OBJECTIVE To assess the oxidative damage after exposure to fine particulate matter (PM2.5) in human umbilical vein endothelial cells (HUVECs) and to explore the influence of the Nrf2 pathway. METHODS HUVECS were exposed to different concentrations of PM2.5 as follows: 0.000 (control), 0.004, 0.039, 0.391, 1.950, 3.910, 7.810, 15.600, 31.250, 62.500, 125.000 and 250.000 μg/cm(2). After 24 h, cell viability was measured by the CCK-8 method. In a separate experiment, HUVECs were exposed to 0 (control), 1.95, 3.91, 7.81, 15.63 or 31.25 μg/cm(2) of PM2.5. The level of cellular reactive oxygen species (ROS) was detected with an H2-DCFDA fluorescence probe after 1h and 3 h exposure. After 24 h exposure, the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and malondialdehyde (MDA) content were detected by colorimetry. Western blot was used to estimate the expression levels of Nrf2 and NQO1 in total protein. RESULTS HUVEC viability was reduced in a concentration-dependent manner by PM2.5. Compared with controls (100% viability), the viability of the 250 μg/cm(2) group was (38.18±6.68)% (P<0.05). Substantial accumulation of ROS occurred in HUVEC after 1 h and 3 h exposure to PM2.5. After 24 h exposure to 0, 1.95, 3.91, 7.81, 15.63 and 31.25 μg/cm(2) of PM2.5, SOD activity decreased concentration-dependently to (26.25±1.76), (24.99±1.81), (24.25±0.49), (22.07±1.13), (21.03±0.43) and (19.37±0.84) U/mg protein, respectively, (F=13.95, P<0.001). GPx activity decreased in a concentration-dependent manner to (25.63±1.33), (24.40±2.20), (22.85±2.46), (20.98±1.95), (20.17±1.86) and (18.69±3.11) mU/mg protein, respectively (F=4.26, P=0.019), whereas MDA increased concentration-dependently to (1.11±0.07), (1.12±0.07), (1.17±0.05), (1.49±0.01), (1.95±0.08) and (2.37±0.08) nmol/mg protein, respectively, (F=186.37, P<0.001). Compared with the control Nrf2, NQO1 protein levels (1.00±0.27, 1.00±0.33), 15.63 μg/cm(2) group (2.38±0.44, 1.78±0.20) were enhanced (P<0.05). CONCLUSION These results demonstrate that PM2.5 can lead to oxidative damage to HUVEC in a concentration-dependent manner. Protein levels of Nrf2 and NQO1 were enhanced at high concentrations of PM2.5, and this mechanism may be related to increases in cellular ROS induced by PM2.5.