Toxins in Tuna: Modern Pollutants


Industrial chemicals pollute our oceans, including our seafood. Photo: Brian J. Skerry / National Geographic Stock

Grant Recipient: Scripps Institution of Oceanography
Project Support: Assessing Modern Global Pollution of Seafood
Term: 2011 – 2013

In the past century, humans have put 83,000 synthetic industrial compounds into the environment. 5000 of these chemicals are high production volume chemicals, produced at volumes of thousands of metric tonnes annually. We have also dramatically changed the environmental levels of natural harmful compounds such as carbon dioxide and mercury; indeed two-thirds of the mercury in the atmosphere today is from our use of coal for energy. Many modern industrial compounds, such as pharmaceuticals, perfluorocarbons (PFC; teflon) and polybrominated diphenylethers (PBDE; flame retardants), are highly persistent.

The oceans are a repository for global pollutants. In turn, our own exposure to these ocean pollutants is often directly linked to our consumption of seafood. For example, elemental mercury in the atmosphere is deposited in the oceans through atmospheric processes and converted to organic mercury by microbes in sediments. Organic mercury persists, by binding to intracellular proteins, and rapidly moves up the food chain where it accumulates to high levels in long-lived fish. In turn, we humans are exposed to mercury when we eat those fish. There is urgent need to measure the scale of the ocean pollution problem and to determine the extent to which it presents a threat to human and environmental health through consumption of seafood.


Through this project, a global map of distribution of key contaminants in yellowfin tuna will be generated. These data will describe robustly whether or not 'pollution knows borders', namely whether any of the world's seafood sources are beyond the influence of chemical pollution.

Project Goal

The overall goal of this project is to estimate levels and distributions of modern industrial chemicals in the global seafood supply. The principal focus will be on one common fishery, the yellowfin tuna. Yellowfin tuna is among the most important fisheries targets worldwide, supporting fishing activities worldwide in tropical and subtropical seas. Approximately one million metric tonnes of yellowfin tuna are caught annually, making up one of the largest single-species contributions to total worldwide finfish consumption (approximately 2% of the total by yellowfin tuna alone). Yellowfin tuna tend to school in shallow waters and thus are likely to be regularly exposed to common sources of marine pollution that are concentrated in the shallow depths of the ocean.

During the first phase of the study, an unbiased chemical screen of yellowfin tuna will be conducted to identify the types and range of chemicals found in these fish. In the second phase, the study will amplify on this screen with targeted analysis of the major problem chemicals generating a large, statistically robust dataset on these common pollutants in yellowfin. They anticipate focusing on modern organic pollutants, including PBDEs, PFCs and one toxic metal, mercury. The study will explore the scope of the problem by comparing contaminant levels in fish across the globe, asking the question whether any fish, even those from the most remote areas of the planet, are free from contamination by modern chemicals.

This project will give us a better understanding of the scope of the seafood pollution, specifically focusing on identification of modern industrial chemicals. This proposal targets a gap in knowledge of how industrial chemistry influences our food supply through global marine pollution.

A Call for Support

Help is needed in collecting yellowfin tuna samples from across the globe. Do you have access to locally-caught yellowfin tuna? If so, a collection kit can be sent and you can help in expanding the map. Please contact Stuart Sandin ( or Amro Hamdoun (


Scripps Institution of Oceanography Website

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