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July 18, 2011
Volume 89, Number 29
pp. 12 - 16

Testing Gulf Seafood

After the oil spill, analytical protocols to assess contaminants in seafood found few problems, but the public and some scientists are not reassured

Ann M. Thayer

Sniff Test: Steven Wilson, chief quality officer for NOAA’s Seafood Inspection Program, demonstrates sensory analysis of a sample of shrimp. NOAA
Sniff Test Steven Wilson, chief quality officer for NOAA’s Seafood Inspection Program, demonstrates sensory analysis of a sample of shrimp.
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The explosion of BP’s Deepwater Horizon oil rig caused 4.9 million barrels of oil to be dumped into the Gulf of Mexico. Of that total, an estimated 17% was recovered and close to 8% was skimmed or burned off. More than one-third is believed to have evaporated, dissolved, or dispersed naturally, and about 16% was dispersed chemically. The fate of the remaining oil—roughly 1 million bbl—is uncertain.

Within two weeks of the April 20, 2010, disaster, the National Oceanic & Atmospheric Administration began closing federal waters to fishing. By June 2, the closures reached a peak when 88,522 sq miles, or 37% of the Gulf, were declared off-limits. After the wellhead was sealed in mid-July, NOAA began to reopen large areas. With the reopening on April 19, 2011, of the last 1,041-sq-mile sector immediately around the wellhead, the entire Gulf was open to fishing a year after the spill.

The closings had a massive impact on the Gulf Coast seafood industry. Gulf fishermen harvest some 1.3 billion lb per year of fish, crabs, oysters, and shrimp—about 20% of U.S. commercial seafood production. Oiled areas were closed to prevent contaminated seafood from reaching the market, and fishing was allowed only after all sampled seafood tested clean.

Putting a testing process in place took a concerted effort. NOAA, in cooperation with the Food & Drug Administration, the Environmental Protection Agency, and state authorities, agreed on a reopening protocol that included analytical testing for contaminants. Of greatest concern were potentially toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs) and the chemicals in the dispersants. Surveillance testing is ongoing.

“We’re very confident that the steps that we have put in place to ensure the safety of seafood have worked,” says Donald W. Kraemer, acting deputy director of FDA’s Center for Food Safety & Applied Nutrition, in a video posted on the agency’s website. “We had an extensive program of sampling at that time and since then, and the results have consistently been 100 to 1,000 times below our levels of concern.”

Balancing consumer protection with the seafood industry’s desire to get back in business required analytical methods that could provide answers quickly without compromising accuracy, reliability, or safety. Multiple FDA, NOAA, and state labs worked to refine testing procedures, create new ones, and put them into practice. Although the tests themselves are considered adequate, environmental groups and academic researchers have raised concerns about the government’s overall approach to risk assessment.

Experience from previous spills gave regulators an understanding of which PAHs to test for and how long it takes animals to clear oil from their systems, according to Kraemer. Oysters, for example, are the first to pick up contaminants, and they hold on to them the longest. Finfish, or non-shellfish, metabolize PAHs much faster and have a low potential to accumulate them in their tissue and transfer them up the food chain, according to NOAA. Shrimp and crabs fall in between.

On the basis of such knowledge, levels of concern (LOCs) for contaminants in seafood were set in the reopening protocol by using what Kraemer has called “very conservative estimates” for people’s seafood consumption and exposure duration. LOCs fell into the range of hundreds of parts per million for chemicals that FDA viewed as not potentially carcinogenic to as low as parts per billion for more harmful ones.

All seafood samples underwent initial sensory screens, or sniff-and-taste tests, which are common in food inspection. Specially trained at NOAA’s National Seafood Inspection Laboratory in Pascagoula, Miss., inspectors can detect unusual odors and flavors at down to about the 10-ppm level. If samples failed, the associated fishing areas were kept closed. Seafood samples that passed were then subject to chemical analysis.

Because of previous oil spills, chemical screening methods already existed for seafood. The accepted NOAA method for PAH detection uses gas chromatography along with mass spectrometry. However, the method requires extensive sample cleanup. To handle the large amounts of seafood that would need to be tested, FDA wanted a simpler approach with higher sample throughput.

By late July 2010, FDA scientists and collaborators had adapted known extraction and liquid chromatography-fluorescence detection (LC/FD) methods. In the adapted method, PAHs are extracted from pulverized seafood through a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample prep developed for monitoring pesticide residues in food. The extracts are filtered but don’t require further cleanup for LC/FD analysis. Testing times were reduced from about a week to two days.

The method can be used to screen for 13 target PAHs, as well as common alkylated homologs and metabolites. It was validated for fish, oysters, shrimp, and crabs. Samples found positive for a target PAH were required to undergo confirmatory testing using the GC/MS method.

