How to Lower Your Risk From the Chemicals in Seafood

If a chemical goes into the water and doesn’t break down, it can end up in fish. Common contaminants like PFAS are linked to certain cancers, hormone disruption, liver disease, and developmental toxicity for children and fetuses, among other issues. 

Meanwhile, fish farms use a constellation of toxic hormones, antibiotics, and pesticides. For example, some use formaldehyde, a carcinogenic embalming fluid, as a pesticide or preservative. Another common U.S. farming chemical found in salmon fillets is ethoxyquin, which is linked to DNA damage, among other conditions, and is banned in the European Union. Some farmed fish have been found to contain higher levels of pollutants than wild. The contaminants in their feed have been found in an animal study to cause metabolic disease, and antibiotics used in fish farming are linked to the proliferation of “superbugs.” 

Moreover, the conditions at industrial farms can be downright unsanitary, as has been found at some farms in countries with fewer antibiotic, pesticide, and management regulations. In the worst of them, as many as 150 shrimp are packed into a square meter, which can lead to bacteria—and algae-breeding sludge of fecal matter, chemicals, and excess food. For all of these reasons, I avoid farmed fish as much as possible. 

Keep in mind that eating a few farm-raised shrimp, for example, probably won’t kill you. But all the chemicals we’re potentially exposed to in daily life can add up—PFAS in cookware, lead in water, flame retardants in plastic, pesticides on produce, and all the substances outside the kitchen. Taking simple steps to avoid the chemicals can help reduce the risk. 

I have a confession to make: I’m pretty consistent about taking steps to avoid chemicals in food and my kitchen, but I most often break my rules when it comes to seafood. I love it, and sometimes I gotta have that Great Lakes whitefish paté, even knowing what’s in it. And of all the topics we’re covering, it’s most difficult to avoid chemicals in seafood because there’s so much uncertainty. All of this is to say, you want to be cautious and do what you can, but don’t drive yourself crazy in the process. 

Seafood is a challenge in part because, unlike fruits and vegetables, there’s no legal definition for organic seafood. A fillet’s chemical load depends on variables that can’t be easily accounted for, like where the fish lived.

To reduce risk, buy wild-caught from the ocean when it’s less expensive and available (oysters and mussels are exceptions—I’ll explain more below). While wild-caught fish isn’t a silver bullet because some netting practices can round up seafood not intended to be collected, unlike fish grown in farms, it’s not raised in waters with intentionally added chemicals. If you’re buying farmed, try to get products from U.S. farms, which are generally more tightly regulated. It’s also worth noting that “sustainably farmed” has no legal definition and doesn’t exclude chemicals. 

But there’s an exception to my recommendation about eating wild-caught fish. In the U.S., freshwater fish is especially a problem because the waterways are typically more polluted. Federal testing, on average, found far more PFAS in freshwater fish than ocean-caught and higher mercury levels. PFAS in one serving of some common freshwater fish was found in one study to be equivalent to drinking highly contaminated water every day for a month.

Oysters
Oysters sponge chemicals, so I check where they’ve been raised. If they were near a military base, the Chesapeake, the lower Puget, or urban centers, then I won’t touch them. It requires a little effort, but you can do this by checking Google Maps for the oyster farm’s location in relation to nearby military bases and urban centers. 

Shrimp
While I occasionally break some of my own rules, I always avoid shrimp farmed outside the U.S. If it’s in the budget, buy wild-caught, and ideally, those with trustworthy certification. If it’s not in the budget, buy shrimp farmed in the U.S. 

Tuna
CR’s tests of mercury in canned tuna found much lower levels in skipjack and light tuna than in albacore. As CR said, “None of the albacore tunas in our tests had levels low enough for an adult to have three servings a week.” That same logic may hold for PFAS in tuna, though very little testing for it exists.  Pole & Line, which is certified by the Marine Stewardship Council and available in Whole Foods, is among my preferred brands. CR advises avoiding tuna altogether if you’re pregnant. 

Seafood from the Great Lakes, Chesapeake Bay, and Puget Sound
I live in Detroit, so it pains me to skip Great Lakes fish, but the lakes sit in the nation’s industrial heartland. Compared with other freshwater fish in the U.S., they show some of the highest levels of PFAS, PCBs, dioxin, mercury, DDT, and a range of other pollutants. And while there are few things as glorious as digging into a platter of Maryland blue crabs, I typically don’t eat seafood from mostly enclosed bodies of water, even those as big as the Chesapeake Bay and Puget Sound. They’re polluted by urban centers and military bases around their shores or industry along rivers emptying into them. Seafood from each has been found to contain staggering levels of PFAS, PCBs, and other toxins. 

I wish I had better advice, and I’m open to suggestions. But what I tell my friends, readers, and colleagues is to limit the consumption of seafood from these waters.

As a general rule, smaller fish are usually safer because fish accumulate toxins farther up the food chain as the bigger fish eat the smaller ones.  

Consumer Reports has a helpful guide for navigating the meaning behind popular seafood terms, such as “pole-caught” and breaks down the most reliable seafood certifiers, like the Marine Stewardship Council, which aims to signify fisheries that meet certain sustainability practices (look for its logos on the packaging). Other groups offer useful tools for parsing the various seafood species and farming practices.

• Give a few minutes of thought to what kind of seafood you like. Is there anything that’s a risk that you’re willing to eat less of? For example, albacore tuna has been found to have higher levels of mercury. Could you cut back on it? Or eat skipjack instead? 

• Check seafood packaging to make sure the product is wild-caught, or ask your fishmonger to clarify. 

• Take a quick peek at CR’s very helpful certification guide and breakdown of seafood terms. Keep an eye out for these on your next trip to the grocery store.