ARC-Nucléart - CEA-Grenoble

   2007

 

----- Original Message -----
Sent: Friday, March 02, 2007 6:47 AM
Subject: RE: from IPEN - request to visit in april

Dear Ms Crescenti,
Thank you for your message, and I just talked to my colleague Laurent Cortella about your request visiting our laboratory at the same time with Ms Brocardo Machado.
We will be very pleased to welcome you at this opportunity, for visiting our facilities and discussing about the problem of paper disinfection.
For your entrance in our Center, we need a copy of your passeport, and your organism ,employer (IPEN ?), and your function.
Could you e-mail or fax the passport to me ?
Best regards,
 

Khôi Tran
ARC-Nucléart
CEA-Grenoble
17 rue des Martyrs, 38054 Grenoble Cedex 09 France
Tél: 33-(0)4 38 78 39 36
Fax: 33-(0)4 38 78 50 89
Mail: quoc-khoi.tran@cea.fr


                                                                                    


 

ENEA - ROMA

2008

 


----- Original Message -----
From: "Marianna Adamo" <marianna.adamo@casaccia.enea.it>
To: <margotcrescenti@uol.com.br>
Sent: Tuesday, June 03, 2008 6:48 AM


> Dear Dr. Crescenti, Dear Dr. Machado,

Dr. Magaudda sent me this e-mail.
We have appreciated very much your interest for our activities.
I inform you that it is certainly possible visit our facility on 29 
th or 30 th September but the admittance to the irradiation buker is 
considered on the spot, according to irradiations in progress that 
now are not possible to foresee.
I think to be here on 29th and 30th September .
In any case, some days in advance, you have to contact Dr. Stefania 
Baccaro, plant Director, to communicate your citizenship, number of 
passport to allow your admittance to our Research Centre.
Best regards
Marianna Adamo

 Stefania Baccaro
 

                                                                                                


 

 

Buenos Aires - Argentina

2009

 

 

From: "ANA MARIA CALVO" <calvo@cae.cnea.gov.ar>
To: "Margot Crescenti" <margotcrescenti@uol.com.br>
Sent: Monday, January 26, 2009 3:55 PM
Subject: Re: [posible spam] Re: Re:ola


Con Mucho gusto, puedes visitar el Centro Atomico Ezeiza donde podras
ver el Laboratorio de Conservación y Restauracion de Colecciones, El
Lab. de Polimeros y el Lab. de Microbiologia. Lo vamos arrreglando . Yo
salgo de vacaciones el lunes 2 y vuelvo el 15 de febrero. Asi que a la
vuelta lo charlamos y con mucho gusto lo organizamosssssss!!!
Gracias por el mail.
Un beso enorme . Ana

 

 

                                                                               


Invasion of the Giant Mold Spore

 

It's a quiet, peaceful day. You stroll complacently through the aisles of books, contemplating the neat rows of colored cloth and leather. A bit of sunshine glimmers through the distant stacks. A little tune is wandering through your thoughts. Suddenly, a shiver runs down your spine. You stop. Something is wrong; you sense danger. Slowly you turn and peer down the rows of books, half afraid of what you will find. You cautiously step forward, and there it is, lurking in the dark, slowly creeping down a row of books. It slithers from one volume to the next, maliciously victimizing innocent and helpless books. The air is filled with a vaguely unpleasant odor. Books become untouchable -- they are slimy, they are furry, they are distinctly icky. Who knows, it may spread to the carpet, the walls, the curtains, the chairs, even your office; it may take over the whole library! It's the attack of the awful mold!

Before you panic, calm down. Although it won't be easy, mold can be stopped. You can protect yourself from it. This leaflet will provide you with strategies for the prevention and control of mold. Before we come to the strategies, though, we need to analyze our foe. What is mold? Where does it come from? What does it do to books and paper?

I. What is Mold? And Where Does It Come From?

Mold is a type of fungus. It grows on surfaces in masses of branching threads which resemble dense cobwebs. The fertile threads, those which produce spores, often stand up from the surface into the air to release their spores. Spores are carried by air currents or by adhering to insects or animals. Active mold can be any color, depending on the species and the substrate upon which it is growing. Mildew is another type of fungus, similar in structure to mold, but distinct as one species of fungus is distinct from another. The terms "mildew" and "mold" are not interchangeable; they are most often used in the common names of various fungi. Fungi is a kingdom of organisms, with a single division, Mycota. The fungi have traditionally been classified with plants but are now considered a distinct group of organisms. Unlike plants, which produce their own food, fungi absorb nutrients from dead or living organic matter. Fungi also lack photosynthetic pigments. There are over 100,000 known living species of fungus, some of which are beneficial to mankind. Mycologists estimate that there may be as many as 200,000 more unidentified species of fungus. Yeasts, molds, mildews, rusts, and mushrooms are types of fungus.

The spores of fungi that become mold or mildew are always present in the air and on objects. When the temperature and moisture in the environment are suitable for germination, the fungus spore bursts and grows into a thread-like filament called a hyphae. Using the object it is growing on as a food source, the hyphae form a mass, called a mycelium, and within a short time begin to produce spores. At maturity, spore sacs burst and release spores, which eventually land on other material and begin the reproductive cycle again.

In libraries, optimum conditions for mold and mildew development exist when temperature is above 70° Fahrenheit and relative humidity is above 70%. However, some common molds can grow at temperatures as low as 50° Fahrenheit and in relative humidities as low as 45%. It is also possible for molds to begin growing in conditions of high relative humidity and temperature and then continue growing in environments with significantly lower relative humidity and temperature.

II. What Does Mold Do To Books and Paper, and to People?

Basically, mold and mildew eat library materials. Books and paper provide a source of nutrition through such components as cellulose, starch adhesives, and starches in sizing. The mold and mildew excrete digestive enzymes that allow them to eat starches and cellulose, grow, and produce more spores. Cellulose in paper is difficult to digest, so many molds prefer the starch in cloth-coverings on books and in paper sizings. In book collections, mold is often noted on the bindings long before it grows on text blocks. Molds grow rapidly, although they generally grow at a slower rate when relying on only cellulose for food.

Conditions that promote mold and mildew growth (high humidity and warm temperatures) will also, in and of themselves, increase the rate of book/paper deterioration by accelerating the aging process and the formation of acids. Furthermore, mold and mildew can irreversibly stain books and paper. Such stains destroy text and images. Books and paper can also be seriously softened and weakened by mold, making them difficult to handle.

Mold and mildew can have an adverse effect on people. Those with allergies, asthma or other respiratory problems should stay away from infested areas, as many fungi will seriously irritate and inflame lungs. Some fungi can cause skin and eye irritation and infections. Prolonged exposure to germinating molds in closed areas (which exist in many library collections) can damage the lungs, mucous membrane, cornea, respiratory tract, stomach, intestines, and skin. Some varieties of mold are highly toxic, such as the strain found in 1990 in the basement of the New Museum of Contemporary Art in New York City.

III. The Repulsion of the Giant Spore, or How To Rid One's Collection of Mold.

The ONLY way to permanently protect your collections from mold is to control the environment by keeping the temperature within 65º-70º Fahrenheit and the relative humidity within 45%-65%. Prevention is the key, but if you do experience a mold outbreak there are non-chemical means for clean-up and recovery (see section III.B.2.). Some chemicals kill mold, but the only safe and effective way to keep it from coming back is to modify the environment which contributed to the development of mold. Some of the chemicals used in the past by libraries to kill mold are no longer recommended, because many are harmful to both people and collections.

III.A. What is a Mold-Preventive Environment?

There are a number of factors which influence the growth of mold: environmental humidity and moisture content of materials, temperature, air circulation, light, and the chemical composition of potential substrates. Each of these is discussed here in relation to the environments which will inhibit or promote mold growth.

