by Lee Bergquist, Journal Sentinel
Levels of a now-banned toxic pollutant continue to decline in the tissue of coho and chinook salmon in Lake Michigan waters.
A study by researchers from the state Department of Natural Resources shows that concentrations of polychlorinated biphenyls have been falling since the industrial chemicals were prohibited in the 1970s.
The findings are good news for Lake Michigan, which has the highest concentrations of PCBs in all of the Great Lakes. It's also good for those eating the prized sport fish, although the DNR continues to recommend limiting how much salmon people regularly eat.
The
state's fish consumption advisory for coho and chinook recommends eating one meal per month.
Writing in the
Journal of Great Lakes Research, the researchers found that PCB levels dropped 23.9% in coho salmon from 1975 to 1986 and fell 16.7% for chinook over the same period.
The decline has moderated significantly since then, however. The scientists found that PCB levels declined 4% in chinook and 2.6% in coho between 1986 and 2010.
The study reflects the findings of other research where falling PCB concentrations were found in water, gull eggs and lake trout.
A federal
Environmental Protection Agency study from the mid-1990s showed that levels were dropping because more PCBs leave the lake, primarily by escaping into the air, than enter the lake.
In 2011, the DNR also reported that walleye in Little Lake Buttes des Morts in northeastern Wisconsin had
sharply lower PCB levels in 2010 after contaminated sediments had been removed.
http://www.jsonline.com/news/wisconsin/pcb-levels-in-lake-michigan-salmon-continue-to-decline-b99298521z1-264569061.html
