Impact of Revised Airborne Exposure Limits on Non-Stockpile Chemical Materiel Program Activities (2005)

The U.S. Army asked the National Research Council (NRC) to form a committee to advise the Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) on proposed plans for implementing newly recommended limits on airborne concentrations of chemical agents.¹ The limits, called airborne exposure limits (AELs), are designed to protect demilitarization workers, the general public, and emergency responders from the toxic effects of airborne exposure to chemical agents. The Centers for Disease Control and Prevention (CDC) issued AELs in 1988 and revised them in October 2003 (for the nerve agents tabun (GA), sarin (GB), and VX) and May 2004 (for the blister agent mustard (H and HD)). The new limits were to be implemented on January 1, 2005, and July 1, 2005, respectively.²

The Army’s non-stockpile program is responsible for dismantling former chemical agent production facilities and destroying recovered chemical materiel.³ Assistance from the NRC was requested on means for implementing the 2003/2004 AELs in connection with two specific tasks: (1) the destruction of a former VX production facility at the Newport Chemical Depot (NECD) in Indiana and (2) the operation of two mobile systems, the explosive destruction system (EDS) and the rapid response system (RRS). The EDS and RRS constitute the non-stockpile program’s primary mobile systems for destroying recovered chemical weapons and materiel that were previously buried at military installations and other sites.

The CDC recommended new values for four types of AELs:

• The short-term exposure limit (STEL), for worker exposures of no more than 15 minutes.

• The worker population limit (WPL), for unprotected workers.

• The general population limit (GPL), for the unprotected general population.

• The immediately dangerous to life or health (IDLH) level.

In addition to specifying the length of time workers may operate safely at low levels of exposure, the AELs affect decisions about the personal protective equipment (PPE) workers should wear to avoid exposure and the monitoring equipment necessary to track ambient air concentrations. Table ES-1 further describes these four types of AELs.

In accordance with the statement of task (see Preface), the committee reviewed facility designs and operational procedures for (1) dismantlement of the former production facility at NECD and (2) the use of the mobile EDS and RRS platforms. Committee members visited NECD to meet with Army and contractor staff tasked with destroying the former VX production facility; other committee members traveled to Dugway Proving Ground (DPG), Utah, to observe monitoring operations during use of the EDS to destroy 4.2-inch mortar rounds. To understand CDC’s basis for establishing

the new AELs for nerve and mustard agents, the committee was briefed by CDC staff, who also provided written responses to questions posed by the committee. The committee was also briefed by the Army and contractor experts and received written responses from them to its questions as well. Numerous documents pertaining to the CDC AELs and the Army’s systems, technologies, processes, and procedures for ensuring worker and public safety were also reviewed.

The committee developed recommendations on analytical methods with improved selectivity and sensitivity; on various aspects of near-real-time (NRT) airborne contaminant monitoring; on operational procedures and airborne contaminant monitoring for NECD and the EDS; on the applicability of the Resource Conservation and Recovery Act (RCRA) to the non-stockpile program; and on involving workers and the public in the implementation of the new AELs. This executive summary discusses the committee’s primary recommendations only; additional recommendations are included in Chapters 2 through 6.

The 2003/2004 AELs were developed using generally accepted methods of setting regulatory limits. Although there are no new data on toxicity beyond those used to establish the 1988 values, the existing data were reevaluated using modified, more conservative methods that reflect present-day practices for establishing uncertainty factors (Federal Register, 2003a, 2004). Because the charge to the committee was narrowly defined, the committee accepted the new CDC-derived AELs as the starting point for its evaluation of the monitoring program. That is, the committee did not evaluate the process used or the end points selected by the CDC in revising the 1988 limits, nor did it take a position on the appropriateness of the 2003/2004 CDC-recommended AELs. Nevertheless, the committee does express, in Chapter 3, its opinion that the new AELs will not produce a demonstrable risk benefit. This report contains a substantive discussion of the 2003/2004 AELs and the distinctions between them and the 1988 limits, because it was necessary to understand the degree of uncertainty in the new limits in order to understand the role of monitoring in implementing them. Table ES-2 presents the 1988 AELs and the revised (2003/2004) AELs.

