Recently some issues concerning a potential for mercury, and specifically methylmercury, contamination of marine life/seafood associated with offshore platforms in the Gulf of Mexico have been raised. Information from MMS’ studies was used to support the conclusion that drilling activities and platform structures were responsible for elevated levels of mercury in commercial fish. Additionally, it was stated that the issue has been “largely overlooked by regulators”. However, the MMS study referenced was misrepresented, resulting in misleading and incorrect conclusions.

Mercury is a naturally occurring element that exists in sediments, rocks, oil, and coal. Mercury also occurs naturally in very small quantities in barite, a major component of drilling fluids used by the offshore oil and gas industry. However, this mercury is locked in the barite grains and not easily transferred to the marine life, which live around the platforms. Methylmercury is primarily created from mercury by a chemical process controlled by bacteria and only occurs when the right conditions exist. There is no evidence that mercury from drilling muds changes into methylmercury. Disposal of drilling fluids only occurs during drilling operations. Oil companies cannot discharge drilling fluids without a discharge permit from EPA. In the barite used to make drilling fluids, the EPA requires that the concentration of mercury be no more than one part per million (see estimate of annual discharge). This reduces the addition of mercury to the environment to values similar to the concentration of mercury found in marine sediments throughout the Gulf of Mexico.

The MMS study, Gulf of Mexico Offshore Operations Monitoring Experiment (GOOMEX), was completed in 1995. In 1996 the results of this study were published in a peer reviewed dedicated volume of the Canadian Journal of Fisheries and Aquatic Sciences. This study examined three OCS platforms and included the analyses of over 700 sediment samples and over 800 tissue samples from shrimp, crabs, marine worms, clams, fish livers, and fish stomach contents. Results of the analyses documented that total mercury is not concentrated to any greater extent in organisms living near the platforms (less than 100 meters away) when compared to those living far away from the platforms (over 3000 meters). From these results the scientists concluded that platforms do not contribute to higher mercury levels in marine organisms.

The Minerals Management Service, MMS, recognizes that mercury (and specifically methylmercury) in the environment is a global issue and a global problem. While the issue of mercury in seafood in the Gulf of Mexico is the subject of an increasing amount of research particularly because of global and regional inputs, the results of research to date generally supports the conclusion that oil and gas platforms do not play a significant role in elevating levels of mercury in fish and other seafood.

MMS authorized in May 2002 a change in an ongoing study.  Sediment samples for total mercury and methylmercury were collected during a May cruise as part of an ongoing study, “Gulf of Mexico Comprehensive Synthetic Based Muds Monitoring Program,” which is funded jointly by MMS, DOE, and industry. A total of 196 samples were collected from six locations in the Gulf of Mexico. Surface samples were collected from near-field, mid-field, and far-field locations around three shallow-water and three deepwater platforms that were already scheduled for sampling under the existing study. As part of the original study, data sets including sediment oxygen, reduction potential, synthetic-based fluid concentration, iron, manganese aluminum, barium, total organic carbon, and grain size were also collected from the same locations.  This information will address a recently identified information gap in the knowledge about methylmercury in marine sediments, both associated with oil and gas platforms and background levels that are naturally occurring. Results from this study are now available.

Where can I get more information?

Contact Caryl Fagot at (504) 736-2590

Associated Correspondence 

Subcommittee on Mercury in the Gulf of Mexico

Methylmercury in the Gulf of Mexico: State of Knowledge and Research Needs