Mothballs are a solid form of pesticide used to protect stored clothing and materials from damage caused by clothes moths and their larvae. They contain volatile organic compounds that slowly release a strong, pungent odor. When used in tightly enclosed spaces, they function as a fumigant insecticide. The two primary active ingredients are Naphthalene and Paradichlorobenzene (PDB).
The Primary Chemical Components
The composition of mothballs is centered around one of two chemicals. The older formulation relied heavily on Naphthalene, a hydrocarbon derived from coal tar or petroleum. Naphthalene is a white solid with a strong odor, but its use has diminished due to concerns over its flammability and higher toxicity profile.
The more common active ingredient in modern mothballs is Paradichlorobenzene (PDB). PDB is an organic compound often marketed in products designed as general deodorizers, but it is still a pesticide. This compound is less flammable than Naphthalene. Both compounds are crystalline solids that are nearly 100% active ingredient in the final product.
The Mechanism of Repulsion
The effectiveness of mothballs relies on a physical process called sublimation, the transition of a substance directly from a solid state into a gaseous state. Both Naphthalene and Paradichlorobenzene have weak intermolecular forces, allowing them to vaporize slowly at room temperature. When you smell mothballs, you are inhaling the vaporized form of the insecticide.
This continuous release of gas creates a concentrated vapor inside a sealed storage container. The toxic fumes must build up to a sufficient level to kill or repel clothes moths, their eggs, and larvae. If mothballs are not used in an airtight container, the gas rapidly dissipates, rendering them ineffective and releasing the chemical into the surrounding environment.
Health and Environmental Hazards
Mothballs are regulated as pesticides by the Environmental Protection Agency (EPA). This classification means that their usage is strictly controlled, and the label instructions for use in sealed containers are legally binding. Using mothballs outdoors or in open closets allows the toxic fumes to escape into the environment, potentially contaminating soil and water.
The primary health risk comes from inhaling the vapor, which can cause irritation of the eyes, nose, and throat, headaches, and nausea. Accidental ingestion is a major concern, particularly for children and pets, who may mistake the small balls for candy. Eating even a single mothball can lead to serious harm, including a condition called hemolytic anemia, especially with Naphthalene exposure. Safe handling requires that mothballs are only used as directed on the label.
Modern Alternatives and Safe Storage
Many people seek safer methods for protecting stored garments. Integrated Pest Management (IPM) for clothing begins with cleanliness, as moths are attracted to human smells, food stains, and dirty fibers. All items should be washed or dry cleaned before storage to eliminate any existing moth eggs or larvae.
Natural repellents offer an aromatic alternative to chemical fumigants. Effective options include:
- Cedarwood, which contains oils that naturally repel moths. The scent must be refreshed periodically to maintain effectiveness.
- Sachets filled with dried herbs and spices such as lavender, dried rosemary, or cloves.
- Storing clothes in airtight plastic bins or vacuum-sealed bags to prevent pests from accessing the fibers.
- Freezing garments for several days to kill any life stages of the clothes moth.