Naphthalene

Endpoint summary

Description of key information

Rats dermally exposed to a dose of 43 µg of 14C-naphthalene absorbed half of the radioactivity into the plasma  within 2.1 h, with an area-specific dose of 3.3 µg/cm2 applied in ethanol.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The following summary is partly quoted from the "Toxicological Profile for Naphthalene, 1 -Methylnaphthalene and 2 -Methylnaphthalene" published by U.S. Department of Health and Human Services (Public Health Service), Agency for Toxic Substances and Disease Registry (ASTR) in 2005 [ATSDR 2005]:

Dermal absorption and excretion

The only available study regarding dermal absorption shows that dermal absorption occurs in rats. Turkall et al. (1994) assessed the bioavailability of naphthalene following dermal treatment of male Sprague Dawley rats. Animals were exposed to 43 µg total of¹⁴C-naphthalene introduced into a shallow glass cap covering a 13-cm²area on the skin of each rat. Plasma half-lives of radioactivity in male rats following dermal exposure to¹⁴C-naphthalene were 2.1 h for absorption and 12.8 h for elimination. Plasma concentration reached a maximum 4 hours after start of exposure. The major excretion route of radioactivity in male rats dermally exposed to naphthalene was via the urine. Approximately 50% of the radioisotope was recovered in the urine within 12 h of dosing. Another 20-25% of the dose was collected between 12 and 24 h (urinary excretion during the 0-24 h collection period 63%). Expired air was the secondary route of excretion (13.6% of the initial dose). The percentage of the administered dose expired as CO₂was less than 0.02%. Results demonstrate that pure naphthalene applied dermally absorbs relatively quickly into plasma.Naphthalene-derived radioactivity was rapidly excreted into the urine. Between 70% and 87% of absorbed radioactivity was excreted as urinary metabolites, but another 6-14% was exhaled as parent compound. Several cases of naphthalene toxicity in neonates have been reported in which the proposed route of exposure was dermal. Each case involved the use of diapers which had been stored in contact with naphthalene (mothballs or naphthalene flakes). The authors proposed that the naphthalene was absorbed through the skin, causing haemolytic anaemia. It was suggested that this absorption may have been enhanced by the presence of oils which had been applied to the babies' skin. Inhalation of vapors from the treated diapers probably contributed to the total exposure.

[ATSDR 2005] Toxicological Profile for Naphthalene, 1-Methylnaphthalene, and 2-Methylnaphthalene No. 67, Agency for Toxic Substances and Disease Registry (ATSDR), Atlanta, Georgia 30333; U.S. Dep. Health & Human Services [http://www.atsdr.cdc.gov]