September 2000 Volume 22 Number 3
(Get) Down with OPP (, you know what I mean)Chris Stavroudis, column editor
In addition to rambling on in this column, I am also on the AIC's Health and Safety committee. It is a great group of people and I learn a lot. One of the tasks that committee members share is personing the Health and Safety booth at the AIC Annual Meeting. While it is something of a nuisance (don't ask me how, but I managed to duck out of both the set-up and tear down this year), it is also really fun to stand behind the table and talk with conservators about their health and safety concerns.
The most common question I was asked was about balancing work and pregnancy. To state the obvious, we want to avoid exposing an unborn child to any toxins. But most expectant conservators can't (and often don't want to) absent themselves from work for their entire pregnancy.
I was asked twice specifically about wearing a respirator during pregnancy -- not for cases of true exposure where you would definitely want protection, but for very low level, almost nuisance exposure. (Someone at the next easel is inpainting with xylene. You can't really even smell it, but you would feel safer not being exposed at all.) Again, the problem is obvious: wearing the respirator will filter out any potential exposure, but will the added breathing strain cause blood oxygen levels to decrease?
On the shuttle to the airport, I met a conservator (whose name I can't recall) who had wondered about the same question. But she and her doctor did something brilliant. Her doctor hooked her up to a blood oxygen monitor, she donned her respirator, and performed the sort of light physical activity typical of her work environment. They noted no decrease in blood oxygen level. Question answered.
Obviously, this presupposes that you are healthy enough to wear a respirator in the first place. And these results don't necessarily apply later in the pregnancy. Also, don't forget that during pregnancy changes in a woman's body may effect the fit of a respirator. But now we have an answer, however guarded and informal, as well as a simple test you can perform with your doctor's consent/support. (If anyone out there repeats this test, please let me know. And, that conservator -- and new mom? -- on the shuttle bus, please drop me a line.)
Another blip on the Health and Safety radar: British Chemical Regulations have required indicating silica gel be labeled and disposed of as a hazardous material. This caused an immediate stir within the conservation community.
It is indeed a new millennium. The new regulations in England went into effect on July 1. A clear and well researched email was sent on August 24 by James Hales, Collections and Conservation Assistant at the Institute of Archaeology, London. This was posted to the OSG-list (of which I am not a member, but former WAAC Board member, Linda Strauss forwarded a copy to me). Former WAAC Board Member Cecily Grzywacz forwarded a different version of the email from the icom-cc list to me, also for discussion in this column. Former AIC Health and Safety committee member, Dan Riss of the National Park service made some further inquiries and sent an email to the AIC Health and Safety committee summarizing his results.
Mr. Hales included the URL for GeeJay Chemicals, Ltd. (UK) website http://www.geejaychemicals.co.uk/cobaltchloride.htm in his email. GeeJay sells silica gels and has posted the above cited web page which includes a concise summary of the regulations, new recommendations for safe handling of indicating silica gels, and a revised MSDS for indicating silica gels. And now, by the time your read this, it is probably all old news. I can't help but marvel, these are indeed wondrous times.
But I digress, back to the topic at hand -- indicating silica gel. The entire brouhaha is over the cobalt chloride present as the indicating element in the silica gel. It is present in concentrations of 0.5 to 1.0% by weight. The concern is that the silica gel generates dust and the dust contains cobalt chloride. (For the time being, we will ignore the silica present in the dust and what health hazard that might pose.)
According to the on-line MSDS from Mallinckrodt/Baker (revised 11/99) http://www.jtbaker.com/msds/c4928.htm inorganic cobalt compounds are an A3 animal carcinogen. The ACGIH TLV (threshold limit value) is 0.02 mg/M3. According to the GeeJay website, "Cobalt Chloride has been classified by IARC (International Agency for Research on Cancer) in Group 2B. Possibly carcinogenic to humans."
Thus far, however, in the US, cobalt chloride is not listed anywhere that I could find as a suspected human carcinogen -- not even California's Prop. 65 list. However, I would expect that to change directly.
That cobalt chloride has not yet being listed on any US based hazardous materials registries is, in my opinion, immaterial. Whether you are concerned about possible exposure to a newly recognized carcinogen or you feel that the risk posed by indicating silica gel is grossly overstated, I think your responses should be the same: Phase out the use of cobalt chloride based indicating silica gel.
Silica gel is used in two ways to control microclimates for artworks. As a desiccant, it can keep metals at lower than ambient RH levels. As an RH buffer, it can help maintain consistent humidity levels for works that are at risk of damage by environmental fluctuations. The latter usage has no need for indicating silica gel.
