EPA 600/R-11/051 | June 2011 | www.epa.gov/ord

Office of Research and DevelopmentNational Homeland Security Research Center

TECHNOLOGY EVALUATION REPORT

Decontamination of Sulfur Mustard and Thickened Sulfur Mustard Using Chlorine Dioxide Fumigation

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EPA 600-R-11-051 June 2011

Evaluation Report

Decontamination of Sulfur Mustard and Thickened Sulfur Mustard Using Chlorine Dioxide Fumigation

NATIONAL HOMELAND SECURITY RESEARCH CENTER OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711

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Disclaimer

The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development’s National Homeland Security Research Center, funded and managed this investigation through a blanket purchase agreement under U.S. General Services Administration contract number GS23F0011L-3 with Battelle Memorial Institute. This report has been peer and administratively reviewed and has been approved for publication as an EPA document. Note that approval does not signify that the contents necessarily reflect the views of EPA. This report includes photographs of commercially available products. The photographs are included for purposes of illustration only. No official endorsement should be inferred. EPA does not endorse the purchase or sale of any commercial products or services.

Questions concerning this document or its application should be addressed to:

Lukas Oudejans, Ph.D.

National Homeland Security Research Center Office of Research and Development U.S. Environmental Protection Agency Mail Code E343-06 Research Triangle Park, NC 27711 (919) 541-2973 oudejans.lukas@epa.gov

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Foreword

Following the events of September 11, 2001, U.S. EPA’s mission was expanded to address critical needs related to homeland security. Presidential directives identify EPA as the primary federal agency responsible for the country’s water supplies and for decontamination following a chemical, biological, and/or radiological (CBR) attack. As part of this expanded mission, the National Homeland Security Research Center (NHSRC) was established to conduct research and deliver products that improve EPA’s capability to carry out its homeland security responsibilities. One specific focus area of our research is on decontamination methods and technologies that can be used in the recovery efforts resulting from a CBR contamination event. In recovering from an event and decontaminating the area, it is critical to identify and implement appropriate decontamination technologies. The selection and optimal operation of an appropriate technology depends on many factors including the type of contaminant and associated building materials, temperature, relative humidity, fumigant concentration, and fumigation time. This document provides information on how one fumigant-based technology performed in the decontamination of one chemical warfare agent (CWA) deposited on an interior industrial building material at various operational conditions. These results, coupled with additional information in separate NHSRC publications (available at www.epa.gov/nhsrc), can be used to determine whether a particular decontamination technology can be effective in a given scenario. With these factors in consideration, the best technology or combination of technologies can be chosen that meets the cleanup, cost and time goals for a particular decontamination scenario. NHSRC has made this publication available to assist the response community to prepare for and recover from disasters involving chemical contamination. This research is intended to move EPA one step closer to achieving its homeland security goals and its overall mission of protecting human health and the environment while providing sustainable solutions to our environmental problems.

Jonathan Herrmann, Director National Homeland Security Research Center

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Acknowledgments

The U.S. EPA’s National Homeland Security Research Center (NHSRC) acknowledges the following organizations and individuals for their support in the development of this report, whether in contributing to the research or providing a peer review. U.S. Environmental Protection Agency

Leroy Mickelsen, (Office of Emergency Management, National Decontamination Team) Jeanelle Martinez (Office of Emergency Management, National Decontamination Team) Sang Don Lee (NHSRC, Decontamination and Consequence Management Division)

Battelle Memorial Institute

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Executive Summary

The U.S. Environmental Protection Agency’s (EPA’s) National Homeland Security Research Center (NHSRC) recently evaluated chlorine dioxide (ClO2) fumigation for the decontamination of chemical agents on indoor material coupons (excised samples).(1) Results on the effectiveness of ClO2, both as a fumigant and as a liquid were reported for sarin, thickened soman , and VX but not for sulfur mustard (HD). This investigation evaluated the efficacy of ClO2 vapor in decontaminating sulfur mustard (HD) and thickened sulfur mustard (THD) on galvanized metal coupons. Galvanized metal was selected for its wide application in heating, ventilation, and air conditioning systems. The technical objective was to investigate the effects of fumigant concentration and contact time on the decontamination efficacy. A test chamber was designed to perform the ClO2 fumigation as ClO2was generated from a Sabre Technical Services (Sabre) ClO2 generator. Neat HD and THD were applied to galvanized metal coupons that were then exposed to ClO2 fumigation for various contact times under specified environmental conditions. Following exposure, HD or THD was extracted to quantitatively determine the remaining concentration of THD and HD by using gas chromatography/mass spectrometry analysis. When compared to the spike controls (agent directly spiked into extraction solvent), the amount of HD and THD for the positive controls (HD and THD applied to galvanized metal coupons but not decontaminated) was >90% of spiked control amounts after 1 hour to <50% of spiked control amounts after 7 hours. Exposure to 80% relative humidity and 3000 parts per million ClO2 vapor over the same time period yielded results similar to the results obtained for the positive controls. Overall, decontamination of HD and THD from galvanized metal with ClO2 yielded poor decontamination efficacies (37% or less). Therefore, ClO2 fumigation as described in these tests should not be considered as an effective decontamination method. In addition to HD, internal standard, and surrogate recovery compound, the gas chromatograms from each decontaminated sample showed that there were three additional peaks observed in the chromatograms of samples that underwent a qualitative assessment; no additional peaks were observed in the controls or blanks (samples with no HD or THD applied). For HD, all samples exposed to ClO2 vapor for 1, 2 or 7 hr exhibited three defined peaks in their chromatograms. The same peaks were observed in the chromatogram of THD, but only for the 2 and 7 hr exposure times. Two of the peaks were identified as bis(beta-chloroethyl) sulfone and bis(beta-chloroethyl) sulfoxide by using mass spectrometric libraries, while the third mass spectrum did not match consistently with compounds in the databases. Like HD, the bis(beta-chloroethyl) sulfone oxidation byproduct is considered to be a vesicant (blister agent) and is found as a stable byproduct following ClO2 fumigation of HD or THD. Following exposure to ClO2 vapor during the decontamination testing and based on visual observations made immediately after experiments were completed, there was no observable damage to any of the galvanized metal coupons on the timescale of the longest exposure (7 hours).

