Detection of a secondary organic aerosol tracer derived from personal care products

Decamethylcyclopentasiloxane (D-5) is frequently used in personal care products (PCPs). In the gas phase, D-5 is oxidized to form 1-hydroxynonamethylcyclopentasiloxane (D4TOH), which can partition to the particle phase. Numerous studies have reported secondary organic aerosol (SOA) formation via hydroxyl (OH) radical-initiated oxidation of D-5. It is expected that PCPs have a significant impact on SOA, but the extent has not yet been investigated. To date, no studies have reported the occurrence of PCP-derived SOA in ambient particulate matter. This study examined fine particulate matter (PM2.5) collected in Atlanta, GA and Houston, TX and determined D4TOH was present in 28 of 29 and 33 of 46 ambient PM2.5 samples, respectively. Gas chromatographic retention data in the form of the Kovats index is reported for the first time to aid others in identifying this compound in order to assess the impact of PCPs on SOA formation. The estimated concentration of D4TOH ranged from 16 to 185 pg m(-3) in Atlanta and 19-206 pg m(-3) in Houston. Synthetic musks were also detected in Atlanta and Houston PM2.5 samples, which is consistent with PCPs impacting urban air quality. Because of its specificity and demonstrated detectability, D4TOH may be useful as a tracer of PCP-derived secondary organic aerosol.

Automated summary

The study found that D4TOH and synthetic musks were commonly present in fine particulate matter collected in Atlanta and Houston, indicating a potential impact of personal care products on urban air quality. Gas chromatographic retention data reported for the first time in this study helps others in identifying these compounds to assess the impact of PCPs on secondary organic aerosol formation.