Blood Test
What – the reader says – does this title have to do with daguerreotypy? Well a little more safety information heading your way. I recently stopped by my health care provider for some routine blood tests. I also arranged with my doctor to get a mercury blood level as well. Here are the results:
The screen capture is a little hard to read, but I passed. I did this to establish a baseline blood level before I start working with mercury. I plan to get an annual test to get a definitve read on whether my safety measures are working. My health plan covered the test, so it didn’t cost me anything. I asked one of my nurse friends however and she tells me it is a pretty cheap test (about USD $25). Even if you are a longer term practitioner you might want to get one done the next time you have to get other bloodwork. You will quickly find out if you have anything to be concerned about.
Happy (and safe) dagging. :)
Daguerreotype Process | andy | April 9, 2009
QuackWatch Site
Urine tests for mercury are more accurate than blood tests and easier on the patients.
Hi Matt -
Thanks for the heads-up about mercury urine tests. Some people certainly avoid any kind of blood test so this information might encourage them to get tested. I will look further into the information on the Quackwatch site that the urine test is more useful/accurate than the blood test. Quackwatch is a site well respected in the healthcare world, so their assertion carries some weight.
In either case, because daguerreotypists have a potential for exposure to mercury that can exceed safe levels it would seem prudent to get some kind of testing done on a regular basis.
I agree. I believe anyone who is often in the vicinity of mercury for any reason should get tested regularly. It would be quite reckless not to.
All of the information I’ve seen says that urine tests (unprovoked by any chelating agent) are the best for detecting exposure to elemental mercury. I’ve read that blood levels of mercury drop rapidly and are only good for detecting recent exposures.
I’m also very curious as to the test you did with the mercury detecting powder, the ammo can, and the eyedrop bottle full of mercury. This test implied that mercury could pass through plastic. I’ve read conflicting information regarding this, many sites that give instructions for cleaning up mercury spills inform people that “any airtight container” or “sealed plastic bag” will be enough to contain mercury vapors. I know for a fact that some organic mercury compounds can most readily pass through plastics, as was proven with the tragic death of Dartmouth chemistry professor Karen Wetterhahn. She spilled one drop of dimethlymercury, the most toxic mercury compound, on her latex gloved hand and that was sufficient to cause her prolonged, horrific death over the course of the following year.
However with elemental mercury I remain unsure. Was the plastic eyedrop bottle 100% air tight? No hole in the top or loose screwcap? Also might there be a possibility that some mercury was once spilled in the ammo can which could have caused the color change? I would be most interested to read about the results of any additional experiments designed to determine the permeability of mercury to plastic. I understand if you don’t want to devote any more time to it though, since as you wrote, you’re doing this to be an artist and not a technician.
Hi Matt – I do intend to do more testing. I am a public health nurse and am very interested in promoting the safety of fellow workers who are keeping this amazing photographic process alive. Because I have limited time though I want to make sure I make progress on becoming a daguerreian artist as well.
Because I am working under fairly primitive conditions, I can claim no real rigor in any of my experiments so far, so I hesitate to make any broad claims. I can tell you that the “eye wash” bottle I tested was free of both leaks and external contamination at least to the level of a naked eye examination. I could see no mercury droplets of any size in the ammo can.
Since that initial test I have also examined a small HDPE bottle that was actually advertised as being “ideal for mercury”. The bottle was new, it had been very carefully filled to avoid spillage and further the cap had been sealed with tape. Since it was sent to me by another daguerreian, I am not sure exactly what tape was used.
I placed that bottle in a new lab grade glass jar with an HDPE lid with a disk of PTFE on the inner face. I placed a small amount of mercury detecting powder inside the glass jar. That powder showed color changes indicating exposure to mercury vapor within 24 hours. At present I am assuming that all plastic is suspect until I perform further tests or see literature concerning lab based testing.
Thanks for the info. I also found a few paragraphs in the “Plastics Engineering, Manufacturing and Data Handbook”, which is available online at google books that related to this. The section was mainly talking about water vapor but it was written:
“It should be recognized that all plastic materials over a time period allow a certain amount of water vapor, organic gas, or liquid to permeate the thickness of the material. It is only a matter of degree of permeation between various materials used as barriers against vapors and gases.
There are substantial differences in the rates at which water vapor and other gases can permeate different plastics. For instance, PE is a good barrier for moisture or water vapor, but other gases can permeate it rather readily. Nylon on the other hand, is a poor barrier to water vapor but a good one to other vapors.”
It doesn’t say which specific plastics would be ideal for the containment of mercury, but from this and your experiments I think it can be concluded that mercury is better kept within glass vessels with tight fitting glass (or perhaps metal) lids. But who knows, maybe it permeates through those materials as well.
I hope for the sake of those many daguerreians who have and will continue to keep their mercury in plastic (or even plastic lidded) bottles that they’ve at least prevented most of the vapors from escaping. Is only the slightest bit of vapor enough to cause the color shift in the powder, or will it only change when a larger amount is present?
Unfortunately the test powder doesn’t provide much in the way of qualitative information, and there are no instructions either. Lesser amounts of vapor seem to create slower and lighter color changes, but no color chart or time chart is provided to help interpret the differences. As such it is a fairly crude test. It would probably be possible to develop an interpretive chart, but I imagine the sellers don’t see it as useful. Their point is color change=Hg vapor=BAD and that’s all you need to know.
My next test planned will be with a glass bottle I have with an HDPE screw top lid and a layer of PTFE acting as a gasket. I am hoping that the combination of plastics will be more effective.