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Table of Contents Disclaimer ....................................................................................................................................... ii

Foreword ........................................................................................................................................ iii

Acknowledgments.......................................................................................................................... iv

Executive Summary ........................................................................................................................ v

Table of Contents ........................................................................................................................... vi

List of Tables ................................................................................................................................ vii

List of Figures ............................................................................................................................... vii

Acronyms and Abbreviations ...................................................................................................... viii

Unit List ......................................................................................................................................... ix

1. Introduction ......................................................................................................................... 1 1.1 Objectives .........................................................................................................................1 1.2 General approach ..............................................................................................................2 1.3 Test Facilities ....................................................................................................................2

2. Experimental Methods ........................................................................................................ 3 2.1 Chemical Agent ................................................................................................................3 2.2 Test Materials....................................................................................................................3 2.3 Spiking Coupons ...............................................................................................................3 2.4 Decontamination and Control Chambers ..........................................................................4 2.5 Temperature and Relative Humidity .................................................................................5 2.6 Extracting and Quantifying Chemical Agents ..................................................................5 2.7 Measurement of Gaseous ClO2 .........................................................................................6 2.8 Experimental Design .........................................................................................................7 2.9 Calculation of Decontamination Efficacy .........................................................................8 2.10 Decontamination Byproduct Determination ......................................................................9 2.11 Surface Damage ................................................................................................................9

3. Results and Discussion ..................................................................................................... 10 3.1 Extraction Efficiencies of HD and THD from Galvanized Metal ..................................10 3.2 Decontamination Testing of THD and HD using Chlorine Dioxide ..............................10 3.3 Assessment of Decontamination Byproducts .................................................................12 3.4 Surface Damage ..............................................................................................................13

4. Quality Assurance/Quality Control................................................................................... 14 4.1 Decontamination Testing of THD and HD using Chlorine Dioxide ..............................14

4.1.1 Temperature and Relative Humidity ......................................................... 14 4.1.2 Testing and Analysis ................................................................................. 14

4.2 Performance Evaluation Audit ........................................................................................15 4.3 Technical Systems Audit ................................................................................................16 4.4 Data Quality Audit ..........................................................................................................16

5.0 Summary ........................................................................................................................... 17

6.0 References ......................................................................................................................... 18

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List of Tables Table 1. Parameters used for GC/MS Analysis .............................................................................. 6 Table 2. Test Matrix for ClO2 Decontamination Testing of THD and HD on Galvanized Metal

Coupons (number of replicates for each contact time is shown) ............................................ 7 Table 3. Mean (±SD) Percent Recovery of HD and THD from Samples. .................................... 11 Table 4. Characteristics of Observed Peaks in Decontaminated Samples after 7 Hour Contact

Time. ..................................................................................................................................... 13 Table 5. Mean (±SD) Temperatures (°C) during Testing. ............................................................ 14 Table 6. Mean (±SD) Relative Humidity (%) during Testing. ..................................................... 14 Table 7. Mean (±SD) ClO2 Concentration (ppmv) during Testing. ............................................. 14 Table 8. Mean (±SD) Percent Recovery of the Surrogate Recovery Compound from Samples. . 15 Table 9. Performance Evaluation Audit Results. .......................................................................... 15 List of Figures Figure 1: Test coupons on a wire rack. ........................................................................................... 3 Figure 2: Inoculated coupon. .......................................................................................................... 4 Figure 3: Decontamination chamber connected to Sabre unit within chemical fume hood. .......... 4 Figure 4: Control chamber inside chemical fume hood. ................................................................. 5 Figure 5: Mean (±SD) percent recovery HD and THD ................................................................ 11 Figure 6: Decontamination efficacy of 3000 ppmv ClO2 ............................................................. 12

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Acronyms and Abbreviations CAS no. .................................................................. Chemical Abstracts Service Registry Number CBR .............................................................................. Chemical, Biological, and/or Radiological CWA(s) .................................................................................................. chemical warfare agent(s) DCMD................................................ Decontamination and Consequence Management Division EPA ................................................................................... U.S. Environmental Protection Agency GB ........................................................................................................................................... sarin GC .................................................................................................................... gas chromatograph GC/MS ............................................................................... gas chromatograph/mass spectrometer GD ....................................................................................................................................... soman HD .......................................................................................................................... sulfur mustard HVAC ............................................................................. heating, ventilation and air conditioning IS ........................................................................................................................ internal standard MSD ........................................................................................................... mass selective detector N .................................................................................................................................... Number NHSRC .................................................................. National Homeland Security Research Center PE ............................................................................................................. performance evaluation QA .................................................................................................................... Quality Assurance QC ......................................................................................................................... Quality Control RH ....................................................................................................................... relative humidity SARM ................................................................................. standard analytical reference material SD ..................................................................................................................... standard deviation SRC .................................................................................................. surrogate recovery compound STS ..................................................................................................................... sodium thiosulfate TBP .................................................................................................................... tributyl phosphate TGD ..................................................................................................................... thickened soman THD ......................................................................................................... thickened sulfur mustard TSA .............................................................................................................. technical systems audit VX ............................................... O-ethyl S-2-diisopropylamino ethyl methylphosphonothioate

