&EPA
United States Office of Research and EPA/600/R-11/079
Environmental Protection Development January 2007
Agency Washington, DC 20460
A Literature Review of Wipe
Sampling Methods for
Chemical Warfare Agents and
Toxic Industrial Chemicals
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EPA/600/R-11/079
January 2007
A Literature Review of Wipe
Sampling Methods for Chemical
Warfare Agents and Toxic
Industrial Chemicals
Prepared by
Battelle
505 King Avenue
Columbus, Ohio 43201
Contract No. GS23F0011L-3
Task Order No. 1125
Stephen Billets
Environmental Sciences Division
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, NV 89119
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Notice
This document was prepared for the U.S. Environmental Protection Agency (EPA) under
Contract No. GS23F0011L-3, Task Order No. 1125. The document has met the EPA's
requirements for peer and administrative review and has been approved for publication. Mention
of corporation names, trade names, or commercial products does not constitute endorsement or
recommendation for use.
11
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Abstract
Wipe sampling is an important technique for the estimation of contaminant deposition in
buildings, homes, or outdoor surfaces as a source of possible human exposure. Numerous
methods of wipe sampling exist, and each method has its own specification for the type of wipe,
wetting solvent, and determinative step to be used, depending upon the contaminant of concern.
The objective of this report is to concisely summarize the findings of a literature review that was
conducted to identify the state-of-the-art wipe sampling techniques for a target list of
compounds. This report describes the methods used to perform the literature review; a brief
review of wipe sampling techniques in general; an analysis of physical and chemical properties
of each target analyte; an analysis of wipe sampling techniques for the target analyte list; and a
summary of the wipe sampling techniques for the target analyte list, including existing data gaps.
In general, no overwhelming consensus can be drawn from the current literature on how to
collect a wipe sample for the chemical warfare agents, organophosphate pesticides, and other
toxic industrial chemicals of interest to this study. Different methods, media, and wetting
solvents have been recommended and used by various groups and different studies. For many of
the compounds of interest, no specific wipe sampling methodology has been established for their
collection. Before a wipe sampling method (or methods) can be established for the compounds
discussed in this report, two steps must be taken: (1) conduct investigative research to fill in the
gaps in wipe sampling knowledge, and (2) conduct method validation to optimize the methods.
in
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IV
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Table of Contents
Chapter 1 Introduction 1
Chapter 2 Literature Search Methods 3
2.1 Literature Review 4
2.2 Search of Physical and Chemical Properties of Compounds 4
Chapter 3 General Wipe Sampling Information 7
3.1 Background 7
3.2 Environmental Applications 7
3.3 Occupational Applications 13
3.4 Homeland-Security Related Applications 13
3.5 Other Applications 14
3.6 Wipe Sampling Performance Information 14
3.7 Miscellaneous Notes on Other Surface Sampling Methods 16
3.8 Summary 18
Chapter 4 Physical and Chemical Properties 19
4.1 Chemical Agents and TICs of Interest 19
4.2 Summary 27
Chapter 5 Wipe Sampling Methods for CWAs and TICs 29
5.1 OP Pesticides/Pesticides 29
5.2 CWAs, CWA Precursors, and CWA Degradation Products 33
5.3 Rodenticides 34
5.4 Controlled Substances 34
5.5 Summary 34
Chapter 6 Summary and Data Gaps 35
6.1 Summary of Available Wipe Sampling Information for Compounds of Interest 35
6.2 Gaps 37
6.3 Conclusions 38
Chapter 7 References 39
Appendix A Chemical Structures for the Compounds of Interest A-l
List of Tables
Table 1. Summary of Resources for MSDS Information for Compounds of Interest 4
Table 2. General Uses of Wipe Sampling Techniques 8
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Table 3. Physical/Chemical Properties of CWAs - Blister Agents 20
Table 4. Physical/Chemical Properties of CWAs -Nerve Agents 21
Table 5. Physical/Chemical Properties of CWA Precursors and Degradation Products 22
Table 6. Physical/Chemical Properties of OP Pesticides and Other Pesticides 23
Table 7. Physical/Chemical Properties of Rodenticides and Controlled Substances 25
Table 8. Summary of Wipe Sampling Information Found in the Literature for the Compounds of
Interest 30
VI
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Abbreviations, Acronyms, and Symbols
ASTM American Society for Testing and Materials
CBIAC Chemical and Biological Defense Information Analysis Center
CHEERS Children's Environmental Exposure Research Study
cm centimeter
cm2 square centimeter
cm/s centimeter per second
Children's Total Exposure to Persistent Pesticides and Other Persistent
Organic Pollutants
CWA chemical warfare agent
DCM dichloromethane
EPA U.S. Environmental Protection Agency
FPD flame photometric detector
ft2 square foot
GC gas chromatography
HPLC high-performance liquid chromatography
HVS3 High Volume Small Surface Sampler
IPA isopropyl alcohol
LC liquid chromatography
m2 square meter
mL milliliter
mm millimeter
MS mass spectrometry
MSDS material safety data sheet
NERL National Exposure Research Laboratory
NHEXAS National Human Exposure Assessment Survey
NHSRC National Homeland Security Research Center
NIOSH National Institute for Occupational Safety and Heath
OP organophosphate pesticide
OPCW Organisation for the Prohibition of Chemical Weapons
OSHA Occupational Safety and Health Agency
PBDE polybrominated diphenyl ether
PBS phosphate buffered saline
PBT phosphate buffer with Tween
PCB polychlorinated biphenyl
PCP phencyclidine
PUF polyurethane foam
SSP swab sample processing
TEPP tetraethyl pyrophosphate
TIC toxic industrial chemical
TSA Transportation Security Administration
USDA U.S. Department of Agriculture
vn
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Vlll
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Acknowledgements
This report was prepared for the U.S. Environmental Protection Agency (EPA) under the
direction and coordination of Stephen Billets of the EP A's National Exposure Research
Laboratory (NERL), Environmental Sciences Division, in Las Vegas, Nevada. EPA NERL
acknowledges funding support for this project from EPA's National Homeland Security
Research Center (NHSRC), and specifically Oba Vincent and Rob Rothman for their
contributions. The EPA NERL thanks the following peer reviewers for their review of this
report: Brian Schumacher (EPA NERL); Eric Koglin (EPA NHSRC); Dan Stout (EPA NERL);
and Kevin Ashley (Centers for Disease Control and Prevention, National Institute for
Occupational Safety and Health). This report was prepared for the EPA by Battelle.
Acknowledgment is given to Stephanie Buehler, who was the Battelle lead author, and to Sarah
Attenberger, Jane Chuang, and Amy Dindal, for their contributions to the preparation of this
report.
IX
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Chapter 1
Introduction
Collection of contaminants from surfaces, referred to as "wipe sampling", is an important
technique for the estimation of contaminant deposition on a variety of surfaces, including those
in buildings, homes, outdoor areas, and hands (dermal wipes). Wipe sampling techniques are
used for environmental sampling, industrial hygiene monitoring, monitoring of remedial
processes, security monitoring, compliance monitoring, and various other related applications.
Examples of wipe sampling applications include testing of household surfaces for lead; airport
luggage screening for explosives; post-remediation sampling of methamphetamine houses;
dermal wipe sampling techniques for personal exposure to pesticides; post-decontamination
sampling; and spill clean-up verification of environmental contaminants. These are just a few of
the many applications of wipe sampling techniques that are applied by government agencies and
the private sector on any given day.
Procedures for the collection of contaminants from surfaces have several components in
common, including the wipe sampling media, the wetting solvent, and the collection technique.
However, wipe sampling procedures can vary widely, depending on the contaminant(s) of
interest and the surface to be sampled. Reliability of the sample results begins with accurate
collection of a sample for analysis. Thus, the wipe sampling procedures used for a particular
analyte on a given surface, including the proper combination of the wipe sampling components
described above, are an integral aspect of whether or not the results generated will be
representative of the contamination.
The objective of this report is to concisely summarize the findings of a literature review that was
conducted to identify the state-of-the-art wipe sampling techniques for a target list of
compounds. This report describes the methods used to perform the literature review; a historical
review of wipe sampling techniques in general; a review of chemical and physical properties of
each target analyte; an analysis of wipe sampling techniques for the target analyte list; and a
summary of the findings, including data gaps.
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Chapter 2
Literature Search Methods
2.1 Literature Review
In the first task of this project, a two-phased approach was used to conduct a literature review to
determine what is already known about wipe sampling techniques for a target list of analytes.
First, a broad search was conducted that explored what general information was available on
wipe sampling (i.e., how different organizations are using wipe sampling). This search did not
focus on the specific compounds of interest for this project, but instead focused on what wipe
sampling procedures could be found for various government agencies or other groups. Extensive
internet searching was used as the primary tool for this phase of the review process. Various
government agency websites were also searched using the available search options on that site
using keywords such as "wipes(s)" or "wiping" and "sample(s)". The following government
agency websites were included in the search: Drug Enforcement Administration, Federal Transit
Administration, Occupational Safety and Health Administration (OSHA), National Institute for
Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention, Bureau
of Alcohol, Tobacco and Firearms, Coast Guard, Consumer Product Safety Commission, U. S.
