Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 1
Monitoring at Chemical Agent Disposal Facilities Executive Summary This report from the National Research Council’s (NRC’s) Committee on Monitoring at Chemical Agent Disposal Facilities was requested by the U.S. Army for purposes of advising its Chemical Materials Agency (CMA) about the status of analytical instrumentation technology and systems suitable for monitoring airborne chemical warfare agents at chemical weapons disposal and storage facilities. The CMA is currently operating six chemical weapons disposal facilities located at storage sites in the continental United States and has completed the disposal of weapons once stored overseas. Disposal facilities at two U.S. sites are still in the design stage. To date, just over a third of the chemical agent in the original stockpile has been destroyed. It is likely that disposal operations will not be completed until 2012 or later. The committee was charged to review both the current monitoring systems used for airborne agent detection at CMA facilities and to investigate the applicability and availability of innovative new technologies. It was also tasked with considering how the regulatory requirements for airborne agent monitoring, particularly the new chemical agent airborne exposure limits (AELs) recommended by the Centers for Disease Control and Prevention (CDC) in 2003 and 2004 and implemented by the CMA in 2005, would impact the effectiveness of the CMA’s current agent monitoring procedures, and whether any applicable new monitoring technologies that are available could be effectively incorporated into the CMA’s overall chemical agent monitoring strategies. A review of the CMA’s chemical weapons demilitarization challenge, an account of the committee’s activities, and the committee’s statement of task are presented in Chapter 1. CHEMICAL AGENT MONITORING CHALLENGE In order to protect its workforce as well as both the general public and the environment near its facilities, the CMA monitors airborne chemical agents at exceedingly low levels. Through the use of near-real-time (NRT) instruments, the ambient air inside much of each facility is monitored for concentrations of agents not to exceed (depending on the type of agent) 0.4 to 0.0008 parts per billion by volume (ppbv) every 15 minutes or less. The purpose of this monitoring is to warn workers if unexpected levels of agent have penetrated areas in which protective gear is normally not required. Exhaust emissions in the pollution abatement system and the exhaust stack are also monitored for agents by NRT instruments at the source emission limits (SELs), which are only modestly higher levels than those acceptable for the ambient air in the facility. In addition, using sample collection and analysis techniques, historical monitoring is performed within the facility, in accordance with the new AELs, at agent concentration levels that are 3 to 10 times lower (depending on the type of agent) than the levels for plant air NRT monitors in order to ensure that the workers are not exposed to very low but persistent levels of agent. These same sampling and laboratory analysis systems are used as confirmation monitors to determine if adjacent NRT monitor alarms are actually caused by a chemical agent or another pollutant. Finally, the sampling and analysis method is also used at CMA facility perimeters to monitor at extremely low agent levels that, based on the new CDC recommendations, range from 0.003 to 0.00005 ppbv (depending on the chemical agent). Such monitoring is intended to ensure that no significant level of agent migrates over the fence line of a CMA facility and affects the nearby public or environment. The need to detect very low chemical agent concentrations within air masses that may also contain much higher levels of other industrial and environmental contaminants that can interfere with chemical agent detection makes the CMA’s monitoring tasks very challenging. In order to assess this challenge, the committee reviewed the CMA’s chemical agent monitoring requirements, the chemical and physical properties of the stockpiled chemical agents, and the former (1988) and current (2003/2004) chemical agent AELs; its
OCR for page 2
