Are Mothballs Toxic?
They are insecticides made to give off a toxic gas. The National Pesticide Information Center says mothballs, moth flakes, crystals and bars come in a solid form that slowly gives off a toxic gas that kills clothes moths and other insects, and that mothballs in the US contain very high concentrations of naphthalene or paradichlorobenzene as active ingredients. It says that when you smell mothballs, you are inhaling the insecticide.
For naphthalene, the Agency for Toxic Substances and Disease Registry says people who breathed in air containing it had irritation and inflammation in their noses, decreased lung function, headaches and confusion, or felt tired and dizzy, and that damage to red blood cells has also been reported. It says health effects may happen at air levels you cannot smell. The US Department of Health and Human Services concluded that naphthalene is reasonably anticipated to be a human carcinogen, the EPA classifies it as a possible human carcinogen, and IARC classifies it as possibly carcinogenic to humans.
How they are used matters. The center says mothballs are pesticides regulated by the EPA, that the label specifies exactly where and how they can legally be used, and that labels typically direct users to keep them in a tightly closed container. It says a common mistake is using containers that are not airtight, which lets the vapors escape and can lead to long-term exposure that may cause health problems, and that mothballs used outdoors against insects, snakes or other wildlife can harm pets and other animals and contaminate soil, plants and water. ATSDR adds that blankets or clothing stored with naphthalene should be aired outdoors and washed before use.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Medical referenceThe National Pesticide Information Center says mothballs, moth flakes, crystals and bars are insecticides that slowly give off a toxic gas, and that mothballs in the US contain very high concentrations of naphthalene or paradichlorobenzene. National Pesticide Information Center, Oregon State University ↗
- Medical referenceThe center says mothballs slowly turn from solids to toxic vapor, and that when you smell mothballs you are inhaling the insecticide. National Pesticide Information Center, Oregon State University ↗
- Government sourceATSDR says people who breathed in air containing naphthalene had nose irritation and inflammation, decreased lung function, headaches and confusion, or felt tired and dizzy, and that red blood cell damage has been reported. ATSDR, CDC ↗
- Government sourceATSDR says the US Department of Health and Human Services concluded naphthalene is reasonably anticipated to be a human carcinogen, the EPA classifies it as a possible human carcinogen, and IARC as possibly carcinogenic to humans. ATSDR, CDC ↗
- Medical referenceThe center says mothballs are pesticides regulated by the EPA, that using them in a way not specified by the label is illegal, and that labels typically direct users to place them in a tightly closed container. National Pesticide Information Center, Oregon State University ↗
- Medical referenceThe center says using mothballs in containers that are not airtight can lead to long-term exposure that may cause health problems, and that mothballs used outdoors can contaminate soil, plants and water. National Pesticide Information Center, Oregon State University ↗
- Government sourceATSDR says naphthalene mothballs should be enclosed in containers that prevent vapor escaping, and that blankets or clothing stored with naphthalene should be aired outdoors and washed before using. ATSDR, CDC ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.