Mothballs are made of one of two chemicals: naphthalene or paradichlorobenzene (sometimes written as 1,4-dichlorobenzene or PDCB). Both are solid pesticides that slowly turn into gas at room temperature, filling enclosed spaces with fumes that repel or kill fabric-eating insects like clothes moths and carpet beetles. Neither chemical is harmless, and both pose real health risks when used improperly, inhaled over long periods, or accidentally swallowed, especially by children or pets.
The Two Chemicals Inside Mothballs
Naphthalene is a white, waxy solid derived from coal tar or crude oil. It has the pungent, unmistakable smell most people associate with mothballs. Paradichlorobenzene is also a white crystalline solid, but it has a slightly sweeter, less acrid odor. Both work the same way: they sublimate, meaning they transition directly from a solid into a vapor without passing through a liquid phase. That vapor accumulates inside a sealed container like a garment bag or storage trunk, reaching concentrations high enough to kill moth larvae and other textile pests.
From a toxicity standpoint, the two are not interchangeable. Naphthalene is generally considered the more dangerous of the two, particularly if swallowed. Emergency physicians have developed simple tests to tell them apart when a patient shows up after ingesting an unlabeled mothball. One method involves dropping a mothball into turpentine: paradichlorobenzene dissolves completely within about an hour, while at least a quarter of a naphthalene mothball remains intact after the same period.1PubMed. Mothball differentiation: naphthalene from paradichlorobenzene That distinction matters because the treatment approach differs depending on which chemical was ingested.
In many countries, paradichlorobenzene has become the more common formulation on store shelves because it is considered somewhat less acutely toxic than naphthalene. But “less toxic” is relative, not a safety endorsement. Paradichlorobenzene can still affect the liver, kidneys, skin, lungs, and central nervous system with prolonged or heavy exposure.2PubMed Central. Para-dichlorobenzene toxicity – a review of potential neurotoxic manifestations
What Happens When You Breathe Mothball Fumes
Mothballs are designed to release their vapors slowly inside a sealed space, but people routinely use them in open rooms, closets with no doors, attics, basements, and even scattered around foundations to deter rodents or snakes. That open-air use means the chemicals linger in the air you breathe at home, sometimes at surprisingly high levels. A study analyzing naphthalene concentrations in residential indoor air found that the median long-term level was just under 1 microgram per cubic meter, but the distribution was extremely skewed. About 14 percent of homes exceeded the chronic reference concentration considered safe for long-term non-cancer exposure, and roughly 8 percent had levels above 10 micrograms per cubic meter. The highest concentrations, reaching 200 micrograms per cubic meter, were linked to excessive use of naphthalene as a pest repellent.3PubMed Central. Sources, concentrations, and risks of naphthalene in indoor and outdoor air
Those numbers mean that a small but meaningful fraction of homes using mothballs are chronically exceeding the exposure thresholds that health agencies have set. The people at greatest risk are those who use mothballs liberally throughout the home rather than confining them to sealed containers, and those who live in smaller or poorly ventilated spaces where the vapors concentrate. Mothballs placed in open bowls, tucked under furniture, or scattered in crawlspaces create persistent low-level exposure that can continue for months.
Acute Poisoning and Who Is Most Vulnerable
Swallowing a mothball is a genuine medical emergency, especially for young children. Naphthalene mothballs are the bigger concern here. After ingestion, symptoms typically appear within two to four days and can include dark brown urine, watery diarrhea, and vomiting. Vital signs may show fever, a rapid heart rate, and low blood pressure. A characteristic finding is persistently low oxygen saturation readings on a pulse oximeter, around 84 to 85 percent, that do not improve even when supplemental oxygen is given. Lab work in these cases often reveals hemolytic anemia, a condition where red blood cells are destroyed faster than the body can replace them, along with elevated bilirubin and kidney dysfunction.4PubMed Central. Naphthalene Toxicity: Methemoglobinemia and Acute Intravascular Hemolysis
Children are especially at risk because mothballs can look like candy or small toys to a toddler. A single naphthalene mothball weighs only a few grams, but that can be a significant dose for a small child. The white, round shape and sometimes faintly sweet smell of paradichlorobenzene versions make them even more tempting.
People with glucose-6-phosphate dehydrogenase deficiency, known as G6PD deficiency, face a disproportionately severe reaction. G6PD deficiency is one of the most common enzyme deficiencies in the world, affecting hundreds of millions of people, with higher prevalence in populations of African, Mediterranean, Middle Eastern, and Southeast Asian descent. In people with this condition, naphthalene exposure triggers a particularly aggressive form of hemolytic anemia because their red blood cells lack adequate protection against the oxidative damage the chemical causes.5PubMed Central. Naphthalene-Induced Acute Oxidative Hemolysis With Methemoglobinemia in Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency What might cause mild symptoms in a person with normal enzyme levels can cause life-threatening anemia in someone with G6PD deficiency, sometimes from inhalation exposure alone, not just ingestion.