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Unit List amu – atomic mass unit cm – centimeter g/cm3 – grams per cubic centimeter hr – hour L – liter L/min – liters per minute mm – millimeter min – minute mL – milliliter ppmv – parts per million by volume °C – degrees Celsius μL – microliter μm – micrometer

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1. Introduction

The U.S. Environmental Protection Agency’s (EPA’s) National Homeland Security Research Center (NHSRC) is protecting human health and the environment from adverse impacts resulting from acts of terror. The emphasis of NHSRC is directed toward the decontamination and consequence management, water infrastructure protection, and threat and consequence assessment. NHSRC is working to develop tools and information that will help detect the intentional introduction of chemical, biological, or radiological (CBR) contaminants in buildings or water systems, contain these contaminants, decontaminate buildings or water systems, and dispose of materials resulting from cleanups. In the interest of expanding our national readiness against highly-ranked threat scenarios, the NHSRC is conducting tests to evaluate the performance of products, methods, and equipment for decontaminating contaminated materials. NHSRC is also investigating the fate (e.g., persistence) of biological, chemical, and radiological agents in the absence of decontamination. NHSRC has been systematically evaluating ClO2 fumigant,(1) hydrogen peroxide fumigant, and steam (2) for the decontamination of various chemical warfare agents (CWAs) on interior building material coupons. The efficacies of these decontamination methods have been determined as a function of the concentration of the fumigant, the fumigant contact time, relative humidity, temperature, air exchange rate, and air velocity. Systematic decontamination studies for ClO2 fumigant and three chemical agents: sarin (GB), thickened soman (TGD), and VX were completed in a past EPA effort. (1) These decontamination studies were not performed for sulfur mustard (HD) and it is unknown if ClO2 fumigation of HD is efficacious and/or

will result in the production of toxic byproducts. Thickened HD (THD) was added to the test matrix to offset the possible high natural evaporation rate of HD that could prevent the measurement of the efficacy of the ClO2 fumigation for extended interaction times.

1.1 Objectives Sulfur mustard (bis(2-chloroethyl) sulfide, HD; CAS no. 505-60-2) is a chemical warfare agent that is persistent in the environment and on building materials such as concrete. Because it is one of the more persistent chemical agents, an indoor or outdoor release of HD may require decontamination of surfaces. The overall objective of this work was to systematically evaluate ClO2 vapor as a commercially available decontaminant for decontamination of the chemical agent HD and THD on a single interior building material. Galvanized metal was chosen for its wide application in heating, ventilation, and air conditioning (HVAC) systems and as a nonporous surface material. This work focused on the determination of the decontamination efficacy of ClO2 vapor for removal of HD and THD when compared to controls under ambient environmental conditions. To evaluate the usefulness of a specific decontamination procedure against chemical agents, it is important to determine whether toxic byproducts are produced. ClO2 vapor in combination with high humidity (65-90% RH) has shown to be a selective oxidation method for other CWAs.(1) Oxidation would convert HD into bis(beta-chloroethyl) sulfoxide followed by further oxidation into bis(beta-chloroethyl) sulfone.(3) In a basic solution, these oxidation products would be dechlorinated. However, this last step may not occur in a more acidic

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environment during ClO2 fumigation leaving the vesicant bis(beta-chloroethyl) sulfone as a toxic byproduct on the contaminated surface.

1.2 General approach As a part of this evaluation, the efficacy of the ClO2 decontaminant was determined as function of exposure time. A test chamber was put together that interfaced with the ClO2 delivery system. Known quantities of HD or THD were applied to sample coupons including positive controls, blanks and replicates. Following a specific decontamination contact time with ClO2 vapor, the sample coupons were removed from the test chamber and analyzed for the remaining amount of agent as well as screened for presence of (toxic) fumigation byproducts. The effects of the decontaminant on galvanized metal were determined by visual inspection along with an assessment of the byproducts from the decontamination of HD and THD.

1.3 Test Facilities All decontamination testing was carried out at Battelle’s certified chemical surety facility (Hazardous Materials Research Center) near West Jefferson, Ohio.

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2. Experimental Methods

2.1 Chemical Agent Both HD and THD were used in this evaluation. The HD was supplied by the U.S. Army at the request of the EPA and used neat. The purity of the HD (~100%) was determined on two separate days by performing a comparison of this HD to standard analytical reference material (SARM) supplied by the U.S. Army. The same HD was used for preparing the calibration standards and THD by adding the thickener polymethylmethacrylate (Sigma Aldrich®, St. Louis, MO; CAS no. 9011-14-7) at a 5% weight to volume ratio.

2.2 Test Materials Coupons from the building material, galvanized metal, were used in this evaluation. The galvanized metal coupons were cut from larger pieces of industry HVAC standard, 24 gauge galvanized steel (Adept Products, Inc., West Jefferson, OH). The coupons to which THD and HD were applied had a surface area of approximately 10 cm2 (6.5×1.5 cm) as used previously for other EPA projects.(1)

2.3 Spiking Coupons All coupons intended for use as controls (N=5) or decontamination (N=5), including corresponding laboratory and procedural blanks (N=2), were laid flat onto one of two wire racks (Figure 1). Neat THD (1 µL) or HD was applied to all test coupons and controls. The application delivered ~1 mg per coupon (Figure 2) (density HD = 1.27 g/cm3 at 20 °C) which corresponds to a surface concentration of approximately 1 g/m2. This surface concentration was chosen as a worst-case indoor contamination scenario and is consistent with other EPA decontamination research efforts.(1,2)

Using a repeating syringe, a 1 µL volume of THD or HD was applied at 10-15 second intervals (except for blanks) to each coupon outside the respective test chambers. Following spiking, all coupons were placed immediately into their appropriate chamber or extraction vial.

