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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).


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 acronyms 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.

Due to the health risks of 1,4-dichlorobenzene, and flammability of naphthalene, other substances like camphor are sometimes used.


Mothballs are stored in air-tight bags made of a non-reactive plastic such as polyethylene or polypropylene (other plastics may cause a reaction). The clothing protected by their presence must also be enclosed in one of these plastics and must be sealed within it. Otherwise the vapors will tend to escape and will lose the effectiveness. Manufacturer's instructions regularly warn against using mothballs for any purpose other than those specified by the packaging, as such uses are not only harmful and noxious, they are also frequently considered illegal.[1]

Although occasionally used as snake repellent, use as a rodent, squirrel, and bat repellent is illegal in many areas, and tends to cause more annoyance to humans than to the target pest.[2] Mothballs, however, continue to be advertised as squirrel repellent and are an ingredient in some commercial vermin and snake repellent products. Evidence of their effectiveness as a squirrel repellent is lacking.[3][4]

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.[5] The National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC) and the state of California consider 1,4-dichlorobenzene a carcinogen.[6]

Exposure to naphthalene mothballs can cause acute hemolysis (anemia) in people with glucose-6-phosphate dehydrogenase deficiency.[7] IARC classifies naphthalene as possibly carcinogenic to humans and other animals (see also Group 2B).[8] 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.[9] Under California's Proposition 65, naphthalene is listed as "known to the State to cause cancer".[10]

Research at the University of Colorado at Boulder revealed a probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners.[11][12]

1,4-Dichlorobenzene is a neurotoxin. It has been abused as an inhalant, causing a variety of neurotoxic effects.[13][14]

Mothballs containing naphthalene have been banned within the EU since 2008.[15][16]


As discussed in more detail at Tineola bisselliella, alternatives to mothballs to control clothes moths include dry cleaning, freezing, thorough vacuuming, and washing in hot water.[17] Camphor is also used as a moth repellent, particularly in China.[18] Unlike naphthalene and dichlorobenzene, camphor has medicinal applications and is not regarded as a carcinogen, though it is toxic in large doses.

Pheromone traps are also an effective tool used when attempting to protect valuable clothing.

In popular culture[edit]

As a verb, "mothball" has a metaphorical usage, meaning "to stop work on an idea, plan, or job, but leaving it in such a way that work can continue in the future".[19]

See also[edit]


  1. ^ Uncommon Uses for Common Household Products. Frank W. Cawood and Associates. 2000. p. 126. ISBN 978-1-890957-39-1.
  2. ^ "Problem Wildlife in the Garden and Yard". N?IC. National Pesticide Information Center. Retrieved February 21, 2016.
  3. ^ "Guide to Safe Removal". Squirrels in the Attic. Retrieved April 19, 2012.
  4. ^ "Problem Wildlife in the House". N?IC. National Pesticide Information Center. Retrieved May 24, 2013.
  5. ^ "ToxFAQs™ for Dichlorobenzenes". Toxic Substances Portal. Agency for Toxic Substances and Disease Registry. Retrieved May 24, 2013.
  6. ^ "p-dichlorobenzene (1,4-dichlorobenzene)" (PDF). Material Safety Data Sheet. Archived from the original (PDF) on May 22, 2013. Retrieved May 24, 2013.
  7. ^ Santucci, K; Shah, B. (January 2000). "Association of naphthalene with acute hemolytic anemia". Academic Emergency Medicine. 7(1):42-7.
  8. ^ "Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene". IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 82: 367. 2002. Retrieved December 25, 2008.
  9. ^ "Naphthalene". Air Toxics Web Site. US Environmental Protection Agency. Retrieved May 24, 2013.
  10. ^ Proposition 65 Archived July 29, 2019, at the Wayback Machine, Office of Environmental Health Hazard Assessment
  11. ^ "Scientists May Have Solved Mystery Of Carcinogenic Mothballs". June 20, 2006.
  12. ^ "Mothballs, air fresheners and cancer". Environmental Health Association of Nova Scotia. Retrieved May 24, 2013.
  13. ^ "Mothball sniffing warning issued". BBC News. July 27, 2006.
  14. ^ "Twin Girls with Neurocutaneous Symptoms Caused by Mothball Intoxication". The New England Journal of Medicine. July 27, 2006.
  15. ^ Gray, Kerrina (November 17, 2013). "Council warned against use of poisonous moth balls". Your Local Guardian. Newsquest (London) Ltd. Retrieved November 23, 2012.
  16. ^ Alderson, Andrew (November 15, 2008). "Holy straight bananas – now the Eurocrats are banning moth balls". The Telegraph. Retrieved November 23, 2013.
  17. ^ Eisenberg, Sheryl. "Mothballed". This Green Life. Natural Resources Defense Council. Retrieved May 24, 2013.
  18. ^ 国务院经贸办、卫生部关于停止生产和销售萘丸提倡使用樟脑制品的通知(国经贸调(1993)64号)
  19. ^ "Mothball". Cambridge Dictionary. Retrieved September 2, 2019.

External links[edit]

The dictionary definition of mothball at Wiktionary