Emergency Planning: Critical Evaluation of Proposed AEGLs for Ammonia
Robert A. Michaels
KAM TRAC Corp., Schenectady, NY 12309
National Advisory Committee’s Acute Exposure Guideline Levels (AEGLs) for ammonia are critically evaluated. The technical bases for concern about AEGL-2 and AEGL-3 values derived by the committee are summarized recommendations made.
and
“During the 20th century, humanity has almost quadrupled its numbers. Although many factors have fostered this unprecedented expansion, its continuation during the past generation would not have been at all possible without a widespread, yet generally unappreciated, activity: the synthesis of ammonia” [22].
At its June 9, 1997 meeting, after five meetings and a year of deliberations about ammonia, the National Advisory Committee on Acute Exposure Guideline Levels (NAC AEGL) decided to propose AEGL values for ammonia, which were lower than RAM TRAC recommendations [8, 9, 16, 17, 18, 19], as shown in Table 1. The values are generally too low by a factor of approximately 4.5, producing Emergency Planning Zone areas generally 20 times greater than necessary around facilities exceeding threshold quantities of ammonia on-site.
The proposed values will be published in the Federal Register, and the Committee will then receive and formally respond to comments from members of the public. This article critically evaluates NAC AEGL's actions, and summarizes the technical bases for concern about AEGL-2 and AEGL-3 values to be proposed by the Committee, as well as RAM TRAC comments [76, 17, 18, 19] on the values. Although NAC AEGL may “finalize” the AEGL values de-
TABLE 1. AEGL Values for Ammonia
Concentration (ppm-v) by Exposure Duration
AEGL Parameter Smin 30min 1h 4h 8h NAC AEGL Proposals 1 25 25 25 25 25 2 380 160 110 110 110 3 3,800 1,600 1,100 550 390 RAM TRAC Recommendations 2 1,704 696 429 246 174 3 16,869 6,887 4,870 2,435 1,722
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spite the arguments summarized herein, further review will be undertaken by an independent entity, namely, the Committee on Toxicology of the U.S. National Research Council (NRC).
AEGL-3
m derive AEGL-3 values, the Committee properly used human data for range-finding, and bioassay data to flesh out the dose-response curve over the full eight-hour range of exposure durations of concern [12]. However, the Committee applied this proper approach in an improper manner. For range-finding, the Commitee gave undue credence to Henderson and Haggard [4], which cites no source of its reported lethality concentration of 5,000 to 10,000 ppm-v with five to 10 minutes of exposure. This exposure range is apparently anecdotal, and apparently predates World War 1[5, 6, 20], when ammonia was marketed to military buyers interested in its high toxic potency against enemy soldiers engaged in trench warfare. Whereas such “data” should have been accorded a low threshold for refutation, the Committee instead adhered to this lethality exposure range, even when presented with reconstructions of several relatively recent industrial accidents involving ammonia release [2, 10, 11, 14], each conflicting with the preWorld War I “data” (Figure 1). A further reason for rejecting the old lethality exposure range is its lack of concordance with bioassays involving five animal species, producing LC., and LC,, values scaled to human equivalent concentrations (HECs). These lethality values are, however, in accordance with the accident reconstruction data (Figure 2). In reajecting accident reconstructions which rely upon air modeling, the Committee improperly overemphasized uncertainties inherent in air modeling [7, 13], even though the Risk Management Program (RMP) being implemented by the Committee depends critically and intrinsically upon air modeling. Moreover, the Committee failed to understand that meta-analysis of multiple accidents can dramatically reduce uncertainties inherent in modeling single accidents, as should be evident from Figure 1.
The flawed rationale for preferring anecdotal lethality data predating World War I over a wealth of accident reconstruction data for range-finding provided the Committee with a basis, spuriously, for deriving AEGL-3 values using mouse data [5]. Although citing Ten Berge et al [23], the Committee ignored the authors’ caveat: “ Mice are often more sensitive than other mammals...experiments using
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90,000 N ‘ ‘ Gb eneccrassersnneannsenossnsasiessii@eeeSE \ \ \ [=-O-- Farmland acddent 70,000 } -- 4; JO mean of four accident reconstructions = 60,000 £ =-0-- Potchefstroom scident LC rf i) & somo}. £ J=-0---Mulder and Van der Zam (1967) i 8 s § gE 5 § ° Smin. 30min, th on eh exposure duration FIGURE 1 Lethality range-finding based upon accident re-
construction vs. anecdotal data predating World War I.
