1 

2 

3 

4 

5 

6 

7 

8 ACUTE EXPOSURE GUIDELINE LEVELS (AEGLs) 

9 FOR SELECTED CYANIDE SALTS 

10 

11 PROPOSED 

12 

13 Sodium Cyanide (CAS No. 143-33-9) 

14 NaCN 

15 

16 Potassium Cyanide (CAS No. 151-50-8) 

17 KCN 

18 

19 Calcium Cyanide (CAS No. 592-01-8) 

20 Ca(CN)2

21 

22 

23 

24 

25 

26 

27 

28 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 2 of 38 

1 

2 ACUTE EXPOSURE GUIDELINE LEVELS (AEGLs) 

3 FOR 

4 SELECTED CYANIDE SALTS 

5 

6 

7 

8 PROPOSED 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 3 of 38 

1 PREFACE 

2 

3 Under the authority of the Federal Advisory Committee Act (FACA) P. L. 92-463 of 1972, 

4 the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances 

5 (NAC/AEGL Committee) has been established to identify, review and interpret relevant toxicologic 

6 and other scientific data and develop AEGLs for high priority, acutely toxic chemicals. 

7 

8 AEGLs represent threshold exposure limits for the general public and are applicable to 

9 emergency exposure periods ranging from 10 minutes to 8 hours. Three levels C AEGL-1, AEGL-2 

10 and AEGL-3 C are developed for each of five exposure periods (10 and 30 minutes, 1 hour, 4 hours, 

11 and 8 hours) and are distinguished by varying degrees of severity of toxic effects. The three AEGLs 

12 are defined as follows: 

13 

14 AEGL-1 is the airborne concentration (expressed as parts per million or milligrams per cubic 

meter [ppm or mg/m3 15 ]) of a substance above which it is predicted that the general population, 

16 including susceptible individuals, could experience notable discomfort, irritation, or certain 

17 asymptomatic, non-sensory effects. However, the effects are not disabling and are transient and 

18 reversible upon cessation of exposure. 

19 

AEGL-2 is the airborne concentration (expressed as ppm or mg/m3 20 ) of a substance above 

21 which it is predicted that the general population, including susceptible individuals, could experience 

22 irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape. 

23 

AEGL-3 is the airborne concentration (expressed as ppm or mg/m3 24 ) of a substance above 

25 which it is predicted that the general population, including susceptible individuals, could experience 

26 life-threatening health effects or death. 

27 

28 Airborne concentrations below the AEGL-1 represent exposure levels that could produce 

29 mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or 

30 certain asymptomatic, non-sensory effects. With increasing airborne concentrations above each 

31 AEGL, there is a progressive increase in the likelihood of occurrence and the severity of effects 

32 described for each corresponding AEGL. Although the AEGL values represent threshold levels for 

33 the general public, including susceptible subpopulations, such as infants, children, the elderly, 

34 persons with asthma, and those with other illnesses, it is recognized that individuals, subject to 

35 unique or idiosyncratic responses, could experience the effects described at concentrations below the 

36 corresponding AEGL 

37 

38 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 4 of 38 

1 TABLE OF CONTENTS 

2 LIST OF TABLES ................................................................................................................ 6

3 1. INTRODUCTION........................................................................................................... 8

4 2. HUMAN TOXICITY DATA .......................................................................................... 10

5 3. ANIMAL TOXICITY DATA.......................................................................................... 10

6 4. SPECIAL CONSIDERATIONS ................................................................................... 10

7 4.1. Metabolism and Disposition ..............................................................................................................................10

8 4.2. Mechanism of Toxicity.......................................................................................................................................10

9 4.3. Structure Activity Relationships.......................................................................................................................10

10 5. DATA ANALYSIS FOR AEGL-1 ................................................................................ 11

11 5.1. Summary of Human Data Relevant to AEGL-1..............................................................................................11

12 5.2. Summary of Animal Data Relevant to AEGL-1 ..............................................................................................11

13 5.3. Derivation of AEGL-1........................................................................................................................................11

14 6. DATA ANALYSIS FOR AEGL-2 ................................................................................ 12

15 6.1. Summary of Human Data Relevant to AEGL-2..............................................................................................12

16 6.2. Summary of Animal Data Relevant to AEGL-2 ..............................................................................................12

17 6.3. Derivation of AEGL-2........................................................................................................................................12

18 7. DATA ANALYSIS FOR AEGL-3 ................................................................................ 13

19 7.1. Summary of Human Data Relevant to AEGL-3..............................................................................................13

20 7.2. Summary of Animal Data Relevant to AEGL-3 ..............................................................................................13

21 7.3. Derivation of AEGL-3........................................................................................................................................13

22 8. SUMMARY OF AEGLS .............................................................................................. 14

23 8.1. AEGL Values and Toxicity Endpoints .............................................................................................................14

24 8.2. Comparison with Other Standards and Guidelines ........................................................................................14

25 8.3. Data Adequacy and Research Needs ................................................................................................................17
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 5 of 38 

1 9. REFERENCES............................................................................................................ 18

2 APPENDIX A: DERIVATION OF AEGL VALUES FOR CYANIDE SALTS ..................... 20

3 APPENDIX B: TIME SCALING CALCULATION FOR HYDROGEN CYANIDE AEGL-1, 

4 AEGL-2, AND AEGL-3 ...................................................................................................... 24

5 APPENDIX C: DERIVATION SUMMARY TABLES FOR CYANIDE SALTS AEGLS...... 28

6 APPENDIX D: DERIVATION SUMMARY TABLES FOR HYDROGEN CYANIDE .......... 32

7 APPENDIX E: CATEGORY PLOTS FOR CYANIDE SALTS........................................... 36

8 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 6 of 38 

1 LIST OF TABLES 

2 

3 TABLE 1. CHEMICAL AND PHYSICAL PROPERTIES FOR SODIUM CYANIDE.............................................9

4 TABLE 2. CHEMICAL AND PHYSICAL PROPERTIES FOR POTASSIUM CYANIDE .....................................9

5 TABLE 3. CHEMICAL AND PHYSICAL PROPERTIES FOR CALCIUM CYANIDE..........................................9

6 TABLE 4. RAT ORAL LETHALITY DATA...............................................................................................................11

7 TABLE 5. AEGL-1 VALUES FOR CYANIDE SALTS* .............................................................................................12

8 TABLE 6. AEGL-2 VALUES FOR CYANIDE SALTS* .............................................................................................12

9 TABLE 7. AEGL-3 VALUES FOR CYANIDE SALTS* .............................................................................................13

10 TABLE 8. AEGL VALUES FOR METAL CYANIDE SALTS* .................................................................................14

11 TABLE 9. EXTANT STANDARDS AND GUIDELINES FOR SODIUM CYANIDE ..............................................14

12 TABLE 10. EXTANT STANDARDS AND GUIDELINES FOR POTASSIUM CYANIDE.....................................15

13 TABLE 11. EXTANT STANDARDS AND GUIDELINES FOR CALCIUM CYANIDE.........................................16
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 7 of 38 

1 SUMMARY 

2 

3 Sodium cyanide, potassium cyanide, and calcium cyanide are all simple inorganic cyanide salts 

4 with an almond-like odor. They may react with water or moist air to release toxic, corrosive, or 

5 flammable gases. Reaction with water may generate heat which will increase the concentration of 

6 HCN fumes in the air (HSDB, 2008a, b, c). 

7 

8 Even though the salts are solids, inhalation of dusts may result in ionization in the nasal or lung 

mucosal fluids to yield CN- 9 . The salts may also react with water in humid air and be inhaled as 

10 HCN. In both cases, there will be systemic absorption of cyanide ion, which is the toxic moiety. 

11 Cyanide inhibits cellular respiration by blocking electron transfer from cytochrome oxidase to 

12 oxygen, causing tissue hypoxia and cell death. Low levels or low dose rates of cyanide are tolerated 

13 by detoxicficaton by rhodanese to thiosulfate (Cohrssen, 2001). 

14 

15 In the absence of appropriate chemical-specific data for the title cyanides, the AEGL-1, AEGL-2, 

16 and AEGL-3 values for hydrogen cyanide (NRC, 2002) will be used to obtain AEGL-1, AEGL-2, 

17 and AEGL-3 values, respectively for the title cyanide salts. The use of hydrogen cyanide as a 

18 surrogate for the cyanide salts is deemed appropriate because qualitative (clinical signs) and 

19 quantitative (adjusted rat oral LD50 values) data suggest that the cyanide moiety is responsible for 

20 acute toxicity of the cyanide salts. The hydrogen cyanide AEGL values will be used as target values 

21 for calculating the concentrations of cyanide salt needed to generate the hydrogen cyanide AEGL 

22 values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole of 

23 NaCN and KCN will yield one mole of HCN, and one mole of Ca(CN)2 will yield two moles of 

24 HCN). 

25 

26 

27 The calculated values are listed in the table below. 

28 

AEGL VALUES FOR METAL CYANIDE SALTS* 

Compound Classification 10-min 30-min 1-hr 4-hr 8-hr

AEGL-1 5.0 mg/m3

 5.0 mg/m3 4.0 mg/m3 2.6 mg/m3 2.0 mg/m3

AEGL-2 34 mg/m3

 20 mg/m3 14 mg/m3 7.0 mg/m3 5.0 mg/m3

Sodium 

Cyanide 

AEGL-3 54 mg/m3

 42 mg/m3 30 mg/m3 17 mg/m3 13 mg/m3

AEGL-1 6.6 mg/m3

 6.6 mg/m3 5.3 mg/m3 3.5 mg/m3 2.7 mg/m3

AEGL-2 45 mg/m3

 27 mg/m3 19 mg/m3 9.3 mg/m3 6.6 mg/m3

Potassium 

Cyanide 

AEGL-3 72 mg/m3

 56 mg/m3 40 mg/m3 23 mg/m3 18 mg/m3

AEGL-1 4.7 mg/m3

 4.7 mg/m3 3.8 mg/m3 2.4 mg/m3 1.9 mg/m3

AEGL-2 32 mg/m3

 19 mg/m3 13 mg/m3 6.6 mg/m3 4.7 mg/m3

Calcium 

Cyanide** 

AEGL-3 51 mg/m3

 39 mg/m3 28 mg/m3 16 mg/m3 12 mg/m3

29 3⁄4 *These airborne concentrations will produce the equivalent AEGL values for hydrogen cyanide. 