Department of Agriculture (USD A), U.S. Department of Defense, U.S. Department of Homeland
Security, U.S. Department on the Interior, Agency for Toxic Substances and Disease Registry,
Federal Aviation Administration, Transportation Security Administration (TSA), Federal Bureau
of Investigation, Food and Drug Administration, National Aeronautics and Space
Administration, National Institute of Standards and Technology, the U.S. Army Corp of
Engineers, and the U.S. Environmental Protection Agency (EPA). These agencies and
departments were selected because they seemed most likely to conduct wipe sampling for some
branch of their operations. In spite of this effort, only limited information was obtained from this
search process.
As a subset to this search, the Federal Register was explored to see if any further information
could be obtained on the agencies listed above. It was determined that this approach was not
productive as little practical information was found.
In the second phase of the literature search, information was sought on wipe sampling as it
relates to the compounds of interest. These focused searches were conducted by using databases
available through a regular library system as well as by the Chemical and Biological Defense
Information Analysis Center (CBIAC), which has special access to documents related to
chemical, biological, radiological, and nuclear technology information. Searches were
conducted using keywords similar to the following:
wipe OR wipes OR wiping AND sample OR sampling AND compound
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Each compound being investigated was included in individual searches. CBIAC searches
focused on the chemical warfare agents (CWAs) and related compounds; the library database
searches focused on the remaining compounds (pesticides and other toxic industrial chemicals
(TICs). These searches yielded more than 140 references. The references were reviewed further
for information regarding wipe sampling methodology, covering areas such as wipe material,
wetting solvent, wipe procedure, and sampling surface. As a result of this further examination,
only 39 citations were deemed relevant to this study and are included as references in this report.
As part of the overall reference collection effort, knowledgeable experts in the field of wipe
sampling were contacted and relevant references were gathered based on their suggestions and
input.
2.2 Search of Physical and Chemical Properties of Compounds
Part of the literature review also included gathering physical and chemical property information
on each of the compounds of interest. Specifically, material safety data sheets (MSDSs) were
collected from various publicly available internet sites as shown in Table 1. Information from
the MSDSs was compiled into tables in Chapter 4. When the information contained on the
MSDS seemed sparse, physical property information for a particular compound was cross-
checked using CHEMINFO (through the Canadian Centre for Occupational Health and Safety
(CCOHS)) and Ecotoxnet (http://extoxnet.orst.edu/). MSDS information from a subscription
service (OHS at www.ohsworks.com) was also used. For the CWAs, information on chemical
and physical properties was also obtained from two literature sources (1,2), in which detailed
information on these compounds had been collected and summarized. The chemical structures
for each of the compounds of interest are provided in Appendix A.
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Table 1. Summary of Resources for MSDS Information for Compounds of Interest
Compound
Chloropicrin
Dichlorvos
Dicrotophos
Dimethylphosphite
Distilled Mustard
(HD)/Mustard Gas (H)
1,4-Dithiane
Mustard (HT)
Ethyldichloroarsine (ED)
Fenamiphos
Lewisite (1)
Lewisite (2)
Lewisite (3)
Methyl parathion
Mevinphos
Nicotine
Phencyclidine
Phorate
Sarin (GB)
Soman (GD)
Cyclohexyl sarin (GF)
Strychnine
Tabun (GA)
Tetraethyl pyrophosphate
(TEPP)
Thiodiglycol
1,4-Thioxane
Trimethyl phosphite
VX
Crimidine
Methyl fluoroacetate
CAS No.
76-06-2
62-73-7
141-66-2
868-85-9
505-60-2
505-29-3
172672-28-5
598-14-1
22224-92-6
541-25-3
40334-69-8
Resource
www.e 1 .greatlakes.com/common/msdspdf/00026.pdf
ittp://www. cdc.gov/niosh/ipcsneng/neng0690.html
ittp : //pmep .cce . Cornell . edu/profile s/extoxnet/carbaryl-
dicrotophos/dicrotophos-ext.html
ittp://www.cdc.gov/niosh/ipcsneng/neng 1599.html
ittp : //www .gulfweb . org/bigdoc/report/apphd .html
http://physchem.ox.ac.uk/MSDS/DI/l,4-dithiane.html
ittp : //chppm-www . apgea. army .mil/dts/docs/detht .pdf
ittp : //environmentalchemistry . com/yogi/chemicals/cn/E
thyl%AODichloroarsine .html
ittp: //www. cdc.gov/niosh/ipcsneng/neng0483. html
http://www.uscg.mil/mlclant/KDiv/Envrn%20Hlth/IH-
MSDS/MSDS/LewisiteMSDS.doc
MSDS not available; information presented from:
ittp://www.epa.gov/opptintr/aegl/pubs/restl33.htm
40334-70-1 IMSDS not available; information presented from:
pttp://www.epa.gov/opptintr/aegl/pubs/restl33.htm
298-00-0 pttp://www.cdc.gov/niosh/ipcsneng/neng0626.html
7786-34-7 pttp://pmep.cce. cornell.edu/profiles/extoxnet/metiram-
propoxur/mevinphos-ext.html
54-1 1-5 fiittp://physchem.ox.ac.uk/MSDS/NI/nicotine.html
77-10-1 pttp://www.cerilliant.com/search.htm
(search cat no P-001)
298-02-2 pttp://www.piindustries.com/tech main.htm
107-44-8 |http://www.gulfweb.org/bigdoc/report/appgb.html
96-64-0 |http://www.gulfweb.org/bigdoc/report/appgd.html
329-99-7 IMSDS not available; information presented from:
Abercrombie, PL (September 2003)
5 7-24-9 pttp ://www .cdc .gov/niosh/ipcsneng/nengO 1 97 .html
77-8 1-6 pttp://www.gulfweb.org/bigdoc/report/appga.html
107-49-3
111-48-8
15980-15-1
ittp : //www . segulab . com/en/t_msds .htm
ittp ://www .cdc .gov/niosh/ipcsneng/neng 1601 .html
ittp://www.fluorochem.net/msds.asp?txtCatNo=001450
&x=25&y=6 (search for cat no 001450)
121-45-9 |http://www.osha.gov/SLTC/healthguidelines/trimethylp
posphite/recognition.html
50782-69-9 |http://www.gulfweb.org/bigdoc/report/appvx.html
535-89-7 |http://yosemite.epa.gov/oswer/ceppoehs.nsf/profiles/535
-89-7?opendocument
453-1 8-9 tattp://www. fluorochem.net/msds. asp ?txtCatNo=006800
|&x=29&y=10 (search for cat no 006800)
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Chapter 3
General Wipe Sampling Information
3.1 Background
Wipe sampling is one of the primary techniques for assessing surface contamination. When using
the appropriate wipe sampling media coupled with an appropriate solvent (or used dry, as
warranted), the type and amount of chemical on a particular surface can be identified by wiping a
sufficient area of the surface and analyzing the wipe. This technique is a quick and easy means
of determining what chemicals reside on a surface. Though wipe sampling is often employed,
the methods and materials associated with wipe sampling vary greatly. Most wipe sampling
procedures are a manual process, and the pressure applied for each wiping procedure could vary
significantly among field operators. Different government agencies use different wipe methods
for various compounds. Even within a particular field (such as occupational exposure
assessments), variations in wipe sampling methodologies have been reported.
In this section, the general uses of wipe sampling techniques by different government agencies,
various researchers, and studies are described in three primary areas: environmental,
occupational, and homeland security-related applications. This information is summarized in
Table 2. Performance information on wipe sampling methods is provided in Section 3.6. This
chapter is meant to provide only a brief overview of wipe sampling applications and performance
data. It is not meant to provide exhaustive coverage of all available studies but rather a synopsis
of relevant information that describes what wipe sampling methods have been performed by
various organizations to help establish the credibility of wipe sampling as a useful technique.
3.2 Environmental Applications
Wipe sampling is an integral part of the sampling protocol for many environmental assessments
including evaluating remedial progress, environmental compliance, and for human exposure
monitoring. A review of the literature for wipe sampling techniques in these areas is described in
this section.
EPA has devised wipe sampling methods for polychlorinated biphenyl (PCB) analysis (3, 4}.
This technique is used to verify PCB cleanup on hard, smooth, non-porous surfaces. In this
application, filter papers (such as Whatman 40 ashless or Whatman 50 smear tabs) or a gauze
pad are used for the wipe material. The wipes are wetted with a solvent, such as isooctane or
hexane, held with forceps or rubber gloves, and rubbed over a 100 square centimeter (cm2) area.