Figure 1: Test coupons on a wire rack.

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Figure 2: Inoculated coupon.

2.4 Decontamination and Control Chambers

The decontamination chamber fabricated for this testing (Figure 3) was constructed of black acrylic and possessed an internal volume of approximately 300 L. The black acrylic was chosen as ClO2 is light-sensitive. Ports were added to the chamber to accommodate connection to the Sabre™ unit

(used for generating ClO2), a humidification source, and midget impingers for air sampling within the chamber during decontamination. A single door was added to one side of the chamber for transfer of coupons into and out of the chamber. A battery-operated fan was added to the chamber to promote circulation of the ClO2 during decontamination.

Figure 3: Decontamination chamber connected to Sabre unit within chemical fume hood.

The Sabre™ technology (custom-made model, Sabre Technical Services, LLC, Slingerlands, NY) in this evaluation uses ClO2 as the active ingredient and is the same unit as used in previous ClO2 vapor decontamination research.(1) ClO2 is unstable as a compressed gas and, therefore, ClO2 vapor must be produced on-site. The Sabre decontamination technology includes the equipment and chemicals for on-site generation, delivery, removal, and neutralization of ClO2. The decontamination

technology was operated as summarized below. A 19.4 L container containing 15 L of ClO2 decontamination solution (an aqueous solution consisting of 3 g/L ClO2 plus 1000 ppm of sodium chlorite per manufacturer recommendation) was prepared just prior to use in each test. The ClO2 solution was pumped (using a peristaltic pump) into a sparging column and air from the test chamber was pumped into and through the column to sparge ClO2 from the liquid into

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the air stream. The air stream re-entered the glove box to establish the desired gaseous ClO2 concentration. Liquid introduction from the reservoir of ClO2/chlorite solution to the sparging column was initially at the rate of 60 mL per min. When the desired ClO2 concentration in the test chamber was achieved, the liquid introduction into the sparging column and air stream was turned off. As the ClO2 concentration dropped, additional gas was added to the chamber by manually increasing the air and liquid flow rate into the sparging chamber to achieve the target concentration. At the end of the decontamination test the ClO2 in the system

was neutralized by pumping a 10% sodium hydroxide solution (or a 10% sodium thiosulfate solution) into the sparging column. The concentration of gaseous ClO2 in the decontamination chamber was monitored using a modified titration method and is described in detail in Section 2.7. A control chamber (Figure 4) was constructed of clear acrylic and possessed an internal volume of approximately 20 L. Ports were added to the chamber to accommodate connection to the humidification source. A battery-operated fan was added to the chamber to promote air circulation.

Figure 4: Control chamber inside chemical fume hood.

2.5 Temperature and Relative Humidity The temperature of both test chambers was that of the ambient air in the laboratory in which the target was 22 °C ± 2 °C. The RH was adjusted to achieve 80 ± 10% RH using an ultrasonic fog generator. The test chambers were sealed with the only air exchange occurring during RH adjustment and during the decontamination process (decontamination chamber only).

Temperature and RH were monitored and recorded at 20-30 min intervals throughout each test using a National Institute of Standards and Technology (NIST)-traceable combination thermometer/hygrometer. A single thermometer/hygrometer was placed in the control chamber, decontamination chamber, and chemical fume hood housing the two chambers.

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2.6 Extracting and Quantifying Chemical Agents

This investigation used extraction and analysis procedures developed and demonstrated under a prior effort (2) to quantify the concentration of HD and THD extracted from coupons. Briefly, the extraction consisted of a sonication step followed by passive extraction. At the end of each designated decontamination time period, 1.0 µL of the surrogate recovery compound (SRC) tributyl phosphate (TBP; CAS no. 126-73-8) was applied to all coupons (test, controls, and blanks) and then placed individually into an extraction vial. Extraction solvent (10 mL hexane) containing

naphthalene-d8 (CAS no. 1146-65-2) as an internal standard (IS) for quantification was added and each vial was sealed. The vials were sonicated for 2 min, allowed to stand for 5 min before aliquots of the hexane were removed and assayed for HD or THD using gas chromatography/mass spectrometry (GC/MS). Samples were analyzed on an Agilent 6890N GC (Model G1530A, Agilent Technologies, Santa Clara, CA) equipped with 5973N MSD (Model G2589A, Agilent Technologies, Santa Clara, CA) and data analyzed using Agilent’s Enhanced MSD ChemStation software, version D.01.02.16. The specific GC parameters are provided below in Table 1.

Table 1. Parameters used for GC/MS Analysis

Oven Parameters

Initial Temp: 40 °C Initial Time: 1.0 min Ramp Rate: 8 °C/min Final Temp: 300 °C Post Temp: 300 °C Post Time: 1.0 min Run Time: 33.50 min

Inlet Parameters Splitless Injection Injection Volume: 1 µL Inlet Temp: 250 °C

Column Restek Corporation Rtx®-5 30 meter, 0.25 mm ID, 0.5 µm film

Detector

MSD Full Scan Low Mass: 40 amu High Mass: 400 amu

2.7 Measurement of Gaseous ClO2

The concentration of gaseous ClO2 in the decontamination chamber was monitored before beginning a test and approximately every 20-30 min during testing using a modified titration method based on the Standard Method 4500-ClO2 E Amperometric Method II (4) as recommended and used by Sabre Technical Services. For this titration method, ClO2 air samples are passed through impingers (at a rate of 1 L/min for 2 min) that

contain 15 mL of 5% potassium iodide in phosphate buffer (pH 7.0) solution. Under these conditions ClO2 oxidizes iodide to iodine and reduces ClO2 gas to the chlorite ion (ClO2

