Mercury contamination at some oil and gas rigs in the Gulf of Mexico appears to be so severe that the rigs could qualify for the National Priorities List, a roll call of the nation's most hazardous contaminated sites.  Placement on the National Priorities List -- which would ultimately depend on approval by federal agencies -- can eventually lead to a federal "Superfund" clean-up effort, like those at Love Canal in New York and at Cold Creek Swamp and the Olin Basin in south Alabama.

But federal officials say that the rigs are unlikely to ever make the list -- in spite of any hazards they may pose to humans -- because at least some of the contamination might have been the result of federally permitted releases of pollutants. The Mobile Register found that the rigs could warrant a place on the National Priorities List by applying formulas outlined in the U.S. Environment Protection Agency's widely available Hazard Ranking System and its supporting PreScore computer program, which the agency relies on when examining potential Superfund sites.

The Register's Hazard Ranking System calculations showed that:  The well-documented contamination in the sediments beneath some rigs reached the Hazard Ranking System's maximum value for observed releases of hazardous pollutants. Mercury concentrations in many fish and shellfish sampled around at least one of the rigs were high enough to qualify the area as a contaminated fishery. Frequent use of the rigs by commercial and recreational fishermen means that the contamination around the rigs represents "a human food chain threat."

Scientists have tested only a handful of Gulf rigs, but it's apparent that the processes that caused contamination at those rigs are standard within the industry. The oil industry dumps over a billion pounds of mercury-contaminated drilling mud wastes into the Gulf each year. Drilling muds are used to cool and lubricate drill bits as they bore into the earth while plumbing for oil and natural gas. The mercury is present in an element called barite, the main ingredient in the muds.

Read the full article and think twice about ordering that grouper sandwich.