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...I would not recommend trying that. Sorry for the fat finger, Robbie Sent from my Windows 10 phone From: Robbie Joosten<mailto:[log in to unmask]> Sent: 12 September 2017 21:46 To: [log in to unmask]<mailto:[log in to unmask]> Subject: Re: [ccp4bb] Risk assessment for heavy atom soaking - examples? Liquid mercury cannot be absorbed very well through the skin. Also ingestion seems to be much less risky than breathing in mercury vapours. My thermodynamics lecturer at uni was convinced that you can drink liquid mercury with no health risk, but I would not rec Sent from my Windows 10 phone From: George Sheldrick<mailto:[log in to unmask]> Sent: 12 September 2017 20:59 To: [log in to unmask]<mailto:[log in to unmask]> Subject: Re: [ccp4bb] Risk assessment for heavy atom soaking - examples? Over 50 years ago, a Toepler pump that I had glass-blown myself developed a crack that caused several kilos of mercury to hit tha ceiling and give me a shower. Fortunately I did not then know how poisonous it was and suffered no ill-effects George On 12.09.2017 19:46, James Holton wrote: > One more correction, > > It seems brominated vegetable oil (BMO) really does contain Br atoms! > I could have sworn I read in some reputable source long ago that the > process of "bromination" was an old term for general reduction of > double bonds and did not necessarily involve bromine. Usually > hydrogen. I remembered this because I thought it was hugely > counter-intuitive. Now, of course, I cannot find that reference. So, > who am I to pit the validity of my memory against Wikipedia and a long > list of links to health-nut web blogs? Guess I was wrong about that. > > The Mountain Dew I am drinking right now has a very faint X-ray > fluorescence peak that could be Br. Hard to be sure above > background. So I will have to get a sample of neat BMO to sit next to > my shampoo, pepto and sunscreen on my shelf of heavy atom compounds > that are on the FDA's GRAS list: > https://www.fda.gov/food/ingredientspackaginglabeling/gras/ > > Remarkably, the MSDS for BMO is less scary than that of ordinary > vegetable oil. This raises more than one interesting topic, but the > most relevant here I think is "bio-availability". Selenomethionine is > much much more bioavailable than selenium sulfide, which is the active > ingredient in my dandruff shampoo. Apparently, humans don't absorb it, > but microorganisms can mistake it for a source of sulfur. > > I expect the bio-availability of Hg in pizza is pretty high > considering how it bio-amplifies in fish, so I stand by my APE. But it > is always prudent to read the MSDS before you open a bottle, and then > read the MSDS of something similar just to put it in perspective. > > -James Holton > MAD Scientist > > On 9/6/2017 12:59 PM, James Holton wrote: >> Was just pointed out to me off-list that my anchovy data was off, so >> I just double-checked the FDA website: >> >> https://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm115644.htm >> >> >> Turns out the latest number for anchovies is 0.016 ppm, or 0.5 ug per >> ounce (28g). >> >> So, if you use a whole 2 oz can, that's still ~ 1 microgram Hg as the >> Anchovie Pizza Equivalent. >> >> And it looks like one piece of bigeye tuna sushi could be as much as >> ~14g*1.816ppm = 25 APEs >> >> -James Holton >> MAD Scientist >> >> On 9/6/2017 11:44 AM, James Holton wrote: >>> Something that could perhaps be of use here is what I like to call >>> the "Anchovie Pizza Equivalent" (APE), which is about 1 microgram of >>> mercury. According to the Food and Drug Administration website here >>> in the USA the average mercury content of anchovies is 0.34 ppm, >>> which is about 1 microgram per ounce of fish. Tuna can be higher, >>> but varies a lot from fish to fish. My point here is that most >>> institutions regard the amount of mercury you bring onsite for >>> purposes of eating for lunch, be it sushi or pizza, as small enough >>> to be negligible. I tend to agree. So, one could argue that 1 >>> microgram of Hg per day is a "safe amount". Especially if you don't >>> eat it. >>> >>> In terms of protein crystals, a 100 micron wide cube has a volume of >>> 1 nanoliter, and if it were soaked to a final concentration of 50 mM >>> Hg that is 1e-9 L * 50e-3 mol/L *200 g/mol = 10 ng. So, 100 protein >>> crystals soaked with Hg add up to roughly 1 APE. Please note that I >>> am in no way encouraging you to eat your protein crystals, and >>> especially not the solutions you soak them in. You should do your >>> own APE calculations for those. But I do think it important to note >>> just how tiny the amount of metal in our crystals really is. >>> >>> Now, mercury is purportedly the second-most-toxic metal after >>> Plutonium. But Pu derivatives are uncommon. In fact, until >>> recently (4zhd) Pu derivatives were unheard of. The authors I'm sure >>> will tell you 4zhd involved no small amount of paperwork. But as >>> long as you are not working with Pu, you can regard every other >>> metal as less toxic than Hg. >>> >>> Another good example is selenium; by far the most common metal >>> derivative. Although toxic, Se is also a dietary requirement. I >>> suppose this is an excellent demonstration of what "moderation" >>> really means. The Recommended Daily Allowance (RDA) of selenium in >>> the USA for adult men and pregnant women is 55-60 micrograms per >>> day. In crystals, one Se atom per 100 amino acids at 50% solvent >>> comes to an overall concentration of 50 mM. So, a 100 micron >>> crystal contains about 4 ng of Se. It would take 15,000 such >>> crystals to add up to the US RDA. The synchrotrons I work at don't >>> go thought that many crystals every day. But even if they did, I'd >>> stick to my commercially available multivitamin to get my dietary >>> selenium. >>> >>> So, although it is never a good idea to be sloppy with chemicals in >>> the lab, I think it is also important to do the math and think about >>> not just the toxicity of the things we work with on the bench, but >>> the everyday items all around us. It is never a good idea to be >>> antagonistic with regulators about such things. They are only trying >>> to do their job, and all they are trained to know about are LD50s >>> and how to stay as far below them as possible. A little >>> gently-pointed-out insight into non-lethal applications of heavy >>> metals can be helpful all around. The over-the-counter drug Pepto >>> Bismol (bismuth subsalicylate) is almost 50% bismuth by weight, a >>> metal that is right next to mercury on the periodic table. >>> Brominated vegetable oil contains no bromine, by the way. And >>> dandruff shampoos such as Selsun Blue make an excellent and >>> surprisingly radiation-hard reference for the selenium edge. >>> >>> -James Holton >>> MAD Scientist >>> >>> On 9/4/2017 3:13 AM, Dr Stephen Graham wrote: >>>> Hi all, >>>> >>>> (This email is aimed primarily at my UK colleagues, but feel free to >>>> read on and gloat that you don't have to write safety forms in your >>>> lab/country!). >>>> >>>> I need to sort out written risk assessments for heavy atom soaking of >>>> crystals in my lab. I wondered whether anyone would be willing to >>>> share the risk assessments they have in their institute/company so >>>> that I can seek inspiration and make sure I'm keeping up with best >>>> practice. >>>> >>>> Many thanks, >>>> >>>> Stephen >>>> > -- Prof. George M. Sheldrick FRS Dept. Structural Chemistry, University of Goettingen, Tammannstr. 4, D37077 Goettingen, Germany Tel. +49-551-39-33021 or -33068 Fax. +49-551-39-22582