Acute increases in PM2.5 and lead constituent were associated with endothelial dysfunction (increased endothelin-1, E-selectin, and intracellular adhesion molecule-1) and inflammation (increased interleukin-1β, interleukin-6, tumor necrosis factor-α). Endothelial dysfunction and elevated inflammation were partially mediated by the effect of PM2.5 and lead constituent on blood pressure. Here, TNF is linked to endothelial dysfunction.