oEPA
LPA/600/R-15/279 I November 2015 I www2.epa.gov/research
United States
Environmental Protection
Agency
Application of Electrostatic and
Backpack Sprayer Systems for
Decontamination of Building
Materials Contaminated with
Malathion
ASSESSMENT AND EVALUATION REPORT
Office of Research and Development
National Homeland Security Research Center
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EPA 600- R-15-279
Application of Electrostatic and Backpack Sprayer
Systems for Decontamination of Building Materials
Contaminated with Malathion
Assessment and Evaluation Report
National Homeland Security Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Disclaimer
The U.S. Environmental Protection Agency through its Office of Research and Development funded and
managed the research described here under contract EP-C-09-027, Work Assignment 5-67, with
ARCADIS U.S., Inc. It has been subjected to the Agency's review and has been approved for publication.
Note that approval does not signify that the contents necessarily reflect the views of the Agency. Mention
of trade names, products, or services does not convey official EPA approval, endorsement, or
recommendation.
Questions concerning this document or its application should be addressed to the principal investigator:
Lukas Oudejans, Ph.D.
Decontamination and Consequence Management Division
National Homeland Security Research Center
U.S. Environmental Protection Agency (MD-E343-06)
Office of Research and Development
109 T.W. Alexander Drive
Research Triangle Park, NC 27711
Phone: 919-541-2973
Fax: 919-541-0496
E-mail: Oudeians.Lukas@epa.gov
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Acknowledgments
This effort was directed by the principal investigator, Lukas Oudejans, of the Office of Research and
Development's (ORD) National Homeland Research Center (NHSRC), through a collaborative effort with
the Office of Emergency Management's (OEM) Chemical, Biological, Radiological, and Nuclear
Consequence Management Advisory Division (CBRN CMAD) to evaluate novel approaches for
decontamination of surfaces contaminated with chemical agents.
This effort was completed under EPA contract number EP-C-09-027 with ARCADIS US, Inc. The support
and efforts provided by ARCADIS US, Inc., are gratefully acknowledged.
The following persons are acknowledged for their contributions to this project:
Ramona Sherman and Eletha Brady-Roberts (Quality Assurance)
NHSRC, ORD, US EPA
Cincinnati, OH 45220
Joan Bursey (Editorial)
NHSRC, ORD, US EPA
Research Triangle Park, NC 27711
The peer reviewers of this report are also acknowledged for their input to this product:
Shannon Serre,
CMAD, OEM
Office of Solid Waste and Emergency Response (OSWER), US EPA
Research Triangle Park, NC 27711
Dave Mickunas,
Emergency Response Team (ERT)
Office of Superfund Remediation and Technology Innovation (OSRTI)
OSWER, US EPA
Research Triangle Park, NC 27711
Paul Lemieux,
NHSRC, ORD, US EPA
Research Triangle Park, NC 27711
iv
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Table of Contents
Disclaimer iii
Acknowledgments iv
List of Tables viii
List of Acronyms and Abbreviations ix
Executive Summary xi
1 Introduction 1
1.1 Project Objectives 1
2 Experimental Approach 2
2.1 Overview of the Experimental Approach 2
2.2 Decontamination Efficacy Determination 2
2.3 Statistical Analysis 2
2.4 Test Setup 3
2.5 Test Materials and Characteristics 4
2.6 Coupon Contamination 5
2.6.1 Chemical Agent 5
2.6.2 Coupon Contamination 5
2.7 Decontamination Testing 7
2.7.1 Decontamination Solution 7
2.7.2 Decontamination Approach 7
2.8 Extraction Solvent 9
2.9 Decontamination Testing 9
2.9.1 Test Matrix 9
2.9.2 Extraction Method for Coupons 10
2.10 Sample Identification 11
2.11 Chemical Analysis 12
2.11.1 GC/MS Analysis 12
2.11.2 GC/MS Detection Limit 13
2.11.3 GC/MS Quantification 13
3 Results and Discussion 15
3.1 Shakedown of Airbrush Delivery Method 15
3.2 Electrostatic Sprayer Decontamination Results 15
3.2.1 Thin Film Deposition Method 15
v
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3.2.2 Evenly Distributed Low Concentration Droplet Deposition Method 17
3.2.3 Evenly Distributed High Concentration Droplet Deposition Method 20
3.3 Backpack Sprayer Decontamination Results 25
3.3.1 Thin Film Deposition Method 25
3.3.2 Evenly Distributed Low Concentration Droplets Deposition Method 25
3.3.3 Evenly Distributed High Concentration Droplet Deposition Method 25
4 Quality Assurance/Quality Control 29
4.1 Quality Assurance and Quality Control Checks 29
4.2 Data Quality Acceptance Criteria Verification 29
4.2.1 Control of Monitoring and Measuring Devices 29
4.3 GC/MS Calibrations 30
4.4 Other QC Chemical Analyses 31
4.4.1 Positive Control Recoveries 31
4.4.2 Procedural and Laboratory Blanks 32
5 Summary 33
6 References 35
vi
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List of Figures
Figure ES-1. Decontamination Efficacies for Malathion-Contaminated Materials Using Bleach
Dispensed from an Electrostatic Sprayer (ESS) and Backpack Sprayer (BPS) xii
Figure 2-1. Coupon Configuration for the Even-Distribution Droplet Contamination Scenario 3
Figure 2-2. Coupon Configuration during the Thin Film Contamination 4
Figure 2-3. Master Performance Pro Dual-Action Gravity Feed Airbrush 6
Figure 2-4. Picture of SC-1 Electrostatic Sprayer 8
Figure 2-5. Electric Backpack Sprayer 9
Figure 2-6. Stainless Steel Coupons during Extraction 11
Figure 3-1. Stainless Steel Material Coupons Contaminated using an Airbrush 16
Figure 3-2. Wood Material Coupons Contaminated using an Airbrush 16
Figure 3-3. Vinyl Material Coupons Contaminated using an Airbrush 16
Figure 3-4. Evenly Distributed Low Concentration Droplet Deposition Method on SS Material
Coupons 18
Figure 3-5. Evenly Distributed Low Concentration Droplet Deposition Method on Wood Material
Coupons 18
Figure 3-6. Evenly Distributed Low Concentration Droplet Deposition Method on Vinyl Material
Coupons 19
Figure 3-7. Evenly Distributed High Concentration Droplet Deposition Method on SS Material
Coupons 21
Figure 3-8. Evenly Distributed High Concentration Droplet Deposition Method on Wood Material
Coupons 22
Figure 3-9. Evenly Distributed High Concentration Droplet Deposition Method on Vinyl Material
Coupons 22
Figure 3-10: Corrosion Spots on SS Material Coupons following Decontamination with Bleach
using the Evenly Distributed High Concentration Droplets Deposition Method 23
vii
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List of Tables
Table 2-1. Description of Building Materials for Decontamination Testing 5
Table 2-2. Contamination Solution Properties 7
Table 2-3. Decontamination Solution Properties 7
Table 2-4. Building Material Surface Decontamination Test Matrix 10
Table 2-5. Sample Identification 12
Table 2-6. Calibration Solutions (CS1-CS9) Concentrations 13
Table 3-1. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Material
Coupons Contaminated via an Airbrush 17
Table 3-2. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Evenly
Distributed Low Concentration Droplet Deposition Method on Material Coupons 20
Table 3-3. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Evenly
Distributed High Concentration Droplet Deposition Method on Material Coupons 24
Table 3-4. Test Results for Bleach Decontamination using a Backpack Sprayer on Material
Coupons Contaminated via an Airbrush 26
Table 3-5. Test Results for Bleach Decontamination using a Backpack Sprayer on Evenly
Distributed Low Concentration Droplet Deposition Method on Material Coupons 27
Table 3-6. Test Results for Bleach Decontamination using a Backpack Sprayer on Evenly
Distributed High Concentration Droplet Deposition Method on Material Coupons 28
Table 4-1. Data Quality Objectives and Results for Test Measurements 30
Table 4-2. Equipment Calibration Schedule 31
Table 4-3. Quality Assurance Measurements 32
Table 5-1. Summary of Decontamination Efficacies using ESS and BPS for Three Malathion
Deposition Distributions 33
viii
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List of Acronyms and Abbreviations
BPS backpack sprayer
°C degrees centigrade (Celsius)
CAS Chemical Abstracts Service
CBRN Chemical, Biological, Radiological, and Nuclear
CCV continuing calibration verification
CMAD Consequence Management Advisory Division
cm3 cubic centimeter(s)
CWA chemical warfare agent
DQO data quality objective
EPA U. S. Environmental Protection Agency
ERT Environmental Response Team
ESS electrostatic sprayer system
FAC free available chlorine
g gram(s)
GC/MS gas chromatography/mass spectrometry
HSRP Homeland Security Research Program
ICAL internal calibration (standard)
IS internal standard
kHz kilohertz
L liter(s)
LB laboratory blank
MDL method detection limit
min minute(s)
mL milliliter(s)
jjg microgram(s)
ND non-detect
NHSRC National Homeland Security Research Center
NIST National Institute of Standards and Technology
OEM Office of Emergency Management
ORD Office of Research and Development
OSRTI Office of Superfund Remediation and Technology Innovation
OSWER Office of Solid Waste and Emergency Response
PB procedural blank
PC positive control
pg picogram(s)
P/N part number
ix
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QA Quality Assurance
QC Quality Control
QAPP Quality Assurance Project Plan
RF response factor
SD standard deviation
SIM selected ion monitor
SS stainless steel
TC test coupon
VMD volume median diameter
VX O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate
x
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Executive Summary
This project supports the mission of the U.S. Environmental Protection Agency Office of Research and
Development's Homeland Security Research Program (HSRP) by providing information relevant to the
decontamination of areas contaminated as a result of a chemical contamination incident. The primary
objective of this investigation was to evaluate the use of two different types of spray systems to supply a
decontaminant to a surface.
