IRIS

Naphthalene

System	RfD (mg/kg-day)	Basis	PoD	Composite UF	Confidence
Other	2 x 10^-2	Decreased mean terminal body weight in males	NOAEL (ADJ): 7.1 x 10¹ mg/kg-day	3000	Low

System	RfC (mg/m³)	Basis	PoD	Composite UF	Confidence
Nervous, Respiratory	3 x 10^-3	Nasal effects: hyperplasia and metaplasia in respiratory and olfactory epithelium, respectively	LOAEL (HEC): 9.3 mg/m³	3000	Medium

Weight of Evidence for Cancer (PDF) (32 pp, 102 K) Last Updated: 09/17/1998

WOE Characterization	Framework for WOE Characterization
C (Possible human carcinogen)	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1986)
Carcinogenic potential cannot be determined	Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1996)

Basis:

Using criteria of the 1986 Guidelines for Carcinogen Risk Assessment, naphthalene is classified in Group C, a possible human carcinogen. This is based on the inadequate data of carcinogenicity in humans exposed to naphthalene via the oral and inhalation routes, and the limited evidence of carcinogenicity in animals via the inhalation route. Using the 1996 Proposed Guidelines for Carcinogen Risk Assessment, the human carcinogenic potential of naphthalene via the oral or inhalation routes "cannot be determined" at this time based on human and animal data; however, there is suggestive evidence (observations of benign respiratory tumors and one carcinoma in female mice only exposed to naphthalene by inhalation [NTP, 1992a]). Additional support includes increase in respiratory tumors associated with exposure to 1-methylnaphthalene.
This may be a synopsis of the full weight-of-evidence narrative.

Not assessed under the IRIS Program.

Not assessed under the IRIS Program.

Additional EPA toxicity information may be available by visiting the following sites:

Human Health Benchmarks for Pesticides (HHBP). This database provides human health benchmarks for pesticides that may be present in drinking water.
Office of Pesticide Programs Pesticide Chemical Search. This database provides links to health effects information and registration status for pesticides.
Chemistry Dashboard. This database provides information on chemical structures, experimental and predicted physicochemical, and toxicity data.

Naphthalene is being reassessed.

Assessment Manager(s): Andrew Kraft (kraft.andrew@epa.gov), Dahnish Shams (shams.dahnish@epa.gov)

Step	Assessment Materials Released to the Public	Release Date	Public Meeting Date
1	Problem Formulation Materials	07/2018	TBD
1	Preliminary Assessment Materials	03/2023	TBD
4	Public Comment Draft	TBD	TBD
4	Peer Review Draft	TBD	TBD
7	Post Final Assessment	TBD