III.A.1. Humidity. The most important environmental factor to control is the amount of moisture in the air and consequently in books and paper. Books and paper naturally contain a certain amount of water. They are hygroscopic, so that when relative humidity goes up, they absorb water to achieve equilibrium. At 50% relative humidity, the moisture content of paper is approximately 7%; at 70% relative humidity, it is approximately 10%. Moisture enables mold to absorb nutrients from book and paper substrates, so the more moisture a book contains, the greater are the chances for fungus spores to germinate at room temperature. The potential for mold or mildew development on wet books is one important reason for quick freezing of books damaged by water.

Relative humidities above 70% can easily lead to mold growth; for safety, it is generally recommended that libraries keep their relative humidity below 65%. Relative humidity below 40%, however, can cause books and paper to become fragile from dryness. Hence the acceptable range is 45% to 65%. It is possible, however, that some molds can begin growing at 70% relative humidity or higher and then continue growing at relative humidities of less than 70%. Because of this, new acquisitions should be checked for mold and treated, if necessary, prior to storing them with the rest of the collection.

Consistency is also important within the 45% to 65% range. As books and papers absorb or release water into the atmosphere with changes in relative humidity, they also change their shapes. They expand or contract, although different parts of a book will do so at different rates, as will different types of paper. For example, a vellum binding may expand quickly as it absorbs water, but the paper inside will expand more slowly, and the adhesive used in binding may expand at an intermediate rate. Fluctuations in humidity, when necessary due to, for example, seasonal changes, should be slow and carried on over time. Generally, it is recommended that relative humidity remain at 50% with a maximum change of plus or minus 5% per month.

III.A.2. Temperature. Most molds thrive at warmer temperatures. When combined with high levels of humidity, temperatures of 70 to 75° Fahrenheit can cause mold to develop. Temperatures below freezing will not kill mold, but they do make it dormant. Few molds will be active at temperatures of less than 50° Fahrenheit. Mold can also grow in conditions up to 140° Fahrenheit. High heat will kill mold, but it will also severely damage library materials.

For patron comfort, temperatures of 70° Fahrenheit plus or minus 2° are acceptable in libraries, provided relative humidity is kept at 50%.

III.A.3. Air Circulation. In conjunction with humidity and temperature control, adequate air circulation will help prevent mold growth. Air circulation helps control moisture levels through evaporation.

Installing a heating/ventilation/air conditioning (HVAC) system with humidity control can solve all three problems of humidity, temperature, and air circulation at the same time. Such systems are not easy to install, simple to maintain, or inexpensive. But they provide the most effective means of preserving your collections. Not only do suitable HVAC systems assist in mold prevention, but they also stabilize the environment and hence eliminate the distortion of materials due to fluctuating temperature and humidity. Furthermore, maintenance of a stable environment slows down processes of deterioration caused by acid, light, and pollution. An HVAC system's control of the environment can also help in controlling insect infestations.

If you cannot install or improve an HVAC system in your library, there are a few alternatives which, although not as effective, will help. Fans can be installed to improve air circulation. They are best placed near outside walls and close to floor level. Portable dehumidifiers can be used, particularly for localized problems. Although you can invest in several units, portable dehumidifiers tend not to be as effective in large spaces as a centralized HVAC system with humidity control. Fans and vents in attics will increase air circulation by pulling air through the building. This is particularly useful when it is necessary to leave windows open. Desiccants (such as silica gel) can be used to absorb moisture in humid environments. They should not, however, be used where young children are able to reach them because ingestion may be dangerous. Desiccants are most useful for localized problems, especially those that can be contained in a small, enclosed space.

Sometimes an older air circulation system can actually be the origin of your mold problems.  When conducting a visual inspection for mold, it is important that duct work and the age of a building be taken into account.  Ceiling tiles should also be inspected; if a damp or stained ceiling tile is in evidence, leaky ductwork may be the culprit, and mold can grow on the ceiling tiles in dark crawlspaces.  Paper or insulation lining the ductwork and old filters that are not regularly replaced are all growth supporting materials for mold.

III.A.4. Light. Sunlight, and in particular ultra-violet radiation, generally inhibits mold growth. The Virginia State Library observed a direct connection between the rate of mold growth and the presence of light during several outbreaks in its collections between 1978 and 1980. It was found that more light correlated with slower growth rates. The relationship between light and mold growth is discussed further in section III.B.1.c. Sunlight and ultra-violet radiation, however, cause serious fading of library materials and can speed up chemical reactions leading to the formation of acids in paper; hence prolonged increases in the exposure of library materials to light are not recommended.

III.A.5. Chemical Composition. Mold growth can also be affected by the chemical composition of the book or paper substrate. Many fungi prefer slightly acidic material. They will also interact with non-cellulose matter within paper, such as iron particles, leading to staining and further deterioration. The chemical composition of most library materials is not something which can easily or even should be changed. But it does make some parts of collections more susceptible to mold growth than others.

III.A.6. Miscellaneous Environmental Modifications. There are several modifications that can be made to the building or its internal environment which will assist in preventing mold outbreaks.

a. Don't shelve books directly against an outside wall. Due to temperature and humidity differences between inside and outside environments, moisture may develop along walls. Allowing air to circulate against the walls will enable the moisture to evaporate.

b. Keep the quantity of indoor plants to a minimum and don't allow indoor planted areas.

c. Waterproof basements and walls below ground level. And use water-sealant paint on floors and walls.

d. Place or adjust outside gutters and drains so that water does not collect near the outside walls. Check gutters and drains regularly to avoid clogs. Place lawn sprinkler systems so that they do not soak outside walls.

e. Regularly inspect your collection for mold or mildew. This will allow you to catch any infestation before it becomes large. And continue to monitor potentially hazardous areas until the environment can be stabilized in an appropriate state.

f.  Install the best filters you can afford in your library's heating and cooling vents.  In recent years the cost of quality HEPA filters has decreased dramatically.  When good HEPA filters are replaced regularly, they can decrease the amount of mold spores as well as dust and other materials that allow for mold growth.

III.B. What Can You Do If You Have a Mold Outbreak?

There are a number of things you can do when faced with mold in your collection, but first you need to determine whether the mold is active or inactive. Active mold can be colorful, and it's damp, slimy and web-like and had a musty odor. Inactive, or dormant mold is dry and powdery. Try looking at in under a microscope, does it appear web like? Or, try brushing it with a soft brush, active mold will smear. Take a sample of the mold to a mycologist to identify the species.

Your second response should be to isolate affected materials. If a small quantity of books is moldy, seal them in air-tight plastic bags. If the infestation is large, quarantine the area.. Isolating moldy books and papers serves two purposes: it minimizes the spread of mold, and it protects those persons who may have allergies or respiratory problems from harm.

Third, determine the source of the outbreak. Check the humidity and temperature. Chances are good that, for a large infestation, the cause at least partially lies there. When the Denver Public Library found mold in its off-site storage facility in 1984 (it was visible on approximately one-third of the books there), relative humidity was 60% and temperature was 78° Fahrenheit. Also look for a source of water, such as an unnoticed leak, a broken window, moisture along outside walls. A third place to check is the heat-exchange coils in the heating/air conditioning system; they are a prime area for fungus growth and spore distribution. They can be cleaned using a commercial EPA registered cleaning solution designed for coils and following the manufacturer's direction for use. It's recommended to have coil cleaning performed by an experienced individual. You need to pinpoint whatever caused the mold to develop and then fix it, because until you solve that problem, mold will continue to grow, no matter how often you treat the affected material.

