Figure 2: Detection of reactive oxygen species (ROS) in human dermal fibroblasts exposed to Cr(VI) with or without FeSO4. Exponentially growing human dermal fibroblasts were exposed to 5 µM Cr(VI) with or without 40 µM FeSO4 as described in the Materials and methods section. The cells were stained with the fluorescent dye 5-(and-6)-chloromethyl-2’,7’- dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA), capable of detecting Cr(VI) reductive metabolites and reactive oxygen species and the nuclear dye, DAPI. The stained cells were detected by confocal microscopy and a representative field is presented. The various colors in the photographs represent the cellular level of ROS in decreasing order as follows: red > yellow > green > blue.