Dioxins are primarily byproducts resulting from paper mills, industrial waste incineration and water purification processes, but they also result from natural sources like forest fires in much smaller quantities. Rifai said her team believes the majority of dioxins found locally today are from historical sources.
Meanwhile, PCBs, whose manufacture was banned in 1979, long were used as coolants and lubricants in electrical transformers and capacitors. Why they persist today in local waterways and seafood remains something of a mystery, Rifai said.
"Now, what we find with the PCBs, and what's got people worried, is, if indeed it's historical from before the ban, you would see it in the sediment," she explained. "But, we're actually seeing the patterns have shifted, as if there are some new sources of PCBs. Since the 1990s, we've had so much growth and industrial activity kicking back up that there might be some new material coming in."
What those new sources are remains unclear, Rifai said, and materials that were manufactured with PCBs before the ban may still be in use.
"Historically with PCBs, if you've made a million transformers, you didn't have to destroy them. You use them up till they die," she said, adding that many outdated transformers were ruined by Hurricane Ike.
In July 2008, the Texas Department of State Health Services issued an advisory for Galveston Bay, Chocolate Bay, East Bay, West Bay, Trinity Bay and contiguous waters, saying consumers should limit intake of spotted seatrout, also known as speckled trout, and gafttop catfish to no more than one 8-ounce meal a month. Furthermore, children, women who are nursing, pregnant or who
|Contact: Angela Hopp|
University of Houston