Potassium cyanide (CASRN 151-50-8)
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0092
Potassium cyanide; CASRN 151-50-8
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 Potassium cyanide
File First On-Line 01/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 02/01/1996 |
Inhalation RfC Assessment (I.B.) | no data | |
Carcinogenicity Assessment (II.) | no data |
_I. Chronic Health Hazard Assessments for Noncarcinogenic Effects
_I.A. Reference Dose for Chronic Oral Exposure (RfD)
Substance Name — Potassium cyanide
CASRN — 151-50-8
Last Revised — 02/01/1996
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
|
---|---|---|---|---|
Rat Chronic Oral Howard and Hanzal, |
NOAEL: 10.8 mg/kg/day cyanide (CN) converted to 27.0 mg/kg/day of potassium cyanide |
100
|
5
|
5E-2
mg/kg/day |
Rat Subchronic to Philbrick et al., 1979 |
LOAEL: 30 mg/kg/day cyanide (75 mg/kg/day potassium cyanide) |
* Conversion Factors: molecular weight conversion factor = 65/26 [MW KCN = 65; MW CN = 26]
__I.A.2. Principal and Supporting Studies (Oral RfD)
Howard, J.W. and R.F. Hanzal. 1955. Chronic toxicity to rats of food treated with hydrogen cyanide. Agric. Food Chem. 3: 325-329.
Philbrick, D.J., J.B. Hopkins, D.C. Hill, J.C. Alexander and R.G. Thomson. 1979. Effects of prolonged cyanide and thiocyanate feeding in rats. J. Toxicol. Environ. Health. 5: 579-592.
Since potassium is present in very high levels in food and the environment, an RfD of 3.8 mg/day for potassium cyanide, based on cyanide content, is recommended.
Potassium cyanide is soluble in water and dilute acid (which includes the gastric environment) and is readily hydrolyzed to 1 molar equivalent of cyanide and 1 molar equivalent of potassium (Hartung, 1982).
In this 2-year dietary study, rats (10/sex/group) were administered food fumigated with hydrogen cyanide. The average daily concentrations were 73 and 183 mg CN/kg diet. From the data reported on food consumption and body weight, daily estimated doses were 4.3 mg and 10.8 mg CN/kg bw. The average food cyanide concentrations were estimated based on the authors' data for concentration at the beginning and end of each food preparation period and by assuming a first-order rate of loss for the intervening period. There were no treatment-related effects on growth rate, no gross signs of toxicity, and no histopathologic lesions.
Studies by Philbrick et al. (1979) showed decreased weight gain and thyroxin levels and myelin degeneration in rats at 30 mg/kg/day CN. Other chronic studies either gave higher effect levels or used the subcutaneous route (Crampton et al., 1979; Lessell, 1971; Hertting et al., 1960). Human data do not provide adequate information from which to derive an RfD because effective dose levels of chronically ingested CN are not documented. Therefore, the study of Howard and Hanzel (1955) provides the highest NOAEL, 10.8 mg/kg/day for CN, and is chosen for the derivation of an RfD for CN of 1.5 mg/day or 0.02 mg/kg/day.
Cyanide is metabolized extensively in the liver, indicating that the only relevant route of administration for quantitative risk assessment in the derivation of an oral ADI is the oral route of administration.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — According to the U.S. EPA (1985), an uncertainty factor of 100 is used to derive the ADI (10 for species extrapolation, 10 for sensitive population).
MF — A modifying factor of 5 is used to account for the apparent tolerance to cyanide when it is ingested with food rather than when it is administered by gavage or by drinking water.
__I.A.4. Additional Studies/Comments (Oral RfD)
Decreased protein efficiency ratio was produced by dietary cyanide treatment of rats during gestation, lactation, and postweaning growth phase in the Tewe and Maner (1981a) experiment; the dose level of cyanide (10.6 mg/kg/day) producing that effect is slightly lower than the currently accepted NOAEL of 10.8 mg/kg/day (U.S. EPA, 1985). Furthermore, Tewe and Maner (1981b) tested sows. Possible effects observed at about 9.45 mg/kg/day were proliferation of glomerular cells of the kidneys and reduced activity of the thyroid glands in the gilts. However, the number of animals in this experiment was very small. A Japanese study (Amo, 1973) indicated that 0.05 mg/kg/day of cyanide obtained from drinking water decreased the fertility rate and survival rate in the F1 generation and produced 100% mortality in the F2 generation in mice. However, these data are not consistent with the body of available literature.