The 2003 WPLs and GPLs for GB were lowered from the 1988 values by a factor of 3 (an “uncertainty factor”) to account for individual variability within the worker and general population (Federal Register, 2003a). Since the WPLs for GA and VX are derived from the WPL for GB, the 2003 WPLs for GA and VX were also automatically reduced by a factor of 3. The WPL for VX, however, was further reduced by an additional factor of 3 (a “modifying factor”) to account for a sparse database, resulting in a 10-fold total decrease in the WPL from 1988. The CDC adjusted the GPL for VX, 3 × 10⁻⁸ mg/m³, upward by a factor of 20, to 6 × 10⁻⁷, so as to obtain a value that was protective for humans and that could be reliably monitored by available monitoring methods (Federal Register, 2002). The CDC justified this

increase in the allowable concentration by noting there was an expectation that any exposure would be identified and corrected within 3 days (72-hour TWA).

STELs and IDLH limits were derived in 2003 for GA, GB, and VX. A STEL of 1 × 10⁻⁴ mg/m³ was determined for GA and GB, while a STEL of 1 × 10⁻⁵ mg/m³ was determined for VX (Table 3-1). STELs are defined as exposures that would be acceptable for 15 minutes for unprotected workers. For GA and GB, such exposures should occur not more than four times a day, and at least 60 minutes should elapse between successive exposures. For VX, STEL exposures should occur not more than once a day (Federal Register, 2003a).

In 2004 the CDC recommended a WPL for HD of 4 × 10⁻⁴ mg/m³. This AEL was based on both short-term human data and long-term animal data, the same data used to establish the 1988 AELs. The critical human study incorporated an exposure concentration of 0.06 mg/m³ for 8 hours per day for 3 consecutive days adjusted to a 5-day occupational work week using a factor of 3/5, resulting in a lowest observed adverse effect level (LOAEL)⁴ of 0.036 mg/m³.

In 2004, the CDC also recommended a new 12-hour GPL of 2 × 10⁻⁵ mg/m³. This AEL was established using a single 10-hour human exposure of 0.1 mg/m³ and adjusting the 10-hour exposure to 24 hours and the 1-day exposure to 7 days, resulting in a LOAEL of 6 × 10⁻³ mg/m³. The exposure data were those that had been used to establish the 1988 AELs.

The CDC recommended a 2004 STEL of 3 × 10⁻³ mg/m³ for no more than one exposure to mustard in a day.

The CDC also recommended a 2004 IDLH limit of 0.7 mg/m³, not to exceed 30 minutes of exposure. The IDLH limit was derived by CDC’s National Institute for Occupational Safety and Health (NIOSH) in accordance with structured NIOSH protocols (Federal Register, 2004).

Sulfur mustard is listed as a Part A carcinogen in the National Toxicology Program’s Eleventh Report on Carcinogens (DHHS, 2004) and as a Group 1 carcinogen by the World Health Organization’s International Agency for Research on Cancer (IARC, 1987). The CDC GPL for sulfur mustard is a 12-hour TWA that reflects typical sampling times used in the stockpile program. The CDC considers that the 2004 GPL, 2 × 10⁻⁵ mg/m³, keeps carcinogens below thresholds of significant risk (see Chapter 3) (Federal Register, 2003b). Nevertheless, because of the uncertainties in characterizing the cancer potency of sulfur mustard, the CDC has recommended the 2004 AELs as interim values pending better understanding of the cancer potency of this agent.

The CDC states that the lower 2003/2004 recommended AELs do not reflect a change in or a refined understanding

of the demonstrated human toxicity of these agents and that no overt adverse health effects have been associated with the exposure limits recommended in 1988. The 2003/2004 values are based not on new or additional scientific data on the toxicity of these nerve agents in humans or animals but on updated and minimally modified risk assessment assumptions (Federal Register, 2003a). Thus, the lower 2003/2004 AELs add a layer of safety (conservatism) to the 1988 recommended AELs that have so far been protective for humans.

CDC’s objective in developing new AELs was to protect the health of workers and others who might be exposed to these chemical agents. In response to the new, lower AELs, sufficiently capable monitors must be used. Monitoring at the new AELs at non-stockpile sites is made difficult by the need to detect small quantities of agent with a high degree of confidence, taking into account the monitor’s detection limits and the presence of background interferents, to ensure that the AELs are not exceeded.

