Salmon contains very low levels of heavy metals, making it one of the safest fish you can eat. Fresh or frozen salmon averages just 0.022 parts per million (ppm) of mercury, and canned salmon is even lower at 0.014 ppm. For context, high-mercury fish like swordfish and shark can reach 1.0 ppm or more. The FDA lists salmon as a “Best Choice” fish, its highest safety category.
Mercury Levels in Salmon
Mercury is the heavy metal most people worry about in seafood, and salmon consistently ranks near the bottom of the scale. At 0.022 ppm for fresh or frozen fillets, salmon contains roughly 20 to 50 times less mercury than predatory fish like king mackerel, tilefish, or bigeye tuna. Canned salmon comes in even lower at 0.014 ppm.
The reason salmon stays so low comes down to its position in the food chain. Mercury builds up through a process called biomagnification: tiny organisms absorb it from the water, small fish eat those organisms, and bigger fish eat the small fish. At each step, mercury concentrations increase. Large, long-lived predators at the top of the chain accumulate the most. Salmon are mid-level predators with relatively short lifespans, so they simply don’t have as much time or dietary exposure to build up significant mercury stores.
Salmon also has a built-in advantage. It contains high levels of selenium, a mineral that counteracts some of mercury’s harmful effects. Selenium binds to mercury in the body and helps prevent it from disrupting important cellular processes. Salmon’s selenium-to-mercury ratio averages around 29:1, meaning there’s far more protective selenium than harmful mercury in every bite.
Other Heavy Metals: Lead, Cadmium, and Arsenic
Mercury gets the most attention, but it’s not the only metal found in fish. Lead and cadmium levels in salmon are consistently negligible. A Norwegian study measuring contaminants in Atlantic salmon found lead and cadmium at 0.01 mg/kg in both farmed and wild fish, essentially at the lowest detectable limit.
Arsenic is present at somewhat higher levels, particularly in wild salmon, which averaged 2.56 mg/kg compared to 0.86 mg/kg in farmed salmon. However, the arsenic found in seafood is predominantly organic arsenic, a form the body processes and eliminates much more efficiently than the inorganic arsenic found in contaminated water or rice. Independent testing by ConsumerLab found no problems with canned pink or sockeye salmon for any heavy metals.
Wild vs. Farmed Salmon
This one surprises most people: wild salmon actually contains more mercury and arsenic than farmed salmon. Norwegian research found wild Atlantic salmon averaged 56.6 micrograms of mercury per kilogram of fillet, while farmed salmon averaged just 18.1 micrograms per kilogram. That’s roughly three times less mercury in the farmed fish. Arsenic showed a similar pattern, with wild salmon containing about three times more than farmed.
The explanation is straightforward. Farmed salmon eat a controlled diet that increasingly includes plant-based ingredients, which naturally contain less mercury than the wild prey that free-swimming salmon hunt. Wild salmon feed on smaller fish, shrimp, and krill that have accumulated metals from the ocean environment over their lifetimes. Lead and cadmium, however, were equally low in both groups.
It’s worth noting that while farmed salmon is lower in heavy metals, wild salmon tends to be higher in certain beneficial nutrients like DHA, one of the key omega-3 fatty acids. Both types are well within safe limits for metals, so the choice between them doesn’t need to hinge on contamination concerns.
How Much Salmon Is Safe to Eat
Because salmon falls in the FDA’s “Best Choice” category, the recommended intake is generous. Adults can eat two to three servings per week (8 to 12 ounces total) without concern. This applies to people who are pregnant or breastfeeding as well, though they should eat a variety of low-mercury seafood rather than the same fish every time.
For children, the FDA recommends two servings per week, with serving sizes scaled by age: about 1 ounce for toddlers ages 1 to 3, 2 ounces for ages 4 to 7, 3 ounces for ages 8 to 10, and 4 ounces at age 11. Salmon is specifically named as one of the lowest-mercury options suitable for children at these higher serving frequencies.
Canned vs. Fresh Salmon
Canned salmon actually tests slightly lower in mercury than fresh or frozen (0.014 ppm vs. 0.022 ppm). Most canned salmon is wild-caught pink or sockeye from Pacific waters and is processed relatively young and small, which contributes to its low metal content.
One consideration unique to canned products is the can itself. Tin can leach from the lining into the food, particularly from older-style unlacquered cans, which can contain up to 100 ppm of tin. Modern cans with protective coatings minimize this, and tin at low levels isn’t considered a significant health risk. If you’re choosing between canned and fresh for heavy metal reasons alone, both are safe options, and canned salmon has a slight edge on mercury.
How Salmon Compares to Other Fish
To put salmon’s numbers in perspective, here’s how its average mercury level (0.022 ppm) stacks up against commonly eaten seafood:
- Shrimp: 0.009 ppm
- Salmon (fresh/frozen): 0.022 ppm
- Pollock: 0.031 ppm
- Light tuna (canned): 0.126 ppm
- Albacore tuna: 0.350 ppm
- Swordfish: 0.995 ppm
Salmon sits near the very bottom of this range. You would need to eat roughly 45 servings of fresh salmon to match the mercury in a single serving of swordfish. For most people, the omega-3 fatty acids, protein, and other nutrients in salmon far outweigh any trace metal exposure.