Humans have used dried meats, fish, and fruits as a portable nutrition source for centuries. Because omega 3 fatty acids in fish are recognized as having antioxidant and anti inflammatory properties found to be beneficial for good health, many consumers are looking to fish as their main source of protein. Fish products on the market can now be obtained as fresh, frozen, canned, smoked, or dried. Unfortunately, contaminants such as methylmercury can accumulate in some species of fish.
The United States Food and Drug Administration (FDA) regulates commercial fish and fisheries products, which includes jerky. Non-commercial fish are regulated by the United States Environmental Protection Agency (EPA). The current FDA and EPA joint advisory addresses "fish" and "shellfish," and their consumption for women who are pregnant, or want to become pregnant, nursing mothers, and young children. The advisory states they should not eat shark, swordfish, king mackerel, or tilefish because these species contain high levels of mercury. They are advised to eat up to twelve ounces (340 g) a week of a variety of fish and shellfish that are lower in mercury, such as shrimp, canned light tuna, salmon, Pollock, and catfish. They may also eat up to six ounces (170 g) of albacore ("white") tuna per week, as it can contain higher mercury levels .
The current allowable mercury level in commercial fish and fisheries products directed by the FDA is 1.0 μg/g. Of historic interest, this limit was originally derived form the conclusion of a court trial in 1977 with Anderson Seafood Inc, a swordfish proprietor, and the FDA. Data used to establish this level came from a massive poisoning episode that occurred in Iraq in 1971-2 from an organic mercury fungicide placed on grain, whereby the people used this grain for their daily bread consumption instead of for planting. In the court transcripts, there was much discussion as to whether a minimal clinical effect level could be established from the Iraqi data. Regardless, the court proceedings concluded that a minimal clinical effect level for humans was determined to be 400 μg/l whole blood. This allowed for the mercury limit set for fish of 0.5 μg/g to be raised to 1.0 μg/g, thus allowing fish greater than 0.5 μg/g to be sold in the commercial market [2, 3].
The EPA still maintains a mercury limit set for non-commercial fish of 0.5 μg/g. In addition, since the FDA vs. Anderson Seafood Inc. trial, the EPA established a human tolerable limit for mercury exposure of 0.1 μg/kg body weight/day. For a 60 kg (132 lb) person, this would amount to an average of 42 μg of mercury allowed per week. Consistently consuming mercury at this amount is estimated to result in a blood mercury level of about 4-5 μg/l . The FDA though, has not adopted the EPA's tolerable limit.
Mercury concentrations in some fish species can be quite variable, as mercury accumulates in the food chain. Longer lifespans, stronger predatory behavior, and greater number of miles traveled to diverse areas of exposure, are just a few reasons for this variability. Methylmercury is the predominant mercurial contaminant in fish. It can penetrate every cell in the body where it becomes strongly bound to tissues. No known cooking methods can remove it from fish tissue. As to fish products that have been dehydrated, the authors hypothesized that fish jerky would likely have mercury concentrations that were several times higher than found in fresh fish.