The non-stockpile program involves the carefully planned and executed dismantlement and disposal of the former chemical agent production facility at NECD. The material removed is decontaminated, if necessary, before shipment to offsite recycling or disposal facilities. The program also encompasses the destruction of recovered munitions and chemical items, many of which had been buried at military installations. Depending on the type and condition of the recovered items, they are destroyed in one of two mobile systems—the EDS or the rapid response system (RRS), which the non-stockpile program has developed and fielded for this purpose. The Army has also developed other mobile systems for use on certain types of munitions, but these systems are beyond the scope of this study. For a review of these other systems, see the NRC report Systems and Technologies for the Treatment of Non-Stockpile Chemical Warfare Materiel (NRC, 2002).

Because of their advanced age and, frequently, their deteriorated condition, non-stockpile items require treatment different from that for items in the stockpile program, by which hundreds of thousands of various munitions that have been stored in controlled environments (e.g., storage igloos) are being destroyed in state-of-the-art fixed facilities. In contrast, former production facilities are one-of-a-kind facilities that have been in disuse for over 35 years. Recovered buried chemical munitions such as those found in Spring Valley, in northwest Washington, D.C., are frequently considered unsafe or are otherwise difficult to transport, so that mobile destruction equipment must be transported to the location where they are found.

This report focuses on the unique challenges the non-stockpile program faces in implementing lowered AELs under a schedule constrained by an international treaty deadline⁵ and subject to federal and state environmental regulatory and permitting requirements. The committee notes that at the time this report was being prepared, a second, parallel National Research Council study on issues faced by the stockpile program in implementing the revised AELs was under way.

MINICAMS and DAAMS are the primary monitoring systems used for the detection of airborne agents at non-stockpile disposal sites, at stockpile disposal sites, and at agent storage facilities. MINICAMS, an automated, near-real-time (NRT) monitoring system, is presently used to monitor for HD, GB, and VX at the CDC’s 1988 TWA AELs; for GB and VX at the 1997 IDLH AELs; and for other agents of concern in the non-stockpile program. MINICAMS typically reports the concentration of agent in the air once every 3 to 10 minutes and alarms when agent is detected.

MINICAMS has also been used to monitor for HD at concentrations greater than the 1997 IDLH AEL for this agent.⁶ The use of MINICAMS to monitor for GB, HD, and VX at the CDC’s 2003/2004 IDLH levels and at the 2003/2004 STELs (numerically equal to the current TWAs) should be straightforward. It will only be necessary to develop and test an analytical method for measurement at the 2004 HD IDLH level, to slightly modify operating parameters for existing IDLH analytical methods for GB and VX, and to test the modified methods.

The main problem for MINICAMS will continue to be monitoring at the STEL for VX (equal to the CDC’s 1988 TWA value), especially at the NECD former VX production facility. When monitoring for VX at the TWA level at the NECD, the incidence of false positives—indications of concentrations above some given level when the actual concentrations are below that level—that are caused by phosphorus-containing compounds and other compounds with elution times similar to that of the G-analog of VX may be reduced by reconfiguring or upgrading the MINICAMS to improve its chromatographic resolution for phosphorus-containing compounds that do not undergo conversion to yield the G-analog of VX, that is, O-ethyl methylphosphono-

fluoridate. False positives at the TWA for VX caused by phosphorus-containing compounds other than VX that undergo conversion to yield the G-analog of VX may be eliminated by developing a MINICAMS method that can detect VX directly rather than as the G-analog. Both techniques will result in fewer interferences when monitoring for VX. Therefore, it would be preferable to monitor for VX directly and to improve chromatographic resolution. Other automated NRT monitors that have been used or tested include a system based on a thermal desorption unit connected to a gas chromatograph and a newer, improved system based on a continuous air sampler and gas chromatograph. Both are known by the acronym A/DAM. Both can be configured to achieve better chromatographic resolution and, thus, better selectivity than MINICAMS and would be expected to result in fewer false positives for phosphorus-containing compounds and other compounds with retention times similar to that of the G-analog of VX (for phosphorus-containing compounds that do not undergo conversion to yield the G-analog of VX). A method has been developed that allows an A/DAM system to determine the presence of VX directly, without the need for derivatization.

