IN-HOSPITAL RESPONSE TO EXTERNAL\
CHEMICAL EMERGENCIES:\
PERSONAL PROTECTIVE EQUIPMENT, TRAINING,\
SITE OPERATIONS PLANNING, AND MEDICAL PROGRAMS

Technical Report -- Final Draft

by\
Paul Fedele, PhD\*,\
Panos Georgopoulos, PhD^†^, Pamela Shade^†^, Paul Lioy PhD^†^,\
Michael Hodgson, MD, MPH\*\*, Mark A. Brown, PhD\*\*

\*U.S. Army Soldier and Biological Chemical Command (SBCCOM)

*^†^Environmental and Occupational Health Sciences Institute (EOHSI)*

\*\*Veterans Health Administration (VHA)

*April 15, 2003*

# TABLE OF CONTENTS {#table-of-contents .unnumbered}

[TABLE OF CONTENTS i](#table-of-contents)

[LIST OF TABLES ii](#list-of-tables)

[LIST OF FIGURES iii](#list-of-figures)

[ACKNOWLEDGEMENTS v](#acknowledgements)

[1. SUMMARY 1](#summary)

[2. INTRODUCTION 2](#introduction)

[3. HAZARD AND EXPOSURE ASSESSMENT: METHODS, ANALYSIS AND RESULTS
6](#hazard-and-exposure-assessment-methods-analysis-and-results)

[3.1. Site Operations Planning 7](#site-operations-planning)

[3.2. Background and Motivation for Hazard Assessment
8](#background-and-motivation-for-hazard-assessment)

[3.3. Purpose of Hazard Assessment 9](#purpose-of-hazard-assessment)

[3.4. Realistic Maximum Hazard Levels
9](#realistic-maximum-hazard-levels)

[3.5. Evaporation Process 11](#evaporation-process)

[3.6. Evaporation Rate and Adsorption/Desorption
11](#evaporation-rate-and-adsorptiondesorption)

[3.7. Vapor Generation at the Decontamination Site
12](#vapor-generation-at-the-decontamination-site)

[3.8. Constant Flow, Uniform Mixing Approximation
13](#constant-flow-uniform-mixing-approximation)

[3.9. Exposure Modeling 14](#exposure-modeling)

[3.10. Discussion of Modeling Results
17](#discussion-of-modeling-results)

[4. TRAINING NEEDS 34](#training-needs)

[5. MEDICAL SURVEILLANCE 35](#medical-surveillance)

[6. CONCLUSION 36](#conclusion)

[6.1. Local: facility level 36](#local-facility-level)

[6.2. Local: Area Emergency Planning Committees
36](#local-area-emergency-planning-committees)

[6.3. National Level 36](#national-level)

[REFERENCES 37](#references)

[APPENDIX: ACRONYMS AND SYMBOLS 44](#appendix-acronyms-and-symbols)

# LIST OF TABLES {#list-of-tables .unnumbered}

[Table 1. Description of the levels of Personal Protective Equipment
(PPE) as well as any inherent limitations.
4](#__RefHeading___Toc38171596)

[Table 2. Summary of the properties of chemical warfare agents (CWA) and
selected toxic industrial chemicals. The volatility and time constant ()
for the evaporation process determine how quickly an agent will
evaporate upon dissemination. The concentration of the CWA that is
lethal to 50% of the population after a one-minute exposure (LCt~50~) is
provided as well as the dose that is lethal to 50% of the population
(LD~50~). The 100 g deposition of agent is an upper bound release from
typical dissemination devices. The larger number of lethal doses per
100 g of CWA indicate increased potential harm to those exposed.
19](#__RefHeading___Toc38171597)

[Table 3. Number of lethal doses resulting from a 100 g deposition of a
chemical warfare agent. The 100 g deposition of agent is an upper bound
release from typical dissemination devices. The larger number of lethal
doses per 100 g of CWA indicate increased potential harm to those
exposed. 20](#_Ref36019265)

[Table 4. Percentiles of the Monte Carlo forecasted total integrated
exposure concentration (*CT*) of sarin. The concentration is the
predicted exposure of medical personnel as victims present themselves to
the medical treatment facility for decontamination and triage. The Monte
Carlo trials represent the initial mass deposition (*m~o~*) with an
appropriate beta distribution (shown in Figure 4).
21](#__RefHeading___Toc38171599)

[Table 5. Percentiles of the Monte Carlo forecasted total integrated
exposure concentration (*CT*) of sarin. The concentration is the
predicted exposure of medical personnel as victims present themselves to
the medical treatment facility for decontamination and triage. The Monte
Carlo trials represent the initial mass deposition (*m~o~*) with a
triangular distribution with a maximum value of 100 g and a likeliest
value of 10 g. 22](#__RefHeading___Toc38171600)

[Table 6. Percentiles of the Monte Carlo forecasted total integrated
exposure concentration (*CT*) of sarin. The concentration is the
predicted exposure of medical personnel as victims present themselves to
the medical treatment facility for decontamination and triage. The Monte
Carlo trials represent the initial mass deposition (*m~o~*) with a
triangular distribution with a maximum value of 100 g and a likeliest
value of 10 g. The evaporation rate of sarin (*~evap~*) is described by
an exponential distribution as a realistic estimate of the desorptive
evaporation rate. 23](#__RefHeading___Toc38171601)

[Table 7. Percentiles of the Monte Carlo forecasted total integrated
exposure concentration (*CT*) of sarin. The concentration is the
predicted exposure of medical personnel as victims present themselves to
the medical treatment facility for decontamination and triage. The Monte
Carlo trials represent the initial mass deposition (*m~o~*) with a
triangular distribution with a maximum value of 100 g and a likeliest
value of 10 g. In this scenario the contaminated body surface area is
assumed to be 20%, which represents the potential exposure to healthcare
workers when victims immediately disrobe.
24](#__RefHeading___Toc38171602)

# LIST OF FIGURES {#list-of-figures .unnumbered}

[Figure 1. Depiction of the presence of a secondary source of exposure
to healthcare workers (decon staff) that are downwind of arriving
victims. Exposure would arise from evaporation of agent from victims'
clothing prior to disrobing and showering. Worst-case conditions are
used to estimate an upper bound of exposure; if recommended
decontamination procedures are followed, this scenario would be highly
unlikely. 5](#__RefHeading___Toc38171603)

[Figure 2. Schematic depiction of free-surface evaporation process of a
liquid agent. The evaporative flux is the rate of change of
surface-deposited mass with time. It depends on the volatility and an
evaporation rate of the liquid. 25](#__RefHeading___Toc38171604)

[Figure 3. Total integrated exposure concentration (*CT*) of CWA for
medical personnel as a function of the evaporation time constant (). The
time interval begins after a 10-minute lag time during which some
material has evaporated; the evaporation will continue as
decontamination proceeds. The time-integrated exposure concentration is
then the sum of exposure concentration as contaminated patients file
past the medical personnel. This concentration is dependent upon the
evaporation time constant () which is the characteristic time for
volatilization of the liquid agent. When is small the majority of the
agent evaporates prior to arrival at the medical treatment facility; for
agents with a larger , little agent will evaporate not only during
transport to the medical facility, but throughout the decontamination
process. 26](#__RefHeading___Toc38171605)

[Figure 4. Frequency density of initial mass deposition (*m~o~*) of
sarin which describes the frequency with which victims will be
contaminated with a specific amount of sarin. This density is based on
the assumption of a two-dimensional Gaussian distribution that
represents a uniform density of people and the likely mass deposition of
the CWA as the radial distance increases from the dissemination device.
27](#__RefHeading___Toc38171606)

[Figure 5. Beta distribution with =0.52 and =1.20 representing the
initial mass deposition (*m~o~*) of sarin. The distribution was chosen
as an appropriate fit corresponding to the frequency density shown in
Figure 3 and is used in subsequent Monte Carlo simulations to determine
the total exposure to sarin received by medical personnel.
28](#__RefHeading___Toc38171607)

[Figure 6. Monte Carlo forecast of total integrated exposure
concentration (*CT*) of sarin when the mass deposition (*m~o~*) is
represented by the beta distribution presented in Figure 4. The
time-integrated exposure concentration is then the sum of exposure
concentration as contaminated patients file past the medical personnel.
The integration begins after a 10-minute lag time which represents
transport time to the facility; the integration is stopped when the
decontamination process ends. 29](#__RefHeading___Toc38171608)

[Figure 7. Monte Carlo forecast of total integrated exposure
concentration (*CT*) of sarin when the mass deposition (*m~o~*) is
represented by a triangular distribution with a maximum value of 100 g
and a likeliest value of 10 g. The time-integrated exposure
concentration is then the sum of exposure concentration as contaminated
patients file past the medical personnel. The integration begins after a
10-minute lag time which represents transport time to the facility; the
integration is stopped when the decontamination process ends.
30](#__RefHeading___Toc38171609)

[Figure 8. Monte Carlo forecast of total integrated exposure
concentration (*CT*) of sarin when the evaporation rate of sarin
(*~evap~*) is described by an exponential distribution as a realistic
estimate of the desorptive evaporate rate. The mass deposition (*m~o~*)
is represented by a triangular distribution with a maximum value of
100 g and a likeliest value of 10 g. The time-integrated exposure
concentration is then the sum of exposure concentration as contaminated
patients file past the medical personnel. The integration begins after a
10-minute lag time which represents transport time to the facility; the
integration is stopped when the decontamination process ends.
31](#__RefHeading___Toc38171610)

[Figure 9. Monte Carlo forecast of total integrated exposure
concentration (*CT*) of sarin when the mass deposition (*m~o~*) is
represented by a triangular distribution with a maximum value of 100 g
and a likeliest value of 10 g. The time-integrated exposure
concentration is then the sum of exposure concentration as contaminated
patients file past the medical personnel. The integration begins after a
10-minute lag time which represents transport time to the facility; the
integration is stopped when the decontamination process ends. In this
scenario the contaminated body surface area is assumed to be 20%, which
represents the potential exposure to healthcare workers when victims
immediately disrobe. 32](#__RefHeading___Toc38171611)

