Cheeky sharks: Heavy metal low

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  • Published: Sep 15, 2016
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Cheeky sharks: Heavy metal low

Edible muscles

Atomic absorption spectroscopy (AAS) on edible muscle of whitecheek shark, Carcharhinus dussumieri from the Persian Gulf suggests there is no problem with heavy metal contamination of this food.

Atomic absorption spectroscopy (AAS) on edible muscle of the whitecheek shark, Carcharhinus dussumieri (not pictured), also known as the widemouth blackspot shark, found widely distributed in the Persian Gulf suggests there is no problem with heavy metal contamination of this particular food stuff and that the benefits of seafood outweigh the low risk in this case.

There has been much worrying talk in the media over the last few decades of heavy metal contamination of the edible meat from shark, tuna, swordfish and other species. This supposed crisis exists in parallel with calls to eat more fish and less red meat from terrestrial species for the sake of our health. Of particular concern has been contamination of fish flesh with mercury from seas and oceans where waste from shipping, the oil industry and other heavy polluters is of a high density.

Turning the tide

Now, writing in the November 2016 issue of the journal Food and Chemical Toxicology, an international team turns the tide on the deceived wisdom, at least for one particular shark species. Milad Adel and Masoud Mahjoub of the Iranian Fisheries Science Research Institute (IFSRI), in Tehran, Gea Oliveri Conti, Chiara Copat, and Margherita Ferrante of the University of Catania, Italy, and Maryam Dadar of the Agricultural Research, Education and Extension Organization (AREEO), in Karaj, Iran, have used AAS to analyse for any trace elements present in the meat of C. dussumieri and found that the metal concentrations of cadmium, copper, lead, mercury, and zinc did not exceed the European limits for human consumption. Moreover, the average estimated daily intake (EDI) of all metals studies was lower than the provisional tolerable daily intake (PTDI) given by the World Health Organisation (WHO). Finally, the target hazard quotient (THQ) was less than one.

Seafood diet

"Aquatic environments are continuously threatened by inorganic contaminants including trace metals and metalloids," the team says. Moreover, predatory species can lead to a magnification of metal contamination upward through the food chain from the microscopic species that first sequester metals from the sea to those that feed on these and thence to the carnivores, the sharks and others that eat those species in turn. Despite this, all of the metals tested were present at low concentration below recommended safety thresholds, the team reports and says that this suggests "no risk for human health derived from consumption" of this shark meat and given the purported health benefits over eating red meat, there is presumably no need to avoid this delicacy. Indeed, "Seafood is an important source of proteins and essential fatty acids necessary for a healthy human life," the team adds.

Related Links

Food Chem Toxicol 2016, 97, 135-140: "Heavy metal concentrations in edible muscle of whitecheek shark, Carcharhinus dussumieri (elasmobranchii, chondrichthyes) from the Persian Gulf: A food safety issue."

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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