High rate of tumors found in fish

Scientists led by researchers with the U.S. Geological Survey have found an elevated number of cases of skin and liver tumors in white suckers in the Milwaukee, Menomonee and Kinnickinnic rivers — a discovery that suggests more work will be needed to remove contaminants from the waterways.

In a new study, the scientists said they found evidence that some male white suckers sampled in the rivers also had testicular tumors. That was a surprise discovery, and had not often been found in other research projects involving contaminated rivers slated for environmental cleanups, a researcher in the study said. 

The exact cause of the tumors is not known, but previous research has suggested that exposure to certain chemicals can cause liver tumors in fish, according to research published this week in the Journal of Fish Diseases. 

The three rivers make up one of 43 so-called “areas of concern” in the Great Lakes region, where high levels of pollution qualify them for federal cleanup funding to remove industrial contaminants and other pollutants.

Tens of millions of dollars have been spent on cleanup projects in the Milwaukee River estuary, including more than $20 million each in recent years on the Milwaukee River in Lincoln Park and Kinnickinnic River. 

Cleanup work has included the removal of chemicals such as polychlorinated biphenyls, or PCBs, and polycyclic aromatic hydrocarbons, or PAHs. PCBs are industrial chemicals once used by local manufacturers but are now banned. PHAs come from diesel, coal, gasoline and types of oil.

According to the study, liver tumors have been associated with PAHs. 

In 2014, the Milwaukee Journal Sentinel used publicly available data dating back to the early 1980s to show a mixed bag of results in water quality measures for run-off pollutants. Bacteria levels have been falling. But a pollution measure strongly influenced by the application of road salt has grown worse.

In the latest study, Victor Pappas of the state Department of Natural Resources says the measure of skin and liver tumors is one method the DNR and the U.S. Environmental Protection Agency use to show whether additional remediation of contaminated sediments is needed. The DNR said the results indicate more cleanup in new areas of the rivers is needed.

White suckers are widely used in environmental health monitoring and are considered an indicator species. And because they forage in sediments, they can help scientists understand the types and extent of pollution in waterways. 

Vicki Blazer is a research fish biologist with the U.S. Geological Survey and the lead scientist in the study. She said pollutants that appear to be the source of tumors in white suckers could be creating tumors in other fish species, too. "Or they could have other effects, such as in reproduction, or they might simply die,” Blazer said.

The researchers sampled the three Milwaukee rivers, the Sheboygan River, the Root River in Racine and the Kewaunee River in northeastern Wisconsin between 2012 and 2014 and took 200 samples of adult fish during spawning season in each of the four river systems. 

Many of the fish with the tumors were relatively old, but Blazer said younger fish could also be affected in ways not yet known. Only adult fish were sampled.

In the three Milwaukee rivers, 48% had skin tumors and 15% has liver tumors. The Sheboygan River had a lower percentage, and Root and Kewaunee river had even less.

Pappas said that he expected the researchers to return to the rivers at some point to see whether removing contaminants corresponded with fewer tumors in the white suckers.