Page 143 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Appendix C

Derivation of AEGL Values for Selected Chloroformates

Methyl Chloroformate

Derivation of AEGL-1 Values for Methyl Chloroformate

Insufficient data were available on methyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for Methyl Chloroformate

Insufficient data were available on methyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for methyl chloroformate by 3.

Calculations:
10-min AEGL-2:	12 ppm ÷ 3 = 4.0 ppm
30-min AEGL-2:	8.5 ppm ÷ 3 = 2.8 ppm
1-h AEGL-2:	6.7 ppm ÷ 3 = 2.2 ppm
4-h AEGL-2:	4.2 ppm ÷ 3 = 1.4 ppm
8-h AEGL-2:	2.1 ppm ÷ 3 = 0.70 ppm

Derivation of AEGL-3 Values for Methyl Chloroformate

Key study:	Hoechst. 1986. Chloroformic Acid Methyl Ester. Inhalation Toxicity in the Flow Through System in Male and Female SPF Wistar Rats. 4-hour LC₅₀. Hollander, H., Weigland, W, Mayer, D., Langer, K.H. Hoechst Pharmaceutical Research Toxicology. Report No. 86.0432. April 11, 1986.

Page 144 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Toxicity end point:	Lethality threshold in rats (4-h BMCL₀₅ of 42.4 ppm)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (42.4 ppm)³ × 4 h = 304,900 ppm-h (42.4 ppm)¹ × 4 h = 170 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	C³ × 0.167 h = 304,900 ppm-h C³ = 1,825,748 ppm C = 122 ppm 122 ppm ÷ 10 = 12 ppm
30-min AEGL-3:	C³ × 0.5 h = 304,900 ppm-h C³ = 609,800 ppm C = 84.8 ppm 84.8 ppm ÷ 10 = 8.5 ppm
1-h AEGL-3:	C³ × 1 h = 304,900 ppm-h C³ = 304,900 ppm C = 67.3 ppm 67.3 ppm ÷ 10 = 6.7 ppm
4-h AEGL-3:	42.4 ppm ÷ 10 = 4.2 ppm
8-h AEGL-3:	C¹ × 8 h = 170 ppm-h C¹ = 21.2 ppm C = 21.2 ppm 21 ppm ÷ 10 = 2.1 ppm

Ethyl Chloroformate

Derivation of AEGL-1 Values for Ethyl Chloroformate

Insufficient data were available on ethyl chloroformate to derive AEGL-1 values, so no values are recommended.

Page 145 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Derivation of AEGL-2 Values for Ethyl Chloroformate

Insufficient data were available on ethyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for ethyl chloroformate by 3.

Calculations:
10-min AEGL-2:	8.8 ppm ÷ 3 = 2.9 ppm
30-min AEGL-2:	6.1 ppm ÷ 3 = 2.0 ppm
1-h AEGL-2:	4.8 ppm ÷ 3 = 1.6 ppm
4-h AEGL-2:	1.2 ppm ÷ 3 = 0.40 ppm
8-h AEGL-2:	0.60 ppm ÷ 3 = 0.20 ppm

Derivation of AEGL-3 Values for Ethyl Chloroformate

Key study:	Vernot, E.H., J.D. MacEwen, C.C. Haun, and E.R. Kinkead. 1977. Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicol. Appl. Pharmacol. 42:417-424.
Toxicity end point:	Lethality threshold; estimated LC₀₁ (LC₅₀ ÷ 3) from a 1-h exposure in male rats. LC₅₀ = 145 ppm; 145 ppm ÷ 3 = 48.3 ppm (point of departure)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (48.3 ppm)³ × 1 h = 112,769 ppm-h (48.3 ppm)¹ × 1 h = 48.3 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors

Page 146 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

10-min AEGL-3:	C³ × 0.167 h = 112,769 ppm-h C³ = 675,263 ppm C = 87.7 ppm 87.7 ppm ÷ 10 = 8.8 ppm
30-min AEGL-3:	C³ × 0.5 h = 112,769 ppm-h C³ = 225,538 ppm C = 60.9 ppm 60.9 ppm ÷ 10 = 6.1 ppm
1-h AEGL-3:	48.3 ppm ÷ 10 = 4.8 ppm
4-h AEGL-3:	C¹ × 4 h = 48.3 ppm-h C¹ = 12 ppm C = 12 ppm 12 ppm ÷ 10 = 1.2 ppm
8-h AEGL-3:	C¹ × 8 h = 48.3 ppm-h C¹ = 6.0 ppm C = 6.0 ppm 6.0 ppm ÷ 10 = 0.60 ppm

Isopropyl Chloroformate

Derivation of AEGL-1 Values for Isopropyl Chloroformate

Insufficient data were available on isopropyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for Isopropyl Chloroformate

Insufficient data were available on isopropyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for isopropyl chloroformate by 3.

Calculations:
10-min AEGL-2:	11 ppm ÷ 3 = 3.7 ppm
30-min AEGL-2:	11 ppm ÷ 3 = 3.7 ppm
1-h AEGL-2:	9.1 ppm ÷ 3 = 3.0 ppm

Page 147 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

4-h AEGL-2:	5.7 ppm ÷ 3 = 1.9 ppm
8-h AEGL-2:	3.8 ppm ÷ 3 = 1.3 ppm

Derivation of AEGL-3 Values for Isopropyl Chloroformate

Key study:	Collins, C.J., and B.G. Proctor. 1984. A 5-day Range-Finding Inhalation Toxicity Study of Isopropyl Chloroformate in the Albino Rat. Draft Report. Prepared by Bio-Research Laboratories, Ltd.: Quebec, Canada. Prepared for PPG Industries, Pittsburgh, PA.
Toxicity end point:	Concentration causing no mortality in male and female rats exposed for 6 h/day for 5 days (50 ppm)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (50 ppm)³ × 6 h = 750,000 ppm-h (50 ppm)¹ × 6 h = 300 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	11 ppm (set equal to 30-min AEGL-3 value, because of the uncertainty associated with extrapolating a 6-h point-of-departure to a 10-min value)
30-min AEGL-3:	C³ × 0.5 h = 750,000 ppm-h C³ = 1,500,000 ppm C = 114 ppm 114 ppm ÷ 10 = 11 ppm
1-h AEGL-3:	C³ × 1 h = 750,000 ppm-h C³ = 750,000 ppm C = 90.9 ppm 90.9 ppm ÷ 10 = 9.1 ppm

Page 148 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

4-h AEGL-3:	C³ × 4 h = 750,000 ppm-h C³ = 187,500 ppm C = 57.2 ppm 57.2 ppm ÷ 10 = 5.7 ppm
8-h AEGL-3:	C¹ × 8 h = 300 ppm-h C¹ = 37.5 ppm 37.5 ppm ÷ 10 = 3.8 ppm

n-Propyl Chloroformate

Derivation of AEGL-1 Values for n-Propyl Chloroformate

Insufficient data were available on propyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for n-Propyl Chloroformate

AEGL-2 values for propyl chloroformate were set equal to AEGL-2 values for isopropyl chloroformate, because of the inadequate data on propyl chloroformate and the similar toxicity of the two chemicals.

Calculations:
10-min AEGL-2:	3.7 ppm
30-min AEGL-2:	3.7 ppm
1-h AEGL-2:	3.0 ppm
4-h AEGL-2:	1.9 ppm
8-h AEGL-2:	1.3 ppm

Derivation of AEGL-3 Values for n-Propyl Chloroformate

AEGL-3 values for n-propyl chloroformate were set equal to AEGL-3 values for isopropyl chloroformate, because of the inadequate data on n-propyl chloroformate and the similar toxicity of the two chemicals.