The mechanism behind this vulnerability involves oxidative stress. Naphthalene and paradichlorobenzene generate reactive molecules in the body that damage hemoglobin and other proteins. Normally, an enzyme pathway involving glutathione neutralizes those reactive molecules. In G6PD deficiency, that pathway is impaired, so the damage accumulates unchecked, destroying red blood cells en masse.6PubMed Central. Severe Hemolytic Anemia After Mothball Ingestion Complicated by an Undiagnosed Enzyme Deficiency: A Case Report Many people with G6PD deficiency are undiagnosed, which means a mothball exposure can be the event that first reveals the condition.
Chronic Exposure and Cancer Concerns
The acute poisoning scenario gets the most dramatic attention, but the chronic, low-level exposure from living with mothball fumes in your home may be the more widespread concern. Workers occupationally exposed to paradichlorobenzene have shown elevated white blood cell counts, higher liver enzyme levels (suggesting liver stress), and elevated markers of kidney strain compared to unexposed workers.7PubMed. Effects of occupational exposure to 1,4-dichlorobenzene on hematologic, kidney, and liver functions Those are occupational exposures, meaning the levels were higher than typical household use, but they illustrate what these chemicals do to the body over time when the dose is high enough.
Naphthalene has been classified as a possible human carcinogen by the International Agency for Research on Cancer (IARC). That classification reflects animal studies showing nasal and lung tumors after inhalation exposure, combined with the fact that naphthalene is essentially everywhere in the indoor environment at some level.8PubMed Central. A critical review of naphthalene sources and exposures relevant to indoor and outdoor air “Possible carcinogen” is the lower tier of cancer concern, meaning the animal evidence is suggestive but the human evidence is not strong enough to be definitive. It is worth noting that the classification applies to naphthalene broadly, not just to mothballs, since the chemical also enters indoor air from tobacco smoke, vehicle exhaust migrating in from attached garages, and certain wood-burning stoves.
Paradichlorobenzene has its own IARC classification as a possible human carcinogen, based on similar reasoning. Neither chemical has been conclusively proven to cause cancer in humans at typical household exposure levels, but the precautionary principle suggests minimizing exposure is a good idea, especially since the exposure is voluntary and easily avoidable.
Pets and Mothballs
Dogs and cats are at significant risk from mothball exposure. Dogs may eat mothballs out of curiosity or because they mistake them for treats. Cats, who groom themselves constantly, can absorb mothball chemicals through their skin and fur after lying on or near treated fabrics. Cats also have a limited ability to metabolize certain compounds through their liver compared to dogs and humans, making them more sensitive to many household chemicals.
Symptoms in pets mirror those in humans: vomiting, lethargy, difficulty breathing, and in severe cases, hemolytic anemia and liver failure. Because pets are smaller, a single mothball represents a proportionally larger dose. If you suspect your pet has ingested or been heavily exposed to a mothball, it warrants an immediate call to a veterinary poison control service or emergency vet clinic. There is no safe way to “wait and see” with mothball ingestion in a small animal.
Common Misuses That Increase Risk
A significant part of the mothball safety problem comes from how people actually use them, which often bears little resemblance to the label instructions. Mothballs are EPA-registered pesticides in the United States, and their labels specify that they should be used only in airtight or tightly sealed containers with the specific fabrics being protected. They are not designed or approved for any of the following uses, all of which are common:
- Open-air pest deterrent: Scattering mothballs around a garden, under a deck, or in a yard to repel snakes, rodents, squirrels, or deer. This is both illegal under federal pesticide law (because it is off-label use) and ineffective, since the vapor dissipates too quickly outdoors to reach concentrations that deter anything.
- Whole-room treatment: Placing mothballs in open closets, attics, basements, or under sinks. This exposes everyone in the home to the fumes and can push indoor air concentrations well above safe thresholds.
- Car or boat storage: Leaving mothballs inside a vehicle or boat during off-season storage. The fumes permeate upholstery, plastics, and rubber, and the enclosed space concentrates the vapor to very high levels.
- Pest control in living spaces: Tucking mothballs behind appliances or in cabinets to deter cockroaches, mice, or other household pests they were never designed to target.
Environmental health professionals have flagged mothball misuse as a recurring problem, particularly in communities where they are culturally used as general-purpose pest repellents or deodorizers rather than strictly for fabric protection.9PubMed Central. Naphthalene Mothballs: Emerging and Recurring Issues and their Relevance to Environmental Health The fact that mothballs are cheap, widely available, and have been around for generations gives people a false sense that they are harmless household products rather than the concentrated chemical pesticides they actually are.
How to Use Mothballs More Safely If You Choose to Use Them
If you do decide to use mothballs for their intended purpose of protecting stored woolens, furs, or other natural-fiber garments, a few practices reduce the risk substantially. First, use them only inside airtight containers: sealed plastic bins, vacuum storage bags, or garment bags that zip completely closed. The point is to keep the vapor in contact with the clothing while keeping it out of your living space. Second, use the minimum quantity listed on the product label. More is not better; it just raises the vapor concentration without improving effectiveness. Third, when you take clothes out of storage, air them out thoroughly outdoors before wearing them. The vapors cling to fabric and will off-gas into your breathing zone if you wear the garments straight out of the bin. Fourth, store the sealed containers in areas away from living spaces, like a garage or shed, rather than in a bedroom closet.
