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Mothball odor removal & mothball chemical & gas hazards: here we describe the detection of and risks of exposure to mothball chemicals & odors when moth repellent products are applied indoors in buildings.
We describe how to get rid of mothball odors in buildings, building furnishings, clothing, or vehicles.
We note the possible health hazards from exposure to mothball odors (and gases) as well as the child hazard of eating mothballs or moth repellent products. We discuss methods to reduce mothball chemical & gas exposure.
We cite authoritative sources of information about safe and proper use of moth repellents and about mothball and moth repellent chemistry, child hazards, indoor air quality and health concerns, and proper application and use of these products.
Some people have also tried using moth repellent products like mothballs to keep rodents and other pests out of certain building areas or out of stored vehicles.
Placing an open box of mothballs under the hood of my MG midget while it was stored kept squirrels and mice from nesting in the engine compartment, and leaving a box of mothballs inside the car was an attempt to keep the same pests out of the vehicle interior too.
Watch out: we do not recommend placing mothballs, moth cakes, or moth repellent flakes inside building rooms, crawl spaces, attics, wall or ceiling cavities, trash cans, nor inside vehicles, both because the fumes and chemicals can be hazardous to humans and because the odor can later be difficult to get rid-of. We explain this problem in detail below.
Watch out: because mothballs are a registered pesticide and because of the toxicity of their chemicals, it is illegal to use mothballs or moth crystals, cakes, etc. as a repellent for animal pests (birds, cats, deer, dogs, moles, pigeons, mice, skunks, raccoons,snakes, squirrels, etc.) 
Pesticides are a special class of organic chemicals designed to kill living organisms.
In addition to the compounds used in the home and garden, the class of chemicals regulated as pesticides also include kitchen and bath disinfectants, flea and tick products, and swimming pool chemicals.
In most cases, both the active ingredient targeted to one or more pests and the “inert” carriers are organic chemicals that are toxic to humans.
Every registered pesticide has a “signal” word on the label, ranking the level of toxicity to humans, as follows:
Danger—Poison: highly poisonous
Danger: poisonous or corrosive
Warning: moderately hazardous
Caution: least hazardous
Page top image of mothballs courtesy of Wikipedia creative commons. Clothes moth image shown at above left is from Stone & Stock, PNW who provide an excellent guide to moth control. 
Health Effects of Exposure to (or ingestion of) Mothballs, Moth cakes, Moth Repellent Crystals
Mothballs contain either of the chemicals paradichlorobenzene or naphthalene. Paradichlorobenzene is classified as a possible human carcinogen by the EPA, and its vapors can irritate skin, eyes, and the respiratory tract.
Large doses can damage the liver. Mothballs are not intended to be placed in open spaces such as rooms, closets, or vehicles. Rather they should be used in an airtight space such as a clothes storage bag. 
Mothballs are fumigants that will dissolve or sublime at lower temperatures; mothballs thus work by a process of sublimation - the solid ball of chemicals converts directly to a gas that enters the air nearby.  But believe it or not mothballs or moth crystals may also be a child hazard if eaten - as has happened. 
Symptoms of exposure to naphthalene include headache, nausea, dizziness, and difficulty breathing. Paradichlorobenzene is also a potential hazard, although typically less so compared to naphthalene. ... Eating just one mothball containing naphthalene can damage a young child’s red blood cells.... 
Exposure to naphthalene promotes hemolytic anemia, associated with fatigue in mild cases and acute kidney failure in severe cases. Poisonings of infants have been reported after dressing the children in clothing stored in naphthalene mothballs.
Below: an edited (excerpted) page from a 1963 Boys Life magazine describing a do-it-yourself home science project using moth balls, water, baking soda, and vinegar.
Watch out: we do not recommend repeating this experiment unless under supervision of your science teacher or another suitable expert. Mothballs are a particular hazard to children, especially small children who may mistake a mothball for something edible.
FYI for our Australian readers, there have been recent news reports inquiring if mothballs are harmful to babies - we're researching that question.
Certainly eating sucking on mothballs, and probably exposure to high levels of mothball offgassing can be harmful to babies and mothball odors can trigger problems for people with allergies and asthma (including this site editor).
Dawson back in 1958 documented this concern: it's certainly not "new" news.
