Selenium and Mercury

I just spent three days at an Inbre conference at Salish Kootenai
College in Arlee Montana. Inbre means "idea network for biological
infrastructure." The most important part about Inbre is that it pays
my salary. The second most important part is its support for educational
resources and information in rural states.

While there I learned a ton of good stuff, including some new
information about biological amplification of mercury in the food chain.

As you must know by now, mercury tends to get trapped in fatty tissues.
Most of the excess mercury in the ecosystem comes for coal fired power
plants. Mercury settles out into the food chain were it gets trapped in
fatty tissue, and then it amplifies as it migrates up the food chain.
Top of the line predators, like Pike, Barracuda, Sword Fish and Sharks
often have alarming and near toxic levels of mercury.

But mercury levels can be deceiving. Mercury causes trouble in
mammals by disturbing natural metabolic processes involving selenium.
Mercury binds chemically to selenium, transforming it into an alien
compound mammalian metabolisms cannot recongnize. And selenenium
(although toxic itself in excessive quantities) is an essential compound.

So it is not the mercury per se that causes mercury poisoning. It is
lack of selenium (caused by mercury's affinity to selenium) that causes
sickness.

PUNCHLINE POINT
There are many fish in the world that have high levels of mercury, that
are perfectly safe to eat, because they also have high selenium levels.
Most sea food is mercury safe. What counts is the ratio of selenium to
mercury. Sword Fish has bad ratio close to one to one. Shark tends to
be even worse. Fish with positive selenium to mercury ratios are safe
to eat. No matter how high the mercury, the fish is safe, as long as
it also contains enough selenium.

Fresh water fish, unfortunately, tend to have bad ratios. Some areas
are worse than others. The Rocky Mountains are particularly bad.
Mercury concentrates in all fresh water predators, and in the Rock
Mountains, mercury levels (although not particularly high) are
dangerous, because the selenium levels are so low.

The ratio, and not the absolute level, is what counts.
And big Brown Trout are a bad deal. Mercury poisoning effects the
nervous system. In tends to make you dumb. Maybe that's why rural
western voting patterns are....well. I'd better not go there. :-)