CouchHatter
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cobalt chloride desiccant dangerous?
Cobalt chloride is a coloring indicator used in some desiccants, changing from blue to pink when saturated. Some studies have been done as to its
toxicity and carcinogenicity in humans, but there are still unknowns. https://oem.bmj.com/content/58/10/619 . What I can't figure out is why this 3D printing blog would advise against using it. From what I gather the danger arises in factories where the beads are produced.
Could the absorption and release of moisture carry other molecules out of the beads? I have used cobalt chloride beads in my air compressor dryer and
re-used them after using a food dehydrator. Makes me wonder if these are something I should consider wearing a respirator around, or not drying food
with the machine after the beads. Maybe their blog should be taken with a grain of scientific salt, between the "We are no chemists" and some typos. I
can't see how it would pose ANY danger through normal use.
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Texium
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I wouldn't worry about it, so long as you aren't stirring up a lot of dust, and you clean the food dehydrator well before using it for food.
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zed
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If Cobalt Chloride is very dangerous, we all died a long time ago.
Might have some nasty secrets though. When you think about it, many of us have died.
Hmmmm.
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AJKOER
Radically Dubious
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In my opinion, cobalt compounds are probably toxic in a manner relating to the poorly understood toxic behavior of chromium salts!?
Both Co2+ and Co3+ can form numerous coordination compounds (or complexes), which implies to me that the standard reduction potential of say Co(ll)
can, I suspect, be varying based on the particular complex (see discussion at https://www.researchgate.net/post/Can_you_provide_an_explana... ). This produces the effect of 'excited states' which are associated with radical
formations. The latter can disrupt cell chemistry (like hydroxyl radicals acting on DNA).
Here is an example referring to the creation of hydrogen atom radical (cited as the major reducing species by Buxton in solution), which historically
has been referred to as the excited 'nascent' state of hydrogen:
H+ + e-(aq) = .H
.H + .H = H2
and some authors just ignore the transient excited state by writing:
H+ + e-(aq) = 1/2 H2
Now, in a nearly parallel reaction with metals:
M(lll) + e-(aq) = M(ll)
where the newly created M(ll) could actually be in an excited state which increases its toxicity! In the case of cobalt salts, the ability of forming
numerous coordination compounds, with, I suspect, varying standard electrode potentials, could contribute to this toxic excited state effect.
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A more specific sub-argument of the above is that as cobalt can apparently be easily complexed and move between lower and higher transition metal
states, this also implies that the well-known metal auto-oxidation reaction converting oxygen into the superoxide radical anion is facilitated:
M(ll)L + O2 ⇌ M(lll)L' + •O2- (L = ligands, which for Cobalt can be various with differing standard electrode potentials, see http://www.life.illinois.edu/crofts/bioph354/ligands.html)
H+ + •O2- --> HO2-
It has been claimed that water will readily provide a hydronium ion to convert the HO2- into hydrogen peroxide:
H2O + HO2- --> H2O2 + OH-
So, as the superoxide radical is a precursor to hydrogen peroxide, this implies that Fenton and Fenton-like reactions resulting in radical formations
are promoted (both in creating superoxide from oxygen and in reducing M(lll) back to M(ll) to create a cyclic reaction, problematic even in low
doses!). In fact my recollection of a review of advanced oxidation processes to address environmental pollution of non-iron metals (link to article ,
but now no longer free, https://www.researchgate.net/publication/262451840_Review_of... ) interestingly ranked cobalt and chromium as having exceptional abilities, but
we're generally ruled out do to their toxic nature.
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Some related material for reading:
‘Estimation of excited-state redox potentials by electron-transfer quenching. Application of electron-transfer theory to excited-state redox
processes’, by C. R. Bock, J. A. Connor, A. R. Gutierrez, Thomas J. Meyer, D. G. Whitten, B. P. Sullivan, and J. K. Nagle , in J. Am. Chem. Soc.,
1979, 101 (17), pp 4815–4824, DOI: 10.1021/ja00511a007
‘From free radicals to electronically excited species’, by Giuseppe Cilento and Waldemar Adam, in Free Radical Biology and Medicine, Volume 19,
Issue 1, July 1995, Pages 103-114, Link: https://www.sciencedirect.com/science/article/pii/0891584995... . From the abstract:
“The pronounced similarity in the chemical behavior and reactivity of radicals and excited species derives in part from the biradical nature of the
latter. Usually in analyzing the biological effects of xenobiotics, only radicals and/or reactive ground state products have been considered. However,
in such processes the generation of excited species is possible, which should be tested for by direct and/or sensitized emission or by photochemical
transformation.”