Research on the Health Hazards of Eating Mothballs: Naphthalene Poisoning
Dawson, Jean P., William W. Thayer, and Jane F. Desforges, "Acute Hemolytic Anemia in the Newborn Infant due to Naphthalene Poisoning: Report of Two Cases with Investigations into the Mechanism of the Disease." Blood, J. Hematol. 13, no. 12 (1958): 1113-25.
Abstract : At least 18 cases of acute haemolytic anaemia after exposure to naphthalene have been reported since 1949. In this paper there is a description of 2 cases of this condition in new-born children with a report on the investigations of erythrocyte metabolism in these infants and their families.
The cases occurred in Negro infants, , a 14-day-old female and a 9-day-old male who were admitted to the Boston City Hospital because of icterus and pallor. Both infants were normal at their birth in hospital and only became ill after returning home, where the girl was dressed in " clothing heavily impregnated with naphthol " and the boy in " clothing impregnated with naphthalene mothballs". Both children recovered. Their states on admission are described with details of the results of blood examinations.
The biochemical investigations of the peripheral blood of the 2 patients and some of the members of their families which were carried out are described in detail. These studies included examination of Heinz bodies, glutathione determination, glutathione stability, methaemoglobin reduction, glucose-6-phosphate de-hydrogenase activity and glutathione reductase.
The findings of these studies are described with tables and figures and there is a long discussion and many references.
In both infants there was " glutathione instability upon incubation with acetyl phenyl-hydrazine and naphthol months to years later. Several members of their families exhibited a similar defect with evidence that it is inherited as a simple dominant". In those individuals with glutathione instability there were indications of deficiency in glucose-6-dehydrogenase activity.
M. E. Delafield.
Siegel, Earl, and Suman Wason. "Mothball toxicity." Pediatric Clinics of North America 33, no. 2 (1986): 369-374.
Abstract: Accidental mothball ingestion is very common in children. Mothballs consist either of naphthalene or paradichlorobenzene, the toxicities of which are very diferent. This article focuses on the management of mothball ingestion with reference to these major ingredients.
Valaes, Timos, Spyros A. Doxiadis, and Phaedon Fessas. "Acute hemolysis due to naphthalene inhalation." The Journal of pediatrics 63, no. 5 (1963): 904-915.
How to Reduce Indoor Exposure to Mothball Odors, Chemicals, Gases
Avoid unnecessary use of mothballs & moth repellents: When possible, the best approach
is to find non chemical approaches to pests, including moths. That includes
Don't use moth repellents if you don't have a moth problem in the first place. Moth larvae are shiny light colored wormlike organisms about 1/2-inch in length. Adult clothing-eating moths are white
(Image at left, PNW) 
Don't blame the innocent. None of the other moth or insect pictures shown in this article are clothing-eating insects.
To check for a moth infestation in your home, and keeping in mind that most moths are not the species that attack fabrics, you can try a pheromone trap to monitor for moth activity. The insects shown in our photo (left) attack our fig plant but not our clothing.
Avoid importing moths, moth pupae or moth larvae (it's the larvae that eat animal fibers and fabrics) by cleaning used or old clothing that is "new" to your home before storing those materials away
When storing clothing or other soft goods, especially woolens or other animal fiber materials, use clothing storage containers that are dry and airtight, first to keep moths out, and second, especially if moth repellent products are to be placed therein, to prevent mothball odors from invading other building areas or materials.
Do not simply place moth repellent products in open boxes in areas such as rooms, closets, garages, or vehicles in an attempt to keep them moth (or mouse, or squirrel) free.
Cedar closets? cedar fumes are toxic to moths only at high concentrations. Don't trust a cedar closet alone to prevent moth damage, although indeed cedar wood and cedar oils do avoid the mothball hazard and odor issue.
Dried lavender and cedar fiber balls as moth repellents are not supported by good evidence. [2-Farr]
Wash or dry clean clothing before putting it into storage; clean clothes are less attractive to moths according to some experts. Moth eggs, moth larvae as well as adult moths can all be killed by a hot water wash cycle. Moth eggs, pupae, or even adults may already be present in clothing, including cotton even though which moths are not directly attracted to that material. Dry-clean wool or other animal fiber materials (to which moths are attracted) for the same reason. 
Read the mothball package label and closely follow instructions. If you are going to use a moth repellent product like mothballs, read and follow the directions on the product label. keep these products away from children who may be especially vulnerable not only to vapors from mothballs but as something sometimes eaten.
