Ocean Pollutants Found in Tuna Weaken the Immune System

Exposure to certain contaminants blocks the body’s ability to expel toxins, a study has found.
A yellowfin tuna. (Photo: Taro Taylor/flickr)
Apr 16, 2016· 1 MIN READ
Emily J. Gertz is an associate editor for environment and wildlife at TakePart.

Eating seafood tainted with a class of common, long-lasting environmental contaminants can weaken the human body’s ability to defend itself against toxic substances, a new study has found.

A team of California scientists, led by Amro Hamdoun of the Scripps Institution of Oceanography, tested how exposure to 10 persistent organic pollutants, or POPs, affected an important cellular protein found in most animals and plants.

The pollutants, all detected in the past both in humans and in yellowfin tuna, included the upholstery flame retardant PBDE; pesticides such as dieldrin and DDT; and PCB, an industrial chemical.

The protein, called P-gp, usually ejects toxins from the body. But the team found that all 10 pollutants weakened P-gp’s protective function. One form of flame retardant, PBDE-100, bound itself to the protein and blocked it from transporting the toxin out of the body cell.

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“When we eat contaminated fish, we could be reducing the effectiveness of this critical defense system in our bodies,” said Hamdoun in a statement.

The yellowfin tuna used in the study were caught in the northern Gulf of Mexico. It is one of the most popular fish served as sushi, with fishermen catching more than 1.1 million tons of yellowfin each year.

POPs are known to cause reproductive, immune system, and neurological impairments in humans and other animals. Their chemical stability is part of what has made them valuable in agriculture and industry, but it also means that they decompose slowly in the environment. That has allowed POPs to enter, spread, and concentrate in the food chain years and even decades after initial use.

POPs have been found almost everywhere on Earth, from a remote Arctic island near Norway to the middle of the Pacific Ocean, and in the bodies of killer whales off the coast of Europe. They have been implicated in the global die-off of honeybee colonies. But global agreements to reduce and phase out some POPs may be having a positive effect.

“We are the only species that can influence entire food chains and habitats,” said Jacob James of the Waitt Foundation, the study’s funder, in a statement. “We must act more responsibly in the design and use of chemicals in our environment.”

The study was published Friday in the journal Science Advances.