-) which dissolves in solution. Molecular iodine appears yellow-brown in aqueous solution. After collection of the ClO2 gas, the solution is acidified and the chlorite is allowed to react further with the iodide ion, forming additional iodine and reducing the chlorite to chloride. The total resulting iodine is reduced to iodide when titrated against

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standard 0.1 N (equal to 0.1M) sodium thiosulfate (STS). The titration endpoint is determined when the color of the solution changes from yellow-brown to colorless. The volume (mL) of STS titrated is proportional to the amount of iodine generated, which is

proportional to the gas-phase ClO2 concentration in the air that passed through the impinger. Using Equation 1, the concentration of ClO2 (in ppm per volume in air) was calculated:

ClO2 (ppmv) =

× 1

5 ×24.45 ×1000 (1)

where: V = volume of STS titrant (mL)

M = molarity (mol/L) of STS titrant SR = sampling rate through impinger (L/min) T = sampling time (min) 1/5 = stoichiometric ratio = 1 mol ClO2 reacts with 5 mol STS 24.45 = ideal gas constant, L/mol, at 25 °C, 1 atm

1000 = conversion factor (L/m3) Note that in this case the molarity of STS titrant is equal to its normality (N). The allowable ClO2 concentration variation (± 10%) covers the <2% variation due to differences in test temperature and barometric pressure conditions from the ideal gas constant conditions (1 atm and 25 °C).

2.8 Experimental Design The test matrix is provided in Table 2. For each contact/decontamination time, HD or THD was applied to 5 positive controls and 5 test coupons in addition to the 2 (no HD or THD applied) laboratory blanks and 2 (no HD or THD applied) procedural blanks. Test coupons and procedural blanks were placed in the decontamination chamber and exposed to the ClO2 vapor while the positive control coupons and laboratory blanks were placed in the control chamber in parallel for the associated time periods of decontamination.

Table 2. Test Matrix for ClO2 Decontamination Testing of THD and HD on Galvanized Metal Coupons (number of replicates for each contact time is shown)

Agent ClO2

Concentration (ppmv)

Sample Type Test Type Contact Time

1 hr 2 hr 7 hr

HD

0 Laboratory Blank No HD, no decon 2 2 2 3000 Procedural Blank No HD, with decon 2 2 2 3000 Test Coupon HD, with decon 5 5 5

0 Positive Control HD, no decon 5 5 5

THD

0 Laboratory Blank No THD, no decon 2 2 2 3000 Procedural Blank No THD, with decon 2 2 2 3000 Test Coupon THD, with decon 5 5 5

0 Positive Control THD, no decon 5 5 5

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For each contact/decontamination time test, spike controls were also created. Spike controls are defined as controls in which the agent is directly spiked into the extraction solvent containing the IS and SRC. The recoveries from these spike controls are set as the baseline for maximum agent recovery from the test samples. The amount of agent recovered from the test coupons is then expressed as a proportion of the spike control.

2.9 Calculation of Decontamination Efficacy

The decontamination efficacy was determined by measuring the extracted amount of residual HD on test coupons and comparing to the extracted amount on positive controls (HD or THD applied, not decontaminated and analyzed after the same decontamination time as the test coupons). Concentrations of the target analyte in a coupon extract were first determined according to Equation 2:

AsAis

X· CsCis

W (2) where:

As = Area of target analyte peak in sample extract Ais = Area of internal standard peak Cs = Concentration of target analyte in sample extract (µg/mL) Cis = Concentration of internal standard (µg/mL)

X = slope of the gas chromatograph calibration curve W = Y intercept of the gas chromatograph calibration curve.

Concentration results (g/mL) were converted to total mass by multiplying by extract volume:

M C V (3) where:

Mm = Measured mass of chemical agent (g) C = Concentration (g/mL) from Equation (2) V = Volume of extract (mL).

The decontamination efficacy E was then defined in Equation 4 as:

E 1– M ofHDonTestCoupon

MmofHDonPositiveControlCoupon100% (4)

Since the recovered amounts of the test coupons and positive control coupons are calculated with respect to the associated spike control, Equation (4) becomes

E 1– %RecoveryHDonTestCoupon

%RecoveryHDonPositiveControlCoupon100% (5)

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Decontamination efficacies (mean ± standard deviation) were calculated for all exposure times for galvanized metal to which HD or THD was applied. The use of multiple coupons allows for the determination of a mean and standard deviation of the efficacy value.

2.10 Decontamination Byproduct Determination

In addition to HD, IS, and SRC, the chromatograms from each decontaminated sample showed additional observed peaks that underwent a qualitative assessment. Using the chromatograms from each sample, additional observed peaks in the chromatograms of the decontaminated samples were further analyzed using the ChemStation (version D.01.02.16) software and mass spectrometry libraries from NIST and Battelle’s Biomedical Research Center. The observed peaks were assessed for best predicted chemical match (when possible) and expressed as a percentage of HD in each sample by comparing the ratio of total area counts for the longest decontamination time period (7 hours) only.

2.11 Surface Damage The physical effect of the decontamination technologies on the galvanized metal was also monitored during the investigation. The qualitative approach involved a gross visual investigation of the damage to the galvanized metal caused by the decontamination technology. Before and after decontamination of the test coupons, the appearance of the coupons was visually inspected for any obvious changes in the color, reflectivity, and apparent roughness of the material surfaces.