30 3⁄4 ** Although the adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

31 compound) than would be expected on a molar basis for CN, the production of two moles of HCN was 

32 assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 8 of 38 

1 1. INTRODUCTION 

2 

3 Sodium cyanide, potassium cyanide, and calcium cyanide are all simple inorganic cyanide salts 

4 with an almond-like odor. They may react with water or moist air to release toxic, corrosive, or 

5 flammable gases. Reaction with water may generate heat which will increase the concentration of 

6 HCN fumes in the air (HSDB, 2008a, b, c). 

7 

8 Even though the salts are solids, inhalation of dusts may result in ionization in the nasal or lung 

mucosal fluids to yield CN- 9 . The salts may also react with water in humid air and be inhaled as 

10 HCN. In both cases, there will be systemic absorption of cyanide ion, which is the toxic moiety. 

11 Cyanide inhibits cellular respiration by blocking electron transfer from cytochrome oxidase to 

12 oxygen, causing tissue hypoxia and cell death. Low levels or low dose rates of cyanide are tolerated 

13 by detoxification by rhodanese to thiosulfate (Cohrssen, 2001). 

14 

15 Although hydrolysis rates were not located for the title cyanides, the rate of cyanide generation 

16 may be dependent on ambient temperature and humidity and the chemical structure of the cyanide. 

17 Hydrolysis reactions are as follows (Kirk-Othmer, 2008): 

18 

19 

20 Sodium Cyanide and Potassium Cyanide:

21 One mole of sodium cyanide or potassium cyanide may react with water or moisture to produce a 

22 maximum of one mole of hydrogen cyanide as follows: 

23 

24 NaCN + H2O 6 HCN + NaOH 

25 

26 KCN+ H2O 6 HCN + KOH 

27 

28 Calcium Cyanide:

29 One mole of calcium cyanide may react with water or moisture to produce a maximum of two 

30 moles of hydrogen cyanide as follows: 

31 

32 Ca(CN)2 + 2H2O 6 2HCN + Ca(OH)2

33 

34 

35 Sodium cyanide is a white crystalline solid, and may be prepared by heating sodium amide 

36 with carbon or by melting sodium chloride and calcium cyanamide together in an electric furnace. It 

37 is used for extracting gold and silver from ores, heat treating of metals, electroplating, various 

38 organic reactions, and the manufacturing of adiponitrile (Cohrssen, 2001). U.S. production was 

reported as “at least” 1.14 x 1011 grams in 1978, and U.S imports were reported as 2.77 x 107 39 pounds 

40 in 1986 (HSDB, 2008a). 

41 

42 Potassium cyanide, a white crystalline solid, is prepared by reaction of an aqueous solution of 

43 potassium hydroxide with hydrogen cyanide. It is used for fine silver plating, dyes and speciality 

44 products, and fumigation of fruit trees, ships, railway cars, and warehouses. U.S. production 

45 information was not available; however, U.S. imports were reported as 1,468,423 pounds in 1987 

46 (HSDB, 2008b). 

47 

48 Calcium cyanide is a white powder, and is prepared from lime, calcium oxide, coke, and 

49 nitrogen in an electric furnace. The commercial product is dark gray because of the presence of 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 9 of 38 

1 carbon. It is used in the extraction of precious metal ores, adsorption of gold complexes on carbon, 

2 as a fumigant, and a rodenticide (Cohrssen, 2001). U.S. production information was not available; 

3 however, U.S. imports were reported as 468,246 pounds in 1986 (HSDB, 2008c). 

4 

5 

6 Available physicochemical data for the title cyanides are presented in Tables 1, 2, and 3. 

7 

TABLE 1. Chemical and Physical Properties for Sodium Cyanide 

Parameter Value References 

Synonyms 

Cyanogran; Cyanide of sodium; Cymag; 

Hydrocyanic acid sodium salt; 

Cyanobrik; White cyanide 

Cohrssen, 2001 

Chemical formula NaCN HDSB, 2008a 

Molecular weight 49.0 HSDB, 2008a 

CAS Reg. No. 143-33-9 HSDB, 2008a 

Physical state White crystalline solid HSDB, 2008a 

Solubility in water 48 g/100 mL water at 10°C; forms HCN HSDB, 2008a 

Density /specific gravity 1.595 g/cu cm at 20 °C HSDB, 2008a 

Vapor pressure 1 mm Hg at 817 °C HSDB, 2008a 

Melting point 563 °C HSDB, 2008a 

Boiling point 1496 °C HSDB, 2008a 

Conversion factors 1 ppm = 2.0 mg/m3

1 mg/m3

 = 0.50 ppm 

8 

TABLE 2. Chemical and Physical Properties for Potassium Cyanide 

Parameter Value References 

Synonyms Hydrocyanic acid potassium salt Cohrssen, 2001 

Chemical formula KCN HDSB, 2008b 

Molecular weight 65.11 HSDB, 2008b 

CAS Reg. No. 151-50-8 HSDB, 2008b 

Physical state White crystalline solid HSDB, 2008b 

Solubility in water 100 g/100 mL water at >176°F; forms 

HCN HSDB, 2008b 

Density /specific gravity 1.55 at 20 °C HSDB, 2008b 

Melting point 634 °C HSDB, 2008b 

Conversion factors 1 ppm = 2.7 mg/m3

1 mg/m3

 = 0.38 ppm 

9 

TABLE 3. Chemical and Physical Properties for Calcium Cyanide 

Parameter Value References 

Synonyms Calcyanide; Cyanogas; Black Cyanide, 

aero; Calcium cyanide, tech grade Cohrssen, 2001 

Chemical formula Ca (CN)2 HDSB, 2008c 

Molecular weight 92.12 HSDB, 2008c 

CAS Reg. No. 592-01-8 HSDB, 2008c 

Physical state White powder, solid HSDB, 2008c 

Solubility in water “Soluble in water with gradual liberation 

of HCN” HSDB, 2008c 

Density /specific gravity 1.853 at 20 °C HSDB, 2008c 

Melting point 640 °C (Estimated by extrapolation 

because of decomposition) HSDB, 2008c 

Conversion factors 1 ppm = 3.8 mg/m3 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 10 of 38 

1 mg/m3 = 0.27 ppm 

1 

2 

3 

4 2. HUMAN TOXICITY DATA 

5 

6 No human inhalation toxicity data were located for sodium, potassium, or calcium cyanide. 

7 There are numerous reports of occupational exposure to hydrogen cyanide; these data are 

8 summarized in the AEGL Technical Support Document for hydrogen cyanide (NRC, 2002). 

9 

10 3. ANIMAL TOXICITY DATA 

11 

12 No animal inhalation toxicity data were located for sodium, potassium, or calcium cyanide. 

13 However, the inhalation toxicity data base for hydrogen cyanide is robust. Lethality data exist for 

14 dogs, rats, mice and rabbits, and non-lethal toxicity data exist for nonhuman primates, rats, and mice. 

15 These data are summarized in the AEGL Technical Support Document for hydrogen cyanide (NRC, 

16 2002). 

17 

18 

19 4. SPECIAL CONSIDERATIONS 

20 4.1. Metabolism and Disposition 

21 

22 Solid cyanide salts deposited on moist respiratory tract surfaces may hydrolyze and release 

23 absorbable cyanide. Another scenario would involve atmospheric hydrolysis of metal cyanides to 

24 hydrogen cyanide vapor. Metabolism and disposition information for hydrogen cyanide is 

25 summarized in the AEGL Technical Support Document for hydrogen cyanide (NRC, 2002). 

26 

27 4.2. Mechanism of Toxicity 

28 

29 HCN is a systemic poison that acts on the central nervous system. HCN interrupts cellular 

30 respiration by blocking electron transfer from cytochrome oxidase to oxygen. Tissue oxygen levels 

31 rise, resulting in increased tissue oxygen tension and decreased unloading for oxyhemoglobin. As a 

32 consequence, oxidative metabolism may slow to a point where it cannot meet metabolic demands. 

33 This is particularly critical in the brainstem nuclei where lack of an energy source results in central 

34 respiratory arrest and death. Cyanide can inhibit many other enzymes, particularly those that contain 

35 iron or copper, but cytochrome oxidase appears to be the most sensitive enzyme. Cyanide also 

36 stimulates the chemoreceptors of the carotid and aortic bodies to produce a brief period of 

37 hyperpnea. Cardiac irregularities may occur, but death is due to respiratory arrest (Cohrssen, 2001; 

38 Smith 1996). Brain lesions have been associated with exposure of animals to high concentrations of 

39 HCN (ATSDR 1997). 

40 

41 

42 4.3. Structure Activity Relationships

43 

44 As previously stated, there are no human or animal acute inhalation toxicity data for the title 

45 cyanide salts. However, acute oral toxicity data suggest both qualitatively (clinical signs) and 

46 quantitatively (rat LD50 values) that the cyanide moiety is responsible for acute toxicity of the 

47 cyanide salts. Cyanide-induced clinical effects are indistinguishable following inhalation or dermal 

48 exposure to HCN vapor, or oral exposure to the cyanide salts NaCN and KCN, for both humans and 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 11 of 38 

1 animals. Clinical signs include headaches, dizziness, nausea, inability to concentrate, thoracic 

2 oppression, palpitation, numbness, weakness, rapid pulse, face flushing, unconsciousness, and death 

3 (Cohrssen, 2001). 

