It's not just tuna. Mercury in fish is becoming a bigger and bigger problem worldwide.

In Roman mythology, the god Mercury represented financial gain and good luck. Today, the idea of mercury isn't so pleasant, and it's definitely not something you want on your plate. Linked to brain damage and cancer, the heavy metal is highly toxic and is building up in some of America's favorite seafood dishes as ocean pollution reaches unprecedented levels. In fact, a recent United Nations Environment Program report found mercury levels in our oceans doubled over the last century.

To help reverse this unappetizing problem, delegates from 130 nations around the world are meeting to develop a first-ever mercury-curbing agreement.

Man-made mercury pollution comes from burning coal, where it starts as air pollution and returns back to surface waters when it rains, building up in certain fish. You probably already know tuna poses a mercury threat, but you can also avoid the toxic substance by minimizing meals that feature these fish:

Orange Roughy
It's a lose-lose when you put orange roughy on your plate. One of the most mercury-packed fish on the market, it's also overfished to the point of threatening the species' survival.

Lobster
Lobster contains moderate amounts of mercury, meaning you want to limit lobster meals to fewer than six a month. If the heavy metals aren't enough to deter you, consider this: Scientists in New England found that many lobsters were contaminated with the pesticides used to kill mosquitoes.

Red Snapper
A recent Oceana report found that 15 out of 19 times, fish served as red snapper wasn't really red snapper, but in some instances was tilefish, a mercury-rich fish that children pregnant and women are advised to avoid.

To find safer seafood picks, check out The 10 Healthiest Fish on the Planet.