Ozone Oxidation of Cigar Smoking Products Produces Additional Ultrafine Particles

The interaction between cigar smoke and ozone, two prevalent indoor air pollutants, has garnered significant attention due to its potential to generate harmful substances with synergistic effects on human health and the environment. This study investigates the ozonolysis of cigar smoke under indoor ozone concentrations using a Teflon bag reactor, focusing on the formation of ultrafine particles (UFPs) and the role of gas and particulate phases. Particulate size distribution and chemical compositions were monitored in real-time using an Electrical Low-Pressure Impactor and gas chromatography–mass spectrometry (GC-MS). The results demonstrate that UFP formation occurs when cigar smoke is exposed to ozone levels above 10 ppb, with primary particles ranging from 0.1 to 1 μm. GC-MS analysis reveals distinct differences in the chemical compositions of the gas and particulate phases of cigar smoke and their nascent UFPs during ozonolysis. Key species such as 2,5-dimethylfuran in the gas phase and nicotine in the particulate phase are identified as crucial contributors to UFP nucleation. The study highlights the significant contribution of the particulate phase to UFP formation, exceeding that of the gas phase. Quantum chemistry and kinetics calculations elucidate the gas-phase oxidation mechanism of nicotine and other compounds initiated by their reactions with ozone. These findings provide valuable insights into the oxidative aging processes of cigar smoke and emphasize the need for further investigation into the health implications of UFPs in indoor environments.