Every library and archives should have at least one tool for measuring relative humidity -- a hygrometer, sling psychrometer, or hygrothermograph. Used regularly and properly, these tools can alert you to increases in relative humidity before mold growth begins so that you may effectively modify the environment to prevent mold. During an outbreak, hygrometric tools should be used regularly (two to four times a day) to monitor the environment and the effectiveness of your modifications, and to make readjustments as necessary.

Increase air circulation and lower humidity. Open windows, provided it is not raining outside and the relative humidity outside is lower than that inside. Set up fans to increase air circulation. Set up dehumidifiers or re-adjust the HVAC system to lower the relative humidity. If you have a thermostat-controlled cooling system or one which simply lowers the temperature of outside air prior to ventilating it through the building, turn it off. This kind of "air conditioning" or cooling system does not provide humidity control and will in fact increase internal relative humidity because cold air cannot hold as much water as warm air. Furthermore, the moist heat-exchange coils in this system may be providing a fertile ground for the growth of mold, the spores of which are then distributed throughout the building via its ventilation system.

After you have readjusted the environment, you can look at available means for removing mold and cleaning the collections. There are both chemical and non-chemical means to treat mold. Effective treatments can be fungistatic or fungicidal. Fungistatic treatments are those that prevent the mold spores from germinating, but do not kill the mold. Freezing is one such method. Fungicidal treatments kill the mold and its spores. No safe large-scale treatment, however, imparts lasting, or residual, mold control. That is why it is so important to change the environment so that it inhibits mold growth. Furthermore, there is some evidence that books and papers treated with fungicides may be more susceptible to mold after treatment than they were prior to the outbreak. For these reasons, the use of chemicals to treat mold is no longer recommended for library, archival, and museum collections.  In addition, many chemical treatments that seem benign, such as Ozone, may be hazardous to the health of workers, and can cause chemical reactions to some materials in your collection.

III.B.1. Health Issues. Some of the molds commonly found in library and archival collections can cause serious health problems including respiratory infections, headaches, nausea, and eye and skin irritation. People predisposed to upper respiratory problems such as allergies and asthma should not be exposed to areas affected with mold, even if they wear a respirator. For health reasons, even a small mold outbreak should be taken seriously. You should wear disposable rubber or plastic gloves, a lab coat and a respirator whenever handling moldy materials. Ordinary dust masks are not sensitive enough to filter mold spores, use a respirator with a HEPA (high efficiency particulate arrestant) filter. Be aware that respirators are ineffective if used improperly, for example people with facial hair will not be protected because they can't get a tight fit. Training staff about proper fitting and use of respirators is essential. Wash protective clothing in hot water and bleach.

III.B.2. Mold Control and Eradication.

Freezing or air-drying followed by cleaning, do not involve the application of chemicals to the books or paper in solid, liquid, or vapor form, and are the current recommended practices. Any type of treatment must include some temporary modification of the environment. Non-chemical treatments are preferred to chemical treatments because they do not interfere with the chemical composition of the materials, they do not leave residues in treated materials, and they are non-toxic to humans. Many non-chemical means have been discussed and experimented with; I mention the more commonly known of them here. The first step is to inactivate the mold so it can be easily cleaned from the item.

III.B.2.a. Freezing involves placing the moldy books in an atmosphere of below freezing temperatures. It is a fungistatic, not fungicidal treatment, meaning it will halt growth but will not kill spores. Freezing presents an option for halting the spread of mold while you prepare for cleaning.

III.B.2.b. Air Drying of damp, moldy items will inactivate the mold, though it should be done in an area that is vented to the outside or isolated, to prevent the spreading of spores.

III.B.2.c. Cleaning Books and Paper is appropriate once the mold has been inactivated. Vacuuming is the most effective way to remove mold spores from books and paper because it doesn't spread the spores around. You must use a vacuum with a HEPA (high efficiency particulate air) filter. Ordinary vacuums should be used outdoors ONLY, their filters don't trap mold spores, rather they circulate them back into the air. Vacuum mold from flat paper documents through a screen to avoid damage. For books use the nozzle or brush attachment covered with cheesecloth. If needed, residual mold can be wiped from bindings with dry or slightly damp cloth.

You can also clean mold with a soft bristled brush or clean rag, but this technique in some instances can cause increased staining. When wiping off mold, be careful not to brush it into the air indoors or onto other objects; this can be accomplished by wiping books or papers off outdoors or under a fume hood. Replace rags frequently and store used rags in sealed plastic bags until they can be washed in bleach for re-use. For fragile and rare materials, or if you're unsure about how to treat an item don't hesitate to consult a conservator. In some cases it may be necessary to remove active mold which is done through a technique called aspiration and should be conducted by a trained conservator.

III.B.2.d. Low Oxygen Environments are commonly used for pest control. The procedure involves placing the infested item in an airtight plastic bag or fumigation chamber with an oxygen scavenger such as Ageless™ for a prescribed period of time. This treatment for mold is fungistatic, in that it causes it to inactivate or become dormant, but will not kill the mold spores.

III.B.2.e. Gamma Radiation has been used to sterilize surgical equipment and food. Experiments in irradiation of books to kill mold have been conducted by Johns Hopkins Medical Institutions and by the State Central Archives of Czechoslovakia. Although it does kill mold and does not leave residues, there is evidence that gamma radiation softens leathers and adhesives and breaks down the internal structure of paper. The folding endurance of paper decreases with higher levels of radiation. Mold can be killed at lower levels of radiation when heat is applied; heat, however, can also decrease paper strength. Studies indicate that the effects of individual radiation exposures add up, hence repeated disinfection of books and papers with radiation is not recommended. Special chambers and corresponding operator training are necessary for irradiation, sources which are not easily accessible or necessarily affordable for most libraries. Because of the possibility of damage and the difficulty of accessing equipment, gamma radiation as a fungicide for books is not commonly used or recommended.

III.B.2.f. Ultra-violet light, as mentioned earlier, inhibits mold growth and may kill mold. It is not, however, recommended as a full-scale treatment for mold on books and papers because the amount of exposure necessary to kill mold would induce fading and accelerate aging. However, it has been suggested as a possible step in treating small, localized outbreaks. Place the book or document outdoors, fanned open, in the sun, for no longer than 30 minutes. Follow up with cleaning (see above, III.B.2.c). Do not leave books and papers outside overnight, as temperature changes may cause condensation to form. If the book is placed back into a suitable environment, the combination of removing the visible mold and allowing the book to dry out in the sun may halt the further growth and spread of the mold. Books should not be placed outdoors if the relative humidity is above 65%. This process needs careful and continued monitoring, and may not be feasible for a mold outbreak affecting a large quantity of material.

III.B.3. Activities to be Carried out in Conjunction with Treatment.

III.B.3.a. Cleaning the Storage Area. While books are being treated, the area in which they were stored should be cleaned. Begin by vacuuming the area. Then, shelves, floors, walls, ceilings, and windows should be cleaned with a mold and mildew killing solution, such as Lysol, Clorox, or X-14. Make sure the area is properly ventilated while cleaning. Don't return treated books to the area until it has been cleaned. It may also be necessary, depending upon how serious the infestation is, to clean carpets and drapery. Ducts, filters and heat-exchange coils in HVAC systems should be checked and replaced or cleaned with a mold-killing household cleaner.

III.B.3.b. Odor removal. Charcoal and/or baking soda can be used to remove the odor of mold, if the treatment has not done so. Simply place briquettes and/or bowls of baking soda in the area to absorb the odor. Do not wipe the books or paper with the charcoal or baking soda.

III.B.3.c. Monitoring. Continue to monitor the area and the treated books and papers after clean-up and recovery. Changes in the environment should have been made (either before or during treatment) to reduce the possibility of future outbreaks; i.e., humidity and temperature control established, air circulation improved, leaks fixed or other sources of moisture removed. Nonetheless, careful watch should be kept over treated collections to prevent new outbreaks.