Monitoring at Chemical Agent Disposal Facilities review is presented in Chapter 2. The committee does find that the CDC’s newly promulgated AEL, the short-term exposure limit (STEL), is an appropriate basis for NRT monitoring at CMA facilities, since it ensures worker protection. The committee recommends that the Army continue to use STELs as the basis for NRT monitoring. In order to develop the framework for evaluating the performance of the current CMA airborne agent monitoring systems and for evaluating potential novel agent monitoring technology, the committee reviewed the science of analytical trace gas detection and quantification and the components of trace gas monitoring systems. Its review is presented in Chapter 3. CURRENT AIRBORNE AGENT MONITORING SYSTEMS A detailed review of the CMA’s current agent monitoring instruments, systems, and practices that focuses on the challenges posed by the CDC’s new 2003/2004 AELs is presented in Chapter 4. The committee concurs with previous NRC reports that frequent NRT false-positive alarms have been a persistent problem (NRC, 1994, 1999, 2001, 2002).1 It reviewed some recent NRT monitoring data which indicated that the CMA has made progress in reducing, but has not eliminated this problem. The committee finds that the Army has indeed made progress in reducing NRT false positives, but notes that this type of false-positive alarm will likely continue to be a problem, particularly for the nerve agent VX. The committee also finds that an increased frequency of false positives may be experienced for historical monitoring sample-collection-and-laboratory-analysis systems as the CMA implementation of the lower 2003/2004 AEL levels for historical monitoring of the workplace and at the fence line continues. Despite some problems with false-positive measurements, the committee also finds that the current NRT monitoring and the monitoring technology for sampling and laboratory analysis appear to provide sufficient airborne agent monitoring capability to afford adequate protection to workers, the general public, and the environment. However, given that the disposal operations will be ongoing for some years, at least until 2012 and perhaps beyond, the committee recommends that the CMA should consider a wider range of incremental improvements to the Automatic Continuous Air Monitoring System (ACAMS), the Miniature Chemical Agent Manufacturing System (MINICAMS), and the Depot Area Air Monitoring System (DAAMS) to allow these monitoring systems to better monitor at the CDC’s 2003/2004 AELs. Some technologies that deserve consideration by the CMA are shown in Chapter 4. The committee also notes that the CMA has historically set the NRT alarm levels at some fraction of the relevant AEL or SEL, with the goal of ensuring a statistical alarm response rate of 95 percent or better when agent is present at the AEL or SEL. The committee finds that neither the CMA’s plans to possibly set alarm levels at 1.0 AEL/SEL nor the inclination of state regulators to specify alarm levels of 0.2 AEL may be optimal. The committee recommends that the Army should consider continuing to use alarm levels that ensure that all properly operated and maintained NRT monitors at a given site have at least a 95 percent probability of sounding an alarm any time the true agent concentration in an area being monitored exceeds 1.00 STEL. The committee’s analyses and recent operational experience indicate that this can often be achieved with an alarm level of ~0.5 AEL/SEL, and that such a setting will tend to reduce false-positive alarms without greatly enhancing the probability of false-negative measurements. ADVANCED CHEMICAL AGENT MONITORING TECHNOLOGY After reviewing the performance of the current airborne monitoring technology used in CMA facilities, in Chapter 5 the committee reviews newer trace gas monitoring technologies that might be applicable for airborne agent monitoring in CMA facilities. Here it focuses on technologies that might provide real-time (~1 s) agent detection capability without sacrificing too much sensitivity or specificity. The committee examined two vibrational spectroscopy technologies: Fourier transform infrared (FT-IR) spectroscopy, employed in either an open-path or a folded multipass gas cell configuration, and surface-enhanced Raman scattering (SERS). The committee finds that FT-IR spectroscopy will likely have limited utility because its limited sensitivity for the relevant chemical agents makes real-time detection at STEL or lower AELs problematic. FT-IR might be configured to detect concentrated agent plumes encountered near large emission sources that contain agent concentrations of 0.05 mg/m3 (~4 to 8 ppb) or higher. Likewise, SERS is not likely to allow real-time agent detection at STEL levels and does not promise significant advantages over current NRT monitors. The committee did, however, find that chemical ionization mass spectrometry (CIMS) is a highly sensitive trace gas detection technique, widely deployed in atmospheric chemistry research studies to measure a variety of trace gases, and that it is potentially capable of measuring the stockpiled chemical agents at concentrations well below STEL levels in real time. The committee recommends that the Army should investigate whether present CIMS instrumentation could be immediately used to detect chemical agents at the immediately dangerous to life and health (IDLH) limit in real time. The use of negative ions as a 1 False-positive alarms refer to situations in which an agent concentration above a specified level is indicated by an alarm but is not true; false-negative alarms refer to situations in which a specified level is exceeded but no alarm is sounded.
