Mothballs are a registered pesticide product, and while it is physically possible to scatter them outside, this practice is strongly discouraged and illegal due to significant environmental and public health risks. These small, solid chemicals are designed for a very specific use, and when applied incorrectly, they can contaminate soil and water, poison wildlife, and expose people to harmful fumes. Understanding the product’s chemistry and regulatory constraints explains why outdoor application should be avoided entirely.
Chemical Composition and Intended Use
Mothballs contain high concentrations of one of two active ingredients: naphthalene or paradichlorobenzene. These compounds are solid pesticides that do not melt but instead undergo a process called sublimation, transitioning directly into a toxic gas or fume at room temperature. The continuous release of this vapor is what makes the product effective against pests.
The United States Environmental Protection Agency (EPA) regulates mothballs as pesticides, and their labeling dictates a highly specific intended use. The product is designed exclusively to kill clothes moths, their eggs, and larvae, which feed on natural fibers like wool and silk. The label instructs users to place mothballs only inside tightly sealed, airtight containers, such as storage chests or garment bags. This enclosed environment allows the toxic fumes to build up to a concentration lethal to the fabric pests while preventing the chemicals from escaping.
Hazards of Outdoor Application and Regulatory Misuse
Scattering mothballs outdoors constitutes a misuse of a registered pesticide and creates numerous environmental and health hazards. When placed in gardens, lawns, or near foundations, the active ingredients are released directly into the open air and soil, where they dissipate quickly, rendering the pest control attempt ineffective. The toxic chemicals then leach into the ground, contaminating the soil and potentially running off into surface water or groundwater sources.
The outdoor use of mothballs poses a severe poisoning risk to non-target animals, including pets, livestock, and wildlife. The small, white pellets can be mistaken for food or candy by children and animals, leading to accidental ingestion. Ingesting naphthalene can cause severe gastrointestinal distress, liver damage, and hemolytic anemia, which involves the destruction of red blood cells.
Using mothballs in a manner inconsistent with the instructions printed on the label is a violation of federal law, specifically the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). This law requires that all pesticides be used only as directed on their packaging. Common misuses, such as scattering mothballs to repel unlisted pests like snakes, deer, skunks, or rodents, are illegal and subject to fines and enforcement action. Furthermore, the quick dissipation of the vapor in an open environment means the product fails to deliver the toxic concentration needed to repel or kill these larger animals.
Safer Alternatives for Pest Management
Since the goal of placing mothballs outside is often to repel unwanted wildlife or rodents, safer, legal alternatives should be employed instead. For managing common outdoor nuisance animals, exclusion methods are generally the most effective approach. This involves physically blocking access by installing wire mesh, fencing, or sealing entry points around a home’s foundation or deck.
Habitat modification is another highly effective non-chemical strategy. This includes removing potential food sources like fallen fruit or pet food left outdoors, and eliminating dense ground cover or debris piles where pests might nest. When a chemical solution is necessary, choose an EPA-approved repellent or pesticide specifically formulated and labeled for the target pest and for outdoor application. These labeled products have undergone testing to ensure they can be used effectively and safely without the widespread contamination risks associated with mothballs.
For protecting stored clothing from moths, the safest alternatives are non-toxic methods. Proper storage in airtight containers or vacuum-sealed bags eliminates the pest’s access to the fabric. Natural deterrents like cedar blocks or sachets containing dried lavender or rosemary are also effective, as their oils naturally repel moths without posing the health risks of chemical mothballs.