m^-2. In a typical home, such daily emissions could amount to a non-negligible fraction of the nicotine released by smoking one cigarette. Operation of a commercial ozone generator for a total duration of 156 min, reaching concentrations up to 10,000 ppb, did not significantly reduce the carpet nicotine loading (26 – 122 mg m^-2). Ozone reacted primarily with carpet fibers, rather than with THS, leading to short-term emissions of aldehydes and aerosol particles.