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Cancerous Lesions Confirmed in South River Fish in Maryland

Date Posted: January 24, 2006

Laboratory studies confirm suspicions that lip growths on catfish from a Maryland river are a form of skin cancer, according to Fred Pinkney, environmental contaminants biologist with the U.S. Fish and Wildlife Service's Chesapeake Bay Field Office in Annapolis. (See photo Scientists have linked this type of tumor in brown bullheads, a species of catfish, with exposure to cancer-causing chemicals.

"Since 1992, we have surveyed 10 other locations in the Chesapeake watershed. These catfish from the South River have the highest skin tumor rate and second highest liver tumor rate," Pinkney said. Fish from the Anacostia River have a higher incidence of liver tumors.

"I am very concerned we are seeing unusually high cancer rates among these fish. We are determined to continue investigating this issue until we establish what is giving these fish cancer," said Drew Koslow, riverkeeper for the South River Federation.

"We collected 30 fish from the South River near Annapolis last year," Pinkney said. "Sixteen fish had raised, pinkish red lesions around the mouth."

Dr. John Harshbarger, a tumor pathologist with George Washington University Medical Center, identified the lesions as tumors. He diagnosed 13 of the 16 fish with invasive carcinomas; the remaining three fish had non-invasive skin tumors. In addition to the skin tumors, six of the 30 fish had liver tumors.

In studies conducted over the past 10 years, the Service linked the types of tumors found in bullheads with a class of chemicals known as polynuclear aromatic hydrocarbons. Petroleum, coal and other fossil fuels contain PAHs. They enter rivers through water runoff and build up in sediments where bullheads live. Service biologists found high concentrations of these compounds in areas of the Chesapeake watershed that also had a high incidence of tumors in bullheads.

"In the South River, however, we have not established a link between the tumors and PAH exposure," Pinkney said.

This study was a partnership between the Service and the South River Federation, a local watershed group. Together, they are pursuing follow-up studies to identify classes of chemicals that may be responsible for the high tumor incidence.

Fred Pinkney 410/573-4519 (FWS)

Drew Koslow 443/482-2154 (SRF)

Diana Weaver 413/253-8329 (FWS)

A fact sheet is at

A full report on the study is available from the Service's Chesapeake Bay Field Office or from

Last updated: June 12, 2015