We present a study of the seasonal and diurnal variability of carbon monoxide and selected volatile organic compounds in the Los Angeles area. Measurements were made during four different nine-day field campaigns in April/May, September, and November, 2007, and February, 2008, at the Mt. Wilson sampling site, which is located at an elevation of approximately 1700 m in the San Gabriel Mountains overlooking Pasadena and the Los Angeles basin. The results were used to characterize the Mt. Wilson site as a representative location for monitoring integrated Los Angeles basin emissions, and, by reference to carbon monoxide emissions, to estimate average annual emissions. The considerable seasonal variability of many hydrocarbons, in both their measured mixing ratios and their relationship to carbon monoxide, was indicative of variable source strengths. Most interestingly, perturbation of C4 hydrocarbon ratios suggested an enhanced role for chlorine chemistry during the month of September, likely as the result of Los Angeles' coastal location. Such coastal influence was confirmed by observations of enhanced mixing ratios of marine halocarbons, as well as air mass back trajectories. © 2010 Elsevier Ltd.

The relationship of exhaled ethane and n-pentane to exhaled NO, carbonylated proteins, and indoor/outdoor atmospheric pollutants were examined in order to evaluate ethane and n-pentane as potential markers of airway inflammation and/or oxidative stress. Exhaled NO and carbonylated proteins were found to have no significant associations with either ethane (p = 0.96 and p = 0.81, respectively) or n-pentane (p = 0.44 and 0.28, respectively) when outliers were included. In the case where outliers were removed n-pentane was found to be inversely associated with carbonylated proteins. Exhaled hydrocarbons adjusted for indoor hydrocarbon concentrations were instead found to be positively associated with air pollutants (NO, NO(2) and CO), suggesting pollutant exposure is driving exhaled hydrocarbon concentrations. Given these findings, ethane and n-pentane do not appear to be markers of airway inflammation or oxidative stress.