[Figure 10. Emergency response steps for survivors of chemical attack
seeking medical attention at hospital ER. The "hot" zone represents the
site of the CWA release, while the "cold" zone is the area with no
expected contamination. The "warm" zone denotes areas where contaminated
victims present themselves for decontamination. As the contaminated
patients arrive at the medical treatment facility, they become sources
of contamination for the medical personnel who must adhere to the
recommended steps to minimize exposure. Health care workers in each zone
also limit exposure when covered by the appropriate level of personal
protective equipment. 33](#__RefHeading___Toc38171612)

# ACKNOWLEDGEMENTS {#acknowledgements .unnumbered}

This work originated in several overlapping committees convened to plan
an agency-wide response to the possibility of chemical terrorism and the
role of hospitals supporting decontamination. The authors wish to
acknowledge the thoughtful and important support of James Genovese of
SBCCOM; Art Stuempfle, Ph.D. of OptiMetrics; Jim Farsetta, Edward
Thorsland, Craig Hyams, M.D., M.P.H., Susan Mather, M.D., M.P.H., John
Beatty, Margie Scott, M.D., and Vernon Wilkes of VHA; Scott Deitchmann,
M.D. of NIOSH; Melody Sands and Atkinson Longmire, M.D., M.P.H. of OSHA;
and Linda Everett of EOHSI.

# SUMMARY

Hospitals removed from the immediate site of an incident involving the
release of hazardous materials, including chemical warfare agents, must
develop emergency response plans to receive victims and simultaneously
protect healthcare professionals from toxic chemicals, including weapons
of mass destruction. This paper reviews four technical issues essential
to the success of these plans.

1.  Hospital personnel who work with contaminated individuals should
    receive at least eight hours of training on personal protective
    equipment and decontamination and be retrained at least annually to
    work safely; more frequent equipment practice is strongly
    recommended.

2.  Development and coordination of protocols must include the local
    emergency planning committee, with clear assignment of tasks and
    locations, such as clothing removal for primary decontamination.
    Failure to plan this single most important contribution to exposure
    reduction through systematic local coordination puts hospital
    personnel at grave risk of adverse effects.

3.  Site operations planning must address decontamination runoff and
    contaminated clothing control, as these are both potential sources
    of secondary exposure. Failure to control them increases risk for
    staff.

4.  Level C personal protective equipment, though not appropriate for
    work at the site of the hazardous materials releases, is adequate to
    protect hospital staff away from the site of release despite
    off-gassing of agents that have been identified as possible causes
    of incidents. This conclusion is based on the development of
    worst-case evolution of scenarios for which none of the identified
    or planned exposure control strategies are actually implemented.
    Preventing exposures to healthcare workers does require that plans
    and procedures are in place, coordinated, and trained for.

# INTRODUCTION

The Nunn-Lugar Act, first approved in 1991 in response to the
disintegration of the Soviet Union (Reaves, 2001) was designed to limit
the threat of terrorism; this act increased in relevance after September
11, 2001. The status of research and development to ensure and improve
proper civilian medical response to chemical and biological terrorism
was assessed by the Institute of Medicine/National Research Council in
1999 (IOM/NRC, 1999). Ongoing terrorist threats have generated far more
widespread civilian emergency response planning and development. These
include the formation of Metropolitan Medical Response Teams (MMRTs),
the promulgation of new standards demanded by the Joint Commission on
Accreditation of Healthcare Organizations (JCAHO) (JCAHO, 2003), and the
development of standards for personal protective equipment (PPE) (NIOSH,
2001) in "hot" and "warm" zones (see Page [7](#site-operations-planning)
and Figure 10 for detailed explanation of zones). PPE comes in various
"levels," (OSHA, 1995a), described in Table 1 (see also Lindsay, 1999a,
1999b, 2001; Foust, 1999). The appropriate level of protection and
victim decontamination for healthcare remains to be defined (Fairfax,
1992, 1999, 2002a, 2002b; Arnold & Lavonas, 2003; ATSDR, 2001b),
especially in the case of the appearance of victims of attacks at the
front door of an emergency room.

Chemical incidents are thought to be possible through several different
scenarios. These possibilities include the release of chemical warfare
agents, such as nerve gases (e.g. sarin, VX) or blister agents (e.g.
mustard), with detailed information on appropriate responses available
(see e.g. two SBCCOM reports: Lake et al., 2000, SBCCOM, 2002; also
ATSDR, 2002, and Sidell et al., 2002). Another possibility of accidental
harmful chemical release may involve adverse transportation events
(USAF, 1990). The Centers for Disease Control and Prevention (CDC) has
developed a list of agents and clinical implications (CDC, 2003),
including those most likely released through the opportunistic use of
weapons of mass destruction or chemical transportation accidents (i.e.,
tanker trucks and railcars) by terrorists. However, this is not an all
inclusive list for the types of situations that may yield the
instantaneous or continuous release of toxic chemicals. Standard
protocols provide appropriate response to such events; one such
publication (Bronstein & Currance, 1994) advocates the use of high level
PPE.

Emergency planning has led many hospitals to develop chemical hazard
plans for emergencies arising within hospitals and in the community,
such as may occur from terrorist attacks (Kirk et al., 1994; Huff, 1991;
Brennan et al., 1999). Much discussion has focused on the appropriate
level of PPE needed to protect healthcare workers as they address the
health needs of contaminated patients (CDC, 1997). Many hospitals have
expressed concern about the widespread expectation for level A or level
B PPE. Although highly trained response teams, with monthly practice,
may feel comfortable intubating patients and performing triage
(Stopford, 2001), many hospitals consider the use of level C PPE at the
top end of their reasonable range (MacIntyre et al., 2000). Standards
promulgated by the Occupational Safety and Health Administration (OSHA)
on hazardous waste operations (OSHA, 1995a) and respiratory protection
(OSHA, 1995b; NIOSH, 2001) require a hazard analysis to justify
selection of specific equipment. In addition, hospitals must train
employees adequately to an appropriate level of skill in the use of
personal protective equipment and in decontamination procedures. As part
of such programs, they must include medical testing and surveillance
under the same two OSHA standards (Levitin & Siegelson, 1996). All of
these issues must be examined in order to achieve an effective plan that
both protects healthcare workers, and allows for the decontamination of
victims prior to triage and treatment.

The Veterans Health Administration (VHA) consists of 142 hospital
systems (many with multiple campuses), 800 clinics, and 200 nursing
homes around the United States, with approximately 210,000 healthcare
workers. As a large integrated healthcare system, it must provide a
certain level of central policy guidance for facilities. In an effort to
identify and define needed resources, the VHA convened groups to develop
a hazard and exposure assessment, identify needed actions for compliance
with OSHA standards, review site and operational planning issues, and
resolve medical testing issues.

This report develops a hazard and exposure assessment to identify an
adequate level of PPE and defines the associated local emergency
planning, medical surveillance, and training elements needed to meet
OSHA, EPA, and JCAHO requirements. To that end, it uses worst-case
conditions to estimate an upper bound of exposure, as illustrated in
Figure 1.

[]{#__RefHeading___Toc38171596 .anchor}Table 1. Description of the
levels of Personal Protective Equipment (PPE) as well as any inherent
limitations.

+-----+--------------+----------+---------+-------------+------------+
| **L | **Elements** | **       | **Usual | **Maximal   | **Con      |
| eve |              | Protects | time    | period      | straints** |
| l** |              | a        | r       | available   |            |
|     |              | gainst** | equired | to work**   |            |
|     |              |          | to put  |             |            |
|     |              |          | on and  |             |            |
|     |              |          | remove  |             |            |
|     |              |          | PPE**   |             |            |
+-----+--------------+----------+---------+-------------+------------+
| A   | Fully        | All      | 15      | ap          | Card       |
|     | e            | unknown  | minutes | proximately | iovascular |
|     | ncapsulating | agents   |         | 60 minutes  | risk;      |
|     | for vapor    |          |         | in two      | exercise   |
|     | barriers     |          |         | periods     | li         |
|     |              |          |         | (two 60     | mitations; |
|     | Se           |          |         | minute,     | heat       |
|     | lf-contained |          |         | "fea        | stress     |
|     | breathing    |          |         | therweight" |            |
|     | apparatus    |          |         | bottles,    | Visibility |
|     |              |          |         | with bottle | c          |
|     |              |          |         | replacement | onstraints |
|     |              |          |         | time needs) | in face    |
|     |              |          |         |             | shields    |
|     |              |          |         |             | (fogging;  |
|     |              |          |         |             | perimeter  |
|     |              |          |         |             | vision)    |
|     |              |          |         |             |            |
|     |              |          |         |             | Glove use  |
|     |              |          |         |             | (          |
|     |              |          |         |             | palpation, |
|     |              |          |         |             | fine motor |
|     |              |          |         |             | man        |
|     |              |          |         |             | ipulation) |
+-----+--------------+----------+---------+-------------+------------+
| B   | E            | Splash   | 15      | ap          | Card       |
|     | ncapsulating | pr       | minutes | proximately | iovascular |
|     | suits        | otection |         | 60 minutes  | risk;      |
|     |              |          |         | in two      | exercise   |
|     | Se           | Airborne |         | periods     | li         |
|     | lf-contained | hazards  |         | (two 60     | mitations; |
|     | breathing    |          |         | minute,     | heat       |
|     | apparatus    |          |         | "fea        | stress     |
|     |              |          |         | therweight" |            |
|     |              |          |         | bottles,    | Visibility |
|     |              |          |         | with bottle | c          |
|     |              |          |         | replacement | onstraints |
|     |              |          |         | time needs) | in face    |
|     |              |          |         |             | shields    |
|     |              |          |         |             | (fogging;  |
|     |              |          |         |             | perimeter  |
|     |              |          |         |             | vision)    |
|     |              |          |         |             |            |
|     |              |          |         |             | Glove use  |
|     |              |          |         |             | (          |
|     |              |          |         |             | palpation, |
|     |              |          |         |             | fine motor |
|     |              |          |         |             | man        |
|     |              |          |         |             | ipulation) |
+-----+--------------+----------+---------+-------------+------------+
| C   | Negative     | Splash   | 1-5     | 8 hour      | Heat       |
|     | pressure     | pr       | minutes | shift with  | illness    |
|     | respirator   | otection |         | rest breaks |            |
|     |              |          |         | for heat    |            |
|     | Splas        | Some     |         | illness     |            |
|     | h-protecting | airborne |         | management  |            |
|     | suits        | hazards  |         |             |            |
+-----+--------------+----------+---------+-------------+------------+
| D   | No           |          |         |             |            |
|     | respirator   |          |         |             |            |
+-----+--------------+----------+---------+-------------+------------+