__I.A.5. Confidence in the Oral RfD
Study — Medium
Database — Medium
RfD — Medium
The confidence in the study is medium because adequate records of food consumption and body weight were maintained, and animals of both sexes were tested at two doses for 2 years. The database is rated medium because a small but sufficient number of studies support the chosen study. Medium confidence in the RfD follows. Additional chronic/reproductive studies are needed to support a higher level of confidence in the RfD.
__I.A.6. EPA Documentation and Review of the Oral RfD
Source Document — U.S. EPA, 1984
Other EPA Documentation — U.S. EPA, 1985
Agency Work Group Review — 08/05/1985
Verification Date — 08/05/1985
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 potassium cyanide conducted in August 2003 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).
_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)
Substance Name — Potassium cyanide
CASRN — 151-50-8
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Potassium cyanide
CASRN — 151-50-8
This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.
_III.
[reserved]
_IV. [reserved]
_V. [reserved]
_VI. Bibliography
Substance Name — Potassium cyanide
CASRN — 151-50-8
Last Revised — 01/01/1990
_VI.A. Oral RfD References
Amo, H. 1973. Effects of oral administration of cyanide and heavy metals in long term on breeding and chromosomes analyses of mice. Nagoya shiritsu Diagaku Igakkai Zasshi. 24(1): 48-66.
Crampton, R.F., I.F. Gaunt, R. Harris et al. 1979. Effects of low cobalamin diet and chronic cyanide toxicity. Toxicology. 12: 221-234.
Hartung, R. 1982. Cyanides and nitriles. In: Patty's Industrial Hygiene and Toxicology, 3rd revised ed., Vol. 2c, G.D. Clayton and F.E. Clayton, Ed. John Wiley and Sons, Inc., NY. p. 4845-4900.
Hertting, G., O. Kraupp, E. Schnetz and S. Weeketich. 1960. Untersuchungen uber die Folgen einer chronischen Verabreichung akut toxischer Dosen von Naturimcyanid an Hunden. Octa Pharmacol. Toxicol. 17: 27-43.
Howard, J.W. and R.F. Hanzal. 1955. Chronic toxicity for rats of food treated with hydrogen cyanide. Agric. Food Chem. 3: 325-329.
Lessell, S. 1971. Experimental cyanide optic neuropathy. Arch. Opthalmol. 86(2): 194-204.
Philbrick, D.J., J.B. Hopkins, D.C. Hill, J.C. Alexander and R.G. Thomson. 1979. Effects of prolonged cyanide and thiocyanate feeding in rats. J. Toxicol. Environ. Health. 5: 579-592.
Tewe, O.O. and J.H. Maner. 1981a. Long-term and carry-over effect of dietary inorganic cyanide (KNC) in the life cycle performance and metabolism of rats. Toxicol. Appl. Pharmacol. 58: 1-7.
Tewe, O.O. and J.H. Maner. 1981b. Performance and pathophysiological changes in pregnant pigs fed cassava diets containing different levels of cyanide. Res. Veter. Sci. 30: 147-151.
U.S. EPA. 1984. Health Effects Assessment for Cyanides. Prepared by the Office of Health and Environmental Assessment, Environmental Criteria Assessment Office, Cincinnati, OH for the Office of Emergency and Remedial Response, Washington, DC.
U.S. EPA. 1985. Drinking Water Criteria Document for Cyanides. Prepared by the Office of Health and Environmental Assessment, Environmental Criteria and Assessment, Cincinnati, OH for the Office of Drinking Water, Washington, DC.
_VI.B. Inhalation RfC References
None
_VI.C. Carcinogenicity Assessment References
None
_VII. Revision History
Substance Name — Potassium cyanide
CASRN — 151-50-8
Date |
Section |
Description |
---|---|---|
03/31/1987 | I.A.6. | Documentation corrected |
03/01/1988 | I.A.4. | Text revised |
03/01/1988 | III.A. | Health Advisory added |
01/01/1990 | I.A.4. | Add Philbrick et al. 1979 citation |
01/01/1990 | VI. | Bibliography on-line |
08/01/1990 | IV.F.1. | EPA contact changed |
01/01/1992 | I.A.7. | Primary contact changed |
01/01/1992 | IV. | Regulatory actions updated |
02/01/1996 | I.A.7. | Contact changed |
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. |
10/28/2003 | I.A.6 | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
Substance Name — Potassium cyanide
CASRN — 151-50-8
Last Revised — 01/31/1987
- 151-50-8
- Hydrocyanic Acid, Potassium Salt
- Potassium Cyanide