Bioaccumulation of trace metals in Hexaplex trunculus: spatial and temporal trends from 2004 to 2011 along the Tunisian coast

Cd, Zn, Cu, As, Fe, Cr, Ni, Al, and Pb were analyzed in the edible and inedible parts of the muricid gastropod Hexaplex trunculus sampled along the Tunisian coast in 2004, 2007, and 2011. The concentration ranges (μg/g dry weight) in the whole soft tissue were 0.1–19.2 for Cd, 198.7–564.6 for Zn, 31.9–363.1 for Cu, 12.8–177.8 for As, 35.4–179.0 for Fe, 0.0–5.8 for Cr, 0.1–4.6 for Ni, 1.0–41.4 for Al, and 0.0–0.6 for Pb. The highest concentrations were recorded in Gabès for Cd, Menzel Jemil for Zn and Cu, Bizerte channel for As, Zarat for Cr and Pb, and Tunis North Lake for Fe, Al, and Ni. The European standards compiled by FAO for mollusks were exceeded in several localities. The temporal trends revealed a decreasing metal contamination in most sampling stations from 2004 to 2011. The calculated intake of metals (μg/week/kg body weight) through human consumption of the snail edible portion varied from 0.0 to 4.4 of Cd, 55.9 to 172.1 of Zn, 8.7 to 92.7 of Cu, 3.0 to 42.6 of As, 9.5 to 49.1 of Fe, 0.0 to 1.52 of Cr, 0.0 to 1.4 of Ni, and 0.3 to 11.4 of Al. Comparison of these metal intakes with those of the standard provisional tolerable weekly intake (PTWI) values stipulated by the WHO recommends precaution in terms of human consumption of this marine snail.