III.B.4. Chemical Teatments.

There is now a much greater awareness of toxicity to humans and residual damage to books when applying chemical fungicides. Several chemicals that are fungicidal are not used on book collections because of their toxicity and instability. Some examples are mercuric chloride, highly toxic and legally restricted in the United States; hydrogen sulfide, an explosive; and methyl bromide, which leaves an irreversible foul odor, softens adhesives, and is toxic.

Many chemicals that have been used in the past for killing mold in libraries and archives are no longer considered safe because of the health risks to people, and the potential harm to collections. Consulting a conservator is recommended prior to treating large mold infestations in rare book or manuscript collections.  Do not use chemical treatments unless you have had training by a professional conservator.  Many chemicals can cause severe health problems, and some treatments widely practiced as recently as two decades ago are no longer used, and subject to strict regulation by OSHA.

IV. Concluding Recommendations

Most authorities agree that fumigating collections with toxic chemicals is rarely necessary for dealing with mold and mildew problems. Storing collections in appropriate environmental conditions should prevent the need for fumigation. To quote Dr. Thomas Parker, of Pest Control Services, Inc.:

"Fumigation will not control mold and mildew if the library
materials are placed back into the same conditions from
which they came. In most instances library materials that
have been fumigated are then stored in areas which do not
have an environment conducive to mold growth. The success
of the fumigation is given as a reason for the control of the
mold and mildew, when in fact, the new area in which the
materials are stored is the governing factor as to why mold
and mildew is now being controlled."

Maintenance of proper environmental conditions will prevent mold growth. And if mold does occur, a relatively gentle form of cleaning along with improving the environment will solve the problem in most situations. I recommend that you try the following instead of chemical treatments.

1. Determine the cause: check temperature and relative humidity levels; check to see if the material has been wet and, if so, why; check heat-exchange coils in air conditioning units.

2. Isolate materials: place individual items in sealed plastic bags; quarantine stacks; for large and heavy infestations, it may be necessary to restrict access to the building/room. Don't leave materials in plastic bags for extended periods of time, follow up with cleaning as soon as possible.

3. Modify the environment: readjust relative humidity to the best of the HVAC system's ability; set up fans to keep air circulating in the affected area; install portable dehumidifiers in the affected area if the HVAC system cannot be controlled; turn lights on in affected areas for as long as possible during periods of obvious mold growth. Continuously record temperature and relative humidity until they stabilize at an acceptable level.

4. Clean: Vacuum with a HEPA vacuum, then wipe books or papers with a clean dry rag or a soft brush (wearing proper protective apparel); clean shelves, walls, floors, air conditioning heat-exchange coils, air vents, etc. with Lysol, Clorox, X-14, or other mold-killing solutions; if you are dealing with a small quantity of books, you can set them out in the sun to dry out, otherwise use fans following the ethanol/vacuum cleaning.

5. Monitor: keep watch on the affected area for several months beyond the mold outbreak and clean-up, even after the environment has been restored to conditions which inhibit mold growth.

Research and testing continue to assess the effectiveness of fungicides, to determine appropriate treatment procedures, and to identify molds and mildews and their characteristics. Studies may result in changes to existing procedures for mold control in the future. The SOLINET Preservation Program is able to provide advice and assistance in dealing with mold infestations in specific situations. Please call if we can help.

 

BIBLIOGRAPHY OF SOURCES CONSULTED FOR INFORMATION PROVIDED IN THIS LEAFLET

Abbey Newsletter, v. 7, no. 4 supplement (Sept. 1983). The entire issue is on fumigation.

Ballard, Mary W. and Norbert S. Baer. "Ethylene Oxide Fumigation: Results and Risks." Restaurator, v. 7 (1986), p. 143-168.

Byers, Barry. "A Simple and Practical Fumigation System." Abbey Newsletter, v. 7, no. 4 supplement (Sept. 1983), p. 1-4. Includes description and instructions for constructing a thymol chamber.

Center for Occupational Hazards, 5 Beekman St., New York, NY 10038(212-227-6220). Summaries available on ethylene oxide standards, as well as safe handling procedures for various other chemical fumigants discussed in this paper.

Chamberlain, William R. "Fungus in the Library." Library and Archival Security, v. 4, no. 4 (1985), p. 35-55. Describes mold outbreaks at the Virginia State Library in 1978-1980.

Conservation Center for Art and Historic Artifacts. Managing a Mold Invasion: Guidelines for Disaster Response. Technical Series No. 1. Philadelphia, PA: Conservation Centerfor Art and Historic Artifacts, 1994.

Daniels, V. and B. Boyd. "The Yellowing of Thymol in the Display of Prints." Studies in Conservation, v. 31 (1986), p. 156-158.

Dawson, John. "Preventive Measures: Fumigation." In Proceedings of An Ounce of Prevention: A Symposium on Disaster Contingency Planning ..., March 7-8, 1985. Toronto, Ontario: Toronto Area Archivists Group, 1986, p. 54-63. Available from the Toronto Area Archivists Group, Education Foundation, P.O. Box 97, Station F, Toronto, Ontario M4Y 2L4, Canada. Also available from the Society of American Archivists.

"Deadly Fungus in Museum Basement Prompts Big Lawsuit" Abbey Newsletter, v. 18, no. 6 (Oct. 1994), p.68.

"Gamma Radiation." Abbey Newsletter, v. 8, no. 2 (April 1984), p. 25, 28.

"Gamma Radiation Approval Seen." Abbey Newsletter, v. 10, no. 1 (Feb. 1986), p. 12.

Gustafson, Dr. Ralph. Notes from a speech given 20 February 1987 at the South Carolina Library Association meeting of the Archives and Special Collections Roundtable, Columbia College, Columbia, South Carolina. Dr. Gustafson is a mycologist in the Biology Department at Winthrop College, and is working on a study of fungicides for library and archival material under a grant from the Council on Library Resources.

Haines, John H. and Stuart A. Kohler. "An Evaluation of Ortho-Phenyl Phenol as a Fungicidal Fumigant for Archives and Libraries." Journal of the American Institute for Conservation, v. 25 (1986), p. 49-55. Also, Mary-Lou Florian's letter to the editor in regard to the Haines-Kohler article, in JAIC, v. 25 (1986), p. 109.

Hanus, Jozef. "Gamma Radiation for Use in Archives and Libraries." Abbey Newsletter, v. 9, no. 2 (April 1985), p. 34.

Horáková, Hana and Frantisek Martinek. "Disinfection of Archive Documents by Ionizing Radiation." Restaurator, v. 6, no. 3-4 (1984), p. 205-216.

Kowalik, R. "Microbiodeterioration of Library Materials." Restaurator, v. 4, no. 2 (1980), p. 99-114; v. 4, no. 3-4 (1980), p. 135-219.

Kowalik, R. "Some Problems of Microbiological Deterioration of Paper." Annali della Scuola Speciale per Archivisti e Bibliotecari dell'Universita di Roma, Nuova Tecnica Grafica, v. 9, no. 1-2 (1972), p .61-80.

Lafontaine, Raymond H. Silica Gel. Technical Bulletin number 10. Ottawa, Canada: Canadian Conservation Institute, 1984.

McGiffin, Robert F., Jr. A Current Status Report on Fumigation in Museums and Historical Agencies. Technical Report 4. Nashville, TN: American Association for State and Local History, 1985.

"More About Gamma Rays." Abbey Newsletter, v. 8, no. 4 (July 1984), p. 53-54.

New York City Department of Health and Mental Hygiene, Bureau Of Environmental and Occupational Disease Epidemiology.  "Guidelines on Assessment and Remediation of Fungi in Indoor Environments", April 2000, January 2002.

