SAMPLING AND ANALYSIS ARTIFACTS CAUSED BY ELEVATED INDOOR AIR POLYCHLORINATED BIPHENYL CONCENTRATIONS

Polychlorinated biphenyl (PCB) concentrations were measured in the ind oor air of several public buildings in Bloomington, IN. The concentrat ions ranged from 5 to 300 times higher than outdoor concentrations, an d the indoor air PCB levels were highest in buildings with the earlies t construction dates; see Figure 2. These elevated indoor air PCB leve ls have caused contamination in sample preparation as well as artifact s in sample collection. PCBs in procedural blanks in a laboratory with an indoor air PCB concentration of 6 ng/m(3) averaged 1 order of magn itude lower than those measured in a laboratory with an indoor air PCB concentration of 300 ng/m(3). Air sampling conducted on the roof of a building with high indoor a ir PCB concentrations and ro of-top venti lation gave PCB concentrations that were approximately five times abov e ambient levels. However, sampling on the roof of another building wi thout roof-top ventilation gave PCB concentrations that were not artif icially elevated. We recommend measuring the indoor air of all sample preparation and collection sites to ensure that contamination can be r ecognized and mitigated.