Recommendation 4-1: To reduce false positives when monitoring at critical locations susceptible to chemical interferences, the Army should explore ways to improve the gas-chromatographic resolution of the MINICAMS. As an alternative, at critical locations, the Army should consider using the A/DAM system, which can be configured to achieve better chromatographic resolution than the MINICAMS.

DAAMS, a manual monitoring system, is used to confirm or deny MINICAMS alarms—that is, reports of the presence of agent at concentrations greater than the alarm level. Because of its more sophisticated and longer-duration manual sampling and laboratory-based analysis, DAAMS has better gas-chromatographic resolution than MINICAMS. DAAMS has proved effective in monitoring for GB, HD, and VX at the 1988 TWA levels (numerically equivalent to the new STELs) through many years of successful use at non-stockpile and stockpile sites. Confirming or denying MINICAMS alarms at the new STELs will be no more difficult when using the DAAMS technique than confirming or denying alarms at the 1988 TWA levels.

Work is currently under way or has been completed at several stockpile and non-stockpile sites to modify DAAMS methods to meet the requirements of monitoring at the new AELs. Since much of this work appears to be taking place under the guidance of the local monitoring managers only, DAAMS methods and equipment configurations for monitoring at the new AELs could vary widely from site to site, especially because there seems to be only a limited exchange of timely information among the sites and staff at the Chemical Materials Agency (CMA).

Also, agent monitoring efforts at the sites appear to focus only on achieving adequate sensitivities to monitor at the new AELs. There appears to be little or no effort at the site level to improve the selectivity of DAAMS methods. Thus, although it is likely that agents can be detected at the new WPLs (and GPLs) using DAAMS, it is also likely that interference problems will be much more severe for DAAMS than in the past, especially for VX methods based on V-to-G conversion and, perhaps, for HD when using flame-photometric-detector (FPD)-based DAAMS systems. There is a CMA-directed study to improve the sensitivity and selectivity of DAAMS methods, but little information regarding this study is available to local sites, with the exception of the Umatilla, Oregon, stockpile site, where the CMA-modified DAAMS methods are being tested.

Recommendation 4-2: The Army should immediately convene a workshop of non-stockpile and stockpile personnel working on DAAMS methods from each site to allow them to exchange written procedures, test data, and other information regarding the CDC’s 2003/2004 AELs. This workshop should also offer presentations by knowledgeable technical personnel involved in the recent CMA-sponsored effort to develop more selective DAAMS methods. Also, the Army should continue to work on improving the selectivity of DAAMS methods, especially FPD-based methods, to further reduce the number of false positive alarms.

The CDC’s 2003 STEL level for VX, 1 × 10⁻⁵ mg/m³, corresponds to a concentration of about one part per trillion by volume. Not only must NRT monitoring systems be capable of detecting VX at this concentration, but they must also be capable of meeting quality assurance/quality control (QA/QC) requirements for concentrations as low as 0.5 part per trillion (equal to 0.50 STEL, the lowest level—other than the blank—used during P&A studies).⁷ In other words, automated detection systems used in the non-stockpile program are actually automated analytical instrument systems. The CDC’s 2003 WPL for VX is 1 × 10⁻⁶ mg/m³, or about 0.1 part per trillion. The DAAMS method used to monitor at this concentration must also be capable of meeting stringent QA/QC requirements, including passing P&A studies, where the lowest test concentration is about 0.05 part per trillion. In addition to measuring VX at concentrations of less than one part per trillion and meeting QA/QC requirements, auto-

mated and manual methods must be amenable to reliable, long-term operation by relatively nontechnical personnel.

For the new WPL, the only systems capable of achieving the required sensitivity and meeting other stringent requirements for historical and NRT monitoring systems in the near term are systems based on sampling using porous polymers, separation using capillary gas chromatography, and detection using flame photometry.⁸ DAAMS systems using mass selective detectors with chemical ionization are also capable of detecting VX at these levels. Other technologies, especially miniature mass spectrometers, may be able to meet the sensitivity and selectivity requirements of NRT monitoring systems in the non-stockpile program at a reasonable cost within 5 years.