mice do not provide an appropriate basis for predicting quantitatively the mortality response in humans.” The Committee’s assumption that humans are as sensitive as mice to ammonia was applied to the Potchefstroom accident, in which 18 people died. Under the Committee’s assumption, at least 180 people should have died [76]. Thus, human experience refuted the Committee’s use of the mouse data. Rat data are more relevant, as acknowledged by NRC’s Committee on Toxicology [12], and rats [7] were three times more tolerant of ammonia than mice [5], as acknowledged by ORNL. Even using mice, however, the Committee had difficulty deriving AEGL-3 values below concentrations assumed to be lethal for humans. Upwardly scaling ammonia concentrations to which mice were exposed to HEC values produced AEGL-3 values too high relative to the pre-World War I data selected for lethality range-finding. Consequently, the Committee declined to do HEC scaling, although guidelines of NRC [12] and EPA [24] require it. The resulting values were still so high that their further reduction by a safety factor of three was deemed necessary to protect “sensitive subpopulations” not already protected by mouse LC,,, (one-per-thousand lethality) values, which are already very protective. Finally, the Committee claimed that it could produce similar AEGL-3 values using rat data [Z], but required an interspecies safety factor of three [73], whereas no such factor is justified given the accident reconstruction data (see Figures 1 and 2).
Resolution of AEGL-3 differences
Resolution of the 4.4-fold difference between RAM TRAC and NAC AEGL recommendations can be achieved via two steps, restoring consistency of Committee procedures with those specified by the EPA [24] and NRC’s Committee on
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Toxicology [12]. First, HEC adjustment of mouse [5] or rat [1] LC,,, data (not to be confused with means of multiple LCs and LC, bioassay data depicted in Figure 2) to HEC values would multiply AEGL-3 values to be proposed by the Committee by a factor of 2.7. If only this adjustment were implemented, this would bring AEGL-3 values to within two-thirds of RAM TRAC recommendations, which were derived based upon halving the five-minute zeromortality level of 33,737 ppm-v in the Potchefstroom accident reconstruction. This leaves a difference of approximately 1.6-fold.
Virtually all of this remaining 1.6-fold difference can be eliminated by a second step, that is, adopting the Appelman etal. rat LC, data [7]; approximately mouse LC,, data times three) with an interspecies uncertainty factor of two rather than three proposed by NAC AEGL. This produces an approximate 1.5-fold increase in NAC AEGL proposed values. This adjustment is technically justified based upon accident reconstruction data, which suggest higher human. tolerance to ammonia than assumed by the Committee based upon pre-World War I data. Accident reconstruction data indicate the absence of any need to apply an interspecies uncertainty factor relative to rat LC, data (not relative to LCs) and LC,, data depicted in Figure 2). The resulting harmony of AEGL-3 values with RAM TRAC recommendations would decrease the area of Emergency Planning Zones around ammonia facilities by a factor of 20-fold, with commensurate savings in community emergency planning costs and reductions in the difficulty of permitting or repermitting facilities exceeding threshold quantities of ammonia on-site.
AEGL-2
With respect to irreversible injury and inability to escape from released ammonia (AEGL-2), the Committee deviated
accident .reconstructions.).......
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a 50,000 } =
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FIGURE2 Lethality range-finding via bioassays of five species, reconstruction of four industrial acci-
dents, and anecdotal data predating World War I.
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from its defined criteria, deriving values based upon volunteer's perception that concentrations to which they were exposed were “intolerable” [13, 25]. However, concentrations perceived in the context of voluntary exposure as “intolerable” caused neither injury (not even minor injury) nor incapacitation [25], and were greatly exceeded in another study of volunteers, also with neither injury nor incapacitation [27].
The proposed AEGL-2 is 160 ppm-v at 30 min and 110 ppm-v thereafter based upon the need to preserve the ability to escape. The 30-min concentration should not be reduced, however, for longer-term exposures of 1 h, 4 h, and 8 h. These values should remain at 160 ppm-y, consistent with NAC AEGL policy. Thirty minutes is a traditional period assumed for escape from chemical emergencies, and is embodied in the Immediately Dangerous to Life and Health (IDLH) parameter of the National Institute of Occupational and Industrial Health (NIOSH). Moreover, given the extreme volatility and fugacity of ammonia, ammonia releases can be expected to have completely dissipated within 30 min following a release (for example, the preponderance of ammonia dissipated within 10 min at Potchefstroom).