The evaluation tests described in this report determined the effectiveness of an electrostatic sprayer
system in delivery of a decontaminant to clean a building material contaminated with a toxic chemical.
Efficacy results using the electrostatic sprayer for neutralization of the chemical from three building
materials were compared to the results obtained using the more traditional backpack sprayer system.
Electrostatic sprayers are more efficient than conventional spray systems, and they deliver a more
uniform distribution of the liquid on an (uneven) surface. In this study, the targeted decontaminant was
full-strength bleach and the chemical was malathion, a pesticide and surrogate for the chemical warfare
agent (CWA) O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX). Full-strength bleach
was selected over more traditional diluted bleach (typically 10 fold dilution) based on outcomes from
previous bench scale research in which poorer decontamination efficacy was observed against materials
contaminated with CWAs HD and VX [1], Malathion was applied uniformly as a thin film or as more
discrete droplets of low or high concentration. The impact on the efficacy of these different malathion
distribution patterns was also investigated. Three building material substrates were included, namely,
stainless steel, wood, and vinyl.
Summary of results:
The decontamination efficacies as obtained using the electrostatic and backpack sprayer systems are
shown in Figure ES-1. For stainless steel surfaces, both spray systems were able to decontaminate the
surface by achieving mostly non-detectable malathion amounts after a 30 min dwell time of the full-
strength bleach applied to the contaminated material. The results indicate that efficacies were not
dependent on the actual mode of malathion distribution.
xi
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h-
0.05). Efficacy values for vinyl are between the results observed for
stainless steel and wood with a better performance when using the electrostatic sprayer for two of the
three modes of malathion distribution. For both wood and vinyl, the malathion distribution has an impact
on the observed efficacy. Highly concentrated (malathion) droplets are more difficult to decontaminate
than a more evenly distributed film.
Impact of this study
Both sprayer systems performed equally well at decontaminating flat surfaces. The more uniform initial
distribution of the decontamination solution on the surface as applied by the electrostatic sprayer does not
result in a significantly better efficacy under the tested conditions. Localized high concentrations of
chemicals are more difficult to decontaminate and may require repeated application of a given
decontamination technology.
xii
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1 Introduction
This project supports the mission of the U.S. Environmental Protection Agency's (EPA) Office of
Research and Development's (ORD) Homeland Security Research Program (HSRP) by providing
information, expertise and products that can be widely used to prevent, prepare for, and recover from
public health and environmental emergencies arising from terrorist threats and incidents. EPA
researchers initiated bench scale studies to tailor the decontamination practices for surfaces
contaminated with chemical warfare agents (CWAs), to the environment and material affected, type of
chemical encountered, and to determine the effect on materials using operationally relevant
decontamination dwell times. This project is a first effort to scale up decontamination methods from small
surfaces (coupon sizes typically less than 10 cm2) to surface sizes of approximately 1 square foot. This
project supports the HSRP mission in determining the effectiveness of undiluted bleach for the removal of
malathion, selected as a pesticide and surrogate for the CWA O-ethyl S-[2-(diisopropylamino)ethyl]
methylphosphonothioate (VX), from building surfaces using two different spray/fine-mist decontaminant
delivery methods.
1.1 Project Objectives
The objective of this study was to determine the decontamination efficacy of bleach as a target
decontaminant for the removal of malathion as applied to three building materials (stainless steel
(SS), wood, and vinyl). Two decontamination spray methods, an electrostatic sprayer (ESS)
system and a backpack sprayer (BPS) system, were evaluated for three building materials and
three malathion deposition methods, namely, a thin-film application, an evenly distributed low
concentration of droplets, and an evenly distributed high concentration of droplets.
The test matrix for this effort consisted of 18 pairings (three material types, three malathion deposition
methods, and two decontamination spray methods). Three (3) replicate test coupons (TCs), three (3)
replicate positive control coupons (PCs), one (1) procedural blank (PB), and one (1) laboratory blank (LB)
were included in each test - a total of eight (8) coupons for each material/malathion deposition
condition/decontamination method combination. A single 30-minute (min) interaction time between the
bleach and malathion was used for all 18 tests.
1
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2 Experimental Approach
2.1 Overview of the Experimental Approach
The decontamination efficacy of the bleach solution was assessed by determining the amount of
malathion remaining on each test coupon after a 30-min decontamination period using bleach, by
comparing this result to the amount recovered from the positive control coupons, which were
contaminated but not decontaminated at the same time as the test coupons.
The amount of malathion remaining on the surface was quantified via chemical extraction of the coupon
followed by measurement of the concentration of the target chemical through gas chromatographic/mass
spectrometric (GC/MS) analysis. The mean decontamination efficacy along with the standard deviation
was calculated for each set of replicates and controls. The standard deviation of the efficacy was
calculated by propagation of error using the standard deviation of the average mass of agent remaining
on the test coupons and on the positive control coupons.
At the end of the 30-min decontamination interaction time for the decontamination product with the
malathion, the decontamination process was quenched through extraction of the remaining chemical by
neutralizing the decontamination chemical through dilution. The quenching of the decontamination
reaction was accomplished by dropping all twelve coupons that constitute one sample into a beaker and
adding 150 milliliters (mL) of extraction solvent (hexane) followed by a 10-min sonication. After
completion of the sonication and a short (5-10 min) time period to separate solvent phases, an aliquot of
the extraction solvent was diluted (10 fold) further prior to analysis. This second dilution step ensures a
completely quenched decontamination process. This is critical as the chemical analysis typically occurs
hours to days later which is a significantly longer time period than the 30-min decontamination interaction
time at the surface. A non-quenched reaction would potentially bias decontamination efficacy
measurements.
2.2 Decontamination Efficacy Determination
The decontamination efficacy was determined by measuring the amount of residual malathion on the test
coupons and comparing this amount with positive controls (spiked with malathion, not decontaminated
and analyzed after the same "contact time" as the test coupons) using Equation 1:
where:
E = % Efficacy
Mi = Measured mass of malathion on the ith test coupon (micrograms [jjg]);
Ma = Average measured mass of malathion on the control coupons (jjg).
2.3 Statistical Analysis
The standard deviation in the measured mass of malathion is calculated as shown in Equation 2:
f
E= 1
Mt on Test Coupon ^ ^ QQ%
Ma on Positive Control Coupon
(1)
v
2
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= jz^Cxi-n)2
¦\] N-l
where:
a = standard deviation
)j = mean
x, = Ith value of the variable being evaluated, e.g., control coupon
N = total number of elements in the population.
2.4 Test Setup
Decontamination solution testing occurred in a conventional chemical safety hood. Twelve (12)
building material coupons (2" x2" size) were placed in an individual 14" x 14" transparent test tray
to provide representative coverage of an approximately 12" x 12" test area. The use of multiple
smaller coupons to represent a larger surface area instead of a single 12"x 12" coupon significantly
facilitates the extraction process for the material. The surface of each test tray had a grid to allow
for a reproducible coupon arrangement pattern. This coupon arrangement was used for the even
distribution of droplets for contamination scenario tests (Figure 2-1). For the thin-film application, an
airbrush type of application was used to apply malathion in ethanol solution onto twelve individual 2"x
2" size coupons. In that case, the coupons were placed closely together to reduce variation in the
amount of malathion received during the airbrush spraying between individual coupons. (Figure 2-2).
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Figure 2-1. Coupon Configuration for the Even-Distribution Droplet Contamination Scenario.
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Figure 2-2. Coupon Configuration during the Thin Film Contamination,
2.5 Test Materials and Characteristics
The representativeness and uniformity of test materials are essential in achieving statistically defensible
evaluation results. Material representativeness means that these materials are typical of those currently
used in buildings in terms of quality, surface characteristics, and structural integrity. In this effort,
representativeness was assured by selecting test materials typical of the materials found in residential
dwellings that meet industry standards or specifications for indoor use, and by obtaining those materials
from appropriate suppliers. Material uniformity means that all these material coupons are equivalent for
purposes related to testing. Uniformity was maintained by obtaining and preparing a quantity of material
sufficient to allow multiple test samples to be prepared with presumably uniform characteristics (i.e., test
coupons were cut from the interior rather than the edge of a large piece of material). A description of the
selected building materials for decontamination testing is provided in Table 2-1.
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Table 2-1. Description of Building Materials for Decontamination Testing
Material
Description
Manufacturer/
Supplier Name,
Location
Coupon Surface
Size, L x W (inches)
Material Preparation
Stainless
Steel
Multipurpose Stainless Steel
(48x48 inch), type 304,
#2B mill (unpolished), 0.036
inch thick
McMaster-Carr,
Elmhurst, IL, USA
2" x 2" organized
into 12" x 12" test
area
- Remove any
lubricant/grease from
shearing with acetone and
wipe dry
- Remove particles and dust
by wiping clean with water
and wipe dry
Wood
Untreated Pine Plywood,
0.5" thick
Plytanium/
Lowe's, Durham,
NC, USA
1.6" x 1" organized
into 12" x 12" test
area
- Remove particles by wiping
clean with water and wipe
dry
Vinyl
flooring
Traffic MASTER Allure (12 x
24 inch) Ivory Travertine,
vinyl tile; residential grade,
stain resistant, scratch
resistant, 0197 inch thick
Armstrong/ Home
Depot, Durham,
NC, USA
2" x 2" organized
into 12" x 12" test
area
- Remove particles by wiping
clean with water and wipe
dry
SS coupons were prepared using heavy duty power hydraulic shears to cut the metal from larger sheets
to the correct length and width. Lubricant from the shears was removed using acetone and wiped dry.