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Table 2. General Uses of Wipe Sampling Techniques
Compound
Pesticides
polar pesticides
malathion
2,4-D
chlorpyrifos
chlorpyrifos, diazinon
Other Organics
PCBs
Agency or Agency
Affiliation
ASTM
ASTM
EPA
ASTM
EPA, New Jersey
Department of
Environmental
Protection
New Jersey Department
of Environmental
Protection and Energy
EPA
EPA
EPA
NIOSH
general :
general :
Wipe Material
cotton gauze pads
cotton gauze pads
gauze pads
cotton gauze pads
gauze pads
gauze pads
gauze pads
gauze pads
filter paper, gauze pad
glass wool filter
filter paper
Kleenex®
Wetting Solvent
IPA
isooctane, DCM
70: 30 phosphate
buffer: acetonitrile;
IPA
isooctane
DI water
DI water
IPA
DI water
isooctane, hexane
hexane
dry, water
dry, water
Wipe Surface
smooth, non-porous;
100 cm2
smooth, non-porous;
100 cm2
uncarpeted floors,
table tops, window
sills, carpet; 850cm2
-2m2
smooth, non-porous;
100 cm2
carpet; 100 - 800
cm2
turf; 100 cm2
hard floors, hard
surfaces
window sill
hard, smooth, non-
porous; 100 cm2
hard, non-porous; 1
ft2
floors, walls; 200
cm2
floors, walls; 200
cm2
Reference
10
10
12, 15, 16
10
30
14
12
13
3,4
5
5
5
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Table 2. (continued)
Compound
PCBs
organic residues
tetrachlorophenol
chlorophenols
2,4-difertbutylphenol
2,3,7,8-
tetrachlorodibenzo-/?-
dioxin
Metals
As, Cu, Cr
Pb, Be, As, Cd, Cr, Ni
Pb
Agency or Agency
Affiliation
general :
general :
general :
ASTM
USDA
general :
general :
general :
general :
EPA
Brookhaven National
Lab/NIOSH
ASTM
general :
EPA
Wipe Material
Cloth wipes
Whatman filter paper
Whatman smear tabs
cotton gauze pads
gauze pads
gauze pads
Whatman filter paper
cotton swabs
Whatman glass microfiber
paper
TexWipe TX1009 clean room
wipe (100% polyester)
cotton gauze pads, ashless filter
paper, GhostWipes™
Disposable towellete
Wash'nDry® paper towels
Swiffer® dry and wet cloths
Wetting Solvent
octane
hexane
methanol
hexane, isooctane
IPA
NA
NA
ethanol
none
DI water, 0.9%
saline
DI water, IPA,
ethanol, methanol,
hexane
pre-moistened
pre-moistened
pre-moistened
Wipe Surface
NA
ventilation system; 1
ft2
work and tool
surfaces; 100 cm2
smooth, non-porous;
100 cm2
100 cm2
wood; 23 1 cm2
wood
rubber
laboratory surfaces;
625cm2
wood; 314 cm2
metal, plastic, glass,
wood, concrete; 100
cm2
1ft2
household surfaces;
1ft2
floors, window sills
Reference
5
5
5
10
12
5
5
5
5
6
8
7
5
9
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Table 2. (continued)
Compound
Others
methamphetamine
anthrax
Agency or Agency
Affiliation
MN State Department
of Health
WA State Department
of Health
general :
general :
Wipe Material
gauze sponge
filter paper
Swipe, Heavy Wipe, swab
rayon gauze pad, swab
Wetting Solvent
methanol
methanol
PBT
water, PBS
Wipe Surface
dry, hard, non-
porous; 100cm2
dry, hard, non-
porous; 100cm2
vinyl, tile, wood
laminate, metal; 929
cm2
hard surface
Reference
21
22
19
20
1 No particular agency was found to be affiliated with the referenced study.
NA = Not Available.
DCM = dichloromethane
IPA = isopropyl alcohol
PBT = phosphate buffer with 0.05 percent Tween
PBS = phosphate buffer saline
10
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Other PCB wipe methods are used to determine the extent of PCB contamination. PCB
contamination on walls and transformers has been determined by the National Institute for
Occupational Safety and Heath (NIOSH) using glass wool filter wipes wetted with hexane over a
1 square foot (ft2) area (5). Other studies by various researchers have used filter paper and
Kleenex®, cloth wipes, Whatman filter paper, and Whatman smear tabs as a sampling medium.
These wipes have been used dry, and saturated with octane, hexane, and methanol, respectively.
The areas wiped range from 100 cm2 to 900 cm2 (5).
Wipe sampling for metals such as lead or arsenic is also routinely done. In a wipe comparison
study to determine the dislodgeable arsenic, copper, and chromium residues on chromated
copper arsenate treated lumber, EPA used the following wipe media: a Tex Wipe TX1009 clean
room wipe (100 percent polyester) that was saturated with deionized (DI) water, the same
polyester wipe moistened with 0.9 percent saline solutions at two times the dry weight of the
wipe, and an acid-washed polyester wipe saturated with DI water, though this particular wipe
was found to contain traces of the acid wash still in the wipe (6). Wiping was done using a 1.1
kilogram disc that was approximately 8.5 centimeter (cm) in diameter, as a wiping block.
The American Society for Testing Materials (ASTM) has a lead-specific wipe sampling standard
method for collecting settled dust on surfaces in and around buildings (7). A packaged,
disposable towellette that is pre-moistened with a wetting solvent is used for the sample
collection. Overlapping "S" and "Z" patterns are used when collecting the sample from an area
of 100cm2.
The Industrial Hygiene Group at Brookhaven National Laboratory uses NIOSH Method 9100
(posted at www.cdc.gov/niosh/nmam) to determine lead and other metals in surface residue (5).
A range of wipe materials can be used. Either 2" x 2" or 4" x 4" cotton gauze pads; ashless filter
paper (1.5 to 4 inches in diameter); or pre-moistened wipes such as GhostWipes™ are
appropriate for lead, beryllium, arsenic, cadmium, chromium, or nickel sampling.
Approximately 1-2 milliliters (mL) of solvent such as DI water, isopropanol (IPA), ethanol,
methanol, or n-hexane is used with the wipe. A 100 cm2 area is supposed to be sampled by this
method. The solvent used does not appear to be critical for the metal collection, but can impact
the sampling surface and should be chosen accordingly.
Other commercially available wipes have also been used for lead sample collection.
Wash'nDry® disposable paper towels, moistened with 20 percent denatured alcohol and 1:750
benzalkanium chloride have been used to collect lead dust from general household surfaces (5).
Other researchers have used methods similar to the NIOSH Method 9100 described previously.
EPA is currently exploring the potential use of dry electrostatic cloths (Swiffer®), as well as wet
Swiffer® cleaning pads, for collecting residual dust samples after lead-based paint abatement
cleaning (9).
Sampling for organic compounds is an important component of many exposure assessments.
ASTM offers a method for taking wipe samples from smooth, non-porous surfaces for organic
compounds (10). ASTM recommends the use of sterile, surgical cotton gauze pads (7.6 cm2)
with pre-cleaning only when necessary. Wipe wetting solvents are recommended on a
compound basis. For example, for PCBs and most pesticides, isooctane is recommended (54 to
11
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80 percent recovery). Hexane can also be used in wipes for PCBs. For carbamates or polar
pesticides, IPA is an appropriate solvent for use with the wipe (84 to 96 percent recovery).
Acetone is not desirable because it can remove interfering compounds from the sampling
surface. A 100 cm2 wiping area is recommended as is 2 mL of any solvent that is used to wet the
wipe. The area should be wiped vertically and then horizontally using firm strokes with minimal
overlap.
The USDA also has a published wipe sampling method for detecting organic residues or dusts
from surfaces (11). As with the ASTM method, their technique uses a 3" x 3" sterile gauze pad
moistened with IPA. A 100 cm2 area is also sampled.
EPA has conducted multiple exposure studies where wipe sampling for organic compounds on
household surfaces played a key role in the assessment. As part of the Children's Total
Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study
assessing children's exposures to particular persistent organic pollutants, such as chlorpyrifos
and polycyclic aromatic hydrocarbons, wipe samples were taken for residues on hard floors
using pre-cleaned, 4" x 4" Johnson and Johnson (J&J) SOF-WICK gauze pads moistened with 2
mL of 75 percent IPA in DI water (72). The J&J SOF-WICK gauze pads were also used in the
National Human Exposure Assessment Survey (NHEXAS) exposure study in collecting wipe
samples for chlorpyrifos and diazinon from window sills. In this case, the wipes were moistened
with 2 mL of DI water and were also pre-cleaned with methylene chloride prior to their use (13).
Window sills were wiped in this study by wiping the length of the sill using moderately firm
pressure. After wiping the sill in one direction, the wipe was folded in on itself and the sill was
wiped in reverse.
EPA's Children's Environmental Exposure Research Study (CHEERS) pilot study also used
gauze pads for wipe sampling to determine children's exposure to various pesticides, phthalates,
polybrominated diphenyl ethers (PBDEs), and fluorinated compounds. At the time of this study,
however, the J&J SOF-WICK gauze pads had been discontinued, so an alternative, Kendall
Excilon wipes were used instead. The wipes were the same size as the J&J brand wipes and
were also pre-cleaned prior to use with dichloromethane (DCM). They were saturated with 10
mL of IPA before a sample was taken. This amount of IPA has the potential to extract more of
the compounds from the surface and sub-surface of the sample area than are otherwise available
for human contact and thus dermal absorption.
