Opinion: Seafood needs better science

On August 19, 2010, the House Subcommittee on Energy and Commerce held a hearing on seafood safety in the Gulf of Mexico. The hearing was spurred by the opening of this year's shrimp season, amid worries that reopened areas might be tainted by the recent BP oil spill. Government officials testified that the seafood is safe, but fishermen and some scientists raised concerns. The health concerns from Gulf seafood are not immediate but they are serious, and the government safety system is not yet up to the task of assuring safety in the months and years ahead.

Image: Wikimedia commons

Seafood can be contaminated after an oil spill in three ways: crude oil can coat seafood or be incorporated into fish or shellfish, making it smell or taste oily and be unsafe to eat. As the oil breaks down in the environment, polycyclic aromatic hydrocarbons (PAHs) from the oil enter the food chain.¹ PAHs can cause DNA damage and cancer.² Invertebrates (such as oysters, shrimp, and crabs) are less efficient at excreting these chemicals, so they are most likely to be contaminated.³ Toxic metals, such as mercury, cadmium, and lead are also found in crude oil.⁴ Although only trace amounts are present in the oil itself, these metals bioaccumulate in the food chain and the peak levels of metal contamination will likely occur months or years from now in swordfish, tuna, King mackerel, and marine mammals. These metals can cause damage to the kidneys and central nervous system, particularly during pregnancy.

Assuring seafood safety over an area as large and varied as the Gulf of Mexico is a difficult task. The Food and Drug Administration (FDA) performed a risk assessment to determine what levels of PAH contamination should be allowed in Gulf seafood, and the National Oceanic and Atmospheric Administration (NOAA) is conducting monitoring in the Gulf to compare seafood against the FDA limits. States are in charge of their own waters (within 3 miles of the shore in Louisiana and Mississippi) and are making independent (and not always science-based) decisions about reopening their fisheries. A non-scientific convenience sample of a few pieces of seafood has been used by the popular press to argue that all Gulf seafood is safe. Small samples that are not representative of the range of conditions present in the reopened Gulf fisheries cannot be used as a scientific basis for demonstrating safety.

The FDA made four questionable assumptions in their risk assessment that could jeopardize vulnerable populations: First, their "average fish consumer" weighs 80 kilograms (176 pounds), which may be appropriate for a man, but wouldn't protect children and most women.⁵ Second, the FDA ignored scientific data showing that fetuses can't efficiently repair the genetic damage caused by PAHs, and that babies may also be at increased risk of neurological effects from these chemicals, failing to adjust the risk assessment to protect them.⁶ Third, they used national seafood consumption data, assuming that people eat one meal of shrimp per week and a serving size of 3 ounces (about 4 large shrimp). These numbers don't match up with the shrimp-heavy diets of Gulf residents. Finally, the FDA assumed that Gulf seafood contamination would disappear within five years, whereas previous scientific studies after oil spills have documented contamination at least 6-7 years later.⁷

Meanwhile, NOAA has been testing for PAHs in seafood but has not been testing for metals. The PAH sampling frequency cited in the NOAA protocol of "6 sub-samples per species from each sampling location" may be inadequate to assure testing of the reopened fisheries. NOAA claims to have collected thousands of samples, but have made data publicly available on less than 200; none of which have included shrimp. Data from reopened state waters have not been released at all.

These scientific concerns don't necessarily mean that Gulf seafood isn't safe, or that the areas that have been reopened to fishing should be closed; those questions are yet to be answered. Furthermore, the contaminants from the oil are not likely to affect health with short-term or moderate consumption. Yet the health concerns are real, so the government must set up a robust and scientifically valid system today in order to assure safety for years into the future.

Dr. Gina Solomon is an associate clinical professor of medicine, the director of the occupational and environmental medicine residency program at the University of California San Francisco, and a senior scientist at the Natural Resources Defense Council (NRDC). Miriam Rotkin-Ellman is a public health scientist at NRDC. Dr. Solomon and Ms. Rotkin-Ellman have been researching the human health effects of the Gulf oil spill, including analyzing data on air quality and seafood contamination.

References:

1) J. Tronczynski, et al., "Contamination of the Bay of Biscay by polycyclic aromatic hydrocarbons (PAHs) following the T/V 'Erika' oil spill," Aquat Living Resour, 17:243-59, 2004.

2) Agency for Toxic Substances and Disease Registry (ATSDR), "Toxicological Profile for total petroleum hydrocarbons (TPH)," Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, 1999.

3) RJ Law and Hellou J, "Contamination of Fish and Shellfish following Oil Spill Incidents," Environ Geosci, 6:90-8, 1999.

4) LC Osuji and Onojake, CM, "Trace heavy metals associated with crude oil: A case study of Ebocha-8 oil-spill-polluted site in Niger Delta, Nigeria," Chem Biodivers, 1:1708-15, 2004.

5) FDA, "Protocol for Interpretation and Use of Sensory Testing and Analytical Chemistry Results for Re-Opening Oil-Impacted Areas Closed to Seafood Harvesting," June 18, 2010.

6) F Perera, et al., "Biomarkers in Maternal and Newborn Blood Indicate Heightened Fetal Susceptibility to Procarcinogenic DNA Damage," Environ Health Perspect, 112:1133?36, 2004.

7) F Berthou, et al., "The Occurrence of Hydrocarbons and Histopathoiogical Abnormalities in Oysters for Seven Years Following the Wreck of the Amoco Cadiz in Brittany (France)," Marine Environmental Research, 23:103-33, 1987.

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