2.6 Coupon Contamination
2.6.1 Chemical Agent
The target chemical agent was malathion (Chemical Abstracts Service (CAS) # 121-75-5), which is
considered to be a surrogate for the CWA VX (O-ethyl S-[2-(diisopropylamino)ethyl]
methylphosphonothioate). The chemical agent malathion (part number (P/N): N-12346-1OOMG, Chem
Services Inc., West Chester, PA) was purchased in neat liquid form (>98% purity) and initially dissolved in
ethanol (Sigma-Aldrich, St. Louis, MO Cat # 459828-1 liter (L) spectrophotometric grade) to 50/50 percent
by volume. Malathion was further dissolved in ethanol at 12, 50 or 500 mg/mL concentration, depending
on each spatial coupon deposition approach. The stock solutions were made through the transfer of the
contents of a malathion ampoule to a pre-weighed GC vial, capped and weighed again. Ethanol was then
added to produce a solution of the desired concentration. The vial was then mixed for approximately 30
sec using a vortex mixer.
2.6.2 Coupon Contamination
Three types of malathion contamination were evaluated for all material/decontamination combinations:
1. Application of malathion as a thin film, applied by an airbrush technique
2. Application by microsyringe of evenly distributed low concentration droplets of diluted malathion
solution
3. Application by microsyringe of evenly distributed high concentration droplets of diluted malathion
solution.
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A Master Performance Pro Dual-Action Gravity Feed Airbrush with a 0.2 mm nozzle (Item #: MAS G-233-
SET, TCP Global, San Diego, CA), shown in Figure 2-3, was used for the thin film application of
malathion solution to the surface of the coupons.
Figure 2-3. Master Performance Pro Dual-Action Gravity Feed Airbrush
As is visible in Figure 2-2, a set of twelve 2" x 2" size coupons of the same material was uniformly
contaminated with malathion solution. An approximately 70-second long sweeping spray motion (left to
right across the twelve coupons first; then up and down across the same coupons, followed by a spray on
the circumference) was used to deliver the stock solution in a uniform manner. Upon completion of the
malathion solution application, the weight of the test tray containing the set of twelve coupons was
measured and compared against the tray weight with coupons prior to the application of the stock
solution. This weight increase was converted to applied volume using the density of ethanoi [0.789 grams
(g)/cubic centimeter (cm3)] as the main constituent of the solution. The average volume applied to a set of
twelve coupons throughout the test program was 4.0 ± 0.5 mL.
The evenly distributed low concentration and the evenly distributed high concentration droplets of diluted
malathion solution were applied using a 25 microliter (uL) syringe (P/N: 702, Hamilton, Reno, NV) and a 5
juL syringe (P/N: 7105, Hamilton, Reno, NV), respectively.
The amount and concentration of solution deposited on a set of twelve coupons is shown in Table 2-2 for
each malathion deposition method.
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Table 2-2. Contamination Solution Properties
Spatial Distribution of
Contamination
Scenario
Stock Solution
Concentration
Volume of Solution per Test
Coupon/Positive Control
Coupon
Theoretical Amount of
Malathion Applied (mg)
Even distribution-high
concentration
500 mg/mL
24 |jL (12 x 2 |jL)
12
Even distribution-low
concentration
50 mg/mL
240 mL (12x20 mL)
12
Thin Liquid Film though
an airbrush
12 mg/mL
70 seconds spray/4 mL
48
2.7 Decontamination Testing
The overall decontamination effectiveness was determined for the three malathion deposition conditions
as a function of the material type and type of decontamination spray apparatus (ESS or BPS) for a 30-min
interaction time with the test coupons (contaminated) or procedural blank coupons.
2.7.1 Decontamination Solution
Concentrated bleach solution (hereafter, "bleach") (Clorox® Concentrated Germicidal Bleach, The Clorox®
Company, Oakland, CA) was purchased from a local retail store. As per label, the bleach contains 8.25%
sodium hypochlorite. The "bleach" definition used in this report refers to this product as received without
dilution or pH adjustments. Details on the concentrated Germicidal Bleach decontamination solution are
shown in Table 2-3. Germicidal bleach was selected over other concentrated Clorox® bleach products
based on its more frequent use in biological remediation efforts.
Table 2-3. Decontamination Solution Properties
Solution
Manufacturer/
Supplier Name, Location
Active
ingredients
pH Range
Bleach (8% sodium
hypochlorite)
Clorox® Concentrated Germicidal Bleach
(The Clorox® Company), Oakland, CA, USA
Hypochlorite ion/ hypochlorous
acid /hydroxide ion [bleach
stabilizer]
11-12
2.7.2 Decontamination Approach
Two decontamination spray methods (ESS and BPS systems) were evaluated for the three
materials/malathion deposition methods. The amount of bleach applied was derived from the gain
in weight of the sample setup box (which includes the test coupons) following the application of
the bleach.
2.7.2.1 Electrostatic Sprayer
For ESS applications, a self-contained disinfection sprayer system (SC-1 electrostatic sprayer,
Electrostatic Spraying Systems ESS, Watkinsville, GA, USA), shown in Figure 2-4, was used in this study.
7
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Figure 2-4. Picture of SC-1 Electrostatic Sprayer.
This air-assisted ESS (22" height [H] x 18" wide [W] x 10.5" length [L]) produces electrically charged spray
drops that are carried to the target in a low pressure, gentle, air stream. The SC-1 ESS system is
intended for light-duty, quick disinfection and sanitization applications and compatible with most
conventional chemicals. The ESS is equipped with a patented MaxCharge™ technology electrostatic
spray gun that delivers droplets with a volume median diameter (VMD) of 40 pm at a flow rate of 3,8 liters
(L) per hour. The electrostatic charge induced by the MaxCharge™ nozzle is strong enough to allow the
droplets to move in any direction to cover surfaces homogeneously. Air-assisted electrostatic spray
technology gives more than twice the deposition efficiency of hydraulic sprayers and non-electrostatic
types of air-assisted sprayers. Prior to testing, the spray distance was set to cover the whole 12"x12" test
area. The spray volume was determined for each decontamination test by collecting the entire sprayed
volume into a graduated cylinder of the appropriate size. The ESS was used for the decontamination of
three trays at a time containing coupons with an average mass flow rate of 75.4 ± 5,8 g/min over a one
(1) min spray time, leading to an average mass loading of bleach in each tray of 25.1 ± 2.5 g. The ESS
flow rate was checked at the start and at the end of each set of spray applications and the drift, if any,
was recorded.
2.7.2.2 Electric Backpack Sprayer
An SHURFLO® SRS-600 ProPack rechargeable backpack sprayer BPS (approximately 36" H x 24" W x
6" L), SHURflo®, Cypress, CA, (Figure 2-5) was used as an alternative to a handheld sprayer. The mass
flow rate of was set to achieve a mass of bleach in each tray comparable to the ESS. The BPS was used
for the decontamination of three trays at a time containing coupons with an average mass flow rate of 607
± 68 g/min over a ten (10) second spray time, leading to an average mass loading of bleach in each tray
of 33.8 ± 7.9 g. The backpack sprayer flow rate was checked at the start and at the end of each set of
spray applications and the drift, if any, was recorded.
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Figure 2-5. Electric Backpack Sprayer
2.8 Extraction Solvent
Hexane (OrnniSolv® HX0296, EMD Millipore, Billerica, MA; or Optima™ H303, Fisher Scientific, Pittsburgh,
PA) was used as the diluting medium for both the chemical and the decontaminant. The volume of solvent
that was used in each test was dispensed via a bottletop dispenser (P/N: BRAND 4730351 US, Sigma-
Aidrich, St. Louis, MO).
2.9 Decontamination Testing
2.9.1 Test Matrix
Table 2-4 shows the test matrix containing the malathion distribution method, materials tested, and
decontamination spray type.
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Table 2-4. Building Material Surface Decontamination Test Matrix
Test ID
Chemical Contamination Scenario
Decontamination
Application
Test Material
Total # of
Coupons
E-1
Even distribution-high concentration droplets
ESS
Stainless steel
8
E-2
Even distribution-low concentration droplets
ESS
Stainless steel
8
E-3
Thin-film application
ESS
Stainless steel
8
E-4
Even distribution-high concentration droplets
ESS
Wood
8
E-5
Even distribution-low concentration droplets
ESS
Wood
8
E-6
Thin-film application
ESS
Wood
8
E-7
Even distribution-high concentration droplets
ESS
Vinyl flooring
8
E-8
Even distribution-low concentration droplets
ESS
Vinyl flooring
8
E-9
Thin-film application
ESS
Vinyl flooring
8
H-1
Even distribution-high concentration droplets
BPS
Stainless steel
8
H-2
Even distribution-low concentration droplets
BPS
Stainless steel
8
H-3
Thin-film application
BPS
Stainless steel
8
H-4
Even distribution-high concentration droplets
BPS
Wood
8
H-5
Even distribution-low concentration droplets
BPS
Wood
8
H-6
Thin-film application
BPS
Wood
8
H-7
Even distribution-high concentration
BPS
Vinyl flooring
8
H-8
Even distribution-low concentration
BPS
Vinyl flooring
8
H-9
Thin-film application
BPS
Vinyl flooring
8
Each test consisted of three test coupons (contaminated and decontaminated), three positive controls
(contaminated but not decontaminated), one procedural blank (not contaminated but decontaminated)
and a laboratory blank (not contaminated and not decontaminated). The decontamination solution was
applied 30 min following the application of the malathion. Such an amount of time was chosen to allow for
some weathering of the chemical into the material (as applicable).