[Edited on 27-8-2018 by AJKOER]
[Edited on 27-8-2018 by AJKOER]
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unionised
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Cobalt is certainly toxic.
https://en.wikipedia.org/wiki/Cobalt_poisoning
The question is- as always- a matter of dose.
However, it's worth remembering that cobalt is also an vital part of the diet, albeit as this stuff
https://en.wikipedia.org/wiki/Vitamin_B12
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AJKOER
Radically Dubious
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Unionised:
Read my revised comments relating to promoting a possible cyclic Fenton-like reaction, which may account for Cr and Co favorable review in a relative
performance in an advanced oxidation study addressing the removal of pollutants (but, here, unfortunately DNA is a possible organic target of the
redox).
So, yes dose remains important, but I would not expect to see the typical slope (or first derivative in the case of a non-linear curve) for the
reduction in mortality versus lowering of the dose in the presence of a possible cyclic reaction. I would expect a more graduated/gentle decline.
One word translation: AVOID.
[Edited on 27-8-2018 by AJKOER]
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zed
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Back in the day, every child's chemistry set, was stocked with Cobalt Chloride.
We were not especially fastidious children. No doubt Cobalt Chloride is toxic, but probably not very toxic. Or, alternately.... we were ALL....
very, very lucky.
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AJKOER
Radically Dubious
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zed:
Perhaps only apparently lucky, as our body is constantly destroying cancerous cells. But, at some point, like when we get old, our body's natural
defense mechanisms get reduced, and all of a sudden, surprise (but that, in my opinion, is a lie), we get multiple cancers!
Recent example is a report about health issues from people exposed to the toxic soup from the WTC attack. The comment was in that exposed population,
they were seeing more early than normal serious health issues.
So not lucky, just delayed issues...
The good news is there are things we can do to boost the immune system to help fight free radicals, like Vitamin C, melatonin... Yes, the same
melatonin that disrupts fenton/fenton-type REDOX reactions and that is claimed to have anti-aging benefits probably by reducing free radical damage
(see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001211/ )! No real surprise here, at least for me, but we are all free to be ignorant about the
chemistry and wait for your surprise...
DISCLAIMER: I have no commercial interests in any vitamins or anti-aging product, nor do I make or endorse claims as to their efficacy or safety.
[Edited on 12-9-2018 by AJKOER]
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unionised
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Thanks for the warning.
I avoided reading it.
The toxicity of cobalt compounds is quite well documented.
https://echa.europa.eu/documents/10162/13641/cobalts_salts_s...
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AJKOER
Radically Dubious
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Quote: Originally posted by AJKOER  | ......
Read my revised comments relating to promoting a possible cyclic Fenton-like reaction, which may account for Cr and Co favorable review in a relative
performance in an advanced oxidation study addressing the removal of pollutants (but, here, unfortunately DNA is a possible organic target of the
redox).
So, yes dose remains important, but I would not expect to see the typical slope (or first derivative in the case of a non-linear curve) for the
reduction in mortality versus lowering of the dose in the presence of a possible cyclic reaction. I would expect a more graduated/gentle decline.
One word translation: AVOID.
[Edited on 27-8-2018 by AJKOER] |
Unionised: Thanks for that link on the toxicity report for select cobalt salts.
I especially find interesting the comment, to quote:
"Following the conclusion of the 2013 report, ECHA commissioned an assessment of the mode of action of the cobalt salts, which has concluded that the
cobalt salts are genotoxic carcinogens by inhalation with a non-threshold mode of action; RAC4 supported this conclusion. This work answered one of
the key uncertainties raised in the previous report. "
with the key word being 'non-threshold', which I am interpreting, per my extracted comments above, as relating to dosing level assessment.
[Edited on 13-9-2018 by AJKOER]
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