Use of historical PCB aroclor measurements: Hudson River fish data

Modern analytical techniques allow the resolution of most individual polychlorinated biphenyl (PCB) congeners; however, analysis of long-term trends in concentration and calibration of environmental fate and transport models often must rely on older, packed-column quantitations against Aroclor standards. These quantitations were often based on a limited set of chromatogram peaks, and methods may have changed over time. It is essential to be wary of false signals in the historical record resulting from changes in analytical schemes. Using an extensive database of historical packed-column quantitations relative to Aroclor standards in Hudson River fish, coupled with recent capillary-column quantitations of PCB congeners, we demonstrate that certain apparent changes in the historical record of PCB Aroclor concentrations are, in fact, partly attributable to changes in quantitation methods. We then offer techniques to ''translate'' reported Aroclor concentrations to a single, consistent basis. These corrections are essential to a valid interpretation of the historical record of PCB contamination in the Hudson River.