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Thallium carbonate (CASRN 6533-73-9)

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0112

Thallium carbonate; CASRN 6533-73-9

Health assessment information on a chemical substance is included in IRIS only after a comprehensive review of chronic toxicity data by U.S. EPA health scientists from several Program Offices and the Office of Research and Development. The summaries presented in Sections I and II represent a consensus reached in the review process. Background information and explanations of the methods used to derive the values given in IRIS are provided in the Background Documents.

STATUS OF DATA FOR Thallium carbonate

File First On-Line 01/31/1987

Category (section)
Status
Last Revised
Oral RfD Assessment (I.A.) on-line 09/01/1990
Inhalation RfC Assessment (I.B.) no data
Carcinogenicity Assessment (II.) on-line 09/01/1990

_I.  Chronic Health Hazard Assessments for Noncarcinogenic Effects

_I.A. Reference Dose for Chronic Oral Exposure (RfD)

Substance Name — Thallium carbonate
CASRN — 6533-73-9
Last Revised — 09/01/1990

The oral Reference Dose (RfD) is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Please refer to the Background Document for an elaboration of these concepts. RfDs can also be derived for the noncarcinogenic health effects of substances that are also carcinogens. Therefore, it is essential to refer to other sources of information concerning the carcinogenicity of this substance. If the U.S. EPA has evaluated this substance for potential human carcinogenicity, a summary of that evaluation will be contained in Section II of this file.

__I.A.1. Oral RfD Summary

Critical Effect
Experimental Doses*
UF
MF
RfD

Increased levels
of SGOT and LDH

Rat Oral Subchronic
Study

U.S. EPA, 1986

NOAEL: 0.25 mg/kg/day
(Tl2SO4) (converted
to 0.23 mg/kg/day
Tl2CO3)

LOAEL: None

3000
1
8E-5
mg/kg/day

*Conversion Factors: 0.25 mg/kg/day Tl2SO4 = 0.20 mg/kg/day Tl; 0.20 mg/kg/day Tl x [molecular weight of Tl2CO3 (469) divided by the molecular weight of Tl2 (408.7)] = 0.23 mg/kg/day Tl2CO3.

__I.A.2. Principal and Supporting Studies (Oral RfD)

U.S. EPA. 1986. Subchronic (90-day) toxicity of thallium sulfate in Sprague- Dawley rats. Office of Solid Waste, Washington, DC.

In a 90-day subchronic study, Sprague-Dawley rats (20/sex/group) were treated by gavage with 0, 0.01, 0.05, or 0.25 mg/kg/day of an aqueous solution of thallium sulfate (approximately 0, 0.004, 0.02, or 0.10 mg Tl/kg/day). Data generated from this study included body and organ weights, food consumption, hematology and clinical chemistry parameters, neurotoxicologic examinations, ophthalmologic examinations, and histopathology and neuropathology. No mortality was observed, but apparent dose-related increases in the incidence of alopecia, lacrimation, and exophthalmos were observed throughout the study. No differences between the control groups and groups receiving thallium sulfate were observed in body weights, body weight gains, food consumption, or absolute and relative organ weights. Moderate dose-related changes were observed in some blood chemistry parameters: increased SGOT, LDH, and sodium levels, and decreased blood sugar levels. The only grossly observed finding at necropsy thought to be treatment-related was alopecia, especially in female rats; however, microscopic evaluations did not reveal any histopathologic alterations. Based on the results of this study the highest dose, 0.25 mg/kg/day thallium sulfate (0.10 mg/kg/day Tl), is considered a NOAEL. Using the molecular weight ratio of Tl2CO3 to Tl (469/204.4) for conversion, this NOAEL was converted to 0.23 mg/kg/day Tl2CO3.

__I.A.3. Uncertainty and Modifying Factors (Oral RfD)

UF — The UF of 3000 includes factors of 10 to extrapolate from subchronic to chronic data, 10 for intraspecies extrapolation and 10 to account for interspecies variability, and a factor of 3 to account for lack of reproductive and chronic toxicity data.