Page 149 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Calculations:
10-min AEGL-3:	11 ppm
30-min AEGL-3:	11 ppm
1-h AEGL-3:	9.1 ppm
4-h AEGL-3:	5.7 ppm
8-h AEGL-3:	3.8 ppm

Allyl Chloroformate

Derivation of AEGL-1 Values for Allyl Chloroformate

Insufficient data were available on allyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for Allyl Chloroformate

Insufficient data were available on allyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for allyl chloroformate by 3.

Calculations:
10-min AEGL-2:	3.8 ppm ÷ 3 = 1.3 ppm
30-min AEGL-2:	2.6 ppm ÷ 3 = 0.87 ppm
1-h AEGL-2:	2.1 ppm ÷ 3 = 0.70 ppm
4-h AEGL-2:	0.53 ppm ÷ 3 = 0.18 ppm
8-h AEGL-2:	0.26 ppm ÷ 3 = 0.09 ppm

Derivation of AEGL-3 Values for Allyl Chloroformate

Key study:

Stillmeadow Inc. 1987. Rat Acute Inhalation Toxicity: Allyl Chloroformate. Stillmeadow, Inc. Biological Testing Laboratory: Houston, TX. Project No. 4438-86. Report Submitted to PPG

Page 150 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

	Industries, Inc.: Chicago, IL. February 19, 1987. OTS0536028.
Toxicity end point:	Lethality threshold (1-h rat BMCL₀₅ = 21 ppm)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (21 ppm)³ × 1 h = 9,261 ppm-h (21 ppm)¹ × 1 h = 21 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	C³ × 0.167 h = 9,261 ppm-h C³ = 55,455 ppm C = 38 ppm 38 ppm ÷ 10 = 3.8 ppm
30-min AEGL-3:	C³ × 0.5 h = 9,261 ppm-h C³ = 18,522 ppm C = 26.4 ppm 26.4 ppm ÷ 10 = 2.6 ppm
1-h AEGL-3:	21 ppm ÷ 10 = 2.1 ppm
4-h AEGL-3:	C¹ × 4 h = 21 ppm-h C¹ = 5.25 ppm C = 5.25 ppm 5.25 ppm ÷ 10 = 0.53 ppm
8-h AEGL-3:	C¹ × 8 h = 21 ppm-h C¹ = 2.63 ppm C = 2.63 ppm 2.63 ppm ÷ 10 = 0.26 ppm

n-Butyl Chloroformate, Isobutyl
Chloroformate, and sec-Butyl Chloroformate

Data were insufficient to derive AEGL values for isobutyl or sec-butyl chloroformate. Because these two compounds are structural analogs of n-butyl

Page 151 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

chloroformate and because they appear to have similar toxicity, the AEGL values for n-butyl chloroformate were adopted for these chemicals. The section below shows how the values for n-butyl chloroformate were derived.

Derivation of AEGL-1 Values for n-Butyl Chloroformate

Insufficient data were available on n-butyl chloroformate to derive AEGL-1 values, so no values are recommended. No values are also recommended for isobutyl chloroformate or sec-butyl chloroformate.

Derivation of AEGL-2 Values for n-Butyl Chloroformate

Insufficient data were available on n-butyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for n-butyl chloroformate by 3. The values were also applied to isobutyl chloroformate and sec-butyl chloroformate.

Calculations:
10-min AEGL-2:	12 ppm ÷ 3 = 4.0 ppm
30-min AEGL-2:	8.4 ppm ÷ 3 = 2.8 ppm
1-h AEGL-2:	6.7 ppm ÷ 3 = 2.2 ppm
4-h AEGL-2:	1.7 ppm ÷ 3 = 0.57 ppm
8-h AEGL-2:	0.83 ppm ÷ 3 = 0.28 ppm

Derivation of AEGL-3 Values for n-Butyl Chloroformate

Key study:	BASF. 1970. BASF AG, Gewerbehygienisch-Pharmakologisches Institut. n-Butylchlorokohlensaureester-Gewerbetoxikologische Vorprufung. Unpublished Report No. XIX 352
Toxicity end point:	Estimated 1-h lethality threshold in rats (66.7 ppm) 4/10 rats died after exposure at 200 ppm for 1 h; lethality threshold was estimated by taking one-third of that concentration (200 ppm ÷ 3 = 66.7 ppm).

