Drivers of the accumulation of mercury and organochlorine pollutants in Mediterranean lean fish and dietary significance

Science of the Total Environment


An integrated assessment of lean fish of commercial value as Hg and organochlorine compound source into the population of the Balearic Islands were reported. Dependences between pollutant concentrations, trophic level, fish species, specimen weight and physical-chemical properties were evaluated.

Hg and total DDTs showed highest variability between fish species whereas PCBs and HCB displayed more constant median values. The organochlorine compounds found in highest concentrations were those with highest hydrophobicity, consistently with their higher bioaccumulation potential. These pollutant concentrations were higher in Mediterranean than Atlantic fish. Higher median total DDT and PCBs concentrations were also observed in the third than the second trophic level species. The observed concentrations were below the threshold recommended by the EU for human consumption (75 ng/g wet weight).

The Hg concentrations were higher in Mediterranean than Atlantic fish, with average values of 1.5 μg/g ww and 0.43 μg/g ww, respectively. Forty-one percent of the specimens from the Mediterranean and 25% of dusky grouper specimens from the Atlantic Ocean showed Hg concentrations above the EU recommended limits for human consumption, either 0.5 μg/g ww or 1 μg/g ww.

In the third trophic level, a significant dependence between median Hg concentrations and weight of each studied species was observed, which remained significant in specimen weight correlations. Independent species correlations of Hg concentrations vs individual weight generally showed higher concentrations at higher weight. Weight/size of the individuals was therefore an important factor for Hg accumulation but the trend was modulated by a species effect.

Extrapolation of the observed Hg concentrations in Mediterranean fish to Provisional Tolerable Weekly Intakes (PTWIs) showed higher intakes than the thresholds recommended by EFSA for adults and children, 110% and 140%, respectively. The estimated PTWIs for MeHg corresponded to 310% and 400% of the recommended threshold values. The PTWI values for organochlorine compounds were lower than those recommended.


  • 40% of Mediterranean lean fish had Hg concentrations above EU recommended values.
  • The levels of organochlorine compounds in all specimens were below the EU threshold.
  • Hg levels were correlated with specimen weight but the trend was species dependent.
  • The organochlorine compound concentrations were not correlated with specimen weight.
  • Mediterranean populations feeding on fish have higher EWI for Hg than the EFSA PTWIs.