MF — None

__I.A.4. Additional Studies/Comments (Oral RfD)

Groups of rats (5/sex/dose) were fed diets containing nominal concentrations of thallium acetate of 0, 5, 15, or 50 ppm (Downs et al., 1960). An additional group (30 ppm) was added after the study had been initiated (time not specified). Animals were allowed ad lib access to these diets for 15 weeks. The 50 ppm level resulted in 100% mortality by week 5. The 30 ppm level resulted in 100% mortality by week 9. By week 15, 4/10 control animals died (2/sex), making interpretation of survival in remaining dose groups difficult (15 ppm, 3/5 males and 1/5 females died; 5 ppm, 2/6 males and 0/4 females died). At termination, the only gross finding was alopecia in the 15 and 30 ppm groups. The authors stated that there was a slight increase in kidney weight (doses not specified, data not shown). The authors reported that histopathologic evaluations did not indicate treatment-related pathology.

Male Wistar rats (10/group) were administered drinking water containing 10 ppm T1SO4 (approximately 0.7 mg T1/kg/day based on reported thallium consumptions [270 ug T1/rat] and body weights [350-370 g] for 30 or 60 days; controls were pair fed. After 60 days of treatment, the following testicular effects were observed: disarrangement of the tubular epithelium, cytoplasmic vacuolation and distention of the smooth endoplasmic reticulum of the Sertoli cells, reduced testicular beta-glucuronidase activities, high concentrations of thallium in the testes, and reduced sperm motility (Formigli et al., 1986).

Eighty female Sprague-Dawley rats were administered drinking water containing thallium sulfate at a concentration of 10 mg Tl/L (approximately equivalent to a dose of 1.4 mg T1/kg/day based on reported T1 intakes and an assumption that the rats weighed 200 g). Mortality was 15 and 21% after 40 and 240 days of treatment, respectively. Functional and histopathological changes were observed in the peripheral nerves including changes in motor and sensory action potentials and histopathological changes in the sciatic myelin sheath and axonal destruction characterized by Wallerian degeneration, mitochondrial degeneration, neurofilamentous clustering, and elevated lysozomal activity (Manzo et al., 1983).

__I.A.5. Confidence in the Oral RfD

Study — Low
Database — Low
RfD — Low

Confidence in the critical study is rated low because of uncertainties in the results (i.e., vehicle vs. control differences) and because supporting studies show adverse health effects at doses slightly higher than the NOAEL. The data base provided only one subchronic study and some anecdotal human data, thus, a low confidence was assigned. Until additional chronic and reproductive studies are available, confidence in the RfD is considered low.

__I.A.6. EPA Documentation and Review of the Oral RfD

Source Document — This assessment is not presented in any existing U.S. EPA document.

Other EPA Documentation — U.S. EPA, 1986

Agency Work Group Review — 08/05/1987, 04/21/1988

Verification Date — 04/21/1988

Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the RfD for Thallium carbonate conducted in September 2002 identified one or more significant new studies. IRIS users may request the references for those studies from the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.

__I.A.7. EPA Contacts (Oral RfD)

Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general, at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov (internet address).

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_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)

Substance Name — Thallium carbonate
CASRN — 6533-73-9

Not available at this time.

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_II.  Carcinogenicity Assessment for Lifetime Exposure

Substance Name — Thallium carbonate
CASRN — 6533-73-9
Last Revised — 09/01/1990

Section II provides information on three aspects of the carcinogenic assessment for the substance in question; the weight-of-evidence judgment of the likelihood that the substance is a human carcinogen, and quantitative estimates of risk from oral exposure and from inhalation exposure. The quantitative risk estimates are presented in three ways. The slope factor is the result of application of a low-dose extrapolation procedure and is presented as the risk per (mg/kg)/day. The unit risk is the quantitative estimate in terms of either risk per ug/L drinking water or risk per ug/cu.m air breathed. The third form in which risk is presented is a drinking water or air concentration providing cancer risks of 1 in 10,000, 1 in 100,000 or 1 in 1,000,000. The rationale and methods used to develop the carcinogenicity information in IRIS are described in The Risk Assessment Guidelines of 1986 (EPA/600/8-87/045) and in the IRIS Background Document. IRIS summaries developed since the publication of EPA's more recent Proposed Guidelines for Carcinogen Risk Assessment also utilize those Guidelines where indicated (Federal Register 61(79):17960-18011, April 23, 1996). Users are referred to Section I of this IRIS file for information on long-term toxic effects other than carcinogenicity.

