Arsenic, Inorganic

CASRN 7440-38-2 | DTXSID4023886

Updated Problem Formulation and Systematic Review Protocol for the Inorganic Arsenic IRIS Assessment

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In May 2019, EPA released the Updated Problem Formulation and Systematic Review Protocol for the Inorganic Arsenic IRIS Assessment for a 30-day public comment period. The IRIS Program is updating its 1988 Toxicological Review of Inorganic Arsenic. Given the size and complexity of the evidence base for this chemical, input on the scope of this assessment has been sought from the National Academy of Sciences, Engineering, and Medicine (NAS), EPA Program and Regional Offices, other federal agencies, and public stakeholders to help focus the objectives of the assessment and ensure it is transparently conducted. On July 16, 2019, an NAS ad hoc committee will evaluate the revised scope of the assessment and determine whether the proposed methods are appropriate to synthesize the scientific evidence and develop conclusions.


U.S. EPA. Updated Problem Formulation and Systematic Review Protocol for the Inorganic Arsenic IRIS Assessment. U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-19/049, 2019.

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Inorganic arsenic is used for hardening copper and lead alloys. It also is used in glass manufacturing as a decolorizing and refining agent, as a component of electrical devices, in the semiconductor industry, and as a catalyst in the production of ethylene oxide. Arsenic compounds are used as a mordant in the textile industry, for preserving hides, as medicinals, pesticides, pigments, and wood preservatives.

Arsenic is also found naturally in the environment and is typically present in soil and water at detectable levels. Sources of human exposure to inorganic arsenic include drinking water, diet, air, and soils (which can contain naturally occurring arsenic or contamination from anthropogenic sources). This draft IRIS health assessment addresses cancer and non-cancer human health effects that may result from chronic exposure to this chemical.


Date Description
01- 1988 EPA published the IRIS Health Hazard Assessment for Inorganic Arsenic.
02- 1999 NRC reviewed the 1988 IRIS assessment and the available health data for inorganic arsenic and made recommendations for updating the cancer assessment in Arsenic in Drinking Water.
03- 2001 NRC updated the NRC (1999) report and evaluated the toxicological risk and health effects of arsenic as relevant to the 2001 Arsenic Rule in Arsenic in Drinking Water – 2001 Update.
04- 2001 NRC reviewed the 2001 Primary Drinking Water Standard for inorganic Arsenic and made recommendations for applying epidemiologic data in the cancer health assessment.
05- 2003 EPA started a reassessment of the IRIS Toxicological Review.
06- Jul 2005 EPA released the draft IRIS inorganic arsenic assessment in July 2005 for public comment and peer review.
07- Jun 2007 Science Advisory Board (SAB) posted a response to the 2005 EPA reassessment of inorganic arsenic (cancer).
08- Oct 2008 Draft IRIS Toxicological Review for Inorganic Arsenic (Cancer) submitted to OMB for interagency review.
09- Jun 2009 EPA hosted an interagency science consultation on the draft IRIS Toxicological Review of Inorganic Arsenic (cancer).
10- Feb 2010 EPA released the revised draft IRIS inorganic arsenic assessment (cancer) for public comment and peer review, SAB announced public teleconference to conduct a quality review of the draft report to be held on November 22, 2010. [Federal Register Notice Oct 25, 2010], and SAB completed its review of the draft assessment.
11- 2011 Congress directed EPA to contract with the National Research Council (NRC) to review the draft assessment (cancer and noncancer).
12- Jan 2013 EPA held a public planning and scoping meeting for development of a new IRIS Toxicological Review of Inorganic Arsenic (cancer and noncancer).
13- 2013 EPA held eight science issues public webinars (Mar–July).
14- May 2013 EPA submitted a draft Assessment Development Plan (ADP) and preliminary assessment materials to NRC for review.
15- Nov 2013 NRC released the interim report, Critical Aspects of EPA’s IRIS Assessment of iAs and provided recommendations; NRC supported EPA’s plan.
16- Jun 2014 EPA held a public science meeting to present and encourage comments on the ADP, preliminary assessment materials, and key science issues.
17- Apr 2015 EPA released a revised ADP and other preliminary materials and held two public meetings (webinars).
18- Dec 2015 The National Academies of Science hosted a meeting on the review of EPA's IRIS Toxicological Assessment of Inorganic Arsenic (Preliminary Meeting Materials).
19- May 2019 EPA released the Updated Problem Formulation and Systematic Review Protocol for the IRIS inorganic Arsenic Assessment. EPA posted an errata sheet outlining an update that was made to the protocol and posted on this site on June 20, 2019. [Federal Register Notice May 28, 2019]
20- Jul 2019 EPA posted the summary of public comments document received on the IRIS inorganic arsenic protocol.
21- Oct 2023 EPA released an update to the IRIS inorganic arsenic protocol.


The IRIS Program will use the updated problem formulation and methods for conducting the systematic review and dose-response as described in the protocol to develop the draft assessment.

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