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Iodotrifluoromethane: Toxicity Review 6 Human Exposure Two documents from the U.S. Army Center for Health Promotion and Preventive Medicine (USACHPPM) (McCain and Macko 1999; Chaney 2002) provide basic information on potential scenarios of U.S. Army exposure to iodotrifluoromethane (CF3I). However, few specific exposure data were available for or included in the two reviews. Two experimental studies, one assessing exposure to CF3I in handheld extinguishers (Skaggs and Cecil 1995, as cited in Chaney 2002) and one assessing exposure from intentional release of CF3I in Air Force F-15 aircraft engine nacelles (Vinegar et al. 1999), are discussed in detail. They also discuss anecdotal evidence from two people who inhaled CF3I during sales demonstrations (Vinegar et al. 1999). Lack of realistic exposure data on CF3I (or even a potential exposure surrogate, Halon 1301) and on potential decomposition products collected in situations and conditions of interest to the U.S. Army makes it difficult to evaluate the conclusions reached in the 2002 update (Chaney 2002). This chapter discusses specific issues related to exposure that should be considered in the Army’s review. CF3I AND ITS DECOMPOSITION PRODUCTS Since the United States signed the 1987 Montreal Protocol on Substances That Deplete the Ozone Layer, which restricted the use of halon fire suppressants and banned production of many of them after 1993, U.S. military and firefighting agencies have been seeking so-called drop-in replacements for the widely used Halons 1211 and 1301 (CF2BrI and CF3Br, respectively). Of special interest as a replacement for Halon 1301 has been CF3I, which is chemically similar to but replaces its bromine atom
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Iodotrifluoromethane: Toxicity Review with an iodine atom. CF3I has similar fire-suppression potential (Tapscott 1999; Chaney 2002) but much lower ozone-depletion potential—0.008-0.01 compared with 12 for Halon 1301 (Solomon et al. 1994; Connell et al. 1996; Bannister et al. 2003). The cited inerting1 concentration of CF3I is 6.5% (NFPA 2000). CF3I breaks down in the presence of sunlight and degrades rapidly at temperatures above 100°C, producing hazardous by-products that include hydrogen fluoride (HF), hydrogen iodide (HI), and carbonyl fluoride (COF2) (McCain and Macko 1999). Exposure to those decomposition products should be considered in the assessment of health effects of use of CF3I. Orion Safety Industries (2000) has discussed one of the decomposition products, HF, and suggests that concentrations of HF produced by degradation of CF3I are similar to those produced by degradation of Halon 1301. USES OF CF3I The 1999 Army review of CF3I concludes that it should not be used “in many Army systems without further evaluation” (McCain and Macko 1999). The 2002 update (Chaney 2002) concludes that CF3I can be used in normally unoccupied areas only and that “any employee that could possibly be in the area must be able to escape within 30 sec, and the employer must ensure that no unprotected employees enter the area during agent discharge.” Those conclusions are based on the U.S. Environmental Protection Agency (EPA) Significant New Alternatives Policy guidelines (60 Fed. Reg. 31092 ). A presentation on potential military uses of CF3I was given to the present National Research Council subcommittee by J. Vitali, of Georgia Tech Research Institute (Vitali 2003). The presentation also discussed approved uses in countries other than the United States. Suggested potential uses include many Army systems that now use Halon 1301, such as Fire suppression in helicopter engines. Ground vehicle engine compartments, for example, armored personnel carriers. Halon 1301 can be used in occupied and unoccupied spaces; however, 1 An inerting gas usually refers to a gaseous mixture containing little or no oxygen and mainly consisting of non-reactive gases or gases having a high threshold before they react. Nitrogen, argon, and carbon dioxide are common examples.
