Polycyclic Aromatic Hydrocarbon Concentrations in Rental Car Dust Samples as a Measure of Thirdhand Smoke

Includes bibliographical references (pages 60-69).Environmental tobacco smoke (ETS) is a mixture of more than fourthousand chemicals, many of which are known carcinogens. Included in this mixture are polycyclic aromatic hydrocarbons (PAHs), a class of persistent, ubiquitous, semi-volatile compounds. Environmental tobacco smoke is a major contributor to indoor air pollution and may persist in contaminated air, dust, and surfaces. This persistent pollution has been termed thirdhand smoke (THS). THS pollution has been previously shown to increase PAH surface area loadings in settled house dust; however, PAH concentrations due to THS contamination have not been studied in vehicles. This thesis investigated THS pollution from PAHs in rental vehicles and explored the relationships between smoking status, rental agency type, and vehicle characteristics, and PAH concentrations in dust. Samples were collected as part of a larger study in which dust, air, and surface samples were collected from 250 vehicles sampled from both locally and nationally based rental companies in San Diego, CA. Dust samples (n=66, including 25 vehicles designated for smoking) were collected using an HSV4 Small Volume Surface Sampler. PAHs and nicotine were extracted from dust samples and analyses were performed using gas chromatography with mass spectrometry (GC-MS) for PAHs (i.e. total, acenaphthene, acenaphthylene, anthracene, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-cd)pyrene, naphthalene, phenanthrene, and pyrene) and high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) for nicotine. Geometric mean concentrations of nicotine were 31.1ng/m?? (air), 15.0??g/g (dust), and 0.9??g/m?? (surfaces), and of total PAHs 1487.3 ng/g (dust). Significant correlations were not observed between nicotine and PAH measures. In robust regression models, surface nicotine concentrations were not significantly correlated to any PAH measures. Significant negative correlations were found between PAH concentrations in dust and both odometer reading and dust weight, and a significant positive correlation was observed between odometer reading and dust weight. Robust regression modeling indicated odometer reading to be the best predictor for concentrations of total and individual PAHs, as significant negative relationships between odometer reading, total PAHs, and thirteen of the sixteen individual PAHs measured were observed. These results may indicate a complex relationship in which dust particles accumulate over time and act as diluents, hiding or thinning the true concentrations of PAHs in the sample. Vehicles frequently vacuumed would then reflect higher PAH dust concentrations as the PAHs would settle into upholstery and fabrics instead of dust particles. Additionally, PAH concentrations in newer vehicles may be partially attributed to chemicals used in the manufacturing process. It was also speculated that factors within the vehicle cabin including air conditioner use, cleaning techniques, ventilation, and direct sunlight may reduce nicotine concentrations observed in vehicle surface dust, eliminating or decreasing the relationship between nicotine and PAH measures. Further investigation is required to comprehend the complex interactions and relationships that occur between measures inside the vehicle cabins