Moth balls are small, solid pesticides designed and regulated for controlling clothes moths and other fabric pests. They are classified as insecticides and must be used strictly according to the directions provided on the product label. The Environmental Protection Agency (EPA) mandates their application only within sealed, airtight containers for indoor storage. This controlled environment is necessary to achieve the pest-killing effect while limiting human and pet exposure to the toxic fumes.
Chemical Composition and Intended Function
Moth balls typically contain one of two active ingredients: naphthalene or 1,4-dichlorobenzene, also known as paradichlorobenzene (PDB). Both are volatile organic compounds that work through sublimation, transitioning directly from a solid state into a toxic gas. The pesticidal action relies on the concentration of these vapors building up to a lethal level for the target insects. For the chemical to be effective, the vapors must be trapped within a tightly closed, non-ventilated container, such as a sealed storage chest or garment bag. If used in an open area, the vapors quickly dissipate, preventing the concentration from reaching a potent level.
Misconceived Outdoor Applications
Many people attempt to use moth balls outdoors as a broad-spectrum repellent for nuisance wildlife, a use that is neither approved nor effective. Common misguided applications include scattering the balls in gardens, flowerbeds, or beneath porches to deter burrowing animals like moles and voles. Individuals also try to use them to repel larger pests, such as squirrels, bats, and snakes. These applications are ineffective because the active ingredients must reach a high concentration for a pesticidal effect, which is impossible in the open air. Furthermore, the product label, which dictates legal pesticide use, does not permit using moth balls as a wildlife repellent.
Environmental and Health Hazards of Outdoor Use
Using moth balls outdoors transforms a regulated pesticide into a hazardous pollutant, violating federal law. When scattered on the ground, the solid chemicals leach into the soil and can contaminate groundwater. Naphthalene is classified by the EPA as a persistent, bioaccumulative, and toxic (PBT) chemical, meaning it resists environmental breakdown and accumulates in the ecosystem. The chemicals also contribute to air pollution as vapors are released directly into the environment, posing an inhalation risk to humans and pets.
Children and pets are at significant risk of poisoning, as the white, pellet-like moth balls can be mistaken for candy or small toys and ingested. Ingesting even a small amount of naphthalene can cause serious health issues, including hemolytic anemia, which destroys red blood cells. Extended exposure to the vapors may lead to eye and respiratory irritation, headaches, and nausea in humans. Naphthalene is also categorized as a possible human carcinogen by some health agencies.
The chemicals also pose a direct threat to non-target species, including beneficial insects, birds, and other garden wildlife. Paradichlorobenzene is known to be a neurotoxin, and its unregulated use outdoors exposes the environment to a dangerous compound. Any use of a registered pesticide inconsistent with the label instructions is illegal and subject to enforcement actions. This is because the product’s safety has only been evaluated for its intended use in sealed containers.
Safer Outdoor Pest Control Solutions
Effective and safe outdoor pest management relies on exclusion, habitat modification, and targeted, approved products. To deter burrowing animals like moles and voles, focus on removing their food source, such as treating your lawn for grubs using beneficial nematodes or milky spore. Another option is applying liquid repellents that contain castor oil, which upsets the digestive systems of these pests. These castor-oil products are non-toxic to wildlife and children when used as directed.
Preventing snakes involves eliminating the shelter and food sources that attract them. This means clearing brush piles, removing lumber stacks, keeping the grass mowed short, and controlling rodent populations. For active insect problems, consider using targeted, plant-based sprays formulated with natural oils, such as clove or cottonseed oil. For long-term control of rodents, setting up physical barriers, such as deep-set wire mesh fencing, can effectively block underground access.