Oysters collected from the waters of the Gulf of Mexico in Louisiana are turning up with extremely high levels of cadmium, a toxic heavy metal. The amounts–at 150 to 200 times greater than levels considered safe for human consumption of oysters– are troubling.
Louisiana took the brunt of the 4.9 million barrel BP oil spill that flowed for three months last year. Did the oil spill cause the high levels of cadmium now being found in Louisiana Gulf oysters?
Maybe, says Ed Cake, a marine biologist who works for the oyster industry from nearby Mississippi, where his auto license is “Oyster 1.”
Cake sees two potential sources of cadmium. He says there is “anecdotal evidence” that cadmium may be in the Louisiana Light Sweet Crude Oil that washed ashore from BP’s free-flowing Macondo Well.
“Therefore, oysters from areas that suffered direct oiling from the BP’s spill may contain more cadmium than oysters from areas not receiving BP’s oil,” according to Cake.
Cake says the other potential source of the heavy metal would be the oysters themselves. He said oysters seem to be natural bioaccumulators of cadmium from seawater; there have been reports of concentrated cadmium in their shells at one thousand times the background level.
Cadmium in its ionic form (which is bioavailable to oysters) is complexed by chloride ions and rendered unavailable for uptake. Cadmium bioaccumulation decreases as water salinity increases.
“Oysters from areas that experience freshwater flooding from the Mississippi River, for example, would have higher levels of cadmium than oysters from non-flooded areas closer to the Gulf, ” Cake adds. “Perhaps we can blame some of the observed cadmium levels on Governor Bobby Jindal for flushing the coastal zone with polluted river water!”
The latest oyster findings continue a trend in which local nonprofits and university researchers have come up with more unsettling findings than federal agencies, which have cleared Gulf seafood for human consumption almost from the day the oil stopped flowing.
In the past, high levels of cadmium in British Columbia oysters prompted Canadian health authorities to warn against eating certain amounts over a month’s time. Cadmium, chemically similar to mercury, last year was responsible for recalls of children’s jewelry by Walmart, and Shrek glasses by McDonald’s.