Other research and development programs aimed at improving sensitivity, selectivity, and reliability in monitoring for VX, GB, and mustard are under way. The stockpile sites have the largest programs because they have historically been required to monitor at lower levels than the non-stockpile sites.

Recommendation 4-3: PMNSCM should take advantage of research and development being funded by the stockpile program to develop more selective and more sensitive DAAMS methods for monitoring VX and HD at the 2003/2004 WPLs.

Recommendation 4-4: PMNSCM should conduct a paper study of the state of miniature mass spectrometer technologies and, if warranted, support the development of near-real-time (NRT) systems based on the best available technology. The paper study should be done by technical personnel with extensive hands-on experience in air monitoring at the 1988 AELs, who—along with personnel involved in the manufacture of miniature mass spectrometers—should also conduct the effort to develop or modify mass spectrometer systems for NRT monitoring.

Recommendation 4-5: For near-real-time monitoring, the non-stockpile program should meet the 2003/2004 AELs promulgated by the CDC using an approach that establishes a sufficiently high confidence level (that is, a high statistical response rate) for the detection of excursions above 1.00 AEL. The alarm levels for near-real-time (NRT) monitors should then be set to achieve the required confidence.

The purpose of alarm levels is to ensure with a high degree of confidence that an NRT monitoring system will alarm when the true concentration of agent exceeds 1.00 AEL. The non-stockpile program sometimes uses higher alarm levels than the stockpile program, so agent excursions above 1.00 AEL are sometimes less likely to be detected by the non-stockpile program than by the stockpile program.

Recommendation 4-6: The non-stockpile program should justify sometimes using alarm levels for near-real-time monitoring systems that are different from those used by the stockpile program.

The Army used the 1988 AELs to determine whether certain types of materials (e.g., contaminated tools and contaminated buildings) posed a further hazard to workers and to implement management systems for secondary waste, much of which is defined as hazardous waste under federal and state hazardous waste laws. Known as the X Classification System, this system defines levels of agent decontamination for materials and waste and defines subsequent management procedures (U.S. Army, 2002). The Army has indicated that it not only will replace the 1988 AELs with the new 2003/2004 AELs for purposes of material and waste classification but also will substantially revise the X Classification System. It says that modification of the X Classification System for decontamination is the most controversial aspect of the whole AEL implementation process and that the main stockpile demilitarization sites have already reported major schedule delays due to permit changes required by the modification.⁹

The committee observes that the issues involved cut across all of the Army’s chemical programs. The impact on the non-stockpile program is relatively minor in comparison with impacts on the other programs. In particular, because the committee believes that the X Classification System under the new AELs is worthy of a more comprehensive examination within a larger study, it has decided not to further examine the subject in this report.

The 1960s-era facility at NECD for the production of the nerve agent VX produced the U.S. Army’s entire 4,400-ton stockpile of VX. Production of VX ceased in 1968. After production ceased, the rooms, pipes, and tanks were flushed and decontaminated using hypochlorite solution and the facility was mothballed. In August 2003, as dismantlement operations were getting under way, air monitoring in Building 143 of the NECD facility detected material suspected to be VX. Subsequent analysis of liquid samples removed from nitrogen piping showed the presence of an oxidized VX

precursor and VX degradation products. As a precaution, the Army instituted safety procedures to protect workers from possible exposure to potentially toxic organophosphorus compounds, such as VX and related compounds, in Building 143.

Compounds related to VX that may be present in the atmosphere of Building 143 also pose a potential risk to NECD workers. An examination of the chromatograms from analysis of DAAMS tubes shows perhaps two dozen compounds, most of which have not been satisfactorily identified. It is likely that at least some of these compounds are related to VX. The concentrations and toxicity of these unidentified compounds are not known with certainty. Worker protection at the Level B PPE, which includes a supplied air respirator, is recommended for protection of workers dismantling the equipment and building. NECD personnel have been using Levels C and D PPE, which employ an air purifying respirator or no respiratory protection.

Recommendation 2-1: NECD personnel working in Building 143 should be protected by Level B PPE unless the background chemicals are accurately identified, their toxicity estimated, and commensurate risk established.