Page 152 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (66.7 ppm)³ × 1 h = 296,741 ppm-h (66.7 ppm)¹ × 1 h = 66.7 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	C³ × 0.167 h = 296,741 ppm-h C³ = 1,776,892 ppm C = 121 ppm 121 ppm ÷ 10 = 12 ppm
30-min AEGL-3:	C³ × 0.5 h = 296,741 ppm-h C³ = 593,482 ppm C = 84.0 ppm 84.0 ppm ÷ 10 = 8.4 ppm
1-h AEGL-3:	66.7 ppm ÷ 10 = 6.7 ppm
4-h AEGL-3:	C¹ × 4 h = 66.7 ppm-h C¹ = 16.8 ppm C = 16.8 ppm 16.8 ppm ÷ 10 = 1.7 ppm
8-h AEGL-3:	C¹ × 8 h = 66.7 ppm-h C¹ = 8.34 ppm C = 8.34 ppm 8.34 ppm ÷ 10 = 0.83 ppm

AEGL-3 values for n-butyl chloroformate were also applied to isobutyl chloroformate and sec-butyl chloroformate.

Benzyl Chloroformate

Derivation of AEGL-1 Values for Benzyl Chloroformate

Insufficient data were available on benzyl chloroformate to derive AEGL-1 values, so no values are recommended.

Page 153 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Derivation of AEGL-2 Values for Benzyl Chloroformate

Insufficient data were available on benzyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for benzyl chloroformate by 3.

Calculations:
10-min AEGL-2:	3.7 ppm ÷ 3 = 1.2 ppm
30-min AEGL-2:	3.7 ppm ÷ 3 = 1.2 ppm
1-h AEGL-2:	2.9 ppm ÷ 3 = 0.97 ppm
4-h AEGL-2:	1.9 ppm ÷ 3 = 0.63 ppm
8-h AEGL-2:	0.93 ppm ÷ 3 = 0.31 ppm

Derivation of AEGL-3 Values for Benzyl Chloroformate

Key study:	BASF. 1990. Study on the Acute Inhalation Toxicity LC₅₀ of Benzyl Chloroformate as a Vapor in Rats, 4-Hour Exposure. Project No. 13I0674/887075. Unpublished report, BASF Aktiengesellschaft, Experimental Toxicology and Ecology: Ludwigshafen, Germany. February 15, 1990.
Toxicity end point:	Concentration causing no mortality in 4-h rat study (18.6 ppm)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (18.6 ppm)³ × 4 h = 25,739 ppm-h (18.6 ppm)¹ × 4 h = 74.4 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors

Page 154 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

10-min AEGL-3:	3.7 ppm (set equal to 30-min AEGL-3 value, because of the uncertainty associated with extrapolating a 4-h point-of-departure to a 10-min value)
30-min AEGL-3:	C³ × 0.5 h = 25,739 ppm-h C³ = 51,478 ppm C = 37.2 ppm 37.2 ppm ÷ 10 = 3.7 ppm
1-h AEGL-3:	C³ × 1 h = 25,739 ppm-h C³ = 25,739 ppm C = 29.5 ppm 29 ppm ÷ 10 = 2.9 ppm
4-h AEGL-3:	18.6 ppm ÷ 10 = 1.9 ppm
8-h AEGL-3:	C¹ × 8 h = 74.4 ppm-h C¹ = 9.3 ppm C = 9.3 ppm 9.3 ppm ÷ 10 = 0.93 ppm

Phenyl Chloroformate

Derivation of AEGL-1 Values for Phenyl Chloroformate

Insufficient data were available on phenyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for Phenyl Chloroformate

Insufficient data were available on phenyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for phenyl chloroformate by 3.