2.9.2 Extraction Method for Coupons
After completion of each test, sets of twelve 2 in x 2 in coupons (test coupons or positive controls) were
carefully transferred into a custom-made extraction coupon holder made of SS wire and Teflon (Figure 2-
6). Extraction of SS and vinyl coupons occurred in a 250 mL glass beaker with 150 mL hexane.
10
-------
Figure 2-6. Stainless Steel Coupons during Extraction
The wood coupons were too thick to fit in this custom-made coupon holder. Instead, the wood coupons
were placed face up in the bottom (single layer) of a 400 ml_ beaker to which 150 rnL hexane was added.
Once all coupons of the set were placed in individual beakers with hexane, the beakers were covered
with aluminum foil and sonicated at 40 kilohertz (kHz) for 10 min. The temperature of the water in the
sonic bath was monitored at least once every 2 min. If the temperature of the bath increased to more than
40 degrees Celsius (°C), the water was replaced to prevent overheating of samples/avoid excessive
evaporation of extraction solvent during sonicafion. Losses in extraction solvent following sonication were
compensated by adding solvent to the same marked level. Significant losses (more than 10%) were
documented.
After extraction, a 100 |jL aliquot of the raw extract was transferred to a 1.8 mL GC vial, preloaded with
hexane spiked with isotopically-labeled internal standards. This transfer occurred shortly after the end of
the sonication process. The additional dilution of samples reduces the chance that residual bleach may
continue to interact with the malathion in the extract.
An aliquot of 100 pL of the extract was added to a preloaded sample vial with 880 pL of hexane, 10 pL of
a 50 mg/mL d-10 malathion solution in dichloromethane (P/N DLM-76-1.2, CIL Inc, Tewksbury, MA), and
10 pL of a 50 mg/mL of Internal Standards Mixture (P/N ERS-091, Sigma-Aldrich, St. Louis, MO). The
deuterated malathion was added as a pre-injection labeled surrogate, to check for variations and
irregularities in the instrumental analysis.
All extraction samples were stored at 4 °C ± 3 °C until analysis by GC/MS. Vials were marked at the
solvent level so that sample integrity could be maintained by verification of the solvent level by the
EPA/NRMRL Organic Support Laboratory, who conducted the GC/MS analyses.
2.10 Sample Identification
Each sample was identified by a description of the technology tested and a unique sample number. Table
2-5 specifies the sample identification.
11
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Table 2-5. Sample Identification
Coupon Identification: 67-A#-B-CC(CC)-DD(x min)-SS-N
ID
Code
Description
A# Test ID
E1
Test ID per Table 2-4, Neutralization test
would be N1, N2, etc...
B Material Type
S
Stainless steel
W
Wood
F
Vinyl flooring
CC (CCJ Process type
EE
Extraction efficiency testing
BC (NT)
Neutralization testing
BC (ST)
Solution testing bleach
BC (ES)
Decontamination bleach via ESS
BC (HS)
Decontamination bleach via BPS
DD x min
30
Processing Time (30 min)
SS Sample Type
PC
Positive control coupon/sample
TC
Test (decontaminated) coupon/sample
PB
Procedural Blank
LB
Laboratory Blank
N Sample Number
N
Replicate number
2.11 Chemical Analysis
2.11.1 GC/MS Analysis
Extraction samples were analyzed using a Thermo 1310 Gas Chromatograph (Thermo Scientific,
Waltham, MA, USA) equipped with a low resolution Thermo ISQ Mass Spectrometer. The GC/MS was
operated in alternating selected ion monitoring (SIM) mode and full scan mode. The 173 m/z (SIM target
ion) was used to quantify the amount of malathion in the extract. Qualifier ions were 125 m/z. and 127
m/z. The GC was equipped with a 60 meter DB-5 column (0.25 mm x 0.25 jjm) (J&W/Agilent, USA). The
GC was programmed from the initial temperature of 110 °C, followed by a ramp at 25 °C/min to an
intermediate one min hold at 215 °C followed by a ramp at 30 °C/min to a final temperature of 300 °C with
a hold of 7.25 min. The carrier gas was helium at a 1.3 mL/min flow rate. The temperature of the injection
12
-------
port was 150 °C, and the transfer line temperature was 250 °C. Thermo Xcalibur software was used for
data acquisition and processing.
Nine calibration standards were prepared and injected onto the GC/MS system prior to the malathion
extract analysis. The composition and concentrations of calibration standards are given in Table 2-6. The
initial calibration for the malathion and phenanthrene d-10 as the internal standard (IS) was completed
with phenanthrene d-10 at 1000 picograms (pg)/uL and the malathion ranged from 100 pg/uL to 10000
pg/uL. The calibration curve was analyzed with every batch of samples.
Table 2-6. Calibration Solutions (CS1-CS9) Concentrations
ICAL-1
ICAL-2
ICAL-3
ICAL-4
ICAL-5
ICAL-6
ICAL-7
ICAL-8
ICAL-9
pg/ ml
Malathion
100
500
1000
2000
3000
4000
5000
7500
10000
d-10 phenanthrene (IS)
1000
1000
1000
1000
1000
1000
1000
1000
1000
2.11.2 GC/MS Detection Limit
Method detection limit (MDL) values were determined in accordance with SW 846 [2] guidelines for
determination of method detection limits. The lowest internal calibration standard (ICAL-1) was injected
seven times. The standard deviation from these data was multiplied by the appropriate one-sided 99% t-
statistics value [2.998] for seven samples to determine the MDL. The instrumental MDL was calculated to
be 2 pg/ |jL. For samples where the malathion signal was less than a signal to noise ratio of three, the
concentration was reported as ND (non-detect). The signal to noise ratio of the lowest calibration
standard was approximately 50. Therefore the precision of the data was better than the signal to noise
ratio, and the MDL should therefore be considered to be 6 pg/uL based on the signal to noise ratio of the
lowest calibration point.
2.11.3 GC/MS Quantification
Sample concentrations were assessed by using an internal standard (IS) method as outlined in SW 846
[2], The internal standard used was d-10 phenanthrene.
A response factor (RF) was calculated for each calibration point with the following equations:
RP = x Sil. (3)
A is Ccai
where Acai = Area of malathion calibration point,
Ccai = Concentration of the malathion calibration point,
Ais = Area of the d-10 phenanthrene internal standard, and
Cis = Concentration of the d-10 phenanthrene internal standard.
The calculated response factors from each malathion calibration point were averaged, and this average
response factor (RF) was used to calculate the concentration of the samples.
The sample concentration equation used is:
13
-------
where Cx = Concentration of the sample, and
Ax = Area of malathion in the sample.
A malathion-d10 internal standard was used to verify the injection sequence and to ensure that the
correct amount was injected, and that no sample degraded in the injection port.
14
-------
3 Results and Discussion
The results for the decontamination efficacy of bleach as a target decontaminant for the removal
of malathion as applied to three building materials (SS, wood, and vinyl) are presented in the
following subsections. The results are presented for the decontamination spray methods (ESS
and BPS) for all three materials/malathion deposition methods (thin-film application, even-
distributed-low droplets, and evenly distributed high concentration droplets).
The decontamination efficacy for each test coupon was determined by measuring the amount of residual
chemical on a specific test coupon and comparing the residual chemical to the average values of the
positive controls that were subjected to the same malathion deposition method. Positive control values for
each material were evaluated to determine the precision with which deposition and analysis of malathion
occurred.
3.1 Shakedown of Airbrush Delivery Method
The initial airbrush application was conducted using a solution of 6 mg/mL malathion in ethanol. The
recovered malathion amount (by GC/MS analysis) was 5.0 ± 0.8 mg per set of twelve SS coupons
(triplicate sets) after an approximately 50 sec spraying time while the theoretical amount was 16.1 ± 1.2
mg per set of twelve SS coupons. Extraction efficiencies were therefore only 24-35%, which are much
lower than the anticipated 70-95% range for extraction of malathion from a SS coupon when deposited as
a discrete droplet. This apparent lower extraction efficiency may be attributed to either an overspray of
the airbrush into the tray resulting in a bias in the spray volume applied per set of coupons or a lower than
anticipated extraction efficiency of the extraction method itself. A detailed investigation to identify this
lower recovery was not conducted. To compensate for the losses, the malathion concentration was
doubled to 12 mg/mL, and the spray time was extended to approximately 70 sec per set of twelve
coupons. Although the theoretical amount applied was now approximately 48 mg per twelve coupons, the
amounts extracted were in the 8-12 mg range per twelve coupons, similar to the discrete malathion
droplet deposition amounts.
3.2 Electrostatic Sprayer Decontamination Results
3.2.1 Thin Film Deposition Method
The results of the airbrush malathion solution deposition technique for the three building materials (SS,
wood, and vinyl coupons) are illustrated in Figures 3-1 through 3-3, respectively. As expected, the
malathion solution remains on the surface of the SS coupons and to a certain extent on the vinyl coupons
but not on the wood coupons due to the absorption capacity of this material. After the 30 or 60 min
"weathering" time, the ethanol had evaporated, and the coupons were dry.
A better than 97.5% efficacy was observed following decontamination of all materials with bleach (30 min
interaction time) using the ESS (Table 3-1). Decontamination of SS led to malathion non-detects in the
test coupon extracts resulting in a better than 99.95% efficacy based on a method detection limit of 6
pg/jjL (equivalent to 9 jjg in the coupons extract).