4 

5 

6 Rat oral LD50 values support the contention that CN is the toxic moiety. These reported 

7 values and LD values adjusted for CN are presented in Table 4. The CN adjusted values for 

8 hydrogen, sodium, and potassium cyanides are comparable; whereas, the adjusted value for 

9 calcium cyanide is much greater (suggesting a less toxic compound) than would be expected on a 

10 molar basis for CN. This may be due to a slower hydrolysis rate, allowing for more efficient 

11 detoxification, relative to the other cyanide salts. [Although hydrolysis rates were not located, 

12 water solubility/reactivity is described as “forms hydrogen cyanide” for sodium and potassium 

13 cyanides (HSDB, 2008a; 2008b), and “gradually liberates hydrogen cyanide” for calcium 

14 cyanide (HSDB, 2008c)]. 

15 

TABLE 4. Rat oral lethality data 

Compound LD50 (mg/kg) Adjusted LD50 (mg/kg CN) Reference 

HCN 8.5 8.2 Cohrssen, 2001 

NaCN 15 7.9 Smyth et al., 1969 

KCN 16 6.4 IUCLID, 2000 

Ca(CN)2 39 22 Smyth et al., 1969 

16 

17 

18 

19 5. DATA ANALYSIS FOR AEGL-1 

20 5.1. Summary of Human Data Relevant to AEGL-1 

21 

22 No human data relevant to development of AEGL-1 values were identified. 

23 

24 5.2. Summary of Animal Data Relevant to AEGL-1 

25 

26 No animal data relevant to development of AEGL-1 values were identified. 

27 

28 5.3. Derivation of AEGL-1 

29 

30 In the absence of appropriate chemical-specific data for the title cyanides, the AEGL-1 

31 values for hydrogen cyanide (NRC, 2002) will be used to obtain AEGL-1 values for the title cyanide 

32 salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

33 because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that 

34 the cyanide moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide 

35 AEGL-1 values will be used as target values for calculating the concentrations of cyanide salt 

36 needed to generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 

37 mm Hg and complete hydrolysis. The AEGL-1 values for the cyanide salts are given in Table 5, 

38 calculations for these values are presented in Appendix A, and derivation summary tables for 

39 cyanide salts are in Appendix C. [For comparison, the calculations and derivation summary tables 

40 for hydrogen cyanide AEGL values are presented in Appendix B and Appendix D, respectively.] 

41 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 12 of 38 

TABLE 5. AEGL-1 VALUES FOR CYANIDE SALTS* 

 

Compound 10-min 30-min 1-hr 4-hr 8-hr

Sodium Cyanide 5.0 mg/m3 5.0 mg/m3 4.0 mg/m3 2.6 mg/m3 2.0 mg/m3

Potassium Cyanide 6.6 mg/m3 6.6 mg/m3 5.3 mg/m3 3.5 mg/m3 2.7 mg/m3

Calcium 

Cyanide** 

4.7 mg/m3 4.7 mg/m3 3.8 mg/m3 2.4 mg/m3 1.9 mg/m3

1 3⁄4 *These airborne concentrations will produce the equivalent AEGL values for hydrogen cyanide. 

2 3⁄4 ** Although the adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

3 compound) than would be expected on a molar basis for CN, the production of two moles of HCN was 

4 assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

5 

6 

7 

8 6. DATA ANALYSIS FOR AEGL-2 

9 6.1. Summary of Human Data Relevant to AEGL-2 

10 

11 No human data relevant to development of AEGL-2 values were identified. 

12 

13 6.2. Summary of Animal Data Relevant to AEGL-2 

14 

15 No animal data relevant to development of AEGL-2 values were identified. 

16 

17 6.3. Derivation of AEGL-2 

18 

19 In the absence of appropriate chemical-specific data for the title cyanides, the AEGL-2 

20 values for hydrogen cyanide (NRC, 2002) will be used to obtain AEGL-2 values for the title cyanide 

21 salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

22 because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that 

23 the cyanide moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide 

24 AEGL-2 values will be used as target values for calculating the concentrations of cyanide salt 

25 needed to generate the hydrogen cyanide AEGL values. Calculations are for 25 degrees C and 760 

26 mm Hg and assume complete hydrolysis. The AEGL-2 values for the cyanide salts are given in 

27 Table 6, calculations for these values are presented in Appendix A, and derivation summary tables 

28 for cyanide salts are in Appendix C. [For comparison, the calculations and derivation summary 

29 tables for hydrogen cyanide AEGL values are presented in Appendix B and Appendix D, 

30 respectively.] 

31 

32 

TABLE 6. AEGL-2 VALUES FOR CYANIDE SALTS* 

 

Compound 10-min 30-min 1-hr 4-hr 8-hr

Sodium Cyanide 34 mg/m3 20 mg/m3 14 mg/m3 7.0 mg/m3 5.0 mg/m3

Potassium Cyanide 45 mg/m3 27 mg/m3 19 mg/m3 9.3 mg/m3 6.6 mg/m3

Calcium 

Cyanide** 

32 mg/m3 19 mg/m3 13 mg/m3 6.6 mg/m3 4.7 mg/m3

33 3⁄4 *These airborne concentrations will produce the equivalent AEGL values for hydrogen cyanide. 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 13 of 38 

1 3⁄4 ** Although the adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

2 compound) than would be expected on a molar basis for CN, the production of two moles of HCN was 

3 assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

4 

5 

6 

7 7. DATA ANALYSIS FOR AEGL-3 

8 7.1. Summary of Human Data Relevant to AEGL-3 

9 

10 No human data relevant to development of AEGL-3 values were identified. 

11 

12 7.2. Summary of Animal Data Relevant to AEGL-3 

13 

14 No animal data relevant to development of AEGL-3 values were identified.

15 

16 

17 7.3. Derivation of AEGL-3

18 

19 In the absence of appropriate chemical-specific data for the title cyanides, the AEGL-3 

20 values for hydrogen cyanide (NRC, 2002) will be used to obtain AEGL-3 values for the title cyanide 

21 salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

22 because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that 

23 the cyanide moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide 

24 AEGL-3 values will be used as target values for calculating the concentrations of cyanide salt 

25 needed to generate the hydrogen cyanide AEGL values. Calculations are for 25 degrees C and 760 

26 mm Hg and assume complete hydrolysis. The AEGL-3 values for the cyanide salts are given in 

27 Table 7, calculations for these values are presented in Appendix A, and derivation summary tables 

28 for cyanide salts are in Appendix C. [For comparison, the calculations and derivation summary 

29 tables for hydrogen cyanide AEGL values are presented in Appendix B and Appendix D, 

30 respectively.] 

31 

32 

TABLE 7. AEGL-3 VALUES FOR CYANIDE SALTS* 

 

Compound 10-min 30-min 1-hr 4-hr 8-hr

Sodium Cyanide 54 mg/m3 42 mg/m3 30 mg/m3 17 mg/m3 13 mg/m3

Potassium Cyanide 72 mg/m3 56 mg/m3 40 mg/m3 23 mg/m3 18 mg/m3

Calcium 

Cyanide** 

51 mg/m3 39 mg/m3 28 mg/m3 16 mg/m3 12 mg/m3

33 3⁄4 *These airborne concentrations will produce the equivalent AEGL values for hydrogen cyanide. 

34 3⁄4 ** Although the adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

35 compound) than would be expected on a molar basis for CN, the production of two moles of HCN was 

36 assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

37 

38 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 14 of 38 

1 8. SUMMARY OF AEGLS 

2 8.1. AEGL Values and Toxicity Endpoints 

3 

4 AEGL values are summarized in Table 8. AEGL values were based on molar adjustments of 

5 hydrogen cyanide AEGL values. 

6 

TABLE 8. AEGL VALUES FOR METAL CYANIDE SALTS* 

Compound Classification 10-min 30-min 1-hr 4-hr 8-hr

AEGL-1 5.0 mg/m3

 5.0 mg/m3 4.0 mg/m3 2.6 mg/m3 2.0 mg/m3

AEGL-2 34 mg/m3

 20 mg/m3 14 mg/m3 7.0 mg/m3 5.0 mg/m3

Sodium 

Cyanide 

AEGL-3 54 mg/m3

 42 mg/m3 30 mg/m3 17 mg/m3 13 mg/m3

AEGL-1 6.6 mg/m3

 6.6 mg/m3 5.3 mg/m3 3.5 mg/m3 2.7 mg/m3

AEGL-2 45 mg/m3

 27 mg/m3 19 mg/m3 9.3 mg/m3 6.6 mg/m3

Potassium 

Cyanide 

AEGL-3 72 mg/m3

 56 mg/m3 40 mg/m3 23 mg/m3 18 mg/m3

AEGL-1 4.7 mg/m3

 4.7 mg/m3 3.8 mg/m3 2.4 mg/m3 1.9 mg/m3

AEGL-2 32 mg/m3

 19 mg/m3 13 mg/m3 6.6 mg/m3 4.7 mg/m3

Calcium 

Cyanide** 

AEGL-3 51 mg/m3

 39 mg/m3 28 mg/m3 16 mg/m3 12 mg/m3

7 3⁄4 *These airborne concentrations will produce the equivalent AEGL values for hydrogen cyanide. 

8 3⁄4 ** Although the adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

9 compound) than would be expected on a molar basis for CN, the production of two moles of HCN was 

10 assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

11 

12 

13 

14 8.2. Comparison with Other Standards and Guidelines 

15 

TABLE 9. Extant Standards and Guidelines for Sodium Cyanide 

Exposure Duration

Guideline 10 min 30 min 1 h 4 h 8 h 

AEGL-1 5.0 mg/m3 5.0 mg/m3 4.0 mg/m3 2.6 mg/m3 2.0 mg/m3

AEGL-2 34 mg/m3 20 mg/m3 14 mg/m3 7.0 mg/m3 5.0 mg/m3

AEGL-3 54 mg/m3 42 mg/m3 30 mg/m3 17 mg/m3 13 mg/m3

PEL-TWA 

(OSHA)a

 5.0 mg/m3 

 (as CN) 

IDLH (NIOSH)b 25 mg/m3 

(as CN) 

 

 REL-TWA (NIOSH)c 5.0 mg/m3 

(as CN)[10-min] 

 

TLV-STEL (ACGIH)d 5.0 mg/m3 

(as CN) 

 

MAK (Germany)e 3.8 mg/m3

MAC-Peak Category 

(The Netherlands)f

 5.0 mg/m3 

(as CN) 

OEL (Sweden)g 5.0 mg/m3 

(as CN) a 16 OSHA PEL-TWA (Occupational Health and Safety Administration, Permissible Exposure Limits - Time Weighted 

17 Average) (OSHA, 1993) is defined analogous to the ACGIH-TLV-TWA, but is for exposures of no more than 10 

18 hours/day, 40 hours/week. Value for cyanides (as CN). 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 15 of 38 

1 b 2 IDLH (Immediately Dangerous to Life and Health, National Institute of Occupational Safety and Health) (NIOSH, 

3 1996) represents the maximum concentration from which one could escape within 30 minutes without any 

4 escape-impairing symptoms, or any irreversible health effects. Value for cyanides (as CN). 