Nyuksha, Yu.P. "Biodeterioration and Biostability of Library Materials." Restaurator, v. 4, no. 1 (1980), p. 71-77.

Parker, Thomas A. "Integrated Pest Management for Libraries." Unpublished article, from a presentation given at Osterreichische Nationalbibliotheck, Vienna, Austria, for the First Conference on Preservation of Library Materials, sponsored by the Conference of Directors of National Libraries in cooperation with IFLA and UNESCO, April 1986. Available from Dr. Parker at Pest Control Services, Inc., 14 E. Stratford Ave., Lansdowne, PA 19050(215-284-6249).

Preservation Office, Library of Congress. "Fact Sheet on Mildew and Mold." Distributed by the National Preservation Program Office, The Library of Congress, Washington, D.C. 20540.

Raven, Peter H., Ray F. Evert, and Helena Curtis. Biology of Plants, 2nd ed. New York: Worth Publishers, 1976.

Ritzenthaler, Mary Lynn. Archives and Manuscripts: Conservation. Basic Manual Series. Chicago: Society of American Archivists, 1983.

Roberts, Matt T. and Don Etherington. Bookbinding and the Conservation of Books: A Dictionary of Descriptive Terminology. Washington, D.C.: Library of Congress, 1982.

Smith, Richard. "Fumigation Dilemma: More Overkill or Common Sense?" New Library Scene, v. 3, no. 6 (Dec. 1984), p. 1, 5-6.

Thomson, Garry. The Museum Environment. 2nd ed. London: Butterworths (in conjunction with IIC), 1986.

Turner, Sandra. "Mold ... the Silent Enemy." New Library Scene, v. 4, no. 4 (Aug. 1985), p. 1, 6-8, 21. Article on the Denver Public Library Administrative Center mold outbreak in August 1984.

Wellheiser, Johanna G. Nonchemical Treatment Processes for Disinfestation of Insects and Fungi in Library Collections, IFLA Publications 60. Munchen: K.G. Saur, 1992.

Footnotes

1. See "Deadly Fungus..." in Abbey Newsletter, 1994.
2. Silica gel is a buffering substance, absorbing or releasing moisture into the environment to maintain a chosen level of relative humidity. It is frequently used in exhibit cases. See Lafontaine, Silica Gel, for procedures to condition and use silica gel.
3. Parker, "Integrated Pest Management for Libraries," p.21.

[Sandra Nyberg November 1987, SOLINET July 2003]

 

REVISED 7.11.2003

 


 

 

 

The Use of Gamma Rays in Book Conservation

by Patrick Sinco

Reprinted with permission from Nuclear News, April 2000, pp. 38-40.

The book conservation world has been wary of treating infested books and documents with radiation, but sometimes nothing works better.

Unlike its roles in medical sterilization or food disinfestation, gamma irradiation remains far from the frontline of treatments in the field of book conservation. Although it can be used for the same purpose—to kill mold and other fungi, as well as bacteria, in damaged documents—the practice of exposing valued papers to ionizing radiation is recommended only in certain, desperate circumstances. That said, irradiation is a young, promising, and relatively untested treatment in the preservation field—and as such is both scorned and lauded.

Intermittent studies performed over the past three decades have identified the damage that irradiation can impart to paper—or, more specifically, to cellulose, the chief component of paper. Although paper can be produced using anything from animal furs to metal, most paper is produced from cellulosic plant fibers, and principally those obtained from wood pulp, cotton, and linen. During irradiation, free radicals can be unleashed in the cellulose and quickly react with oxygen to break cellulose molecules and degrade the paper.

Irradiation's propensity for aging paper prematurely is borne out in a number of studies. A 1994 European study, led by Judith Hofenk de Graaff, compared the effects of gamma radiation and ethylene oxide (once a standard for treating mold-infested materials) on the aging of paper. The chemical and physical properties—such as folding endurance, internal tearing resistance, stiffness, and pH level—were measured on five different kinds of papers following treatment, both before and after the paper was artificially aged. A 10 kilogray (1 megarad) dose accelerated the aging process in the irradiated papers by 50 to 100 percent, depending on the paper, according to the study, while the EtO treatment did not affect the aging of the paper. A 1998 study that appeared in the German journal Restaurator described the effects of increased doses of gamma rays on cellulose paper, both before and after accelerated aging. The radiation treatment decreased polymerization in the paper and caused it to turn yellow. A pair of studies that appeared in the March and June 1999 issues of the Taiwan Journal of Forest Science revealed a decrease of up to 15 percent in the mechanical properties of the papers tested at low to medium levels of irradiation, while at high doses the papers showed significant decreases in brightness and increases in yellowness.

So much for irradiation in book conservation?

In a field that strives to preserve materials, a treatment that may incidentally degrade materials can also greatly contribute. A slightly yellowed or embrittled document can be tolerated when the alternative is no document at all.

"Radiation has a place, if only because all the alternatives have their drawbacks," said Ellen McCrady, who edits the Abbey Newsletter, which has been tracking the field of library and archival materials preservation for 25 years. "[Conservators] know the irradiation degrades paper and parchment, but . . . the mold and insects will also continue to degrade the materials if they are not killed."

"I think [irradiation] needs some open minds," said Dennis Allsopp, a retired microbiologist and current U.K.-based consultant who specializes in work for libraries, museums, and archives. "There has been work done by the conservation world where, because someone said, 'Well, we think that this actually causes a little bit of damage,' people have written it off and said, 'Oh, we can't have anything that causes damage.'

"Well, of course, any treatment—handling a book, fumigating it—will probably cause some sort of damage. If you want to be a total purist, you can just sit and watch the thing rot and weep over it."

The Gantt Papers

The pilot project in the United States on the use of irradiation to disinfest archival materials began in 1980 when the medical archives of Johns Hopkins University inherited a collection of documents from a public health officer named W. Horsley Gantt. The materials, however, had been stored in a dilapidated row house in Baltimore that was infested with insects, rodents, and dog and cat carcasses. When a team of archivists first showed up at the house, "things were strewn about—it was in total disorder," Nancy McCall, an archivist at the JHU Alan M. Chesney Medical Archives in Baltimore who led the effort to preserve the Gantt collection, recalled recently. But what they found littered among the rubbish (which also included stray car fenders and giant balls of string) made clear that they would need to discover a way to preserve the collection.

Dr. Gantt lived in Petrograd, Russia, in the years following the Revolution in 1917. He had collected valuable public health documentation, such as letters, photographs, and diaries, as well as rare public health posters from pre-Revolution Petrograd—all of which were found in the row house. Gantt's correspondence with psychologist B.F. Skinner and author John Dos Passos were also found. Most notably, Gantt's papers and letters from Russian physiologist Ivan Pavlov were stored in the row house; Gantt was the only American to study with Pavlov.

"Since it was a very valuable collection, we felt it was important to make a very concerted effort to save the material, to clean it up," McCall explained. (McCall was familiar with valuable collections, having served as a volunteer during the devastating flood of the Arno River in Florence in November 1966. The angeli del fango—or "mud angels," as they were called—were students and conservators from around the world who came to rescue invaluable centuries-old paintings and manuscripts from the flood waters.)

McCall and her colleagues at JHU began to contact large archival programs, like state archives, that had larger treatment facilities. "We were very up front about what the problems were, and that just scared people. They didn't even want their loading docks contaminated," McCall said.

McCall had heard of using ionizing radiation for disinfestation, but didn't know much about it. After a search through the literature, she found mention of its use in eastern Europe to treat artifacts—and little else. "A lot of conservators with whom I spoke thought it was high risk. But we felt that we had no alternative but to take that risk." She then contacted Walter Chappas, who was a nuclear engineer at the University of Maryland at the time (and is now vice president and technical director for Damilic Corporation, in Rockville, Md.), to do preliminary test samples. Chappas performed tests using a linear accelerator to establish dosage level and exposure time so that the extermination process would be effective and minimize damage to paper and ink composition.

