Heavy metal: Not so fishy

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  • Published: Nov 15, 2013
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Heavy metal: Not so fishy

Fish tests

Fishing boat photo by David Bradley There is ongoing concern regarding levels of heavy metal contamination of edible fish. However, a study of Atlantic species by a team in Morocco using atomic absorption spectroscopy shows that although cadmium, lead and mercury are present, concentrations are well below the safety thresholds published by the European Union.

There is ongoing concern regarding levels of heavy metal contamination of edible fish. However, a study of Atlantic species by a team in Morocco using atomic absorption spectroscopy shows that although cadmium, lead and mercury are present, concentrations are well below the safety thresholds published by the European Union.

Adil Chahid and Taoufiq Bouzid of the National Office of Food Safety in Agadir and Mustapha Hilali and Abdeljalil Benlhachimi of the Ibn Zohr University, also in Agadir, explain that while fish is eaten as a tasty and nutritious part of the human diet across the globe, there are concerns regarding its safety because many species are known to accumulate heavy metals and metalloids in their tissues; levels rise up the food chain. Many of these elements are present naturally in the marine environment but there is an inevitably raised burden from industrial wastewater, incineration processes, mining and other human activities.

Worrying metals

Among the most worrying metals that might accumulate in edible fish are cadmium, lead and mercury. Cadmium is known to occur only at trace levels in the marine environment, but it does bioaccumulate and can have a detrimental effect on the kidneys, lungs, bone, placenta, brain and central nervous system. Lead causes renal failure, liver damage and developmental problems. While mercury can cause serious to the brain kidneys and developing foetus.

The team explains that as part of a monitoring program, lead (Pb) cadmium (Cd) and mercury (Hg) concentrations in nine edible Atlantic fish species landed at ports in the southern Kingdom of Morocco - Sardina pilchardus (European pilchard), Scomber scombrus (Atlantic mackerel), Plectorhinchus mediterraneus (the Mediterranean sweetlips), Trachurus trachurus (horse mackerel), Octopus vulgaris (common octopus), Boops boops (bogue seabream), Sarda sarda (Atlantic bonito), Trisopterus capelanus and Conger conger (European conger eel) - were analysed for these trace elements. Levels of lead and cadmium were determined using graphite furnace atomic absorption spectrometry (GFAAS) while mercury was analysed by cold vapour atomic absorption spectrometry (CVAAS).

Fish food

The researchers report data on concentrations for wet weight. Cd, Pb and Hg in fish muscle were 0.009 to 0.036, 0.013 to 0.114 and 0.049 to 0.194 micrograms per gram of tissue, respectively. The legal limits are 0.1, 0.3 and 0.5 micrograms per gram, respectively.

"The present study showed that different metals were present in the sample at different levels but within the maximum residual levels prescribed by the EU for the fish and shellfish from these areas, in general, should cause no health problems for consumers," the team says.

"This is only the beginning," Adil told us, "as we went further by determining the dose tolerable weekly for these metals, and simultaneously determining a study on the variation of metals in different organs of the fish."

Related Links

Food Chem 2014, 147, 357-360: "Contents of cadmium, mercury and lead in fish from the Atlantic sea (Morocco) determined by atomic absorption spectrometry"

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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