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Iodotrifluoromethane: Toxicity Review CF3I can be used only in normally unoccupied spaces. Weapon systems and facilities in which Halon 1301 fire suppression might be required include Unoccupied spaces, such as Air Force F-16 aircraft engines, auxiliary power units, dry bays, and fuel tanks. Occupied spaces, such as personnel compartments. Command and control facilities, generally considered to be occupied, including computer rooms, base operations, flight lines, hangars, depots, and testing facilities. Halon 1301 is now used in rotary aircraft engines (Apache, Kiowa, Comanche, Chinook, Black Hawk, and Cobra) and in ground vehicles and personnel compartments (armored personnel carriers, interim armored vehicles, medium tactical vehicles, and Abrams and Bradley tanks). In rotary-engine fire-suppression systems, CF3I would not be expected to enter the personnel compartment. For inerting of Air Force F-16 fuel tanks, occupant exposure would not be expected to occur. The primary potential exposure would be of service and maintenance personnel. CF3I has been approved for use in unoccupied areas in two other countries. In June 1996, the German Hygiene Institut des Ruhrgebiets recommended CF3I use in unoccupied areas of military vehicles and aerospace engine compartments. Australia has approved use of CF3I as a total flooding agent in unoccupied spaces, such as aircraft-engine compartments and auxiliary power units, and in unoccupied engine and power compartments on a variety of military and nonmilitary vehicles, including its Sea Sprite helicopters. Commercial-aircraft test systems and a railroad diesel power car have been installed with CF3I. Australia also has approved use of CF3I as an explosion suppressor in grain silos, gluten-formulation facilities, and starch-processing plants. CF3I may be used as a streaming agent in portable and wheeled fire-fighting units for high-risk fires, such as in aircraft engines and refueling fires (Vitali 2003). So far, with limited CF3I use, no accidental discharges have occurred, according to Australian officials (O.E. Aberle, Australian Government Department of Defense, personal commun., December 4, 2003). Thus, many uses of Halon 1301 represent potential uses of CF3I. The Army review update (Chaney 2002) recommends use in normally unoccupied areas only. Most likely uses of CF3I are as a fire suppressor or a streaming agent for handheld fire extinguishers, a flooding agent for tanks and military aircraft (for example, in F-15 aircraft-engine nacelles) and for electronic equipment, and an inerting agent in Air Force F-16 aircraft-engine wing fuel tanks (McCain and Macko 1999; Rupnik et al. 2002).
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Iodotrifluoromethane: Toxicity Review No commercial uses of CF3I, other than fire suppression have been identified in the published literature. However, there may be fire-suppression uses that are not covered in the Army update (Chaney 2002). To assess exposure fully, the subcommittee recommends that the Army review all potential use scenarios, not just those in normally unoccupied areas. USACHPPM should more clearly define specific situations in which CF3I is likely to be used. Refining such exposure scenarios would allow more accurate assessment of potential exposure, particularly during maintenance and accidental releases. Measured levels of CF3I can be dangerously high (up to 70,000 ppm) in cases of accidental discharge when it is used as a flooding agent for fires in Air Force F-15 engine nacelles (Vinegar et al. 1999). The subcommittee recommends that personnel potentially exposed in similar situations be properly trained and use appropriate personal protective equipment. Furthermore, the subcommittee recommends that release technologies be studied so that the potential for accidental release in normally unoccupied spaces, such as aircraft engine nacelles, can be minimized. RECOMMENDED STANDARDS FOR CF3I AND ITS DECOMPOSITION PRODUCTS The Army update (Chaney 2002) discusses and reviews exposure standards for CF3I but does not discuss exposure standards for potential decomposition products. For completeness, exposure standards for CF3I and its decomposition products are discussed below. The subcommittee recommends that additional information on types of exposure (such as, acute, chronic, intermittent) and exposure concentrations for CF3I and its decomposition products in various Army uses be collected and evaluated. Without such information, assessment of the safety of CF3I as a Halon 1301 replacement in Army applications cannot be complete. When specific exposure data for CF3I or its decomposition products are lacking, the subcommittee finds that it may be possible to use, with adjustments for physical and chemical properties, exposure data on Halon 1301. Iodotrifluoromethane In 1994, EPA approved CF3I as a substitute for Halon 1301 but only for normally unoccupied areas, owing primarily to concerns about cardiac sensitization. Specifically, approved systems using CF3I were required to be designed up to the no-observed-adverse-effect level (NOAEL) (0.2%
