The mercury-in-fish dietary guidelines issued by the Food and Drug Administration are only for pregnant women, women who are planning to become pregnant, and young children. And even then, the FDA's guidelines are overly cautious. The FDA has issued no consumption advice about the amount of fish that's safe for older kids, teens, men, post-menopausal women, and women who don't plan to become pregnant.

In the FDA's own words, its mercury guideline "was established to limit consumers' methyl mercury exposure to levels 10 times lower than the lowest levels associated with adverse effects." So even if a pregnant woman consumed twice as much mercury as the FDA's recommended limit, she would still be protected by a 500-percent cushion.

This calculator uses the Environmental Protection Agency's "Benchmark Dose Lower Limit" (BMDL) to demonstrate the actual dose of mercury in tuna and other fish that's completely safe for consumption. Fishy calculators run by the Environmental Working Group and other scaremongering organizations use the EPA's "Reference Dose" instead -- which is this BMDL divided by ten. So the amount of mercury that might be harmful is actually ten times greater than the amount the U.S. government (and a growing activist chorus) wants you to consider "unsafe."

The Food and Drug Administration's advice to young children and women of childbearing age is roughly equivalent to the EPA's Reference Dose, which is by far the most restrictive in the world. The standards adopted by the Canadian government, the World Health Organization, and the British Food Standards Agency are 4.7 times higher than what the EPA permits.