ROS assay (Invitrogen) was performed after exposure to increasing doses of MEHP (0, 0.5, 5.0, 10, 50 μM) for 10 h. Following treatment, the cells positively stained for ROS were counted using Tali™ image-based cytometer. Hydrogen peroxide (0.18 mM for 90 minutes) was used as positive control. Results indicated that there was no significant production of ROS induced by MEHP in the C18-4 cells. The counts were standardized over the vehicle control. Data are expressed as the means of 3 experiments in duplicates, and error bars represent the standard error to the mean. ** indicates a p-value <0.005.