Gulf of Mexico Seafood Safety Testing After Deepwater Horizon

The safety of seafood from the Gulf of Mexico became a central concern following the Deepwater Horizon blowout a year ago. Even after previously closed Gulf waters began reopening in summer 2010, consumer confidence in the safety of Gulf seafood remained shaky. A new review published in the peer-reviewed journal Environmental Health Perspectives (EHP) affirms that levels of polycyclic aromatic hydrocarbons (PAHs) found thus far in Gulf seafood samples in fact have been well below levels that would be of concern for human health.

Nevertheless, the review authors write, federal protocols to reopen waters to commercial fishing after an oil spill should be standardized and strengthened to better protect sensitive populations. Moreover, they assert, timely, clear communication about the results of seafood testing will go far in promoting consumer confidence.

The Deepwater Horizon blowout occurred April 20, 2010, and the U.S. National Oceanic and Atmospheric Administration (NOAA) began closing commercial fisheries May 2. By June 21, 37 percent (225,290 square kilometers) of the Gulf of Mexico Exclusive Economic Zone was closed to commercial fishing.

NOAA began reopening federal waters to fishing June 23 after sensory and chemical testing of Gulf seafood by the U.S. Food and Drug Administration (FDA), NOAA, and state agencies indicated it was safe to eat. Protocols relied heavily on sensory testing (i.e., expert evaluation based on the smell of raw and cooked seafood), in addition to more sensitive but less frequent chemical testing for PAHs, a group of compounds with a wide range of toxicities. Seafood was considered safe if chemical tests indicated PAH levels below levels of concern (LOCs) for human health set by the FDA and NOAA in collaboration with Gulf states.

NOAA also developed and implemented a new test to detect dioctyl sodium sulfosuccinate (DOSS), a primary component of the two chemical dispersants used in the Deepwater Horizon disaster (Corexit 9500 and 9527A). DOSS has been detected in only a small minority of samples from the Gulf of Mexico and at levels far below the LOC.

The well was capped on July 15, and as of April 19, 2011, all federal waters had been reopened to fishing.

The authors of the EHP review developed several recommendations after reviewing toxicology reports from oil spills worldwide and examining protocols for reopening fisheries after the Deepwater Horizon blowout and previous spills. They recommend that Gulf seafood continue to be tested for PAHs in light of potential recontamination from disturbance and redistribution of uncaptured oil. After previous spills, PAH levels have been elevated in fish and shellfish for periods ranging from several weeks to several years. Little is known about the toxicity of dispersants applied deep under water, as during the Deepwater Horizon disaster, but given the lack of information on environmental persistence of DOSS, they also recommend continued testing for this compound.

Additional testing is recommended for metals such as mercury, cadmium, and lead, which are found in crude oil and in drilling fluids. “Based on evidence from previous oil spills, it is in the interest of public health to monitor levels of metals in seafood,” said lead author Julia M. Gohlke of the University of Alabama at Birmingham. Some metals are known to bioaccumulate in seafood and can damage the developing nervous systems of infants and young children.

According to the authors, expanded monitoring for PAHs and DOSS in the Gulf of Mexico and additional testing for metals will not only protect consumers now but also provide valuable information for preparedness in response to future spills.

The LOCs used in Gulf seafood testing represented the amount of PAH that would be considered safe for an 80-kilogram (176-pound) adult whose seafood consumption is in the top 10% for U.S. adults. However, “the risk assessment parameters used to develop the LOCs may not be conservative enough to cover the most sensitive populations,” Gohlke said. The authors recommend that lower LOCs be set for children, who have higher ratios of consumption to body weight, and that seafood consumption rates used in the FDA formulas be tailored to affected populations. For example, recent surveys indicate Gulf residents may eat up to 12 times more shrimp than the generic “high end” consumption rate of 13 grams per day used to calculate LOCs for the Deepwater Horizon disaster.

The authors also recommend that agencies provide timely and effective communication of testing results to help consumers understand “levels of risk in the context of previous disasters as well as . . . everyday decisions people make at the grocery store.” They also encourage agencies to involve communities in seafood monitoring. “Increased stakeholder involvement in the monitoring scheme may help to heighten consumer confidence by increasing understanding of the risk assessment and testing process,” Gohlke said.

The article, “A Review of Seafood Safety after the Deepwater Horizon Blowout,” will be available May 12 free of charge at Other study coauthors are Dzigbodi Doke, Meghan Tipre, Mark Leader, and Timothy Fitzgerald. The work was supported in part by the Walton Family Foundation.

EHP is published by the National Institute of Environmental Health Sciences, National Institutes of Health, Public Health Service, U.S. Department of Health and Human Services. EHP is an open-access journal, and all content is available free online at Brogan & Partners Convergence Marketing handles marketing and public relations for the publication and is responsible for creation and distribution of this press release.