[ RadSafe ] heavy metal hormesis / trace levels etc

[Bjorn Cedervall]

I find the comparison with chemicals quite irrelevant. Each element has to 
be discussued separately. All elements can kill you if they are given in 
high enough amounts. The essential (trace metals) include most elements of 
the periodic table (actinides and transuraniums taken aside) - only about 
four exceptions are known. There is thus a "concentration window" (for some 
or most organs) that is good for you. Chromium is needed in small amounts in 
the pancreas, copper in the liver, (vertebrates)... there is a long story 
here.

The term "hormesis" is according to my opinion not well defined and 
therefore not very useful - it refers to dozens, if not hundreds of 
phenomena that shouldn't be clumped together.

"Tolerance" to metals in vascular plants for instance can be broken down 
into capacity to exclude (a threshold is then often reached where the toxic 
effects take over) and the capacity to take up (examples: Haumanistrum sp. 
(cobalt) and Bechium homblei (copper), both African members of the genus 
Lamiaceae).

My personal opinion only,

Bjorn Cedervall   bcradsafers at hotmail.com