January 1998 Volume 20 Number 1
I was asked at the WAAC Annual Meeting (in Phoenix) about the potential exposure of the conservator to lead when preparing lead coupons for use in the Oddy test and its variations. Good question!
Metallic lead's high sensitivity to, and distinct corrosion products caused upon exposure to gaseous pollutants is used to test materials to be used in storage and display cases. A small piece of lead sheet (the coupon) is placed in the same microenvironment with the questionable material. Growth of, among other possibilities, lead formate crystals or a basic lead carbonate crust on the coupon indicate that the test material is releasing reactive pollutants - generally considered a bad thing.
To provide a receptive surface, the lead coupon is cleaned before being used in the test. And there, quite literally, is the rub. Abrading the surface can generate lead dust. And if you have read my last two columns ("I think we have a problem" in May and "Lead Sucks - HEPA Saves" in September) you know just how serious a health concern this can be.
Cleaning the coupon liberates fine particles of metallic lead, lead oxide and probably some lead sulfide. If you are doing this manually, you probably transfer lots of these particles onto your hands. You might even slip and abrade the tip of a finger or two.
Here is my considered suggestion on how to polish a lead coupon safely. But I must emphasize that this is my opinion only. It hasn't been looked at, much less verified, by an industrial hygienist, nor is it the recommendation of WAAC or any of the WAAC Board.
This discussion presumes you do not have access to metallographic or microscopic polishing equipment. (If you do, use copious running water and wear gloves. You are entirely safe, but possibly violating clean water standards.)
For the low-tech approach: Wear disposable gloves! Latex gloves should be fine, but I would opt for the disposable Nitrile gloves as they are quite tough and tear resistant.
Lay down two pieces of polyethylene plastic sheeting one on top of the other. [6-mil is the thickness required in HUD Guidelines.] The sheets should be large enough to be easily folded up along with gloves, paper toweling and abrasive paper.
Place a piece of 600 grit silicon carbide abrasive paper (or whatever grade and type you normally use) in the middle of the plastic sheets. Wet the abrasive surface with a drop or two of water and polish the coupon as you normally do. (I was taught a figure-eight was the best way to minimize directional scratching.) Avoid abrading a hole in your glove.
Rinse the coupon over the work area. Use a small amount of water or a damp bit of cotton or paper towel. Dry with paper towel if you like.
Proceed to clean all of your coupons.
When completed, place all cotton and paper towels on the abrasive paper. Sop-up any puddled water with paper toweling. Remove your gloves and add them to the midden in the middle of the plastic sheets. Carefully fold up the upper plastic sheet beginning at the corners and seal it with duct tape. Wrap up the lower plastic sheet around the upper and seal it as well. Dispose of this bundle properly. It should be treated as contaminated hazardous waste. [Exactly what "dispose of properly" means will be discussed in a future column.]
Wash your hands.
You are probably thinking: "Chris has lost it. He didn't even mention wearing a lab coat and respirator!"
Wearing protective clothing (that you don't wash or wear at home) is always a very good idea. And while wearing a respirator won't harm you, in this case, it probably does no good either. Lead dust is very dense and tends to fall straight down from where it is generated. Airborne lead dust is generally not a problem unless you are working pretty hard to get it into the air - as happens with power sanding or air abrasive cleaning. More importantly, as the coupon is being wet sanded, there should be no dust produced as long as the work area within the plastic sheeting is kept damp.
I received a call a few days before writing this column. A colleague had taken a drink from the wrong bottle in the studio. Instead of drinking water, she had taken a swig from a bottle of dilute hydrogen peroxide bleaching solution.
Before reading further, what should the conservator have done? What would you have recommended?
Since the conservator was able to call me and said she felt OK but was worried, this wasn't a 911 emergency.
Determine the identity of the poison. Hydrogen peroxide. In this case, the concentration is important. Fortunately, it was dilute. She gave me the proportions and I calculated the dilution to be 0.9%. The stock chemical was unstabilized, pharmaceutical grade, so there was no concern about poisoning from a stabilizer.
Call Poison Control. Do you have the number near the phone? I'm embarrassed to admit I didn't. The number is in the front section of the telephone directory. Look it up. Write it down.
I gave the number to the conservator. I waited. I thought about the survey the AIC Health and Safety Committee had just completed. See the next issue of AIC News for details, but we know that almost everyone in conservation, at least on occasion, eats or drinks in their studio.
I waited. I began to think about this sort of accident. In a way, it is surprising that it hasn't happened more often. To state the obvious, you should not be eating or drinking in the workplace and you should NEVER store conservation chemicals in the same types of containers in which you store food or drink. (In this case the culprit was a 2 liter plastic soda bottle.).
I waited. I went to my reference shelf. I found very little. The Merck Index did mention that hydrogen peroxide reacts with albumen.
The conservator called me back. Poison Control said s/he would be fine and that 3% hydrogen peroxide is given orally to animals so 1% wasn't going to kill her.
Since it was just before the holidays, and it could do no harm (with the possible exception of salmonella poisoning), I suggested an egg nog chaser made with raw egg white. My reasoning was that if there was any peroxide left, it would react with the egg white. At the very least, it would be a pleasant, relaxing beverage.
All turned out well. The recipe for nog, however, needs sugar.
Best Wishes to all for a SAFE and happy new year.
Thanks to Dr. David Scott and (WAAC Member-at-Large) Cecily Grzywacz at the Getty Conservation Institute for informative discussions about the lead coupon issue. Thanks to my colleagues on the AIC Health and Safety committee for letting me preview the results of our survey.
Chris Stavroudis is a conservator in private practice.