5 c 6 NIOSH REL-TWA (National Institute of Occupational Safety and Health, Recommended Exposure Limits - Time 

7 Weighted Average) (NIOSH, 2005) is defined analogous to the ACGIH-TLV-TWA. Value for cyanides except 

8 hydrogen cyanide. 

9 

d 10 ACGIH TLV-STEL (Threshold Limit Value - Short Term Exposure Limit) (ACGIH, 2008) is defined as a 15-minute 

11 TWA exposure which should not be exceeded at any time during the workday even if the 8-hour TWA is within 

12 the TLV-TWA. Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should 

13 not occur more than 4 times per day. There should be at least 60 minutes between successive exposures in this 

14 range. Value is for sodium, potassium, and calcium cyanides (as CN). 

15 e 16 MAK (Maximale Arbeitsplatzkonzentration [Maximum Workplace Concentration], Deutsche Forschungs-gemeinschaft 

17 [German Research Association], Germany) (DFG, 2007) is defined analogous to the ACGIH-TLV-TWA. 

18 

f 19 MAC (Maximaal Aanvaaarde Concentratie [Maximal Accepted Concentration - Peak Category]) (SDU Uitgevers 

20 [under the auspices of the Ministry of Social Affairs and Employment], The Hague, The Netherlands 2000) is 

21 defined analogous to the ACGIH-Ceiling. Value for cyanides (as CN). 

22 g 23 OEL (Occupational Exposure Limit Values and Measures Against Air Contaminants) [Swedish Work Environment 

24 Authority] (AFS, 2005). Value for cyanides and hydrogen cyanide (as CN) total dust. 

25 

26 

27 

TABLE 10. Extant Standards and Guidelines for Potassium Cyanide 

Exposure Duration

Guideline 10 min 30 min 1 h 4 h 8 h 

AEGL-1 6.6 mg/m3 6.6 mg/m3 5.3 mg/m3 3.5 mg/m3 2.7 mg/m3

AEGL-2 45 mg/m3 27 mg/m3 19 mg/m3 9.3 mg/m3 6.6 mg/m3

AEGL-3 72 mg/m3 56 mg/m3 40 mg/m3 23 mg/m3 18 mg/m3

PEL-TWA 

(OSHA)a

 5.0 mg/m3

 

(as CN) 

IDLH (NIOSH)b 25 mg/m3 

(as CN) 

 

 REL-TWA 

(NIOSH)c

5.0 mg/m3

 

(as CN)[10-min] 

 

TLV-STEL 

(ACGIH)d

5.0 mg/m3

 

(as CN) 

 

MAK (Germany)e 5.0 mg/m3

MAC-Peak Category 

(The Netherlands)f

 5.0 mg/m3

 

(as CN) 

OEL (Sweden)g 5.0 mg/m3 

(as CN) a 28 OSHA PEL-TWA (Occupational Health and Safety Administration, Permissible Exposure Limits - Time Weighted 

29 Average) (OSHA, 1993) is defined analogous to the ACGIH-TLV-TWA, but is for exposures of no more than 10 

30 hours/day, 40 hours/week. Value for cyanides (as CN). 

31 b 32 IDLH (Immediately Dangerous to Life and Health, National Institute of Occupational Safety and Health) (NIOSH, 

33 1996) represents the maximum concentration from which one could escape within 30 minutes without any 

34 escape-impairing symptoms, or any irreversible health effects. Value for cyanides (as CN). 

35 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 16 of 38 

c 1 NIOSH REL-TWA (National Institute of Occupational Safety and Health, Recommended Exposure Limits - Time 

2 Weighted Average) (NIOSH, 2005) is defined analogous to the ACGIH-TLV-TWA. Value for cyanides except 

3 hydrogen cyanide. 

4 

d 5 ACGIH TLV-STEL (Threshold Limit Value - Short Term Exposure Limit) (ACGIH, 2008) is defined as a 15-minute 

6 TWA exposure which should not be exceeded at any time during the workday even if the 8-hour TWA is within 

7 the TLV-TWA. Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should 

8 not occur more than 4 times per day. There should be at least 60 minutes between successive exposures in this 

9 range. Value is for sodium, potassium, and calcium cyanides (as CN). 

10 e 11 MAK (Maximale Arbeitsplatzkonzentration [Maximum Workplace Concentration], Deutsche Forschungs-gemeinschaft 

12 [German Research Association], Germany) (DFG, 2007) is defined analogous to the ACGIH-TLV-TWA. 

13 

f 14 MAC (Maximaal Aanvaaarde Concentratie [Maximal Accepted Concentration - Peak Category]) (SDU Uitgevers 

15 [under the auspices of the Ministry of Social Affairs and Employment], The Hague, The Netherlands 2000) is 

16 defined analogous to the ACGIH-Ceiling. Value for cyanides (as CN). 

17 g 18 OEL (Occupational Exposure Limit Values and Measures Against Air Contaminants) [Swedish Work Environment 

19 Authority] (AFS, 2005). Value for cyanides and hydrogen cyanide (as CN) total dust. 

20 

21 

22 

23 

TABLE 11. Extant Standards and Guidelines for Calcium Cyanide 

Exposure Duration

Guideline 10 min 30 min 1 h 4 h 8 h 

AEGL-1 4.7 mg/m3 4.7 mg/m3 3.8 mg/m3 2.4 mg/m3 1.9 mg/m3

AEGL-2 32 mg/m3 19 mg/m3 13 mg/m3 6.6 mg/m3 4.7 mg/m3

AEGL-3 51 mg/m3 39 mg/m3 28 mg/m3 16 mg/m3 12 mg/m3

PEL-TWA 

(OSHA)a

 5.0 mg/m3 (as 

CN) 

IDLH (NIOSH)b 25 mg/m3 

(as CN) 

 

 REL-TWA 

(NIOSH)c

5.0 mg/m3

 

(as CN)[10-min] 

 

TLV-STEL 

(ACGIH)d

5.0 mg/m3

 (as 

CN) 

 

MAC-Peak Category 

(The Netherlands)e

 5.0 mg/m3

 

(as CN) 

OEL (Sweden)f 5.0 mg/m3 

(as CN) a 24 OSHA PEL-TWA (Occupational Health and Safety Administration, Permissible Exposure Limits - Time Weighted 

25 Average) (OSHA, 1993) is defined analogous to the ACGIH-TLV-TWA, but is for exposures of no more than 10 

26 hours/day, 40 hours/week. Value for cyanides (as CN). 

27 b 28 IDLH (Immediately Dangerous to Life and Health, National Institute of Occupational Safety and Health) (NIOSH, 

29 1996) represents the maximum concentration from which one could escape within 30 minutes without any 

30 escape-impairing symptoms, or any irreversible health effects. Value for cyanides (as CN). 

31 c 32 NIOSH REL-TWA (National Institute of Occupational Safety and Health, Recommended Exposure Limits - Time 

33 Weighted Average) (NIOSH, 2005) is defined analogous to the ACGIH-TLV-TWA. Value for cyanides except 

34 hydrogen cyanide. 

35 

d 36 ACGIH TLV-STEL (Threshold Limit Value - Short Term Exposure Limit) (ACGIH, 2008) is defined as a 15-minute 

37 TWA exposure which should not be exceeded at any time during the workday even if the 8-hour TWA is within 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 17 of 38 

1 the TLV-TWA. Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should 

2 not occur more than 4 times per day. There should be at least 60 minutes between successive exposures in this 

3 range. Value is for sodium, potassium, and calcium cyanides (as CN). 

4 e 5 MAC (Maximaal Aanvaaarde Concentratie [Maximal Accepted Concentration - Peak Category]) (SDU Uitgevers 

6 [under the auspices of the Ministry of Social Affairs and Employment], The Hague, The Netherlands 2000) is 

7 defined analogous to the ACGIH-Ceiling. Value for cyanides (as CN). 

8 

f 9 OEL (Occupational Exposure Limit Values and Measures Against Air Contaminants) [Swedish Work Environment 

10 Authority] (AFS, 2005). Value for cyanides and hydrogen cyanide (as CN) total dust. 

11 

12 

13 

14 8.3. Data Adequacy and Research Needs 

15 

16 There are no human or animal inhalation data for sodium, potassium, or calcium cyanide. 

17 However, data suggest that the cyanide moiety is responsible for the acute toxicity of these 

18 compounds, and the hydrogen cyanide data set is fairly robust. 

19 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 18 of 38 

1 9. REFERENCES 

2 

3 

4 ACGIH (American Conference of Governmental Industrial Hygienists). 2008. Threshold Limit Values and Biological 

5 Exposure Indices; Hydrogen cyanide and cyanide salts. American Conference of Governmental Industrial 

6 Hygienists, Inc. Cincinnati, OH. 

7 

8 ACGIH (American Conference of Governmental Industrial Hygienists). 1996. Documentation of the Threshold Limit 

9 Values and Biological Exposure Indices; Hydrogen cyanide and cyanide salts. American Conference of 

10 Governmental Industrial Hygienists, Inc. Cincinnati, OH. 

11 

12 AFS. 2005. Cyanides. OEL (Occupational Exposure Limit Values and Measures Against Air Contaminants) [Swedish 

13 Work Environment Authority]. 

14 

15 ATSDR (Agency for Toxic Substances and Disease Registry). 1997. Toxicological profile for cyanide. U.S. 

16 Department of Health and Human Services, Public Health Service, Atlanta, GA. 

17 

18 Cohrssen, B. 2001. Cyanides and Nitriles. In: Patty’s Toxicology fifth Edition, Volume 4. E. Bingham, B. Cohrssen, 

19 and C. H. Powell, Eds. John Wiley and Sons, Inc. pp. 1373-1456. 