Black et al. (14) also used wipe samples for measuring dislodgeable chlorpyrifos residues on
Kentucky bluegrass turf. The wipes were pre-extracted 7.6 cm x 7.6 cm gauze pads sprayed with
DI water. A 100 cm2 area was sampled based on Occupational Safety and Health Agency
(OSHA) methods. Specifically, the area was wiped with one pad in a single direction for 10
strokes. Wipe samples recovered 1 percent to 6 percent of the initial chlorpyrifos deposit from
the turf (1 to 3 hours after application). Wipe sampling variability ranged from 37 to 74 percent
between different studies performed during the research. Within a particular study, wipe
sampling variability averaged 21.5 percent.
Nishioka et al. wiped uncarpeted floors, table tops, and window sills using J&J SOF-WICK
cotton gauze dressing sponge moistened with 2 mL of sweat stimulant (70:30 phosphate
12
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buffer:acetonitrile) (15,16). An area from 850 cm2 to 2 m2 was sampled by first wiping in one
direction, then folding the wipe in on itself, and then wiping the same area in an orthogonal
direction.
Multiple other methods of wipe samples for various compounds have been used over the years,
as noted by McArthur (5). Wooden surfaces (231 cm2) were sampled for tetrachlorophenol with
12-ply surgical pads using 10 strokes for each of four samples. Chlorophenols were also
collected from wooden surfaces using Whatman 1 filter paper (4.25 cm) with a 300 gram weight
placed on top. Surface contamination of rubber with 2,4-difertbutylphenol was determined using
ethanol-soaked cotton swabs. 2,3,7,8-tetrachlorodibenzo-p-dioxin contamination of laboratory
surfaces was found by wiping a 625 cm2 area with dry Whatman glass microfiber paper.
3.3 Occupational Applications
Wipe sampling is an important component of occupational exposure analysis. OSHA has
multiple wipe sampling methods and recommendations depending on the chemical of interest.
OSHA has developed guidelines to provide chemists with a uniform method of evaluating
surface sampling wipes (77). As part of these guidelines, information on how to properly
conduct wipe sampling is presented. Among the steps is selecting a sampling medium. OSHA
recommends the following list of media for wipe sampling: DURX 670 (polyester and cellulose),
Pro-Wipe 880 (polypropylene), Ghost Wipes (cross linked polyvinyl alcohol), AlphaWipes
(polyester), and even charcoal impregnated discs. Various wetting agents are also
recommended: DI water for metals, DI water or IPA for non-volatile organics, or other solvents
if the compound being sampled will react with water or IPA. The guidelines also indicate that
the ideal sampling surface is a smooth and non-porous, and that the sampling area should be 100
cm2.
OSHA has also prepared a chapter in their Technical Manual with more detailed information
about wipe sampling (18). Similar to the previous document, each step of the wipe sampling
procedure is discussed. Particular attention is paid to the media choice for sampling a surface. A
filter is described as the classic wipe sampling technique. Paper filters, mixed cellulose ester
filters, and smear tabs are best for metals. For things that are unstable on paper filters, polyvinyl
chloride filters are recommended. Squares of a gauze material that are used either wetted (with
solvent or water) or dry are purported to be best for organic compounds while volatile solvents
are best sampled with charcoal impregnated pads. To sample a surface for isocyanates or
aromatic amines, a filter treated with derivitizing reagent is recommended. Glass fiber filters,
either wetted or dry, are recommended for many of the chemicals that will be analyzed by gas
chromatography (GC) or high-performance liquid chromatography (HPLC).
3.4 Homeland-Security Related Applications
Over the last five years, the increased focus on homeland-security related techniques has
generated new applications for wipe sampling. For example, airport luggage is screened by wipe
sampling followed by ion mobility spectrometry analysis for explosives detection. In recent
years, the detection of anthrax has become a critical analytical need. More specifically, the
determination of whether or not any anthrax remains in a building after building decontamination
13
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has become an important use for wipe sampling. Buttner et al. (19) tested the efficiencies of
decontamination strategies for b. anthracis by taking wipe samples of vinyl tile, wood laminate,
and metal surfaces after a simulated dispersion and subsequent decontamination. Three different
kinds of wipe samples were used: (1) a Swipe (Speci-sponge) moistened with 30 mL of 0.01M
phosphate buffer with 0.05 percent Tween (PBT); (2) a Heavy Wipe (Handy Wipes) moistened
with 40 mL of PBT; and (3) a swab sample processing (SSP) kit moistened with 20 drops of
buffer. In all cases, a 929 cm2 area was sampled. For the Swipe and Heavy Wipe samplers, the
surface was sampled by wiping the area in a horizontal direction. The wipe was then turned over
and the unused surface was used to sample the same area while wiping in a vertical direction.
For the SSP kit, the foam swab was used to sample the first half of the pre-moistened surface,
then the swab was turned over and the remaining half of the surface was sampled. Removal
efficiencies were not presented for any of the methods used in this study, but all three wipe
materials collected similar levels of the b. anthracis surrogate used during testing, and similar
levels of the bacteria were obtained from all three surfaces tested.
In another study by Sanderson et al. (20), two different b. anthracis sampling methods were
tested. Wipe samples were taken using actual wipes as well as a swab. The wipe was 7.62 cm x
7.62 cm sterile rayon gauze pad that was wetted with 5 mL of sterile water. The sampling area
was first wiped using vertical strokes, the wipe was then folded in on itself and the area was
wiped using horizontal strokes. The swab was a sterile, rayon swab that was moistened with
phosphate buffered saline (PBS) at pH 7.2. Several strokes of the area were first taken with the
swab. The swab was then rotated during sampling to ensure that all of the swab was used. Dry
swab samples were also taken. Samples were collected from air ducts, machinery, window
boxes, and mail sorting bins from a postal facility (all non-porous surfaces). Wet swabs
performed better than dry, detecting b. anthracis in 54 percent vs. 14 percent of the instances.
Wipe sampling detected b. anthracis in 87 percent of the instances.
3.5 Other Applications
Illegal methamphetamine labs have become a serious problem for many cities and states. Wipe
sampling methods for methamphetamines were found for two state departments, the Minnesota
Department of Health (along with the Minnesota Pollution Control Agency) and the Washington
State Department of Health (21, 22). Though both methods used 2 mL of methanol as the
wetting solvent for their wipes, the wipe material itself was quite different for the two states.
Minnesota used a 3" x 3" general use gauze sponge while Washington used filter paper. In both
cases, a dry surface was to be sampled. The Washington State procedure specified a hard, non-
porous surface be sampled; this was implied in the Minnesota protocol. An overlapping "Z" and
"N" pattern are used for sampling.
3.6 Wipe Sampling Performance Information
The wipe sampling studies presented in this chapter mainly discuss applications of wipe
sampling. While various applications are important in verifying the validity of the technique, it
is also important to discuss and understand the validation and performance of the sampling
methods. Some studies have focused on determining performance criteria for various wipe
sampling methods.
14
-------
Chavalitnitkul et al. (23) conducted an evaluation of wipe sampling variability using lead oxide
dust as the test contaminant. This study aimed to evaluate wipe testing methods in general as
well as the OSHA wipe testing method, more specifically, for quantitative recovery and
repeatability. The study used moistened Whatman filter paper, commercial paper towels,
adhesive paper labels, and adhesive tape as wipe media. Formica (a non-porous, smooth surface)
and plywood (a rough, porous surface) were tested. Personal variations in performing wipe
sampling were first tested using 12 different individuals to collect samples. A wide variation in
removal efficiencies was found across participants, indicating potential issues in duplicating
sample results between field staff. Much of the variation was caused by the pressure applied
during sampling as well as the lack of a consistent sampling area. Removal efficiencies ranged
from 31 percent to 212 percent across the 12 samplers in this portion of the study. The degree of
sample variation decreased when the area to be sampled was measured prior to sampling, thus
allowing for a consistent sampling area across all samples.
In evaluating the different wipe media and wipe surfaces, as described earlier, Chavalitnitkul et
al. (23) found that most Whatman filter paper and moist paper towels gave similar, and good,
removal efficiencies (80 to 90 percent). The surface sampled, however, was found to have a
significant impact on the removal efficiency of the wipe sample. The smooth, non-porous
surface (Formica) showed better removal efficiencies than the rough, porous surface (plywood).
Removal efficiencies ranged from 57 percent to 91 percent across all sampling media and
various applied pressures on formica, while efficiencies ranged from 30 percent to 77 percent on
plywood. For plywood, the adhesive tapes gave better removal efficiencies than the paper towels
or Whatman filters used. Applying the maximum pressure while sampling increased the removal
efficiency of the adhesive media on both surfaces, but provided little impact for the paper towel
and Whatman filter.
