The atmospheric fate of cashmeran from fragrant volatile chemical products : emissions, sinks, indoor-outdoor transport, and ambient measurements

As transportation emissions decline due to cleaner fuels and stricter regulations, volatile chemical products (VCPs) have emerged as an increasingly important source of urban volatile organic compounds (VOCs). Fragrant VCPs contain synthetic musk compounds designed to provide a characteristic scent. However, their impacts on indoor chemistry, human exposure, and urban air quality remain poorly constrained. This dissertation investigated the sources, sinks, and transport of cashmeran through laboratory studies and field campaigns. Cashmeran was identified as the dominant musk compound in a commercial perfume using a Vocus proton-transfer-reaction time-of-flight mass spectrometer. Its reaction rate with O₃, the dominant indoor oxidant, corresponded to an 85-day lifetime at 20 ppbv. Interestingly, ozonolysis generated secondary OH, which dominated its sink and reduced its lifetime to ∼5 h. This result demonstrates that musk compounds can persist indoors and influence indoor oxidative capacity. Given this persistence, we hypothesized cashmeran could be transported outdoors. During the Toronto Halogens, Emissions, Contaminants, and Inorganic eXperiment campaign, up to 5 pptv of cashmeran was detected in urban air, with the highest linear correlation with D5-siloxane, a personal care product tracer. To further investigate indoor–outdoor transport, cashmeran emissions were monitored following perfume application onto cotton fabric. Cashmeran exhibited the slowest growth and decay among detected compounds, persisting over 5 h due to its low volatility and reactivity. As fabric surfaces acted as reservoirs, we proposed that humans wearing fragrant VCPs can transport cashmeran outdoors. Analyses of two urban datasets, the New York Investigation of Consumer Emissions and the Southwest Urban NOx and VOC Experiment campaigns, confirmed cashmeran in urban air through correlations with D5-siloxane, population density scaling, and temporal patterns consistent with human activity. Finally, emission rates were estimated for the South Coast Air Basin using usage estimates and box modelling. Experimental kinetics identified OH reaction as a dominant atmospheric sink of cashmeran. Cashmeran was further detected across four cities from ground and airborne measurements between 2021 and 2023. This dissertation establishes cashmeran as a robust tracer for fragrant VCP emissions and highlights the opportunity to incorporate musk compounds into chemical transport models to assess indoor and urban air quality.