UNITED STATES: New research to investigate the factors that influence the levels of methylmercury contained in tuna, could help us understand why the concentrations of this compound vary by geographical region.
Inorganic mercury compounds are released into the atmosphere from natural sources, such as volcanoes, and human-based sources, such as fossil fuel combustion and gold mining. Some of these compounds settle onto oceans, where natural processes convert them into methylmercury. This substance is then naturally transferred to sea creatures, including tuna, which sometimes contain amounts exceeding food safety guidelines.
Researchers David Point, Anne Lorrain, Valérie Allain, and other colleagues, wanted to map regional variations in methylmercury levels in tuna and to investigate the biological, environmental and ecological factors that drive these variations.
The scientists studied bigeye, yellowfin and albacore tuna captured in the Western and Central Pacific Ocean (WCPO)region.
The researchers found that methylmercury levels were below food safety guidelines for most of the samples. In addition, they confirmed earlier findings from other ocean regions that body size is the primary factor in determining contamination within a species, with bigger fish accumulating a higher concentration of methylmercury in their tissues than smaller fish.
They also found that sea-surface temperature and the depth of the ocean layer in which tuna feed, also affect this concentration.
The scientists who participated in the studu, published in the journal Environmental Science and Technology, believe that their results could help in evaluating the risks and benefits of eating tuna caught in a particular location, or tuna of different sizes.
The research recevied funding from the Grand Observatoire du Pacifique Sud, the Pacific Fund VACOPA project, the Pacific Community, Government of New Caledonia, the Institut de Recherche pour le Développement and the French National Research Agency MERTOX project.
Source: American Chemical Society