Dioxins in U.S. Farm-Raised Catfish

Image Credit: Brent Moore / Flickr. This image has been modified.

Dioxins in U.S. Farm-Raised Catfish

Dioxins are highly toxic pollutants that accumulate in tissue fat. Almost all dioxins found in people who don’t work in toxic waste dumps or something similarly hazardous are believed to come from food, especially meat, milk, and fish, which account for about 95% of human exposure. We tend to only hear about it in the news, though, when there’s some mass poisoning.

In 1957, for example, millions of chickens began dying, blamed on toxic components in certain feed fats. Factory farming was taking off, and the industry needed cheap feed to fatten up the birds. They ended up using a toxic fleshing grease from hide stripping operations in the leather industry that were using dioxin-containing preservatives. A subsequent outbreak in 1969 resulted from a pipe mix-up at a refinery that was producing both pesticides and animal feed.

In the 1990’s, a supermarket survey found the highest concentrations of dioxins in farm-raised catfish. The source of dioxins was determined to be the feed, but that’s surprising, since catfish aren’t fed a lot of animal fat. Turns out it was dioxin-contaminated clay added to the feed as an anti-caking agent, which may have originally come from sewage sludge. The same contaminated feed was fed to chickens; so, what may have started out in sewage sludge ended up on the plates of consumers in the form of farm-raised catfish and chicken.

How widespread of a problem did it become? This affected five percent of U.S. poultry production; that’s people eating hundreds of millions of contaminated chickens. And if it’s in the chickens, it’s in the eggs. Elevated dioxin levels were found in chicken eggs too. When the source of the feed contamination was identified, the USDA estimated that less than 1% of animal feed was contaminated, but 1% of egg production means over a million eggs a day. But the catfish were the worst. More than a third of all U.S. farm-raised catfish were found contaminated with dioxins thanks to that ball clay. So, the FDA requested that ball clay not be used in animal feeds. They even asked nicely, writing, “Dear producer or user of clay products in animal feeds, continued exposure to elevated dioxin levels in animal feed increases the risk of adverse health effects in those consuming animal-derived food products… we are recommending that the use of ball clay in animal feeds be discontinued…We look forward to the industry’s cooperation.” (You can see the original letter in my video, Dioxins in U.S. Farm-Raised Catfish).

So, how cooperative did the industry end up being? Half a billion pounds of catfish continued to be churned out of U.S. fish farms every year, but only recently did the government go back and check. Published in 2013, samples of catfish were collected from all over the country. Dioxins were found in 96% of samples tested. Yeah, but just because catfish are bought in the U.S. doesn’t mean they came from the U.S. And indeed, some of the catfish were imported from China or Taiwan, but they were found to be ten times less contaminated. And indeed, when they checked the feed fed to U.S. catfish, more than half were contaminated, and so, it seems likely that mined clay products are still being used in U.S. catfish feeds. Even “just small amounts of mineral clays added to fish feeds, together with the fact that catfish can be bottom-feeders may lead to higher than acceptable dioxin residues in the final catfish products.”

The Institute of Medicine suggests strategies to reduce dioxin intake exposure, such as trimming the fat from meat, poultry, and fish, and avoiding the recycling of animal fat into gravy, but if almost all dioxin intake comes from animal fat, then eating a more plant-based diet could wipe out about 98% of exposure. Thus, “a vegetarian diet or even just eating more plants might have previously unsuspected health advantages along with the more commonly recognized cardiovascular benefits and decreased cancer risk.”

This is a good illustration of how we can’t necessarily rely on regulators to protect our families’ health. More on dietary dioxins and what we can do about them in Dioxins in the Food Supply and Counteracting the Effects of Dioxins Through Diet.

Even wild fish are exposed to industrial pollutants spewed into our waterways. See, for example:

Farmed fish is the worst, though: Farmed Fish vs. Wild-Caught.

Other pollutants in our food supply and how to avoid them:

Though the best way to detox is not to tox in the first place, our bodies can eventually get rid of much of the toxin load:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

17 responses to “Dioxins in U.S. Farm-Raised Catfish

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  1. Does cooking catfish remove any of the dioxins? Where can you buy catfish?

    By its nature catfish are bottom feeders where all the trash is. It seems that catfish are not good to consume right? Yet, I love catfish. What % of the dioxins are getting into my body and can the body get rid of them?

    1. Here are some links to federal EPA and FDA pages you might find helpful. On the EPA page there is a link to a “General Fact Sheet” which states that ‘the geographic area covered by testing for dioxins is small, in part because it’s expensive to test’. The federal Food and Drug Admin also has guidelines on safe eating limits. It’s easy to find these and other reports by independent environmental non-profits by googling safe eating limits fish. Number 4 is the FDA’s consumption info and 5 is some information for California fish consumption published by that state.

      1. https://www.epa.gov/choose-fish-and-shellfish-wisely/fish-and-shellfish-advisories-and-safe-eating-guidelines
      2. https://www.epa.gov/fish-tech
      3. https://www.epa.gov/fish-tech/national-listing-fish-advisories-general-fact-sheet-2011
      4. http://www.fda.gov/food/resourcesforyou/consumers/ucm110591.htm
      5. http://oehha.ca.gov/fish/nor_cal/2011SFbay.html

    2. Unfortunately cooking won’t remove dioxins. Also unfortunate is that dioxins have a half life of 7-11 years so it can take decades to clear them out of our bodies.

  2. I too love catfish, but it’s not worth the health dangers. The problem is most fish farm producers only care about profit, not human health. The only way producers will change their production methods will be to hit them in their wallets, stop buying their products.

  3. When I learned about dioxins a decade ago I was furious. “Animal studies indicate that dioxin is the most potent carcinogen ever discovered” my book stated. Yikes! And it’s concentrated in ALL animal fat and clearance from the body is a long slow process that can take decades. How many people are aware of this?

    1. Julie: Well said. It’s truly infuriating that society continues to poison the humans and non-humans of the planet even after knowing better. The common person may not know these details, but you can bet the farm that the people making the decisions do know.

  4. Interesting read. I’d be lying if I claimed to go plant-based for altruistic reasons, but they have definitely become more of a concern since adopting this lifestyle awhile ago. This write-up certainly gives credit to the phrase: “What goes around, comes around.”

  5. Being sick is normal. Taking medications is normal. Going to hospitals is normal. It is normal to die and have procedures. Disease is normal when you live in a society of sick people. Unhealthy people make rules for everybody to adopt their standards. I don’t think that a UFO could save us from disguised ignorance.

  6. A politically incorrect joke…”What’s the difference between a {… name or profession you abhor…} and a catfish? One is a bottom dwelling scum sucker, and the other is a fish”. :P

  7. Agent Orange contained a dioxin as an impurity. Some of the worst effects of Agent Orange on health is suspected to have been caused by the dioxin.

  8. Regulators are concerned more about the business continuing than public health. Otherwise, the regulating agencies would have the authority to shut down any operation found to be willfully destroying public health, after public, televised hearings…..When the 1% buys elections for their hand picked candidates who talk about industry approved issues, the result is a government of, by and for businesses against the consumers. Of course those who know what is contaminated and have the resources to get the best food will have no consequences from the poisoned food, air, water the rest of us are eating, breathing….

  9. how can we get an update on the current status of dioxins in catfish in today’s food supply? Is there any data out there? I wouldn’t necessarily assume that this data against catfish farms still holds true, a decade later

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