Mothballs are small, solid pesticides containing one of two primary active ingredients: naphthalene or paradichlorobenzene. These chemicals slowly convert from a solid directly into a toxic gas, a process called sublimation, which creates the characteristic strong odor. The U.S. Environmental Protection Agency (EPA) registers these products only for a single purpose: to control clothes moths and other fabric pests. For the product to work effectively and safely, the pesticide fumes must be contained within an airtight space, such as a sealed chest or garment bag.
The Intended Target: Pests Mothballs Are Designed to Control
Mothballs are designed to control clothes moths, specifically the webbing clothes moth (Tineola bisselliella) and the casemaking clothes moth (Tinea pellionella), along with their destructive larvae. Some formulations may also target other fabric pests like silverfish and carpet beetles.
The mechanism requires the vaporized chemical to reach a lethal concentration within the sealed container. This high concentration of toxic fumes kills the pests or acts as a potent fumigant to prevent them from damaging stored items made of natural fibers like wool and silk.
Any use outside of an airtight container, such as placing them in open closets or drawers, allows the toxic gas to dissipate quickly, rendering the product ineffective. The label-approved use depends entirely on trapping the toxic gas in a small, enclosed area to achieve the necessary fumigating effect.
Misapplication for Wildlife Control
Despite their narrow intended use, mothballs are frequently and improperly used in attempts to repel a wide variety of outdoor wildlife. This includes common nuisance species such as squirrels, mice, rats, skunks, deer, and snakes. This practice is based on the mistaken belief that the strong, unpleasant odor will effectively drive away larger animals from yards, gardens, or attics.
Mothballs are generally ineffective as a wildlife repellent because they cannot achieve the necessary concentration in open air. When scattered outdoors, the toxic vapors quickly disperse and become highly diluted by the wind and rain. Wildlife often ignores the mild, dispersed scent or simply learns to move around the small area where the mothballs are placed. Even if the smell is initially annoying, animals frequently become accustomed to the odor over time, making the mothballs useless as a deterrent.
Animals like raccoons, mice, and rats that have established a nest or found a reliable food source are particularly unlikely to be repelled. In some cases, animals may even consume the mothballs, mistaking them for food, which leads to severe poisoning. Relying on mothballs for wildlife control is a failed method, a waste of money, and a source of environmental contamination.
Toxicity and Regulatory Status
Using mothballs in any way that deviates from the product label, such as scattering them outdoors, is considered pesticide misuse and is illegal under federal law. The EPA strictly regulates mothballs, and the label specifies the exact conditions for safe and effective use. Applying them outside of a sealed container violates this regulation, posing significant health and environmental hazards.
The active chemicals, naphthalene and paradichlorobenzene, are toxic to humans and pets. When placed outdoors, they can be easily accessed and accidentally ingested by children or domestic animals, with even a single mothball causing serious harm. The chemicals also leach into the soil and water, leading to contamination, and the toxic vapors contribute to air pollution, harming non-target wildlife. Due to these substantial risks, regulatory bodies caution against any outdoor or off-label use of the product.