Based on my readings, most people would argue that the best defense against molds and pests, should be prevention or common sense environmental measures. Although accidents and disasters beyond one's control can and do occur, some situations may be avoided.
Prevention
For the most part, the same practices are effective to prevent outbreaks of both pests and mold. The following discussion about control of molds should be applicable to pest control. Additional measures for pests follow.
Ideally, the most important practice to prevent the growth of mold is to maintain an environment where the growth of mold is not stimulated. Nyberg emphasizes that controlling environmental factors such as air temperature and humidity is the only permanent method of keeping mold in check. Books absorb moisture and the presence of moisture is conducive for mold to feed off the nutrients in books. According to Nyberg, the air temperature should be maintained at a range of 65°- 70° with a relative humidity within 45% to 65%. Temperature below freezing will cause mold to become dormant. While high temperatures will arrest mold, it may also cause damage to books.
Sufficient air circulation is another aid in the prevention of mold growth. Nyberg points out that a well-function heating and air conditioning system, can keep humidity, air temperature and circulation at appropriate levels. Since fluctuations are undesirable, regular monitoring is another recommended precaution.
It may be interesting to note that both the presence of sunlight or ultra-violet radiation may support the control of molds. But, according to studies on the deterioration of paper, exposure to sunlight and ultra-radiation may lead to the increased acidity of paper, a major cause of deterioration.
Certainly with insects, the safest and simplest approach is maintain regular housekeeping procedures by controlling food on the premises, removing garbage and keeping floors clean. Other steps may include: sealing cracks and caulking to prevent access; sealing windows and doors with proper gaskets and screens; preventing water leakage or unwanted moisture; maintaining low humidity; using exterior lighting that inhibit insects (i.e. sodium vapor).
For the control of insects and other pests, the Chicora Foundation also recommends that an institution create a comprehensive pest management program. I believe that the need to undergo such a formal process should be related to the magnitude of the pest problem. The following are the features of this approach:
How to Handle Disasters or Crisis Situations
Until I had completed the readings about mold damage and pests, I had never given any thought to the degree of devastation that such organisms could cause if left unchecked. Even a stable environment could turn into a disaster scene for books when humidity and the air temperature inside reach extreme levels.
The crisis involving the presence of mold at the off-site storage center for Denver Public Library in 1984 so glaringly demonstrates how even a malfunctioning air cooling system could quickly upset the delicate balance between heat and humidity. So, even in an arid environment such as Denver, Colorado, it was possible to witness the rapid spread of mold spores through the shelves of vulnerable books.
With more knowledge and concern about the toxicity of chemicals and increased concern about indoor air pollution, the use of chemicals should be the approach of last resort. Chemicals such as phenols (i.e. thymol) and ethylene oxide are known to be toxic. Exposure to ethylene oxide has been linked to a variety of cancers while exposure to thymol may cause kidney and liver damage (Nyberg). So, care should be taken to select an experienced fumigator, who is knowledgeable in the organisms to be removed. The institution should obtain documentation about the chemical concentration to be applied. In addition, the institution should limit the number of applications so that exposure to chemicals is minimized.
The literature about molds and insects suggests alternatives that are appear to be more conservative and therefore much less toxic than the application of chemicals. Based on my readings, it appears that the same treatments may be applicable to the control of both molds and insects.
For the control of pests, the National Forest Service, utilizes a freezing process (Conserve a Gram). Freezing should not be undertaken on a regular basis but only when pests are present. Dry articles made of leather, wood, textiles and paper are suitable materials. Freezing can be accomplished in an ordinary freezer (but not self-defrosting) as long as the temperature remains would be stable at less than -20°C. Two freezing cycles are conducted separated by a warming period. Provided that the appropriate steps are taken to prevent the presence of moisture, this approach seems safe and effective.
According to the National Forest Service, the presence of moisture can cause swelling or shrinkage. High levels of moisture can cause further damage such as rotting, corrosion and a resurgence of pests. According to the Chicora Foundation, the temperature must be lowered quickly otherwise the insects will simply become dormant and not completely eradicated. According to the Forest Service, materials that are wet, are not suitable candidates for the freezing process.
