.In the Natick case, the court addressed the issue of whether polychlorinated biphenyl (PCB) contaminants were impermissible food additives. The court stated that if “the food placed in or to be placed in the paper container is or will be insulated from PCB migration by a barrier impermeable to such migration, so that contamination cannot reasonably be expected to occur, the paperboard would not be a food additive.” Structural analysis using the anticipated conditions that a package will be exposed to or migration testing can be used to establish that a true barrier exists.