Which fish and shellfish accumulate the most toxic metals?

Mercury, cadmium and lead are some of the most persistent toxic metals in the food chain, which can pose a health risk to those who feed on animals that accumulate them. A study published in 2014, carried out by researchers at the University of Granada (UGR), proved a detailed analysis of the fish and shellfish that accumulated these substances the most. 

Researchers analysed 485 samples from 43 different species, of which 25 were fresh fish, 12 were canned fish and 6 were frozen fish. Of the species analyzed, 18 per cent came from fishing grounds in Andalusia, 42 per cent from the rest of Spain, 10 per cent from Europe, and 30 per cent from the rest of the world (since species such as panga, perch or frozen squid came from countries such as Vietnam, Tanzania or Argentina, respectively). 

Values below the maximum permitted limits

The analysis verified that the average concentration of mercury, cadmium, lead, tin and arsenic (the most toxic metals, according to the Spanish Agency for Food Safety and Nutrition) found in the species analysed were below the limits permitted by the European Food Safety Authority (EFSA). In fact, only 6 of the 485 samples analysed (1.24%) exceeded the maximum limits, while in 174 (36%) the levels of toxic metals were even lower than detectable values.

In short, scientists observed that dogfish, swordfish, mussels and cockles are the species of fish and shellfish that accumulate the greatest amount of toxic metals, such as mercury and lead. In contrast, panga (traditionally considered one of the most contaminated species) and frozen cod are the two safest types of fish to eat.

Food safety

The main author of this research, Fernando Gil Hernandez, Professor of Toxicology at the UGR, recommends, especially to pregnant women and children, "diversify the consumption of fish and seafood, and not restrict the consumption of any specific species. Gil also points out that it is very important "to take into account the presence of selenium, an antioxidant that prevents cardiovascular diseases, and that is present in salmon and sardines, making them two species highly recommended for consumption", containing a very low amount of mercury and a significant proportion of omega 3 fatty acids whose beneficial effects for the body have been demonstrated on multiple occasions. In short, the advantages of eating fish outweigh the disadvantages and the key is to diversify.

This is a very extensive study that analyzes the levels of toxic metals in shellfish and fish, and the only one carried out in Andalusia. Its conclusions were published in the specialized magazine Environment International. 

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