"When you're asked to take thousands of books that may have been published over 100 years, with different materials, different adhesives, different printing inks," Chappas said, "the legitimate engineer has to ask himself, 'We may kill all the bacteria, but are we also going to damage these materials in the process?'"

After working out a plan with a commercial radiation facility, McCall and her fellow archivists lined Paige boxes with plastic garbage bags, packed in the papers, and sealed the boxes. In all, 295 record storage boxes of Gantt's papers were exposed to 4.5 kGy (0.45 Mrad) of gamma radiation from a cobalt-60 source for approximately 45 minutes. Afterward, 10 cultures produced from a broad sampling of the irradiated materials revealed only one minor and incidental strain of mold, which was most likely introduced when the materials were unpacked.

"We had absolutely no problems—nothing," McCall said, and mentioned that there have been no problems with the documents in the nearly 20 years since the materials were placed in the Chesney Archives. "We were severely criticized at the time by very conservative conservators," McCall said. "But, truly, there has not been one conservation problem."

"We never want to suggest that this is the magic wand," Chappas explained, "and that you can take these heavily infested manuscripts and other documents, send it through the irradiation vault, and out the other side comes this pristine document that's clean and stable. The fact is there's potential for problems.

"But, the good news here was that we took samples that would otherwise have been lost. We did this technique and it not only solved the immediate problem—killing all the bacteria [and other contaminants]—but, in fact, did it in a way where the long-term damage has been apparently immeasurable at this point."

Misconceptions

The reputation of irradiation certainly suffers the same problems among book conservators as it does most everywhere else. Namely, people fear all things "radiation." Some people in the conservation field quickly dismissed the technology when asked about its role in the preservation of books, as if it were useless to discuss.

"There is the psychological point that everybody gets so scared if they hear the word 'radiation,'" said Bert Van Zelst, director of the Smithsonian Institution's Center for Materials Research and Education. "That's the usual thing everywhere. But it is effective. There's no doubt that it's effective."

If only for control of insect pests in books, using much lower doses—0.5 kGy (0.05 Mrad)—than required for mold disinfestation, irradiation does have an unassailable role to play in book conservation. Looking at a higher dose level, a 1992 study published in the German journal Restauro described the minimal optical and mechanical effects on mold-infested historic books at the Leipzig University Library when given 12 kGy of gamma radiation, and noted that "severely attacked historical books showed improved quality after having undergone the described treatment."

"One of the problems is the scientific world and the art world—the conservation world—have often found difficulty in getting together," Allsopp said, "for reasons that people in them come from very different disciplines and are trained in different ways and mix socially in different ways."

Others expressed concerns about gamma radiation that appear to result from hearsay rather than fact. A few mentioned the difficulty, if not implausibility, of convincing a food or medical irradiation facility to accept their dirty books. Ruth Garcia, a plant operations manager for Isomedix, which operates 15 irradiation facilities in the United States and Canada, said they readily accept infested books, provided a number of measures are taken to package the material to isolate the contamination.

Still others—even those in advanced positions at elite institutions—have more troubling misconceptions. The comments of a senior scientist at one of the world's leading conservation institutes—who admitted irradiation was not his specialty but goodnaturedly responded to a few questions—are telling. In enumerating some of the disadvantages of gamma irradiation, he noted "You have to have a reactor," which certainly would present an obstacle if it were true.

He also said that irradiation is not needed in book conservation: "You just keep the books dry and you have no problem."

Disaster Recovery

The only thing unusual about the late Sunday afternoon storm a few years ago that burst over the college town of Fort Collins, Colo., located about an hour's drive north of Denver, was the storm itself. The summer had been unusually arid, with rainfalls totaling less than half an inch for the region since the middle of June. Even as low, dark clouds lingered in the foothills of the Rocky Mountains after the storm ended—instead of clearing after dark in accord with normal summer weather patterns—there was little indication that the evening storm would be but a prelude to the most intense rainfall the region had ever seen.

The clouds released a steady torrent of rain through the night, and area residents awoke to a cool, gloomy Monday morning. By midday, curiosity turned to concern as continued rains led to accumulations of between 2 and 10 inches in locations in and near Fort Collins since the previous afternoon. The creeks and ditches were running full.

As flooding began to be reported in a nearby town, the rains had abated across the region in the afternoon. The air, however, remained unusually humid. Showers again erupted, and by 8:30 p.m., after two hours of heavy rains, the rains diminished in the east and southeast areas of Fort Collins.

The next hour-and-a-half, however, brought accumulations of rain over western portions of the city the likes of which had never before been recorded. Since hourly data were first published in 1940, the campus of Colorado State University had never experienced as much rain in a similar period as the 5.3 inches that fell between 6 p.m. and 10:30 p.m. on that Monday, July 28, 1997. Flood waters roiled through campus, and by morning there would be 10 feet of water in the basement of the main library.

"It's bad. It's a real mess," Camila Alire, CSU dean of libraries, was quoted at the time in The Coloradoan. "But the books are salvageable."

Mold can begin to form on a wet book within hours. Once it has bloomed on an item, it will reappear whenever favorable environmental conditions, such as high temperatures and high humidity, allow. As such, mold can never be eradicated unless it is killed.

Chemical treatments to kill molds in library collections are currently discouraged because of their toxicity. Indeed, exposure limits of ethylene oxide have been regulated to the extent that EtO—once a mainstay for mold control—is no longer a viable treatment option, according to Mark Gilberg, a research coordinator at the National Center for Preservation Technology and Training. "For me, many years it was ethylene oxide," Gilberg said. "But the exposure limits got to the point where they were so low that it was almost impossible to carry out."

"Ethylene oxide is the main alternative to radiation," Ellen McCrady stated, "but we know now that it is very hard to get back out of certain materials . . . no matter how many times the air is purged while they are in the chamber. . . . The EtO that remains will eventually escape from the book or document and endanger staff and readers."

Photograph

Flood ruin: The scene in the library basement was bleak soon after the nearly 5 million gallons of water were pumped out. The 1997 flood damaged 462,500 books, journals, and periodicals (Photos: Colorado State University)

Other accepted treatments, such as freezing or placing the materials in a low-oxygen environment, can be effective in limiting the growth of molds. They do not kill the mold, but send them into a dormant state. A cool, dry environment with plenty of air circulation must still be maintained in the room where the collection is stored to prevent an outbreak recurrence.

"Mold can be a very big problem depending on where you are in the United States," Gilberg said. "It's a big problem here, down south. . . . Mold develops. And you have to react quickly."

Within days of the Colorado University flood, work crews began the task of removing nearly 500 000 books, periodicals, and journals from the library. Two weeks later nearly all the books were wrapped individually and placed into approximately 60,000 boxes. They were then shipped on a refrigerated truck to a freezer storage facility in Wyoming.

 Pulled from the wreckage: When the floodwater was finally pumped out of the basement of the main library at Colorado State University, library officials were faced with restoring damaged books such as these [Photo not published in Nuclear News]

Meanwhile, the library was sending samples of damaged books across campus to a microbiologist, who then tested different treatments. "We were trying to find the easiest, safest, and fastest way to clean and sterilize the books," said Doug Rice, director of CSU's Environmental Quality Laboratory, who performed the studies. "We tried several chemical methods, wet methods, cleaning methods. We tried ozonation. And we tried cobalt-60 gamma irradiation."

"We consulted with the Library of Congress," remembers Carmel Bush, the library's assistant dean for technical services. "We talked to people about what was best to do. We also had independent physical chemistry consultants. We had a number of points of view."