![](media/image1.jpeg){width="5.5465277777777775in"
height="5.033333333333333in"}

[]{#__RefHeading___Toc38171603 .anchor}Figure 1. Depiction of the
presence of a secondary source of exposure to healthcare workers (decon
staff) that are downwind of arriving victims. Exposure would arise from
evaporation of agent from victims' clothing prior to disrobing and
showering. Worst-case conditions are used to estimate an upper bound of
exposure; if recommended decontamination procedures are followed, this
scenario would be highly unlikely.

# HAZARD AND EXPOSURE ASSESSMENT: METHODS, ANALYSIS AND RESULTS

To understand the required level of PPE and associated operational
strategies, specific actions were taken for the current study:

1.  **Discussions to define issues, tasks, and responsibilities:** Three
    overlapping groups discussed hospital planning in face-to-face,
    electronic (email), and telephone communications. Group members
    included clinical and clinical administrative staff (medical center
    directors, regional corporate directors), toxicology and
    occupational medicine, industrial hygiene and safety, physics,
    exposure assessment, chemical engineering, public health, safety
    regulation, and computer modeling. The initial starting point for
    these discussions was the Chemical Stockpile Emergency Preparedness
    Program (CSEPP) (FEMA, 2003). These discussions outlined likely
    scenarios, defined roles, tasks, and responsibilities and considered
    site consequences, in part based on national discussions and
    resources.

2.  **Theoretical work to assemble equations and derive important
    constraints:** A first step was to develop relevant conceptual
    models and to assemble equations for chacterizing estimates of
    source attributes for the chemical vapor hazards produced by
    contaminated patients. These equations could then be used to derive
    relationships between operational parameters (time and distance from
    sites and sources) and exposures generated by the patients acting as
    sources of contamination.

3.  **Dissemination of materials and identified problems:** Written
    materials, i.e., text, equations, modeling spreadsheets, and visual
    presentations were circulated for the solicitation of comments and
    suggestions for refining the issues. Individual participants
    reviewed and used the various materials to identify weaknesses,
    missing critical information, and faulty assumptions.

4.  **Face-to-face meeting to develop scenarios, refine questions, and
    define likely important modeling parameters:** A face-to-face
    meeting was held to review concerns and walk through the assumptions
    and scenarios, to identify weaknesses and omissions, and to define
    the release, exposure, decontamination and triage scenarios to be
    modeled.

5.  **Identify model parameters for range finding:** Modeling experts
    identified appropriate models, used an existing array of models in
    the laboratory, and compared the results from these with available
    pertinent published data.

6.  **Review model assumptions and operational implications:** These
    results were reviewed in a face-to-face meeting to define weaknesses
    and the resulting operational needs.

7.  **Refine needed model inputs and operational consequences:** An
    updated set of models was developed based on refinements with
    operational recommendations.

OSHA Standards, interpretations, and letters were reviewed to determine
what level of skill, training, and response is expected of healthcare
facilities (Fairfax, 1992, 1999, 2002a, 2002b). Finally, medical program
content was defined by reviewing the pertinent standards, considering
the levels of protection and decontamination required to provide
effective medical care, and reviewing the scientific literature on
appropriate medical surveillance.

A large hospital system, such as VHA, has facilities in a variety of
settings vulnerable to an equally broad range of hazards and exposures
to weapons of mass destruction, based on local differences in targets
and parallel resources. For example, in some densely populated urban
areas, the VA hospital is adjacent to a modern university hospital. In
some relatively rural areas, and mid size cities, the VA hospital is the
single largest healthcare facility. Consequently, a national plan would
be both inadequate and inappropriate. Locally appropriate emergency
planning can be more effectively accomplished at the local (municipal)
level.

Hazards broadly covered under this assessment initially included the
traditional weapons of mass destruction identified as likely agents in
the US Army Chemical Casualty Care Handbook (USAMRICD, 2000). Subsequent
discussions suggested that industrial chemicals, that are commonly
transported, might also be used as weapons. Several lists of such agents
are available, including one posted on the website of the Agency for
Toxic Substances and Disease Registry (ATSDR), identifying approximately
140 such agents (ATSDR, 2001a) and one in the Army Field Manual 3-9,
*Potential Military Chemical/ Biological Agents and Compounds* (US Army,
1990). Discussions identified agents with a broad range of physical
characteristics (vapor pressure), toxicology (dermal, systemic,
respiratory effects), and exposure routes (dermal, inhalation). Table 2
presents example agents in the broad spectrum of potential CWAs, with
corresponding critical physical, chemical, and toxicological
characteristics. Water is also included in this table, for comparison
purposes.

## Site Operations Planning

The National Institute for Standards and Technology (NIST) is leading
the development of standards for personal protective equipment for "hot"
and "warm" zone work, i.e., in sites with active release of and
potential exposure to chemical agents (NIST, 2002). The implicit
assumption has been that such areas are geographically distinct from
hospital emergency departments. Protection needs for healthcare workers
might therefore be less stringent for two reasons. First, the active
primary source of chemical agent, whether from a terrorist device or
from a transportation accident, will no longer contribute to exposures.
Second, the time since exposure will have led to a reduction in agent
left to be released, due to evaporation (or off-gassing from the
contaminated patient) (Westin et al., 1998).

Tasks for healthcare workers and others include decontamination, triage,
and treatment in various settings. Clinical treatment guidelines after
diagnoses are clear. No clinical algorithms have been published to guide
non-clinicians (technicians), but specific treatment is needed only for
chemical asphyxiants (cyanide) and cholinesterase inhibitors (nerve
agents) (ATSDR, 2001c). Discussions revealed the presence of some
confusion regarding planning for decontamination, triage, and treatment
at the local level. In many settings, clothing removal, where much of
the chemical contamination resides, was not considered to be an
essential first step. This oversight may lead to unnecessary and
preventable exposure to emergency transport personnel due to the
continued presence of the secondary source (Torngren et al., 1998).
Additionally, site operations planning must address decontamination
runoff and contaminated clothing control, as these are both potential
sources of secondary exposure (USEPA, 2000).

A roundtable of experts reviewed known terrorist devices and the
possible delivered doses. In addition, assumptions about battlefield
exposure**/**dose delivery from chemical warfare agents were reviewed
and considered (Fulco et al., 2000). Agent exposures might occur through
aerosol spray or vapor generation (US Army, 1990; Winters & Chenoweth,
2002). Both condensation and evaporation may modify the dispersion of
the airborne agents. An assumed reasonable upper bound of agent
deposition on individuals is 100 g, if the individual is in the direct
line of dissemination. In general, much lower exposure would be expected
as most of the deposited agent will be on clothing (Jenkins et al.,
1992).

## Background and Motivation for Hazard Assessment

The event of 20 March 1995 in Tokyo was used as an example scenario of
what could take place in a chemical terrorism event. In that case,
members of a Japan-based cult, Aum Shinrikyo, placed eleven bags
containing a dilute mixture of sarin on five subway cars in the Tokyo
subway system. Some of these bags were punctured, dilute agent mixture
spread across the floor of the subway cars, and some people were
overcome by the sarin. The mixture was about 30% sarin; it also
contained other compounds that gave it a strong, irritating odor. This
odor alerted people to the presence of a chemical hazard, whether or not
they had received a significant exposure to sarin. The overall result
was that thousands of people, considered the "worried well", sought
immediate medical attention (Nakajima et al., 1997; Ogawa et al., 2000;
Ohbu et al., 1997).

Many people who suspected that they had been exposed to a dangerous
chemical went directly to various Tokyo medical facilities.
Self-referred patients arrived at medical facilities without undergoing
any decontamination process. Actions as simple as removing one's shoes,
were not implemented; this oversight was significant, due to the nature
of the spill. (After leaking from the punctured bags, the sarin
presumably spread over the floor and could be most easily picked up on
shoes.) Under these conditions, victims brought contamination into
medical facilities capable of producing sarin vapor exposures sufficient
to cause noticeable effects among medical staff, even though the
arriving patients were not overcome by their own contamination. Since
the affected medical staff did not necessarily touch victims, the
presence of a vapor hazard can be inferred.

In the event of terrorism involving chemical warfare agents, it is
anticipated that some self-referred patients, who have not experienced
any decontamination process, will seek medical aid wherever the public
perceives aid to be available. Such locations include Veteran's
Administration Medical Centers. The arrival of these contaminated
persons would present a hazard to the personnel at the medical facility
and would threaten the ability of medical personnel to continue
providing necessary medical care (Nozaki et al., 1995; Okumura et al.,
1998; Ohbu et al., 1997). Should a medical facility become contaminated
with a Chemical Warfare Agent (CWA) and should the medical center
personnel begin to exhibit chemical exposure effects, the facility would
be effectively shut down.

