7
Findings and Recommendations

The findings and recommendations developed and presented in the previous chapters of this report are gathered below for easy review.

GENERAL AIRBORNE CHEMICAL AGENT MONITORING CHALLENGES

Finding 2-1. The Army’s use of CDC’s newly promulgated short-term exposure limits (STELs) as a basis for monitoring at demilitarization facilities is appropriate to ensure that workers are protected.

Recommendation 2-1. The committee recommends that the Army continue to use short-term exposure limits (STELs) as the basis for near-real-time monitoring.

AIRBORNE CHEMICAL AGENT MONITORING WITH CURRENT TECHNOLOGY

Finding 4-1. The Army has taken significant steps to reduce the level of false alarms (false positives) for ACAMS and MINICAMS monitors at stockpile disposal sites, especially through the elimination of potential chemical interferences and by the adjustment of alarm levels (while still maintaining a statistical response rate of 95 percent or better for the detection of agent excursions above 1.00 STEL). False-positive alarms are still a problem, however, especially when monitoring at VX STEL levels using NRT monitors. Also, false positives are expected to be a significant problem when using DAAMS monitors equipped with FPDs to monitor at the 2003/2004 WPLs and GPLs.

Finding 4-2. In accordance with the determinations of previous NRC studies (NRC, 1999, 20011), the committee finds that the reliability of ACAMS, MINICAMS, and DAAMS appears to provide sufficient airborne agent monitoring capability to afford adequate protection to workers, the general public, and the environment.

Finding 4-3. Air monitoring instrumentation used at stockpile disposal sites has been capable of reliable detection of the 1988 TWA levels for agents, as earlier NRC committees have indicated. These NRT instruments (ACAMS and MINICAMS) are likewise capable of detection at the 2003/ 2004 STEL and 2003/2004 IDLH levels.

Finding 4-4. DAAMS has proven effective in monitoring at the CDC’s 1988 TWA and GPL levels at stockpile disposal sites for more than 15 years. Because the 2003/2004 STELs have the same numerical concentration values as the 1988 TWA levels, historical and confirmation monitoring of GB, VX, and HD at the new STELs using DAAMS will be no more difficult than monitoring these agents at the 1988 TWA levels. Also, monitoring at the 2003 WPL for GB using DAAMS will be straightforward, with no significant increase in the occurrence of false positives (compared with DAAMS monitoring for GB at the 1988 TWA level). However, although DAAMS either has or is likely to have adequate sensitivity for monitoring at 2003/2004 AELs, the frequency of false positives is expected to increase in the following cases:

  • The 2003 VX WPL, which is less than the 1988 GPL for this agent;

  • The 2004 HD WPL, which is less than the 1988 GPL;

  • The 2003 GB GPL level, which is one-third of the 1988 GPL level;

  • The 2003 GPL for VX, which is one-fifth of the 1988 GPL value; and

  • The 2004 GPL for HD, which is one-fifth of the 1988 HD GPL value.2

1  

For references, see p. 37.

2  

As a consequence of the quadratic response of the FPD, the detector signal for the 2004 HD GPL will be 25 times less than the detector signal



