Arsenic, Inorganic

CASRN 7440-38-2 | DTXSID4023886

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (29 pp, 186 K) Last Updated: 09/01/1991

System RfD (mg/kg-day) Basis PoD Composite UF Confidence
Cardiovascular, Dermal 3 x 10-4 Hyperpigmentation, keratosis and possible vascular complications NOAEL : 8 x 10-4
3 Medium


Reference Concentration for Inhalation Exposure (RfC) (PDF) (29 pp, 186 K)
Not assessed under the IRIS Program.


Cancer Assessment

Weight of Evidence for Cancer (PDF) (29 pp, 186 K) Last Updated: 06/01/1995

WOE Characterization Framework for WOE Characterization
A (Human carcinogen) Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1986)
  • Based on sufficient evidence from human data. An increased lung cancer mortality was observed in multiple human populations exposed primarily through inhalation. Also, increased mortality from multiple internal organ cancers (liver, kidney, lung, and bladder) and an increased incidence of skin cancer were observed in populations consuming drinking water high in inorganic arsenic.
  • This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (29 pp, 186 K)

Oral Slope Factor: 1.5 per mg/kg-day
Drinking Water Unit Risk: 5 x 10 -5 per µg/L
Extrapolation Method: Time- and dose-related formulation of the multistage model
Tumor site(s): Dermal
Tumor type(s): Skin cancer (Tseng, 1977; Tseng et al., 1968; U.S. EPA, 1988)

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (29 pp, 186 K)

Inhalation Unit Risk: 4.3 x 10 -3 per µg/m3
Extrapolation Method: Absolute-risk linear model
Tumor site(s): Respiratory
Tumor type(s): Lung cancer (Brown and Chu, 1983a,b,c; Lee-Feldstein, 1983; Higgins, 1982; Enterline and Marsh, 1982)

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

Arsenic, Inorganic is being reassessed.

Assessment Manager(s): JaniceS Lee (

Step Assessment Materials Released to the Public Release Date Public Meeting Date
1 Problem Formulation Materials 11/2012 01/2013
1 Preliminary Assessment Materials 05/2019 07/2019
4 Public Comment Draft 10/2023 TBD
4 Peer Review Draft 10/2023 12/2023
7 Post Final Assessment TBD

Please note: Any future dates displayed under Release Date are estimates and subject to change.

You will need Adobe Reader to view some of the files on this page. See EPA’s PDF page to learn more.

Quick Check