Naphthalene is released into ambient air via industrial gaseous and particulate emissions, tobacco use, and through consumer use. The data base concerning exposure of humans via inhalation and associated health effects is virtually nonexistent. Overexposure often results in acute hemolytic anemia and has been associated with cataract formation. There are no available dose-response data. In laboratory animals, two principal target tissues have been identified: non-ciliated bronchiolar epithelial (Clara) cells and eye tissue. The metabolite(s) that is responsible for Clara cell damage is unknown. There are no published studies involving inhalation exposure. Administration of naphthalene by routes other than inhalation has been shown to produce cataracts in rats, rabbits, and one mouse strain. Animal strains with pigmented eyes develop cataracts faster and more severely than albino strains. The likely causative agent is polyphenol oxydase, found only in pigmented eyes, that catalyzes the formation of 1,2-naphthoquione which binds to lens tissue. Negative results have been reported for gene mutations (Salmonella), unscheduled DNA synthesis in rat hepatocytes and microneuclei in mouse bone marrow. Limited teratology studies in rats and rabbits reported no gross abnormalities. In a single dose (300 mg/kg) study in mice, both maternal and fetal toxicity were reported.