Looking for Oil in Seafood – But Not Finding Any!
By Jo Marie Cook
Since April, 2010 when the Deepwater Horizon explosion spilled thousands of gallons of oil into the Gulf of Mexico, knowledgeable and experienced food safety chemists from National Oceanic and Atmospheric Administration (NOAA), the Food and Drug Administration (FDA) and several state laboratories including the Florida Department of Agriculture and Consumer Services (FDACS), have been working closely together to detect any oil contamination in Gulf harvested seafood. Although Florida’s long coastline was largely spared, oil did come ashore in the western panhandle. An area from Pensacola to Cape San Blas was closed to fishing for several weeks from early June to September 2, 2010.
Figure 1 shows a map provided by NOAA summarizing the sampling and analyses they have conducted to assure that seafood continues to be safe. 1. The outline of this map shows the areas of the Gulf that were closed for some time following the spill. Since the beginning of this crisis, the FDA and many state labs, including FDACS have also been sampling and analyzing seafood from state waters.
2. Figure 2 shows the dates when areas were reopened for fishing from August 10 to November 15, 2010. 3. Extensive work was done to assure that seafood was safe before these areas were opened to fishing.
Following the oil spill, federal and state governments applied multiple strategies to assure seafood safety. Areas of the Gulf with visible oil, including large buffer zones around it, were closed to fishing. Physical and chemical barriers in the form of oil-catching booms and surfactant dispersants were used to contain and remove the oil. Once visual sources of contamination were removed, sensory evaluations of seafood were conducted, by sight, smell and taste. NOAA has long used trained sensory evaluators to detect seafood contamination and provided this training to FDA and state analysts. Seafood processors also use sensory evaluation to verify fish freshness and safety as part of the many precautions put in place to assure they sell the most wholesome seafood to you including careful evaluation and control of hazards as described in FDA guidelines. 4 Any good chef can attest that the power of the human sense of taste and smell is still more sensitive than many chemical instruments. Any of us can do the same. “If is smells bad, don’t eat it!”
Once passing a sensory evaluation, seafood was tested for the most toxic of the chemicals found in oil, the polycyclic aromatic hydrocarbons or PAHs. Seafood areas were opened for fishing only after sensitive chemical testing indicated oil was not present. If seafood does not look, smell or taste of oil, these tests are designed to determine if oil chemicals have been absorbed by the eatable tissues. Seafood samples are also screened for the dispersant, dioctylsulfosuccinate (DOSS). FDA has established clear guidelines for acceptable levels of these compounds. (Table 1) 5 Why are any levels acceptable? Aromatic hydrocarbons such as the PAHs originate from multiple sources. For example, because we all use gasoline in our vehicles, low levels of some PAHs are common in our everyday environment. The gas chromatographic mass spectrophotometric instrumentation used in laboratory analysis of PAHs can easily pick up background contamination, even from a truck backing up to the laboratory loading dock. The dispersant chemicals are also commonly used soap-like chemicals which have very low toxicity. Much is already known about the safety of oil-based chemicals and dispersants. Toxicologists have applied multiple safety factors to their guidelines when establishing their levels of concern to assure that seafood is safe to eat, even for small children. Much more about PAHs, DOSS and their safety can be found at www.fda.gov and www.noaa.gov.
Here at FDACS, significant resources in people, time and instrumentation have been dedicated to the detection of very low levels of oil contamination. So far the evidence is just not there. Oil contamination is not being detected in the eatable portions of seafood sold for consumption. That doesn’t mean that a storm or some other unexpected occurrence might not lead to future problems so we continue to be vigilant. Supported by funding from BP Exploration and Production, the FDACS Bureau of Chemical Residue Laboratories is hiring additional analysts and purchasing instrumentation to allow them to provide surveillance and analysis of seafood for several years to come. Other scientists are also investigating the effects of the oil spill on the environment and the overall health and sustainability of the seafood species and their habitat. Scientists also continue to investigate many other diseases and environmental effects that may affect the safety of seafood but are unrelated to oil contamination. Table 2 6 summarizes FDACS seafood analyses. More detailed information can be found on the Department website at www.freshfromflorida.com.
The challenge for the laboratory is to isolate the analysis and assure minimal background interference. The laboratory location, equipment and handling must also be carefully controlled because many plastics are processed using oil based chemicals and can also be a source of background. For example, the seafood is collected and wrapped in foil to prevent any contamination from plastic wrappings. How do we assure that we are detecting the chemicals from the seafood and not from other sources? Each set of samples analyzed is accompanied by blanks which are known to be PAH-free as well as reference materials which contain know amounts of PAHs. These positive and negative quality control samples help assure that each set of analyses are accurate.
There are several analytical methods employed to detect oil contamination as well as the dispersant, dioctylsulfosuccinate, which was one of the chemicals present in both of the dispersants used to control the Deepwater Horizon spill. The first method used was developed by NOAA for the analysis of PAHs, pesticides and other contaminants in seafood. This method has been used for many years to evaluate the safety of seafood after the Exon Valdez spill and to routinely evaluate the safety of oysters. It is a tried and proven method that provides valuable and reliable data. The NOAA method, however, is very time and resource intensive, taking two people as much as a week to screen 15 samples. For that reason, a screening method was developed by FDA and adopted by FDACS to allow screening of many more samples in a shorter period of time.
A portion of all the samples screened are also routinely analyzed by the NOAA method to assure that no contamination is being missed by screening. In addition, if there are any findings of concern found using the screening method, they are reanalyzed by the NOAA.
Jo Marie Cook has served as the Chief of the Bureau of Chemical Residue Laboratories, Division of Food Safety in the Florida Department of Agriculture and Consumer Services (FDACS) since 2005.