20 

21 DFG. 2007. Deutsche Forschungs-gemeinschaft [German Research Association. MAK (Maximale 

22 Arbeitsplatzkonzentration [Maximum Workplace Concentration], Germany. 

23 

24 E.I. du Pont de Nemours and Company. 1981. Inhalation toxicity of common combustion gases. Haskell Laboratory 

25 Report No. 238-81. Haskell Laboratory, Newark, DE. 

26 

27 El Ghawabi, S.H., M.A. Gaafar, A.A. El-Saharti, S.H. Ahmed, K.K. Malash and R. Fares. 1975. Chronic cyanide 

28 exposure: A clinical, radioisotope, and laboratory study. Brit. J. Ind. Med. 32:215-219. 

29 

30 Grabois, B. 1954. Monthly Review 33:33; Publication of the Division of Industrial Hygiene, New York Department of 

31 Labor, September 1954. 

32 

33 Hardy, H.L., W.M. Jeffries, M.M. Wasserman, and W.R. Waddell. 1950. Thiocyanate effect following industrial 

34 cyanide exposure - report of two cases. New Engl. J. Med. 242:968-972. 

35 

36 HSDB (Hazardous Substances Data Bank). 2008a. Sodium Cyanide. Online data base, National Library of Medicine: 

37 http://toxnet.nlm.nih.gov/cgi-bin/sis. 

38 

39 HSDB (Hazardous Substances Data Bank). 2008b. Potassium Cyanide. Online data base, National Library of 

40 Medicine: http://toxnet.nlm.nih.gov/cgi-bin/sis. 

41 

42 HSDB (Hazardous Substances Data Bank). 2008c. Calcium Cyanide. Online data base, National Library of Medicine: 

43 http://toxnet.nlm.nih.gov/cgi-bin/sis. 

44 

45 IUCLID. 2000. IUCLID Dataset for potassium cyanide. European Commission- European Chemicals Bureau. 

46 February 18, 2000. 

47 

48 Kirk-Othmer. 2008. Cyanides. Kirk-Othmer Encyclopedia of Chemical Technology. 

49 http://www.mrw.interscience.wiley.com. 

50 

51 Leeser, J.E., J.A. Tomenson, and D.D. Bryson. 1990. A cross-sectional study of the health of cyanide salt production 

52 workers. Report No. OHS/R/2, ICI Central Toxicology Laboratory, Alderley Park, Maccles field, Cheshire, 

53 U.K. 

54 

55 Maehly, A.C. and A. Swensson. 1970. Cyanide and thiocyanate levels in blood and urine of workers with low-grade 

56 exposure to cyanide. Int. Arch. Arbeitsmed. 27:195-209. 

57 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 19 of 38 

1 NIOSH (National Institute for Occupational Safety and Health). 1996. Documentation for Immediately Dangerous to 

2 Life or Health Concentrations (IDLHs). Cyanides (as CN). U.S. Department of Health and Human Services; 

3 U.S. Government Printing Office, Washington. (Retrieved online Nov. 2008) 

4 

5 NIOSH (National Institute for Occupational Safety and Health). 2005. NIOSH Pocket Guide 

6 to Chemical Hazards. Cyanides (as CN) U.S. Department of Health and Human Services; U.S. Government 

7 Printing Office, Washington, PB9419504 National Technical Information Service, Springfield, VA. (Retrieved 

8 online Nov. 2008) 

9 

10 

11 NRC (National Research Council). 2002. Acute Exposure Guideline Levels for Selected Airborne Chemicals. Volume 

12 2. Hydrogen Cyanide. pp. 211-276. 

13 

14 Purser, D.A., P. Grimshaw, and K.R. Berrill. 1984. Intoxication by cyanide in fires: A study in monkeys using 

15 polyacrylonitrile. Arch. Environ. Health 39:394-400. 

16 

17 SDU Uitgevers. 2000. Nationale MAC List (under the auspices of the Ministry of Social Affairs and Employment), 

18 The Hague, The Netherlands. 

19 

20 Smith, R.P. 1996. Toxic responses of the blood. In: Casarett & Doull's Toxicology: The Basic Science of Poisons, 5th 

21 Ed., McGraw-Hill, New York, pp. 350-351. 

22 

23 Smyth, H.F., Carpenter, C.P., Weil, C.S., Pozzani, Striegel, J.A., and Nycum, J.S. 1969. Range-finding toxicity data: 

24 List VII. Am. Ind. Hyg. Assoc. J. 30: 470-476. 

25 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 20 of 38

1 APPENDIX A: Derivation of AEGL Values for Cyanide Salts 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 21 of 38 

1 

2 Derivation of AEGL-1 

3 

4 Derivation of AEGL-1 for Sodium Cyanide 

5 Key Study: Hydrogen cyanide AEGL-1 values used as target values for calculating the concentrations of cyanide salt needed to 

6 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

7 of NaCN will yield one mole of HCN). 

8 

9 10-min AEGL-1 = 2.5 ppm ÷ 1 = 2.5 ppm 

 2.5 ppm x 49.0 ÷ 24.5 = 5.0 mg/m3 10 

11 

12 30-min AEGL-1 = 2.5 ppm ÷ 1 = 2.5 ppm 

 2.5 ppm x 49.0 ÷ 24.5 = 5.0 mg/m3 13 

14 

15 1-hour AEGL-1= 2.0 ppm ÷ 1 = 2.0 ppm 

2.0 ppm x 49.0 ÷ 24.5 = 4.0 mg/m3 16 

17 

18 4-hour AEGL-1 = 1.3 ppm ÷ 1 = 1.3 ppm 

1.3 ppm x 49.0 ÷ 24.5 = 2.6 mg/m3 19 

20 

21 8-hour AEGL-1 = 1.0 ppm ÷ 1 = 1.0 ppm 

1.0 ppm x 49.0 ÷ 24.5 = 2.0 mg/m3 22 

23 

24 

25 Derivation of AEGL-1 for Potassium Cyanide 

26 Key Study: Hydrogen cyanide AEGL-1 values used as target values for calculating the concentrations of cyanide salt needed to 

27 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

28 of KCN will yield one mole of HCN). 

29 

30 10-min AEGL-1 = 2.5 ppm ÷ 1 = 2.5 ppm 

 2.5 ppm x 65.1 ÷ 24.5 = 6.6 mg/m3 31 

32 

33 30-min AEGL-1 = 2.5 ppm ÷ 1 = 2.5 ppm 

 2.5 ppm x 65.1 ÷ 24.5 = 6.6 mg/m3 34 

35 

36 1-hour AEGL-1= 2.0 ppm ÷ 1 = 2.0 ppm 

2.0 ppm x 65.1 ÷ 24.5 = 5.3 mg/m3 37 

38 

39 4-hour AEGL-1 = 1.3 ppm ÷ 1 = 1.3 ppm 

1.3 ppm x 65.1 ÷ 24.5 = 3.5 mg/m3 40 

41 

42 8-hour AEGL-1 = 1.0 ppm ÷ 1 = 1.0 ppm 

1.0 ppm x 65.1 ÷ 24.5 = 2.7 mg/m3 43 

44 

45 Derivation of AEGL-1 for Calcium Cyanide 

46 Key Study: Hydrogen cyanide AEGL-1 values used as target values for calculating the concentrations of cyanide salt needed to 

47 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

48 of Ca(CN)2 will yield two moles of HCN). 

49 

50 10-min AEGL-1 = 2.5 ppm ÷ 2 = 1.25 ppm 

 1.25 ppm x 92.1 ÷ 24.5 = 4.7 mg/m3 51 

52 

53 30-min AEGL-1 = 2.5 ppm ÷ 2 = 1.25 ppm 

 1.25 ppm x 92.1 ÷ 24.5 = 4.7 mg/m3 54 

55 

56 1-hour AEGL-1= 2.0 ppm ÷ 2 = 1.0 ppm 

1.0 ppm x 92.1 ÷ 24.5 = 3.8 mg/m3 57 

58 

59 4-hour AEGL-1 = 1.3 ppm ÷ 2 = 0.65 ppm 

0.65 ppm x 92.1 ÷ 24.5 = 2.4 mg/m3 60 

61 

62 8-hour AEGL-1 = 1.0 ppm ÷ 2 = 0.50 ppm 

0.50 ppm x 92.1 ÷ 24.5 = 1.9 mg/m3 63 

64 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 22 of 38 

1 Derivation of AEGL-2 

2 

3 Derivation of AEGL-2 for Sodium Cyanide 

4 Key Study: Hydrogen cyanide AEGL-2 values used as target values for calculating the concentrations of cyanide salt needed to 

5 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

6 of NaCN will yield one mole of HCN). 

7 

8 10-min AEGL-2 = 17 ppm ÷ 1 = 17 ppm 

 17 ppm x 49.0 ÷ 24.5 = 34 mg/m3 9 

10 

11 30-min AEGL-2 = 10 ppm ÷ 1 = 10 ppm 

 10 ppm x 49.0 ÷ 24.5 = 20 mg/m3 12 

13 

14 1-hour AEGL-2= 7.1 ppm ÷ 1 = 7.1 ppm 

7.1 ppm x 49.0 ÷ 24.5 = 14 mg/m3 15 

16 

17 4-hour AEGL-2 = 3.5 ppm ÷ 1 = 3.5 ppm 

3.5 ppm x 49.0 ÷ 24.5 = 7.0 mg/m3 18 

19 

20 8-hour AEGL-2 = 2.5 ppm ÷ 1 = 2.5 ppm 

2.5 ppm x 49.0 ÷ 24.5 = 5.0 mg/m3 21 

22 

23 

24 Derivation of AEGL-2 for Potassium Cyanide 

25 Key Study: Hydrogen cyanide AEGL-2 values used as target values for calculating the concentrations of cyanide salt needed to 

26 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

27 of KCN will yield one mole of HCN). 