As part of another lead dust study, Vostal et al. (24) evaluated the efficacy of the wipe sampling
procedure using moist, disposable paper towels on household floors. They found low variability
between wipe samples and across four different investigators, indicating that the amount of lead
obtained by these wipe samples could be reliably reproduced.
As McArthur describes (5), others have also explored the effect of wipe media, surface, and wipe
techniques on the wipe sampling collection efficiency. They have determined, as Chavalitnitkul
et al. (23) did, that wipe sampling removal efficiency decreased for rough surfaces. Variation
was also found between samples taken by different individuals when the sampling area was
estimated instead of measured.
Fenske et al. (25) evaluated the applicability of wipe sampling to determine exposure to
pesticides in indoor environments. They sampled chlorpyrifos using a surgical gauze pad wetted
with either distilled water or IPA. Wipe samples were taken on carpet and aluminum foil
surfaces. Wipe samples were taken using a modification of the OSHA method where a 100 cm2
area was wiped with three strokes in one direction, then a second gauze pad was used to wipe the
same area in an orthogonal direction. Removal efficiency was 86 percent to 96 percent from the
spiked aluminum foil samples with low variability between the different technicians taking the
samples. For wipe samples taken on carpeted surface, the variability was much higher, 40
15
-------
percent to 60 percent. Fenske et al. (25) concluded that much of this variability was related to
the deposition of the pesticide onto the carpet, not the wipe sampling itself. They further
concluded that wipe sampling provides a simple way of estimating the pesticide residues on a
surface, but precision for the method could be improved by defining the wipe area and
standardizing materials and methods.
3.7 Miscellaneous Notes on Other Surface Sampling Methods
As noted from the studies discussed in this section, wipe sampling can involve various materials
and be used on a variety of surfaces. There are a couple of related sampling techniques that
warrant mentioning here, but that do not address the surface wipe sampling that is the focus of
this report. Dislodgeable residues from carpets can be determined using wipe sampling, as
discussed previously; however, the preferred method of collecting dust samples from carpets is
using vacuum sampling. For exposure studies a High Volume Small Surface Sampler (HVS3) is
generally used for such a purpose. This is essentially a modified vacuum that uses cyclonic
action to collect dust particles from the carpet into an attached sampling container. A sample is
taken by vacuuming a given area with overlapping path lengths. An ASTM standard method is
available for this technique (26).
EPA studies have also used a polyurethane foam (PUF) roller sampler to determine dislodgeable
or transferable residues from floors (15-16, 27-29}. The PUF roller generally consists of an
aluminum frame with aluminum wheels. A PUF sleeve is the placed on the frame and the
sample is taken by rolling the sampler back and forth over the selected 100 cm traverse path.
This technique was used in CTEPP where a 7.6 cm thick pre-cleaned PUF was used on the roller.
One EPA study compared the PUF roller to the Dow drag sled and the California cloth roller
methods to determine which was best at estimating the transfer of chlorpyrifos to carpets and
vinyl flooring to skin (27, 28). The PUF roller used in this study is similar to the one discussed
previously. The PUF sleeve used in the EPA comparison study measured 90 millimeter (mm)
outer diameter x 30 mm inner diameter x 76 mm length. A 100 cm sample length was used, with
sampling consisting of one forward and one backward pass of the length. The roller was
operated at a rate of 10 centimeters per second (cm/s). The drag sled device consisted of a 3" x
3" piece of 3A" plywood as the base with an 8 pound weight mounted on top. A pre-cleaned 4"x
4" undyed denim cloth was used on the underside as the sampling media. The sled was pulled by
a wire along a 48 inch path at a rate of 10 cm/s. The California roller device resembled a large
rolling pin made of poly vinyl chloride pipe. The pipe was 63 cm long, 13 cm in diameter
covered with 1 cm thick foam, and filled with steel ball bearings. A 17" x 17" pre-cleaned
percale sheet cloth (50 percent cotton, 50 percent polyester) was used to collect the sample by
placing the cloth on the sampling area, covering it with the plastic, and pushing the roller over it.
The study found the drag sled and PUF roller to be better methods than the cloth roller technique.
All three methods had reasonable precision (24 to 46 percent). Transfer efficiencies ranged from
2 percent to 7 percent, with the drag sled method averaging 2.1 percent.
Other exposure studies have also relied on the PUF roller for sampling. Nishioka et al. (15-16,
29) used the sampler to determine the available dislodgeable residue or surface dust of 2,4-D on
indoor carpets. The PUF sleeves used were 8 cm long x 8 cm outer diameter. The PUF was pre-
16
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cleaned before use with water and then 70:30 volume/volume acetonitrile:phosphate buffer. In
one of these studies, the PUF was moistened with a 70:30 phosphate bufferacetonitrile mixture
that simulates human sweat, allowing the PUF roller to simulate a child's hand contact with the
sampling surface. A 0.48 m2 area was sampled at a rate of approximately 17 cm/s. The PUF
roller provided transfer efficiencies of 0.1 percent to 0.2 percent.
In a study by Lu and Fenske (30), the PUF roller method was compared to wipe sampling to
determine which was better at simulating hand pick-up of chlorpyrifos residues from carpet. The
PUF sleeve used was 8 cm in length and sampling was conducted over a 100 cm length (total of
800 cm2 area) using techniques similar to those described previously. The PUF sleeve was
misted with DI water before use. The wipes used in this study were 12-ply 7.6 cm x 7.6 cm
surgical gauze pads. They were also moistened with DI water before sampling was conducted.
In this case, a 100 cm2 area was wiped. The area was first wiped with three strokes, and then the
sampling was repeated with a second pad in the orthogonal direction. Results showed that
chlorpyrifos residue transfer as measured by these methods was 23 to 36 times greater than that
found from normal carpet to skin transfers.
The Minnesota Children's Pesticide Exposure Study compared two different surface sampling
methods to determine which better represents realistic estimates of exposure (31). Malathion,
atrazine, diazinon, and chlorpyrifos were measured using the Edwards and Lioy (EL) sampler
and the Lioy, Wainman, and Weisel (LWW) surface wipe sampler. The EL sampler is a press
sampler designed to collect surface dust from carpets or other surfaces. CIS filters were used
and a 150 cm2 area was sampled. Samples were collected from both carpet and another non-
carpeted surface. The LWW sampler consisted of a CIS impregnated Teflon filter wetted with
IPA and placed on a pressure plate. A sample was taken by sliding the sampler the length of a
100 cm2 template three times. Wipe samples from smooth surfaces were collected in this
manner. The LWW sampler was determined to not be representative of pesticide residues found
on a child's hand from dermal contact with contaminated surfaces. The EL sampler, because it
uses only a single hand press, represents what dislodgeable residues are available via one hand
contact on the surface, not the total amount that might end up on a child's hand.
Other techniques for assessing surface contamination include directly applying a sensing
instrument at or near the surface. Some examples of direct sensing techniques include: X-ray
fluorescence devices for metals detection, radiation meters for determining radioactivity, and
portable photoionization monitors for detecting volatile organic compounds. The application of
these direct-sensing techniques is usually limited to: qualitative (e.g., presence/absence) results,
higher detection limits, analyte selectivity, and availability of detection capability for the target
analyte. For these reasons, wipe sampling techniques are typically used in conjunction with or
instead of direct sensing techniques. For example, as noted previously, the TSA often collects
wipe samples of passengers' luggage and then tests the wipes for explosives residue using ion
mobility spectrometry, a direct-sensing technique. Because we regard this as more of a direct-
sensing method rather than a wipe sampling method, this technique was not researched as part of
this report.
For many studies, it is important to understand what amount of contaminants a person has
transferred from the surface to his hands. Hand wipe samples or dermal wipes have therefore
17
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played a major role in many exposure studies. Dermal wipes generally consist of some sort of
gauze sponge or cloth being used as the wipe, the wipe being wetted, and then the hand being
thoroughly wiped. For the CTEPP study, pre-extracted gauze pads, the same as those used for
surface wipes, were wetted with 2 mL of 75 percent IPA in DI water and used for hand wipe
samples (72). NHEXAS dermal wipes were similar but used 4 mL of IPA (13}. OSHA
recommends the use of glass fiber filters, mixed cellulose ester filters or smear tabs, gauze
sponges, or charcoal impregnated pads moistened with either DI water or a 50 percent solution of
IPA in water (18). McArthur (5) notes the use of ethyl alcohol for dermal wipe samples.
Though dermal wipes do not measure the contaminated surface, they can provide a more
accurate assessment of a person's exposure to a chemical.
3.8 Summary
Numerous wipe sampling methods were found for different government agencies, such as EPA,
OSHA, and NIOSH, and for various sampling studies that have been conducted by different
researchers. Wipe media ranged from gauze sponges to Whatman filters to pre-wetted,
commercially-available wipes. Wipe sampling methods were found for various compounds,
such as metals, PCBs, drugs, and pesticides.
