Mothballs are small balls of chemical

pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...

and

deodorant A deodorant is a substance applied to the body to prevent or mask body odor due to bacterial breakdown of perspiration or vaginal secretions, for example in the armpits, groin, or feet. A subclass of deodorants, called antiperspirants, prevents s ...

, sometimes used when storing clothing and other materials susceptible to damage from

mold A mold () or mould () is one of the structures certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal seco ...

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

larvae (especially

clothes moth Clothes moth or clothing moth is the common name for several species of moth considered to be pests, whose larvae eat animal fibres (hairs), including clothing and other fabrics. These include: * ''Tineola bisselliella'', the common clothes moth ...

s like ''

Tineola bisselliella ''Tineola'' is a genus of moths the family Tineidae. There are two species, including the familiar common clothes moth (''T. bisselliella'').naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

, but due to naphthalene's flammability, many modern mothball formulations instead use

1,4-dichlorobenzene 1,4-Dichlorobenzene (1,4-DCB, ''p''-DCB, or ''para''-dichlorobenzene, sometimes abbreviated as PDCB or para) is an organic compound with the formula C6H4Cl2. This colorless solid has a strong odor. The molecule consists of a benzene ring with two ...

. The latter formulation may be somewhat less flammable, although both chemicals have the same

NFPA 704 "NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response" is a standard maintained by the U.S.-based National Fire Protection Association. First "tentatively adopted as a guide" in 1960, and revised sev ...

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 Sublimation or sublimate may refer to: * ''Sublimation'' (album), by Canvas Solaris, 2004 * Sublimation (phase transition), directly from the solid to the gas phase * Sublimation (psychology), a mature type of defense mechanism * Sublimate of mer ...

, meaning that they transition 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 Camphor () is a waxy, colorless solid with a strong aroma. It is classified as a terpenoid and a cyclic ketone. It is found in the wood of the camphor laurel ('' Cinnamomum camphora''), a large evergreen tree found in East Asia; and in the k ...

are sometimes used.

Uses

Mothballs are stored in air-tight bags made of a non-reactive plastic such as

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and ...

(other plastics may be degraded or softened). The clothing to be protected should be sealed within airtight containers; otherwise the vapors will tend to escape into the surrounding environment. 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. Although occasionally used as snake repellent, mothball use as a rodent, squirrel, or bat repellent is illegal in many areas, and tends to cause more annoyance and hazard to humans than to the target pest. However, mothballs continue to be advertised as squirrel repellent and are an ingredient in some commercial vermin and snake repellent products.

Health risks

The

US Department of Health and Human Services The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the U.S. federal government created to protect the health of all Americans and providing essential human services. Its motto is " ...

(DHHS) has determined that 1,4-dichlorobenzene "may reasonably be anticipated to be a

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

". This has been indicated by animal studies, although a full-scale human study has not been done. The

National Toxicology Program The National Toxicology Program (NTP) is an inter-agency program run by the United States Department of Health and Human Services to coordinate, evaluate, and report on toxicology within public agencies. The National Toxicology Program is headqua ...

(NTP), the

International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...

(IARC) and the

state of California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

consider 1,4-dichlorobenzene a carcinogen. Exposure to naphthalene mothballs can cause acute

hemolysis Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...

(anemia) in people with

glucose-6-phosphate dehydrogenase deficiency Glucose-6-phosphate dehydrogenase deficiency (G6PDD), which is the most common enzyme deficiency worldwide, is an inborn error of metabolism that predisposes to red blood cell breakdown. Most of the time, those who are affected have no symptoms. ...

. IARC classifies naphthalene as possibly carcinogenic to humans and other animals (see also Group 2B). IARC points out that acute exposure causes

cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...

s in humans, rats, rabbits, and mice. Chronic exposure to naphthalene vapors is reported to also cause cataracts and

retinal hemorrhage Retinal hemorrhage (UK English: retinal haemorrhage) is a disorder of the eye in which bleeding occurs in the retina, the light sensitive tissue, located on the back wall of the eye. There are photoreceptor cells in the retina called rods and c ...

. Under California's

Proposition 65 Proposition 65 (formally titled The Safe Drinking Water and Toxic Enforcement Act of 1986, and also referred to as Prop 65) is a California law passed by direct voter initiative in 1986 by a 63%–37% vote. Its goals are to protect drinking water s ...

, naphthalene is listed as "known to the State to cause cancer". Research at the

University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado sys ...

revealed a probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners. In addition to their cancer risks, mothballs are known to cause liver and kidney damage. 1,4-Dichlorobenzene is a

neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...

. It has been abused as an

inhalant Inhalants are a broad range of household and industrial chemicals whose volatile vapors or pressurized gases can be concentrated and breathed in via the nose or mouth to produce intoxication, in a manner not intended by the manufacturer. They ...

, causing a variety of neurotoxic effects. Mothballs containing naphthalene have been banned within the EU since 2008.

Alternatives

As discussed in more detail at ''

Tineola bisselliella ''Tineola'' is a genus of moths the family Tineidae. There are two species, including the familiar common clothes moth (''T. bisselliella'').Camphor Camphor () is a waxy, colorless solid with a strong aroma. It is classified as a terpenoid and a cyclic ketone. It is found in the wood of the camphor laurel ('' Cinnamomum camphora''), a large evergreen tree found in East Asia; and in the k ...

is also used as a moth repellent, particularly in China. Unlike

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

and

dichlorobenzene There are three distinct chemical compounds which are dichlorobenzenes: *1,2-Dichlorobenzene or ''ortho''-dichlorobenzene; *1,3-Dichlorobenzene or ''meta''-dichlorobenzene; *1,4-Dichlorobenzene or ''para''-dichlorobenzene. All three isomers are col ...

, camphor has medicinal applications and is not regarded as a carcinogen, though it is toxic in large doses. Red cedar wood and oil is also used as an alternative moth repellent.

Pheromone trap A pheromone trap is a type of insect trap that uses pheromones to lure insects. Sex pheromones and aggregating pheromones are the most common types used. A pheromone-impregnated lure, as the red rubber septa in the picture, is encased in a convent ...

s are also an effective diagnostic tool and can sometimes be an effective control tool to protect valuable clothing.

In popular culture

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". "Mothballed" is a common adjective to describe ships or aircraft which are stored for long periods, but not sent for scrapping.

References

External links

{{wiktionary-inline, mothball
Mothballs (Naphthalene and Paradichlorobenzene) - National Pesticide Information Center

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Argonne National Laboratory Argonne National Laboratory is a science and engineering research United States Department of Energy National Labs, national laboratory operated by University of Chicago, UChicago Argonne LLC for the United States Department of Energy. The facil ...