Calculations:
10-min AEGL-2:	0.72 ppm ÷ 3 = 0.24 ppm
30-min AEGL-2:	0.72 ppm ÷ 3 = 0.24 ppm
1-h AEGL-2:	0.57 ppm ÷ 3 = 0.19 ppm

Page 155 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

4-h AEGL-2:	0.36 ppm ÷ 3 = 0.12 ppm
8-h AEGL-2:	0.18 ppm ÷ 3 = 0.06 ppm

Derivation of AEGL-3 Values for Phenyl Chloroformate

Key studies:	BASF. 1990. Study on the Acute Inhalation Toxicity LC₅₀ of Phenyl Chloroformate as a Vapor in Rats, 4-Hour Exposure. Project No. 13I0675/887076. Unpublished report, BASF Aktiengesellschaft, Experimental Toxicology and Ecology: Ludwigshafen, Germany. January 18, 1990.
	Hoechst. 1989. Chloroformic Acid Phenyl Ester. Aerosol Inhalation Toxicity in Male and Female SPF Wistar Rats. 4-Hour LC₅₀. Hofmann, T. Hoechst Pharmaceutical Research Toxicology. Report No. 89.0761. April 26, 1989.
Toxicity end point:	Lethality threshold (4-h rat BMCL₀₅ = 3.6 ppm)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (3.6 ppm)³ × 4 h = 186.7 ppm-h (3.6 ppm)¹ × 4 h = 14.4 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	0.72 ppm (set equal to 30-min AEGL-3 value, because of the uncertainty associated with extrapolating a 4-h point-of-departure to a 10-min value)
30-min AEGL-3:	C³ × 0.5 h = 186.7 ppm-h C³ = 373.4 ppm C = 7.2 ppm 7.2 ppm ÷ 10 = 0.72 ppm

Page 156 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

1-h AEGL-3:	C³ × 1 h = 186.7 ppm-h C³ = 186.7 ppm C = 5.7 ppm 5.7 ppm ÷ 10 = 0.57 ppm
4-h AEGL-3:	3.6 ppm ÷ 10 = 0.36 ppm
8-h AEGL-3:	C¹ × 8 h = 14.4 ppm-h C¹ = 1.8 ppm C = 1.8 ppm 1.8 ppm ÷ 10 = 0.18 ppm

2-Ethylhexyl Chloroformate

Derivation of AEGL-1 Values for 2-Ethylhexyl Chloroformate

Insufficient data were available on 2-ethylhexyl chloroformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for 2-Ethylhexyl Chloroformate

Insufficient data were available on 2-ethylhexyl chloroformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for 2-ethylhexyl chloroformate by 3.

Calculations:
10-min AEGL-2:	3.6 ppm ÷ 3 = 1.2 ppm
30-min AEGL-2:	3.6 ppm ÷ 3 = 1.2 ppm
1-h AEGL-2:	2.9 ppm ÷ 3 = 0.97 ppm
4-h AEGL-2:	1.8 ppm ÷ 3 = 0.60 ppm
8-h AEGL-2:	0.91 ppm ÷ 3 = 0.30 ppm

Derivation of AEGL-3 Values for 2-Ethylhexyl Chloroformate

Key study:

BASF. 1985. Acute Inhalation Toxicity LC₅₀ for a 4-Hour Exposure (Rats), Vapor Test of 2-Ethylhexyl Chloroformate. Unpublished report, BASF Aktiengesellschaft, Experimental Toxicology

