Environmental Factor, October 2011, National Institute of Environmental Health Sciences
SRP researchers quantify PCB pollution in East Chicago harbor
By Rebecca Wilson
EPA employees assisted Hornbuckle and Martinez with sample collection. Here, they separate a sediment core into pieces. (Photo courtesy of Andres Martinez)
NIEHS-funded University of Iowa Superfund Research Program (SRP)(http://iowasuperfund.uiowa.edu/) researchers Keri Hornbuckle, Ph.D.(http://www.engineering.uiowa.edu/faculty-staff/profile-directory/cee/hornbuckle_k.php) , and Andres Martinez, Ph.D., have found high levels of polychlorinated biphenyls (PCBs) in the deep sediment of the Indiana Harbor and Ship Canal (IHSC) in East Chicago, Ind. The findings are cause for concern because the U.S. Army Corps of Engineers has plans to begin dredging the canal in spring 2012 to maintain the shipping lanes in this active harbor.
The study's results(http://www.ncbi.nlm.nih.gov/pubmed/21899876) were published in the Sept. 6 online edition of Chemosphere, building upon a previous study showing that airborne PCBs in the area originated in the water and sediments below (see story(http://www.niehs.nih.gov/news/newsletter/2008/november/superfund-study.cfm)). In the new study, the researchers drilled into the canal floor and analyzed core sediment samples. One of the samples yielded a PCB concentration exceeding 50 parts per million, the U.S. Environmental Protection Agency (EPA) threshold for hazardous waste. That means that the IHSC is eligible to be listed on the National Priorities List (NPL) and become a Superfund site.
Could dredging uncover PCBs deposited more than 30 years ago?
PCBs are a class of organic compounds, roughly half of whose 209 congeners, or forms of PCB, were widely used in industrial applications and products such as coolants, solvents, and paint. Due to their toxicity and persistence, the manufacture of PCBs was banned in the U.S. in 1979. They can enter the human body from eating or drinking contaminated food, inhalation, or dermal contact. The EPA has indicated that the chemicals can have several different health endpoints, including cancer, depending on the particular congener.
The study found that deeper canal sediments in their samples yielded a higher concentration of PCBs than sediments nearest the surface. This result was not a surprise to the researchers because, according to Martinez, the canal was last dredged in 1972, prior to the ban of PCBs. Any new sediment being deposited in the canal at that time could have been contaminated by chemicals present there.
Interestingly, the deepest sediments, while more contaminated than sediments near the surface, were less contaminated than the sediments a meter below the surface, which has important implications for the planned dredging. If the sediment there is exposed, then the long-term release of PCBs from the surface sediments to the water will increase. “It will be really bad if they [the dredgers] leave a high PCB concentration in the surface sediment,” Hornbuckle said.
The researchers are careful to point out that these findings reflect results from only two core samples. “We cannot tell what the trends could be with depth for the regions of the canal and harbor that will be dredged,” noted Hornbuckle, referring to the unsampled regions of the harbor.
Citation: Martinez A, Hornbuckle KC(http://www.ncbi.nlm.nih.gov/pubmed/21899876) . 2011. Record of PCB congeners, sorbents and potential toxicity in core samples in Indiana Harbor and Ship Canal. Chemosphere; doi: 10.1016/j.chemosphere.2011.08.018 [Online 6 September 2011].
(Rebecca Wilson is an environmental health information specialist with MDB, Inc., a contractor for the NIEHS Superfund Research Program and Worker Education and Training Program.)