Uranium, natural

CASRN 7440-61-1

IRIS Assessment Plan for Uranium (Scoping and Problem Formulation Materials)


EPA announced the availability of the IRIS Assessment Plan for Uranium (Oral Reference Dose) (Scoping and Problem Formulation Materials) for a 30-day public comment period. Information regarding the implementation of systematic review in the IRIS Program is described in a January 2018 Memo. EPA will convene an IRIS Public Science Meeting (Webinar Only) to discuss this chemical on March 22, 2018.

NOTE: EPA has identified an incorrect docket number associated with the Uranium IAP in the Federal Register Notice announcement. The correct docket number is EPA-HQ-ORD-2017-0747. EPA is working to correct this issue. If you have an issue providing your comments, please contact Dahnish Shams, at


In January 2018, EPA released the IRIS Assessment Plan for Uranium (Oral Reference Dose) (Scoping and Problem Formulation Materials). An IRIS Assessment Plan , or IAP communicates to the public the plan for assessing each individual chemical and includes summary information on the IRIS Program’s scoping and initial problem formulation, objectives and specific aims for the assessment, and the PECO (Populations, Exposures, Comparators, and Outcomes) criteria that outlines the evidence considered most pertinent to the assessment; and identification of key areas of scientific complexity. The PECO provides the framework for developing literature search strategies and inclusion/exclusion criteria, particularly with respect to evidence stream (i.e., human, animal, mechanistic), exposure measures and outcome measures.


U.S. EPA. IRIS Assessment Plan for Uranium (Scoping and Problem Formulation Materials). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-17/787, 2018.


Paul White,  Ph:  202-564-1369,  Email:

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Uranium is a naturally occurring radioactive element which in nature is a mixture of three isotopes: 234U, 235U, and 238U. The most common isotope, 238U, makes up a majority natural uranium. Uranium is enriched by processes that remove and concentrate 235U, with the remaining uranium being termed "depleted." Enriched uranium is used in nuclear reactor fuel and in nuclear weapons; it is not a subject of this assessment. Due to its physical properties, depleted uranium is used as a counterbalance in aircraft applications, for shielding against ionizing radiation, and both in military armor and in armor penetrating munitions.

Environmental exposures to uranium include ingestion of soil, foods, surface water, or groundwater including ingestion of locally grown or foraged food. Uranium is naturally present in many soils with higher concentrations found in the western United States. Uranium mining, milling, and processing operations can release this element into the environment leading to elevated levels of uranium in affected soils and dusts. The general population is primarily exposed to uranium through intake of food and drinking water.


Date Description
Jan 2018EPA released the IRIS Assessment Plan (IAP) for Uranium (Oral Reference Dose).[Federal Register Notice Jan 31, 2018]


The IRIS Program will use the IAP to inform the subsequent development of a chemical-specific systematic review protocol.

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This download(s) is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy.

Federal Register Notices


Comments on the assessment may be submitted and reviewed using the Docket ID EPA-HQ-ORD-2017-0747

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