Superfund Research Program
Sources of Airborne PCB Congeners
Final Progress Reports
This project examines sources of airborne PCBs. In the last year, researchers have reported several important findings about current emissions of PCBs. These findings result from large-scale and ongoing field work conducted in four locations:
- the residential regions of urban Chicago, Illinois;
- industrial regions of East Chicago, Indiana;
- rural Iowa; and
- the entire Cleveland, Ohio region.
One of the most surprising findings from the emerging dataset is the presence of PCB11 in almost all the air samples collected in the cities of Chicago and Cleveland (Hu et al, 2008). PCB11 ( 3,3’-dichlorobiphenyl) is a rather volatile compound with only two chlorine atoms. It was not a common compound in the industrial PCB mixtures sold in the United States and so was somewhat of a mystery. Follow-up studies conducted in 2009 have shown that PCBs are common contaminants in commercial house paint and are related to the use of organic pigments (Hu and Hornbuckle, in press). White and black pigments do not contain PCBs but other colors made from azo and phthalocyanine pigments often contain PCB congeners, including PCB11. It is possible that the production and use of these pigments is a major source of PCB congeners to urban air.
PCBs are common contaminants in many industrial sites throughout the Great Lakes region so it was not surprising to find PCBs in the sediments of the Indiana Harbor and Ship Canal of East Chicago, Indiana. This project conducted a large reconnaissance study of PCBs in the harbor and canal and in 2009 reported that concentrations of PCBs in the surface sediments were as high as 30 ppm (Martinez et al, in press). The PCBs found in the sediments closely resemble Aroclor 1248 - a common commercial PCB mixture used in many applications. This mixture is enriched in PCBs that have a relatively high tendency to dissolve in water and to be emitted into air. This research is determining the magnitude of potential emissions in East Chicago that originate from the PCB-contaminated sediments.
The project has examined the spatial distribution of airborne PCBs across large cities. Prior to the studies conducted by the isrp, it was not known if airborne PCBs were distributed at high concentrations throughout cities or radiated out from a central emission location. The research team has shown that PCBs are indeed found throughout Chicago and Cleveland at levels that are at least 10 times higher than background levels (Persoon et al, in press). The concentrations in the two cities are similar in magnitude but appear to be enriched in some different PCB congeners. For example, the study showed that Cleveland had somewhat higher PCB concentrations overall, but Chicago had higher concentrations of dioxin-like PCBs. Future research will examine the importance of cities as sources of PCBs deposited into the Great Lakes and accumulating in fish. This work will also be used to examine direct inhalation exposure by the Airborne Exposure to Semi-volatile Organic Pollutants Project of the ISRP.