Mothballs are small balls of chemical pesticide and deodorant used when storing clothing and other articles susceptible to damage from mold or moth larvae (especially clothes moths like Tineola bisselliella).
Their use when clothing is stored out-of-season gave rise to the colloquial usage of the terms "mothballed" and "put into mothballs" to refer to anything which is put into storage or whose operation is suspended.
Composition and safety 
Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, modern mothballs instead use 1,4-dichlorobenzene (also called para-dichlorobenzene, p-dichlorobenzene, pDCB, or PDB). Both of these ingredients have a strong, pungent, sickly-sweet odor often associated strongly with mothballs. 1,4-Dichlorobenzene and naphthalene should not be mixed, as they react chemically to produce a liquid which may cause damage to items being preserved. Camphor, an insect repellent, can also be used as a less-toxic ingredient in mothballs.
Both naphthalene and 1,4-dichlorobenzene sublimate, meaning that they evaporate from a solid state directly into a gas; this gas is toxic to moths and moth larvae.
For either of these insecticidal chemicals to be effective, they need to be placed with the clothing in a sealed container so the vapors can build up and kill the moths. In a sealed atmosphere like this, the vapors are not as harmful to people because they are relatively contained. The main exposures would occur when filling or opening the containers, or from wearing clothes immediately after opening (especially a problem for infants). A possible solution is to open the containers outside and let the clothes hang and air out for a day before wearing, though this practice will also expose the clothes to any moths that may be flying about, risking re-infestation.
Uses and risks 
A major concern about the use of mothballs as a snake, mouse, or animal repellent or poison is their easy access to children, pets, and beneficial animals. Leaving them in a garden or in a living space unprotected makes it very easy for unintended victims such as children and pets to gain access to them. Mothballs are highly toxic when ingested (they have a sweet taste, making this more likely), and will cause serious illness or death. In addition to this, using a large quantity of mothballs in a basement or a living space may cause serious respiratory problems in people living in the space.
Mothballs have been promoted as a squirrel repellent, and are an ingredient in some commercial repellent products. They are generally ineffective, and are no substitute for physical measures to exclude squirrels from building interiors.
Mothballs are a neurotoxin - especially those made of para-dichlorobenzene - and need to be treated as such. Mothballs have also been found to be carcinogenic. Mothballs have been used for solvent abuse, causing a variety of neurotoxic effects.
Older-formula mothballs have also been used by drag racers to enhance the octane value of fuel by dissolving the mothballs in some of the fuel and filtering out the remains with a filter paper. In the Mythbusters episode "Scuba Diver, Car Capers", it was shown to be "plausible" that adding mothballs to a car's fuel tank would increase its horsepower.
See also 
- Clothing moth for alternative treatments for clothes moths
- "Collecting and Preserving Insects and Mites: Tools and Techniques". United States Department of Agriculture - Agricultural Research Service. Retrieved 26 June 2011.
- Uncommon Uses for Common Household Products. Frank W. Cawood and Associates. 2000. p. 126. ISBN 1-890957-39-9.
- "National Pesticide Information Center"
- "Guide to Safe Removal". Squirrels in the Attic. Retrieved 19 April 2012.
- "Scientists May Have Solved Mystery Of Carcinogenic Mothballs", Physorg.com, June 20, 2006.
- "Mothball sniffing warning issued", BBC News, 27 July 2006.
- "Twin Girls with Neurocutaneous Symptoms Caused by Mothball Intoxication", The New England Journal of Medicine, July 27, 2006.
- Santucci K, Shah B. Association of naphthalene with acute hemolytic anemia. Acad Emerg Med. 2000 Jan;7(1):42-7.
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