28 

29 10-min AEGL-2 = 17 ppm ÷ 1 = 17 ppm 

 17 ppm x 65.1 ÷ 24.5 = 45 mg/m3 30 

31 

32 30-min AEGL-2 = 10 ppm ÷ 1 = 10 ppm 

 10 ppm x 65.1 ÷ 24.5 = 27 mg/m3 33 

34 

35 1-hour AEGL-2= 7.1 ppm ÷ 1 = 7.1 ppm 

7.1 ppm x 65.1 ÷ 24.5 = 19 mg/m3 36 

37 

38 4-hour AEGL-2 = 3.5 ppm ÷ 1 = 3.5 ppm 

3.5 ppm x 65.1 ÷ 24.5 = 9.3 mg/m3 39 

40 

41 8-hour AEGL-2 = 2.5 ppm ÷ 1 = 2.5 ppm 

2.5 ppm x 65.1 ÷ 24.5 = 6.6 mg/m3 42 

43 

44 

45 Derivation of AEGL-2 for Calcium Cyanide 

46 Key Study: Hydrogen cyanide AEGL-2 values used as target values for calculating the concentrations of cyanide salt needed to 

47 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

48 of Ca(CN)2 will yield two moles of HCN). 

49 

50 10-min AEGL-2 = 17 ppm ÷ 2 = 8.5 ppm 

 8.5 ppm x 92.1 ÷ 24.5 = 32 mg/m3 51 

52 

53 30-min AEGL-2 = 10 ppm ÷ 2 = 5 ppm 

 5 ppm x 92.1 ÷ 24.5 = 19 mg/m3 54 

55 

56 1-hour AEGL-2= 7.1 ppm ÷ 2 = 3.55 ppm 

3.55 ppm x 92.1 ÷ 24.5 = 13 mg/m3 57 

58 

59 4-hour AEGL-2 = 3.5 ppm ÷ 2 = 1.75 ppm 

1.75 ppm x 92.1 ÷ 24.5 = 6.6 mg/m3 60 

61 

62 8-hour AEGL-2 = 2.5 ppm ÷ 2 = 1.25 ppm 

1.25 ppm x 92.1 ÷ 24.5 = 4.7 mg/m3 63 

64 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 23 of 38 

1 

2 Derivation of AEGL-3 

3 

4 Derivation of AEGL-3 for Sodium Cyanide 

5 Key Study: Hydrogen cyanide AEGL-3 values used as target values for calculating the concentrations of cyanide salt needed to 

6 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

7 of NaCN will yield one mole of HCN). 

8 

9 10-min AEGL-3 = 27 ppm ÷ 1 = 27 ppm 

 27 ppm x 49.0 ÷ 24.5 = 54 mg/m3 10 

11 

12 30-min AEGL-3 = 21 ppm ÷ 1 = 21 ppm 

 21 ppm x 49.0 ÷ 24.5 = 42 mg/m3 13 

14 

15 1-hour AEGL-3= 15 ppm ÷ 1 = 15 ppm 

15 ppm x 49.0 ÷ 24.5 = 30 mg/m3 16 

17 

18 4-hour AEGL-3 = 8.6 ppm ÷ 1 = 8.6 ppm 

8.6 ppm x 49.0 ÷ 24.5 = 17 mg/m3 19 

20 

21 8-hour AEGL-3 = 6.6 ppm ÷ 1 = 6.6 ppm 

6.6 ppm x 49.0 ÷ 24.5 = 13 mg/m3 22 

23 

24 Derivation of AEGL-3 for Potassium Cyanide 

25 Key Study: Hydrogen cyanide AEGL-3 values used as target values for calculating the concentrations of cyanide salt needed to 

26 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

27 of KCN will yield one mole of HCN). 

28 

29 10-min AEGL-3 = 27 ppm ÷ 1 = 27 ppm 

 27 ppm x 65.1 ÷ 24.5 = 72 mg/m3 30 

31 

32 30-min AEGL-3 = 21 ppm ÷ 1 = 21 ppm 

 21 ppm x 65.1 ÷ 24.5 = 56 mg/m3 33 

34 

35 1-hour AEGL-3= 15 ppm ÷ 1 = 15 ppm 

15 ppm x 65.1 ÷ 24.5 = 40 mg/m3 36 

37 

38 4-hour AEGL-3 = 8.6 ppm ÷ 1 = 8.6 ppm 

8.6 ppm x 65.1 ÷ 24.5 = 23 mg/m3 39 

40 

41 8-hour AEGL-3 = 6.6 ppm ÷ 1 = 6.6 ppm 

6.6 ppm x 65.1 ÷ 24.5 = 18 mg/m3 42 

43 

44 

45 Derivation of AEGL-3 for Calcium Cyanide 

46 Key Study: Hydrogen cyanide AEGL-3 values used as target values for calculating the concentrations of cyanide salt needed to 

47 generate the hydrogen cyanide AEGL values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis (one mole 

48 of Ca(CN)2 will yield two moles of HCN). 

49 

50 10-min AEGL-3 = 27 ppm ÷ 2 = 13.5 ppm 

 13.5 ppm x 92.1 ÷ 24.5 = 51 mg/m3 51 

52 

53 30-min AEGL-3 = 21 ppm ÷ 2 = 10.5 ppm 

 10.5 ppm x 92.1 ÷ 24.5 = 39 mg/m3 54 

55 

56 1-hour AEGL-3= 15 ppm ÷ 2 = 7.5 ppm 

7.5 ppm x 92.1 ÷ 24.5 = 28 mg/m3 57 

58 

59 4-hour AEGL-3 = 8.6 ppm ÷ 2 = 4.3 ppm 

4.3 ppm x 92.1 ÷ 24.5 = 16 mg/m3 60 

61 

62 8-hour AEGL-3 = 6.6 ppm ÷ 2 = 3.3 ppm 

3.3 ppm x 92.1 ÷ 24.5 = 12 mg/m3 63 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 24 of 38

1 APPENDIX B: Time Scaling Calculation for Hydrogen Cyanide AEGL-1, AEGL-2, and 

2 AEGL-3 

3 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 25 of 38 

1 HYDROGEN CYANIDE AEGL-1 (NRC, 2002)

2 

3 Key studies: El Ghawabi et al. 1975; Hardy et al. 1950; Grabois 1954; Maehly and 

4 Swensson 1970; Leeser et al. 1990 

5 

6 Toxicity endpoint: No adverse effect in healthy adult humans occupationally exposed to geometric 

7 mean concentration of #1 [range 0.01-3.3 ppm, personal samplers (up 

8 to 6 ppm, area samples)] or 5 ppm; mild headache in adult humans 

9 occupationally exposed to 8 ppm. The exposure duration was 

10 considered to be 8 hours. 

11 

12 Uncertainty factor: 3 for intraspecies (no susceptible populations were identified). The 

13 uncertainty factor was applied to the 8-hour 5 and 8 ppm 

14 concentrations which resulted in concentrations close to the 8-hour 1 

15 ppm concentration in the Leeser et al. study. 

16 

Scaling: C3 17 x t = k (conservative time-scaling relationship because the 

18 relationship between concentration and exposure duration for the 

19 headache effect is unknown. An 8-hour 1 ppm concentration was used 

20 as the starting point for time scaling. 

21 

Calculations: (C3 22 /uncertainty factors) x t = k 

 (1 ppm)3 x 480 minutes = 480 ppm3 23 ·minutes 

24 

25 

10-minute AEGL-1 (480 ppm3·minutes/10 minutes)1/3 26 = 3.6 ppm 

27 Because 3.6 ppm is above the highest exposure concentration in the 

28 Leeser et al. (1990) study, as measured by personal monitors, the 10-

29 minute value was set equal to the 30-minute value. 

30 

30-minute AEGL-1 (480 ppm3·minutes/30 minutes)1/3 31 = 2.5 ppm 

32 

1-hour AEGL-1 (480 ppm3

·minutes/60 minutes)1/3 33 = 2.0 ppm 

34 

4-hour AEGL-1 (480 ppm3

·minutes/240 minutes)1/3 35 = 1.3 ppm 

36 

37 8-hour AEGL-1 1.0 ppm 

38 

39 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 26 of 38 

1 

2 HYDROGEN CYANIDE AEGL-2 (NRC, 2002) 

3 

4 Key study: Purser 1984 

5 

6 Toxicity endpoint: Slight central nervous system depression in monkeys inhaling 60 ppm for 30 

7 minutes 

8 

Scaling: C2 9 x t = k (this document; based on regression analysis of incapacitation and 

10 lethality data for the monkey) 

11 

12 Uncertainty factors: 2 for interspecies 

13 3 for intraspecies 

14 combined uncertainty factor of 6 

15 

Calculations: (C2 16 /uncertainty factors) x t = k 

 (60 ppm/6)2 x 30 minutes = 3000 ppm2 17 ·minutes 

18 

19 

10-minute AEGL-2 (3000 ppm2·minutes/10 minutes)1⁄2 20 = 17 ppm 

21 

22 30-minute AEGL-2 60 ppm/6 = 10 ppm 

23 

1-hour AEGL-2 (3000 ppm2·minutes/60 minutes)1⁄2 24 = 7.1 ppm 

25 

4-hour AEGL-2 (3000 ppm2·minutes/240 minutes)1⁄2 26 = 3.5 ppm 

27 

8-hour AEGL-2 (3000 ppm2·minutes/480 minutes)1⁄2 28 = 2.5 ppm 

29 

30 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 27 of 38 

1 

2 HYDROGEN CYANIDE AEGL-3 (NRC, 2002)

3 

4 Key study: E.I. du Pont de Nemours 1981 

5 

6 Toxicity endpoint: 15-minute LC01 of 138 ppm in the rat 

7 30-minute LC01 of 127 ppm in the rat 

8 1-hour LC01 of 88 ppm in the rat 

9 LC01 derived by probit analysis 

10 

Scaling: C2.6 11 x t = k (this document; based on the E.I. du Pont de Nemours (1981) rat 

12 data set 

13 

14 Uncertainty factors: 2 for interspecies 

15 3 for intraspecies 

16 combined uncertainty factor of 6 

17 

Calculations: (C2.6 18 /uncertainty factors) x t = k 

 (138 ppm/6)2.6 x 15 minutes = 52069.5 ppm2.6 19 ·minutes 

(127 ppm/6)2.6 x 30 minutes = 83911 ppm2.6 20 ·minutes 

(88 ppm/6)2.6 x 60 minutes = 64656.6 ppm2.6 21 ·minutes 

22 

23 

10-minute AEGL-3 (52069.5 ppm2.6·minutes/10 minutes)1/2.6 24 = 27 ppm 

25 

26 30-minute AEGL-3 127 ppm/6 = 21 ppm 

27 

28 1-hour AEGL-3 88 ppm/6 = 15 ppm 

29 

4-hour AEGL-3 (64656.6 ppm2.6·minutes/240 minutes)1/2.6 30 = 8.6 ppm 

31 

8-hour AEGL-3 (64656.6 ppm2.6·minutes/480 minutes)1/2.6 32 = 6.6 ppm 

33 

34 

35 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 28 of 38

1 APPENDIX C: Derivation Summary Tables for Cyanide Salts AEGLs 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 29 of 38

AEGL-1 VALUES FOR CYANIDE SALTS 

10 min 30 min 1 h 4 h 8 h

Sodium Cyanide 

5.0 mg/m3 5.0 mg/m3 4.0 mg/m3 2.6 mg/m3 2.0 mg/m3

Potassium Cyanide 

6.6 mg/m3 6.6 mg/m3 5.3 mg/m3 3.5 mg/m3 2.7 mg/m3

Calcium Cyanide 

4.7 mg/m3 4.7 mg/m3 3.8 mg/m3 2.4 mg/m3 1.9 mg/m3

Key Reference: NRC (National Research Council). 2002. Acute Exposure Guideline Levels for Selected 

Airborne Chemicals. Volume 2. Hydrogen Cyanide. pp. 211-276. 

Test Species/Strain/Number: 

 Exposure Route/Concentrations/Durations: 

Effects: 

Endpoint/Concentration/Rationale: AEGL-1 values for hydrogen cyanide were used to obtain AEGL-1 values for 

the title cyanide salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that the cyanide 

moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide AEGL-1 values were used as 

target values for calculating the concentrations of cyanide salt needed to generate the hydrogen cyanide AEGL 

values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis. 

Uncertainty Factors/Rationale: 

Interspecies: 

Intraspecies: 

Molar Adjustment Factor: 

 1 (Sodium cyanide and Potassium cyanide) 

 2 (Calcium cyanide) 

Animal to Human Dosimetric Adjustment: 

 Time Scaling: 

Data adequacy: AEGL-1 values for cyanide salts were derived by analogy to HCN AEGL-1 values. The HCN 

database is robust. 

Calcium Cyanide: The adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

compound) than would be expected on a molar basis for CN. However, the production of two moles of HCN was 

assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

1 

2 

3 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 30 of 38 

1 

AEGL-2 VALUES FOR CYANIDE SALTS 

10 min 30 min 1 h 4 h 8 h

Sodium Cyanide 

34 mg/m3 20 mg/m3 14 mg/m3 7.0 mg/m3 5.0 mg/m3

Potassium Cyanide 

45 mg/m3 27 mg/m3 19 mg/m3 9.3 mg/m3 6.6 mg/m3

Calcium Cyanide 

32 mg/m3 19 mg/m3 13 mg/m3 6.6 mg/m3 4.7 mg/m3

Key Reference: NRC (National Research Council). 2002. Acute Exposure Guideline Levels for Selected 

Airborne Chemicals. Volume 2. Hydrogen Cyanide. pp. 211-276. 

Test Species/Strain/Number: 

 Exposure Route/Concentrations/Durations: 

Effects: 

Endpoint/Concentration/Rationale: AEGL-2 values for hydrogen cyanide were used to obtain AEGL-2 values for 

the title cyanide salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that the cyanide 

moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide AEGL-2 values were used as 

target values for calculating the concentrations of cyanide salt needed to generate the hydrogen cyanide AEGL 

values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis. 

Uncertainty Factors/Rationale: 

Interspecies: 

Intraspecies: 

Molar Adjustment Factor: 

 1 (Sodium cyanide and Potassium cyanide) 

 2 (Calcium cyanide) 

Animal to Human Dosimetric Adjustment: 

 Time Scaling: 

Data adequacy: AEGL-2 values for cyanide salts were derived by analogy to HCN AEGL-2 values. The HCN 

database is robust. 

Calcium Cyanide: The adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

compound) than would be expected on a molar basis for CN. However, the production of two moles of HCN was 

assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 31 of 38 

1 

AEGL-3 VALUES FOR CYANIDE SALTS 

10 min 30 min 1 h 4 h 8 h

Sodium Cyanide 

54 mg/m3 42 mg/m3 30 mg/m3 17 mg/m3 13 mg/m3

Potassium Cyanide 

72 mg/m3 56 mg/m3 40 mg/m3 23 mg/m3 18 mg/m3

Calcium Cyanide 

51 mg/m3 39 mg/m3 28 mg/m3 16 mg/m3 12 mg/m3

Key Reference: NRC (National Research Council). 2002. Acute Exposure Guideline Levels for Selected 

Airborne Chemicals. Volume 2. Hydrogen Cyanide. pp. 211-276. 

Test Species/Strain/Number: 

 Exposure Route/Concentrations/Durations: 

Effects: 

Endpoint/Concentration/Rationale: AEGL-3 values for hydrogen cyanide were used to obtain AEGL-3 values for 

the title cyanide salts. The use of hydrogen cyanide as a surrogate for the cyanide salts is deemed appropriate 

because qualitative (clinical signs) and quantitative (adjusted rat oral LD50 values) data suggest that the cyanide 

moiety is responsible for acute toxicity of the cyanide salts. The hydrogen cyanide AEGL-3 values were used as 

target values for calculating the concentrations of cyanide salt needed to generate the hydrogen cyanide AEGL 

values. Calculations assume 25 degrees C and 760 mm Hg and complete hydrolysis. 

Uncertainty Factors/Rationale: 

Interspecies: 

Intraspecies: 

Molar Adjustment Factor: 

 1 (Sodium cyanide and Potassium cyanide) 

 2 (Calcium cyanide) 

Animal to Human Dosimetric Adjustment: 

 Time Scaling: 

Data adequacy: AEGL-3 values for cyanide salts were derived by analogy to HCN AEGL-3 values. The HCN 

database is robust. 

Calcium Cyanide: The adjusted rat oral LC value for calcium cyanide is much greater (suggesting a less toxic 

compound) than would be expected on a molar basis for CN. However, the production of two moles of HCN was 

assumed per mole of calcium cyanide. This assumption will yield protective AEGL values. 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 32 of 38 

1 

2 

3 APPENDIX D: Derivation Summary Tables for Hydrogen Cyanide 

4 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 33 of 38 

1 

HYDROGEN CYANIDE AEGL-1 VALUES

10 minute 30 minute 1 hour 4 hour 8 hour

2.5 ppm 

2.8 mg/m3

2.5 ppm 

2.8 mg/m3

2.0 ppm 

2.2 mg/m3

1.3 ppm 

1.4 mg/m3

1.0 ppm 

1.1 mg/m3

Key Reference: (1) Leeser, J.E., J.A. Tomenson, and D.D. Bryson. 1990. A cross-sectional study of the health of 

cyanide salt production workers. Report No. OHS/R/2, ICI Central Toxicology Laboratory, Alderley Park, Maccles 

field, Cheshire, U.K. 

Supporting references: (2) El Ghawabi, S.H., M.A. Gaafar, A.A. El-Saharti, S.H. Ahmed, K.K. Malash and R. Fares. 

1975. Chronic cyanide exposure: A clinical, radioisotope, and laboratory study. Brit. J. Ind. Med. 32:215-219. 

(3) Grabois, B. 1954. Monthly Review 33:33; Publication of the Division of Industrial Hygiene, New York 

Department of Labor, September 1954. 

(4) Maehly, A.C. and A. Swensson. 1970. Cyanide and thiocyanate levels in blood and urine of workers with lowgrade exposure to cyanide. Int. Arch. Arbeitsmed. 27:195-209. 

(5) Hardy, H.L., W.M. Jeffries, M.M. Wasserman, and W.R. Waddell. 1950. Thiocyanate effect following industrial 

cyanide exposure - report of two cases. New Engl. J. Med. 242:968-972. 

Test Species/Strain/Number: Occupational exposures/63 employees, mean age 44.7 (Leeser et al. 1990) 

Occupational exposures/36 workers (El Ghawabi et al. 1975) 

Occupational exposures/five factories (Grabois 1954) 

Occupational exposures/94 workers (Maehly and Swensson 1970) 

Occupational exposures/factories (Hardy et al. 1950) 

Exposure Route/Concentrations/Durations: Inhalation/geometric mean exposure of 1 ppm (range, 0.01-3.3 ppm; 

personal samplers), up to 6 ppm (area samples)/mean service years, 16.5 (Leeser et al. 1990); Inhalation/average 

exposure 8 ppm/5-15 years (El Ghawabi et al. 1975); Inhalation/5 ppm/unknown/(Grabois 1954; Maehly and Swensson 

1970; Hardy et al. 1950). 

Effects: No exposure related adverse symptoms or health effects (surveys and medical examinations taken in spring and 

fall of year) (Leeser et al. 1990); mild headache, other symptoms (El Ghawabi et al. 1975); no effects reported (Grabois 

1954; Maehly and Swensson 1970; Hardy et al. 1950). 

