Association between CAP mass concentration and blood IL-6 change 3-hrs post for CAP and CAP+O3 exposures. Individual data are shown for 80 exposures. Data for FA (●) and O3 (□) are shown separately to the left. A solid regression line is shown for CAP observations (▼) and dashed line for CAP+O3 observations (◊). There was a significant positive association between PM mass concentration and IL-6 change 3-hrs after for CAP but not for CAP+O3 exposures, with significant effect modification by ozone. The 3-hr post ΔIL-6= 3-hr IL-6 minus pre-exposure IL-6. Abbreviations: FA, filtered air; CAP, concentrated ambient particle; O3, ozone; PM, particulate matter.