Whether polybrominated diphenyl ethers (PBDEs) induce effects in target cells is increasingly important given that their environmental burdens are rising. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy can be used to biochemically signature cells based on the notion that a detailed "biochemical-cell fingerprint" in the form of an infrared (IR) spectrum is derived. By employing subsequent computational approaches such as principal component analysis (PCA) and/or linear discriminant analysis (LDA), data reduction is achieved to allow for the identification of wavenumber-related biomarkers of effect Clustering of similar spectra (or scores) away from dissimilar ones highlights the variance responsible for discriminating classes. Discriminating biomarkers might include protein conformational changes, structural alterations to DNA/RNA, glycogen content, or protein phosphorylation. Employing this approach, we investigated in MCF-7 cells the dose-related effects of PBDEs (congeners 47, 153, 183, and 209), benzo[a]pyrene (B[a]P), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PHIP), 17beta-Oestradiol (E2), or lindane (gamma-hexachlorocyclohexane). Cultures concentrated in G0/G1- or S-phases were treated for 24 h. Following treatment MCF-7 cells were fixed and applied to IR reflective Low-E windows for interrogation using ATR-FTIR spectroscopy. At concentrations as low as 10(-12) M in culture, significant separation (P < or = 0.05) of PBDE-treated and vehicle control cell populations was noted. In some cases this was associated with alterations in lipid or the secondary structure of proteins; with DNA-reactive compounds (e.g., B[a]P), variance was primarily noted in the DNA/RNA region. This study points to a novel nondestructive approach capable of identifying contaminant effects at environmental concentrations in target cells.