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Monitoring at Chemical Agent Disposal Facilities 7 Findings and Recommendations The findings and recommendations developed and presented in the previous chapters of this report are gathered below for easy review. GENERAL AIRBORNE CHEMICAL AGENT MONITORING CHALLENGES Finding 2-1. The Army’s use of CDC’s newly promulgated short-term exposure limits (STELs) as a basis for monitoring at demilitarization facilities is appropriate to ensure that workers are protected. Recommendation 2-1. The committee recommends that the Army continue to use short-term exposure limits (STELs) as the basis for near-real-time monitoring. AIRBORNE CHEMICAL AGENT MONITORING WITH CURRENT TECHNOLOGY Finding 4-1. The Army has taken significant steps to reduce the level of false alarms (false positives) for ACAMS and MINICAMS monitors at stockpile disposal sites, especially through the elimination of potential chemical interferences and by the adjustment of alarm levels (while still maintaining a statistical response rate of 95 percent or better for the detection of agent excursions above 1.00 STEL). False-positive alarms are still a problem, however, especially when monitoring at VX STEL levels using NRT monitors. Also, false positives are expected to be a significant problem when using DAAMS monitors equipped with FPDs to monitor at the 2003/2004 WPLs and GPLs. Finding 4-2. In accordance with the determinations of previous NRC studies (NRC, 1999, 20011), the committee finds that the reliability of ACAMS, MINICAMS, and DAAMS appears to provide sufficient airborne agent monitoring capability to afford adequate protection to workers, the general public, and the environment. Finding 4-3. Air monitoring instrumentation used at stockpile disposal sites has been capable of reliable detection of the 1988 TWA levels for agents, as earlier NRC committees have indicated. These NRT instruments (ACAMS and MINICAMS) are likewise capable of detection at the 2003/ 2004 STEL and 2003/2004 IDLH levels. Finding 4-4. DAAMS has proven effective in monitoring at the CDC’s 1988 TWA and GPL levels at stockpile disposal sites for more than 15 years. Because the 2003/2004 STELs have the same numerical concentration values as the 1988 TWA levels, historical and confirmation monitoring of GB, VX, and HD at the new STELs using DAAMS will be no more difficult than monitoring these agents at the 1988 TWA levels. Also, monitoring at the 2003 WPL for GB using DAAMS will be straightforward, with no significant increase in the occurrence of false positives (compared with DAAMS monitoring for GB at the 1988 TWA level). However, although DAAMS either has or is likely to have adequate sensitivity for monitoring at 2003/2004 AELs, the frequency of false positives is expected to increase in the following cases: The 2003 VX WPL, which is less than the 1988 GPL for this agent; The 2004 HD WPL, which is less than the 1988 GPL; The 2003 GB GPL level, which is one-third of the 1988 GPL level; The 2003 GPL for VX, which is one-fifth of the 1988 GPL value; and The 2004 GPL for HD, which is one-fifth of the 1988 HD GPL value.2 1   For references, see p. 37. 2   As a consequence of the quadratic response of the FPD, the detector signal for the 2004 HD GPL will be 25 times less than the detector signal

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Monitoring at Chemical Agent Disposal Facilities Finding 4-5. The efforts of the Chemical Materials Agency (CMA) have resulted in the demonstration of significant incremental improvements in MINICAMS and DAAMS. It is clear, however, that even with the improvements demonstrated by the CMA, it will probably be difficult to monitor agents, especially VX and HD at the 2003/2004 GPL levels, without a significant increase in false positives (compared with monitoring at the 1988 GPL levels). Also, despite the success demonstrated to date, false positives may be a significant problem when monitoring at the 2003/2004 WPLs. Finally, false positives for ACAMS and MINICAMS monitors, especially when monitoring at the STEL for VX, are expected to continue. Recommendation 4-5. The Chemical Materials Agency (CMA) should consider a wider range of incremental improvements to ACAMS, MINICAMS, and DAAMS to allow these monitoring systems to better monitor at the CDC’s 2003/2004 AELs. Some technologies that deserve consideration by the CMA include the following: Adding a convex lens to the FPD to improve the signal-to-noise ratio of this detector in ACAMS, MINICAMS, and DAAMS; The use of cryotraps for all DAAMS monitors to sharpen GC peaks and thereby improve selectivity and sensitivity; The equipping of DAAMS systems with a PFPD in place of the FPD to enhance the selectivity and sensitivity of the DAAMS when monitoring for GB, VX, and HD; The equipping of DAAMS monitors with an XSD to enhance the selectivity and sensitivity of this system when monitoring for HD; The use of a sulfur chemiluminescence detector (SCD) for the detection of HD; and Funding the development of a phosphorus-specific FPD based on the magnetic quenching of HPO*3 emissions, a detector that is expected to be much more selective for organophosphorus compounds than is the conventional FDP or the PFPD. Finding 4-6. The Army’s plan to allow alarm levels for NRT monitors to be set at 1.00 AEL, especially for the CDC’s 2003/2004 STEL and IDLH values, has the potential to be perceived by workers and the general public as a significant reduction in safety for workers; will result in widely varying alarm rates from instrument to instrument and from week to week; will increase the probability that a worker may be exposed to unacceptable levels of HD, a classified carcinogen; and will increase the likelihood that the Army will not respond properly or in a timely manner to the presence of agents at true concentrations above the AELs. The only perceived benefit to raising the alarm level to 1.00 AEL is a possible reduction in the rates of false alarms, but this benefit is gained at the expense of a higher probability of false negatives. Recommendation 4-6. 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. Finding 4-7. At some sites, state regulators may insist that alarm levels be set at 0.2 STEL, the lower limit of certification for NRT monitors, even though it is likely that a statistical response rate of 95 percent or better can be achieved with the alarm level set at 0.5 STEL. Although an alarm level of 0.2 STEL typically ensures at least a 99 percent probability of detecting a true agent excursion above 1.00 STEL, alarm levels this low contribute significantly to the frequency of false alarms observed at stockpile disposal sites and contribute to a reduction in worker safety caused by the human tendency to discount an alarm if false alarms are experienced frequently. AIRBORNE CHEMICAL AGENT MONITORING WITH ADVANCED TECHNOLOGY Finding 5-1. In general, the use of FT-IR spectrometry with either open-path or multipass gas cell sampling for monitoring chemical warfare agents (CWAs) at levels below about 0.05 mg m−3 in the atmosphere near the perimeter of chemical agent storage facilities or demilitarization plants is not likely to be effective because of the low sensitivity of this technique. Conversely, FT-IR spectrometry may play an important role in monitoring accidental releases of chemical agents in locations very close to where the agents are stored or incinerated and where the concentration may exceed 0.05 mg m−3. Detecting a catastrophic release within a minute of the event would allow suitable action to be taken. Finding 5-2. Although SERS is the most promising infrared technique of any reviewed by the committee, it is unlikely to be any more sensitive or faster than ACAMS and probably would be less selective and more subject to interference from other airborne molecules. Finding 5-3. Chemical ionization mass spectrometry (CIMS) is a highly sensitive technique that may be able to detect all chemical agents in real time, potentially even at the general population limit. Previous work has focused exclusively on positive ion precursors. Instruments in the atmospheric community extensively use negative ions as a precursor, leading to increased selectivity without sacrificing sensitivity. Commercial CIMS instrument are already available, although with reduced sensitivity.     obtained for the 1988 HD GPL (for the same sample flow rate and sample period). For this reason, it may prove very difficult to monitor for HD at the 2004 GPL. 3   The asterisk symbol as used here indicates an excited electronic state.