Wipe sampling provides a simple way of testing for contamination on a particular surface and
can provide information on the mass of a contaminant on the surface. However, variability in
reproducibility and removal efficiencies can result from the lack of standardization within a
particular wipe sampling method as well as across various other methods. Simply clearly
measuring the area to be sampled can significantly lower this variability. Different surface
characteristics can also affect wipe sampling efficiency. It is therefore important that a wipe
sampling method be fully validated before it is used so that such performance parameters, as
discussed here, can be determined and improved.
18
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Chapter 4
Physical and Chemical Properties
4.1 Chemical Agents and TICs of Interest
Wipe sampling methods exist for a variety of situations and a diverse number of chemicals. The
focus of this report, however, is on a select set of compounds. Table 1 lists the compounds of
interest to EPA that are the subject of this literature review. The ultimate goal of this review is to
determine what wipe sampling methods are available and have been used for these compounds.
Before that can be done, however, it is important to better understand the compounds listed in
Table 1. To this end, the physical and chemical properties of each of the compounds of interest
listed in Table 1 have been obtained, as available, for this report. The chemical structure of each
compound has also been collected. The structures are provided in Appendix A.
Tables 3 through 7 provide a summary of some of the physical properties listed in the MSDS
information that was obtained. Characteristics that are provided where available include the
chemical family that the compound belongs to; the physical state of the compound; its molecular
weight and formula; boiling, freezing, and melting points; vapor pressure and density; and
solubility. The information listed in Tables 3 through 7 was gathered from the MSDSs listed in
Table 1, two other primary references that were used to fill in gaps in the information (1, 2), and
those references discussed in Chapter 2.
There are essentially two major classes of compounds in the following tables: organophosphate
(OP) pesticides and CWAs and related compounds (e.g., CWA precursors and degradation
products). A couple other compound classes round out the list, such as rodenticides and
controlled substances, but the OP pesticides and CWAs and related compounds comprise 83
percent of the compounds of interest to this literature review. Within the group of CWAs, there
are two different types: blister agents (see Table 3) and nerve agents (see Table 4). HD, H, HT,
Lewisite, and ED are all blister agents. Blister or vesicant agents produce burns and blisters on
the skin of those who come in contact with them. The mustard agents (HD, H, and HT) are
chemically stable. They are not very soluble in water, but that which does dissolve in water can
hydrolyze very quickly. HT is actually a mixture of 60 percent H and 40 percent T (a closely
related mustard). Lewisite and ED are organic arsenicals. They have similar properties to the
mustard agents but they contain arsenic instead of the sulfur found in mustard agents. Lewisite
is often found as a mixture of isomers (Lewisite 1, 2, and 3) and is only slightly soluble in water.
19
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Table 3. Physical/Chemical Properties of CWAs - Blister Agents
Compounds
Mustard Gas (H)/
Distilled Mustard
(HD)
Mustard (HT)
Ethyldichloroarsine
(ED)
Lewisite (1)
Lewisite (2)
Lewisite (3)
CAS#
505-60-
2
172672-
28-5
598-14-
1
541-25-
3
40334-
69-8
40334-
70-1
Chemical Class
organic sulfur
compounds
organic sulfur
compounds
halogenated,
aliphatic
halogenated,
aliphatic
halogenated,
aliphatic
halogenated,
aliphatic
Physical
State
liquid
liquid
liquid
liquid
liquid
liquid
Molecular
Weight
159.08
263.3 (T)
174.89
207.31
233.36
259.39
Molecular
Formula
C4H8C12S
C8H16C12S2O
(T)
C2H5AsCl2
C2H2AsCl3
C4H4AsCl3
C6H6AsCl3
Boiling
Point
423 °F
(217°C)
>228
°C
NA
159.8
°C
230 °C
215.4
°C
Freezing
Point
57 °F
(14 °C)
NA
< -65 °C
32.2 °F
(0.1 °C)
NA
NA
Melting
Point
NA
0.0- 1.3 °C
NA
NA
NA
NA
Vapor
Pressure
0.09
mmHg
® 30 °C
0.077
mmHg
® 25 °C
2.29
mmHg
@
21.5 °C
0.395
mmHg
® 20 °C
0.108
mmHg
® 20 °C
0.217
mmHg
® 25 °C
Vapor
Density
(air =1)
5.5
6.5
6
7.1
NA
NA
Specific
Gravity
(water
=D
1.2741
NA
1.742@
14 °C
1.88 @
20 °C
1.702@
20 °C
1.572 @
20 °C
Water Solubility
very slightly soluble;
hydrolysis t]/2 = 5min @
25 °C only for what
dissolves
negligible
decomposes/hydrolyzes
immediately
decomposes/hydrolyzes
rapidly
NA
NA
Solvent
Solubility
fats, oils, organic
solvents
most organic
solvents
ethyl chloride,
alcohol, ether,
benzene,
acetone, kersone,
cyclohexane
ether, alcohol,
organic solvents
NA
NA
NA = Not Available
20
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Table 4. Physical/Chemical Properties of CWAs - Nerve Agents
Compounds
Sarin (GB)
Soman (GD)
Cyclohexyl sarin
(GF)
Tabun (GA)
VX
CAS#
107-
44-8
96-64-
0
329-99-
7
77-81-
6
50782-
69-9
Chemical Class
esters, halogens,
phosphine
esters, halogens,
phosphine,
organophosphorus
esters, halogens,
phosphine
organophosphorus,
phosphoryls,
amides
phosphono, sulfur
compounds
Physical
State
liquid
liquid
liquid
liquid
liquid
Molecular
Weight
140.11
182.19
180.16
162.13
267.36
Molecular
Formula
C4H10F02P
C7H16F02P
C7H14F02P
C5HnN2O2P
CnH26NO2PS
Boiling
Point
297 °F
(147 °C)
333 °F
(167°C)
228 °C
248 °C
568 °F
(298 °C)
Freezing
Point
-71°F(-
57 °C)
-94 °F (-
70 °C)
-30 to -
50 °C
-51°F(-
46 °C)
< -60 °F
(<-51
°C)
Melting
Point
NA
NA
NA
NA
NA
Vapor
Pressure
2.9
mmHg
® 25 °C
0.401
mmHg
® 25 °C
0.0927
mmHg
@ 25 °C
0.07
mmHg
@ 25 °C
0.0007
mmHg
® 25 °C
Vapor
Density
(air =1)
4.86
6.3
6.2
5.63
9.2
Specific
Gravity
(water
=D
1.10@
20 °C
1.026
1.128@
25 °C
1.073 @
25 °C
1.0083
® 25 °C
Water Solubility
miscible; hydrolysis
under acidic conditions;
t1/2=80hr@20°C,
pH7
2.1gGD/100g@20°C;
hydrolysis, ti/2 = 45hr @
pH 6.65
3.7gGF/100g@20°C;
hydrolysis, t]/2 = 42hr @
20 °C in DI water
7.1gGA/100g@20°C;
hydrolyzes, ti/2= 8.5 hr
@ 20 °C, pH 7
30 g/L @ 25 °C;
miscible @ 9.4 °C;
hydrolysis, varies ti/2 =
17 -42 days @ 25 °C,
pH7
Solvent
Solubility
organic solvents
organic solvents
organic solvents
organic solvents
lipids; organic
solvents
NA = Not Available
21
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Table 5. Physical/Chemical Properties of CWA Precursors and Degradation Products
Compounds
Dimethyl
phosphite
1,4-Dithiane
Thiodiglycol
1,4-Thioxane
Trimethyl
phosphite
CAS#
868-
85-9
505-
29-3
111-
48-8
15980-
15-1
121-
45-9
Chemical Class
phosphoryls, esters,
alkyl phosphite
heterocyclic, sulfur,
hydrocarbons
hydroxyls,
aliphatic,
mercaptans
ethers, alicyclic,
sulfur compounds,
ethers
organic, alkyl
phosphites
Physical
State
liquid
solid
liquid
liquid
liquid
Molecular
Weight
110.05
120.24
122.18
104.17
124.09
Molecular
Formula
C2H603P+
04^82
C4H10O2S
C4H8OS
C3H9O3P
Boiling
Point
336-342
°F (169-
172°C)
390-392
°F (199-
200 °C)
541 °F
(283 °C)
297 °F
(147 °C)
232-234
°F(111-
112°C)
Freezing
Point
NA
NA
3 °F (-16
°C)
1°F
(-17°C)
-108 °F
(-78 °C)
Melting
Point
NA
226-235 °F
(108-113
°C)
NA
NA
NA
Vapor
Pressure
<1.0
mmHg
® 20 °C
NA
1.3
mmHg
® 42 °C
NA
17.0
mmHg
@ 20 °C
Vapor
Density
(air =1)
NA
NA
4.2
3.59
4.3
Specific
Gravity
(water
=D
1.2
NA
1.1852
1.1174
1.052
Water Solubility
hydrolyzes
slightly soluble
soluble
NA
reacts
Solvent
Solubility
organic solvents
alcohol, carbon
tetrachloride,
ethanol, ether
ethanol, acetone,
methanol,
chloroform;
Slightly
