Monday, March 20, 2000 Cancerous catfish Erie's bullheads now healthier... but why? By DAVID KINNEY -- The Associated Press Channel Catfish STATE COLLEGE, Pa. (AP) -- It's a decadelong scientific whodunit. For years, researchers tried to figure out why so many bullhead in Presque Isle Bay had tumors. Now, they're trying to unravel a twist that is just as mysterious: Why has the cancer rate in the catfish dropped so precipitously since the late 1980s? It might be the millions of dollars [7] Erie has spent to cut sewage overflows. Or maybe it's that some of the big industrial polluters have closed. Or it could just be evolution: The catfish are adapting naturally to cope with the pollution. "I could go on and on and on about all these theories," said Penn State's Eric Obert. "It's a pretty complicated case." The bay is formed by a thin sand spit reaching into Lake Erie from the industrial city. Long polluted by direct discharge of industrial sewage and municipal sewer overflows, the bay is in the process of being cleaned up. The city has spent millions to upgrade a wastewater treatment plant and millions more to stop the overflows that sent untreated sewage into the bay during heavy rains. The city was up for a national anti-pollution award, and Erie might be able take credit for the improved health of the resident bullheads, too -- if, that is, anyone knew what caused the tumors in the first place. "We don't really have a clue why," said Obert, who runs the region's [8] Sea Grant program, an arm of the National Oceanic and Atmospheric Administration. The catfish, researchers have found, are a good tool for tracking pollution. If the water isn't safe for the bottom-feeding bullheads, it might be a warning sign for humans. "Bullheads are probably kind of a canary in a coal mine," said Jack Vanden Heuvel, a Penn State molecular toxicologist. "They're a sentinel kind of animal to tell us if there is a problem." The latest research on the cancerous catfish suggests what was assumed from the start: Polluted sediment is to blame. Vanden Heuvel examined 40 sediment samples collected last year and found "dioxin-like activity." Any number of thousands of industrial pollutants could be to blame. But if the pollution is still there, why is the tumor rate down? Vanden Heuvel doesn't know. He still needs to test the samples from the early 1990s to determine whether toxin levels have decreased. Catfish -- Image from [9] Andrew's Catfish page "We could see if the dioxin-like response is stronger in the past than it is now, which would be a sign that the area is cleaning up. "The other possibility," he added, "is that the area is not cleaning up, but the fish have evolved. It's not necessarily that the bay is getting better, but the fish are getting better at dealing with it." Like so many theories researchers have entertained, his may not stand up. It was the 1980s when anglers first started noticing the tumors. The bullhead is ugly as it is, but in cancerous fish, red bumps clung to the barbules, their lips turned puffy and red, black spots dotted their bodies. In 1990, Obert looked at 50 fish from the bay. An astounding 80 percent had skin tumors. Ten of the worst-looking fish were sent off to a lab in Maryland: Four of them had liver tumors, too. Two years later, a study of 110 bullheads found that 61 percent had skin cancer, 22 percent had liver tumors. Then, in 1995, a new study found that just 10 percent of bullheads had liver tumors. In 1997, the rate fell to the single digits, the normal range in the Great Lakes. Researchers are still grasping for an explanation to explain that decline. The first chemical to be investigated was a cancer-causing compound called nitrosamine. The bay had high levels of nitrogen after hot effluent from a power plant killed off thousands of gizzard shad. That plant has closed, but the connection to the cancer is murky. Then they looked at PAHs, or polycyclic aromatic hydrocarbons, produced by the burning of fossil fuels. But catfish with high PAH rates didn't necessarily have tumors. Next, they considered a virus. Then they looked for testing errors. No perfect answer popped up. "It could be that all of them are problems," Obert said. "That's been my frustration." Paul Baumann, an Ohio State professor, related a story about how clams off a pristine Maine coast developed tumors. Nobody knew why, until they discovered a nearby blueberry farmer who sprayed his fields with pesticides, then washed his trucks in the bay. "There is a cause," Baumann said. "They just don't know what it is."