One of the reasons for concern about the consumption of  yellowfin tuna  is the presence of so-called heavy metals. Heavy metals are contaminants of great environmental concern because of their multiple origins (natural and anthropogenic), their ability to accumulate in organs and tissues, and the deleterious effects they can cause in organisms. Studies on the accumulation of metals in marine populations, such as fish, have increased in importance because of the risk to human health when metal-contaminated fish are consumed. The present work aimed to verify the concentrations of cadmium (Cd), mercury (Hg) and lead (Pb) in muscle tissue and liver of yellowfin tuna (Thunnus albacares) and dolphinfish (Coryphaena hippurus) from the eastern Pacific (1).

A comprehensive review of literature and studies on mercury concentrations in 36 fish species showed that (2) fish such as tuna and swordfish have the highest concentrations of CH₃Hg or Methylmercury and mackerel and sardines from the Mediterranean Sea contain more CH₃Hg than other harvesting areas (3). All these and other data are detailed in this study (4).

References________________________________________________________________________

(1) Araújo CVM, Cedeño-Macias LA. Heavy metals in yellowfin tuna (Thunnus albacares) and common dolphinfish (Coryphaena hippurus) landed on the Ecuadorian coast. Sci Total Environ. 2016 Jan 15;541:149-154. doi: 10.1016/j.scitotenv.2015.09.090. 

(2) Pirrone N.; Mahaffey K. R. Dynamics of Mercury Pollution on Regional and Global Scales; Springer Publishers: New York, 2005; p 744.

(3) Pirrone N.; Mason R. Mercury Fate and Transport in the Global Atmosphere: Emissions, Measurements and Models; Springer: New York; p 637.

(4) Driscoll CT, Mason RP, Chan HM, Jacob DJ, Pirrone N. Mercury as a global pollutant: sources, pathways, and effects. Environ Sci Technol. 2013 May 21;47(10):4967-83. doi: 10.1021/es305071v.