Dispose of unwanted mothballs safely. Most of thesechemicals contain VOCs that will vaporize and getinto the household air. If you cannot dispose of partiallyused containers, store outside the living space.
Minimize exposure to moth repellant products. When used,place mothballs, moth repellent cakes or moth crystals in a well-sealed trunk or other container thatcan be stored in ventilated areas outside of the main
living space, such as attics or attached garages.
Minimize exposure to some air fresheners: Paradichlorobenzene is also the active ingredient inmany air fresheners and should be avoided.
Reader Question: How can we get rid of an annoying mothball odor in our Condo?
We moved into a condo, which is a concrete block structure 3 months ago. Shortly after the move we began to smell moth balls.
After following the smell we were able to find out that the unit above us displaced several moth balls throughout there unit, tightly sealed the unit up without air conditioning on(we live in Florida) and left for the summer.
As the smell increased in our unit we begged parties involved to rid the unit of the moth balls and air it out.
Finally this was done, however even though the smell appears to be gone sometimes, other times we can still smell a bad odor, sometimes now the odor is less mothball smell and just simply a bad odor.
We have tried everything and are desperate to solve the problem. Is it possible to get rid of this toxic odor?
Any help would be greatly appreciated. - B.P. 9/22/2012
Reply: How to get rid of mothball odors in buildings, contents, clothing, furnishings
Indeed the odor from mothballs is a VOC-like substance (paradichlorobenzene or naphthalene) that quite penetrates many materials including even drywall, furnishings, carpeting, and it can take quite a while for it to diminish. And most people can smell mothballs - the characteristic odor of those chemica
ls can generally be detected in air at a concentration of just a few parts per billion, so getting rid of mothball odors is going to take some thorough airing out and cleaning.
Airing out the original building area helps, this means opening windows and perhaps even using fans to move a good volume of fresh air through the building area - weather permitting. This is the best and principal means of reducing indoor mothball odors in building spaces themselves, and it will help reduce odors from furnishings and carpets and draperies too.
Find & address the principal odor source: in general, odor removal of any sort in buildings is most effective if we can identify the exact odor source and remove or clean or seal that source. - what materials absorbed the gases, airborne compounds or VOCs from the mothballs - perhaps using
Turning up the heat in the space where mothball odors persist can help drive volatiles back into building air where in combination with fresh air venting you will reduce mothball odors. For soft goods such as upholstered couches you may speed up the mothball odor removal by using a hair dryer (on low or medium temperature) to heat the upholstered surfaces.
For soft goods such as clothing that has absorbed mothball odors, having the clothes dry-cleaned or laundered, or sometimes simply running washable clothing through the clothes dryer on medium heat will suffice to get rid of the mothball odors.
If that doesn't solve the problem and you need to go further you'd need to track down the principal sources of the odor
Watch out: for mothball odor solutions that are ineffective, are products sold by someone with a conflict of interest, or may in fact make matters worse:
Ozone generators for mothball odors???? Do not try using ozone or an indoor ozone generator to get rid of mothball odors. Improperly used you will find you've made a worse problem than before.
See OZONE MOLD / ODOR TREATMENT WARNINGS for details and for links to articles that describe how over-treatment by ozone can generate new horrible, costly-to-remove odors in buildings.
Activated charcoal to "remove" mothball odors ??? In our OPINION the recommendation by some sources to place activated charcoal in the space where the mothball odors are strong is not likely to be useful; air circulation and fresh air are more effective than relying on a passive absorption system that never addresses the source of odors.
Air purifiers to remove mothball smells? In our OPINION, a portable indoor "air purifier" is unlikely to move enough air through a charcoal filter to be effective except in the case perhaps of a very small enclosed space.
Unfortunately some key studies we have reviewed tested a portable air "purifier" by placing it into an enclosed chamber with a limited amount of a specific pollutant - not a realistic nor real-world situation.
Life Expectancy of Mothballs Used in Buildings - Mothball Sublimation Rate
On 2017-07-27 by Laurie Davis - What is the life expectancy of a moth ball in a hot area?
What is the life expectancy of a moth ball in a hot area? How long does it continue to releasee the harmful fumes?
On 2017-07-27 by (mod) - Life Expectancy of Mothballs Used in Buildings - Mothball Sublimation Rate
If you will permit me to wave my arms about mothball sublimation rates as a preface to giving an opinion about how long a mothball will "last" in use then my estimates of mothball life will, perhaps, make more sense. Tennakone (1978) looked at the sublimation rate for mothballs - but I've not yet gotten a copy of the full article to support the following opinion with science.