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Iodotrifluoromethane: Toxicity Review vol/vol) where egress could not be accomplished within 1 min, up to the lowest-observed-adverse-effect level (LOAEL) (0.4% vol/vol) where egress could occur within 30 sec to 1 min, and above the LOAEL where egress could occur in less than 30 sec (EPA 1994). In 1997, EPA approved CF3I as a replacement for Halon 1211 in nonresidential applications only. However, both those restrictions on the use of CF3I were withdrawn by EPA in April 2002 because they were considered redundant with respect to the National Fire Protection Association (NFPA) 2001 Standard on Clean Agent Fire Extinguishing Systems (NFPA 2000). The standard allows CF3I to be used for systems in normally occupied areas up to the NOAEL (0.2% vol/vol) for any period, although unnecessary exposures to CF3I and decomposition products “shall be avoided.” For both normally occupied and unoccupied areas, exposures may exceed either the NOAEL (0.2% vol/vol) or the LOAEL (0.4% vol/vol) or both, according to durations based on physiologically based pharmacokinetic (PBPK) model studies (Vinegar et al. 2000). Specifically, up to 5 min of exposure is allowed for CF3I concentrations of 0.2-0.3% vol/vol—that is, above the NOAEL—and decreasing times are allowed as concentrations increase above this level and may even exceed the LOAEL if escape can occur within 30 sec (see Table 6-1). The NFPA standards are designed for the protection of firefighting personnel in emergency-response and cleanup operations. Hydrogen Fluoride The American Conference of Government Industrial Hygienists (ACGIH) has set a ceiling limit for exposure to HF of 3 ppm, and the Occupational Safety and Health Administration (OSHA) permissible exposure limit is 3 ppm for an 8-h exposure time-weighted average (TWA) (Table Z-2) (29 CFR § 1910.1000). However, NFPA considers those standards “not relevant” for fire-extinguishing use, although they “may need to be considered” for cleanup operations (NFPA 2000). NFPA considers the recommendations of the American Industrial Hygiene Association Emergency Response Planning Guidelines to be more appropriate for firefighting situations: for 1-h exposures, mitigating steps such as respiratory protection should be taken above 20 ppm, and 50 ppm is the maximal nonlethal exposure for nearly everyone, except those who are “susceptible persons” (NFPA 2000); for 10-min exposures, the corresponding recommendations are 50 and 170 ppm, respectively. The NFPA document also notes that at about 100 ppm, escape-impairing effects may develop, and at
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Iodotrifluoromethane: Toxicity Review TABLE 6-1 Time for Safe Human Exposure at Stated Concentrations of CF3I Concentration (% vol/vol) Concentration (ppm) Exposure Time (min) 0.2a 2,000 5.00 0.25 2,500 5.00 0.30 3,000 5.00 0.35 3,500 4.30 0.40b 4,000 0.85 0.45 4,500 0.49 0.5 5,000 0.35 aNOAEL. bLOAEL. Source: NFPA 2004. Reprinted with permission, copyright 2004, National Fire Protection Association, Quincy, MA. This material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety. 100-200 ppm, humans convert from nose breathing to mouth breathing, greatly increasing the possibilities of lower respiratory system damage and death (Dalby 1996). EPA has developed a 10-min acute exposure guideline level (AEGL-2) for HF of 95 ppm (NRC 2004). Hydrogen Iodide HI is colorless and, because of its great affinity for water, highly corrosive to skin, eyes, and mucous membranes. It has a relatively low OSHA ceiling limit of 0.1 ppm as iodine (29 CFR § 1910.1000). There is also an ACGIH emergency short-term exposure limit (STEL) of 0.1 ppm as a ceiling value for iodine, but none specifically for HI. Carbonyl Fluoride COF2 is highly toxic and unstable, and it does not have an OSHA standard. The ACGIH standards are 2 ppm for the TLV and 5 ppm for the STEL (ACGIH 2003).