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3. Results and Discussion

3.1 Extraction Efficiencies of HD and THD from Galvanized Metal

Acceptable extraction efficiencies (within the accepted criterion of 40-120% with less than 30% coefficient of variance) for HD from galvanized metal using 10 mL of hexane as the extraction solvent followed by ultrasonication were reported. (2) These efficiencies were not explicitly verified in this study since the same extraction procedure was followed for both test coupons and positive controls, hereby cancelling their effect on the efficacy calculation.

3.2 Decontamination Testing of THD and HD using Chlorine Dioxide

The fumigation of galvanized metal coupons with either HD or THD applied for 1, 2, or 7 hr exhibited similar decreasing trends in recoverable agent when comparing the decontaminated samples with their respective matched controls, shown in Table 3. The lower recovery with increased time of both HD and THD for the positive controls can be attributed to the evaporation process. This process appears slower for THD when compared to HD except for the 7 hr contact time result. This recovery value has an associated relative standard deviation of more than 30%. However, no outliers were indentified (Grubbs outlier test) among the

recoveries of the five coupons that make up this mean recovery value. A comparison of the HD positive control recovery data with other positive control recovery data from similar fumigation studies on galvanized metal (2) suggests that the evaporation of the 7 hr HD positive control slowed down significantly, unexpectedly resulting in a higher recovery. No evidence was found in this study that can explain this single discrepancy since, e.g., changes in environmental conditions such as temperature were negligible (see Section 4.1.1, Table 5). It should be noted that the use of two separate chambers of uneven size (300 L versus 20 L for the test and positive control chamber, respectively) may have resulted in different evaporation rates of the HD and THD from the coupons. This difference may have created a bias in the positive control extraction amounts resulting in a higher amount left on the coupons than if the positive control chamber had been of equal size to the test coupon/fumigation chamber. The impact of this size difference is difficult to assess since it depends on the size and chamber wall material characteristics. Nevertheless, the impact is expected to be minimal and should not change the outcome of this study.

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Table 3. Mean (±SD) Percent Recovery of HD and THD from Samples.

Agent ClO2

Concentration (ppmv)

Sample Type Percent Recovery (%)a

1 hr contact 2 hr contact 7 hr contact

HD

0 Laboratory Blank 0 0 0 3000 Procedural Blank 0 0 0 3000 Test Coupon 82 ± 4* 74 ± 2* 31 ± 9*

0 Positive Control 94 ± 5 79 ± 2 49 ± 2

THD

0 Laboratory Blank 0 0 0 3000 Procedural Blank 0 0 0 3000 Test Coupon 98 ± 10 63 ± 9* 35 ± 5

0 Positive Control 96 ± 5 89 ± 2 33 ± 16 a The amount of agent recovered from the samples is expressed as proportion of the spike controls. * Indicates mean value is significantly different (p<0.05; Student’s t-test) from corresponding control. A graphical representation of the decontamination data is also provided in Figure 5. Statistical analysis (Student’s t-test) reveals that the mean recovery of HD from the decontaminated test coupons was statistically significantly lower (p<0.05) than the

corresponding controls at the respective sampling times. However, for THD, only the 2 hr time point showed a significant difference (p<0.05) between the test and control samples. Nevertheless, both HD and THD were persistent, even after a 7 hr contact time with 80% RH and 3000 ppmv ClO2.

Figure 5: Mean (±SD) percent recovery HD and THD

1 hour 2 hour 7 hour0

20

40

60

80

100

Perc

ent o

f Spi

ke C

ontro

l

Decontamination Time

THD

1 hour 2 hour 7 hour0

20

40

60

80

100

Positive Control Test Coupon

HD

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The recovery results were used to determine the decontamination efficacy for each

decontamination time using Equation 5 and are shown in Figure 6.

Figure 6: Decontamination efficacy of 3000 ppmv ClO2

Decontamination efficacies were at best 37% for the 7 hr HD decontamination test. However, this value is probably biased high based on the higher than expected recovery of the HD positive control after 7 hr as discussed earlier in this report. Otherwise efficacies for HD decontamination were well below 15%. Efficacies for the THD decontamination were either not significant in cases where the positive control recoveries were less than the decontaminated test recoveries (1 and 7 hr decontamination time) or were less than 30% for the 2 hr decontamination time.

3.3 Assessment of Decontamination Byproducts

Chromatographic analysis of the decontaminated samples revealed the presence of three additional peaks beyond the expected peaks for HD, IS, and SRC. These three additional peaks were not observed in the chromatograms from the blanks and positive control coupons. The three additional observed peaks underwent a qualitative assessment as potential (toxic) byproducts of the decontamination process. Some defined characteristics of these byproducts are provided in Table 4 for the 7 hr decontamination time. For HD, all samples exposed to ClO2 vapor for 1, 2 or 7 hr exhibited the three defined peaks at retention times 12.6, 16.3, and 16.7 minutes, respectively. For THD, the same peaks were observed, but only for the 2 and 7 hr exposure times.

0

10

20

30

40

50

1 hour 2 hour 7 hour

Effi

cacy

(%)

Decontamination Time

HD

THD

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Table 4. Characteristics of Observed Peaks in Decontaminated Samples after 7 Hour Contact Time.

