Saturday, 18 January 2014

Chromium Six

Dang but teaching can be fun!  My first class back after the holiday last Monday, I gave my (N=9) environmental chemists a task to investigate the 10 chemical elements that qualify as trace-elements in human nutrition.  10 - 9 = 1, so I bellied up to the bar and said I'd do the report on whatever element nobody wanted to touch.  That short straw was going to be Selenium but at the last minute one of the students took that and left me Chromium instead.  Well Cr turned out to be rather interesting because it has been central to two unrelated controversies, one medical and the other environmental.  Unrelated everywhere except in The Blob - because my task to the EnvCh class was to ask (form a hypothesis we say) if there was a correlation between the abundance of elements in the Earth's crust  and in the human body..

Chromium is the fourth of the transition elements, atomic number 24, between Vanadium (23) and Manganese (25).  Chromium exists in a wide range of oxidation states but predominantly as Chr(III) and Cr(VI).  Cr(VI) salts are highly reactive and powerful oxidants,and so toxic that they are used as wood preservatives.  Since 1890, Cr(VI) salts have been known to be toxic and carcinogenic if inhaled and may induce a contact dermatitis as well when wet.  These 'hexavalent' chromium compounds were the star players in the film Erin Brockovich in which Brockovich sued the local power company  in Hinkley, CA for allowing Cr(VI) compounds to leach into and contaminate the groundwater.  The citizens of Hinkley finally settled for $333million, about $200,000 each, of which the lawyers got 40%.  If you read the Daily Mail or listen to Loma Linda University's Professor John Morgan, epidemiological studies indicate that consequent cancer rates in Hinkley were not significantly elevated.  If you believe The Centre for Public Integrity, you'll reckon that Morgan massaged his data to show that there was nothing shocking under the sand.  Now I'm sorry for you if you want The Blob to give you the skinny on what the truth is out there under the beautiful Mojave Desert.  Science is hard and you're going to have to reconcile a lot of different assertions and data to decide for yourself. You might think for example the The California Cancer Registry and their report on Hinkley (by Morgan!) is an authoritative source.  But I used to live in the "Carnivore Genetics Research Centre", which was the desk and file-cabinets in the otherwise uninhabited cellar of my gaffer's home in the Boston surburbs.

With all this chromate toxicity,  it’s a little curious that Cr(III) is considered by some to be an essential dietary supplement, although only in minute quantities.  These findings are controversial, 3 cases have been identified where patients fed through an intravenous drip on an artificially reduced diet for a long time got sick but recovered when chromium was supplemented.  This suggests that a) vanishing small quantities are sufficient for whatever its purpose (possibly glucose metabolism or as a cofactor for insulin) is and b) it is easy to obtain enough in any normal diet.  Because Cr is sequestered in different parts of the body in different chemical states it is quite difficult to measure its concentration overall as a baseline to establish if someone is deficient. The US Academy of Science has a tentative RDA of 50 μg/day but also finds that most Americans intake much less that this (and live happy and productive lives).  The American Diabetes Association conclude thatat the present, benefit from chromium supplementation in persons with diabetes has not been conclusively demonstrated”. This tentative benefit and the known toxicity of excess Cr has not stopped a market developing in chromium dietary supplements.  The Blob's advice: save your money for Molybdenum supps we definitely need a little of that.

Sorry if you thought this was going to be a review of the prequel to The Secaucus Seven. You're just showing your age Eightiesperson.

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