Page 157 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

	and Ecology: Ludwigshafen, Germany. February 8, 1985.
Toxicity end point:	Lethality threshold (4-h rat BMCL₀₅ [18.1 ppm])
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (18.1 ppm)³ × 4 h = 23,719 ppm-h (18.1 ppm)¹ × 4 h = 72.4 ppm-h
Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	3.6 ppm (set equal to 30-min AEGL-3 value, because of the uncertainty associated with extrapolating a 4-h point-of-departure to a 10-min value)
30-min AEGL-3:	C³ × 0.5 h = 23,719 ppm-h C³ = 47,438 ppm C = 36.2 ppm 36.2 ppm ÷ 10 = 3.6 ppm
1-h AEGL-3:	C³ × 1 h = 23,719 ppm-h C³ = 23,719 ppm C = 28.7 ppm 28.7 ppm ÷ 10 = 2.9 ppm
4-h AEGL-3:	18.6 ppm ÷ 10 = 1.8 ppm
8-h AEGL-3:	C¹ × 8 h = 72.4 ppm-h C¹ = 9.1 ppm C = 9.1 ppm 9.1 ppm ÷ 10 = 0.91 ppm

Page 158 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Ethyl Chlorothioformate

Derivation of AEGL-1 Values for Ethyl Chlorothioformate

Insufficient data were available on ethyl chlorothioformate to derive AEGL-1 values, so no values are recommended.

Derivation of AEGL-2 Values for Ethyl Chlorothioformate

Insufficient data were available on ethyl chlorothioformate to derive AEGL-2 values. In the absence of relevant data, AEGL-2 values were estimated by dividing the AEGL-3 values for ethyl chlorothioformate by 3.

Calculations:
10-min AEGL-2:	3.0 ppm ÷ 3 = 1.0 ppm
30-min AEGL-2:	3.0 ppm ÷ 3 = 1.0 ppm
1-h AEGL-2:	2.4 ppm ÷ 3 = 0.80 ppm
4-h AEGL-2:	1.5 ppm ÷ 3 = 0.50 ppm
8-h AEGL-2:	0.75 ppm ÷ 3 = 0.25 ppm

Derivation of AEGL-3 Values for Ethyl Chlorothioformate

Key study:	Stauffer Chemical Company. 1983. Acute Inhalation Toxicity of Ethyl Chlorothioformate in Rats (T-10710). Environmental Health Center Inhalation Facility. Stauffer Chemical Company: Farmington, CT. OTS0538464.
Toxicity end point:	Estimated 4-h lethality threshold of 15 ppm in rats (LC₅₀ = 45 ppm; 45 ppm ÷ 3)
Time scaling:	Cⁿ × t = k; default values of n = 3 for extrapolating to shorter durations and n = 1 for extrapolating to longer durations (NRC 2001). (15 ppm)³ × 4 h = 13,500 ppm-h (15 ppm)¹ × 4 h = 60 ppm-h

Page 159 Cite Bookmark

Suggested Citation: "Appendix C Derivation of AEGL Values for Selected Chloroformates." National Academies of Sciences, Engineering, and Medicine. 2016. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 20. Washington, DC: The National Academies Press. doi: 10.17226/23634.

Uncertainty factors:	3 for interspecies differences 3 for intraspecies variability
Calculations:	Point of departure ÷ product of the uncertainty factors
10-min AEGL-3:	3.0 ppm (set equal to 30-min AEGL-3 value, because of the uncertainty associated with extrapolating a 4-h point-of-departure to a 10-min value)
30-min AEGL-3:	C³ × 0.5 h = 13,500 ppm-h C³ = 27,000 ppm C = 30 ppm 30 ppm ÷ 10 = 3.0 ppm
1-h AEGL-3:	C³ × 1 h = 13,500 ppm-h C³ = 13,500 ppm C = 23.8 ppm 23.8 ppm ÷ 10 = 2.4 ppm
4-h AEGL-3:	15 ppm ÷ 10 = 1.5 ppm
8-h AEGL-3:	C¹ × 8 h = 60 ppm-h C¹ = 7.5 ppm C = 7.5 ppm 7.5 ÷ 10 = 0.75 ppm