Agent/Sample Retention Time (min)

Range as % of HD or THD in Samplea Potential Compound Identified

HD 11.9 - Peak 1/HD decon 12.6 3-9% NAb

Peak 2/ HD decon 16.3 10-42% bis(beta-chloroethyl) sulfone [CAS no. 471-03-4]

Peak 3/ HD decon 16.7 9-31% bis(beta-chloroethyl) sulfoxide [CAS no. 5819-08-9]

THD 11.9 - Peak 1/THD decon 12.6 5-9% NAb

Peak 2/THD decon 16.3 10-15% bis(beta-chloroethyl) sulfone [CAS no. 471-03-4]

Peak 3/THD decon 16.7 9-14% bis(beta-chloroethyl) sulfoxide [CAS no. 5819-08-9]

a Based on ratio of total area counts of each unknown peak to HD; range based on data from five replicates. bNA = Not Applicable; MS libraries could not yield a consistent known match. No absolute quantification of the observed decontamination byproducts was performed as this was not an objective of this study. The identified bis(beta-chloroethyl) sulfone (Peak 2) is considered to have appreciable vesicant activity (5) while bis(beta-chloroethyl) sulfoxide (Peak 3) has no vesicant activity.(6) In general, the byproduct formation was lower for THD which may be attributed to the inability of ClO2 vapor to react with HD in the presence of the thickener. The observation of these fumigation byproducts after 7 hr of exposure to ClO2 vapor demonstrates that oxidation occurs although the associated decontamination efficacy is nonexistent for THD after 7 hr (see Figure 6). This apparent conflict in results may be attributed to the bias in the positive control recovered amounts as discussed in Section 3.2. A higher recovered amount of THD from the positive controls when using an equally sized chamber would have resulted in a positive efficacy value which then can explain the observed byproduct formation. A more detailed study may test this hypothesis. Nevertheless, ClO2 vapor decontamination of HD and THD under the conditions applied in this study is not efficient and results in formation of toxic byproducts.

3.4 Surface Damage Following exposure to ClO2 vapor during the decontamination testing, there was no observable damage to any of the galvanized metal coupons.

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4. Quality Assurance/Quality Control

4.1 Decontamination Testing of THD and HD using Chlorine Dioxide

4.1.1 Temperature and Relative Humidity For the tests conducted according to the test matrix in Table 2, the mean temperatures

during the specified contact times are provided below in Table 5. The mean relative humidity for the chemical fume hood (room), decontamination chamber, and control chamber are provided in Table 6.

Table 5. Mean (±SD) Temperatures (°C) during Testing.

Agent Sample Type Mean (±SD) Temperature (°C) 1 hr contact 2 hr contact 7 hr contact

HD Decontamination Chamber 22.3 ± 0.1 22.4 ± 0 21.0 ± 0.1 Control Chamber 22.2 ± 0.1 22.2 ± 0.1 21.0 ± 0.2 Chemical Fume Hood (Room) 22.1 ± 0.3 22.3 ± 0.1 20.8 ± 0.2

THD Decontamination Chamber 21.8 ± 0.2 21.4 ± 0.6 21.0 ± 0.2 Control Chamber 21.4 ± 0.3 21.2 ± 0.3 20.9 ± 0.3 Chemical Fume Hood (Room) 21.5 ± 0.3 21.4 ± 0.8 20.8 ± 0.4

Table 6. Mean (±SD) Relative Humidity (%) during Testing.

Agent Sample Type Mean (±SD) Relative Humidity (%) 1 hr contact 2 hr contact 7 hr contact

HD Decontamination Chamber 82 ± 1 78 ± 1 80 ± 4 Control Chamber 88 ± 2 89 ± 1 86 ± 2 Chemical Fume Hood (Room) 44 ± 2 44 ± 2 44 ± 1

THD Decontamination Chamber 82 ± 1 81 ± 1 81 ± 1 Control Chamber 81 ± 0 81 ± 1 84 ± 3 Chemical Fume Hood (Room) 44 ± 1 45 ± 1 45 ± 2

4.1.2 Testing and Analysis For the tests conducted according to the test matrix in Table 2, the mean ClO2

concentration (ppmv) during the specified contact times is provided below in Table 7.

Table 7. Mean (±SD) ClO2 Concentration (ppmv) during Testing.

Agent Mean (±SD) ClO2 Concentration (ppmv) 1 hr contact 2 hr contact 7 hr contact

HD 2926 ± 86 2977 ± 76 2911 ± 70 THD 2812 ± 65 2816 ± 112 2921 ± 195

For HD, the observed recovery from the spike controls (agent directly spiked into the extraction solvent containing the IS and SRC) was 76, 80, and 83 percent of expected for 1,

2, or 7 hr, respectively. For THD, the observed recovery from the spiked controls was 91, 75, and 72 percent of expected for 1, 2, or 7 hr, respectively. These recoveries from

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the spike controls were set as the baseline for maximum agent recovery from test samples. The amount of agent recovered from the test coupons was expressed as a proportion of the spike controls.

For both HD and THD, the observed recovery of the SRC from the galvanized metal coupons as a percent of expected was similar at all time periods for the control and test coupons with a marginal exception of the HD 7 hr samples. The data are summarized below in Table 8.

Table 8. Mean (±SD) Percent Recovery of the Surrogate Recovery Compound from Samples.

Agent Sample Type Mean Percent Recovery (%) of Expected (±SD) 1 hr contact 2 hr contact 7 hr contact

HD

Laboratory Blank 100 ± 0 109 ± 0.4 93 ± 3 Procedural Blank 98 ± 5 112 ± 5 92 ± 1 Test Coupon 106 ± 5 103 ± 2 82 ± 18 Positive Control 98 ± 3 107 ± 3 87 ± 5

THD

Laboratory Blank 120 ± 2 108 ± 1 108 ± 0.4 Procedural Blank 123 ± 6 102 ± 2 110 ± 1 Test Coupon 116 ± 2 107 ± 4 104 ± 4 Positive Control 107 ± 1 107 ± 2 107 ± 1

4.2 Performance Evaluation Audit Performance evaluation audits were conducted by the respective laboratory

personnel to assess the quality of the results obtained during these tests. Results of the PE audits are presented in Table 9 below.

