Researchers from the University of Iowa have uncovered high levels of toxic polychlorinated biphenyls (PCBs) in the deep sediments lining the Indiana Harbor and Ship Canal (IHSC) in East Chicago, Indiana.

Scientists say the discovery is cause for concern because the IHSC is scheduled to be dredged in 2012 to maintain proper depth for ship traffic in this heavily industrialized area of southern Lake Michigan.

The study, published online in the journal Chemosphere builds upon a previous study that found the release of PCBs from the sediment floor to the water above, and the air.

This time, scientists drilled down into the floor of the canal and discovered that the concentration of said substances buried within the sediment is even higher.

“We found that the deeper you go, the more toxic it is.” – Andres Martinez University of Iowa postdoctoral scholar

PCBs can enter the human body by the ingestion of contaminated food.

The Environmental Protection Agency (EPA) said these compounds have been shown to cause cancer, along with a variety of other adverse health effects on the body’s immune, reproductive, nervous and endocrine systems.

“This finding is significant because it demonstrates that the concentration of toxic chemicals below the surface of the canal floor is quite high.”- Keri Hornbuckle University of Iowa professor

To calculate accurate estimates of the amount and relative distribution of these toxic elements in the deep sediment of the IHSC, researchers employed a submersible vibro-core system and collected two core samples.

In a statistical analysis, Martinez determined that sediments in Core 1 – collected far from Lake Michigan and the main canal, where there is less vessel traffic – had PCB concentrations higher than 50 parts per million.

This qualifies as hazardous waste according to EPA standards. At those levels, the IHSC could be designated a Superfund Site. Superfund is a federal effort to clean up abandoned hazardous waste sites.

Both Hornbuckle and Martinez recommend that the PCB concentrations in the sediment be considered in the dredging strategy to reduce the potential release of toxic waste into the environment.

Researchers acknowledge that the Army Corps of Engineers may not dredge deep enough to expose the highly toxic elements.

The Iowa Superfund Basic Research Program and the National Institute of Environmental Health Sciences provided funding for the study.