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Iodotrifluoromethane: Toxicity Review EXPOSURE TO CF3I AND ITS DECOMPOSITION PRODUCTS Three potential exposure scenarios have been identified by the subcommittee: Exposures to CF3I during manufacture, transfer and filling of tanks, and tank leakage in transfer and storage. Exposures to CF3I and its decomposition products due to streaming with handheld fire extinguishers (2.5-13 lb fire extinguishers) or due to accidental discharge from firefighting equipment during training, maintenance, repair, or overhaul (Skaggs 1995, as cited in Chaney 2002). Exposures to CF3I and its decomposition products due to accidental discharge of high-volume firefighting systems, such as those in airplane engine nacelles or tanks or of CF3I storage cylinders, could result in exposures to greater than 70,000 ppm at head level (Vinegar et al. 1999). Anecdotally, several instances of salespersons intentionally breathing in CF3I gas have been reported (Vinegar et al. 1999). The third scenario is of greatest concern because it could result in exposures exceeding the NOAEL and LOAEL and be life threatening. Exposures resulting from the first two scenarios are also of concern but are less likely to be immediately dangerous to life and health. Human-Exposure Reports The Army reviews (McCain and Macko 1999; Chaney 2002) contain several reports related to human exposure to CF3I or its decomposition products. They are reviewed below with comments by the subcommittee on other data sources and data gaps. Iodotrifluoromethane There do not appear to be any human-exposure or health-effects studies in the published scientific literature related to low-level exposures, either chronic or acute, to CF3I. Several studies to examine the extent and effects of CF3I exposures have been undertaken to assess its potential as a drop-in replacement for
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Iodotrifluoromethane: Toxicity Review Halon 1301 or 1211. Most of the studies have been sponsored by the Department of Defense or EPA. One series of studies was undertaken in the early 1990s to determine exposures of firefighters during simulated streaming operations with handheld fire extinguishers (Skaggs 1995, as cited in Chaney 2002). Three room sizes were studied—from 900 to 5,100 cubic feet (ft3)—and discharges varied from 2.5 to 13 lb of CF3I. The 1-ft target was placed on or at various heights above the floor. In all cases, the firefighter stood 8 ft from the target. The peak concentrations of CF3I varied from 1.0% to 3.0% and were all above the NOAEL (0.2%) and LOAEL (0.4%). More important, the average concentrations over the first 30 min varied from 1,040 ppm (0.1%), which is below the NOAEL, to 4,678 ppm (0.5%), which is above the LOAEL. Both the NOAEL and the LOAEL are related to cardiac sensitization, so most of those exposure scenarios represent situations immediately dangerous to life and health and would require self-contained breathing apparatus respiratory protection for the firefighters at all times. To assess the potentially very high exposure of personnel who might be affected by accidental discharges of CF3I from an aircraft engine nacelle during ground maintenance and repair operations, a series of CF3I discharges were carried out on a grounded F-15 jet. The CF3I exposures were measured with three test instruments whose sensitivities covered a broad range of possible CF3I exposure. Sensors were at various potential ground-personnel work locations. The lowest peak CF3I concentration (0.9%) occurred at head level behind the left wing with the nacelle doors open, the highest (7.0%) at head level under the nacelle. In two of the six instances illustrated, the concentrations peaked and returned to low levels within 5-10 sec, but in the other four, the concentrations remained above the NOAEL and LOAEL for 30-275 sec. The average concentrations of CF3I were not quoted (Vinegar et al. 1999). However, the authors attempted to assess the arterial blood concentrations of CF3I with a PBPK model to estimate the exposure that affected the heart on the basis of the observed CF3I measurements. The concentrations were compared with the estimated blood concentrations 5 min after steady-state ambient exposure at the LOAEL. Some of the strengths and limitations of that approach were discussed in Chapter 5. According to this relatively sophisticated model, the estimated blood concentration due to ambient air exposure near the head under the open nacelle was about twice the LOAEL-based concentration for cardiac sensitization. None of the other scenarios exceeded the LOAEL-based concentration of 19 mg/L, but the estimated blood concentrations in three of the six scenarios were about
