Uranium, natural

Overview

In February 2024, EPA released the Protocol for the Uranium IRIS Assessment (Oral) (Preliminary Assessment Materials) for a 30-day public review and comment period. As part of developing a draft IRIS assessment, EPA presents a protocol that describes the methodology for how the assessment will be conducted, including systematic review and dose-response. These could include strategies for literature searches, criteria for study inclusion or exclusion, considerations for evaluating study methods, information management for extracting data, approaches for synthesis within and across lines of evidence, and methods for derivation of toxicity values.

Background

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.

History/Chronology

Date	Description
Jan 2018	EPA released the IRIS Assessment Plan (IAP) for Uranium (Oral Reference Dose). [Federal Register Notice Jan 31, 2018]
Mar 2018	EPA hosted a public science meeting on March 22, 2018 to discuss preliminary assessment materials for uranium.
Apr 2019	EPA suspended the assessment in fiscal year 2019. It may be restarted as Agency priorities change.
Jun 2021	The assessment was unsuspended and announced in the June 2021 Outlook.
Feb 2024	EPA released the Protocol for the Uranium IRIS Assessment (Preliminary Assessment Materials). The deadline for comments is March 15, 2024. [Federal Register Notice Feb 14 2024]

Status

The IRIS Program will use the protocol to develop the draft assessment.

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.

• Protocol for the Uranium IRIS Assessment (Oral) (Preliminary Assessment Materials) (PDF)  (175  pp, 2.4 MB, about PDF)

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Document Related Link(s)

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

HERO Project

• Literature Search References Sorted by Publication Year (Uranium)

Federal Register Notices

• Federal Register Notice: Feb 14, 2024

Docket

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