Naphthalene, the chemical that gives mothballs that strong, familiar scent, showed clear evidence of causing cancer in male and female laboratory rats in a two-year study by the National Toxicology Program headquartered at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C. The rats in the study were exposed by inhalation, just as most people are, in doses comparable to some human consumer and workplace exposures.
NIEHS-NTP Study Scientist Kamal Abdo said naphthalene was nominated for study by the National Institute of Occupational Safety and Health, the Occupational Safety and Health Administration, and the US Environmental Protection Agency all of which are represented on the NTP Executive Committee after some German workers exposed to naphthalene were found to have a variety of cancers including laryngeal, gastric, nasal, and colon cancer. Regulatory agencies will have the opportunity to review the study and current labeling and take regulatory action as appropriate, using other studies and data as well.
The most widely known use of naphthalene is in mothballs and bathroom deodorizers, but it also has a number of chemical manufacturing uses, and is used in veterinary medicine to control lice and as a disinfectant for lesions and incisions. It enters the human food chain when used on livestock that then ingest or inhale it. Naphthalene manufacture and use goes back at least to the early part of the 20th Century.