Gladstone Fish Health Investigation 2011 - 2012 - Western Basin ...

Further scallop samples were collected in February 2012 from both Bundaberg and the SpoilGrounds offshore from Gladstone. These scallops appeared healthy, were frozen andforwarded to Biosecurity Queensland for residue testing.Histopathology and chemical residue testingScallops collected from offshore of Gladstone and offshore from Bundaberg (referencesamples) in October and November 2011 were examined histologically and were normal inall organs and tissues, with some parasitic infestation internally and in the gills of scallopsfrom both sites. Composite samples of scallops from Bundaberg and Gladstone Harbourshowed very little difference in tissue metal concentrations. Lead, mercury and silver were allbelow detection limits and, of the remaining 10 metals, only iron differed to any extentbetween samples, being higher in the reference site. No organic chemicals were detected.Scallops collected in February 2012 were tested for relative concentrations of total andinorganic arsenic in tissues using four samples: two with pooled adductor muscles frommultiple individual scallops and two with pooled visceral tissues. No organic contaminantswere detected in any scallop samples. Metal concentrations were similar in the samplesfrom Gladstone and Bundaberg except for iron, aluminium, nickel and copper, all of whichwere higher in the Bundaberg (reference) samples.In testing for metal residue levels, arsenic levels were reported for total arsenic. However, insome instances, the appropriate standards are set for inorganic arsenic, and total arsenicshould not be directly compared with standards for inorganic arsenic. On the basis of the firsttest results, this matter was further investigated to determine if there was a risk to humanhealth. Results showed that the level for inorganic arsenic (As) in the two muscle sampleswas higher than the maximum level (ML) set in the Australia New Zealand Food StandardsCode. The current legal limit for inorganic arsenic in molluscs is 1 mg/kg (wet weight), whichis set out in the Table to Clause 2 of Standard 1.4.1 of the Code. The test results reported bythe Queensland Health Forensic and Scientific Services Laboratory that are above the MLare as follows: Bundaberg scallop muscle: 1.5 mg/kg as inorganic As (wet weight),Gladstone scallop muscle: 1.9 mg/kg as inorganic As (wet weight).Inorganic As is the combination of Arsenite (AsIII) as As (wet weight) and Arsenate (AsV) asAs (wet weight). For this particular scallop species, the viscera are not considered to be partof the edible portion of the animal and therefore the Code does not apply to these samples.Representatives from Queensland Health, Department of Agriculture, Fisheries and Forestryand Safe Food Queensland discussed the results. To inform their discussion, the grouprequested additional information including sampling information; history of results fromNational Residue Surveys; comparisons with As levels in other foods and associated riskassessments; importing country requirements for seafood sourced from Australia; and typicalprocessing procedures involving washing shucked scallops with filtered and sterilisedseawater, which may reduce the final level of As in market-ready scallops.The conclusion reached by these representatives on the significance of the test results wasthat they do not present an acute health risk. It is the chronic, cumulative effects of theexcess intake of As that could potentially be a concern. However, the frequency and level atwhich scallops are consumed indicates it is unlikely to be a public health issue.71