Thallium (I), soluble salts

Overview

Thallium compounds are used in the semiconductor industry, the manufacture of optic lenses and low-melting glass, low-temperature thermometers, alloys, electronic devices, mercury lamps, fireworks, and imitation germs, and clinically as an imaging agent in the diagnosis of certain tumors. EPA's assessment of noncancer health effects and carcinogenic potential of thallium compounds was last prepared and added to the IRIS database between 1988 and 1990. The IRIS program is preparing an assessment that will incorporate current health effects information available for thallium and compounds, and current risk assessment methods. The IRIS assessment for thallium compounds will consist of a Toxicological Review and IRIS Summary. The Toxicological Review is a critical review of the physiochemical and toxicokinetic properties of a chemical, and its toxicity in humans and experimental systems. The assessment will present reference values for the noncancer effects of thallium compounds (RfD and Rfc), and a cancer assessment. The Toxicological Review and IRIS Summary have been subject to Agency review, Interagency review, and external scientific peer review. The final product will reflect the Agency opinion on the overall toxicity of thallium and compounds.

Background

Thallium exists in monovalent (Tl⁺¹) and trivalent (Tl⁺³) states. Thallium is released to the environment through the combustion of fossil fuels, refinement of oil fractions, the smelting of ferrous and non-ferrous ores, and by some other industrial processes such as cement production and brick works. In the past, thallium was used as a depilatory agent and as a treatment for ringworm, venereal diseases, TB, and malaria. It was banned for use as a pesticide in the United States in 1972. Currently, thallium compounds are used in the semiconductor industry, the manufacture of optic lenses and low-melting glass, low-temperature thermometers, alloys, electronic devices, mercury lamps, fireworks, and imitation gems, and clinically as an imaging agent in the diagnosis of certain tumors.

History/Chronology

Date	Description
1987	IRIS assessments of thallium acetate, carbonate, chloride, nitrate, selenite, and sulfate, and thallic oxide posted on the IRIS database (RfD only).
1988	RfDs for thallium compounds revised.
1989	RfD for thallic oxide withdrawn from the IRIS database.
1990	Carcinogenicity assessments for thallium compounds added to the IRIS database.
1993	RfD for thallium selenite withdrawn from the IRIS database.
Feb 2008	EPA releases the draft document, IRIS Toxicological Review of Thallium, for public review and comment in a February 15, 2008 Federal Register notice.
Apr 2008	EPA announces the external peer review panel workshop in an April 8, 2008 Federal Register notice.
Sep 2009	EPA released the Final Toxicological Review (PDF) (136 pp, 964K) and accompanying Summary for Thallium and Compounds to the IRIS Web site.

Status

Following the External Peer Review, the final assessment will be published on the IRIS database.

Additional Information

Comments on the assessment may be submitted and reviewed using the e-Government Regulations.gov Web site. From the site, select Environmental Protection Agency and the keyword EPA-HQ-ORD-2008-0057 (for the docket ID) to comment on this report.

Contact Information

Octavia Conerly
by phone at: 202-566-1094
by fax at: 202-566-1140
by email at: conerly.octavia@epa.gov

Susan Rieth
by phone at: 703-347-8582
by fax at: 703-347-8699
by email at: rieth.susan@epa.gov

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.

• Toxicological Review of Thallium (External Review Draft) (PDF)  (86  pp, 462.9 KB, about PDF)
• Charge to External Peer Reviewers (PDF)  (3  pp, 20.5 KB, about PDF)
• Consolidated Comments from the External Peer Review (Final) (PDF)  (76  pp, 251.0 KB, about PDF)

If you have a disability and the format of any material on our web pages interferes with your ability to access the information, please reach out to us using the Contact Us about IRIS form for assistance. To enable us to respond in a manner most helpful to you, please indicate the nature of the accessibility problem, the web address of the requested material, your preferred format in which you want to receive the material (electronic format (ASCII, etc.), standard print, large print, etc.), and your contact information.

Document Related Link(s)

• Compilation of Reviewer Comments and Responses to Charge Questions (Reported by Midwest Research Institute) (PDF)  (10  pp, 42.0 KB, about PDF)
• Volume 1: Range Finding (14-Day Study) (PDF)  (55  pp, 27.7 MB, about PDF)
• Volume 2: Range Finding (90-Day Study) Part 1 (PDF)  (299  pp, 54.8 MB, about PDF)
• Volume 2: Range Finding - Part 2 (Appendix IV) (PDF)  (255  pp, 143.1 MB, about PDF)
• IRIS Toxicological Review of Thallium And Compounds (Final Report)

Federal Register Notices

• FR Notice: Apr 8, 2008
• FR Notice: Feb 15, 2008