To help reduce hazards to medical facility personnel, and to avert a
shutdown of medical facilities, it is important that all medical
treatment facilities develop the capability to remove and safely store
contaminated clothing, and then decontaminate persons who can be
expected to seek medical attention at the facility, after a potential
exposure to a CWA. The appropriate number of personnel will depend on
the situation of the facility; it will vary with the community and with
the facility's medical role in the community.

## Purpose of Hazard Assessment

The goal of efforts by the VHA and the US Army Soldier and Biological
Chemical Command (SBCCOM) is to identify the amount of vapor protection
needed by personnel at a medical facility, who may be called upon to
eliminate the "personal" secondary source of chemical agent on the
victim, and decontaminate self-referred or Emergency Medical Technician
(EMT) transported victims of a CWA incident. To support this effort,
vapor sources must be identified and quantified. Vapor sources determine
the rate and amount of vapor generated by a contaminated individual.
These terms support the overall estimate of the vapor hazards produced
by a group of contaminated victims (Hartmann, 2001; Thornton, 1990;
Crosier & Sommerville, 2002).

## Realistic Maximum Hazard Levels

The maximum vapor concentration of a chemical compound that can exist in
air is known as its saturation level. While saturated vapor levels can
be produced in the laboratory, it is not reasonable to expect that vapor
saturation would be achieved in a real-world terrorist incident.
Estimation of a reasonable potential maximum vapor exposure
(time-integrated vapor concentration) is needed to determine necessary
protection levels.

A reasonable maximum vapor concentration was needed for establishing a
standard for Self-Contained Respiratory Protection against Chemical,
Biological, Radiological Nuclear and Explosive (CBRNE) Materials (Arnold
& Lavonas, 2003). In creating such a standard, The National Institute
for Occupational Safety and Health (NIOSH) chose a range of
dissemination devices that represent possible terrorist devices.
Dissemination from these devices was modeled by SBCCOM (Fulco et al.,
2000; NIOSH, 2001) and the maximum vapor concentration produced by each
device was determined. A reasonable maximum vapor concentration was
determined as the average of all device maximum concentrations, but only
from those which produced exposures above the 50% lethality level. The
resulting vapor concentration was applied as the vapor concentration
against which Self Contained Breathing Apparatus (SCBA) protective
performance standards were written. For sarin, which has a saturation
concentration of over 20,000 mg/m^3^ at 25°C, a reasonable vapor
concentration is 2,000 mg/m^3^ or less than one tenth of saturation
(Mioduszewski et al., 1998). The reasonable maximum concentration is not
the absolute maximum that is physically possible, but rather a maximum
that can be reasonably expected in a terrorist incident.

The amount of vapor generated by contaminated individuals primarily
depends on the amount of contamination that a self-referred person, or
EMT forwarded person, will likely bring to a medical facility. In
determining the vapor source on the victim's body and clothing, it is
necessary to determine the maximum reasonable amount of contamination
that individuals might bring to a medical facility. To determine this
value, the same procedures are followed that were used to establish the
NIOSH SCBA standard vapor challenge concentration (NIOSH, 2001).

This evaluation commenced with consideration of the same set of
terrorist devices that were used to establish the reasonable maximum
vapor concentration in the NIOSH SCBA standard. In order to ensure a
conservative starting estimate, rather than characterizing the
dissemination of a volatile agent, such as sarin, the dissemination of a
non-volatile agent, such as VX, was considered. The amount of agent
deposited on victims and their clothing was determined, without any
evaporation occurring during the dissemination process. Allowing no
evaporation during the dissemination process will maximize the liquid
deposited on people. Evaporation is only considered once the CWA has
deposited.

The amount of contamination on people will depend on the amount of
material in the dissemination device, where the individual is located
with respect to the dissemination device, and what they are wearing at
the time of contact. Using SBCCOM expertise in liquid dissemination
processes, the radius of liquid dissemination and amount of liquid per
unit area, within the dissemination radius (Fulco et al., 2000) was
determined. Assuming that this total amount is deposited on a person,
the amount of contamination expected was estimated to be 100 g of agent
per individual.

Chemical warfare agents are designed to be lethal. By official
Department of Defense (DOD) cutaneous toxicity estimates, given by
Grotte & Yang, (1998), 100 g yields the number of lethal doses for the
indicated CWA, as shown in Table 3.

People who receive such high numbers of lethal doses will not survive
long enough to get to a medical facility on their own (Moore, 1998b;
Moore, 1998a). Thus, there is a practical upper limit to the amount of
contamination that a self-referred victim can be expected to bring to a
medical facility (Neumann & Kimmel, 1998). However, because it is
desirable to ensure that the vapor hazard levels are reasonable maximum
values, the influence of the agent on the individual victims is ignored
and it is assumed that all contaminated victims are capable of getting
to the medical facility. Thus it is considered that individuals who come
to the medical facility receive 100 g of contamination on (surface) and
in (inhaled) their body and their clothing at the inception of the
incident.

The scenario of interest does not include an attack on the medical
facility; victims are assumed to arrive at the medical facility at some
reasonable time after the dissemination occurs. The focus of this study
is not to prepare medical facilities so that they can continue to
function during a CWA attack at the facility itself, but rather to
ensure that the facility and its associated personnel are capable of
dealing with a number of victims arriving by foot, car or EMT transport,
as a result of a chemical release, which occurred outside the immediate
vicinity of the medical facility (Broadwater, 1999).

So, ten minutes are allowed between the dissemination of the agent and
the arrival of self-referred, contaminated victims at the medical
facility, which is consistent with the arrival times that occurred in
the Tokyo sarin incident (Ohbu et al., 1997). Emergency medical
personnel also consider this to be a reasonable time between incident
inception and arrival at a medical facility.

During this time, the evaporation of the agent will not be ignored (Topp
et al., 1997). Evaporation is assumed to begin after the conclusion of
the dissemination and deposition processes. The agent continues to
evaporate as victims travel to the medical facility and once they arrive
at the medical facility, prior to decontamination. Evaporation before
arrival at the facility will limit the vapor hazards created by
extremely volatile, quickly evaporating, materials such as phosgene,
chlorine, and hydrogen cyanide, all of which are gases at standard
conditions (Kukkonen et al., 2001).

## Evaporation Process

To determine how much vapor will be generated at a hospital
decontamination site, the evaporation rate must also be determined (Topp
et al., 1997). Evaporation from free liquid surfaces is first
considered. Transport models typically deal with evaporation from free
liquid surfaces by applying a finite, constant, evaporation rate until
the liquid is completely gone. (The U.S. Army Personal Computer Program
for Chemical Hazard Prediction or D2PC (Rogers et al., 1990) is the
transport and diffusion model used for hazard estimation in CSEPP). The
rate of change of surface-deposited mass is given by the evaporative
flux of material (mass per unit area per unit time,
$\frac{\text{dm}}{\text{dt}}$) from the liquid free surface, or

$\frac{\text{dm}}{\text{dt}}\  = \  - C_{\text{Vol}}\ v_{\text{evap}}$,

mg/m^2^), *C~Vol~* is the volatility of the liquid (mg/m^3^), and
*ν~evap~* is an empirically determined evaporation transfer rate
(m/min). The evaporation transfer rate is technically a vector taken to
be away from and normal to the liquid surface. The evaporation transfer
rate is the quantity which specifies the finite, constant, evaporation
rate. The evaporation process is schematically illustrated in Figure 2.

Since sarin has about the same volatility as water, this evaporation
time has been verified by observing the evaporation of water on a
low-humidity day. Water and sarin have very similar volatilities: 22,900
versus 22,000 mg/m^3^, at 25°C (Mioduszewski et al., 1998). However,
while the air may hold a substantial level of water vapor at normal
relative humidity, the air seldom holds any ambient level of sarin.
Thus, sarin can generally be expected to evaporate from a liquid free
surface somewhat faster than water, on most days.

A typical evaporation transfer rate of water (*ν~evap~)* is
approximately 10 cm/min, or 0.10 m/min. (Of course, in reality, this
value will vary with temperature and other ambient conditions.) This
value applies to molecules with volatilities in the range of most CWAs.
With a volatility of about 20 g/m^3^, and an evaporation rate of
0.10 m/min, 100 g of sarin/m^2^ will completely evaporate in 50 minutes
(Ellison, 1999; Munro et al., 1999; Rosenblatt et al., 1995).

## Evaporation Rate and Adsorption/Desorption

Free-surface evaporation does not consider evaporation from an adsorbed
state. As the depth of the liquid becomes small, the remaining liquid
can adhere to surfaces and the rate of evaporation will decrease (Hatch
et al., 1987). As the free liquid surface vanishes and the molecules
desorb from the surface itself, the mass evaporation process can be
characterized by an evaporation rate that is proportional to the amount
of mass per unit area remaining on the surface. This scenario is
particularly true of evaporation from porous surfaces, such as
represented by clothing (Karlsson & Huber, 1996; Kukkonen et al., 2001).
Under these conditions, the evaporation process is better described as

![](media/image2.pct)

where *m*~0~ is the amount of mass per unit area at which desorption
begins to effect the evaporation rate, and is the time constant of the
evaporation process for the remaining mass. The time constant, , is not
the time required for complete evaporation, but rather the time for
about 63% of the current amount of material to leave the surface. This
evaporation process is called desorptive evaporation.

For the conditions considered, a deposition of 100 g/m^2^ corresponds to
a depth of 1 mm of liquid. This depth is sufficient to completely cover
many surfaces, such as fabrics. The dividing point between free-surface
evaporation, with the finite constant evaporation rate, and desorptive
evaporation, with a mass-dependent evaporation rate, is 100 g/m^2^. In
our vapor source, *m*~0~ = 100 g/m^2^.