Testing for trace dispersants didn’t emerge until later. According to FDA and NOAA, their own and independent studies had shown that because the dispersants are metabolized and excreted, they “do not accumulate in seafood, and therefore there is no public health concern.” EPA also reported that mixtures of dispersant and oil were no more toxic than the oil alone.

Ultimately, the extent and unique use of the dispersants—about 1.8 million gal worth, about half of which was applied deep underwater instead of only on the surface—called for greater caution. To ensure consumer confidence in the safety of Gulf seafood, FDA and NOAA added dispersant testing to the reopening protocol. But a chemical test had to be developed, and sensory assessors trained.

The agencies decided to test for dioctyl sodium sulfosuccinate (DOSS), a major dispersant component that has low volatility and the potential to persist in the environment. DOSS is used in pharmaceuticals and in food at levels of up to 10 ppm. FDA calculated LOCs at 100 ppm for finfish and 500 ppm for shrimp, oysters, and crabs.

By late October 2010, when just 4% of the Gulf was still closed, FDA’s Forensic Chemistry Center in Cincinnati and NOAA’s Northwest Fisheries Science Center in Seattle announced that they had a test method for DOSS. The procedure drew upon and complemented the PAH method, relying on QuEChERS for sample extraction, followed by LC and tandem mass spectrometry (LC/MS/MS) analysis.

With the method in place, 1,735 samples, including about half of the original number collected and new samples coming in, were analyzed for DOSS. “Pretty much as we had predicted, there almost never were any detectable findings of the dispersant in the fish flesh,” Kraemer said. FDA and NOAA reported that all samples passed sensory testing and that LC/MS/MS showed no detectable residues in 99% of samples. For the 1% that tested positive, DOSS levels were less than one-thousandth of the LOCs.

Although speed was desirable, sensitivity was key. The DOSS method can detect dispersant at a level that is one two-thousandth of the lowest LOC, according to the agencies. When it comes to PAH testing, LC/FD is cheaper and faster than GC/MS, but there are trade-offs in terms of exactly what compounds can be identified. Both methods, however, are sensitive enough to detect well below the LOCs and provide reliable estimates of PAH levels, according to scientists who developed and used the techniques.

EPA had classified seven of the target PAHs as probable human carcinogens. And FDA set the LOC for benzo[a]pyrene, one of the most widely occurring and potent of them, at 35 ppb. The LC/FD method’s detection limit is down to the single-digit-ppb range for most PAHs, according to the scientists who developed it. In contrast, the GC/MS method can be about 10 times more sensitive.

While FDA and NOAA labs across the country handled testing of seafood from federal waters, state labs followed the same protocols for their coastal waters. As a contract lab, Eurofins Central Analytical Laboratories, located in Metairie, La., conducted testing for Louisiana, according to the lab’s director, John M. Reuther.

Eurofins always used a GC/MS method, Reuther says. “The GC/MS method is simply overall more specific, more sensitive, and more selective toward running those compounds,” he says. “The LC method is good for a qualitative reporting of hydrocarbons and serves the purpose of saying there are no hydrocarbons of concern, but if we ever find anything that indicates anything close to a positive it will have to be confirmed by the GC/MS method anyway.”

Although the LC/FD method supported quickly reopening Gulf waters, testing now that the oil has dissipated addresses problems of perception about the quality of fish coming out of the Gulf, Reuther explains. “The most important thing to do is demonstrate, by the most sensitive and selective methods we can find, that the product is either good or not good,” he says. Eurofins conducts testing for PAHs, DOSS, and metals for Gulf Wild, one of many programs that have emerged in the region to rebuild consumer confidence in seafood safety.

Indeed, although all samples have come up clean, a perception problem still exists. According to an October 2010 Institute of Medicine report, many observers, including members of Congress, nongovernmental organizations, scientists, fishermen, seafood processors, and chefs, have had concerns about the adequacy of the federal testing protocol. Some mistrust the risk assessment methods used to establish safe levels for contaminants.

In May, University of Alabama, Birmingham, environmental health sciences professor Julia M. Gohlke and colleagues, along with Timothy Fitzgerald of the Environmental Defense Fund, published a review paper in Environmental Health Perspectives (DOI: 10.1289/ehp.1103507). In it they analyzed the risk assessment process and compared it with those for previous spills.

The assumptions used to set LOCs have been inconsistent across spills, Gohlke and coworkers found. In the case of shrimp and oysters, the recent Gulf LOCs are higher than those set for shellfish in previous incidents. And in comparison with the 1989 Exxon Valdez spill, FDA chose a higher body weight and cancer risk level, and shorter exposure time to calculate contaminant levels from the Gulf spill.

