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Listen to this siteThursday 10 February 2005
This research project analyses levels of chemical contaminants in shellfish from Scottish inshore and offshore harvesting sites.
Study Duration : January 2004 to September 2004
Contractor : Fisheries Research Services Marine Laboratory
The European Union (EU) Shellfish Hygiene Directive (91/492/EEC) includes the requirement to assess a range of elements of end product quality in shellfish offered for sale for human consumption. Therefore there is a need to conduct a targeted programme to provide current data on the concentrations of priority contaminants in harvested shellfish and to assess the contaminant levels in cultivated and natural populations of a number of shellfish species throughout Scottish coastal waters.
Mussels ( Mytilus edulis ), scallops ( Pecten maximus ) and oysters ( Crassostrea gigas ), were sampled during January and February 2004 from a number of production areas, and analysed to determine the soft tissue concentration of polycyclic aromatic hydrocarbon (PAH), trace metal (TM), chlorobiphenyl (CB) and organochlorine pesticide (OCP) residues.
A total of 36 shellfish samples, comprising 20 mussel samples, six oyster samples and 10 scallop samples, were collected during the period January to March 2004. The concentration of PAHs, trace metals, CBs and OCPs was determined in the soft tissues.
The total measured PAH concentration in 13 of the 20 mussel samples analysed was less than 150 ng g -1 wet weight. Four samples returned total PAH concentrations greater than 250 ng g -1 wet weight. Atypical results, either with respect to PAH concentration (eg Loch Stockinish) or PAH distribution (eg Loch Leven) were readily accounted for either in terms of a defined PAH pattern indicating a probable recent source of PAHs or known historical input to the area.
All but one sample of oysters contained PAHs at a concentration less than 100 ng g -1 wet weight.
All scallop adductor muscle samples contained PAHs at a concentration less than 50 ng g -1 wet weight. All but two samples of scallop gonad tissue contained PAHs at a concentration less than 100 ng g -1 wet weight. The PAH concentration in scallop gonad was, without exception, greater than in the corresponding adductor muscle.
Trace metal distribution in mussels, oysters and scallop tissues showed that, with a few exceptions, the concentrations generally do not exhibit a high variance between sites.
Some mussel samples exhibited Cu, Cd, Hg and Pb concentrations greater than the current OSPAR background concentrations.
Zinc concentrations in the oyster samples were greater than in the other shellfish tissues analysed.
In all tissues analysed, mercury concentrations were low, being at or below the limit of detection (0.015 µg g -1 wet weight).
The CB concentrations determined in 75% of the mussels were within the Environmental Assessment Criteria established by OSPAR for mussels (0.75 - 7.5 ng g -1 wet weight for the sum of ICES 7 CB congeners). Five mussel samples (25%) exceeded 7.5 ng g -1 wet weight. An EAC has not been established for either oysters or scallops, but CB concentrations were within the EAC established for mussels.
Although OCPs were detected in all shellfish analysed, concentrations of HCB and alpha-HCH were below the detection threshold or limit of quantification. Low concentrations of gamma-HCH were determined in mussel and oyster samples and in only two scallop gonad tissue samples. Dieldrin and DDT was detected in all mussel, oyster and scallop gonad tissue samples and in 70% of scallop adductor muscle samples. Chlordane was detected in all mussel, oyster and scallop gonad tissue samples and in 50% of scallop adductor muscle samples.
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency ( tel: 020 7276 8181/8182 or email:
library&info@foodstandards.gsi.gov.uk
)
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Email
: science@foodstandards.gsi.gov.uk
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