Little is known about the health effects of these long-lasting compounds on the marine food web or on those who eat lagoon seafood. But scientists point to their widespread presence as yet another example of the ominous effects long-term pollution is having on local waters.
Among the substances a new study found in samples of shark livers are byproducts of DDT and other pesticides banned decades ago.
“This is kind of the first approach of this. We don’t fully understand how these compounds have an influence or effect on these particular fish,” said Doug Adams, a co-author of the study and researcher with the Fish and Wildlife Research Institute. “There’s been hardly any research on what are the impacts, what are the effects.”
Adams collaborated with researchers from the University of Antwerp in Belgium and others from Australia and Norway.
The study, published recently in the journal Environmental Research, adds to the list of lagoon life found with similar persistent organic pollutants in their tissues. Previous studies have detected flame retardants and pesticide byproducts in dolphins, sea turtles, alligators and other wildlife in east Central Florida.
The researchers looked at 53 liver samples from juvenile bull sharks, bonnetheads, lemon sharks and Atlantic stingrays caught in the lagoon, from Cape Canaveral to Sebastian. The lemon sharks and some of the bonnetheads were caught just offshore of Cape Canaveral.
Among the persistent compounds were metabolites of DDT.
Brevard was an early testing ground for the pesticide.
Many lakes in Central Florida, including in Brevard, were drained in the 1940s to help grow food during World War II. Farmers left behind pesticides such as DDT, chlordane, dieldrin and toxaphene.
Even though the pesticides have long been banned, their effects persist. When government reflooded the farms to restore marshes, wildlife returned, but the pesticides in the soil entered the food web.
The researchers found high levels of flame retardants such as PCBs, widely used in plastics, caulking, transformers, capacitors and other electrical equipment. PCBs were banned in 1979, and EPA calls them “probable human carcinogens.”
One outlier the researchers caught — a stingray in Eau Gallie River — had extremely high levels of PCBs, likely “indicative of the known contaminated condition” of the river, the authors said.
The researchers also found PBDEs in the sharks and rays. Those flame retardants — some of which have been phased out — are in clothing, foam cushions, electronics, upholstery and building materials, among many other products.
Studies show PBDE doubling in humans and animal tissues every two to five years. Levels in human breast milk have shown dramatic increases in recent years, especially in the United States.
PBDEs are similar chemically to PCBs. They build up in higher levels as they move up the food web. So the shark’s role as top predator makes it especially vulnerable.
High levels of PBDEs and other persistent organic pollutants in humans can damage the nervous system, cause breast and other cancers and disrupt the immune and hormonal systems.
Other impacts include developmental and reproductive problems.
Researchers at FAU Harbor Branch Oceanographic Institute have found very high levels of PBDEs in lagoon dolphin tissues in recent years.
Such flame retardants and other persistent organic pollutants can mimic hormones and skew gender ratios, leading to fewer fish, birds, amphibians, reptiles, mammals and other wildlife.
Pesticides such as DDT and its derivatives can disrupt fetal development in animals and people. They mimic or block hormones and have been linked with faster onset of puberty and increased prostate and vaginal cancers.
Because of PCBs, state health guidelines limit consumption of striped mullet caught in Escambia River and Escambia Bay to one meal per week.
But no similar guideline exists for the lagoon.
Because of concerns about mercury, Florida health officials already recommend that children and women of childbearing age don’t eat sharks and limit consumption of Atlantic stingrays to once a month.
But exposure to persistent organic pollutants from lagoon fish is probably comparable to what’s in chicken, turkey and many other foods, says John Windsor, a marine sciences professor at Florida Institute of Technology. But scientific ability to detect the pollutants in trace amounts far eclipses the ability to link those levels with specific health outcomes, he said.
“If you analyzed everything that we either interact with, we eat or drink, to the level that these were analyzed, I think we would be shocked by all the components that are there that could be of concern,” Windsor said.
From: Florida Today
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