_II.A. Evidence for Human Carcinogenicity

__II.A.1. Weight-of-Evidence Characterization

Classification — D; not classifiable as to human carcinogenicity

Basis — Based on the lack of carcinogenicity data in animals and humans.

__II.A.2. Human Carcinogenicity Data

Inadequate. Medical records for 86 workers (sex and length of employment not reported) occupationally exposed to thallium at a magnesium seawater battery factory and 79 unexposed workers matched for age, length of employment, shift pattern, and type of work were examined (Marcus, 1985). No increase in incidence of benign neoplasms (site not specified) were observed. This study is limited by the examination of medical records only, lack of exposure quantitation, the small cohort, and unknown length of observation.

In another study, the health effects associated with exposure to thallium in 128 men (age 16 to 62 years) exposed for 1 to 42 years (average=19.5 years) in three cement manufacturing plants were reported (Schaller et al., 1980). Analyses of roasted pyrites and electro-filter dust confirmed the presence of thallium in various production areas in the plants. Urinary thallium was elevated in the workers. The health evaluation, consisting of a medical history and a physical exam, did not show any indication of thallium poisoning. However, this health evaluation was not adequate to detect any oncogenic response.

__II.A.3. Animal Carcinogenicity Data

None. Several subchronic and chronic animal studies on thallium and compounds are available; however, they were not designed to examine carcinogenic endpoints (reviewed in U.S. EPA, 1988).

__II.A.4. Supporting Data for Carcinogenicity

Thallium (I) salts were not mutagenic in reverse mutation assays using Salmonella typhimurium strains TA98, TA100, TA1535,and TA1538 and Escherichia coli strains B/r WP2 try and WP2 hcr try; use of hepatic homogenates was not specified (Kanematsu et al., 1980). Positive results were obtained at 0.001M for thallium nitrate in the Rec assay using Bacillus subtilis strains H17 and M45; use of hepatic homogenates was not specified (Kanematsu\et\al., 1980; Kada et al., 1980). Negative results were obtained in a screening of thallium nitrate for induction of mitotic gene coversion and reverse mutation in the yeast, Saccharomyces cerevisiae (Singh, 1983). Thallium nitrate produced negative effects on cell division in S. cerevisiae and E. coli. (Loveless et al., 1954). Cytotoxic levels (1000 ug/mL) of thallium acetate caused depressed DNA synthesis in Chinese hamster ovary cells (Garrett and Lewtas, 1983). Single-strand DNA breaks occurred in mouse and rat embryo fibroblasts exposed to thallium carbonate at E-6 to E-4M (Zasukhina et al., 1983). Thallium carbonate (0.5-0.005 ug/kg/day) was positive in a dominant lethal test in male white rats (Zasukhina et al., 1983).

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_II.B. Quantitative Estimate of Carcinogenic Risk from Oral Exposure

None

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_II.C. Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

None

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_II.D. EPA Documentation, Review, and Contacts (Carcinogenicity Assessment)

__II.D.1. EPA Documentation

Source Document — U.S. EPA, 1988

The 1988 Health and Environmental Effects Document for Thallium and Compounds is a preliminary draft and has not received Agency Review.

__II.D.2. EPA Review (Carcinogenicity Assessment)

Agency Work Group Review — 11/08/1989

Verification Date — 11/08/1989

Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the cancer assessment for Thallium carbonate conducted in September 2002 did not identify any critical new studies. IRIS users who know of important new studies may provide that information to the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.

__II.D.3. EPA Contacts (Carcinogenicity Assessment)

Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general, at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov (internet address).

