Nov. 3, 2011Vol. 42, Issue 2

New Research

Research Reveals High Levels of Mercury in Fish Jerky

photo of Dr. Jane HightowerThe mercury research was conducted by Dr. Jane Hightower of San Francisco, author of the book, Diagnosis Mercury: Money, Politics and Poison, and geoscientist David Brown, chair of the Department of Geological and Environmental Sciences. Hightower is an alum of CSU, Chico.

Hightower has been investigating mercury in fish for years and was the first in the medical community to raise the red flag about how pervasive mercury is in top predator ocean fish such as tuna. She alerted the world to the health issue that mercury in fish presents, particularly for young children, nursing mothers and women who are or may become pregnant. Hightower and Brown extended the study to fish jerky, and the results were recently reported in the peer-reviewed Journal of Environmental Health.

Brown, whose expertise is in environmental monitoring, was responsible for identifying and acquiring samples of the fish jerky products. He also verified that the fish species investigated (marlin and ahi tuna) were accurately labeled through independent genetic identification.

“This is an important study in that it provides consumers with critical knowledge about the safety of food products that otherwise seem like healthy snacks,” said Brown. “Parents, in particular, need to know whether or not toxic substances are potentially present in foods they may be considering giving to their children.”

photo of Dave BrownHightower and Brown’s testing results showed that marlin jerky contained the most dangerous concentrations at 5 parts per million mercury, more than five times the limit of 1 part per million set by the U.S. Food and Drug Administration. Ahi tuna and salmon jerky contained mercury levels as high as .5 parts per million mercury.  

A 132-pound person eating a 1.5-ounce bag of marlin jerky at the average mercury concentration would result in an intake of mercury five times the weekly limit deemed safe by the FDA, said Brown. A total of 105 fish jerky samples were tested from 21 packages purchased at stores in Hawaii and California and from online vendors.  

The study found that

  • Only one package of marlin jerky had all five samples below the FDA level of 1 part per million
  • Six marlin jerky samples contained mercury greater than 10 parts per million
  • One marlin sample reached 28 parts per million
  • Most of the marlin samples (89%) exceeded the lower U.S. Environmental Protection Agency action level of .5 parts per million mercury
  • The 15 samples of ahi tuna had mercury concentrations ranging from 0.09-0.55 parts per million mercury
  • Mercury concentrations in 15 salmon samples ranged from 0.030-0.17 parts per million

As it does in other large, long-lived fish, mercury bioaccumulates in the flesh of marlin, a commercial and prized sport fish. When marlin is dried for jerky, mercury levels become concentrated. Marlin jerky and other fish jerky are sold at supermarkets around the United States and online and often marketed as a healthy food choice.

According to the U.S. Environmental Protection Agency, the number-one source of mercury exposure in the United States is contaminated seafood. Mercury ingestion can lead to memory loss, developmental and learning disorders, vision loss, heart disease, and, rarely, death.

The FDA is responsible for seafood safety and the regulation of mercury in commercial fish and fisheries products. However, the U.S. FDA has never tested mercury in fish jerky, so it is not included in its advisory for women and children not to eat high mercury fish such as swordfish and shark or to limit servings of albacore tuna.

Dr. Hightower received her undergraduate degrees in biology and chemistry from California State University, Chico in 1983 and graduated from the University of Illinois at Chicago Medical School in 1988. She did her residency at St. Mary’s Hospital and Medical Center in San Francisco. She is currently a doctor of internal medicine at California Pacific Medical Center in San Francisco.

Professor Dave Brown’s graduate training and research experience is in hydrology and soil science; he also has extensive coursework in biology. He has a broad range of applied research interests. His interest in Hightower’s work with mercury and the resulting collaboration came from his recent work on mining toxics released during the Gold Rush.