The content of environmental toxins in shellfish is low, and for the most part, their microbiological quality is good. The only exception is the common whelk, which has a high content of cadmium.
In 2011, NIFES analysed 384 samples of shellfish for E. coli, enterococci and Salmonella on behalf of the Norwegian Food Safety Authority. The samples comprised 312 mussels, 40 scallops, 21 oysters, four horse mussels and seven periwinkles.
Eighty-four per cent of the 384 samples had a content of E. coli that was below the European Union’s upper limits for areas where shellfish are gathered for human consumption. Enterococci were demonstrated in five of the 369 samples tested, in all cases in low concentrations. No Salmonella were found in any of the 38 samples analysed by NIFES.
READ THE REPORT. Good shellfish quality in 2011. Photo: NIFES
Confirmation of previous findings
Heavy metals and organic environmental toxins were also analysed in 43 samples of mussels, three of oysters, five of scallops, seven of periwinkles and five of whelks. Apart from the whelks, none of them contained organic environmental toxins that lay outwith European Union or Norwegian upper limits. These results confirm previous findings.
In the wake of the M/V “Godafoss” grounding and oil-spill off Hvaler in February 2011, 54 mussel, scallop, oyster and periwinkle samples were analysed for heavy metals and organic environmental toxins. None of the samples revealed values above food safety thresholds.
High cadmium content in whole whelks
The samples of whole whelks had a cadmium content that exceeded upper limiting values, with the highest value as much as ten times beyond the permissible limit.
“The cadmium content of the muscle, i.e. the foot of the animal, was much lower and well within the upper limit,” says NIFES scientist Arne Duinker.
Cadmium is a natural component of seawater, and some species take up more of this element than others. High cadmium levels can also be the result of pollution. NIFES will look at the cadmium content of whelks in more detail in 2012.
You can read about cadmium in horse mussels and scallops here.
Annual shellfish monitoring programme
The purpose of the annual shellfish inspection programme, which is carried out by NIFES in collaboration with the Norwegian Food Safety Authority, is to certify that shellfish that are gathered for human consumption do not come from areas that are contaminated by potentially harmful organisms or that contain excessive levels of undesirable substances.
Shellfish can take up gut bacteria if these exist in the waters where they grow. Analyses can therefore reveal whether the area in which shellfish are growing is contaminated by sewage, and as such is a potential hazard to health. The area concerned is classified in terms of its microbiological quality, and of whether shellfish can be harvested directly for human consumption (A-areas) or must be either set out again or heat-treated (B- and C-areas).
The shellfish inspection programme also covers monitoring toxic algae and algae that produce toxins. The programme submits regular reports to the Food Safety Authority.
NIFES has been monitoring shellfish systematically since 1999.
Contact: Arne Duinker
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