By equating the mass evaporation rate at the transition from
free-surface evaporation to desorption evaporation, the desorptive
evaporation time constant can be estimated. Equating these rates when
the mass deposition is *m*~0~, a relation is obtained specifying the
desorptive evaporation time constant in terms of the mass-deposition,
the agent volatility, and the free-surface evaporation transport rate.
The desorptive evaporation time constant, , is

$\tau\  = \ \frac{\left( m_{0} \right)}{C_{\text{Vol}}\ v_{\text{evap}}}$.

From the volatility of the CWA, the mass transfer rate for free-surface
evaporation, and the mass per unit area at the start of desorptive
evaporation, the time constant for desorptive evaporation is estimated.
From the volatilities of various chemical warfare agents, values for
evaporation time constants, , in minutes and in hours are obtained.
Table 2 illustrates the range of values that apply to CWAs and some
selected toxic industrial compounds. Note that compounds such as
phosgene, which is a gas under standard conditions, are expected to
evaporate from a liquid state in less than a minute, water is expected
to completely evaporate in times of about the order of hours, sulfur
mustard would take days to evaporate, while VX would take years. Recall,
the time constant, , is time for approximately 63% of the current amount
of material to leave the surface. In other words, the amount of material
on the surface decreases by about 63%, every minutes, until the amount
of material remaining becomes negligible (Welty et al., 1984).

## Vapor Generation at the Decontamination Site

As agent desorbs from a contaminated individual, it is mixed into the
passing air and is a secondary source to decontamination personnel who
are standing near the contaminated individual. With agent desorbing at a
rate given by

![](media/image3.pct)

the concentration of agent downwind of a patient can be estimated. The
resulting concentration will depend on how this evaporating mass is
mixed into the air.

## Constant Flow, Uniform Mixing Approximation

A simple conceptual model was used to account for the above mentioned
mixing, in order to evaluate the time-dependent concentration close to
an individual with off-gassing vapor. A separation distance of about 1 m
between contaminated persons was assumed.

Downwind, the evaporating agent is assumed to be uniformly mixed within
a column of air that has a cross-sectional area (*A~w~*) of about
1 m^2^. This ideal situation will never precisely occur, but the vapor
plume may travel over an area of the order of 1 m^2^, and the resulting
time-integrated concentration at a point in this square meter should be
close to the value obtained from a uniform concentration distribution.

An area, *A~P~*, (also equal to about 1 m^2^) of the patient surface is
assumed to be contaminated with 100 g of CWA. For outdoor conditions, a
low wind (or local air flow) speed (*u~W~*) is 1 m/s, or 60 m/min (NOAO,
2002; NCDC, 1998). The vapor concentration downwind of the contaminated
individual is then

![](media/image4.pct)

Spreading 100 cm^3^ of liquid (about 100 g) over 1 m^2^, corresponds to
a liquid depth of 0.01 cm, which represents the initial deposition of
agent received at the CWA incident site.

The victims are assumed to arrive at the medical facility and the
medical facility personnel to guide them in removing residual source
material (such as clothing and other personal belongings) and then
decontaminate the victims beginning at a time, *t~s~*, (equal to 10
minutes) after the victims are first splashed with agent (Nakajima et
al., 1997; Ogawa et al., 2000; Ohbu et al., 1997; Zhu et al., 1992;
Larson & Odoni, 1981). The exposure that medical personnel will receive
will also begin after this ten minute interval. Agent deposited on these
victims will however begin evaporating as soon as deposition has
occurred. Thus, some of the agent will actually have evaporated during
that ten minutes.

To determine the exposure that medical personnel will experience in
dealing with these victims, integration of concentration begins at time,
*t~s~* and ends once the decontamination process is completed. The
decontamination process may continue for 6 hours, or 360 minutes**,**
quite a conservative assumption for dealing with persons critically
exposed to weapons of mass destruction (SBCCOM, 2002; Lake et al.,
2000). The integrated total potential concentration is given by the
integral

![](media/image5.pct); *τ* in minutes

Integrating over the specified duration gives the final expression for
the integrated total exposure concentration.

![](media/image6.pct)

This total concentration depends on ; if is very small, the agent mainly
evaporates from the skin and clothing before the victims can get to the
medical facility and the potential exposure remains low. If is large,
the amount of agent that evaporates from skin or clothing before the
victims arrive at the facility is small, but the amount that evaporates
during the decontamination process will also be small.

The total concentration as a function of is shown in Figure 3, with the
previously indicated values for m~0~, *A~P~*, *A~W~*, *u~W~*, and
*t~s~*.

## Exposure Modeling

The goal of the hazard and exposure assessment was to develop a maximum
upper bound under worst-case conditions, i.e., if none of the planned
protective measures were implemented and if health care workers worked
for six direct contact hours with contaminated patients who continued to
arrive after an initial well-defined event with a point source (bomb,
terrorist dispersal device, etc). Chemical warfare nerve agents have
been designed to be very toxic and fast acting. When an individual
receives multiple lethal doses of nerve agent, unconsciousness and death
follow within seconds to minutes. We do not anticipate that individuals
who become contaminated with multiple lethal doses of sarin, or other
nerve agent, will self-refer to any medical treatment facility,
requiring even as little as ten minutes travel time. The lethality of
chemical warfare nerve agents will itself limit the amount of
contamination that self-referred victims will bring to the medical
treatment facility.

Many of the parameters involved in the calculation of the total exposure
are actually probabilistic rather than deterministic in character.
Therefore, to model likely exposure patterns, Monte Carlo simulations
were performed using Design Engineering's Crystal Ball 2000
Professional, a macro package for Microsoft Excel (Werckman et al.,
2000). Probability distributions were assigned to specific parameters to
account for both uncertainty and variability in their values. These
simulations were used to derive distributions of the potential exposure
to decontamination staff.

As a first step in developing a probabilistic assessment of potential
exposures, a likely distribution of the secondary "source" term, i.e.
the amount of contaminant on the victims, based on reasonable
assumptions, must be defined.

To determine the mass deposition, a bivariate Gaussian distribution was
first used to describe a uniform density of people within an area of
agent deposition. This distribution represents a radial situation, where
the greatest potential for a significant amount of contamination would
exist at the center. As the distance from the center increases, the
likelihood of receiving significant contamination decreases. This
arrangement means that more and more people will receive lower and lower
deposition of agent. The final distribution results in approximately
20-30% of victims being significantly contaminated. Specifically, the
standard deviation () was chosen such that 1 of every 4 or 5 persons
becomes contaminated with a significant amount of agent.

The maximum deposition level is established as 100 g/m^2^ (based on the
assumptions previously outlined); one person occupies 1 m^2^ of area.
Single-sided contamination is assumed over 1 m^2^ of clothing/body
surface which means that the amount of contamination per square meter is
the amount of contamination per person. The levels for maximum
deposition and "significant contamination" are based on knowledge of
typical dissemination devices. In this manner, the probability of a
particular mass deposition rate (in g/m^2^) was determined. These
probabilities were then used to generate a frequency distribution for
mass deposition, as shown in Figure 4.

Additional distributions were also used to describe the mass deposition.
First, ranking from a Chi-Square test was employed to determine an
appropriate fit to the above frequency distribution. The
"goodness-of-fit" was then evaluated from the results of
Kolmogorov-Smirnov and Anderson-Darling tests. The resulting beta
distribution (pictured in Figure 5) appropriately places the highest
probability with the range of lower mass deposition of agent.

As an alternative, a triangular distribution was also used to represent
mass deposition, with a maximum value of 100 g of agent and a likeliest
value of 10 g.

The evaporation transfer rate (*~evap~*) value of 0.1 m/min, which was
used in the analysis presented in the earlier sections, was derived
based on the transport of mass via molecular diffusion in air. In
reality, evaporation is a process controlled not only by molecular
diffusion, but by various additional macroscopic factors such as local
air flows, temperature differences between the contaminated individual
and the surrounding air, and proximity of other individuals (Bjorn &
Nielsen, 1996; Bjorn & Nielsen, 2002; Brohus, 1997; Fan, 1995; Chen &
Xu, 1998; Yokoyama et al., 2002). Since these factors would increase the
transfer rate of mass, the fixed value employed in the deterministic
analysis presented earlier, corresponds to a conservative approach.
Therefore, subsequent simulations incorporated the variability and
uncertainty in transfer values by assigning a probability distribution
to the evaporation rate with the value 0.1 m/min as a lower bound.

Distributions were also chosen to represent other parameters as well.
The exposed surface area of the patient (*A~p~*) is assumed to be
one-half of the total body surface area. The normal distribution used to
describe average body surface area (with mean of 2 m^2^) is based on the
EPA's Exposure Factors Handbook (USEPA, 1997). This distribution
accounts for the variability in body surface area due to age, gender,
and race. A normal distribution was also used to represent the wind (or
air flow) velocity (*u~W~*) where the mean is 60 m/min (Karayannis et
al., 1997). This is an approximation of the hypergeometric distribution
(Ayyub & McCuen, 2002) typically associated with ambient wind speeds
(NOAO, 2002; NCDC, 1998).

The lag time from the initial dissemination of agent to the arrival time
of the patient at the medical facility is also variable. A normal
distribution about a mean of 10 minutes was used initially. Ambulance
arrival times can be also be represented by an exponential distribution
(Ayyub & McCuen, 2002; Zhu et al., 1992; Larson & Odoni, 1981) so this
assumption was also incorporated in a set of simulations.

The column of air into which the agent is mixed (*A~w~*) is defined as
1 m^2^ and was treated as a fixed value. The volatility of sarin
(*C~vol~*) was also held constant during the Monte Carlo runs. The
6-hour length of the decontamination process is based on the steps in
the decontamination procedure and was held at this value as a
conservative estimate (Hurst, 1997; Brockman, 1998; Cox, 1994; Raber et
al., 2001).

