Volume 13, Number 3, Sept 1991, pp.24-25
Sit down. Relax, take a moment. Forget your treatments, just for a short while. Comfortable? I would like to tell you a story. Well, perhaps more of a parable.
Everything is complicated. Conservation is complicated. So too, toxicology is complicated.
Someone might ask you: "What is the best way to clean a painting?" or "How can I bleach a print?" If you are nice about it, about all you can say is "carefully" or "don't."
"Just how toxic is xylene?" Well, it is toxic; don't expose yourself to it. "Never? How toxic? More toxic than..." Well, somewhere between "carefully" and "don't."
Assessing health risks of materials is not a simple matter. Understanding the full mechanism of any interaction between a living organism and an environmental agent is a tricky business. I have recently read an article which can be thought of as a parable addressing the complexity of toxicology.
In the November 1990 issue of Scientific American (Vol 263, no 5, pp 16-20), the "Science and the Citizen" column's lead entry was entitled "A Great Poison". The piece, written by Marguerite Holloway, examines research on dioxin.
Dioxin is a family of 75 chemicals, but usually refers to TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin). Dioxin is the material that contaminated the Italian town of Seveso in 1976, where it is estimated that two to ten pounds of TCDD were released into the environment. Dioxin is the trace contaminant in Agent Orange, used in the Vietnam War, suspected of causing increased incidence of cancer in veterans exposed to the defoliant. Dioxin is the stuff that is present in trace amounts in effluent from chlorine bleaching of wood pulp containing lignin. (That hits closer to home.)
Dioxins have been known to be potent carcinogens for some time. Studies, however, have been contradictory. Different animal species react differently to low doses of the poison. Hamsters are unaffected by a dose of dioxin that is lethal to a guinea pig. Female rats develop liver cancer upon exposure, but male rats do not. These counterintuitive results appear in studies undertaken under laboratory conditions.
TCDD is an extremely potent toxin. However, at low level exposures to humans, dioxin's effects are more difficult to pin down. Quoting from the article: "Epidemiological studies finding increased occurrence of soft tissue sarcoma and non-Hodgkin's lymphoma in people exposed to dioxin have been hotly contested; studies finding no such associations have also been widely criticized."
What is interesting is that it is beginning to look as if dioxin does not cause cancer directly, but may function as a cancer causing hormone--a cancer promoter rather than an inducer. Just as a hormone, TCDD reversibly binds to an intercellular receptor at the cell membrane. The dioxin-receptor pair then bind with DNA in the cell's nucleus triggering the formation of enzymes. Yet the TCDD does not damage the DNA; it is not a mutagen.
The dioxin-receptor seems to have four or five binding sites in more or less the same area of DNA. Generally, this type of redundancy is interpreted to mean that the site serves (or perhaps served) an important biological function. The really fascinating notion is that the site may be a disused bit of biological history. Perhaps the site served an evolutionarily important function in our distant past. A vestigial gene, now as useful as our tail-bone, may be promoting cancer. Isn't that a kick in the...
It should be pointed out that dioxin-as-hormone remains a theory. Also, by way of a disclaimer, I am a conservator and not a toxicologist. I relate this to you as a story not as reportage. I was intrigued by the complexity (and the possibility of new perspectives) in dealing with one of the most studied carcinogens in our Pandora's box of better living through chemistry.
Catherine McLean drafted a set of Health and Safety Guidelines for the Textiles Conservation Department at the Los Angeles County Museum of Art, and she sent me a copy. She reports that she was goaded into action by last issue's column, as I hope others of you, dear readers, were.
(Chris Stavroudis is a conservator in private practice.)
I have based the following "Guidelines for the Usage of Laboratory Chemicals" on the list she sent.
- Before using a chemical or supply, know whether it is hazardous. If you know it is safe, proceed. If you know it is hazardous, proceed only after adequate safety materials have been gathered. If you are unsure, do not assume the material is harmless. Consult the Material Safety Data Sheet (MSDS) or ask someone who does know the material's hazards and what precautions are necessary.
- When working with hazardous chemicals, use protective clothing such as goggles, respirator, gloves and apron as is deemed sensible and necessary. Consult the MSDS if in doubt.
- Use proper chemical handling techniques. Verify that you have the correct material (i.e., reread the label) before opening or dispensing it. Do not contaminate stock solutions or chemicals. Do not pour unused materials back into stock containers. Do not carry more chemicals or solvents than you have hands for (i.e., no more than two at a time). Pour liquids with the labels facing up when possible. Beware of drips and dribbles when working with liquids. Always add acids or bases to water, not water to acids or bases.
- Always label your bottles, jars and beakers. Date chemicals or solutions that have limited shelf life. For complex solutions, include proportions or mixing directions on the label.
- When working with volatile chemicals, replace the lids on the bottles, or place a watch glass or cover over beakers, even during active use. If you choose not to tighten the lids on bottles while using them, be very sure to tighten them when you step away, even for a moment, to avoid accidental spills.
- Place solvent soaked swabs into covered containers. (See the Health & Safety column in WAAC Newsletter Vol. 13, No. 2 for ideas on this one.)
- When working with volatile chemicals, ensure proper ventilation. If you have an overhead exhaust system, place the vents as near the work area as is safely (for the object) possible. Do as much work as possible in the fume hood; e.g., mixing solvents.
- When a project is completed, dispose of all solvent waste, solvent soaked swabs, blotters, etc., properly. Do not leave unlabeled beakers of chemicals around the studio.
- Empty solvent soaked garbage nightly.
Confronted with the mutually exclusive evils of chemicals and food in the studio, Catherine and the Textile Lab opted for food, under highly controlled circumstances. Solvents, which she proudly reminded me are seldom used in textile conservation, were moved into other departments' storage areas.
Eating and drinking in the Textile Lab are exceptions to normal safety policy and may be suspended at any time. Such exceptions must be treated with great care. Eating is allowed in only one section of the lab. One sink is reserved for food related items and is not to be used for chemicals or lab equipment. Eating or drinking is not allowed while any chemicals are actively being used. After eating or drinking, clean-up is mandatory. Food related garbage must be securely tied in a plastic bag.
As I was asked for my comments: I am very impressed with the thoroughness of the list. My only addition to the rules about food in the studio would be to consider the case where an object may have been treated with a poison or toxic substance. When such an item is under treatment, all other people in the lab must be advised, and all eating and drinking must be suspended until after a vigorous cleaning.
The first page of the document Catherine sent is a statement of general philosophies. They are sound, wise, and bear repeating.
- The health of everyone and everyone's unborn children is important and is to be respected. It requires everyone's cooperation.
- The lab stores as few chemicals as possible. Quantities of these chemicals are also kept at a minimum. Chemicals are stored, used, and disposed of in designated areas only.
- Food, eating utensils and cleaning utensils are to be kept distinctly and strictly separate from lab chemicals and supplies.
- Cleanliness and neatness are of paramount importance. Everyone must clean up after him or herself.
- Art always has the right-of-way.