Finding the Next DDT or PCB

 Clarkson Prof. Tom Holsen and his team are working to identify contaminants of emerging concern in the Great Lakes ecosystem before their use becomes widespread.



Dr. Tom Holsen, the Jean S. Newell Distinguished Professor in Engineering, is leading the interdisciplinary team of researchers from three universities.


Chemicals that historically have not been found in the environment are now being detected in the world’s largest freshwater system — some at levels far higher than expected. For nearly a decade, the EPA’s Great Lakes Fish Monitoring and Surveillance Program has included an in-depth search for contaminants in these waters. As part of this program, Clarkson’s Thomas Holsen leads an interdisciplinary team of researchers from three universities.

The Jean S. Newell Distinguished Professor in Engineering says, “Most of these chemicals would not persist in the environment if released, but some have properties that suggest they may accumulate in fresh water, potentially making it toxic.”


Water and sediment samples are taken for study in the research vessel’s on-site lab and back on shore.

These chemicals are considered contaminants of emerging concern (CEC) and the risks they pose to human health and the environment are generally not known. These pollutants can come from municipalities, manufacturing and agriculture. They can be found in pharmaceuticals, personal care products, and perfluorinated compounds or PFCs, which have been produced for decades.

PFCs are a current focus of the project in the Great Lakes, targeted to identify potentially problematic chemicals prior to their extensive use and release. Voluntary or regulatory action can be taken to eliminate use of these substances if they are found to be accumulating in the ecosystem and, ideally, before they become a significant environmental problem.

“We want to identify the next PCB or DDT before their use becomes widespread,” says Holsen, “but there is at least one significant difficulty: We don’t know exactly what we are looking for. This poses a dilemma because most analytical techniques are developed and evaluated using the compound of interest. Not knowing what to look for makes this work both challenging and exciting.”

The unique chemical resistance offered by the carbon-fluorine backbone has found many commercial applications, including the production of Teflon, firefighting foams, textiles and commercial goods. PFCs were a key ingredient of the original formulation of Scotchgard (3M), a durable repellent applied to fabric, furniture and carpets to protect them from stains. Since PFCs are so widely distributed they pose a significant analytical challenge. Most laboratory instruments and supplies contain Teflon, contaminating sample preparation or analysis unless extraordinary measures are taken.

The work at Clarkson to determine spatial and temporal trends (2004 -2012) found that PFCs were present in lake trout and walleye. As expected, Lake Superior, the most remote lake —farthest from human activities — had the lowest levels of PFC. Fish in Lakes Erie and Huron had the highest concentrations.

Temporally, PFC concentrations in lake trout significantly decreased in most lakes suggesting the voluntary phase-out of PFCs is working in lowering environmental concentrations.


Comprising Lakes Superior, Michigan, Huron,, Erie, and Ontario, the Great Lakes contain 21% of the world’s fresh water.

Approximately 30,000 other chemical substances in wide commercial use could also be CECs, but most are not being monitored for in the environment.

Looking for these contaminants requires several new approaches. Advanced analytical instrumentation allows the use of novel techniques to measure pollutant concentrations at levels that previously were not possible. These instruments provide additional information about the structure of the pollutant that makes identification possible.

Through these studies, the teams are improving the understanding of contaminant movement and fate in the Great Lakes. This research may provide policy makers with the information on environmental contaminants they need to limit the release of potentially harmful chemicals into the environment and help safeguard ecosystem and human health.

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