If you are using silica gel as a desiccant for maintaining a very low RH you should either look into one of the newly developed cobalt-free indicating gels, or use another form of monitoring to determine when the humidity in the microenvironment is increasing, indicating that the gel needs to be reconditioned.
If you continue to work with indicating silica gel, by all means follow the safe handling procedures discussed on the GeeJay website and in their MSDS - wear a particulate respirator (with a HEPA filter, not a dust mask) and gloves. In addition, wearing a lab coat and vacuuming the work area after handling with a HEPA vacuum would be a very good idea.
Now comes the ethical dilemma: how to dispose of the indicating silica gel you are currently using. It is still legal to dump it in the trash, but likely that will change. Should you dump it in the trash? I would suggest you shouldn't dispose of it as municipal waste. It is better to err on the side of safety. In addition to possible carcinogenicity, the cobalt is toxic to aquatic life, so if the indicating gel is disposed of in a way that can contaminate ground water or runoff ... well, that's just not nice.
So, if you have relatively small amounts to dispose of, process it as hazardous waste. If you have larger quantities to jettison, I would suggest contacting the manufacturer and asking them for a recommendation on disposal or reuse of the material.
Another concern: Those cute little RH indicating cards (as well as RH indicating test papers) that turn from pink to blue seem to use cobalt chloride as the indicating medium. I spoke to a representative from Humidial about the cobalt issue. Yes, their cards are based on cobalt, and they are preparing special labeling to address the issue. As the issue is inhalation of cobalt dust, under normal usage, there shouldn't be a problem. However if the card gets wet (say in a condensing environment) there is the possibility that the cobalt chloride could migrate and recrystallize where it could conceivably become airborne. So don't allow the cards to get wet. If they do get wet, wrap them up and dispose of them.
And, don't put the pretty little pink and blue squares in your mouth or have them located where little people might be tempted to do the same.
While mining for cobalt salts on the web, I was shocked to find that orthophenylphenol (o-phenylphenol, opp) has been listed as a suspected human carcinogen on California's Prop 65 List of Chemicals Known by the State of California to Cause Cancer or Reproductive Toxicity http://www.oehha.org/prop65/prop65_list/Newlist.html.
I was flabbergasted. My first thought was "What about Lysol® spray disinfectant?" Well, it tuns out that Lysol® hasn't contained o-phenylphenol for some time (see the Cons DistList archives). The current formulation's active ingredients are: alkyl dimethyl benzyl ammonium saccharinate 0.1% and ethanol 79.0%. The archaic spray can that I still retain (we estimate that it is between 10 and 20 years old) lists as active ingredients: o-phenylphenol 0.1% and ethanol 79.0%. Then it hit me? "My God, how much of the world (or at least the overly sanitized US) has been sprayed with this stuff?"
Again, I will digress. (unfettered digressing is one of the joys of writing this column)
One of the underlying principals of toxicology is that "the dose makes the poison." In other words, something is poisonous when it exceeds a certain threshold concentration. While some toxic materials have very low thresholds measured in micrograms, even something like table salt can be a poison if one really works hard at getting a sufficiently high dose into the body. Carcinogens are a different story. The prevailing scientific premise is that there is no safe level for a carcinogen. As levels of a carcinogen decrease, the odds of an individual person getting cancer decrease, but they never vanish.
So, think about Lysol® in the good old days. Spraying it in the air to freshen the room. Keeping the kids safe from 99.9% of harmful germs. There is probably a moral here -- something about not using products you don't really need, but that's not really part of my job in this column. Until the other day, I had thought that opp was the sole remaining "safe" preservative and anti mold material from the good old days of conservation (naphthalene, thymol, and paradichlorobenzene all having bitten the dust). I guess those innocent days are gone.
And lastly, in the March 2000 issue of ACTS FACTS, there is a frightening article entitled, "Hydrofluoric Acid: Not for Amateurs." Anyone who uses, or even possesses hydrofluoric acid (HF) must have this information. Some highlights: "Users should remember that concentrated HF covering 2% of the body can be fatal." "ADVICE. As soon as HF is ordered for use, a facility should alert local hospitals to train their own personnel in the special emergency procedures needed.... ACTS urges even professionals to cease using HF whenever possible. If HF must be used, follow the guidelines in AlliedSignal's excellent booklet: "Recommended Medical Treatment for Hydrofluoric Acid Exposure." It can be obtained from AlliedSignal Inc., P.O. Box 1053, 101 Columbia Road, Morristown, NJ 07962-1053. Write or fax 973/455-6141."
Next column: A special shout-out to the first person who "gets" the title of this column.
Chris Stavroudis is a conservator in private practice.