Thus, the generally reasonable 30-minutes escape-time assumption is also specifically reasonable, if not more than reasonable, in the case of ammonia. As ORNL [73] indicated, the “immediate response to individuals exposed to severe irritating concentrations of ammonia is to escape Srom the area’ (August draft, p. 33; emphasis added). Thus, if 160 ppm-v is regarded as a concentration that would permit escape within 30 min, it should also permit escape within 1 h, 4 h, or 8 h, and under the reasonable assumption that no more than 30 min would be required for escape (of both people and ammonia).
Accordingly, at the suggestion of the ammonia chemical manager (at the September 17, 1996 meeting; [9, 75]), the Committee decided to maintain AEGL-2 levels constant beyond 30 min, except when toxic effects beyond 30 min could be demonstrated. However, in setting AEGL-2 values for ammonia at the June-1997 meeting, the Committee denied having established this policy. Yet, during discussion of a constant value beyond 30 min, the Chair began to indicate that “this would be consistent with...” and then stopped himself, apparently from referring to the Committee’s prior policy, recalling its current denial that the prior policy existed. However, all Committee actions eventually can be checked, because under rules of the U. S. Federal Advisory Committee Act (FACA), tapes of Committee deliberations are public documents. Such checking has just now become possible, because previously denied requests under the Freedom of Information Act for transcripts of earlier NAC AEGL proceedings finally have been produced in accordance with the law.
Resolution of AEGL-2 differences
Resolution of differences between RAM TRAC and NAC AEGL recommendations should begin with Committee adherence to its definition of AEGL-2. AEGL-2 values should be derived to protect against irreversible injury or incapacity to escape [12, 13]. Further, the Committee should adhere to its policy of maintaining AEGL-2 values constant beyond 30 min, except if necessary to reduce such values to protect against toxic effects associated with prolonged
136 Summer 1998
exposure. This step would bring AEGL-2 values to 160 ppm-v at exposure durations of 30 min or longer. A third step would be for the Committee to adopt the 30-min value of 500 ppm-v [27], which produced neither injury nor incapacity to escape among volunteers exposed to it. This would bring the Committee into the range of RAM TRAC recommendations (500 ppm-v vs. 696 ppm-v at 30 min). If the Committee maintained 500 ppm-v at 1 h, 4 h, and 8h, then its values would exceed RAM TRAC recommendations. Thus, complete harmonization at the 1-h, 4-h, and 8-h exposure durations consistent with Committee definitions and policies should be possible; whereas, harmonization at the 5- and 30-min durations would be substantial.
LITERATURE CITED
1. Appelman, L. M., W. F. Ten Berge, and P. G. Reuzel, “Acute Inhalation Toxicity Study of Ammonia in Rats with Variable Exposure Periods,” American Ind. Hygiene Association J., 43, 662 (1982).
2. Environ., “Letter to NAC AEGL from James Skillen (The Fertilizer Institute; Washington, DC),” trans mitting letter report from R. B. Kapuscinski re: AEGL Values for Ammonia, including Attachment A: “Dose Reconstruction Modeling for Recent Ammonia Accident,” 8 pp. (Feb. 14, 1997).
3, Flury, F., “Moderne Gewerbliche Vergiftungen in Pharmakologisch-Toxicologischer Hinsicht (Pharmacological-Toxicological Aspects of Intoxicants in Modern Industry, Translated from German), “ Arch. Exp. Pathol. Pharmakol., 138, 65-(1928).
4. Henderson, Y., and W. W. Haggard, Noxious Gases, Chemical Catalogue Company, Inc., New York, Vol. 87, pp. 113-126 (1927 and 1943).
5. Kapeghian, J. C., et al, “Acute Inhalation Toxicity of Ammonia in Mice,” Bull. of Environmental Contamination and Toxicology, 29, 371 (1982).
6. Lehman, K. B., “Experimentelle Studien uber den Einfluss technisch ind hygienisch wichtiger Gase und Dampfe auf den Organismus,” Archiv fur Hygiene, 5, 1 (1886).
7. Mazzola, C. A., “Potchefstroom Dose Reconstruction: Inherent Uncertainties that Significantly Limit Effective Application to Human Health Standards Process,” Stone & Webster Engineering Corp., 32 pp. (May 1997).
