# Metal Levels in Crab Sentinel Species from the Mediterranean Sea: Safety and Toxicological Risk Assessment

## TL;DR

This study assesses metal contamination in three crab species from the Mediterranean Sea to evaluate environmental pollution and health risks.

## Contribution

The study introduces a toxicological risk assessment framework for crabs as sentinel species in the Mediterranean Sea.

## Key findings

- Low metal exposure levels were found in crab tissues, indicating minimal risk to their health.
- Residual levels of Hg, Pb, and As exceeded maximum residue limits, highlighting the need for ongoing monitoring.
- Metal Pollution Index and correlation coefficient suggest low contamination in the marine ecosystem.

## Abstract

The assessment of metal contamination in marine species represents an important tool to monitor the environment pollution and the consequent risk of exposure for aquatic species. Among these marine species, crabs can be considered as the valid sentinel species of the marine environment due to their ability to accumulate pollutants in their tissues. In this study, the content of metals and metalloids (Hg, Pb, Cd, As, Cr, Mn and Ni) was assessed in three crab species, mainly distributed along the Mediterranean coastlines: warty crab (Eriphia verrucosa), brown crab (Cancer pagurus) and marbled crab (Pachygrapsus marmoratus). The analysis conducted in the carapace and the related pulp, gills, claws and bronchial muscle of crabs provided evidence of a low exposure to metals in the marine environment where the crabs lived and did not exhibit a significant risk for the health status of these species, as determined by the specific parameters of toxicological risk assessment. However, the presence of trace metals in carapace pulp needs to be monitored to determine the safety of these sea-foods.

The assessment of metal contamination in aquatic species represents an important tool to monitor the risk of exposure for these species in relation to marine pollution. Crabs are the sentinel species of the aquatic environment and are very sensitive to metal exposure because these inorganic contaminants can be easily absorbed into their exoskeleton and migrate into their inner tissues. The aim of this study was to assess the content of metals and metalloids (Hg, Pb, Cd, As, Cr, Mn and Ni) in species of warty crab (Eriphia verrucosa), brown crab (Cancer pagurus), and marbled crab (Pachygrapsus marmoratus), mainly distributed along the Mediterranean coastlines. The investigations, carried out on several parts of crabs (carapace and the related pulp, gills, claws and bronchial muscle) showed the presence of residual levels of metals and metalloids (Mn > Pb > Hg > As > Ni > Cr > Cd), correlated to the distribution of these elements in the marine environment and to the specific biological features of crabs. However, the values of Metal Pollution Index (MPI) suggested a low level of contamination of the marine ecosystem where these species were found, and the coefficient of correlation (K), a specific parameters of toxicological risk assessment, was indicative of crab health status. However, the residual levels of Hg, Pb and As above the MRL in all analyzed crab species underlined the importance of continuous monitoring studies on the safety of these sea-foods.