The LOCs set by FDA are “grossly inadequate,” says Miriam Rotkin-Ellman, a scientist with the Natural Resources Defense Council, an environmental group. “When we look at the multiple ways in which FDA underestimated risk, these LOCs are orders of magnitude too high.” Last summer, NRDC and two dozen Gulf Coast groups called on NOAA and FDA to strengthen the protocol. NRDC hasn’t yet determined whether the detected levels of contaminants would fall below the even more stringent limits it would like to see, she says.

NRDC contends that FDA greatly underestimated seafood consumption in calculating LOCs. FDA used figures from national surveys for the top 10% of consumers; an NRDC survey found consumption rates in the Gulf region to be up to 10 times higher. Yet on the basis of actual contamination levels, FDA says, people would have to eat several pounds of fish or oysters or several tens of pounds of shrimp every day for there to be any concern.

By using a heavier body weight than that used for previous spills, FDA also didn’t account for the potential impact on groups including women and children, Rotkin-Ellman explains. “If you are concerned about lower levels for vulnerable populations, it raises some valid questions about the appropriate analytical method.”

Gohlke suggests that using plausible risk parameters for different groups to create a range of LOCs, as presented in the review article, would have been a satisfactory solution. Even with the more conservative LOC estimates, the detected PAH levels would have been deemed safe, she says. In general, PAHs measured in Gulf seafood are “at or below levels reported after previous spills,” according to Gohlke and her coworkers.

Beyond the high LOCs, NRDC takes particular issue with FDA’s failure to categorize naphthalene as a cancer risk. This occurred, Rotkin-Ellman says, “despite the fact that the National Toxicology Program has listed naphthalene as likely to be a carcinogen, and it is considered by the state of California to cause cancer.”

When it comes to specific PAHs such as naphthalene, most Gulf data show levels not only below LOCs but even below detection limits, Gohlke says. This is encouraging, but “you can’t do any kind of time-series analysis because you don’t have any data to work with on the individual PAHs,” she adds.

Knowing the total amount of PAHs would be helpful in making comparisons and determining whether levels are rising or falling, but such analysis is stymied by the fact that FDA reported totals and NOAA didn’t. Gohlke warns, however, that total PAH numbers shouldn’t be used to make any kind of health claims.

The target PAHs were chosen because of the available information on their health impacts, and those selected haven’t changed much from earlier spills. “A lot of research has been done on PAHs, and there are obviously more PAHs than those currently used in the risk assessment,” she says. “Whether we should be adding more PAHs to that battery is definitely under discussion.” NRDC also encourages expanded testing for other petroleum hydrocarbons.

Concerns have also been raised that FDA and NOAA did not appear to be interested in testing for metals. Just recently, FDA posted levels of metals for seafood samples collected between October 2010 and May 2011. “Testing showed that the levels of arsenic, cadmium, lead, and mercury were consistent with the background levels found in seafood not impacted by the oil spill and do not present a public health concern,” the agency states.

Although FDA offered no explanation for the metals testing, posting of the results did come after requests and recommendations made by NRDC, the Institute of Medicine, and Gohlke and coworkers. Critics had complained of a lack of transparency on the part of regulators. Both Rotkin-Ellman and Gohlke say the situation has gotten better.

“We have seen some improvements in the level of disclosure,” Rotkin-Ellman says. “In response to a lot of community pressure, FDA has gotten better about putting data up on its website and is doing it faster.” FDA’s explanations of its data and plans for continued monitoring are less clear, she adds. NOAA also posts data on its website.

After other oil spills, increased PAH levels have been detected in fish and shellfish up to several years out, according to Gohlke. She and other researchers hope for long-term monitoring programs for PAHs, DOSS, and metals, especially in light of potential recontamination from uncaptured oil and unknowns concerning the environmental fate of dispersants.

For now, it appears that regulators will continue monitoring for at least a few months more. FDA’s ongoing surveillance program involves testing seafood at processing locations rather than from identified areas in the Gulf. The agency’s risk-based program targets oysters, crabs, and shrimp because they retain contaminants longer than finfish do.

NOAA conducts some dockside testing and also goes back to previously contaminated areas to collect seafood for testing. In November 2010, it closed more than 4,000 sq miles that had been opened off the Louisiana coast after a fisherman brought up tar balls in his nets. Sensory and chemical tests showed that the seafood was clean, and the area was reopened again.

In March 2011, NOAA said it would continue testing through the summer. Reports indicate that FDA will conduct its testing until October 2012. And since late 2010, Gulf state agencies have been using tens of millions of dollars paid by BP for three years of seafood testing and marketing campaigns.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2011 American Chemical Society
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