Mothballs are frequently misused by homeowners who believe the strong odor repels garden pests like squirrels, rabbits, or deer. This practice is unsafe for humans and pets and illegal under federal law because mothballs are highly concentrated, registered pesticides. The active ingredients are designed to kill insects through toxic fumes, not to be broadcast into the open environment as a repellent. Applying these chemicals outside contaminates soil and water, creating a serious hazard where food is grown or children and animals play.
The Chemical Composition and Intended Use of Mothballs
Mothballs contain high concentrations of one of two active ingredients: naphthalene or paradichlorobenzene (PDCB). These compounds are volatile solids that slowly convert directly into a toxic gas, a process known as sublimation. This gaseous state allows the product to function as a fumigant.
The product is registered specifically to control clothes moths and their larvae, which feed on natural fibers in stored items. To be effective, the label instructs users to place the mothballs exclusively inside closed, airtight containers, such as trunks or sealed garment bags. This procedure ensures the toxic vapor builds up to a concentration sufficient to kill the insects. Using mothballs outside of these sealed conditions renders their fumigant purpose ineffective and creates an environmental release.
Why Outdoor Application is Prohibited by Regulations
Mothballs are classified and regulated by the U.S. Environmental Protection Agency (EPA) as insecticides. Under federal law, the pesticide label is a binding agreement, meaning it is illegal to use the product in any manner inconsistent with its instructions. The official labeling expressly prohibits using mothballs outdoors or anywhere outside a tightly sealed container.
The functional design of the mothball explains this prohibition, as they are formulated for slow dissipation in a confined space. When placed in open air, the chemicals rapidly volatilize and disperse, failing to concentrate enough to repel animals effectively. This misuse simply releases the toxic compounds directly into the atmosphere, soil, and water systems. Using them as a general animal repellent, such as for snakes or rodents, is explicitly forbidden because it violates the approved use outlined on the product’s registration.
Specific Toxicity Risks to Humans, Pets, and Soil
The primary danger of outdoor application is direct exposure to humans, pets, and the surrounding environment. Ingestion is a significant risk, particularly for young children and domestic animals who may mistake the white spheres for candy or toys. Ingesting naphthalene mothballs can lead to severe gastrointestinal distress, seizures, and hemolytic anemia, a condition caused by the premature destruction of red blood cells.
The vapors released outdoors also pose a serious health hazard through inhalation, as smelling the product indicates exposure to the pesticide. Acute exposure can cause symptoms like headaches, nausea, dizziness, and irritation of the eyes and respiratory passages. Long-term exposure to naphthalene vapors is associated with more severe outcomes, including liver damage and neurological effects.
When mothballs dissolve in the garden, the compounds become soil and water contaminants. Naphthalene is a polycyclic aromatic hydrocarbon (PAH) that adheres strongly to organic matter in the ground. The chemical can persist for weeks or longer, depending on the soil composition. This contamination harms beneficial soil organisms and can be absorbed by plants, making homegrown produce unsafe for consumption.
Effective and Approved Methods for Garden Pest Control
Gardeners seeking to manage pests should adopt Integrated Pest Management (IPM) strategies that prioritize safety and environmental health.
Physical Exclusion
Physical exclusion is a non-chemical method for deterring larger animals like rabbits and deer. Installing sturdy fences, netting, or floating row covers creates a physical barrier that prevents pests from accessing vulnerable plants.
Cultural and Biological Controls
Cultural controls, such as rotating crops and maintaining healthy soil structure, make plants more resistant to infestation and disease. Introducing or encouraging natural predators is a biological control method that uses beneficial insects like ladybugs, praying mantises, or parasitic wasps to manage harmful populations.
Organic Products
For managing insect pests, approved organic products provide targeted control without widespread environmental harm. Neem oil, a naturally derived insecticide, effectively treats common issues like aphids and mealybugs. Diatomaceous earth, a finely ground powder, works by physically damaging the exoskeletons of crawling insects and is safe for use around food crops. Aromatic herbs such as lavender, rosemary, and thyme can also be planted strategically to help naturally repel certain insects.