Volatile Methyl Siloxanes (VMS) are a class of synthetic compounds ubiquitous in personal care products such as deodorant, lotion, and hairspray as well as some industrial products including waxes and sealants. Due to their high vapor pressures, most VMS compounds included in these products are eventually released to the atmosphere. Concentrations of VMS tend to be highest in densely populated urban areas due to the large emissions from consumer personal care product use. Once released into the atmosphere, VMS react with hydroxyl radicals to form oxidized byproducts. Recent laboratory studies have shown that these oxidized byproducts have the potential to form secondary organic aerosols and that, consequently, VMS emissions from personal care products may significantly contribute to urban particulate matter. However, simultaneous real-world measurements of VMS, oxidized VMS, and VMS SOA in an urban setting are needed to confirm early findings from laboratory studies and to estimate the total contribution of VMS compounds to urban aerosol formation. To address this need we conducted a field sampling campaign in New York City which is expected to have large VMS emissions due to its high population density. Composite air samples were collected over a one-month period using active air samplers and analyzed to determine the concentrations of VMS parent compounds and byproducts. In this presentation we present early results from this study including temporal trends in VMS parent compounds, factors controlling VMS oxidation, and comparisons with previous results from laboratory scale studies.

Role of volatile methyl siloxanes in urban aerosol chemistry: A case study from New York City

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