IL-6 concentrations (% of media alone control) measured by ELISA method in AMJ2-C11 cell supernatants following PM2.5 exposure of 3, 24, and 48 h from varying ambient samples (n = 2/site and time). Sampling locations are ordered from low to high (1 to 5) ambient PM2.5 concentrations. Doses (μg/mL) for cell exposure were 71.9 (site 1), 125.1 (site 2), 121.4 (site 3), 122.6 (site 4), and 151.2 (site 5). Results are presented as mean ± SEM with * and ** indicating a statistically significant difference from control (p < 0.05 and 0.001, respectively). “x” indicates time points missing from site 4 due to equipment failure during ambient PM2.5 collection