15
-------
Figure 3-1. Stainless Steel Material Coupons Contaminated using an Airbrush
J
Figure 3-2. Wood Material Coupons Contaminated using an Airbrush
mjfai
: M
Iv
CI
A
HEfffii
i
Figure 3-3. Vinyl Material Coupons Contaminated using an Airbrush
16
-------
Table 3-1. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Material
Coupons Contaminated via an Airbrush
Stainless Steel
Test Results
Amount of Malathion
Solution Sprayed
Mass of
Malathion
Sprayed
(mg)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery (%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied
(g)
Sample ID
Mass (g)
Volume
(mL)
P re-
Decontamination
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-E3-S-BC(ES)-30-PB-1
-
-
-
-
ND
20.1
67-E3-S-BC(ES)-30-TC-1
2.507
3.178
38.1354
25.4 x103
ND
99.95
24.2
67-E3-S-BC(ES)-30-TC-2
3.569
4.523
54.2783
36.2 x103
ND
99.95
26.2
67-E3-S-BC(ES)-30-TC-3
3.586
4.545
54.5414
36.4 x103
ND
99.95
24.9
67-E3-S-BC(ES)-30-PC-1
3.419
4.334
52.0030
34.7 x103
11.9 x103
34.3
67-E3-S-BC(ES)-30-PC-2
3.387
4.292
51.5057
34.3 x103
10.6 x103
31.0
67-E3-S-BC(ES)-30-PC-3
3.437
4.357
52.2798
34.9 x103
10.8 x103
31.0
67-E3-S-BC(ES)-30-LB-1
-
-
-
-
ND
Average1
3.32
4.20
50.46
33.6 x10s
11.1x10s
32.1
99.95
25.1
Standard Deviation (SD)1
0.41
0.51
6.16
4.1x10s
0.7 x10s
1.9
0.00
1.0
Wood
67-E6-W-BC(ES)-30-PB-1
-
-
-
ND
25.0
67-E6-W-BC(ES)-30-TC-1
3.199
4.054
48.6540
32.4 x103
251
97.48
21.8
67-E6-W-BC(ES)-30-TC-2
2.736
3.468
41.6137
27.7 x103
166
98.34
26.9
67-E6-W-BC(ES)-30-TC-3
3.414
4.326
51.9163
34.6 x103
246
97.54
23.2
67-E6-W-BC(ES)-30-PC-1
3.449
4.371
52.4578
35.0 x103
10.2 x103
29.1
67-E6-W-BC(ES)-30-PC-2
3.088
3.913
46.9612
31.3 x103
10.4 x103
33.2
67-E6-W-BC(ES)-30-PC-3
2.933
3.717
44.6084
29.7 x103
9.4 x103
31.7
67-E6-W-BC(ES)-30-LB-1
-
-
-
Average1
3.14
3.98
47.70
31.8 x10s
10.0 x10s
31.3
97.79
24.0
SD1
0.28
0.35
4.21
2.8 x10s
0.5 x10s
2.1
0.49
2.6
Vinyl
67-E9-F-BC(ES)-30-PB-1
-
-
-
ND
22.0
67-E9-F-BC(ES)-30-TC-1
3.330
4.220
50.6449
33.8 x103
14
99.81
24.2
67-E9-F-BC(ES)-30-TC-2
2.864
3.630
43.5650
29.0 x103
14
99.81
27.1
67-E9-F-BC(ES)-30-TC-3
2.927
3.710
44.5141
29.7 x103
2
99.92
25.7
67-E9-F-BC(ES)-30-PC-1
2.841
3.601
43.2061
28.8 x103
5.8 x103
20.0
67-E9-F-BC(ES)-30-PC-2
2.868
3.635
43.6228
29.1 x103
8.0 x103
27.4
67-E9-F-BC(ES)-30-PC-3
3.238
4.103
49.2395
32.8 x103
8.7 x103
26.4
67-E9-F-BC(ES)-30-LB-1
-
-
-
Average1
3.01
3.82
45.80
30.5 x10s
7.5 x10s
24.6
99.85
25.7
SD1
0.21
0.27
3.27
2.2 x10s
1.5 x10s
4.0
0.07
1.5
ND: Non-Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
3.2.2 Evenly Distributed Low Concentration Droplet Deposition Method
The results of the evenly distributed low concentration malathion solution droplet (nominal 20 |jl_ volume)
approach for the three building material (SS, wood, and vinyl) coupons are illustrated in Figures 3-4
through 3-6, respectively. The spiked area with the malathion solution is visibly shown at the center of
each coupon of the SS material, but not on the wood and the vinyl coupon materials.
17
-------
The results for the decontamination efficiency of the evenly distributed low concentration deposition
method mirror the results of the decontamination of maiathion deposited on the coupons as a thin film. A
better than 92.9% efficacy was observed following decontamination of all materials with bleach (30 min
interaction time) using the ESS (Table 3-2). Decontamination of SS led to maiathion non-detects in the
test coupon extracts, resulting in a better than 99.90% efficacy considering a method detection limit of 6
pg/|jL.
Figure 3-4. Evenly Distributed Low Concentration Droplet Deposition Method on SS Material
Coupons
Figure 3-5. Evenly Distributed Low Concentration Droplet Deposition Method on Wood Material
Coupons
18
-------
Figure 3-6. Evenly Distributed Low Concentration Droplet Deposition Method on Vinyl Material
Coupons
19
-------
Table 3-2. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Evenly
Distributed Low Concentration Droplet Deposition Method on Material Coupons
Stainless Steel
Test Results
Amount of Solution Spiked
(Malathion @ 50 mg/mL)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery (%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Volume
(mL)
Mass (mg)
Pre-
Decontamination
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-E2-S-BC(ES)-30-PB-1
-
-
-
ND
24.8
67-E2-S-BC(ES)-30-TC-1
240 |jL
(12 spots x
20 |JL)
12
8000
ND
99.90
22.5
67-E2-S-BC(ES)-30-TC-2
ND
99.90
24.3
67-E2-S-BC(ES)-30-TC-3
ND
99.90
20.5
67-E2-S-BC(ES)-30-PC-1
6.4 x103
80
67-E2-S-BC(ES)-30-PC-2
6.2 x103
77
67-E2-S-BC(ES)-30-PC-3
6.2 x103
78
67-E2-S-BC(ES)-30-LB-1
-
-
-
ND
Average1
6.3 x103
78
99.90
22.4
SD1
0.14 x10s
2
0.00
1.9
Wood
67-E5-W-BC(ES)-30-PB-1
-
-
-
ND
28.7
67-E5-W-BC(ES)-30-TC-1
240 (jL
(12 spots x
20 |JL)
12
8000
245
93.57
27.5
67-E5-W-BC(ES)-30-TC-2
100
97.37
29.7
67-E5-W-BC(ES)-30-TC-3
151
96.03
25.7
67-E5-W-BC(ES)-30-PC-1
3.3 x103
41
67-E5-W-BC(ES)-30-PC-2
4.0 x103
49
67-E5-W-BC(ES)-30-PC-3
4.2 x103
52
67-E5-W-BC(ES)-30-LB-1
-
-
-
ND
Average1
3.8 x103
48
95.66
27.6
SD1
0.5 x103
6
2.00
2.0
Vim
/I
67-E8-F-BC(ES)-30-PB-1
-
-
-
ND
27.2
67-E8-F-BC(ES)-30-TC-1
240 (jL
(12 spots x
20 ML)
12
8000
98
98.44
25.9
67-E8-F-BC(ES)-30-TC-2
829
86.81
28.6
67-E8-F-BC(ES)-30-TC-3
416
93.39
26.4
67-E8-F-BC(ES)-30-PC-1
6.3 x103
78
67-E8-F-BC(ES)-30-PC-2
6.3 x103
78
67-E8-F-BC(ES)-30-PC-3
6.4 x103
79
67-E8-F-BC(ES)-30-LB-1
-
-
-
ND
Average1
6.3 x10s
79
92.88
27.0
SD1
0.05 x10s
1
5.83
1.4
ND: Non-Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
3.2.3 Evenly Distributed High Concentration Droplet Deposition Method
The results of the evenly distributed high concentration malathion solution droplet approach for the three
building material (SS, wood, and vinyl) coupons are illustrated in Figures 3-7 through 3-9, respectively.
The spiked area with the malathion solution (nominal 2 |jl_ volume) is visibly shown and concentrated at
the center of each coupon of the SS material, but not visible on the wood and the vinyl coupon materials.
20
-------
The results for the decontamination efficiency of bleach using the ESS (Table 3-3) on the wood material
with an evenly distributed high concentration deposition is relatively iower (71 ± 4%) than the
decontamination efficiencies encountered for wood material coupons contaminated via the thin film
deposition method or evenly distributed low concentration deposition methods. Higher decontamination
efficacies (better than 94%) for bleach using the ESS were observed for the SS and vinyl materials.
Decontamination of the SS led to malathion non-detects in the test coupon extracts, resulting in a better
than 99.91% efficacy considering a method detection limit of 6 pg/pL. Further, for the highly concentrated
droplet deposition method, corrosion was observed on the SS coupons after the decontamination with
bleach as shown in Figure 3-10. This corrosion may be attributed to the formation of various malathion-
related degradation acids at a localized high concentration resulting in corrosion of the SS material.
Figure 3-7, Evenly Distributed High Concentration Droplet Deposition Method on SS Material
Coupons
21
-------
Figure 3-8. Evenly Distributed High Concentration Droplet Deposition Method on Wood Material
Coupons
f
A
Figure 3-9. Evenly Distributed High Concentration Droplet Deposition Method on Vinyl Material
Coupons
22
-------
Corrosion spots
Figure 3-10: Corrosion Spots on SS Material Coupons following Decontamination with Bleach
using the Evenly Distributed High Concentration Droplets Deposition Method
23
-------
Table 3-3. Test Results for Bleach Decontamination using an Electrostatic Sprayer on Evenly
Distributed High Concentration Droplet Deposition Method on Material Coupons
Stainless Steel
Test Results
Amount of Solution Spiked
(Malathion @ 500 mg/mL)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery (%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Volume
(mL)
Mass (mg)
Pre-
Decontami nation
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-E1 -S-BC(ES)-30-PB-1
-
-
-
ND
22.0
67-E1-S-BC(ES)-30-TC-1
24 |jL
(12 spots x
2pL)
12
8000
ND
99.911
21.8
67-E1-S-BC(ES)-30-TC-2
2
99.91
25.6
67-E1-S-BC(ES)-30-TC-3
2
99.9l|
19.3
67-E1 -S-BC(ES)-30-PC-1
6.9 x103
86
67-E1 -S-BC(ES)-30-PC-2
6.6 x103
83
67-E1 -S-BC(ES)-30-PC-3
6.8 x103
85
67-E1 -S-BC(ES)-30-LB-1
~
-
-
ND
Average1
6.7 x103
84
99.91
22.2
SD1
0.1 x103
2
0.00
3.2
Wood
67-E4-W-BC(ES)-30-PB-1
~
-
-
ND
24.4
67-E4-W-BC(ES)-30-TC-1
24 pL
(12 spots x
2pL)
12
8000
1.1 x103
74.2
26.9
67-E4-W-BC(ES)-30-TC-2
1.4x103
67.3
27.9
67-E4-W-BC(ES)-30-TC-3
1.2 x103
71.7
22.5
67-E4-W-BC(ES)-30-PC-1
4.3 x103
54
67-E4-W-BC(ES)-30-PC-2
4.3 x103
54
67-E4-W-BC(ES)-30-PC-3
4.1 x103
51
67-E4-W-BC(ES)-30-LB-1
-
-
-
ND
Average1
4.2 x103
53
71.1
25.8
SD1
0.1 x103
2
3.6
2.9
Vinyl
Test Results
Amount of Solution Spiked
(Malathion @ 500 mg/mL)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery (%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Volume
(mL)
Mass (mg)
Pre-
Decontami nation
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-E7-F-BC(ES)-30-PB-1
-
-
-
ND
21.0
67-E7-F-BC(ES)-30-TC-1
24 |jL
(12 spots x
2pL)
12
8000
0.8 x103
88.0
25.4
67-E7-F-BC (ES)-30-TC-2
0.3 x103
95.7
27.7
67-E7-F-BC (ES)-30-TC-3
0.1 x103
98.6
26.6
67-E7-F-BC(ES)-30-PC-1
7.0 x103
87
67-E7-F-BC (ES)-30-PC-2
6.4 x103
80
67-E7-F-BC (ES)-30-PC-3
6.7 x103
84
67-E7-F-BC(ES)-30-LB-1
-
-
-
ND
-
Average1
6.7 x103
84
94.1
26.6
SD1
0.3 x103
4
5.5
1.2
ND: Non-Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
24
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3.3 Backpack Sprayer Decontamination Results
3.3.1 Thin Film Deposition Method
The decontamination efficacy of the bleach, dispensed via an electrical backpack sprayer, mirrors the
results of the ESS for all three building materials (SS, wood, and vinyl) contaminated via the airbrush
technique. A greater than 97% efficacy was observed following decontamination of all three materials with
bleach (30 min interaction time) using the BPS as shown in Table 3-4. Decontamination of SS led to non-
detects for malathion in all test coupon extracts. Considering a method detection limit of 6 pg/|jL
(equivalent to 9 jjg in the coupon extract), the efficacy (for SS) was better than 99.93%.
3.3.2 Evenly Distributed Low Concentration Droplets Deposition Method
The decontamination efficiency of bleach to decontaminate the evenly distributed low concentration
malathion deposition for the wood material coupons (88.9 ± 4.7%) is lower than the decontamination
efficiency when contamination occurred via the thin film deposition method using the backpack sprayer
(98.6 ± 1.0%). For similar material/deposition, the ESS showed relatively higher decontamination
efficiency (95.7 ± 2%) than with the BPS. For the vinyl and SS material, the difference in the effects of
the decontamination method (BPS versus ESS) is statistically insignificant. Near complete
decontamination for vinyl (96.7 ± 2.8%) to full decontamination forSS material (better than 99.90%) was
observed for the bleach using the backpack sprayer (Table 3-5).
3.3.3 Evenly Distributed High Concentration Droplet Deposition Method
The results for the decontamination efficiency of the evenly distributed high concentration malathion
deposition is relatively lower for the wood material coupons (61.1 ± 7.7%) and for the vinyl coupons (78 ±
11%) than the decontamination efficiencies encountered for the respective materials contaminated via the
thin film deposition method using the BPS decontamination approach. For the similar material/deposition,
the ESS was shown to be more efficient than the BPS with efficiencies of 71 ± 4% for the wood material
and 94 ± 5% for the vinyl material, respectively. For the SS material, the ESS seems to be slightly more
effective with full decontamination (non-detects) than the backpack sprayer, but full decontamination was
not reached for one of the tests (90.7%). The results for this series oftests are shown in Table 3-6.
25
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Table 3-4. Test Results for Bleach Decontamination using a Backpack Sprayer on Material
Coupons Contaminated via an Airbrush
Stainless Steel
Test Results
Amount of Malathion
Solution Sprayed
Mass of
Malathion
Sprayed
(mg)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery
(%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Mass
(g)
Volume
(mL)
Pre-Decon
Calculated
(pg/mL)
Post Decon
Measured
(pg/mL)
67-H3-S-BC(HS)-30-PB-1
-
-
-
-
ND
46.7
67-H3-S-BC(HS)-30-TC-1
2.421
3.068
36.817
24. x103
ND
99.93
38.4
67-H3-S-BC(HS)-30-TC-2
2.691
3.411
40.934
27.3 x103
ND
99.93
46.1
67-H3-S-BC(HS)-30-TC-3
2.506
3.176
38.117
25.4 x103
ND
99.93
29.8
67-H3-S-BC(HS)-30-PC-1
2.565
3.251
39.014
26.0 x103
7.8 x103
34.3
67-H3-S-BC(HS)-30-PC-2
2.546
3.226
38.715
25.8 x103
7.5 x103
31.0
67-H3-S-BC(HS)-30-PC-3
2.634
3.338
40.061
26.7 x103
8.8 x103
31.0
67-H3-S-BC(HS)-30-LB-1
-
-
-
-
ND
Average1
2.56
3.25
38.94
26.0 x10s
8.0 x10s
31
99.93
38.1
SD1
0.10
0.12
1.45
1.0 x103
0.7 x10s
2
0.01
8.2
Wood
67-H6-W-BC(HS)-30-PB-1
-
-
-
ND
36.2
67-H6-W-BC(HS)-30-TC-1
2.508
3.178
38.141
25.4 x103
210
97.65
29.0
67-H6-W-BC(HS)-30-TC-2
2.245
2.845
34.143
22.8 x103
45
99.50
41.2
67-H6-W-BC(HS)-30-TC-3
2.514
3.186
38.237
25.5 x103
118
98.68
27.2
67-H6-W-BC(HS)-30-PC-1
2.904
3.681
44.173
29.4 x103
10.8 x103
36.8
67-H6-W-BC(HS)-30-PC-2
3.312
4.198
50.373
33.6 x103
6.5 x103
19.4
67-H6-W-BC(HS)-30-PC-3
3.029
3.839
46.070
30.7 x103
9.5 x103
31.0
67-H6-W-BC(HS)-30-LB-1
-
-
-
-
ND
Average1
2.75
3.49
41.86
27.9 x10s
9.0 x10s
29
98.6
32.5
SD1
0.40
0.50
6.03
4.0 x10s
2.2 x10s
9
1.0
7.6
Vinvl
67-H9-F-BC(HS)-30-PB-1
-
-
-
ND
32.9
67-H9-F-BC(HS)-30-TC-1
2.196
2.783
33.396
22.2 x103
288
95.67
26.7
67-H9-F-BC(HS)-30-TC-2
2.444
3.097
37.170
24.8 x103
248
96.26
37.2
67-H9-F-BC(HS)-30-TC-3
2.026
2.568
30.820
20.5 x103
35
99.48
23.1
67-H9-F-BC(HS)-30-PC-1
2.188
2.773
33.281
22.2 x103
7.5 x103
33.7
67-H9-F-BC(HS)-30-PC-2
2.126
2.694
32.333
21.6 x103
4.9 x103
22.5
67-H9-F-BC(HS)-30-PC-3
2.269
2.876
34.517
23.0 x103
7.6 x103
33.0
67-H9-F-BC(HS)-30-LB-1
-
-
-
Average1
2.21
2.80
33.59
22.4 x10s
6.6 x10s
29.7
97.1
29.0
SD1
0.14
0.18
2.15
1.4 x10s
1.5 x10s
6.2
2.2
7.3
ND: Non-Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
26
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Table 3-5. Test Results for Bleach Decontamination using a Backpack Sprayer on Evenly
Distributed Low Concentration Droplet Deposition Method on Material Coupons
Stainless Steel
Test Results
Amount of Solution
Spiked (Malathion @ 50
mg/mL)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery
(%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Volume
(mL)
Mass (mg)
Pre-
Decontamination
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-H2-S-BC(ES)-30-PB-1
-
-
-
-
26.2
67-H2-S-BC(ES)-30-TC-1
240 |jL
(12 spots x
20 |JL)
12
8000
1
99.90
27.0
67-H2-S-BC(ES)-30-TC-2
ND
99.90
39.1
67-H2-S-BC(ES)-30-TC-3
ND
99.90
33.5
67-H2-S-BC(ES)-30-PC-1
6.1 x103
76.3
67-H2-S-BC(ES)-30-PC-2
6.1 x103
75.7
67-H2-S-BC(ES)-30-PC-3
6.1 x103
75.7
67-H2-S-BC(ES)-30-LB-1
~
-
-
ND
Average1
6.1x10s
76
99.90
33.2
SD1
0.03x103
0
