However, some types of nastiness can't be cleaned. One example is book mold.
"One of the most common problems in libraries and archives... is mold.... Mold grows through the propagation of its spores, which are always present in the air waiting for the right opportunity to germinate. Moisture provides the necessary conditions for mold germination.... Mold spores can be dangerous, and the treatment of mold-infected material must be handled with care to avoid inhalation. Although not all molds are toxic to humans, it is important to regard all infestations as possibly toxic and take the appropriate precautions (respirator and gloves) when entering an infested area.... Mold can grow on any moist surface, including materials such as paper, leather, and book coverings, causing disfiguring, multicolored stains and greatly reducing the material's strength" (http://www.librarypreservation.org/management_and_planning/mold.htm)
We have to be really careful when we come across these books at the library, because some of our staff are highly allergic to book mold. So please be careful this summer as you enjoy all the water activities the Missoula area has to offer, and keep your books dry!