Mercury concentrations in reared Atlantic bluefin tuna and risk assessment for the consumers: To eat or not to eat?

•Size, age and rearing period of bluefin tuna affect the Hg accumulation.•Smaller and younger bluefin tuna show lower Hg concentrations than larger ones.•The longer the rearing period of bluefin tuna, the lower the Hg accumulation.•Mercury may pose a health risk to people consuming bluefin tuna (THQ > 1).•A maximum safe weekly consumption of 400 g is suggested. This study determines the levels of total mercury in muscle tissue from 268 reared Atlantic bluefin tuna in the Mediterranean Sea, detects variations on mercury concentrations in relation to biological parameters and rearing period and evaluates the health risk posed by fish consumption taking into consideration the size, age and rearing period. A total of 30 pooled samples were analyzed. The total Hg concentrations ranged from 0.49 to 1.60 mg/kg w.w. and showed a significant positive relationship with the size and age. It was found that the longer the rearing period, the lower the mercury concentration. The total Hg exceeded the maximum level defined by the European Commission Decision in a proportion of 40.0%. Since the value of Target Hazard Quotient was higher than 1 in all different groups (medium, large, 6 months and 18 months reared specimens), the maximum possible safe weekly consumption (400 g) is suggested.