A method based is provided for determining the toxicity of engineered nanomaterials (NM). The method comprises in vitro assays for oxidative stress associated with exposure to engineered NM, which comprise assays for: reactive oxygen species production; phase II and glutathione antioxidant molecule expression; activation of MAP and NF-kappa B kinase signaling cascades; production of cytokines, chemokines and adhesion molecules; mitochondrial perturbation and apoptosis; and cellular uptake and subcellular localization of the NM. The method further comprises in vivo assays for oxidative stress in subjects exposed to NM.