Bullhead catfish in a Pennsylvania bay are showing fewer signs of cancer after a decade of abnormally high cancer rates, the Associated Press said.
Now scientists at Penn State are trying to discover what environmental changes have caused the improved health of the Presque Isle Bay fish.
The bay is actually within Lake Erie. The report cites a number of environmental circumstances that have improved over the years, including diminished sewer overflows and closed industrial sites.
Fifty-seven percent of the brown bullheads collected in the bay in 1999 showed no sign of skin tumors. The remaining 43 percent had either skin tumors (20 percent) and/or black pigmentation, a precursor to skin tumors.
In 1990, a sampling of 50 fish showed 80 percent had skin tumors. A 1992 study of 110 bullheads found that 61 percent had skin cancer and 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.
The State College, Pa., 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.
Researchers say that the bottom-feeding catfish are a good pollution indicator.
Jack Vanden Heuvel, a Penn State molecular toxicologist found "dioxin-like activity" in 40 sediment samples collected in 1999. Tests on the sediment samples from the early 1990s may yield more information when they are completed.
Scientists are investigating whether the fish have simply evolved to be more pollution-tolerant.
For more information, read about Pennsylvania's Sea Grant program: http://www.pserie.psu.edu/seagrant/seagindex.htm
Information on the city of Erie: http://www.erie.net/~chamber/general.html