Soluble: ether,
benzene, carbon
tetrachloride
N/A
hexane, benzene,
acetone, alcohol,
ether, carbon
tetrachloride,
kerosene,
organic solvents
NA = Not Available
22
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Table 6. Physical/Chemical Properties of OP Pesticides and Other Pesticides
Compounds
Chloropicrin
Dichlorvos
Dicrotophos
Fenamiphos
Methyl
parathion
CAS#
76-06-
2
62-73-
7
141-
66-2
22224-
92-6
298-
00-0
Chemical Class
nitro, halogenated,
aliphatic
heterocyclic,
organophosphorous
organophosphorus
organophosphorus
organophosphorus
Physical
State
liquid
liquid
liquid
solid
solid
Molecular
Weight
164.38
220.98
237.21
303.39
263.22
Molecular
Formula
CC13NO2
C4H7C12O4P
C8H16N05P
C13H22NO3PS
C8H10NO5PS
Boiling
Point
234 F
(112°C)
183 F
(84 °C)
@1
mmHg
266 °F
(130 °C)
@0.1
mmHg
NA
228 °F
(109°C)
@0.05
mmHg
Freezing
Point
-83 °F
(-64 °C)
NA
NA
NA
NA
Melting
Point
NA
NA
NA
120 °F
(49 °C)
97 °F (36
°C)
Vapor
Pressure
20
mmHg @
20 °C
0.012
mmHg @
30 °C
NA
negligible
0.000097
mmHg @
20 °C
Vapor
Density
(air =1)
5.7
15.3
NA
NA
NA
Specific
Gravity
(water
=D
1.7
1.415 @
25 °C
1.216
1.14
1.358
Water Solubility
0.2% ® 20 °C
1%; hydrolysis, t1/2 = 20
to 80hrs @ pH 9 to pH
4
miscible; hydrolysis, ti/2
= 50 days @ 38 °C
pH9.1
770 ppm @ 20 °C;
hydrolysis, ti/2 = 4hrs @
pH7
55-60 ppm @ 25 °C;
hydrolysis, 100%
degradation in seawater,
lakes and rivers in 1
week to 1 month
Solvent
Solubility
alcohol, ether,
acetone,
benzene, acetic
acid
organic solvents
acetone, alcohol,
isobutanol,
hexylene glycol,
xylene
dichloromethane,
isopropanol,
organic solvents;
Insoluble:
aliphatic solvents
dichloromethane,
isopropanol,
organic solvents;
Slightly
Soluble:
aliphatic
solvents, light
petroleum,
mineral oils
23
-------
Table 6. (continued)
Compounds
Mevinphos
Phorate
Tetraethyl
pyrophosphate
CAS#
7786-
34-7
298-
02-2
107-
49-3
Chemical Class
organophosphorus
organophosphorus
organophosphorus
Physical
State
liquid
liquid
liquid
Molecular
Weight
224.16
260.39
290.22
Molecular
Formula
C7H1306P
C7H1702PS3
C8H2oOyP2
Boiling
Point
617 °F
(325 °C)
244-248
°F (11 8-
120 °C)
@0.8
mmHg
255 °F
Freezing
Point
-69 °F (-
56 °C)
<5 °F (< -
15 °C)
NA
Melting
Point
NA
NA
NA
Vapor
Pressure
0.003
mmHg @
20 °C
0.00084
mmHg @
20 °C
0.00047
mmHg @
30 °C
Vapor
Density
(air =1)
7.5
NA
NA
Specific
Gravity
(water
=D
1.25
1.156
1.185
Water Solubility
miscible; hydrolysis, ti/2
= 35 days @ pH 7
50ppm; hydrolysis, ti/2 =
few days to few weeks in
acidic water
soluble; hydrolysis, ti/2 =
6.8hrs(S7pH6
Solvent
Solubility
acetone, carbon
tetrachloride,
chloroform,
alcohol, benzene,
toluene, xylene;
Slightly Soluble:
petroleum ether,
kerosene, carbon
disulfide;
Insoluble:
hexane
carbon
tetrachloride,
dioxane, xylene,
alcohols, esters,
ethers, vegetable
oils, methyl
cellosolve,
dibutyl phthalate
alcohol, benzene,
acetone, glycerol,
ethylene glycol,
propylene
toluene, xylene,
organic solvents;
Insoluble:
petroleum oils
NA = Not Available
24
-------
Table 7. Physical/Chemical Properties of Rodenticides and Controlled Substances
Compounds
Crimidine
Methyl
fluoroacetate
Nicotine from
nicotine sulfate
Phencyclidine
Strychnine
CAS#
535-
89-7
453-
18-9
54-11-
5
77-10-
1
57-24-
9
Chemical Class
pyrimidines
ester, acetic acid
pyridinyl
heterocyclic
heterocyclic,
nitrogen, alkaloids
Physical
State
solid
NA
liquid
solid
solid
Molecular
Weight
171.63
92.07
162.23
243.39
334.42
Molecular
Formula
C7H10C1N3
C3H5FO2
C2oH3oN404S
Ci7H25N
C2iH22N2O2
Boiling
Point
284-297
°F (140-
147 °C)
@4
mmHg
104.5
°C
247 °C
275-279
°F(135-
137 °C)
@ 1
mmHg
NA
Freezing
Point
NA
NA
NA
NA
NA
Melting
Point
189°F
(87 °C)
-35 °C
-79 °C
115-117°F
(46-47 °C)
547-550
°F(286-288
°C)
Vapor
Pressure
<0.00001
mmHg
@ 20 °C
30.8
mmHg
@25C
0.045
mmHg
@ 25 °C
NA
0 mmHg
@ 20 °C
Vapor
Density
(air =1)
NA
NA
NA
NA
NA
Specific
Gravity
(water
=D
NA
1.17@
20 °C
1.01
g/mL
NA
1.36
Water Solubility
1%®20°C
150 g/L; 2.5%
hydrolized in 60 hrs @
22-24 °C DI water
soluble
soluble
0.02%
Solvent
Solubility
alcohol, organic
solvents
NA
alcohol, ether
alcohol
chloroform;
Slightly
Soluble: alcohol,
benzene, ether,
toluene,
methanol,
glycerol, amyl
alcohol,
petroleum ether
NA = Not Available
25
-------
The nerve agents (G-series and VX compounds, see Table 4) have a high acute toxicity and
inhibit acetylcholinesterase throughout the body, disrupting the nervous system. They are
structurally similar OP compounds and, thus, are quite similar to OP pesticides. However, the
nerve agents contain a C-P bond that is not found in OP pesticides and that bond is very resistant
to hydrolysis (7). The nerve agents differ somewhat in the remainder of their structure. VX
contains sulfur while GB, GF, and GD contain fluorine; GA has a cyanide group. The G-series
nerve agents are more volatile than VX and present a vapor hazard. Furthermore, GA, GB, and
GF are more miscible in water, while VX and GD are less soluble (7). As Table 4 indicates,
hydrolysis rates also differ amongst the nerve agents, with VX having the longest half-life (17 to
42 days at 25 °C, pH 7). Though the C-P bond in nerve agents may resist hydrolysis, the overall
hydrolysis half-lives for these compounds is much shorter than those for the OP pesticides
discussed in this report (see Table 6). The P-F bond is the first to hydrolyze for GB, GD, and
GF; the P-CN bond for GA; and the P-S bond is prone to hydrolysis for VX. Two of the
compounds from Table 1 are precursors to the manufacturing of G-series nerve agents. These
are trimethyl phosphite (TMP) and dimethyl phosphite, both of which are alkyl phosphites (see
Table 5). TMP can also be used as an intermediate in the manufacturing of OP pesticides.
The degradation of mustard agents can produce multiple compounds. Table 5 provides
information on the degradation and hydrolysis products from the list of compounds of concern.
1,4-Thioxane is a degradation product of mustard gas; 1,4-dithiane is a thermal degradation
product of HD (7). Thiodiglycol is also known to be a product of the hydrolysis of HD. This
chemical, though, is also a precursor to the production of sulfur-based blister agents.
These degradation products are only a small portion of the overall number of degradation
products associated with the CWAs identified in this report. Not only do CWAs break down in
the environment, but the agents themselves are full of impurities which can also make their way
into the environment in the event of a CWA distribution. In fact, the sulfur mustard agents alone
(H, HD, and HT) have over 40 associated degradation products, hydrolysis products, and
impurities (7). Lewisite has seven reported impurities and degradation products, while GA has
22, GB has nine, and GD has seven reported impurities and degradation products; VX alone has
over 30 (7). A table of the known toxic and persistent degradation products of the
aforementioned CWAs can be found in Munro et al. (7).
Dichlorovos, dicrotophos, fenamiphos, methyl parathion, mevinphos, phorate, and tetraethyl
pyrophosphate (TEPP) are all OP pesticides (see Table 6). OP pesticides work similarly to the
CWA nerve agents, inhibiting acetylcholinesterase in the insects they target. They can also act
as acetylcholinesterase inhibitors in humans. OP pesticides are used on many fruit and vegetable
crops as well as in and around buildings, though their residential uses have been voluntarily
withdrawn by the manufacturers. Most OP pesticides are only slightly soluble in water, have a
low volatility, and undergo hydrolysis. However, there are some exceptions to the rule. For
example, dicrotophos is considered miscible in water but does not undergo hydrolysis quickly.
