Exposure to PM10 is associated with cardiovascular effects. We evaluated the effects of PM10 on E-Selectin expression and monocytic cell adhesion in human umbilical vein endothelial cells (HUVECs). HUVEC were exposed to PM10 (5-40 microg/cm2) for 6 h, following which surface E-Selectin expression was detected by fluorescence microscopy and flow cytometry. The effects of total particles, particles treated with polymixin-B to block the effects of endotoxin, and both soluble and insoluble fractions of particles, were assessed. Incubation with PM10 lead to a concentration-related increase of E-Selectin expression (>seven-fold increase at 40 microg/cm2). Particles pre-treated with polymixin-B inhibited E-Selectin expression to a level slightly higher than untreated particles. An increase in fluorescence was also observed with the insoluble fraction, while the soluble fraction had no significant effect. HUVEC exposed to PM10 were also evaluated for adhesivity of monocytic cells (U937). PM10 strongly increased the adhesion of U937 cells to HUVEC. In conclusion, PM10 induces endothelial cell activation, evidenced by enhanced E-Selectin expression. This activation is manifested functionally as an increase in monocytic cell adhesion. Insoluble components as well as endotoxins appear to be responsible for this activity.