Monte Carlo simulations were then performed using the above defined
parameters with the maximum number of trials set to 25,000. The
percentiles and total concentration forecast, resulting from mass
deposition that is represented by the beta distribution is shown in
Table 4 and Figure 6.

Alternatively, a triangular distribution of mass deposition was used in
another Monte Carlo simulation with all other parameters identical to
the previous simulation. As mentioned earlier, the triangular
distribution was arranged with a maximum value of 100 g of agent and a
likeliest value of 10 g. The results of this simulation are presented in
Table 5 and Figure 7.

According to the above simulation results, medical personnel in level C
PPE with a respiration protection factor of 1,000 working for 6 hours
(i.e. length of the decontamination process) would receive a dose
significantly less than the NIOSH CBRNE SCBA standard of 2.1 mg-min/m^3^
(NIOSH, 2001). The results of both simulations show that less than
2%[^1] of healthcare workers would be exposed to levels of sarin that
could not be protected against with level C PPE, even if victims'
clothing remained as an ongoing source of contamination. As previously
mentioned, several runs were used to compare different distributions for
parameters such as evaporation rate and lag time. When more realistic
distributions for evaporation transfer rate are incorporated, this
percentage is reduced further, as shown in Table 6 and Figure 8.

As previously stated, approximately 80% of the contamination resides on
victims' clothing which leads to the recommended decontamination process
that requires disrobing as a first step. In order to illustrate the
significant reduction in exposure that results from the immediate
disrobing of contaminated patients, a final Monte Carlo simulation was
assembled. A triangular distribution was again used to describe the
deposited mass, but the exposed surface area was reduced from 50% to
20%. The percentiles shown in Table 7 and corresponding results in
Figure 9 show that the potential exposure to healthcare workers has been
significantly reduced. In the prior conservative model, i.e. the
worst-cast scenario, less than 2% of the Monte Carlo trials resulted in
an exposure that could not be protected against with level C PPE. This
final simulation demonstrates that when the contaminated clothing is
immediately removed upon arrival at the health care facility, the level
of sarin exposure to a healthcare worker would be negligible.

## Discussion of Modeling Results

The above modeling outcomes suggest several items with important
operational implications. First, as expected, the major predictors of
exposure to healthcare personnel are time since exposure in "hot" zone
and the amount of material remaining on the person. For all agents
except sarin, doses delivered through airborne routes (i.e.,
off-gassing), five minutes *after leaving the scene should be negligible
if clothing was removed* (see Table 2)*.* Recognition of an event,
identification of transportation means, and transportation to a
healthcare facility are not expected to take less than five minutes
under even the most ideal circumstances. Only agents with a vapor
pressure similar to water, such as sarin, might still volatilize enough
from the skin and clothing to place healthcare workers at risk, even
after relatively short periods of time (Mioduszewski et al., 1998).
Thus, source material needs to be removed from the victim as soon as
possible, and the source material must be safely stored away from
healthcare workers.

In mass casualty settings, many survivors have appeared in healthcare
facilities through non-standard routes, bypassing the planned
transportation pathways. It is likely that "contaminated" patients,
whether minimally exposed and healthy, or heavily exposed and acutely
ill, will arrive in healthcare settings without clothing removal.
Facilities must plan for such unexpected arrivals.

Second, as clothing is likely to contain a large percentage of the
delivered dose, the clothing is the next most important predictor of
dose. If clothing is removed in the "hot" or "warm" zone, exposures are
obviously substantially lower. If not, clothing actually functions as a
secondary source in the decontamination zone and requires an explicit
exposure control strategy. This possibility requires a focus on clothing
removal and control immediately upon arrival at the decontamination
scene (for example, through the preparation of explicit instructions and
through planning an efficient delivery system). Some personal items,
such as wallets, photographs, plastic glasses frames, etc. may absorb
agents in a way that prevent decontamination. Valuables, such as wedding
rings and precious stones, can likely be contaminated. Facilities must
plan to distinguish between decontaminable and discardable belongings.
Clothing must be stored in controlled settings away from people during
activities. Plastic bags (3 or 6 ml) are likely to provide adequate
protection for transport to storage but should not be relied upon for
containment of agent. Therefore there must be a centralized HAZMAT
storage container available near (but at a safe distance from) the
actual decontamination and triage area, in which to deposit all bagged
materials. Finally, formal removal must follow strict hazardous waste
operations protocols.

Third, during the actual decontamination, both showering and effluent
runoff may function as secondary sources of exposure; both may require
control. EPA mandates planning for runoff control. Containment, rather
than relying on evaporation of the CWA, is necessary if real
contamination is expected. Similarly, if serious contamination is
expected, some approach to ventilation of the decontamination facility
is necessary. Where such facilities are permanent, built into a hospital
infrastructure, great care must be taken to assure that no
cross-contamination allows entry into other parts of the facility,
through drift from positive pressure, re-entrainment into air intakes,
or planned recirculation (possible if decontamination areas are built
into hallways). Portable units, including tents, have substantial
advantages for terrorist events using weapons of mass destruction as
such cross-contamination is less likely. A schematic of the recommended
approach to patient receipt, clothing removal, decontamination and
triage is shown in **Figure 10.**

Understanding exposures requires the use of "near field" microscale
models, as the majority of current regulatory models (for atmospheric
dispersion modeling) are valid only for very simple configurations of
source and receptor settings (OFCM, 1999; Bacon, 2000; Fernando et al.,
2001; Georgopoulos, 2002; ORD, 2002; Kukkonen et al., 2001). There are
no existing simple/regulatory models valid down to the 1 m scale in a
realistic setting, i.e. near buildings, with moving vehicles, people,
etc.. In fact, understanding the dynamic patterns of sources and
resulting concentrations in complex outdoor and indoor
microenvironmental settings requires Computational Fluid Dynamics (CFD)
techniques that account for local mechanical and convection effects on
the transport and deposition of contaminants (Bennett et al., 2000;
Winters & Chenoweth, 2002; Hayashi et al., 2002). Not only site
operations planning and layout affects exposures, but also human
movement and posture will affect contaminant transport patterns. For
example, the "human plume" resulting from a thermal gradient producing
convective turbulence, would likely enhance the release agent and move
it along the body at about 50 L/s with a vertical speed of about 0.25
m/s (Settles et al., 1996; Settles et al., 2001) for a standing person.

So, several aspects of local site layout affect predicted exposures.
Orientation of the patient, i.e., lying vs standing, affects
concentrations in that upright patients release concentrations along a
longer pathway, with potentially higher concentrations to healthcare
workers. The closeness of patients to each other and competing up- and
down-drafts caused by convection patterns will considerably influence
exposure. The chaotic nature of emergencies would most likely prevent
the control of exposure via proper placement of stretchers and patients.

Monte Carlo simulations based on conservative assumptions about the
amount of mass deposited to the victims' bodies, suggest that the
probability of levels of exposure exceeding the capability of level C
PPE would be less than 2%.

[]{#__RefHeading___Toc38171597 .anchor}Table 2. Summary of the
properties of chemical warfare agents (CWA) and selected toxic
industrial chemicals. The volatility and time constant () for the
evaporation process determine how quickly an agent will evaporate upon
dissemination. The concentration of the CWA that is lethal to 50% of the
population after a one-minute exposure (LCt~50~) is provided as well as
the dose that is lethal to 50% of the population (LD~50~). The 100 g
deposition of agent is an upper bound release from typical dissemination
devices. The larger number of lethal doses per 100 g of CWA indicate
increased potential harm to those exposed.

  ---------- ----------- ------------- ----------- ---------- ---------- ------------- ---------- -----------------
  **Agent    **Agent**   ***C~vol~*    **MW        **τ\*      **τ \*     **LCt~50~\    **LD~50~   **LD~50~/100g**
  Symbol**               (25°C)        (g/mol)**   (min)**    (hr)**     (mg •         (mg)**     
                         (mg/m^3^)**                                     min)/m^3^**              

  Cl         Chlorine    25000000      71          0.04       0.000667   19000                    

  CG         Phosgene    10000000      99          0.1        0.001667   3200                     

  AC         Hydrogen    1080000       27          0.925926   0.015432   2000                     
             Cyanide                                                                              

  \--        Water       22900         18          43.66812   0.727802                            

  GB         Sarin       22000         140         45.45455   0.757576   35            1700       59

  GD         Soman       3900          182         256.4103   4.273504   35            350        286

  HD         Sulfur      920           159         1086.957   18.11594   1000          1400       71
             Mustard                                                                              

  GA         Tabun       610           162         1639.344   27.3224    70            1500       67

  GF         GF          581           180         1721.17    28.68617   35            350        286

  VX         VX          10            267         100000     1666.667   15            5          20000
  ---------- ----------- ------------- ----------- ---------- ---------- ------------- ---------- -----------------

\*![](media/image7.pct)

[]{#_Ref36019265 .anchor}

Table 3. Number of lethal doses resulting from a 100 g deposition of a
chemical warfare agent. The 100 g deposition of agent is an upper bound
release from typical dissemination devices. The larger number of lethal
doses per 100 g of CWA indicate increased potential harm to those
exposed.

  ----------- ------------------- ----------------- ------------------------
  **Agent**   **Name**            **LD~50~ (mg)**   **LD~50~/100g of agent**

  GB          Sarin               1700              59

  GD          Soman               350               286

  HD          Sulfur Mustard      1400              71

  GA          Tabun               1500              67

  GF          GF                  350               286

  VX          VX                  5                 20000
  ----------- ------------------- ----------------- ------------------------

[]{#__RefHeading___Toc38171599 .anchor}Table 4. Percentiles of the Monte
Carlo forecasted total integrated exposure concentration (*CT*) of
sarin. The concentration is the predicted exposure of medical personnel
as victims present themselves to the medical treatment facility for
decontamination and triage. The Monte Carlo trials represent the initial
mass deposition (*m~o~*) with an appropriate beta distribution (shown in
Figure 4).

