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