According to results published in a forthcoming book about the library's recovery effort, gamma radiation achieved a 100 percent reduction in mold and yeast in Rice's book samples. The next closest reduction was 56.4 percent.

"We thought our experience and testing showed [irradiation] would work," Bush said. "And, because we were controlling it in the low-dosage levels, we did not expect any of the problems that could be reported in higher doses. . . . That led us to feel that it was a good treatment choice."

A query about irradiation posted on an Internet mailing list by a worker from one of the library's recovery subcontractors was answered by a SteriGenics International employee, and a plan to irradiate nearly half-a-million books at the company's Co-60 facility in Fort Worth, Texas, was begun.

The books were taken out of cold storage and thawed. The covers were removed and the pages were washed and shaped into a block. The books were then freeze-dried before being shipped to the irradiation facility in Fort Worth, where they were given an average dose of around 15 kGy (1.5 Mrad). After irradiation, the books were further cleaned and inspected by another recovery subcontractor in Fort Collins. They were sent for rebinding, and then carefully again inspected and repatriated into the library's collection.

The process, however, is far from finished. Bill Parkin, of Belfor USA (formerly Disaster Recovery Services)—CSU's Fort Worth-based subcontractor—estimates that 100,000 volumes yet remain.

"We're still in the process, so we haven't engaged in any longitudinal testing," Bush said when asked about the irradiation's noticeable effect on any books. "But we really don't expect that there's going to be any long-term effects. Our belief is, they are as they are, and we don't see anything relating to the radiation. I think if we had used high-dosage irradiation, we'd be talking about a different story, but we're not. . . .

"Mainly what [effects on the paper] we see is damage from being underwater. The paper suffers from wrinkling, it suffers from discoloration . . . You will see the stains where the mold was. But, obviously, we have no active mold in it—it's completely dead. We're real pleased about that."

Coming of Age?

For now, gamma irradiation in the preservation of books and archival materials has been most successful in emergency circumstances. Although the two examples provided are the only two well-known instances in the United States in which irradiation was used to disinfest books on a large scale, Mark Smith, director of technical services for SteriGenics International, indicated that his company has done similar work on collections of flood-damaged books. He also mentioned that it is preparing to irradiate some damaged internal documents of a major petroleum refiner.

"The trouble is, with a lot of this sort of commercial work, people don't shout it from the rooftops," said Dennis Allsopp, who was once president of the International Biodeterioration Society. "This is one of the problems with biological attack on materials—it's like people don't normally publicize their illnesses. People don't often make a big point that they've had a problem in their factory. They have it cured and solved, if they can, and they're just happy that they've solved the problem."

Allsopp mentioned that it was during the Florence flood when a largely experimental technique—now widely used—was attempted out of necessity. "At the time . . . keeping things cold and freezing was thought to be terribly adventurous, but it had to be done because they just had tons of material which would have gone rotten otherwise. And it worked."


Copyright 2004 Abbey Publications, Inc. All rights reserved.




Combating Mold and Dry Cleaning

We act before your books turn black - fast and effective.

Mold infestation, which is not combated in a timely manner, deteriorates paper severely, which then loses its mechanical stability. The book can become unusable and costly conservation measures are essential.

Mold spores can be found practically everywhere. They begin to grow and develop as soon as they meet with favorable conditions. High humidity and temperatures are favorable conditions for mold. Due to its allergenic properties, mold is also a health hazard for anyone who comes into contact with it.

Paper and the adhesives found in the bindings are an ideal breeding ground for microbes. Mold which is not treated immediately can lead to a loss of the entire object. Within days mold can spread from individual spots on a single sheet to the whole bulk.

In order to combat mold effectively, we first isolate the infested objects from stocks which are not effected. Small-scale surface mold is treated with alcohol. The treatment with alcohol disinfects the effected areas. If mold has already infested an entire book, we irradiate the mold with low-dosed gamma rays. This radiation sterilizes the mold spores.

However, gamma-ray irradiation has no effect on the allergenic effects of mold spores. In addition, deadened mold is also an ideal breeding ground for a new infestation. After irradiation we remove the surface deposits of mold as well as any other dirt. We clean the book under all necessary protective measures. If required, we do this to each page individually.

Severe mold damages the structure of the infested books and documents. After combating mold we are also more than happy to take on any further required conservation work for you!

A subsequent dry-cleaning treatment, in which mold residue is removed, concludes mold-combating treatment.

 
 
 
 


 

Susceptibility of cellulose to attack by cellulolytic microfungi after gamma irradiation and ageing
Titre de la Revue : Restaurator. [ Restaurator. ] , 2003 , vol. 24 , no 3 , pp. 145 - 151 [ 7 pages. ]
    ADAMO M. , MAGAUDDA G. , TRIONFETTI NISINI P. , TRONELLI G.
ENEA C.R. Casaccia, Via Anguillarese 301
Type de document : PERIODIQUE Langue : anglais
Cote INIST : 5546
Editeur :
Résumé : Dans le cadre de travaux de recherche de grande envergure visant à décontaminer les livres et documents stockés dans les bibliothèques et les archives, cet article décrit l'effet de différents dosages de rayons gamma sur le développement d'un champignon responsable de la détérioration du papier (Penecillium chrysogenum Thom.), sur la cellulose du papier (Whatman). L'irradiation a été effectuée à l'aide d'une lampe Co-60. Après l'irradiation les échantillons placés dans un milieu nutritif solide ne contenant pas de carbone ont été inoculés par des spores de P. chrysogenum. Après une incubation à 25°C pendant 7 jours des mesures ont été effectuées pour déterminer l'étendue de la croissance fongique en évaluant la teneur en ergostérol. Les résultats démontrent qu'une forte irradiation aux rayons gamma induit certaines altérations de la macromolécule de cellulose qui influence le développement du champignon responsable de la détérioration du papier. Ce phénomène, particulièrement évident à fortes doses(100 et 200 kGy), reste négligeable lorsque l'irradiation est maintenue à de faibles doses (<10kGy) qui sont adaptées à une application pratique de la technologie d'irrradiation pour la décontamination du papier.

 

 


 

interaction of radiation with matter - half value thickness - attenuation - shielding

What it shows:
The interactions of the various radiations with matter are unique and determine their penetrability through matter and, consequently, the type and amount of shielding needed for radiation protection. Being electrically neutral, the interaction of gamma rays with matter is a statistical process and depends on the nature of the absorber as well as the energy of the gamma. There is always a finite probability for a gamma to penetrate a given thickness of absorbing material and so, unlike the charged particulate radiations which have a maximum range in the absorber where all are stopped regardless of source strength, some gammas will always get through and, given a strong enough source, a lot may get through.

How it works:
The radionuclides and detectors are described in Sources and Detection. The present demonstration is usually performed in conjunction with that demo.

(1) Alpha particles interact with matter primarily through coulomb forces between their positive charge and the negative charge of the atomic electrons within the absorber. The range of alphas of a given energy is a fairly unique quantity in a specific absorber material. 1   For a given energy, alpha particles are much slower than beta particles, giving rise to greater impulses. Additionally, its double charge (+2e) makes an alpha particle have a very high rate of energy loss in matter thus making it heavily ionizing radiation. Consequently, the penetration depth of alpha particles is very small compared to the other radiations. For low density materials, the range 2   of 5.5 MeV alphas (from Am-241) is between 4.5 - 5 mg/cm2; higher density materials give a range between 5 and 12 mg/cm2. The table below gives some specific values.

absorber density alpha range comments
air (STP) 1.2 mg/cm3 3.7 cm
paper (20lb) 0.89 g/cm3 53 µm one sheet = 89 µm
water (soft tissue) 1.0 g/cm3 45 µm will not penetrate skin

The thickness of a single sheet of paper (0.0035") is enough to stop all the alphas. 3

(2) Beta particles also interact through coulomb forces with the atomic electrons. By virtue of their small mass, betas have much higher speeds and smaller impulses are involved in the collisions. Their penetration into matter is thus considerably greater than alphas but, because of the nature of the Coulomb force interactions, betas too are stopped by very little matter (compared to gammas). Because their masses are identical (to the scattering electrons), large deviations in the beta particle path are possible and even thin absorbers will attenuate betas by virtue of the fact that they readily get scattered out of the direct beam. Another difference that complicates the comparison is that, unlike monoenergetic alphas, beta particles come in a continuous spectrum of energies, with the average energy being about 1/3 the maximum. The low energy betas are rapidly attenuated.