  --------------------------------- -------------------------------------
  **Percentile**                    **CT\
                                    mg-min/m^3^**

  0%                                0.00

  5%                                0.00

  10%                               0.00

  15%                               0.00

  20%                               0.10

  25%                               1.11

  30%                               5.02

  35%                               13.44

  40%                               27.44

  45%                               47.18

  50%                               71.65

  55%                               101.57

  60%                               138.19

  65%                               178.36

  70%                               225.89

  75%                               283.86

  80%                               353.97

  85%                               445.37

  90%                               576.87

  95%                               831.21

  100%                              5,953.16
  --------------------------------- -------------------------------------

[]{#__RefHeading___Toc38171600 .anchor}Table 5. Percentiles of the Monte
Carlo forecasted total integrated exposure concentration (*CT*) of
sarin. The concentration is the predicted exposure of medical personnel
as victims present themselves to the medical treatment facility for
decontamination and triage. The Monte Carlo trials represent the initial
mass deposition (*m~o~*) with a triangular distribution with a maximum
value of 100 g and a likeliest value of 10 g.

  --------------------------------- -------------------------------------
  **Percentile**                    **CT\
                                    mg-min/m^3^**

  0%                                0.00

  5%                                2.70

  10%                               9.29

  15%                               18.43

  20%                               30.32

  25%                               44.46

  30%                               60.09

  35%                               78.12

  40%                               98.51

  45%                               120.26

  50%                               143.35

  55%                               168.78

  60%                               199.13

  65%                               233.76

  70%                               272.44

  75%                               321.49

  80%                               382.47

  85%                               459.27

  90%                               592.98

  95%                               819.10

  100%                              3,768.36
  --------------------------------- -------------------------------------

[]{#__RefHeading___Toc38171601 .anchor}Table 6. Percentiles of the Monte
Carlo forecasted total integrated exposure concentration (*CT*) of
sarin. The concentration is the predicted exposure of medical personnel
as victims present themselves to the medical treatment facility for
decontamination and triage. The Monte Carlo trials represent the initial
mass deposition (*m~o~*) with a triangular distribution with a maximum
value of 100 g and a likeliest value of 10 g. The evaporation rate of
sarin (*~evap~*) is described by an exponential distribution as a
realistic estimate of the desorptive evaporation rate.

  --------------------------------- -------------------------------------
  **Percentile**                    **CT\
                                    mg-min/m^3^**

  0%                                0.00

  5%                                1.56

  10%                               9.04

  15%                               20.97

  20%                               35.20

  25%                               51.72

  30%                               68.90

  35%                               87.81

  40%                               108.73

  45%                               132.05

  50%                               157.36

  55%                               185.97

  60%                               217.81

  65%                               252.05

  70%                               292.62

  75%                               345.77

  80%                               412.97

  85%                               507.40

  90%                               651.13

  95%                               950.04

  100%                              20,813.34
  --------------------------------- -------------------------------------

[]{#__RefHeading___Toc38171602 .anchor}Table 7. Percentiles of the Monte
Carlo forecasted total integrated exposure concentration (*CT*) of
sarin. The concentration is the predicted exposure of medical personnel
as victims present themselves to the medical treatment facility for
decontamination and triage. The Monte Carlo trials represent the initial
mass deposition (*m~o~*) with a triangular distribution with a maximum
value of 100 g and a likeliest value of 10 g. In this scenario the
contaminated body surface area is assumed to be 20%, which represents
the potential exposure to healthcare workers when victims immediately
disrobe.

  --------------------------------- -------------------------------------
  **Percentile**                    **CT\
                                    mg-min/m^3^**

  0%                                0.00

  5%                                0.53

  10%                               1.98

  15%                               4.03

  20%                               6.48

  25%                               9.37

  30%                               12.65

  35%                               16.40

  40%                               20.55

  45%                               25.07

  50%                               29.99

  55%                               35.30

  60%                               41.34

  65%                               48.00

  70%                               56.05

  75%                               65.45

  80%                               77.21

  85%                               93.05

  90%                               117.48

  95%                               162.09

  100%                              935.75
  --------------------------------- -------------------------------------

![](media/image8.jpeg){width="5.99375in" height="2.5993055555555555in"}

[]{#__RefHeading___Toc38171604 .anchor}Figure 2. Schematic depiction of
free-surface evaporation process of a liquid agent. The evaporative flux
is the rate of change of surface-deposited mass with time. It depends on
the volatility and an evaporation rate of the liquid.

![](media/image9.jpeg){width="5.9944444444444445in"
height="3.2354166666666666in"}

[]{#__RefHeading___Toc38171605 .anchor}Figure 3. Total integrated
exposure concentration (*CT*) of CWA for medical personnel as a function
of the evaporation time constant (). The time interval begins after a
10-minute lag time during which some material has evaporated; the
evaporation will continue as decontamination proceeds. The
time-integrated exposure concentration is then the sum of exposure
concentration as contaminated patients file past the medical personnel.
This concentration is dependent upon the evaporation time constant ()
which is the characteristic time for volatilization of the liquid agent.
When is small the majority of the agent evaporates prior to arrival at
the medical treatment facility; for agents with a larger , little agent
will evaporate not only during transport to the medical facility, but
throughout the decontamination process.

![](media/image10.jpeg){width="5.998611111111111in" height="4.10625in"}

[]{#__RefHeading___Toc38171606 .anchor}Figure 4. Frequency density of
initial mass deposition (*m~o~*) of sarin which describes the frequency
with which victims will be contaminated with a specific amount of sarin.
This density is based on the assumption of a two-dimensional Gaussian
distribution that represents a uniform density of people and the likely
mass deposition of the CWA as the radial distance increases from the
dissemination device.

![](media/image11.jpeg){width="5.995138888888889in" height="3.725in"}

[]{#__RefHeading___Toc38171607 .anchor}Figure 5. Beta distribution with
=0.52 and =1.20 representing the initial mass deposition (*m~o~*) of
sarin. The distribution was chosen as an appropriate fit corresponding
to the frequency density shown in Figure 3 and is used in subsequent
Monte Carlo simulations to determine the total exposure to sarin
received by medical personnel.

![](media/image12.jpeg){width="5.991666666666666in"
height="2.9902777777777776in"}

[]{#__RefHeading___Toc38171608 .anchor}Figure 6. Monte Carlo forecast of
total integrated exposure concentration (*CT*) of sarin when the mass
deposition (*m~o~*) is represented by the beta distribution presented in
Figure 4. The time-integrated exposure concentration is then the sum of
exposure concentration as contaminated patients file past the medical
personnel. The integration begins after a 10-minute lag time which
represents transport time to the facility; the integration is stopped
when the decontamination process ends.

![](media/image13.jpeg){width="5.989583333333333in"
height="2.9368055555555554in"}

[]{#__RefHeading___Toc38171609 .anchor}Figure 7. Monte Carlo forecast of
total integrated exposure concentration (*CT*) of sarin when the mass
deposition (*m~o~*) is represented by a triangular distribution with a
maximum value of 100 g and a likeliest value of 10 g. The
time-integrated exposure concentration is then the sum of exposure
concentration as contaminated patients file past the medical personnel.
The integration begins after a 10-minute lag time which represents
transport time to the facility; the integration is stopped when the
decontamination process ends.

![](media/image14.jpeg){width="5.998611111111111in"
height="3.1597222222222223in"}

[]{#__RefHeading___Toc38171610 .anchor}Figure 8. Monte Carlo forecast of
total integrated exposure concentration (*CT*) of sarin when the
evaporation rate of sarin (*~evap~*) is described by an exponential
distribution as a realistic estimate of the desorptive evaporate rate.
The mass deposition (*m~o~*) is represented by a triangular distribution
with a maximum value of 100 g and a likeliest value of 10 g. The
time-integrated exposure concentration is then the sum of exposure
concentration as contaminated patients file past the medical personnel.
The integration begins after a 10-minute lag time which represents
transport time to the facility; the integration is stopped when the
decontamination process ends.

![](media/image15.jpeg){width="5.999305555555556in"
height="3.270138888888889in"}

[]{#__RefHeading___Toc38171611 .anchor}Figure 9. Monte Carlo forecast of
total integrated exposure concentration (*CT*) of sarin when the mass
deposition (*m~o~*) is represented by a triangular distribution with a
maximum value of 100 g and a likeliest value of 10 g. The
time-integrated exposure concentration is then the sum of exposure
concentration as contaminated patients file past the medical personnel.
The integration begins after a 10-minute lag time which represents
transport time to the facility; the integration is stopped when the
decontamination process ends. In this scenario the contaminated body
surface area is assumed to be 20%, which represents the potential
exposure to healthcare workers when victims immediately disrobe.

![](media/image16.jpeg){width="5.592361111111111in"
height="7.752083333333333in"}

[]{#__RefHeading___Toc38171612 .anchor}Figure 10. Emergency response
steps for survivors of chemical attack seeking medical attention at
hospital ER. The "hot" zone represents the site of the CWA release,
while the "cold" zone is the area with no expected contamination. The
"warm" zone denotes areas where contaminated victims present themselves
for decontamination. As the contaminated patients arrive at the medical
treatment facility, they become sources of contamination for the medical
personnel who must adhere to the recommended steps to minimize exposure.
Health care workers in each zone also limit exposure when covered by the
appropriate level of personal protective equipment.