OCR for page 3
Monitoring at Chemical Agent Disposal Facilities precursor should be investigated to improve selectivity. Adaptation of one of the research-grade atmospheric field instruments for real-time detection between the STEL and the general population limit (GPL) for each relevant agent should be considered. The committee also examined the rapidly evolving field of chemical sensor arrays but concluded that, while they might soon be useful in detecting agents at the relatively high, IDLH limit, the development time required for these sensor arrays to work reliably at the STEL or lower AELs is probably too long to impact the CMA’s chemical weapons disposal program. The committee also finds that since the federal government is currently the only obvious customer for chemical agent detection at STEL or lower levels, the commercial development of sensors with this capability is unlikely without direct federal support. CHEMICAL AGENT MONITORING SUMMARY The committee also reviewed specific requirements for airborne agent monitoring and analyzed event scenarios in which releases of chemical agents in CMA’s weapons disposal or storage facilities might motivate the development and adoption of new airborne agent monitoring technologies to supplement the CMA’s existing agent monitoring systems. The results of this review and analyses are presented in Chapter 6. Consistent with previous NRC reports (NRC, 1999, 2001), the committee finds that the current airborne agent monitoring systems are adequate to safely protect the chemical demilitarization workforce, the public, and the environment, although potential incremental improvements that enhance sensitivity and specificity to reduce the rate of false-positive alarms and/or cycle times might improve plant efficiency and safety. The committee recommends that continued incremental improvements in the current airborne chemical agent monitoring systems at chemical stockpile storage and demilitarization sites, as discussed in Chapter 4 of this report, should be pursued by the Army. On the basis of its evaluations of the potential agent release scenarios coupled with information on the probable detection capabilities of the newer agent monitoring technologies, the committee finds that disposal facility unpack areas might sustain agent releases, possibly including agents other than the one that its NRT monitors are set up to detect for the current agent disposal campaign. The committee recommends that the Army should analyze whether the addition of real-time and/or multiagent monitoring in the unpack area of chemical demilitarization facilities that process multiple munitions would significantly reduce risk to workers who unpack and stage munitions for processing. If the risk analysis indicates a significant enhancement of worker safety, the Army should investigate whether other, shorter response time and/or multiagent deployment modes for current NRT monitors or the development and/or procurement of real-time, multiagent monitors based on innovative technology are feasible and practical. The committee also finds that, to pose an acute risk to the public, the atmospheric release of sufficient chemical agent vapor or aerosol would require a major accident, almost certainly involving explosion and/or fire. The ability to confirm dispersion model predictions that an agent plume has penetrated the depot boundary and threatens the public or to track the agent plume would require fast-response monitors operating at levels between the STEL and the IDLH that are either widely dispersed or are mounted on a suitable ground or air mobile platform. The committee recommends that the Army and other relevant stakeholders should assess whether public protection would be significantly enhanced by the development and deployment of dispersed fixed or portable fast-response agent sensors or the development of a mobile fast-response agent sensor platform capable of detecting and tracking a large release plume. The committee finds that open- or folded-path FT-IR and CIMS technology have some promise for providing enhanced, fast-response chemical agent monitoring capability to chemical weapons storage and demilitarization facilities. However, the committee recommends that the Army should only deploy advanced chemical agent monitoring equipment after a thorough risk/benefit analysis shows that the risk reduction to the workforce and/or public justifies the monetary and opportunity costs. If worker or public risk reduction analyses indicate significant benefit at acceptable cost from deployment of fast-response, multiagent monitoring capabilities, systems using FT-IR or, more likely, CIMS should be considered. An overview of the committee’s findings and recommendations is presented above. Detailed findings and recommendations associated with the data, references, and analyses that support them are presented in Chapters 2, 4, 5, and 6. All of the findings and recommendations are also grouped together in Chapter 7. REFERENCES NRC (National Research Council). 1994. Review of Monitoring Activities Within the Army Chemical Stockpile Disposal Program. Washington, D.C.: National Academy Press. NRC. 1999. Tooele Chemical Agent Disposal Facility: Update on National Research Council Recommendations. Washington, D.C.: National Academy Press. NRC. 2001. Occupational Health and Workplace Monitoring at Chemical Agent Disposal Facilities. Washington, D.C.: National Academy Press. NRC. 2002. Evaluation of Chemical Events at Army Chemical Agent Disposal Facilities. Washington, D.C.: The National Academies Press.
Representative terms from entire chapter: