Gulf Oil Rigs Implicated

Closer to home, an investigative report by the Mobile Register newspaper, in Alabama, turned up compelling evidence that oil drilling in the Gulf of Mexico may be linked to elevated mercury levels in fish-and worse-local fishermen. The Register sponsored testing of samples of grouper, cobia, amberjack, king mackerel and other species commonly associated with the reef-like ecosystem that's grown up around the rigs. Unsafe levels of mercury, as stipulated by the FDA, turned up in nearly all the samples, the Register reported. Subsequent testing of Gulf Coast residents who said they'd eaten fish at least once a week revealed that 51 out of 65 sampled had levels of methylmercury in their bodies above 1 part per million, the threshold established by EPA as considered safe. Some had 10 or 11 times that level.

Where was the mercury coming from?

The Register cited U.S. Minerals Management Service studies showing intense concentrations of mercury within a 650-foot-diameter circle around Gulf oil rigs. There are about 4,000 such rigs out there, but none in Florida waters. The mercury concentrations, the Minerals Management Service concluded, are the byproduct of barite, a substance the oil industry employs to lubricate the huge oil well drilling bits. Mercury is contained in barite.

Scientists interviewed by the Register indicated that the same type of mercury conversion process that occurs in the Florida Everglades and elsewhere is apparently happening in the sediments surrounding the rigs. "Islands of Contamination," was the front-page headline in the Dec. 30, 2001 edition. From the base of these islands, worms, shrimp, crabs and other critters start the methylmercury on its way up the food chain.

Oil industry reps and an EPA spokesman interviewed by the Register insisted that federal regulations on barite usage had addressed the mercury problem. But could a time lag be at work here, wherein mercury levels remain elevated even after the source has been addressed? Interestingly, Minerals Management Service found dangerous levels of mercury around rigs 12 years after drilling was ceased. That's the same time frame Atkeson cited for a corresponding decline in mercury concentrations in northern Everglades largemouth bass following emissions controls.

How Much Is Too Much?

As researchers struggle to pin down the mercury problem, Florida seafood fans find themselves wading through consumption guidelines set by three agencies. The federal Food and Drug Administration (FDA) is responsible for market and restaurant fish; the Environmental Protection Agency (EPA) gives advice for recreational fishermen; and the state Department of Health rules on fish or water bodies not covered by the others.

The guidelines are easy to read, if sometimes hard to find (you'd think a state fishing magazine would be the first to receive bulletins from the Department of Health, but not so).

According to Dr. David Johnson, bureau chief of environmental epidemiology for the Florida Dept. of Health, fillets of fish are tested for methylmercury concentrations, and consumption guidelines set at levels he described as "somewhat conservative; levels at which there would be no risk to sensitive populations like women and fetuses."

Over time, Johnson said, the body can rid itself of methylmercury. The stuff has a half-life of about 44 days. Eating two tainted fish today, for example, would result in a higher net accumulation of mercury in your system than, say, eating one today, one next week. Still, consuming too much too quickly could overrun the body's defensive mechanisms. Johnson would not say for certain that immediate sickness would result from flouting state consumption advisories, but he urged anglers to abide by the guidelines.

"We want people to use these," he said, "but we get the feeling many aren't."

To be sure, there have been cases in which symptoms have arisen from relatively low levels of methylmercury exposure-though none to date that stand out in Florida. In the Amazon River basin, where methylmercury levels are thought to be rising because of soil erosion, Canadian researchers discovered impaired motor skill and perception skills among people who tested below 50 parts per million. That figure is a World Health Organization threshold that supposedly represents "no significant health risk" to adults. Children and the unborn apparently are affected by even lower concentrations. Levels of 11 ppm resulted in developmental problems among some Iraqi children born to women who'd eaten mercury-tainted grain.

Our advice, until we hear otherwise, is to follow the published consumption advisories.

--Jeff Weakley