0.00
6.1
Wood
67-H5-W-BC(ES)-30-PB-1
~
-
-
ND
46.2
67-H5-W-BC(ES)-30-TC-1
240 (jL
(12 spots x
20 |JL)
12
8000
433
88.2
26.3
67-H5-W-BC(ES)-30-TC-2
230
93.7
38.5
67-H5-W-BC(ES)-30-TC-3
563
85.7
23.7
67-H5-W-BC(ES)-30-PC-1
3.3 x103
41
67-H5-W-BC(ES)-30-PC-2
3.8 x103
48
67-H5-W-BC(ES)-30-PC-3
3.9 x103
49
67-H5-W-BC(ES)-30-LB-1
-
-
-
ND
Average1
3.7 x10s
45.9
88.9
29.5
SD1
0.4 x10s
4.4
4.7
7.9
Yin}
/1
67-H8-F-BC(ES)-30-PB-1
-
-
-
ND
27.3
67-H8-F-BC(ES)-30-TC-1
240 (jL
(12 spots x
20 |JL)
12
8000
263
95.7
36.6
67-H8-F-BC(ES)-30-TC-2
13
99.8
55.4
67-H8-F-BC(ES)-30-TC-3
339
94.5
31.0
67-H8-F-BC(ES)-30-PC-1
6.1 x103
76
67-H8-F-BC(ES)-30-PC-2
6.1 x103
77
67-H8-F-BC(ES)-30-PC-3
6.1 x103
76
67-H8-F-BC(ES)-30-LB-1
-
-
-
ND
Average1
6.1x10s
76.5
96.7
41.0
SD1
0.01 x10s
0.1
2.8
12.8
ND: Non Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
27
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Table 3-6. Test Results for Bleach Decontamination using a Backpack Sprayer on Evenly
Distributed High Concentration Droplet Deposition Method on Material Coupons
Stainless Steel
Test Results
Amount of Solution
Spiked (Malathion @ 500
mg/mL)
Concentration of Malathion in the
Sample Extract (Test/Controls)
Control
Sample
Malathion
Mass
Recovery
(%)
Decontamination
Efficiency (%)
Amount of
Bleach
Solution
Applied (g)
Sample ID
Volume
(mL)
Mass (mg)
Pre-
Decontami nation
Calculated
(pg/mL)
Post-
Decontamination
Measured
(pg/mL)
67-H1 -S-BC(ES)-30-PB-1
-
-
-
ND
21.8
67-H1-S-BC(ES)-30-TC-1
24 |jL
(12 spots x
2ML)
12
8000
658
90.7
23.8
67-H1-S-BC(ES)-30-TC-2
ND
99.9
41.2
67-H1-S-BC(ES)-30-TC-3
ND
99.9
35.1
67-H1 -S-BC(ES)-30-PC-1
7.1 x103
89
67-H1 -S-BC(ES)-30-PC-2
7.0 x103
87
67-H1 -S-BC(ES)-30-PC-3
7.1 x103
89
67-H1 -S-BC(ES)-30-LB-1
-
-
-
ND
Average1
7.7 x103
89
96.9
33.4
SD1
0.08 x103
1
5.3
8.8
Wood
67-H4-W-BC(ES)-30-PB-1
-
-
-
ND
41.1
67-H4-W-BC(ES)-30-TC-1
24 |jL
(12 spots x
2ML)
12
8000
2.4 x103
53.4
28.4
67-H4-W-BC(ES)-30-TC-2
1.9 x103
63.2
40.9
67-H4-W-BC(ES)-30-TC-3
1.7 x103
66.8
28.8
67-H4-W-BC(ES)-30-PC-1
5.0 x103
63
67-H4-W-BC(ES)-30-PC-2
4.8 x103
60
67-H4-W-BC(ES)-30-PC-3
5.7 x103
71
67-H4-W-BC(ES)-30-LB-1
-
-
-
1.4
Average1
5.2 x103
65
61.1
32.7
SD1
0.4 x103
5
7.7
7.1
Vinyl
67-H7-F-BC(ES)-30-PB-1
-
-
-
ND
35.3
67-H7-F-BC(ES)-30-TC-1
24 [JL (12
spots x 2
ML)
12
8000
2.3 x103
69.0
24.1
67-H7-F-BC(ES)-30-TC-2
0.8 x103
89.8
41.7
67-H7-F-BC(ES)-30-TC-3
1.8x103
75.8
35.9
67-H7-F-BC(ES)-30-PC-1
7.7 x103
96
67-H7-F-BC(ES)-30-PC-2
7.8 x103
98
67-H7-F-BC(ES)-30-PC-3
7.1 x103
88
67-H7-F-BC(ES)-30-LB-1
-
-
-
ND
Average1
7.5 x103
94
78.2
33.9
SD1
0.4 x103
5
10.7
9.0
ND: Non-Detect; set to 6 pg/|jL (instrument MDL) in calculation of decontamination efficacy.
1 Average and SD as calculated for shaded values.
28
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4 Quality Assurance/Quality Control
This project was performed under an approved Category III Quality Assurance Project Plan (QAPP):
Decontamination Solution Methods for Toxic Industrial Chemicals, Part A: Assessment of
Decontamination Application and Sampling Method, Task A, approved by the U.S. EPA NHSRC Quality
Assurance (QA) Representative (July 2014), and related amendments.
4.1 Quality Assurance and Quality Control Checks
Uniformity of the test materials was a critical attribute to assuring reliable test results. Samples and test
chemicals were maintained to ensure their integrity. Samples were stored away from standards or other
samples that could cause cross-contamination.
Supplies and consumables were acquired from reputable sources and were National Institute of
Standards and Technology (NIST)-traceable when available. Supplies and consumables were examined
for evidence of tampering or damage upon receipt and prior to use, as appropriate. Supplies and
consumables showing evidence of tampering or damage were not used. All examinations were
documented and supplies were appropriately labeled. Project personnel checked supplies and
consumables prior to use to verify that they met specified task quality objectives and did not exceed
expiration dates.
4.2 Data Quality Acceptance Criteria Verification
The Data Quality Objectives (DQOs) define the critical measurements needed to address the stated
objectives and specify tolerable levels of potential errors associated with simulating the prescribed
decontamination environments. The following measurements were deemed to be critical to accomplish
part or all of the project objectives:
S Volume of malathion solution applied to the coupon surface
S Decontamination exposure time
S Volume of decontamination solution
S Volume of extraction solvent
S Residual chemical quantification of the coupon extractions.
Non-critical measurements were:
S Temperature measurements of bleach prior to each test.
S Free Available Chlorine (FAC) and pH of the bleach decontamination solution prior to each test
S Sonicator temperature.
4.2.1 Control of Monitoring and Measuring Devices
Standard operating procedures for the maintenance and calibration of all laboratory equipment were in
place. All equipment (e.g., pipettes, pH meter, microbalances, FAC titrator) and monitoring devices (e.g.,
thermometer, hygrometer, stopwatches) used at the time of evaluation was verified as being certified
29
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calibrated or having the calibration validated by EPA's on-site (Research Triangle Park, NC) Metrology
Laboratory at the time of use. The data quality results for the critical parameters are listed in Table 4-1
Table 4-1. Data Quality Objectives and Results for Test Measurements.
Parameter
Equipment
QC Acceptance Criteria
Results
Extraction Solvent
Volume
BRAND® Dispensette ©Organic
bottletop dispenser
± 0.5% precision
All these instruments were
verified as being certified by
the respective manufacturer
Volume of Malathion
Applied
Hamilton Microsyringe for Evenly
Distributed High Concentration
Droplet Deposition Method
± 0.04 |jL1 precision
Hamilton Microsyringe for Evenly
Distributed Low Concentration
Droplet Deposition Method
± 0.20 |jL1 precision
Mass of Malathion
Applied
Airbrush: Balance with daily
calibration check using standard
weights
Balance precision at least 0.1 x
lowest measured value
Balance calibration checks
passed Quality Control (QC)
requirement
Decontamination
Solution Mass
Determined by mass balance
with daily calibration check using
standard weights
Balance precision at least 0.1 x
lowest measured value
Balance calibration checks
passed QC requirement
(Decontamination) Time
NIST stopwatch
1 second of NIST time after a 1-
min time check
Accuracy of stopwatch clock
was acceptable
Residual Malathion
Quantification of the
Coupon Extractions
GC/MS
Continuing Calibration
Verification (CCV) Drift
See Section 4.3
Malathion on Positive
Control
Extraction, GC/MS analysis
The mean percent recovery for
malathion added to a coupon
used to determine recovery must
fall within the range of 70%-
110% and have a coefficient of
variation of <30% between
replicates (for same material)
Extraction for Evenly
Distributed High and Low
Concentration Droplet
Deposition distributions
passed QC criteria;
airbrush/thin film application
failed criteria. See Section
4.4.1
Malathion on Laboratory
Blank
Extraction, GC/MS analysis
Laboratory blanks should have
less than 1 % of the amount of
malathion compared to that
found on positive controls
All laboratory blanks (except
for one) were blank (no
malathion detected). One
exception was within the
acceptable range (0.04%)
Malathion on Procedural
Blank
Extraction, GC/MS analysis
Procedural blanks should have
less than 5% of the amount of
malathion compared to that
found on positive controls
All were within the
acceptable range
1 Based on trueness and precision Statement of Conformance from the Hamilton Company Website.
4.3 GC/MS Calibrations
Malathion analyses were performed by the EPA Organic Support Laboratory using a GC/MS instrument.
The analytical equipment used to determine the amount of malathion on the coupons was calibrated at
the time of use and at the frequency specified in Table 4-2.
