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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.
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.
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.
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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.
|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.|
Following the External Peer Review, the final assessment will be published on the IRIS database.
U.S. EPA. IRIS Toxicological Review of Thallium and Compounds (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-08/001, 2008.