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Monitoring at Chemical Agent Disposal Facilities Recommendation 5-3. The Army should investigate whether present CIMS instrumentation could be immediately used to detect chemical agents at the IDHL limit in real time. The use of negative ions as a 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 GPL for each relevant agent should be considered. Finding 5-4. During the time remaining for the CMA program, new chemical sensor technology is not likely to be useful for demilitarization plant monitoring at the STEL regulatory levels or below. The lead times for developing engineering prototypes and validating the technology with real chemical agents are long and are inconsistent with the program needs. Finding 5-5. Chemical sensors have the potential to be useful for making rapid measurements at IDLH levels and above, such as for events including spills and leaks. Finding 5-6. For any of the chemical sensors described, the federal government will be the customer, as there are no significant commercial markets for chemical agent detection. In order to take advantage of these technologies in the requisite time frame, accelerated support mechanisms must be put into place to transition them from research to commercial utility. Chemical sensors developed for active military or homeland defense purposes might be adopted by the CMA for real-time detection of high agent levels if these sensors become available before the demilitarization program ends. SUMMARY OF AIRBORNE CHEMICAL AGENT MONITORING FINDINGS AND RECOMMENDATIONS Finding 6-1. 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. Recommendation 6-1. 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. Finding 6-2. The unpack area is an area in chemical demilitarization facilities that process multiple munitions in which enhanced monitoring that features faster alarm response and/ or multiagent capability might significantly enhance worker safety. An analysis of historic STEL alarms in such areas may indicate that worker protection could be enhanced by a more rapid alarm at a higher level, above the STEL but at or below the IDLH level or AEGL-1, that would allow faster masking of workers in the event of a large leak. Recommendation 6-2. 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. Finding 6-3. 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. Recommendation 6-3. 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. Finding 6-4. 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. The most likely effective use for FT-IR spectroscopy is to provide fast-response, multiagent monitoring for a relatively restricted space such as a demilitarization facility’s unpack area. CIMS instruments are likely to be far more sensitive chemical agent detectors than are FT-IR instruments. Potential CIMS applications include monitoring a restricted space, such as a demilitarization facility’s unpack area, through multiple sampling lines, and detecting and tracking a large-release plume mounted onboard a mobile van or small aircraft. Recommendation 6-4. 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. Recommendation 6-5. 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.