30
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Table 4-2. Equipment Calibration Schedule
Equipment
Frequency and Approach
GC/MS
At the beginning of each batch of test samples (nine-point calibration curve) and a
calibration verification standard (at least every 10 samples and at the end of a batch of
samples)
For GC/MS, one (mid-range, ICAL-4) calibration curve standard was analyzed following the calibration
curve standards and following at least every ten samples and at the end of each batch of samples. The
response to ICAL-4 within 15% of nominal concentration was acceptable. Samples analyzed prior to or
following this mid-range calibration standard that were outside of acceptance limits were re-analyzed.
A nine-point calibration was used for each batch of samples for analysis of malathion with a lower level of
approximately 100 pg/|jL and an upper range of approximately 10000 pg/|jl_. The GC/MS calibration
curves met the following performance requirements:
• R2 greater than 0.999
• % bias for the lowest standard less than 25%
• % bias for the remaining standards less than 15%.
4.4 Other QC Chemical Analyses
Quality control efforts conducted during decontaminant testing included positive control coupons
(contaminated, not decontaminated), procedural blanks (not contaminated, decontaminated), laboratory
blanks (not contaminated, not decontaminated), and spike control samples (laboratory quality indicators).
4.4.1 Positive Control Recoveries
Positive control values for each material were evaluated to determine the precision with which deposition
and analysis of malathion occurred. The standard deviation of this mean was used in the calculation of
error in efficacy values (mean positive control value was used in the calculation of the decontamination
efficacy). The recovered amounts of malathion (in triplicate) for each decontamination test are shown in
Tables 3-1 through 3-6 and summarized in Table 4-3 for all the malathion deposition methods/types of
material tested combinations. The mean recovery of the amount of malathion as applied to a set of
twelve coupons using the described extraction procedure and solvents was between 25 and 31% for the
airbrush deposition method tests for all the testing materials. This value was well outside the set target
recovery of better than 70% (but not more than 110%). The low recovery was attributed to losses during
the application procedure and not necessarily due to the analytical extraction approach that was used.
The impact of not meeting the extraction criteria is minimal as this low extraction efficiency impacts both
the positive control coupons and test coupons equally. Hence, they do not significantly impact the
calculated efficacy values.
For the evenly distributed concentration droplet deposition methods, where the application losses are
minimal or non-existent, the recoveries for the SS and vinyl sets of coupons were between 76 and 94%,
well within the target set recoveries. For the evenly distributed concentration droplet deposition
31
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method/wood combination, the recoveries were between 46 and 65% due to the absorptive nature of the
material. The impact of this lower extraction efficiency for wood should be minimal as explained above.
Precision, listed in Table 4-3, was calculated for each data set to describe agreement among the
recoveries of the positive controls. Precision is calculated as the percent deviation of the standard
deviation from the average mean of the recovery. The results indicate better reproducibility of the data for
the evenly distributed concentration droplet deposition methods (0.2 - 12% range) compared to the
airbrush deposition method (6 -31% range) due to the variability of the malathion losses when applying
the airbrush method to contaminate a set of coupons.
Table 4-3. Quality Assurance Measurements
Deposition Method /
Decontamination Approach
Material Type
Extraction
Efficiencies
Positive Controls
(%,± SD)
Precision of
Extraction
Efficiency Positive
Controls (%)
Procedural
Blanks
Laboratory Blanks
(% of Positive
Control Amount)
Airbrush/ESS
Stainless Steel
32 ±2
6
ND
ND
Wood
31 ±2
7
ND
ND
Vinvl
25 ±4
16
ND
ND
Airbrush/BPS
Stainless Steel
31 ±2
7
ND
ND
Wood
29 ±9
31
ND
ND
Vinvl
30 ±6
21
ND
ND
Evenly Distributed Low Concentration
Droplet/ESS
Stainless Steel
78 ±2
2
ND
ND
Wood
48 ±6
12
ND
ND
Vinvl
79 ± 1
1
ND
ND
Evenly Distributed Low Concentration
Droplet//BPS
Stainless Steel
76 ± 0.3
0.4
ND
ND
Wood
46 ±4
10
ND
ND
Vinvl
77 ±0.1
0.2
ND
ND
Evenly Distributed High Concentration
Droplet/ESS
Stainless Steel
84 ±2
2
ND
ND
Wood
53 ±2
3
ND
ND
Vinvl
84 ±4
4
ND
ND
Evenly Distributed High Concentration
Droplets//BPS
Stainless Steel
89 ± 1
1
ND
ND
Wood
65 ±5
8
ND
0.04
Vinvl
94 ±5
5
ND
ND
4.4.2 Procedural and Laboratory Blanks
For each chemical-material type, a procedural blank was collected. The results of the procedural blanks
are listed in Table 4-3. All the procedural blank results were non-detects (< 6 pg/|jL). Recovered
chemical amounts from laboratory blanks were all non-detects except for one (1.4 pg/|jL or 0.04% of the
chemical amount recovered from the positive control for that material).
32
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5 Summary
The objective of this evaluation was to develop/demonstrate two decontamination solution delivery
systems and apply them to determine the decontamination efficacies of bleach for decontamination of
building materials that were contaminated with malathion. Three different types of malathion distributions
on the surfaces were investigated, namely, the presence of a thin uniform film, a localized low
concentration droplet; and a localized high concentration distribution.
The decontamination efficacy was evaluated utilizing an electrostatic sprayer and backpack sprayer
system. Table 5-1 summarizes the observed decontamination efficacy values.
Table 5-1. Summary of Decontamination Efficacies using ESS and BPS for Three Malathion
Deposition Distributions
ESS
Thin Film
Local Low
Local High |
Mean
SD
Mean
SD
Mean
SD
(%)
(%)
(%)
(%)
(%)
(%)
SS
>99.95
0.00
>99.90
0.00
99.91
0.00
Wood
97.79
0.49
95.66
2.00
71.06
3.61
Vinyl
99.85
0.07
92.88
5.83
94.07
5.49
BPS
Thin Film
Local Low
Local High |
Mean
SD
Mean
SD
Mean
SD
(%)
(%)
(%)
(%)
(%)
(%)
SS
>99.93
0.01
99.90
0.00
96.85
5.32
Wood
98.61
0.99
88.87
4.70
61.12
7.66
Vinyl
97.14
2.16
96.65
2.79
78.20
10.67
>: Non-detects on all test coupons; calculated efficacy based on instrument MDL of 6 pg/|jl_.
Very high decontamination efficiency (better than 99.9%) was observed using sprayed bleach on
malathion-contaminated SS material. Efficacy was independent of the type of spraying method (ESS or
BPS) and independent of the malathion deposition method (thin film, evenly distributed low concentration,
or evenly distributed high concentration). With the exception of one SS test coupon (using BPS to
decontaminate the localized high concentration malathion), all SS coupon extracts had non-detectable or
detectable amounts of malathion below the MDL following the decontamination with bleach (30 min
contact time). No difference in performance of the ESS vs. BPS can be derived from the SS efficacy data.
For the wood material, decontamination efficacies were in general significantly lower (Student's t-test p
value <0.05) than for the SS material. While decontamination with either spray system resulted in high
efficacy (98-99%) for a thin film malathion-contamination distribution, efficacies were lower for the
localized low distribution and even lower for the localized high concentration distribution pattern. For each
of these distributions, the ESS performed better than the BPS. However, differences were not statistically
different (p >0.05).
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Efficacy values for the decontamination of vinyl are between those for the SS and wood material. For thin
film and localized low concentration distribution, both sprayer systems work equally well with non-
statistically significant differences in efficacy. Although the localized high concentration distribution
yielded different efficacy values when comparing the ESS against the BPS, the differences were not
statistically significant.
A material comparison of efficacy values indicates that the decontamination of wood is in general more
difficult than the decontamination of vinyl and SS. Only on two occasions (ESS to decontaminate a thin
film or to decontaminate localized high concentration droplet distribution) were these differences
statistically significantly different (p<0.05).
In general, the ESS is shown to be equally effective as the BPS in decontaminating the three building
materials that were tested. The difference in decontamination solution spray pattern on the surface by
these two types of sprayers is apparently not a critical aspect in obtaining high efficacy. This result is not
too surprising considering that the contact time of 30 min allows for a spreading of decontamination
solution on the (horizontal) surfaces. The initial distribution is less relevant as long as the whole surface
gets "wetted".
The thin film, or evenly distributed low concentration droplets of the malathion solution application were
found to be more easily decontaminated than the evenly distributed high concentration droplets
application for wood and vinyl materials with either decontamination sprayer approach. One explanation
for this behavior is that not all applied bleach is in efficient contact with a highly localized contaminant.
Therefore, the overall decontamination reaction rate may be limited by the mass transfer rate.
As stated, the difference in decontamination solution spray pattern on the surface by the ESS or BPS
does not appear to make a significant difference in these experiments. Further research would be
required to determine whether this is true under conditions where, e.g., the amount of decontamination
liquid that is applied is (much) lower than what was applied here. This factor would be relevant when
spray systems are considered for decontamination of, e.g., personal protective equipment of first
responders when there could be a limitation in the amount of decontaminant that is available. A difference
in decontamination droplet distribution may also impact the efficacy at shorter contact times between
chemical and decontaminant, such as those seen in a personnel decontamination line.
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References
U.S. Environmental Protection Agency Report, Evaluation of Household or Industrial Cleaning Products
for Remediation of Chemical Agents, EPA report 600-R-11-055, 2011.
U.S. EPA Method SW-846. Chapter One. Quality Control.
http://www.epa.gov/epawaste/hazard/testmethods/sw846/pdfs/chap1 .pdf; last accessed September 14,
2015
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