Keep mothballs completely out of reach of children and pets. This means not just placing them high on a shelf, but recognizing that sealed containers can be opened by curious hands. If a child or pet has access to the storage area, consider whether an alternative approach makes more sense entirely.
Alternatives That Do Not Involve Toxic Fumigants
For most people in most situations, mothballs are overkill. Clothes moths are a genuine nuisance that can destroy irreplaceable woolens and silks, but the conditions they need to thrive are specific: they prefer undisturbed, dark spaces with natural fibers, especially items that carry traces of sweat, food, or body oils. Regular laundering or dry cleaning before storage, combined with sealed containers, eliminates the conditions moth larvae need to feed and grow. You do not need to add a chemical fumigant on top of proper storage hygiene.
Cedar wood and cedar oil have been used as moth repellents for centuries. Fresh cedar does contain compounds that can kill very young moth larvae, but the effect diminishes as the cedar ages and its oils evaporate. Sanding the wood or applying fresh cedar oil periodically restores some effectiveness. Cedar alone is not reliable enough for high-value or irreplaceable textiles, but combined with sealed storage and clean garments, it adds a layer of protection without the toxicity.
Lavender sachets, dried rosemary, and other herbal repellents have some insect-deterring properties, though the evidence for their effectiveness against clothes moths specifically is largely anecdotal rather than rigorously tested. They smell pleasant and pose no toxicity risk, which makes them a reasonable addition to a storage strategy even if they are not the primary line of defense.
For active infestations rather than prevention, freezing is surprisingly effective. Placing infested garments in a sealed bag in a household freezer at -18°C (0°F) for at least 72 hours kills moth eggs, larvae, and adults. Commercial cold-storage facilities can treat larger collections. Heat treatment also works: exposure to temperatures above about 50°C (120°F) for 30 minutes or more is lethal to all life stages of clothes moths.
In museum and archival settings, where textile preservation is critical and chemical exposure must be minimized, integrated pest management strategies have moved away from mothballs entirely. One approach involves releasing tiny parasitoid wasps that target clothes moth eggs. Research in museum collections found that regular, long-term exposure to these wasps reduced clothes moth populations over time as part of a broader strategy that included insect monitoring and preventive measures.10Journal of Entomological and Acarological Research. Using parasitoid wasps in Integrated Pest Management in museums against biscuit beetle (Stegobium paniceum) and webbing clothes moth (Tineola bisselliella) These wasps are harmless to humans, textiles, and other household contents. They are commercially available in some regions for home use as well, typically sold as cards containing wasp eggs that you place near areas of moth activity.
When the Smell Will Not Go Away
One of the most common complaints about mothballs is that their odor persists long after the mothballs themselves are gone. This is not your imagination. Both naphthalene and paradichlorobenzene are volatile organic compounds that adsorb readily onto porous surfaces: fabric, wood, drywall, carpet, insulation. In a home where mothballs were used liberally, the smell can linger for months or even years, because the chemicals slowly off-gas from these surfaces back into the indoor air.
Removing the odor requires ventilation and time. Opening windows, running fans, and using air purifiers with activated carbon filters can help. For heavily contaminated fabrics, washing alone may not be enough; dry cleaning with a solvent can be more effective. For structural contamination (mothball odor embedded in walls, floors, or subflooring from years of heavy use), professional remediation may be necessary. Some homes where mothballs were scattered throughout living spaces for years have required removal and replacement of contaminated building materials.
This persistence is itself a health concern. If you can smell mothballs in a home, you are inhaling the chemical. The nose can detect naphthalene at concentrations below the levels considered harmful for short-term exposure, so a faint whiff is not necessarily dangerous. But a strong, pervasive mothball odor throughout a home indicates concentrations that are likely above the chronic exposure thresholds worth worrying about, especially if children, elderly adults, or people with respiratory conditions live there. The smell is not just unpleasant; it is a crude exposure monitor telling you the chemical is in the air.
Legal Status Around the World
Naphthalene mothballs have been banned or restricted in the European Union since 2008 due to concerns about toxicity and environmental contamination. Within the EU, paradichlorobenzene formulations are still available but face increasing scrutiny. In the United States, both naphthalene and paradichlorobenzene mothballs remain legal but are regulated as pesticides by the EPA, which means their labels carry legal force: using them in a way inconsistent with the label is a federal violation. In practice, enforcement of mothball misuse is rare, but the legal framework exists.
Australia, Canada, and several Asian countries have varying regulations. In some regions, naphthalene mothballs remain widely available and heavily used, while in others they have been effectively replaced by paradichlorobenzene or by non-chemical alternatives. The global trend is clearly toward restriction, driven by the accumulating evidence that chronic low-level exposure is more harmful than earlier generations assumed and by the availability of effective alternatives that carry far less risk.