Nyberg suggest that before mold is treated, one should determine if the mold is active or inactive. Active molds appear wet, slimy and may be colored whereas inactive mold is dry and powdery.
When treating moldy items, one should segregate them from the rest of the collection by either placing them in sealed bags or closing off the infested area. Then the humidity, air temperature, and circulation should be checked and regulated. The air conditioning and heating system should be inspected for any malfunction. It is also important to be sure no water is present or leaking from pipes, roofs, etc.
According to Nyberg, when freezing is used to control mold, it serves as a fungistatic rather than a fungicial treatment. In other words, it will arrest the growth of spores but will not kill them. However, freezing is a suitable strategy to employ before cleaning.
Once the growth of molds has been arrested, the cleaning of books and paper can be accomplished with the use of a vacuum. Nyberg states that when ordinary household vacuums are used, the cleaning procedure should be done outdoors since, the filters of these machines will direct the mold spores back into the air. Alternatively, she recommends an industrial strength wet-dry vacuum filled with a diluted mixture of a fungi side such as Lysol. I would think that cleaning with a vacuum would be suitable approach for insects as well. According to the University of Oklahoma, vacuuming decreases the amount of spores but does not kill mold spores. It is also labor intensive.
In the mid-80's, a couple of articles appeared in the Abbey Newsletter about the application of gamma radiation to eradicate mold (Abby Newsletter). This approach was copied from the food industry that developed this food preservation technique. Since ionizing radiation kills insects, bacteria and other micro-organisms, why not apply it on books? Nyberg indicates that although it kills mold and does not have any residual impact, it may soften leather and adhesives. In addition, it also can weaken the strength of paper and decreases its ability to withstand repeated folding. Also special chambers are required for this procedure.
It appears that the most promising method of controlling mold may be the use of chlorine dioxide (Weaver-Meyers). The library at the University of Oklahoma conducted an eight-year study using this chemical. Often confused with chlorine bleach (hypochlorite), chlorine dioxide is considered an acceptable treatment of water by the E.P.A. and has been used as a disinfectant for a long time. They claim that it is more powerful than ethylene oxide but has not been compared to phenols such as Lysol. However, it does not appear that any other studies have been done using this chemical in libraries.
The University of Oklahoma has been using chlorine dioxide to wipe down moldy books since 1991 (Weaver-Meyers). They began to use it after the outbreak of mold following some extensive roof damage. Chlorine dioxide was recommended as a relatively safe treatment for workers to use. They applied the chemical with a hand-held fogger and also used it to wipe down moldy books. Later on, they began to use self- activating gas packets instead of fogging. The gas packets require fewer staff hours, the relative humidity is more stable and the floors and material do not become wet.
It appears that exposure to chlorine dioxide is considered relatively safe according to studies conducted by the EP A. In addition, OSHA has not sited any mutagenic effects resulting from exposure to this chemical. However, further study on the long term impact of chlorine dioxide may be needed. Although they have not detected visible damage to their collections, they have not studied the impact on long term deterioration of the paper.
Conclusion
Prudent measures to prevent outbreaks should be employed but one should also have a well-designed disaster plan to handle the unexpected. In that way, steps to correct the condition and salvage collections can be conducted in an efficient manner.
References
Nyberg, Sandra. Invasion of the Giant Mold Spore. http://palimpsest.stanford.edu/byauth/nyberg/spore.html
Turner, Sandra. Mold...the Silent Enemy. The New Library Scene. August 1985. 1,6- 8,21.
Abbey Newsletter. Gamma Radiation Approval Seen. 10(1). February 1986.
Abbey newsletter. Gamma Radiation. 8(2). April 1984.
Conserve 0 Gram. An Insect Pest Control Procedure: The Freezing Process. 3/6. July 1994.
Chicora Foundation. Managing Pests in Your Collections. 1994. http://palimpsest.stanford.edu/byorg/ chicora/ chicpest.html
Weaver-Meyers, P.L., Stolt, W.A., Kowalseski, B. Controling Mold on Library Materials with Chlorine Dioxide: an eight-year case study. The Journal of Academic Librarianship. 24(6), November 1998. 455-8. [Wilson Select] http://firstsearch.org.
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