8. Michaels, R. A., “Emergency Planning Issues Relating to Ammonia,” in Proc. of the 19th Ann. Meeting of the Int. Inst. of Ammonia Refrigeration, New Orleans, LA; IIAR, Washington, DC, pp. 144-188 (Mar. 23-26, 1997a).
9. Michaels, R. A., “Ammonia Under the Safety Spotlight Again,” Nitrogen (London, 228, 1 July-August 1997b).
10. Mudan, K., and K. Mitchell, “Report on the Potchefstroom, South Africa Ammonia Incident,” Four Elements, Inc., Columbus, OH, 15 pp. (Mar. 1996).
11. Mulder, J. S., and H. O. Van Der Zalm, “Een Gaval van Dodelijke Ammoniakvergiftiging (Fatal Case of Ammonia Poisoning, in Dutch),” Tijdschrift Voor Sociale Geneeskunde, Rotterdam, The Netherlands, 45, 458 (1967).
12. National Research Council Committee on Toxicology, Guidelines for Developing Community Emergency Exposure Levels for Hazardous Substances, National Academy Press, Washington, DC, 109 pp. (1993).
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13.
14.
lod
16.
Li?
18.
19.
ORNL, DRAFT Acute Exposure Guideline Levels (AEGls) for Ammonia, Oak Ridge National Laboratory, Oak Ridge, TN, 61 pp. June 2, 1997).
Pederson, F., and R. S. Selig, “Predicting the Consequences of Short-Term Exposure to High Concentrations of Gaseous Ammonia,” J. of Hazardous Materials, 21, 143 (1989).
RAM TRAC, Acute Inhalation Risks Potentially Posed By Anhydrous Ammonia, R. A. Michaels, Project Director, RAM TRAC Corp., Schenectady, NY, 99 pp. (May 31, 1996).
RAM TRAC, Comments of Robert A. Michaels, PhD, CEP to the National Advisory Committee on Acute Exposure Guideline Levels on AEGL Values for Ammonia, R. A. Michaels, Project Director, RAM TRAC Corp., Schenectady, NY, 28 pp. (Aug. 5, 1996).
RAM TRAC, Supplemental Comments By Robert A. Michaels to the National Advisory Committee on Acute Exposure Guideline Levels for Ammonia, R. A. Michaels, Project Director, RAM TRAC Corp., Schenectady, NY, 14 pp. (Aug. 26, 1996).
RAM TRAC, Residual Issues of Ammonia Emergency Planning: Comments By RObert A. Michaels to the National Advisory Committee on Acute Exposure National Advisory Committee on Acute Exposure Guideline Levels, R. A. Michaels, Project Director, RAM TRAC Corp., Schenectady, NY, 19 pp. (Nov. 15, 1996).
RAM TRAC, Compilation of Previous RAM TRAC Comments Still Requiring Response Regarding Draft Oak Ridge National Laboratory Ammonia Support Docu-
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20.
21.
22.
23.
24.
25.
ments Submitted to NAC AEGL, R. A. Michaels, Project Director, RAM TRAC Corp., Schenectady, NY, 7 pp. (June 9, 1997).
Ronzai, E., “Uber den Einfluss der Einatmungen von reizenden Gasen der Industrien auf die Schutzkrafte des Organismus geneniiber den infektiven Krankheiten,” Archiv fiir Hygiene, 70, 217 (1909). Silverman, L., J. L. Whittenberger, and J. Muller, “Physiological Response of Man to Ammonia in Low Concentrations, J. of Ind. Hygiene and Toxicology, 31, 74 (1949).
Smil, V., “Global Population and the Nitrogen Cycle,” Scientific American, 277(1), 76 (July 1997).
Ten Berge, W. F., A. Zwart, and L. M. Appelman, “Concentration-Time Mortality Response Relationship of Irritant and Systemically Acting Vapours and Gases,” J. of Hazardous Materials, 13, 301 (1986).
U. S. EPA, “Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry,” EPA/600/8-90/066F, Office of Research and Development, Washington, DC, p. i (Oct. 1994). Verberk, M. M., “Effects of Ammonia in Volunteers,” International Archives of Occupational and Environmental Health, 39, 73 (1997).
This paper (3g) was presented at the 32nd Annual Loss Prevention Symposium held during the AIChE Spring National Meeting in New Orleans, LA on March 10, 1998.
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Publication citation
Michaels, RA. Emergency planning: critical evaluation of proposed AEGLs for ammonia. Process Safety Progress, 17(2):134-7, 1998;