Alkyltins in farmed fish and shellfish

Overview

Amodio-Cocchieri and colleagues measured dibutyltin (DBT) and tributyltin (TBT) residues in farmed fish, free-living fish, farmed mussels, and free-living mussels sold or collected in Naples province, Italy. The study was conducted four years after Italy restricted organotin antifouling uses on small boats and in fish and shellfish aquaculture. These values are organotin species occurrence data; they must not be collapsed into total tin or inorganic tin.

Key numbers

Table 1 reports DBT and TBT in fish muscle as µg kg−1 wet wt. Concentrations are averages among positive samples, with ranges in parentheses; data were not corrected for recovery.

Table 2 reports DBT and TBT in mussels (Mytilus edulis) as µg kg−1 wet wt. All mussel samples were positive for both DBT and TBT.

The abstract summarizes farmed-fish DBT as present in 10% of samples, ranging from 1 to 26 µg kg−1 wet wt, with mean 10 µg kg−1; free-living fish DBT was present in 23% with average 2 µg kg−1 wet wt and range 1-4 µg kg−1 wet wt. Farmed-fish TBT was detected in 85%, ranging from 2 to 260 µg kg−1 wet wt, with mean 28 µg kg−1; free-living fish TBT was detected in 46%, with mean 39 µg kg−1 wet wt and range 1-93 µg kg−1 wet wt.

The results section states that farmed salmon samples were imported from Norway and had TBT mean 44 µg kg−1 wet wt with range 24-64 µg kg−1 wet wt. It also states that TBT residues exceeding 100 µg kg−1 were found only in some imported farmed fish, and that the most TBT-contaminated samples were among sea bass and gilthead bream specimens at 120-260 µg kg−1 wet wt.

Method performance values were DBT recovery 90%, TBT recovery 88%, spiked at 10 µg kg−1, and detection limits 1 µg kg−1 for both DBT and TBT chlorides. Values below the detection limit were assumed as zero.

Methods (brief)

Samples of farmed fish and common mussel were purchased from Naples-area retail stores during June 1997 to May 1998. Free-living fish controls included anchovy, mackerel, tuna, common sole, and pandora; free-living mussels from the Gulf of Naples were obtained directly from fishermen. Fish muscle tissues were analyzed, while entire mussel bodies were removed; 10 mussel specimens were pooled per analytical sample, fish below 100 g were pooled as three same-species specimens, and fish above 100 g were analyzed individually. DBT and TBT were determined using the Tsuda et al. method and a capillary gas chromatograph with flame photometric detector (GC-FPD). Reported values are wet-weight organotin species results and were not corrected for recovery.

Implications

This source provides direct organotin occurrence evidence for fish and mussels in the Naples market context shortly after antifouling restrictions. It supports seafood, fresh-fish, marine-fish, shellfish, and mussel routing for DBT and TBT as organotin tin species. Downstream extraction should preserve DBT and TBT as species-specific organotin values and should not use the concentrations as total elemental tin or inorganic tin.

Update history

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