Why You Should Think Twice About Eating Swordfish
Mercury is both a naturally-occurring element as well as a byproduct of industrial projects which makes its way into water systems either via rain and snow or from runoff from industrial sites (via The United States Geological Survey).
It has severe health impacts on humans ranging from kidney problems to neurological effects. Too much mercury in the system can be fatal (via The World Health Organization).
One way that humans introduce mercury into their systems is by eating fish. Fish are exposed to mercury by living in mercury-contaminated waters (via Healthline), and because it stays in their systems, big fish which feed on smaller fish wind up with more mercury in their systems than fish that are lower in the food chain.
One such carnivorous fish is the swordfish, a popular menu item due to its meaty, steak-like texture (via the Spruce Eats). Because it's not flaky and delicate, swordfish is often called for in grill recipes that require a substantial hearty fish.
The mercury content in swordfish
Because they can grow up to 1,400 pounds and 15 feet, it's no wonder that they live at the top of the food chain and consume lots of smaller fish, which in turn have consumed small amounts of mercury (via Oceana).
Swordfish has about .995 parts per million of mercury, which seems to be a small number but puts it in second place on the Food and Drug Administration's list of seafood containing mercury. By comparison, pollock has .031 parts per million and Atlantic mackerel has .050 parts per million.
The good news is that it's not a death sentence to eat swordfish once in a blue moon. For the amount of mercury in swordfish to affect you in any meaningful way, you would have to be consuming a diet of primarily swordfish. At the same time, because mercury has more of an impact on developing fetuses than it does on adults, pregnant women are advised to avoid fish with high levels of mercury such as swordfish.