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Postdoc Tracks Down PCBs

Posted on February 27th, 2014
Rachel Marek at work in the lab.

Rachel Marek at work in the lab.

by Matthew Wolf

Polychlorinated biphenyls, commonly known as PCBs, are everywhere in our environment. They are present in the air we breathe, the food we eat, and can even be passed from mother to child. Recent PhD graduate Rachel Marek is working to better understand where these toxins are coming from, how humans come into contact with them, and their ultimate fate.

PCBs were commonly used as coolants and electrical insulators until the 1970s, when they were banned by the Toxic Substance Control Act. PCBs have also been used in many household items, including paint, adhesives, and sealants. PCBs are known toxins to humans, and although the human body metabolizes and excretes PCBs, some can accumulate faster than the body can process them and are stored in tissue. PCBs interfere with hormone production and cause developmental problems in children. Individuals can be exposed to PCBs through air exposure, food, or direct skin contact. Recent research also shows that PCBs and their metabolites can be transmitted from mothers to children through breast-feeding.

Marek has been working with IIHR Research Engineer Keri Hornbuckle and the Iowa Superfund Research Program to determine the sources, transport, and fate of PCBs, with a special focus on the Great Lakes region. This area is of particular interest because it was a manufacturing and transportation hub for many products containing PCBs before the ban.

In Marek’s most recent project, the group collected blood serum from mothers and children in East Chicago, Ind., and Columbus Junction, Iowa. East Chicago was selected because of its proximity to the Indiana Ship and Harbor Canal (ISHC), where PCBs in the environment have been linked to the waterway’s industrial usage; Columbus Junction was selected as a comparable community with no known industrial sources of PCBs. The project compares the levels of PCBs and their metabolites in children and mothers in the two communities, and tries to determine if these observations can be explained by diet, air exposure, and metabolism.

In addition to the blood serum samples, the group also collected sediment samples from the ISHC and has worked to identify 209 PCBs and 65 metabolites through a unique process using gas chromatography instruments and mass spectrometry detectors.

“As expected, mothers have higher levels of PCBs in their blood than children,” Marek says. Children in the study were found to have lower-weight, more volatile PCBs present, which suggests that airborne exposure may be an important source of the toxins for children. Furthermore, Marek says that the researchers have identified similar PCBs and metabolites in both the rural (Columbus Junction) and urban (East Chicago) groups, suggesting that outdoor air exposure may not be as important as diet and indoor air exposure.

Lastly, the researchers found that metabolites (OH-PCBs) detected in the Great Lakes waterways appear to be coming from original sources of PCB contamination rather than through metabolic processes as observed in the study’s participants. “It is likely that toxic OH-PCBs are present in sediment any place that is contaminated with those original commercial PCB mixtures,” Marek explains. This is an important discovery, as governments and industry continue to identify and clean up sources of PCB pollution.

Marek plans to further observe the transport and fate of PCBs and OH-PCBs. By continuing to collect samples from the study’s participants over several years, she hopes to observe variations in levels and types of PCBs present over time. Additionally, she is working with IIHR Assistant Research Scientist Andres Martinez on the physical-chemical properties of OH-PCBs, to quantify their concentrations in sediment samples and determine the sources of these pollutants and their fate in the environment.

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