Mothballs exposed to the open air will be seen to shrink in size, eventually disappearing, following a process called sublimation: the solid (mothball) converts to a gas without ever entering an intermediate liquid state. The rate of sublimation of mothballs is determined principally by the amount of air available to or circulating around the mothball.
That's because the sublimation rate of mothballs depends on the relative naphthalene gas or para-dichlorobenzene vapor pressure difference between the thin layer of air at the surface of the mothball and the surrounding air.
When mothballs are kept in a small sealed container or relatively-airtight bag (as they are in a sealed box of mothballs in the store), the gas vapors are trapped around the mothballs, slowing their rate of sublimation to almost nothing. But when the same mothballs are spread about in more-open air the vapor pressure differences of the mothball gases permit them to continue to off-gas into the surrounding area.
Mothballs that are actually in the spherical form, about 1/2" in diameter when new, will last from a month to several years or longer depending the type of mothball and on how they are placed.
Furthermore the life of mothballs depends on the product chemistry: naphthalene mothballs take much longer to dissipate than mothballs comprised of para-dichlorobenzene.
For example based on simple experiments and observations of mothballs I've placed in buildings, closets, bureaus, or kept in closed packages, I estimate that:
a single para-dichlorobenzene mothball in open air may dissipate in a month or two
a single para-dichlorobenzenemothball placed under clothing and not in open air may dissipate in 3-6 months
a box of para-dichlorobenzenemothballs left together in the box with the lid cut open and placed in a closet or under clothing may last for more than a year.
a single naphthalene mothball in open air may dissipate in a 3-6 months
a single naphthalene mothball placed under clothing and not in open air may dissipate in 12 months
a box of naphthalene mothballs left together in the box with the lid cut open and placed in a closet or under clothing may last for several years or longer.
sealed packages of mothballs of either type probably have a shelf life of several years
In a hot area like an attic where convection currents may be moving more air about, those mothball life expectancies will be less due to the effects of both temperature and air movement or air velocity on the sublimation rate of the mothballs of either formula. Moisture might also be a factor in the the rate of mothball sublimation.
"In air, the half-life of naphthalene and paradichlorobenzene is less than one day and about 31 days, respectively." (Fishel 2014)  at REFERENCES.
But that half-life expression is misleading. It would only be accurate if we could obtain a measured volume of these two gases ALONE, that is, without a source that continues to emit them, and if we could then obtain more specific information about the concentration of those gases in the space and the rate of fresh air ventilation of the space as well as quite a few other factors. Watch out: however the fumes from these gases may permeate and remain in clothing or building materials after the actual mothballs or moth crystals have dissipated.
Differences Between Paradichlorobenzene Mothballs & Napthalene Mothballs
These two substances are chemically different, have different properties.
Napthalene mothballs produce an off-gassing (through sublimation) that creates and environment that repels moths as well as some other creatures. Napthalene mothballs, and the odor they produce, remains in the environment of use longer than Paradichlorobenzene mothballs. That is, it will take longer for the Napthalene odor to dissipate even when the mothball source has been consumed or removed.
Paradichlorobenzene mothballs produce less noticeable odor (to humans) and its gas will dissipate in free air more quickly than the offgassing product of Napthalene mothballs. If all other parameters are the same (air movement, temperature, etc), Paradichlorobenzene mothballs produce a higher-concentration of gas in the treatment area than Napthalene mothballs, possibly increasing the effectiveness of Paradichlorobenzene for the murder or discouragement of moths.  at REFERENCES
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Tennakone, K., and M. G. C. Peiris. "Sublimation of moth balls." American Journal of Physics 46, no. 4 (1978): 418-419.
Abstract: The study of the decay of a moth ball due to sublimation is an instructive exercise in physics which demonstrates diffusion phenomena. The rate at which a moth ball exposed to the atmosphere wears away due to sublimation is calculated. Experiments are given to demonstrate the validity of the calculation.
 Thomas M. Riddick, "Controlling Taste, Odor and Color With Free Residual Chlorination", Journal (American Water Works Association)
Vol. 43, No. 7 (JULY 1951), pp. 545-552, American Water Works Association, Article Stable URL: http://www.jstor.org/stable/41236445
 Douglas M. Baker, M.D., "Holiday Hazards", Pediatric Emergency Care, Vol. 1 No. 4, December 1985 Lippincott-Raven, retrieved 9/22/12
Abstract: Presented is a selective review of the toxicities of various plants, decorations, and miscellaneous items popularly used during the holiday season. Particularly hazardous agents include mistletoe, holly, bubble lights, fireplace flame colors, alkaline batteries, and mothballs.
