"Hax Planx" wrote in message
.net...

I don't know of any maximum contaminant level (MCL) regulation that is
unreasonable. If a water source has an MCL violation, you can rest
assured that the concentrations of that contaminant are very high
compared to what is normally encountered with clean water.
Concentrations of cobalt are typically in the microgram/liter (ppb)
range for clean drinking water, so an MCL regulation would probably be
nearer the mg/L (ppm) range considering its low toxicity by ingestion,
if such a regulation were ever instituted. It would all depend on what
conclusions were on the study that prompted the hypothetical regulation.
But what I've been able to dredge up from the Net is that continued
ingestion of more than 30mg per day is required to see negative health
problems.

The EPA tends to overreact to preliminary studies. For example, the
recent lowering of exposure limits to methylene chloride is just one
example. At least there is some hope that the EPA will actually reevaluate
that one.


A useless media coined term. Gold is heavier in atomic weight and
denser compared to arsenic, yet it is non-toxic and inert. There are
many other examples. I don't see how manganese at 25 on the periodic
table and cobalt at 27 could be considered heavy metals, whatever that
means. Of course, Andy Dingley didn't mention that term in his post,
but others have in previous threads.


The term "heavy metal" has been in use way before the "media" could have
coined the term. It can be found in all sorts of analytical chemistry
textbooks that date back to before the 1940s and was used in the open
literature before that time. Way back, it actually did have something to
do the with density of a metal but it quickly became applied to all sorts of
metals. It definitely has nothing to do with a metal's atomic weight.
By the way, gold can be quite toxic when in something other than its
elemental form. Just ask anyone who has to take gold containing arthritis
treatment drugs. Keep in mind it is not so much the elemental lead that is
so toxic, it is what it rapidly turns into in the human body. There will
always be certain metals that are way more toxic than others because they
severly
interfere with the human body's biochemical mechanisms.


Yes, but in my worst case scenario I wanted to assume that part of the
finish is actually ingested. Yet even in this worst case scenario
exposure levels were in the microgram range. I think we can forget
about manganese entirely since both of the multi-vitamins in my house
have 2mg of manganese per tablet, a couple of orders magnitude greater
than my worst case scenario. Also the driers are used only in
polymerizing finishes and even if small chips of the finish were
consumed, it isn't at all clear to me that those polymers are digestible
or that the driers could be leached from them. So not only are the
driers safe for ingestion, the exposure amounts are at worst small, but
quite possibly negligible.

I agree 100%. The amounts are so small as to be insignificant when
compared to accepted limits.