IRIS

Naphthalene

CASRN 91-20-3 | DTXSID8020913

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (32 pp, 102 K) Last Updated: 09/17/1998

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

 


Reference Concentration for Inhalation Exposure (RfC) (PDF) (32 pp, 102 K) Last Updated: 09/17/1998

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

 

Cancer Assessment

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.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (32 pp, 102 K)

Not assessed under the IRIS Program.

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (32 pp, 102 K)

Not assessed under the IRIS Program.

Program Outlook Details

Public Assessment Materials Date
Problem Formulation Materials/IRIS Assessment Plan Jul-2018
Preliminary Assessment Materials/Systematic Review Protocol Nov-2022
Public Comment TBD
External Peer Review TBD
Post Final Assessment TBD

Note: Any future dates displayed in the table above should be considered estimates and are subject to change. Once the external peer review is complete, estimated dates for release of the final assessment will be published. For the latest information on the status of this assessment, please refer to the IRIS Program Outlook. To access assessment documents, meeting materials or other supporting documents related to this assessment, visit the Chemical Documents tab. For more information about the development process, visit the IRIS Process page.

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