Time trend of Butyl- and Phenyl-Tin contamination in organisms of the Lagoon of Venice (1999-2003)

Overview

Zanon and colleagues measured butyltin and phenyltin compounds in edible mussels (Mytilus galloprovincialis) and clams (Tapes spp.) from the Lagoon of Venice before the European organotin-antifouling restrictions took full effect. The source reports organotin species as cation concentrations on a dry-weight basis, with a later comparison to a wet-weight TBT residue level. These are organotin occurrence values and must not be collapsed into total elemental tin or inorganic tin.

Key numbers

The abstract reports higher TBT concentrations in mussels than clams:

Tables 2 and 3 report autumnal butyltin concentrations by station and year in μg kg−1 d.w.:

The discussion highlights the Chioggia-area mussel subset as TBT=187-6,666; DBT=80-4,187; MBT=31-1,538 μg kg−1 d.w.. Across the three survey years, the authors report no increase in average concentrations of summed butyltins (TBT + DBT + MBT) in either species (ANOVA, p>0.05), while TBT alone was higher in Mytilus than in Tapes (ANOVA, p<0.05).

Method performance values were procedure recoveries of TBT=89%, DBT=92%, and MBT=92% using certified reference material CRM 477. Detection limits from ten blanks were TBT=12, DBT=12, MBT=12, TPhT=5, DPhT=7, and MPhT=12 μg kg−1d.w..

For the population of Venice, the paper estimated average intake as 70 g-seafood day−1, of which mollusks were about 44% of the total catch, giving about 31 g-mollusks day−1. The source-derived Tolerable Average Residue Level was 487 μg Kg−1 w.w.; the authors state that some wet-weight TBT values exceeded it at stations 4 in 1999, 3 and 11 in 2001, and 1, 10, 11, and 14 in 2003, especially for M. galloprovincialis.

Methods (brief)

The study collected mussels and clams from Lagoon of Venice stations during 1999, 2001, and 2003. About 200 organisms of the same size were collected at each station, drained, dissected to edible tissue, homogenized, frozen at -18°C, freeze-dried, and stored at -20°C. Organotin compounds were extracted from 500 mg dry tissue, derivatized with pentylmagnesium bromide, purified on Florisil, and analyzed by high-resolution gas chromatography-low-resolution mass spectrometry (HRGC-LRMS) using an ion-trap detector. Reported species include TBT, DBT, MBT, TPhT, DPhT, and MPhT; the key tables emphasize butyltins.

Implications

This source contributes organotin occurrence evidence for commercially used bivalve shellfish in the Lagoon of Venice. The edible-organism data support seafood and shellfish routing for organotin-specific tin species, especially TBT/DBT/MBT in mussels and clams. Downstream extraction should preserve the dry-weight versus wet-weight distinction and the TBT+ cation basis, and should not pool these values as inorganic tin or total tin (Sn).

Update history

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