How dangerous can eating fish be

I was looking at the warning in the REGs about eating fish because of the mercury content.
Is this something new or have the fish always had it?
Is this something caused by man or nature?
Do all the fish have it?
Is it in all waters?
Where would I look for the answers?
Curious Bill

I've done a ton of research on mercury for an article I wrote and some subsequent flame wars with the "sky is falling" crowd. You can do some of the same research and get most of your questions answered quickly...however, I can give you the short version:

Organic mercury (the only kind you'll ingest from fish) is both man-caused and natural. It's been around probably forever as a result of a microorganism that converts metallic mercury into organic mercury.It's in the air, water (primarily) and just about every living thing, if not all living things. Currently, over half the organic mercury created each year comes from natural sources. The bulk of the remainder comes from Asia, China and India specifically.

In North America, it seems to be declining based on samples taken from animals killed in the 1800s and preserved.

While all fish likely have some mercury in them, older and larger fish are likely to have more than younger/smaller fish. So if you're concerned, eat younger/smaller fish.

Certain predator fish contain more mercury than others...such as some tunas, sharks and the like.

There's a lot of contradictory discussion on the health aspects of eating fish with high mercury content. However, my research turned up only two situations where ingesting mercury caused serious health problems. In the first, hungry villagers in Iran or Iraq ate seed wheat that had been treated with mercury fungicide. In the other, Japanese people who ate fish from a bay that was an industrial dumping ground were affected, as were their children.

There also is evidence to support that eating fish with a high-ish mercury content does no measurable harm. The Seychelle Islanders eat a lot of the tuna/shark/swordfish species that are high in mercury without any ill effects. There have been several other studies with similar results.

Also, some testing has shown hand-eye coordination improvement in older people who have a diet high in mercury...don't know how high is high in this case, though. The Lancet (the British equivalent of the AMA Journal) just published an article that downplayed the risks of eating fish for pregnant women. The article stated that there were improvements in the mental abilities of the babies they carried when fish were eaten...which may or may not be a direct link to mercury...I just read the article about the study and not the study itself.

You can find more information (way more information) in a Google search, but you have to skim through a lot of misinformation to find it. The sources I used were the American Medical Association, the British version of the AMA, and the federal Center for Disease Control. The CDC has some fairly intensive studies.

Very informative post, Keith.

Bill W

This forum and the people that use it have brought my I Q up to double digits. I know enough now to be dangerous.
I am going to go get a mess of walleye and have a fish fry real soon.
I will have to test the eye-hand coordination . Anyone have something in mind for me to try before and after my walleye meal.
Bill
All of ya'll are the greatest! Thank you Keith

You're welcome, Bill. And thanks for the kind words both of you...

I hate to see someone miss out on fishing or miss out on eating fish because they read something that was biased and a bit scary.

Keith

It's a bit late, but i have never actually seen a report where they say if you eat "x amount" of mercury then you will die from "x disease". I think the mercury scare is a little overrated, considering many foreign people eat a mainly fish diet and they can live healthy lives. Also, If mercury scares people away from fishing, then Carbon monoxide should scare them away from driving, or i could go on with the endless list of things that are bad for people, but they do it anyway, so i think you get the point. FISHIN IS GOOD! Dont be scared now, catch that fish, and eat it.

I've studied the mercury thing a little and other nutrition/toxicity issues a little more. One problem with mercury toxicity research is that mercury occurs much more in fish than most other food sources, but fish themselves 1) contain many contaminents....not just mercury and 2) fish contain many nutrients, such as omega 3 fatty acids, that are very healthy for you. Thus, its hard to tell what causes what and what prevents what. The omegta 3's, in fact, are thought to be potentially protective of nervous tissue that would be damaged by mercury. So eating fish can help protect your nervous system or hurt it, depending on how you look at the research. One thing is for sure: The western diet is currently far lower in omega 3's than its been historically. Omega 3 deficiency has been linked with many diseases that plague our country, including coronary heart disease, diabetes and multiple sclerosis, among others.

Old amalgam fillings may pose more mercury danger than eating fish, depending on who you talk to. Mercury was banned in American densistry before the ADA came along because of neuro toxicity. I believe it is currently banned in some European counrties. When fillings start to break down, or when a tooth cracks, mercury can enter the bloodstream. I didn't know, until recently, that the amalgam fillings I got as an adolesant have limited life (~10 to 20 years) and should be replaced periodically.