Specific questions regarding management of exposure to these items should be referred to regional poison control centers. Avoidance is the most effective treatment. ... [regarding mothballs, ... decontamination is advised for ingestions of greater than one half of a naphthalene mothball and more than two to three paradichlorobenzene mothballs ...]
 Charles M. McGinley, P.E., Michael A. McGinley, MHS, Donna L. McGinley, " “Odor Basics”,
Understanding and Using Odor Testing", paper presentation, The 22nd Annual Hawaii Water Environment Association Conference., Honolulu, Hawaii: 6-7 June 2000, St. Croix Sensory Inc. / McGinley Associates, P.A.
13701 - 30th Street Circle North
Stillwater, MN 55082 U.S.A.
email@example.com, retrieved 9/22/12, original source http://www.fivesenses.com/Documents/Library/33%20
%20Odor%20Basics.pdf, [copy on file as Odor_Basics.pdf]
 Jon H. Ruth, "Odor Thresholds and Irritation Levels of Several Chemical Substances: A Review", American Industrial Hygiene Association Journal
Volume 47, Issue 3, 1986, retrievedf 9/22/12,
Abstract: A collation of odor threshold data for approximately 450 chemical substances is presented. The range of odor thresholds reported in the literature is shown along with any reported threshold of irritation to humans.
These data can assist the industrial hygienist in determining when an “odor” may be in excess of the Threshold Limit Value®, when an organic vapor respirator is not acceptable due to the lack of an odor warning at the end of a cartridge life, and where odors may not indicate a hazard due to extremely low odor thresholds which may be well below the respective TLVs.
 Edward Avila DO,
Paul Schraeder MD,
Ajit Belliappa MD,
Scott Faro MD, "Pica With Paradichlorobenzene Mothball Ingestion Associated With Toxic Leukoencephalopathy", Journal of Neuroimaging
Volume 16, Issue 1, pages 78–81, January 2006, retrieved 9/22/12,
Abstract: This is a case report of central nervous system toxicity associated with paradichlorobenzene (PDCB) ingestion. The patient had ingested mothballs composed of 99.99% PDCB for a period of 7 months.
She was admitted for depression and had no neurologic symptoms. Later she developed an acute cerebellar syndrome followed by stupor and coma. An extensive workup was negative except for decreasing levels of PDCB in her serum. Imaging revealed a diffuse leukoencephalopathy. Her clinical picture was attributed to PDCB toxicity.
 Stone, David L. (David Louis), Stock, T. (Tim), "MOTHBALLS: proper use and alternative controls for clothes moths", [PDF] PNW 606-E, May 2008, Oregon State University. Extension Service
Washington State University. Extension
University of Idaho. Extension, May, 2008, retrieved 9/22/12, original source: http://scholarsarchive.library.oregonstate.edu/
xmlui/bitstream/handle/1957/20800/pnw606-e.pdf?sequence=1, citation: http://hdl.handle.net/1957/20800,
Abstract: In some homes, clothes moths can damage garments and other belongings. There are two common species of clothes moths in the Pacific Northwest: the webbing clothes moth (Tineola bisselliella) and the casemaking clothes moth (Tinea pellionella). The larvae, or immature form, of the moths are responsible for the damage done to personal belongings. Citing the following 2 sources on mothball chemistry, use, hazards:
 Black, Judy. Fabric and Museum Pests. In
Mallis Handbook of Pest Control, 9th edition,
S.A. Hedges and D. Moreland, eds. GIE Media,
Cleveland, OH, 2004, pp. 581 –623.
 U.S. Department of Health and Human Services.
Illness Associated with Exposure to Naphthalene
in Mothballs—Indiana. Morbidity and Mortality
Weekly Report, 1983, Vol. 32: 34–5.
 Willert Home Products, Mold Preventative FAQs, [PDF], Willert, USA, 4044 Park Avenue St. Louis, Missouri 63110 USA Tel: (001) 314 772 2822 Email: firstname.lastname@example.org 2017/07/27, original source: http://www.willert.clients.danskadesigns.com/files/Moth-Preventive-FAQs.pdf
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