Endpoint/Concentration/Rationale: 8 ppm from the El Ghawabi et al. (1975) study; 5 ppm from the Hardy et al. (1950), 

Grabois (1954), and Maehly and Swensson (1970) studies; or 1 ppm from the Leeser study, were considered noadverse-effect to mild effect concentrations for an 8-hour work day. The NRC adjusted the chronic 8 ppm value of El 

Ghawabi et al. (1975) to a 1-hour exposure for healthy adults. 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 3 

Interspecies: Not applicable 

Intraspecies: 3 - no specific susceptible populations were identified in monitoring studies or during the clinical use of 

nitroprusside solutions to control hypertension. The detoxifying enzyme rhodanese is present in all individuals 

including newborns. Application of the uncertainty factor to the El Ghawabi et al. (1975; as adjusted by the NRC) and 

Grabois (1954) data results in a value close to the 8-hour 1 ppm concentration in the Leeser et al. (1990) study. The 

uncertainty factor was not applied to the Leeser et al. (1990) 1 ppm concentration as it is the lowest NOAEL. 

Modifying Factor: Not applicable 

Animal to Human Dosimetric Adjustment: Not applicable 

Time Scaling: Because of the long-term exposure duration of the key studies, the conservative time-scaling value of 

n = 3 (k = 480 ppm3

·minutes) was applied when scaling to shorter exposure durations. The starting point for time 

scaling was an 8-hour concentration of 1 ppm. 

Data Adequacy: The preponderance of data from the key studies support an 8-hour no effect concentration of 1 ppm. 

The Leeser et al. (1990) study encompassed subjective symptoms as well as extensive medical examinations. The 

occupational monitoring study of El Ghawabi et al. (1975) in which it is believed that workers inhaling a mean 

concentration of 8 ppm may suffer mild headaches support the safety of the derived values. The values are also 

supported by a NIOSH (1976) report in which 5 ppm was identified as a no-effect concentration in the Grabois et al. 

(1954) occupational study. Additional monitoring studies support the values. 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 34 of 38 

1 

HYDROGEN CYANIDE AEGL-2 VALUES

10 minute 30 minute 1 hour 4 hour 8 hour

17 ppm 

19 mg/m3

10 ppm 

11 mg/m3

7.1 ppm 

7.8 mg/m3

3.5 ppm 

3.9 mg/m3

2.5 ppm 

2.8 mg/m3

Key References: Purser, D.A. 1984. A bioassay model for testing the incapacitating effects of exposure to 

combustion product atmospheres using cynomolgus monkeys. J. Fire Sciences 2:20-36. 

Purser, D.A., P. Grimshaw and K.R. Berrill. 1984. Intoxication by cyanide in fires: A study in monkeys using 

polyacrylonitrile. Arch. Environ. Health 39:393-400. 

Test Species/Strain/Sex/Number: Cynomolgus monkeys, 4 per exposure group (gender not stated) 

Exposure Route/Concentrations/Durations: Inhalation, 60, 100, 102, 123, 147, or 156 ppm for 30 minutes 

Effects: (30-minute exposures) 

60 ppm: increased respiratory minute volume and slight changes in EEGs near end of exposure 

100 ppm incapacitation (semi-conscious state) in 19 minutes 

102 ppm incapacitation in 16 minutes 

123 ppm incapacitation in 15 minutes 

147 ppm incapacitation in 8 minutes 

156 ppm incapacitation in 8 minutes 

Endpoint/Concentration/Rationale: The 30-minute exposure to 60 ppm, a NOAEL, was chosen because the next 

higher tested concentration, 100 ppm, resulted in incapacitation within the 30-minute exposure period. 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 6 

Interspecies: 2 – The monkey is an appropriate model for humans, the small size and higher respiratory rate of 

the monkey may result in more rapid uptake and greater sensitivity than in humans. 

Intraspecies: 3 – No specific susceptible populations were identified during monitoring studies or during the 

clinical use of nitroprusside solutions to control hypertension. The detoxifying enzyme rhodanese is present in 

all individuals including newborns. 

Modifying Factor: Not applicable 

Animal to Human Dosimetric Adjustment: Insufficient data. 

Time Scaling: Cn x t = k where n = 2 and k = 3000 ppm2·minutes based on regression analysis of timeconcentration relationships for both incapacitation times of 8 to 19 minutes and lethality data (3-60 minutes) for 

the monkey. 

Data Adequacy: Although human data are limited to primarily occupational monitoring studies, the data base on 

animal studies is good. 

The test atmosphere in the key study was supplied via a face mask to the restrained test subjects; restrained 

animals have been shown to be more sensitive than unrestrained animals to inhaled toxicants. 

Relative species sensitivity to inhaled HCN may be related to breathing rate. Compared to rodents, the slower 

breathing rate of humans and monkeys may make them less sensitive to the effects of HCN. 

Two supporting studies were located: 

1. A 30-minute exposure of rats to 55 ppm resulted in changes in lung phospholipids and lung dynamics. Use 

of an uncertainty factor of 6 results in a 30-minute AEGL-2 of 9.2 ppm which is similar to the AEGL value. 

2. Humans inhaling mean concentrations of 10 or 15 ppm in electroplating or silver-reclaiming factories for up 

to 15 years reported symptoms including headache, fatigue, effort dyspnea, and syncopes. There was no 

evidence that these symptoms occurred on the first day of employment. 

2 

3 

4 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 35 of 38 

1 

HYDROGEN CYANIDE AEGL-3 VALUES 

10 minute 30 minute 1 hour 4 hour 8 hour

27 ppm 

30 mg/m3

21 ppm 

23 mg/m3

15 ppm 

17 mg/m3

8.6 ppm 

9.7 mg/m3

6.6 ppm 

7.3 mg/m3

Key Reference: E.I. du Pont de Nemours & Co. 1981. Inhalation toxicity of common combustion gases. 

Haskell Laboratory Report No. 238-81. Haskell Laboratory, Newark, DE 

Test Species/Strain/Sex/Number: Crl:CD male rats, 10/exposure group 

Exposure Route/Concentrations/Durations: 

Inhalation 

273, 328, 340, 353, 441, 493, or 508 ppm for 5 minutes 

110, 175, 188, 204, 230, 251, 283, or 403 ppm for 15 minutes 

128, 149, 160, 183, 222, or 306 ppm for 30 minutes 

76, 107, 154, 183, or 222 ppm for 60 minutes 

Effects (LC01 values were calculated by Haskell Laboratory using probit analysis): 

5-minute LC01: 283 ppm 

15-minute LC01: 138 ppm 

30-minute LC01: 127 ppm 

60-minute LC01: 88 ppm 

Endpoint/Concentration/Rationale: 

The LC01, the threshold for lethality, was used as the basis for the derivation of the AEGL-3. 

The 15-minute LC01 was used to calculate the 10 minute value, the 30-minute LC01 was used for the 30-minute 

value, and the 60-minute LC01 was used to derive the 1-, 4- and 8-hour AEGL-3 values. 

Uncertainty Factors/Rationale: 

Total uncertainty factor: 6 

Interspecies: 2 - LC50 values for the same exposure durations for several species (rat, mouse, and rabbit) were 

within a factor of approximately 1.5 of each other. Based on relative respiration rates, humans are expected to be 

less sensitive than rodents. The mechanism is the same for all species. 

Intraspecies: 3 - No specific susceptible populations were identified during monitoring studies or during the 

clinical use of nitroprusside solutions to control hypertension. The detoxifying enzyme rhodanese is present in 

all individuals including newborns. 

Modifying Factor: Not applicable 

Animal to Human Dosimetric Adjustment: Insufficient data. 

Time Scaling: Cn x t = k where n = 2.6 was derived from empirical data and used in a regression analysis of 

time-concentration relationships for rat LC50 values conducted at time periods of 5, 15, 30, and 60 minutes in the 

key study. However, the 15-, 30-, and 60-minute values were calculated directly from the empirical (LC01) data. 

The k value of 52069.5 ppm2.6·minutes, based on the 15-minute LC01, was used for the 10-minute value and the k 

value of 64656.6 ppm2.6·minutes, based on the 1-hour LC01, was used for the 4- and 8-hour AEGL-3 values. 

Data Adequacy: The study was well conducted. The HCN concentrations were continuously monitored using 

infrared spectrophotometry and validated by gas chromatography. 

One supporting study was located: exposure of rats to 30 ppm for 24 hours resulted in lung congestion but no 

deaths. Use of a total uncertainty factor of 6 and extrapolation across time to 30 minutes results in a 30-minute 

AEGL-3 of 22 ppm which is similar to the derived value of 21 ppm. 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 36 of 38

1 APPENDIX E: Category Plots for Cyanide Salts 

2 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 37 of 38 

1 

2 

3 

4 

5 

1 

10 

100 

mg/m3

0 60 120 180 240 300 360 420 480 

min

Human - No Ef

Human - Disco

Human - Disab

Animal - No Ef

Animal - Disco

Animal - Disab

Animal - Partia

Animal - Letha

AEGL

Sodium Cyanide AEGLs

AEGL-3

AEGL-1

AEGL-2

6 
SELECTED CYANIDE SALTS Proposed: 04-2009/ Page 38 of 38 

1 

10 

100 

mg/m3

0 60 120 180 240 300 360 420 480 

min

Human - No Ef

Human - Disco

Human - Disab

Animal - No Ef

Animal - Disco

Animal - Disab

Animal - Partia

Animal - Letha

AEGL

Potassium Cyanide AEGLs

AEGL-3

AEGL-1

AEGL-2

1 

1 

10 

100 

mg/m3

0 60 120 180 240 300 360 420 480 

min

Human - No Ef

Human - Disco

Human - Disab

Animal - No Ef

Animal - Disco

Animal - Disab

Animal - Partia

Animal - Letha

AEGL

Calcium Cyanide AEGLs

AEGL-3

AEGL-1

AEGL-2

2