The Gulf of Mexico oil spill still poses threats to human health and seafood safety, according to a study published Monday by the peer-reviewed Journal of the American Medical Association.
The report comes two days after President Obama and members of his family swam in the Gulf at Panama City Beach and ate fish caught there, and hours after this year's commercial shrimping season officially kicked off along the Louisiana coast.
Federal officials disputed the new report and said ongoing testing is aggressive and sufficient to protect public health.
In the short term, study co-author Gina Solomon voiced greatest concern for shrimp, oysters, crabs and other invertebrates she says are have difficulty clearing their systems of dangerous polycyclic aromatic hydrocarbons (PAHs) similar to those found in cigarette smoke and soot. Solomon is an MD and public health expert in the department of medicine at the University of California at San Francisco.
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In the longer term, she expressed worries about big fin fish such as tuna, swordfish and mackerel, saying levels of mercury from the oil might slowly increase over time by being consumed by fish lower in the food chain and becoming concentrating in the larger fish.
As time goes on, she said, doctors may be warning pregnant women and children to strictly limit the amount of such fish they eat. Some of the fish had relatively high levels of mercury even before the oil spill, she said.
"It's like iron filings to a magnet," she said. "Several years from now the concentration will go up in fish at the top of the food chain -- tuna, mackerel, swordfish."
Solomon said she based her new report on studies from past oil spills including the Exxon Valdez event off Alaska in 1989, plus her own monitoring of current Gulf data from the National Oceanographic and Atmospheric Administration, the Environmental Protection Agency and the Food and Drug Administration. She also is a member of the Natural Resources Defense Council (NRDC), which calls itself "the nation's most effective environmental action group." Solomon's co-author is Sarah Janssen, MD, a staff scientist with the NRDC.
FDA officials disagreed with Solomon's fears about PAHs.
"We don't agree that's currently a problem,'' said Vicki Seyfert-Margolis, from the office of the chief scientist of the FDA. She said federal officials have a "mussel watch'' program to test for such contamination in all shellfish, and so far it has not found any problems.
As each Gulf area is reopened for fin fish harvest, she said, officials are testing shellfish separately, approving various species only as studies are completed, she said.
For example, shrimp harvesting was reopened off Pensacola on Monday, she said.
Crabs and oysters take longer to test and clear because people eat the entire animal including the liver, where toxins can accumulate, while almost no one eats the liver of a fish, she said.
Seyfert-Margolis agreed that testing must continue for fin fish to make sure toxins don't build up in the future. Such testing will begin if similar early problems come up in the mussel-watch program, she said.
"We have the ability to test it in fin fish. We can study it as long as necessary,'' she said.
Concerning the human effects of the oil spill, Solomon says: "The good news is that the levels of benzene, the most dangerous chemical from oil, have been quite low. It's not likely there's a long-term risk from inhaled vapors for coastal residents.''
She went on: "For oil workers it might be a different story. The people out there deploying boom and burning the oil have been exposed to higher levels of vapor.''
She decried the lack of studies of long-term health effects of past spills such as the Exxon Valdez accident. But she said that on Tuesday the National Institutes of Health will announce a long-term health study of 20,000 Gulf workers and residents.
She pointed to a study of 858 cleanup workers in the 2002 oil spill by the tanker Prestige off the coast of Spain that found DNA damage, although Spanish health officials have said it was not permanent.
On Aug. 10, another 5,144 square miles of Gulf waters were reopened to commerecial and recreational finfish fishing by NOAA, the EPA and the FDA. It reduced the part of the Gulf still closed to 22 percent, from a peak of 37 percent.
NOAA said chemical analysis of 153 fin fish including grouper, snapper, tuna and mahi mahi found contaminants ``well below the levels of concern.'' Also, fish and shellfish harvested from areas unaffected by the closures are considered safe to eat, the FDA said.
"We are confident that Gulf fish from this area is safe to eat,'' said NOAA administrator Jane Lubchenco at the time.
Over the weekend, FDA tests also cleared shrimp from Louisiana's Barataria Bay, making possible the opening of shrimping season there, the Associated Press said. Crabs and oysters, the slowest to metabolize toxins, have not yet been cleared. NOAA will continue sampling, including at dockside.
"We're not going anywhere,'' said Lubchenco.
"I'm not disputing the reopenings,'' Solomon said. ``Many areas of the Gulf are quite likely safe for fishing. But what's true now might change in the future.''
Ronald Kendall, chairman of Texas Tech University's Department of Environmental Toxicology, agreed that PAHs can be a problem.
"They can accumulate in shellfish, and some can be carcinogenic. On the other hand, they are testing a lot for them.''
Kendall tested a small sample of shellfish from the Louisiana coast with gas chromatography on Monday for the ABC News program Good Morning America and said he found all to be clean.
But he added that, while oysters are stationary, shrimp can move about. And so can oil.
"So we must continue to monitor this very closely. Shellfish may be clear now, but in two months maybe not, depending on how the oil moves. You can't just test once and stop. There's a lot of oil in the Gulf, and we don't know where it all is.''
Kendall also agreed that toxins could build up in large fin fish.
"That's another reason we need to keep testing.'' Asked about the Obamas swimming and eating fish in Panama City, Solomon said: ``There are areas along the Gulf Coast that are safe for swimming and fishing. They were in one area that's considered safe. But people all across the Gulf Coast shouldn't assume that if it's safe where the president swam, it's safe where they live.''
People should avoid waters with any trace of oil, she said.
"Use your own eyes. If you see tar balls, oily sheen, don't go in the water. If you're eating fish, make sure they come from an area that's open for fishing and you get it from a reputable fish market or restaurant. If there's any oily smell, don't eat it.''
In her report, Solomon cites a 2002 study in the peer-reviewed journal Marine Environmental Research of the effects of the Exxon Valdez oil spill that concluded: "Our data show that 10 years after the spill, nearshore fishes within the original spill zone were still exposed to residual hydrocarbons. All biomarkers [for contaminants] were elevated in fish collected from sites originally oiled, in comparison to fish from unoiled sites.''
Lead author of the Exxon Valdez study was Stephen Jewett of the School of Fisheries & Ocean Sciences at University of Alaska.