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Mothballs are small balls of chemical pesticide and deodorant sometimes used when storing clothing and other articles susceptible to damage from mold or moth larvae (especially clothes moths like Tineola bisselliella).

Use of mothballs when clothing is stored out-of-season has given 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.


Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, many modern mothball formulations instead use 1,4-dichlorobenzene. The latter formulation may be somewhat less flammable, although both chemicals have the same NFPA 704 rating for flammability. The latter chemical is also variously labeled as para-dichlorobenzene, p-dichlorobenzene, pDCB, or PDB, making it harder to identify unless all these synonyms are known to a potential purchaser. Both of these formulations have the strong, pungent, sickly-sweet odor often associated with mothballs. Both naphthalene and 1,4-dichlorobenzene undergo sublimation, meaning that they evaporate from a solid state directly into a gas; this gas is toxic to moths and moth larvae.

Naphthalene and 1,4-dichlorobenzene should not be mixed, as they react chemically to produce a liquid which may cause damage to items being preserved.[1]

Due to the health risks of 1,4-dichlorobenzene, and flammability of naphthalene, other substances like camphor are sometimes used (though camphor has its own toxicity issues).


In addition to repelling or killing insects such as moths and silverfish, mothballs have been suggested for use as a stovepipe cleaner, a snake repellent, and to keep away mice or other pests.[2] However, 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 odor and taste, making this more likely),[3] and will cause serious illness or death.[4] 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.[5]

Mothballs have been promoted as a squirrel repellent, and are an ingredient in some commercial repellent products. They are generally ineffective, and are not a substitute for physical measures to exclude squirrels from building interiors.[6][7]

Older-formula mothballs have also been used by drag racers to enhance the octane rating 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.

Health risks[edit]

The US Department of Health and Human Services (DHHS) has determined that 1,4-dichlorobenzene "may reasonably be anticipated to be a carcinogen". This has been indicated by animal studies, although a full-scale human study has not been done.[8] The National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC), and the state of California consider 1,4-dichlorobenzene to be a carcinogen.[9]

Exposure to naphthalene mothballs can cause acute haemolysis (anemia) in people with glucose-6-phosphate dehydrogenase deficiency.[10] IARC classifies naphthalene as possibly carcinogenic to humans and animals (see also Group 2B).[11] IARC points out that acute exposure causes cataracts in humans, rats, rabbits, and mice. Chronic exposure to naphthalene vapors is reported to also cause cataracts and retinal hemorrhage.[12] Under California's Proposition 65, naphthalene is listed as "known to the State to cause cancer".[13]

Research at the University of Colorado at Boulder revealed a probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners.[14][15]

1,4-Dichlorobenzene is a neurotoxin. It has been abused as an inhalant, causing a variety of neurotoxic effects.[16][17]

Mothballs containing naphthalene have been banned within the EU since 2008.[18][3]

Alternatives to mothballs to control clothes moths include freezing, dry cleaning, washing in hot water, or thorough vacuum cleaning.[19] Camphor is also used as a moth repellent, and unlike naphthalene and dichlorobenzene, it has medicinal applications and is not regarded as a carcinogen, though it is toxic in large doses.

See also[edit]


  1. ^ "Collecting and Preserving Insects and Mites: Tools and Techniques". United States Department of Agriculture - Agricultural Research Service. Retrieved 26 June 2011. 
  2. ^ Uncommon Uses for Common Household Products. Frank W. Cawood and Associates. 2000. p. 126. ISBN 1-890957-39-9. 
  3. ^ a b Gray, Kerrina (17 November 2013). "Council warned against use of poisonous moth balls". Your Local Guardian (Newsquest (London) Ltd.). Retrieved 2012-11-23. 
  4. ^ "Health Effects of Mothballs". National Pesticide Information Center. National Pesticide Information Center. Retrieved 24 May 2013. 
  5. ^ "Mothballs (Naphthalene and Paradichlorobenzene)". National Pesticide Information Center. National Pesticide Information Center. Retrieved 24 May 2013. 
  6. ^ "Guide to Safe Removal". Squirrels in the Attic. Retrieved 19 April 2012. 
  7. ^ "Problem Wildlife in the House". National Pesticide Information Center. National Pesticide Information Center. Retrieved 24 May 2013. 
  8. ^ "ToxFAQs™ for Dichlorobenzenes". Toxic Substances Portal. Agency for Toxic Substances and Disease Registry. Retrieved 24 May 2013. 
  9. ^ "p-dichlorobenzene (1,4-dichlorobenzene)" (PDF). Material Safety Data Sheet. Retrieved 24 May 2013. 
  10. ^ Santucci K, Shah B. Association of naphthalene with acute hemolytic anemia. Acad Emerg Med. 2000 Jan;7(1):42-7.
  11. ^ "IARC Monographs on the Evaluation of Carcinogenic Risks to Humans". Monographs on the Evaluation of Carcinogenic Risks to Humans, Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene, Vol. 82 (2002) (p. 367). Retrieved 25 December 2008. 
  12. ^ "Naphthalene". Air Toxics Web Site. US Environmental Protection Agency. Retrieved 24 May 2013. 
  13. ^ Proposition 65, Office of Environmental Health Hazard Assessment
  14. ^ "Scientists May Have Solved Mystery Of Carcinogenic Mothballs",, June 20, 2006.
  15. ^ "Mothballs, air fresheners and cancer". Environmental Health Association of Nova Scotia. Environmental Health Association of Nova Scotia. Retrieved 24 May 2013. 
  16. ^ "Mothball sniffing warning issued", BBC News, 27 July 2006.
  17. ^ "Twin Girls with Neurocutaneous Symptoms Caused by Mothball Intoxication", The New England Journal of Medicine, July 27, 2006.
  18. ^ Alderson, Andrew (15 Nov 2008). "Holy straight bananas – now the Eurocrats are banning moth balls". The Telegraph. Retrieved 2013-11-23. 
  19. ^ Eisenberg, Sheryl. "Mothballed". This Green Life. Natural Resources Defense Council. Retrieved 24 May 2013. 

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