ENVE 649, Module 4, Closure
***Dr. Wetterhahn's MSDS
The best answer to quiz Question 10 that asks, "What information on the MSDS sheet that might have helped Dr. Wetterhahn?" is "nothing." Think about this, Wetterhahn died in 1997, six years ago. About five years ago, her employer, Dartmouth University, was fined several $9,000 and the incident was written up many times in science and laboratory magazines. See http://www.udel.edu/OHS/dartmouth/drtmtharticle.html for a good write up.
Because of it is very lipophilic and extremely rapidly absorbed, it is unlikely that washing is of any help. Medical care is fine, but Wetterhahn had lots of good medical care, albeit a little late, it did not help.
The point is, that latex gloves are standard laboratory wear and are no good at all against DMM, and there was no clue on the MSDS sheet about this, nor about its extreme toxicity via the skin. But the main point I was trying to make is, the sheet you read is now, this minute, is on a university's web site, and neither the university, nor the chemical vendor, nor the manufacture, have changed the MSDS sheet to reflect the extreme toxicity of DMM or it very rapid penetration of the standard lab gloves - six years after Dr. Wetterhahn's demise. Take home message is that MSDS sheets are limited, not always updated, and often contain inaccuracies. The usually are, however, better than nothing. They are often a quick means of getting information, but do not regard them as the last word on chemical safety.
***Q. While completing the MSDS assignment I was stumped by the mention that both the MSDS sheets had made concerning the exposure limits. As given in the first MSDS, I would assume that the "Typical TLV/TWA 40 mg/m3" was a reference to the concentration of this chemical in the air. The second MSDS gives ACGIH 5 ppm Ceiling level. I assume this is also concentration of contaminate in the air. Do you have to know the molecular weight to do a conversion from ppm to mg/m3? This seems cumbersome and unclear. It would seem that you would need ceiling level, STEL and the TLV if you were going to work with this product.
A. First confusing point is that the one is stated as mg/m3 and the other as ppm. If you know the MW you can convert them. There was an optional webpage on that back in Module 1 that explained that: http://www.faculty.uaf.edu/ffrap/EQE_649/Module_01/1F_Measuring_Dose/ppm_to_mg.html
Logically all air contaminants would have both an STEL (15 minutes) and a ceiling. But as a practical matter, only a few need that. An 8-hour TWA is usually appropriate because the absorption and distribution process in the body reduces the concentration of the chemical at the target organ to a smoothed out average. However, for some chemicals the target organ is the eyes or nose, and the effect is irritation. If the ceiling is exceeded, irritation might occur, perhaps impairing ability to see and work safely. Other chemicals affect the nervous system quickly. For these a short exposure might impair the ability to self-rescue, or just to work safely. These often have an STEL. Beyond that, use of STEL and C depend on the particular chemical, and also on practical results of industrial exposures, monitored over the years.
***Wetterhahn and MSDS. Remember, the MSDS sheet you read was posted after Wetterhahn's well-publicized death. The sheet mentions that "harmful if absorbed through the skin," but no indication of the extent of harm is mentioned. Also, it simply says "Protective gloves and clothing should be worn" which Wetterhahn did. It is just that latex was not "protective" at all. (It also gives the completely incorrect advice to flush with water, this chemical is absorbed practically instantly.) (One of the students located a more recent MSDS that specified better gloves.) This is an example of the limitation of MSDS sheets. They are a good starting place, only.
** Q. OSHA regulation set the requirement of MSDS sheet but it seems it has not made any format (as ANSI has done). I am confused whether OSHA has specifically pointed out any points that should be included in MSDS sheet or not. Is it legally necessary for the American Chemical companies to follow ANSI format?
A. The OSHA regulations specify a few items, in general terms, that must be in the MSDS sheet. Most large chemical companies follow the ANSI format, because it is standard and "covers" them, if there is a problem. It is not required.
Q. The use of the MSDS sheets is quite interesting. I really don't understand why there is such variance in what is reported in the MSDS sheets from the different manufacturers or why they are not required to test them. I would like to think that it is the manufacturers responsibility to make everything about their product readily available to the public to basically "cover their own ass". This doesn't appear to be the case.
A. A manufacturer, or marketer, only needs do the minimum, or the arguable minimum, that the law calls for. They would need some sort of incentive to do any more. The large manufacturers have toxicology departments, who might do little real testing, but who will do through literature searches. On the other hand, manufacturers of consumer products or food additives come under different laws and do extensive testing, also, people are supposed to be "exposed" to their products. For the vast majority of chemicals, however, the only exposure is workers, and protection of the workers is primarily by their employer, not the supplier of chemicals. The last reason is simple economics, though testing, of the type used for a new artificial sweetener, might cost 30 or 40 million dollars. That level of testing is not justified for most chemicals.