Superfund Research Program
Sources of Airborne PCB Congeners
Final Progress Reports
The Aims for Atmospheric Sources of PCB Congeners have been modified to accommodate a funding level 14% lower than proposed. To accommodate this reduction, the project has reduced long term monitoring in East Chicago, Indiana, and Columbus Junction, Iowa, although the project continues to examine release of PCBs from Indiana Harbor sediments. In 2014, researchers discontinued air sample collection in the City of Chicago and moved funding from sample collection to sample analysis and interpretation.
Studies and Results:
Aim 1 is to determine the sources and fate of airborne PCB congeners in the urban/industrial complex of Chicago and other urban-industrial areas. In 2014, researchers applied the previously developed model of passive air sampling to estimate hourly sampling rates for PCBs and a range of other semi-volatile compounds at urban and regional scales, and used these results to estimate PCB concentrations at ambient and reference temperatures. The development of an uptake model for determining the flow rate of PCBs accumulating on polyurethane foam passive samplers has been a major accomplishment (Petrich et al., 2013). Since its publication, researchers have used the model to determine the sample volume for all passive sampling efforts, including determining the emission of PCBs from the city of Chicago.
In 2014, researchers collaborated with Indiana University to evaluate the presence of other air toxics in the Chicago air shed. Researchers sent Indiana air samples that were dual-located with their samples. Indiana University researchers analyzed these samples for brominated flame retardants, polycyclic aromatic hydrocarbons, chlorinated pesticides and other semi-volatile organic pollutants. Center researchers analyzed the other sample at each location for PCB congeners and synthetic musk fragrances. The work with Indiana was funded by the U.S. EPA Great Lakes National Program Office.
In 2014, in collaboration with the Analytical Core and the Synthesis Core, researchers began analyzing air samples from Chicago for hydroxylated PCBs with the hypothesis that these compounds were not only metabolic products of PCBs, but also present in the environment. This hypothesis stems from the 2013 discovery that OH-PCBs were present in the original Aroclor mixtures, and as a result, contaminate legacy spills of those Aroclors. Researchers reported finding OH-PCBs in the sediments of Indiana Harbor and Ship Canal – a system they have previously shown to be heavily contaminated with Aroclor PCBs. This discovery has led to the current study of the fate of OH-PCBs in the environment. Researchers expect this to result in at least one new publication this year.
Aim 2 is to characterize the sources and environmental exposure to airborne non-Aroclor PCBs. Non-Aroclors continue to be of great interest. Researchers have shown that PCBs are produced inadvertently during chemical manufacture of several commonly used pigments. Furthermore, researchers have shown that this is a major source of some PCB congeners to the atmosphere. In Chicago, the non-Aroclor PCB11 (a PCB with two chlorines) is the most commonly detected PCB in air. Non-Aroclors are not new the environment, just newly detected. Researchers have measured these compounds in dated sediment cores and have shown they have been in the environment for almost 100 years. An urban inventory for Chicago will provide a first-ever high-resolution estimate of PCB-11 emissions from organic pigments found in commercial paint. While PCB 11 from paint application is a negligible source in Chicago, it is responsible for 3-15% of total estimated annual ∑PCB emissions from all sources.
Aim 3 is to characterize the emission and fate of airborne PCBs in the Indiana Harbor and Ship Canal (IHSC). In previous studies, researchers determined that the IHSC is a source of PCBs to the air above it (Martinez et al., 2010). However, how PCBs are dispersed and transported into the atmosphere after they have been emitted from the IHSC is unknown. To determine the fate of airborne PCBs emitted from the IHSC, researchers have modeled the local meteorological conditions in a fine grid scale (1.3 km) using the Weather Research and Forecasting Model (WFR) and predicted the PCB emission rates using an EPA air dispersion model, AERMOD. Results show that the IHSC is not only a source of airborne PCBs to East Chicago, but also to Lake Michigan. Researchers also found a strong effect of the local meteorological conditions into the dispersion and transport of these chemicals during the year. Martinez et al., 2010, shows results of the prediction for 2008. For this year, the local community and Lake Michigan were both affected from PCB airborne emissions from the IHSC.
To support the modeling of release from the IHSC, researchers investigated the distribution of PCBs between the sediment and the sediment pore water. Researchers demonstrated that even though there are high levels of black carbon in the sediments (probably coal and soot), the ratio of PCB concentrations between the sediment and pore water is low compared to other anthropogenic-impacted sediments around the world; meaning the sediment pore water concentrations are higher than expected given the concentrations in the bulk sediment and the organic and black carbons content of the sediments.
Discoveries of the fate and sources of airborne PCBs and related compounds continue. In recent years major discoveries include the finding of high concentrations of non-Aroclor PCBs that researchers linked to the inadvertent production of PCB congeners in household paint pigment. Last year, researchers reported their discovery that OH-PCBs were not only products of metabolism but are also present in Aroclors and in sediments contaminated with Aroclors. This year, researchers expect to show that OH-PCBs are also found in urban Chicago air, and that their presence is a result of photolysis of PCBs and volatilization from legacy Aroclor stocks. The significance of these discoveries includes identification of potential health hazards for urban and industrial environments. This work has influenced new toxicological studies necessary to understand these hazards.
Plans to Address Specific Aims:
Over the next year, researchers will continue laboratory studies of sediment pore waters and field studies of PCB release from IHSC sediments. Researchers will publish the urban inventory of PCBs in Chicago, and combine it with Census and land use history data in GIS to quantitatively link regions of elevated concentrations with industries or activities that handled PCB technical mixtures or used building materials like paint that contain inadvertently produced PCBs.
For Aim 2, researchers will continue to investigate the sources and release of non-Aroclor PCB congeners. They will use methods developed for OH-PCBs in collaboration with the Analytical Core and the Characterization of Exposures of Urban and Rural Cohorts to Airborne PCBs project, and apply them to determination of these compounds in Chicago air. Researchers suspect that OH-PCBs, like PCBs, are both non-Aroclors and Aroclor contaminants. They will determine the potential contribution of paint and pigment manufacturing to Chicago PCB 11 concentrations using chemical transport modeling and land use regression. Researchers will examine the sources of OH-PCBs in the environment and collaborate with toxicologists to understand their importance to human health.
For Aim 3, researchers will continue to examine the effect of dredging the Indiana Harbor and Ship Canal on emissions of PCBs. They expect to complete their assessment and publish the results of modeling of PCB air emissions modeling into the surrounding community. They will augment this work with measurements of sediment/water partitioning and physical chemical property determination for OH-PCBs.