The association between particulate air pollution and high-sensitivity C-reactive protein (hs-CRP) has been well documented in epidemiological studies. Periodontitis has been linked to elevated hs-CRP levels in recent studies. It is still unknown whether patients with periodontal infections are more susceptible to particulate air pollution. The aim of this study was to investigate whether particles with aerodynamic diameters of less than 2.5 mu m (PM2.5) had greater effects on increasing hs-CRP among patients with periodontal infections compared to periodontally healthy individuals. We conducted a cross-sectional study on two panels of adult subjects, 100 adult patients with chronic periodontitis and 100 periodontally healthy adults, in order to evaluate the association between particulate matter (PM) and hs-CRP. We collected blood samples from each subject, measured hs-CRP and monitored average exposure to PM2.5 over 24 h four times during 2010 to 2012. We used mixed-effects models to estimate the association between PM2.5 and hs-CRP and adjusted for cardiovascular risk factors. We found that a 10 mu g/m(3) increase in PM2.5 was associated with a 3.22% (95% confidence interval, Cl: 1.21, 523; p < 0.01) increase in hs-CRP among all adult subjects. The effect of PM2.5 in patients was significantly higher than the effect in healthy participants. In the healthy adult panel, a 10 mu g/m(3) increase in PM2.5 was associated with a 1.17% (95% Cl: 0.54, 1.80; p < 0.01) increase in hs-CRP. For adults in the patient group, a 10 mu g/m(3) increase in PM2.5 was associated with a 9.62% (95% CI: 7.05,12.19; p < 0.01) increase in hs-CRP. We concluded that personal exposure to PM2.5 was associated with increases in hs-CRP among adult subjects. The presence of periodontal disease led to a considerably increased effect magnitude by more than eight fold. (C) 2014 Elsevier B.V. All rights reserved.