# TRAINING NEEDS

*[Does OSHA require level B personal protective equipment for hospital
workers?]{.underline}*

The Hazardous Wastes Operations and Emergency Response (HAZWOPER)
Standard (29 CFR 1910.120(q)(3)(iv)) applies to employees under the site
specific Incident Command System who are engaged in emergency response
with the intent of handling or controlling the release. For these
employees, possible close approach to the point of release and exposure
to inhalation hazards is anticipated, and for them, the highest level of
respiratory protection is required. However, some facilities have
interpreted this to mean that all hospitals involved in chemical
incidents, especially involving WMD agents, must be prepared for
responses using level B PPE.

By contrast, hospital personnel expected to decontaminate a chemically
contaminated patient who had been involved in a release of a hazardous
substance are removed from the site of the emergency and the point of
release. Such personnel do not need to be trained or equipped as would a
person participating on HAZMAT team. Their potential exposures would
result from proximity to or contact with a patient who may have been
chemically contaminated. Such hospital personnel would need be trained
to the first responder operations level (1910.120(q)(6)(ii))(Fairfax,
1999; Fairfax, 1992). Health care workers\' primary activities in such a
situation would be clinical care and the resultant decontamination.
Their exposure to inhalation and dermal hazards is likely to be
substantially lower than those actively participating at the site of
chemical release. OSHA cannot define how contaminated patient(s) will
be, who are presented at hospitals post-release, and whether level A, B,
or C are the most appropriate level of protection (Fairfax, 2002a). OSHA
does not assume that level B or A (self-contained breathing apparatus)
are necessary (Fairfax, 2002b) although this is one way of addressing a
hazard assessment. On the other hand, on-site responding personnel at
active release sites with the potential for exposure from ongoing
release of agents, are at much higher risk of adverse effects than
in-hospital staff. OSHA does require hospitals to conduct a risk
assessment that identifies types and levels of exposures that employees
can reasonably anticipate (Fairfax, 2002a). If personnel are exposed to
residual off-gassing from patients rather than to an active chemical
agent dispersal device, the risk assessment should focus on the actual
likely exposures.

*[Is level C adequate for "self-referrals"?]{.underline}*

Where the types of substances are known and worst-case scenarios can be
constructed, likely exposures can be estimated. Scrutiny of evaporation
rates suggests that only sarin, or other agents with vapor pressures
similar to water, could still generate hazardous vapor exposures during
decontamination. For sarin, levels of 100 g of agent on individuals are
likely to generate doses well above the lethal concentration for 50% of
the population (IOM, 1997). Such levels are incapacitating, so that
patients with such concentrations can arrive only after passive
transport. Such patients must be brought either by ambulance, where they
will likely have been decontaminated, or by private vehicle, via which
only limited numbers (far less than the 50% mentioned above) would
actually appear. So, exposures to hospital personnel would remain well
below the threshold required for level B.

# MEDICAL SURVEILLANCE

Workers in hazardous operations have undergone medical surveillance
examinations since several environmental disasters in the early 1980s.
The practices evolved from an early document (NIOSH/OSHA/USCG/EPA, 1985)
and were codified in a 1986 OSHA standard, HAZWOPER standard (Melius,
1986). Practices have evolved since then and have been codified for a
program to manage demilitarization of chemical warfare agents, namely
the Chemical Stockpile Emergency Preparedness Program (CSEPP) (FEMA,
2003). Medical programs for hazardous materials handling serve two
purposes: (a) fitness to work and (b) adverse health effect monitoring
(Melius, 1986; Gochfeld & Favata, 1990; Favata & Gochfeld, 1989; Udasin
et al., 1991).

[]{.mark}

Working in chemical protective suits with powered air-purifying
respirators (PAPRs) generates the usual consideration of work
capabilities. Three specific concerns arise: first, individuals working
in chemical protective clothing appear to be at increased risk of heat
illness, especially in hot climates. Physical conditioning and
acclimatization appear to have few documented benefits (McLellan & Frim,
1994) and are not likely to serve as a useful element to a hospital
response program. Hospitals should address this with monitoring and
control programs (Tan & Fitzgerald, 2002) such as contained in CSEPP.
Second, chronic diseases associated with impaired autonomic sensitivity
warrant scrutiny (Beckett et al., 1986). Third, PAPRs, by themselves,
really have no physiological contraindications, as there is no added
resistance such as described for negative pressure respirators (Hodous
et al., 1986). However, discomfort from air streams passing the face may
be severe enough to prevent effective work. This represents a
psychological response that, together with claustrophobia, may preclude
participation in a program. The weight of equipment is negligible, so
that the cardiovascular concerns arising with the use of self-contained
breathing apparatus are insignificant for level C PPE. In general,
therefore, neither pulmonary nor cardiac contraindications should
preclude wearing level C PPE, but heat illness monitoring programs are
necessary.

Equally important is surveillance of health endpoints. Routine screening
for pulmonary, dermal, neurological, and gastrointestinal effects
represents important baseline documentation. Routine blood testing for
such programs generally aims to define hematologic and hepatic
functioning. Body-mass index, as a major contributor to liver test
abnormalities, must be recorded. Biological monitoring for the many
potential agents is impossible. After the fact, documentation of
exposure, particularly for individuals who develop symptoms, should be
an integral part of the incident resolution. For many, serial laboratory
determinations, such as used for the documentation of cholinesterase
inhibition and recovery (Coye et al., 1987) are appropriate. Comparison
of levels obtained immediately after exposure with those obtained later
may serve to document markers of exposure or effect with subsequent
resolution. In general, as sequential determination and comparison with
the initial levels provides evidence of changes in body burden or
recovery, serum banking is unnecessary.

# CONCLUSION

Based on considerations discussed in the previous section, the authors
believe level C PPE is possible under well-defined conditions and
assumptions that pertain to hospitals. Still, use of level C requires
prior planning and protocols at the facility and the following
constraints:

## Local: facility level

-   Staff involved in the response to such events must have a clear
    understanding of the hazards of agents, of the broad syndromes
    associated with exposure, and of the treatment implications (pocket
    cards, emergency responders' guides). They must have training in PPE
    and the local plans.

-   Local plans must focus on site layout and operational strategies
    integrated with the local community. A decontamination plan requires
    site layout that identifies a receiving area before the hospital
    that focuses on rapid disrobing and decontamination, and local
    storage of bagged source material**.** Prior consideration of the
    location of staging and holding areas, their relationship to the
    emergency room/ambulatory care access site, and the intricacies of
    security and crowd control are essential to the success of such
    decontamination. Clear and simple instructions by megaphone, to
    individuals or groups, are essential and should happen quickly.

-   Facilities must provide fans for air movement across disrobing /
    holding areas and in decontamination tents.

-   Clothing, etc. can be transported in plastic bags to the designated
    HAZMAT container, but handling this material will require level B or
    higher PPE (done by national operations).

-   Bleach decontamination of corpses is likely to allow the deceased to
    be handled in a normal manner.

## Local: Area Emergency Planning Committees

It is essential that local committees agree on protocols that require
the removal of clothing prior to transport to healthcare facilities.
This exposure reduction will benefit emergency medical technicians and
ambulance drivers and the receiving healthcare workers. This is the
single most important control strategy. All responders must be trained
to recognize that prompt removal of contaminated clothing is essential
once victims have been removed from the site of ongoing release and
before transport to a healthcare facility.

## National Level

EMT triage algorithms should exist for the clinical presentations, to be
used by front-line workers. This is crucial for rapidly-acting nerve
gases and chemical asphyxiants like cyanide. In general, other agents
require decontamination and supportive treatment but do not clearly
benefit from additional pharmacologically justified treatment. Once
detection equipment exists that is sensitive and reliable enough to
guide exposure assessment and management, such front-line algorithms may
be less important. First responders should distinguish basic syndromes
(hypercholinergic, chemical anoxia, mucosal irritants) and relay
critical information on likely agents to the receiving healthcare
facility.

# REFERENCES {#references .unnumbered}

# APPENDIX: ACRONYMS AND SYMBOLS {#appendix-acronyms-and-symbols .unnumbered}

## List of Acronyms

ATSDR Agency for Toxic Substances and Disease Registry

CBRNE Chemical Biological, Radiological Nuclear and Explosive Materials

CSEPP Chemical Stockpile Emergency Preparedness Program

CWA Chemical Warfare Agent

D2PC U.S. Army Personal Computer Program for Chemical Hazard Prediction

DOD Department of Defense

EMT Emergency Medical Technician

EOHSI Environmental and Occupational Health Sciences Institute

HAZWOPER Hazardous Wastes Operations and Emergency Response

JCAHO Joint Commission on Accreditation of Health Care Facilities

MMRT Metropolitan Medical Response Team

NIOSH National Institute of Occupational Safety and Health

NIST National Institute for Standards & Technology

OSHA Occupational Safety and Health Administration

PPE Personal Protective Equipment

SBCCOM US Army Soldier and Biological Chemical Command

SCBA Self Contained Breathing Apparatus

USAF United States Air Force

VHA Veterans Health Administration

## List of Symbols

$\frac{\text{dm}}{\text{dt}}$ evaporative flux of chemical agent
\[mg/m^2^-min\]

*C~vol~* volatility of chemical agent \[mg/m^3^\]

*~evap~* evaporation transfer rate \[m/min\]

*m~o~* mass deposition \[g/m^2^\]

time constant of evaporation process \[min\]

*A~w~* area of column of air \[m^2^\]

*A~p~* surface area of patient contaminated with agent \[m^2^\]

*u~W~* wind velocity \[m/min\]

*C* vapor concentration downwind of contaminated patient \[mg/m^3^\]

*CT* integrated exposure concentration \[mg-min/m^3^\]

*t~s~* start time for integration \[min\]

*LD~50~* dose lethal to 50% of exposed population \[mg\]

*LCt~50\ ~*concentration lethal to 50% of exposed population after 1min
exposure \[mg-min/m^3^\]

[^1]: 2% is a very conservative estimate because removal of clothing and
    decontamination should occur immediately (as subsequently
    discussed).