Table 9. Performance Evaluation Audit Results.

Parameter Measurement Method Acceptance Criteria Actual Tolerance

Temperature NIST-traceable thermohygrometer

Agree ±10% with NIST traceable calibrated thermometer All < 1%

RH NIST-traceable thermohygrometer

Agree ±10% within the 70%-90% RH testing range against NIST traceable calibrated hygrometer

All <10%

Gas Volume Calibrated mass flow controller (Sierra Instruments)

Agree ±5% against NIST traceable primary flow calibrator All <1%

Time Laboratory digital clock

Agree within 1 second/minute against NIST Official U.S. time at http://nist.time.gov/timezone.cgi?Eastern/d/-5/java,

All < 1 second/minute

CW Agent Spike Control

Extraction/ chromatographic quantitation

Percent recovery within the range of 40%-120% All within range of 40-120%

Titration Method

Titration with sodium thiosulfate

Agree ±10% of standard value against certified NIST-traceable chlorite standards 2 measurements, both < 4%

pH Meter Calibrated pH meter at time of use

Agree within ± 0.1 pH units against 2 point calibration with standard buffers All within 0.1 pH units.

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4.3 Technical Systems Audit Battelle quality assurance (QA) staff conducted a technical systems audit (TSA) on February 11, 2010 to ensure that the tests were being conducted in accordance with the appropriate test/QA plan and Quality Management Plan. As part of the audit, test procedures were compared to those specified in the test/QA plan and data acquisition and handling procedures were reviewed. Observations and findings from the TSA were documented and submitted to the Battelle task order leader for response. None of the findings of the TSA required corrective action; TSA records were permanently stored with the Battelle QA manager.

4.4 Data Quality Audit At least 10% of the data acquired during the decontamination technology evaluation were audited by the Battelle QA manager or a designee. A Battelle QA auditor traced the data from the initial acquisition, through reduction and statistical analysis, to final reporting to ensure the integrity of the reported results. All calculations performed on the data undergoing the audit were checked.

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5. Summary

This evaluation project assessed the ability of ClO2 vapor to decontaminate the chemical warfare agents HD and thickened HD (THD). Concentrations of HD and THD for positive controls were observed to decrease over a 7 hr time period from >90% of expected after 1 hour to <50% of expected after 7 hours predominantly due to evaporation. Exposure to ClO2 over the same time period yielded decreases in HD and THD concentrations that were similar to that of the positive controls. A statistical analysis revealed that the mean recovery of HD from the decontaminated test coupons was statistically significantly lower (Student’s t-test p<0.05) than the corresponding positive controls at the respective sampling times. However, for THD, only the 2 hr time point showed a significant difference (p<0.05) between the test and positive control samples. Clearly, considerable amounts of HD or THD remained on the coupon surface after 7 hr of fumigation. The potential for formation of toxic fumigation byproducts was investigated through a full scan GC/MS analysis. Gas chromatograms from each decontaminated

sample showed there were three additional observed peaks in samples in addition to HD, internal standard, and surrogate recovery compound. No additional peaks were observed in the controls or blanks (samples with no HD or THD applied) excluding contamination of the neat HD solution. For HD, all samples exposed to ClO2 for 1, 2 or 7 hr exhibited three defined peaks, while the same peaks were observed for THD, but only for the 2 and 7 hr exposure times. Two of the peaks were identified as bis(beta-chloroethyl) sulfone and bis(beta-chloroethyl) sulfoxide using mass spectrometry libraries, while the third peak did not match consistently with compounds in the databases. The HD oxidation results in the formation of significant amounts of bis(beta-chloroethyl) sulfone which is a vesicant. Finally, following exposure to ClO2 vapor during the decontamination testing, there was no observable damage to any of the galvanized metal coupons. What is clear from this study is that ClO2 fumigation as described in these tests should not be considered as an effective decontamination method for HD or THD.

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6. References

1. Rogers, J., Hayes, T., Kenny, D.,

MacGregor, I., Tracy, K., Krile, R., Nishioka, M., Taylor, M. Riggs, K., and Stone, H. Decontamination of Toxic Industrial Chemicals and Chemical Warfare Agents on Building Materials Using Chlorine Dioxide Fumigant and Liquid Oxidant Technologies; (EPA/600/R-09/012); Cincinnati, OH: U.S. Environmental Protection Agency. Office of Research and Development. National Homeland Security Research Center. February 2009. http://www.epa.gov

2. U.S. Environmental Protection

Agency. Assessment of Fumigants for Decontamination of Surfaces Contaminated with Chemical Warfare Agents; (EPA/600/R-10/035); U.S. Environmental Protection Agency, Office of Research and Development, National Homeland Security Research Center, Cincinnati, OH. August 2010. http://www.epa.gov

3. Chang, Y-C., Baker, J.A., and Ward, J.R. “Decontamination of Chemical Warfare Agents”, Chem. Rev. 92(8):1729-1743 (1992)

4. APHA (American Public Health Association), American Water Works Association and Water Environment Federation. Standard Methods for the Examination of Water and Wastewater. 21st edition. American Public Health Association, Washington, D.C. 2005.

5. Chemcas. See, e.g., http://www.chemcas.com/msds/cas/msds128/471-03-4.asp for toxicity data. Last access 02-04-2011

6. Chemcas. See, e.g.,

http://www.chemcas.com/msds/cas/msds128/5819-08-9.asp for toxicity data. Last access 02-04-2011

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