Unlike previous studies of consumer plastics, which used single-target reporter assays, we took an unbiased approach to identify potential sources of toxicity. We used TF-FACTORIAL and NR-FACTORIAL in vitro bioassays, which measure the activation of 45 human transcription factor response elements and 24 nuclear receptors, respectively. With these assays, specific biological responses yield unique bioassay profiles that can be used to identify potential modes of action. Of the 69 endpoints measured in the bioassays, only five were activated within the range of concentrations tested. The activities of all other response elements and receptors were well below an operationally defined 1.5 fold-induction cut-off. Results were consistent across three extracts prepared from three independent sets of plastic. All activities of the extraction blank were below the induction cut-off (Figure ).