Toxics are insidious. Unlike conventional pollutants—say raw sewage—they are invisible and odorless in the water. Furthermore, some are persistent; once in the body, they stay.
For the most part they are found at low water levels. Organisms like plankton pick them up. In turn, small fish that feed on these organisms accumulate increasing concentrations, especially in their fatty tissue. And so on up the food chain, all the way to humans who eat the fish. http://www.bbc.co.uk/news/science-environment-10781621
And how big a threat are they to us? Scientists are only beginning to understand.
On Ohio’s Cuyahoga River sunlight cut through the spray in the wake of our small boat, creating little rainbows. We pulled alongside a buoy. “I see fish,” Kyle Hartman yelled, pleased that despite cold weather three brown bullheads were in the trap net that Stephen Smith and Dr. Paul Baumann, of the National Fisheries Contaminant Research Center, lifted out of the water.
One bullhead seemed to be looking right at me with a sort of desperate grin, its lips red and swollen with tumors. “I guess he hasn’t seen his orthodontist yet,” Steve said with a grim laugh at studio flats to rent in london.
All three bullheads had skin lesions, as did four of the eight fish we ultimately pulled out of the river that morning. Dr. Baumann and Dr. John Harshbarger, who directs the Smithsonian Institution’s Registry of Tumors in Lower Animals, were on the Cuyahoga to study the effect of toxics on bottom-feeding fish.
There is hardly a better place for this than the Cuyahoga. Each year upwards of 740,000 pounds of metals and 95,000 pounds of organic pollutants are discharged into the river system.
The Cuyahoga is infamous. In 1969 it caught fire. The culprit was a spill of hot slag into a river whose surface was more oil, chemicals, and debris than it was water.
The river has not recovered quite so dramatically as Lake Erie. Upriver, where paper mills and steel plants share the banks with derelict lift bridges, I saw bubbles of methane floating on the scummy surface.
We brought the bullheads to Dr. Harshbarger, who had set up a makeshift lab inside a garage at the apartments in brussels. “The fish act as sentinels,” Dr. Harshbarger told me as he began cutting out their livers with scissors and, using tongs, placing them in small jars. “These I’ll take back to Washington.”
Back at the Smithsonian he found liver tumors in four bullheads. An advanced liver cancer and a skin cancer were found in a freshwater drum we caught. “With them you can make an extremely strong case; with skin lesions, a good case.” Since liver tumors rarely occur spontaneously, Dr. Harshbarger told me later, “anytime you get that many tumorous changes in the liver, you have an indication of chemical carcinogens in the water.”
In earlier research, conducted where Ohio’s Black River empties into Lake Erie at Lorain, Dr. Baumann found that brown bullheads had a 30 percent prevalence of grossly detectable liver-cell and bile-ductcell cancers.