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Iodotrifluoromethane: Toxicity Review 16 mg/L—relatively close to the danger value for a model in which a number of key parameter values had to be extrapolated from values in rats (Vinegar et al. 1999, 2000). Reports have circulated for many years about two CF3I salesmen who are alleged to have inhaled CF3I from a balloon 15-17 times, as part of their sales presentations, without reported ill effects. Vinegar et al. (1999) estimated that the average volume inhaled was 1.25 L of CF3I during each presentation, resulting in a PBPK-based estimate of a peak blood concentration of about 2,000 mg/L, more than 100 times the LOAEL-based level of 19 mg/L. However, no clinical measurements were made of the two men after their demonstrations, so their survival attests to the absence of fatal arrhythmias, not necessarily to nonfatal sensitization incidents—the two men were 35 and 38 years old, ages at which many people are in peak health. Rupnik et al. (2002) has criticized the estimates for ignoring the possibility of tolerance after repeated trials. Those issues suggest that reliance on the data are of little use in setting exposure limits. A fundamental difficulty in using CF3I as a Halon 1301 replacement is that its inerting concentration to extinguish fires is 6.5%, whereas its LOAEL is 0.4%. Thus, its inerting concentration is 16 times as great as its LOAEL, and its use as a flooding agent for fire suppression is inappropriate except for unoccupied areas and poses potentially grave risks to firefighters should the concentration of CF3I be greater than the LOAEL, should exposure exceed 30 sec, or should personal protective equipment not be worn. The subcommittee recommends that uses of CF3I that may involve acute exposures should be restricted to normally unoccupied areas. Hydrogen Fluoride, Hydrogen Iodide, and Carbonyl Fluoride None of the exposure studies examined contained any reports of experimental measurements of any of these three chemicals, nor were the estimates of the possible exposure to them expected from various CF3I discharges. Although it is understandable that studies related to cardiac sensitization, which can be fatal, have attracted the greatest initial research interest, HF, for example, is highly toxic and can lead to death, as NFPA 2001 Standard notes (NFPA 2000). Before the safety of CF3I as a Halon 1301 replacement can be properly assessed, the subcommittee suggests that studies of possible exposure to its potential degradation products—HF, HI, and COF2—be carried out or that reliable estimates of exposures to these chemicals be made to ensure that their presence is not of health consequence.
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Iodotrifluoromethane: Toxicity Review Human-Exposure Limits The NOAEL and LOAEL of CF3I as determined with the dog cardiac-sensitization model are 0.2% and 0.4%, respectively. On the basis of the PBPK model, people could be safely exposed at 0.4% for about 51 sec before the critical CF3I blood concentration for cardiac sensitization is reached. Furthermore, people could be exposed at up to 0.3% for more than 5 min without reaching the critical blood concentration. In addition, the subcommittee recommends that personnel potentially subjected to short-term high exposures (maintenance and service personnel) be trained and use personal protective equipment deemed appropriate by industrial hygienists and described in NFPA 2001 Standard (NFPA 2000). An exposure limit of 2,000 ppm may not be appropriate for other scenarios, however, including those that may involve chronic, low-level exposure or repeated exposure at moderate or high concentrations. For uses and exposures other than those specific to the Army (McCain and Macko 1999; Chaney 2002), the subcommittee recommends that separate exposure assessments be made. It also suggests that the Army monitor for international exposure and toxicity data. Exposure data from Australia and Germany may be available in the future, as CF3I is approved for some uses in those countries.
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