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_VI.  Bibliography

Substance Name — Thallium carbonate
CASRN — 6533-73-9
Last Revised — 08/01/1991

_VI.A. Oral RfD References

Downs, W.L., J.K. Scott, L.T. Steadman and E.A. Maynard. 1960. Acute and subacute toxicity studies of thallium compounds. Am. Ind. Hyg. Assoc. 21: 399-406.

Formigli, L., R. Schelsi, P. Poggi, et al. 1986. Thallium-induced testicular toxicity in the rat. Environ. Res. 40(2): 531-539.

Manzo, L., R. Scelsi, A. Moglia, et al. 1983. Long-term toxicity of thallium in the rat. Proceed. 2nd Int. Conf., Chem. Toxicol. Clin. Chem. Met. p. 401- 405.

U.S. EPA. 1986. Subchronic (90-day) toxicity of thallium sulfate in Sprague-Dawley rats. Office of Solid Waste, Washington, DC.

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_VI.B. Inhalation RfC References

None

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_VI.C. Carcinogenicity Assessment References

Garrett, N.E. and J. Lewtas. 1983. Cellular toxicity in Chinese hamster ovary cell cultures. I. Analysis of cytotoxicity endpoints for twenty-nine priority pollutants. Environ. Res. 32: 455-465.

Kada, T., K. Hirano and Y. Shirasu. 1980. Screening of environmental chemical mutagens by the Rec-assay system with Bacillus subtilis. In: Chemical Mutagens: Principles and Methods for Their Detection, F. deSerrres and A. Hollaender, Ed. 6: 149-173.

Kanematsu, N., M. Hara and T. Kada. 1980. Rec assay and mutagenicity studies on metal compounds. Mutat. Res. 77: 109-116.

Loveless, L.E., E. Spoerl and T.H. Weisman. 1954. A survey of effects of chemicals on division and growth of yeast and Escherichia coli. J. Bacteriol. 68: 637-644.

Marcus, R.L. 1985. Investigation of a working population exposed to thallium. J. Soc. Occup. Med. 35(1): 4-9.

Schaller, K.H., G. Manke, H.J. Raithel, G. Buhlmeyer, M. Schmidt and H. Valentin. 1980. Investigations of thallium-exposed workers in cement factories. Int. Arch. Occup. Environ. Health. 47(3): 223-231.

Singh, I. 1983. Induction of reverse mutation and mitotic gene conversion by some metal compounds in Saccharomyces cerevisiae. Mutat. Res. 117: 149-152.

U.S. EPA. 1988. Health and Environmental Effects Document for Thallium and Compounds. Prepared by the Environmental Criteria and Assessment Office, Cincinnati, OH, for the Office of Solid Waste and Emergency Response, Washington, DC.

Zasukhina, G.D., I.M. Vasilyeva, N.I. Sdirkova, et al. 1983. Mutagenic effect of thallium and mercury salts on rodent cells with different repair activities. Mutat. Res. 124(2): 163-173.

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_VII.  Revision History

Substance Name — Thallium carbonate
CASRN — 6533-73-9

Date
Section
Description
03/31/1987 I.A.6 Documentation corrected
06/30/1988 I.A. RfD withdrawn
09/07/1988 I.A. Revised oral RfD summary added
06/01/1989 I.A.6. Work group review dates revised
09/01/1990 I.A. Text edited
09/01/1990 I.A.7. Secondary contact changed
09/01/1990 II. Carcinogen assessment on-line
09/01/1990 IV.F.1. EPA contact changed
09/01/1990 VI. Bibliography on-line
08/01/1991 VI.C. Kada et al. citation corrected
01/01/1992 IV. Regulatory actions updated
06/01/1992 V.B. Chemical formula corrected
04/01/1997 III., IV. V. Drinking Water Health Advisories, EPA Regulatory Actions, and Supplementary Data were removed from IRIS on or before April 1997. IRIS users were directed to the appropriate EPA Program Offices for this information.
12/03/2002 I.A.6., II.D.2. Screening-Level Literature Review Findings message has been added.

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_VIII.  Synonyms

Substance Name — Thallium carbonate
CASRN — 6533-73-9
Last Revised — 01/31/1987

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