The alarm set points for the MINICAMS monitoring of airborne VX concentrations at NECD will not be changed after January 1, 2005 (see Chapter 4 for a full discussion of this issue). Since the committee agrees that the new AELs can be implemented for VX at the NECD facility dismantlement project without changing the MINICAMS alarm level, it does not expect an increase in the number or frequency of MINICAMS alarms. Because the new AELs have no effect on MINICAMS STEL monitoring, no process changes are required or recommended.

Recommendation 2-4: In consultation with stakeholders, including regulators, and in accordance with the new implementation guidance at all appropriate non-stockpile sites, PMNSCM should continue to take credit for the protection provided by personal protective equipment when setting alarm levels.

The CMA guidelines for selection of PPE differ from those of general industry, and non-stockpile operation managers can select from an extensive list of Army-approved PPE. The PPE being used for the dismantlement of the NECD production facility, while providing adequate protection against airborne exposure to VX, is not the most advanced in terms of minimizing operator stress and maximizing visibility. At the NECD site, the Army uses multiple layers of protection for workers and the community, including (1) double containment of the work site, (2) monitoring at the location of the dismantlement, and (3) stopping work and starting an investigation of whether corrective action is needed whenever the NRT monitors alarm. Commercial chemical PPE that has been approved for use by the Army is listed in Appendix D.

Recommendation 2-6: The workers at NECD should be provided with state-of-the-art industrial PPE to minimize fatigue and maximize field of vision. The committee also recommends that PMNSCM consider using the best available PPE that has been certified for use with chemical agents in its other operations.

Two characteristics of the Army’s mobile explosive destruction system (EDS), which can be deployed in locations with high population densities, address concerns about operating near a civilian population:

• The EDS is deployed and operated inside a vapor containment structure (VCS) under negative pressure; the VCS uses an exhaust filtration system.

• It is monitored using both near-real-time monitors (MINICAMS) and DAAMS tubes located well beyond the boundaries of the VCS and well beyond the distance at which atmospheric dispersion models predict the concentration of any released chemical agent might present a hazard.

However, the Army does not have a clear policy or set of procedures for the design of site-specific DAAMS perimeter monitoring to protect the general population living near EDS sites.

Recommendation 2-8: To reassure the public that potential agent releases are being monitored for at EDS deployment sites, PMNSCM should develop flexible, written guidelines for the deployment of perimeter air monitors at these sites.

The Army has experienced significant delays in implementing the stockpile destruction program (GAO, 2004).¹⁰ The committee believes that the problems faced by the stockpile program could affect the non-stockpile program as well, especially with regard to environmental permitting issues and public involvement programs. As indicated in prior NRC reports on the non-stockpile program, regulatory approval and permitting (RAP) and public involvement issues have

hampered the Army’s ability to meet the CWC schedule and increased the cost of compliance as well (NRC, 1999, 2001a, 2001b, 2002, 2004a). The imposition of new AELs presents a new set of challenges for the non-stockpile program. The new AEL worker and community limits will involve a new round of regulatory approvals or amendments to existing approvals and have the potential to give rise to additional regulatory- and public-involvement-related delays and costs in meeting the CWC deadlines.

Constructive engagement with regulators and the public is essential to the completion of chemical materiel disposal in accordance with the CWC schedule. The committee believes that RAP and public acceptance are critical-path items. That is, if regulators or the public at any location raise significant objections regarding any program activity, it will become increasingly difficult for the Army to achieve its programmatic milestones. A proactive public involvement program would help, not only by reducing delays and other obstacles to the accomplishment of the disposal mission but also by providing the basis for resolving unexpected problems if they arise.

Recommendation 6-1: As the Army modifies its safety regulations (AR 385-61 and DA PAM 385-61) to address the new AELs, it should consider incorporating language that would clarify RCRA applicability to non-stockpile operations. In addition, to avoid reinventing the wheel in the many states where mobile treatment systems might be used, the Army should develop templates for modifying RAP when the new AELs are implemented for non-stockpile operations.

For the most part, the non-stockpile program has avoided delays caused by public concern and opposition. Its disposal strategies have earned widespread support, and through the Core Group, it maintains a constructive relationship with the activist public.¹¹

Recommendation 6-4: PMNSCM should develop, in consultation with the non-stockpile Core Group, a model for public involvement in the fielding of mobile systems and the implementation of monitoring systems to protect the general public.