Roughly 3 in 10 people overall say they have changed their seafood-eating habits for safety or nutritional reasons. So here’s what you need to know about contaminants like mercury and bacteria in seafood.

The Mercury Problem: Mercury, a neurotoxin, is the most well-known health threat from eating fish. Too much of the heavy metal can harm anyone, impairing speech and hearing and causing muscle weakness. But it’s a particular concern for pregnant women, babies and children, because developing brains and bodies are especially vulnerable.

Most seafood contains some mercury from either natural sources or industrial pollution. But bigger fish-such as tuna, shark, and swordfish that are higher in the food chain tend to have more of the heavy metal because they take in all the that the smaller fish mercury eat. Mercury in tuna is especially worrisome because it’s popular with both adults and kids.

So recently independent tests were performed for mercury in five popular canned tuna brands: Bumble Bee, Chicken of the Sea, Safe Catch, StarKist, and Wild Planet. They disclosed that the mercury levels in tuna samples varied widely but that albacore contained, on average, three times as much as the light or skipjack variety. That makes sense because albacore tuna are larger fish.

Conclusion: The tests disclosed that average mercury levels across the samples were, with a few exceptions, generally low enough that adults could safely eat up to three 5-ounce cans of light or skipjack tuna a week, or one can of albacore. However, individual cans of tuna contained enough unpredictable spikes in mercury that canned tuna should avoided entirely during pregnancy. Children can still eat light or skipjack tuna, though in smaller amounts than adults, following these weekly, age-specific guidelines: AGES 1 TO 3: 2 ounces

AGES 4 TO 7: 4 ounces

AGES 8 TO 10: 6 ounces

AGE 11: 8 ounces

For guidance on mercury in other fish, and how much you can safely eat, most adults can eat up to three servings a week of fish with lower levels of mercury such as flounder, sea bass, haddock, lobster, salmon, shrimp and others. Regarding medium levels of mercury, one weekly serving should be OK for that contained in bluefish, carp, grouper, halibut, mahi mahi, Spanish mackerel, snapper, albacore tuna, and others. Everyone should avoid those fish with higher mercury levels such as King mackerel, marlin, orange roughy, shark, swordfish, tilefish, and tuna (bigeye)

Other Contaminants: Mercury isn’t the only pollutant of concern to seafood lovers. Research suggests that potentially dangerous pesticides and other chemicals contaminate our water and, in turn, the fish we eat.

The effects of these chemicals on human health aren’t as well- understood as mercury but have been linked to a host of health problems ranging from a suppressed immune system to an increased risk of liver and some other cancers.

Mercury accumulates more in bigger, slower-growing fish. But per- and polyfluoroalkyl substances, known as PFAS, can linger in the environment for many, many years, and they do not follow the same pattern. Here, it’s more about where a fish was caught-its proximity to sites of PFAS contamination-than it is about its size or species.

Researchers are increasingly finding PFAS in many places, including near manufacturing plants that make the chemicals, which are used in hundreds of products ranging from nonstick cookware to rainproof clothing to food packaging.

The Food and Drug Administration last year found extremely high PFAS levels in two samples of canned clams from China, leading to a recall of the products, although its tests of other ocean dwelling seafood, such as cod and tuna, have not revealed worrisome levels of PFAS

The bigger concern appears to be with freshwater fish caught by recreational anglers and indigenous people who incorporate local fish into their diets. A study by the Environmental Working Group suggests that PFAS may be highest in catfish, small- and largemouth bass, yellow perch, and walleye, especially when caught near urban areas and in the Great Lakes.

When it comes to pesticides like DDT and industrial compounds such as polychlorinated biphenyls (PCB), the risk of contamination is a combination of both a fish’s size and its proximity to pollutants, it is best to limit exposure to pesticides and most other potentially harmful chemicals, a safe bet is to follow the same guidelines as for tuna because fish high in mercury could be high in other contaminants. PFAS is mostly a concern if you are a freshwater angler. If you are, contact your state’s department of natural resources for any guidance, and ask about known PFAS contamination sites in your area.

Raw and Risky?

From sushi and ceviche to oysters and clams on the half shell, raw seafood is a staple in many cuisines. In a new survey, about half of people who eat seafood say they choose raw at least occasionally. The concern: Cooking seafood to 145 degrees F kills most germs that could be in the food, but when the food is eaten raw, dangerous pathogens can be present and cause illness. For fin fish, the issue is mostly parasites such as roundworms, tapeworms, and intestinal flukes. Depending on the type, these parasites can work their way into the intestinal wall and cause nausea, diarrhea, or abdominal pain. Some can even migrate to your liver or heart and damage those organs. For oysters, clams, mussels, and other shellfish, bacteria are the most common cause of food poisoning. particularly one called vibrio. It thrives in coastal waters, especially in warmer months, and it can cause diarrhea, vomiting, and fever. Infections from it sometimes require hospitalization and can even rarely be fatal.

The best strategy: Anyone who is pregnant, is younger than 5 or older than 65, or has a weakened immune system should simply avoid raw seafood. according to the Centers for Disease Control and Prevention. Others can reduce, but not eliminate, the risk when preparing raw fish at home by carefully selecting seafood and making sure it’s prepared properly.

For most raw fin fish, that usually means buying commercially frozen fish. That’s because the parasites that can be found in raw fish can be killed only in temperatures below 0″ F, When you are ready to prepare the fish, thaw it slowly and, once defrosted, keep it very cold. And don’t use the fish if it looks slimy or smells very fishy.

For raw shellfish, check for freshness. Bagged shellfish should have a tag indicating when it was harvested, and if shellfish isn’t bagged, the store should have that information. Stick with those harvested no more than about a week earlier. Also do your own inspection: Shells should close tightly when tapped, and don’t buy them if they are cracked. Use any shellfish you bring home within one or two days, and when the shells are opened, the meat should be firm.

When dining out, consider the restaurant’s reputation. Ratings and reviews on Google, Yelp, and similar sites aren’t foolproof. But it would be wise to avoid places that have anything other than stellar reviews or that have even a few mentions of food poisoning. Some locations provide letter grades or color-coded placards to indicate recent food inspection results. Especially when it comes to sushi, choose only restaurant’s with top ratings.


Despite the warnings detailed above, seafood-eating is generally conducive to better health, especially when compared with consumption of red meat. Some people are concerned about possible risks in consuming farmed fish versus those that are wild caught. In general, farmed fish are safe and nutritious, and I have covered this in a prior communication:



5 thoughts on “HOW SAFE IS SEAFOOD?”

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top