A useful rule-of-thumb for the maximum range of electrons is that the range (in gm/cm2) is half the maximum energy (in Mev). 4   This is of course complicated by the density: electron ranges tend to be about 2 mm per MeV in low-density materials, and about 1 mm per MeV in medium density absorbers. For our Sr/Y-90 source (maximum beta energy = 2.27 MeV, average energy = 1.13 MeV), more precise beta ranges are tabulated below:

absorber material density maximum beta range5
    (2.3 MeV) (1.1 MeV)
air 1.2 mg/cm3 8.8 m 3.8 m
water (soft tissue) 1.0 g/cm3 11 mm 4.6 mm
plastic (acrylic) 1.2 9.6 4.0
glass (Pyrex) 2.2 5.6 2.2
aluminum 2.7 4.2 2.0
copper 8.9 1.2 0.5
lead 11.3 1.0 0.4

(3) Gamma ray interactions with matter are entirely different from that of charged particles. The lack of charge eliminates coulomb interactions and allows gamma rays to be much more penetrating. The interactions that do occur are by way of the photoelectric effect, Compton scattering, and pair production. The probability for any of these happening is specified by a cross section and the linear attenuation coefficients for gamma rays are defined by these cross sections. Since linear attenuation coefficients vary with the density of the absorber, even for the same absorber material, the mass attenuation coefficient (linear attenuation coefficient divided by the density) is more useful and the attenuation law is written as

I = Ioe-(µ/ñ)ñt

The product ñt is the significant parameter and the units (as with â and á) are mg/cm2. Unlike charged particles, a certain percentage of gammas will always make it through the absorber and it is useful to consider the half-value thickness of a given absorbing material for the gamma ray energies of interest. The half-value thicknesses are determined from the equation using the linear attenuation or mass attenuation coefficients found in the references below. Absorbers of these thicknesses attenuate the radiation reaching the detector by a factor of two and some of the common ones are tabulated below for Co-60 (1.33 and 1.17 MeV) and Cs-137 (662 keV).

Setting it up:
Plastic, aluminum, steel, lead, and many other absorbers are available as needed. They range in thicknesses from hundreds of microns (foils) to several centimeters. The absorber is simply placed over the thin end-window of the GM tube.

Comments:
One doesn't really want to turn a simple demonstration into a lengthy laboratory exercise, so it's best to decide beforehand the salient features one wants to impress on the audience and use the appropriate absorbers and thicknesses to make the point. Rating ***

References:
G.F. Knoll, Radiation Detection and Measurement, 2nd ed, (Wiley, NY, 1989)
G.W. Morgan, Some Practical Considerations in Radiation Shielding, Isotopes Division Circular B-4, (U.S. Atomic Energy Commission, Oak Ridge)
CRC Handbook of Radioactive Nuclides, edited by Y. Wang, (Chemical Rubber Company, Ohio, 1969)
A.H. Wapstra, G.J. Nijgh, and R. Van Lieshout, Nuclear Spectroscopy Tables, (North Holland, Amsterdam, 1959)
X-ray Attenuation Coefficients from 10 keV to 100 MeV, National Bureau of Standards Circular No. 583

1 Indeed, in the early days of radiation measurement, alpha particle energies were measured indirectly by determining the absorber thickness equivalent to their mean range.
2 The range is expressed in terms of (density)×(thickness), which is written as the mass/unit area of the absorber of a given thickness. Historically the units have been mg/cm2. Density·thickness (also sometimes referred to as mass·thickness) is a useful concept when discussing the energy loss of alphas and betas because, for absorber materials with similar neutron/proton ratios, a particle will encounter about the same number of electrons passing through absorbers of equal density·thickness. Therefore the stopping power and range, when expressed in these units, are roughly the same for materials that do not differ greatly in Z.
3 The paper weighs 4.77 gm/sheet which gives it a density of 0.89 gm/cm3 and a density·thickness of 7.9 mg/cm2
4 This rule of thumb is applicable only when E > 0.8 MeV. For other energy ranges, see Wang, p 912.
5 Values are from Y. Wang (reference). Another rule-of-thumb is that the half-value range is approximately 1/7 of the maximum range but may vary between 1/5 and 1/10 (depending on beta energy and absorber density).


 

 

copper number

A number expressing the amount of copper reduced from the cupric to the cuprous state by a given amount of cellulosic material. It is useful as a measure of purity, particularly in relation to the strength and resistance to chemical degradation of paper and board. The copper number gives the degraded celluloses, and particularly those that result from bleaching. Although the copper number test is subject to reservations, it is generally agreed that a lower copper number enhances the chances of longevity of the paper. The test does not, however, apply to lignified fibers, and must be corrected for noncellulosic constituents. (72 , 143 )

 

This method describes a procedure for determining the copper number of bleached and purified pulp, paper, and paperboard, except those containing calcium sulfite, zinc sulfide, melamine resin, or other copper-reducing nonfibrous materials. Papers containing such additives can be tested only if the amount and reducing power of the added material is known.

It has been well established that hydrolyzed or oxidized cellulose is capable of reducing certain metallic ions to lower valence states, and reactions of this type have served to detect damage to cellulose and to estimate the quantity of reducing groups.

The copper number may be regarded as an index of those impurities in paper, such as oxycellulose, hydrocellulose, lignin, and sugars, which possess reducing properties. It is useful for determining changes accompanying deterioration and may therefore be considered as a factor having an indirect bearing on the permanence of paper. It should not be applied to papers containing mechanical pulp or unbleached chemical pulp.

 

Em física, uma forma de ionização é produzida pelas radiações ionizantes que tranferem energia suficiente para separar um elétron de seu átomo. A ionização é, portanto, a formação de um par de íons, o negativo ( elétron livre ) e o positivo ( o átomo sem um de seus elétrons ).

 



In generale è ben riconosciuto l'effetto deleterio dei raggi gamma che depolimerizzano la cellulosa. Tuttavia le ultime ricerche aprono interessanti prospettive in quanto sarebbe possibile operare utilizzando intensità inferiori di radiazioni garantendo l'efficienza del trattamento con meno danni per la carta. I dubbi comunque permangono anche perché esistono trattamenti con atmosfere controllate, più lenti ma decisaamente più sicuri per materiali e operatori.
Ecco qualche titolo.
G. Magaudda, A. Adamo, F. Rocchetti, Damage caused by destructive insects to cellulose previously subiected to gamma ray irradiation and artificial aging, in «Restaurator», 22 (2001), n. 4, pp. 242-250

ADAMO A. M. ; GIOVANNOTTI M.; MAGAUDDA G.; ZAPPALA M. P.; ROCCHETTI F.; ROSSI G.; Effect of gamma rays on pure cellulose paper : as a model for the study of a treatment of biological recovery of biodeteriorated books, in:
Restaurator 1998, vol. 19, n.1, pp. 41-59


The Potential Long-Term Effects of Gamma Irradiation on Paper
Fiona J. Butterfield
Studies in Conservation, Vol. 32, No. 4 (Nov., 1987), pp. 181-191

 

 
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