Fishing and swimming in the Gulf of Mexico still pose a danger to human health and food safety, says a study in the Journal of the American Medical Association, just two days after President Obama and his family took a dip in the waters and ate the fish.

But federal officials said the tests they conduct are enough to protect human health, as the shrimping season kicked off in Louisiana (see related story).

The study found that shrimp, oysters, crabs and other invertebrates are likely to contain polycyclic aromatic hydrocarbons in their systems. PAHs are also found in cigarette smoke and soot, according to Gina Solomon, co-author of the study and public health expert in the department of medicine at the University of California, San Francisco.

She also said that over time, mercury from oil could accumulate in long-living, big-fin fish such as tuna, swordfish and mackerel and become part of the food chain.

"It's like iron filings to a magnet," Solomon said. "Several years from now the concentration will go up in fish at the top of the food chain -- tuna, mackerel, swordfish."

Her study uses data from past oil spills such as the Exxon Valdez, together with data from the current spill collected from the National Oceanographic and Atmospheric Administration, U.S. EPA and the U.S. Food and Drug Administration.

FDA said there is no problem with PAHs contaminating seafood, and it has rigorous tests to watch for contamination in all shellfish.

So far it has not found any problems, said Vicki Seyfert-Margolis, from the office of the chief scientist at FDA. The agency will continue monitoring shellfish according to species, she said. It will also monitor large-fin fish in the future to ensure that toxins do not build up over time, she said.

"We have the ability to test it in fin fish. We can study it as long as necessary," Seyfert-Margolis said (Fred Tasker, Miami Herald, Aug. 17). -- GV