Dichlorovos, on the other hand, is not as soluble but can hydrolyze rather quickly under the right
conditions. Mevinphos and TEPP are also soluble in water, but their hydrolysis rates in neutral
water differ greatly. For mevinphos, the half-life in water can be up to 35 days. The hydrolysis
half-life for TEPP in neutral waters is closer to seven hours, with that time decreasing down to
minutes as the pH increases. Phorate and methyl parathion have similar solubility in water as
26
-------
well as similar hydrolysis rates. Fenamiphos is more soluble than these OP pesticides, and its
hydrolysis rate is also much quicker.
Though the basic structural building block is consistent in all of the OP pesticides, each
compound has a slightly different overall structure that separates it from the rest. As the name
implies, dichlorovos has two chlorine atoms, while phorate has three sulfur atoms. Both methyl
parathion and fenamiphos have a benzene ring, a sulfur atom, and a nitrogen atom, but they are
not oriented in the same way. Dicrotophos has a nitrogen atom along with multiple methyl
groups, while mevinphos has oxygen atoms with methyl groups. TEPP is set apart from all of
the other OP pesticides by having two phosphorous atoms in its structure. These structural
differences allow for the physical property differences discussed previously.
The remaining compounds from the list are somewhat diverse. Chloropicrin is a pesticide (see
Table 5) and is used as an insecticidal fumigant. It is also blended with several other toxic
fumigants for insect control, but also has roots as a chemical weapon in World War I, where it
was known as PS. Chloropicrin has also been described as an irritant and something that has
been used for riot control as a tear gas. As with ED, chloropicrin is aliphatic and halogenated,
but it contains nitrogen instead of arsenic. As with many other compounds in Tables 3 through
7, this contaminant is not very water soluble. Crimidine and strychnine are both rodenticides
(see Table 7) that act on cells in the brain and spinal cord to cause convulsions. Strychnine,
however, is a very large molecule compared to crimidine, and is even less water soluble, though
both are barely soluble. Nicotine (see Table 7) is a nerve poison that acts on the nicotinic
acetylcholine receptors. Nicotine sulfate is an insecticide and nicotine can be generated from it.
Nicotine shares one similarity with crimidine as well as phencyclidine (PCP) in that they all have
nitrogen rings in their structure. Nicotine is also considered a drug, as is PCP. PCP (see Table
7) is a dissociative drug and is also a neurotoxin. Both compounds are readily soluble in water,
as some of the compounds previously discussed are. As with the other compounds, methyl
fluoroacetate (see Table 7) is considered a toxin; it has rodenticidal properties. Fluoroacetates, in
fact, were considered as potential CWAs at one point. As with some of the nerve agents, the
hydrolysis half life for methyl fluoroacetate is quite long (2.5 percent in 60 hours).
4.2 Summary
A good understanding of the properties of each of the compounds of interest is important in
selecting an appropriate wipe sampling method for them. As such, Tables 3 through 7 provide a
synopsis of the physical and chemical properties of the compounds listed in Table 1. The CWA
blister agents are presented in Table 3, CWA nerve agents in Table 4, CWA precursors and
degradation products in Table 5, OP and other pesticides in Table 6, and the remaining
compounds (rodenticides and controlled substances) in Table 7. Within each compound class,
similarities and differences exist, as noted in this chapter. Many of the descriptions in this
chapter reference the chemical structure of each compound to elucidate a better understanding of
the compound classes. The chemical structures of each of the compounds listed in Table 1 can
be found in Appendix A.
27
-------
28
-------
Chapter 5
Wipe Sampling Methods for Chemical Warfare Agents and Toxic Industrial
Chemicals
A variety wipe sampling techniques have been used for some of the compounds listed in Table 1.
A summary of the wipe sampling information for the compounds of interest is provided in Table
8. Information regarding the analyte, wipe material, wetting solvent, wipe surface, and
determinative step are provided, including the reference where this information was obtained.
Information gaps are designated as "NA" in the table, and as shown in Table 8, limited specific
wipe sampling information was found for many of the compounds of interest. The literature
information which was available and summarized in Table 8 is described in this section,
organized by chemical class.
5.1 OP Pesticides/Pesticides
Surface wipe sampling for methyl parathion was conducted in a number of different studies. In a
study of 18 pesticides (including methyl parathion) by Lemley et al. (32), living room dust wipe
samples were taken, usually from a window sill or table, using two Whatman filter papers. One
wipe was moistened with water and the other with aqueous methanol solution. Approximately
0.031 m2 was sampled by wiping across the area with each wipe. Methyl parathion was found in
one of the 15 wipe samples taken.
In a study by Clark et al. (33), methyl parathion wipe samples were collected to assess the
potential exposures and health risks of a population, provide a basis for enforcement action, and
determine which properties needed decontamination. Wipes consisted of gauze pads wetted with
IPA. A 100 cm2 area was wiped in this study. Surface sampled included baseboards, counter
splashboards, and under the kitchen sink. Similar wipe sampling methods were used by Wasley
et al. (34} for methyl parathion sampling in another study. Specific wipe sampling information
was not found for the remaining OP pesticides (dichlorovos, dicrotophos, fenamiphos,
mevinphos, and phorate).
Though chloropicrin is considered a pesticide (though not an OP pesticide), it is also listed as a
Scheduled (Schedule 3) chemical by the Organisation for the Prohibition of Chemical Weapons'
(OPCW's) Chemical Weapons Convention (www.opcw.org). Details on sampling methods for
Scheduled chemicals are discussed in the next section.
29
-------
Table 8. Summary of Wipe Sampling Information Found in the Literature for the Compounds of Interest
Compound
Class
OP Pesticides/
Pesticides
CWAs - Blister
Agents
Compound
Chloropicrin
Dichlorvos
Dicrotophos
Fenamiphos
Methyl parathion
Mevinphos
Phorate
Tetraethyl
pyrophosphate
Distilled Mustard
(HD)
Mustard Gas (H)
Mustard (HT)
Ethyldichloroarsine
(ED)
Lewisite (1)
Wipe Material
lint-free cotton
NA
NA
NA
filter paper
gauze pad
NA
NA
NA
Q-tip, cotton cloth, felt,
filter paper
Woven polyester/cotton
blend
lint-free cotton
lint-free cotton
lint-free cotton
NA
Woven polyester/cotton
blend
lint-free cotton
Wetting Solvent
DCM, methanol
NA
NA
NA
water or aqueous
methanol
IPA
NA
NA
NA
acetone, IPA,
ethyl acetate,
DCM
IPA
DCM, methanol
DCM, methanol
DCM, methanol
NA
IPA
DCM, methanol
Wipe
Surface
NA
NA
NA
NA
Window sills
or tables
Kitchen
(baseboards,
backsplash,
under sink),
bathroom
(baseboard)
NA
NA
NA
painted
metal,
concrete
NA
NA
NA
NA
NA
NA
NA
Determinative
Step
NA
NA
NA
NA
GC/MS
GC/MS or
GC/FPD
NA
NA
NA
GC/MS
GC/MS
NA
NA
NA
NA
GC/MS
NA
Reference
35
NA
NA
NA
32
33,34
NA
NA
NA
35
37,38
36
36
36
NA
37,38
36
30
-------
Table 8. (continued)
Compound
Class
CWAs - Blister
Agents
CWAs - Nerve
Agents
CWA
Precursors and
Degradation
Products
Compound
Lewisite (2)
Lewisite (3)
Sarin (GB)
Soman (GD)
Cyclosarin (GF)
Tabun (GA)
VX
1,4-Dithiane
Thiodiglycol
1,4-Thioxane
Trimethyl
phosphite
Dimethyl
phosphite
Wipe Material
Woven polyester/cotton
blend
lint-free cotton
Woven polyester/cotton
blend
lint-free cotton
Q-tip, cotton cloth, felt,
filter paper
Woven polyester/cotton
blend
lint-free cotton
Woven polyester/cotton
blend
lint-free cotton
lint-free cotton
Woven polyester/cotton
blend
lint-free cotton
Woven polyester/cotton
blend
NA
lint-free cotton
NA
lint-free cotton
lint-free cotton
Wetting Solvent
IPA
DCM, methanol
IPA
DCM, methanol
acetone, IPA,
ethyl acetate,
DCM
IPA
DCM, methanol
IPA
DCM, methanol
DCM, methanol
IPA
DCM, methanol
IPA
NA
DCM, methanol
NA
DCM, methanol
DCM, methanol
Wipe
Surface
NA
NA
NA
NA
painted
metal,
concrete
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Determinative
Step
GC/MS
NA
GC/MS
NA
GC/MS
GC/MS
NA
GC/MS
NA
NA
GC/MS
NA
GC/MS
NA
NA
NA
NA
NA
Reference
37,38
36
37,38
36
35
37,38
36
37,38
36
36
37,38
36
37,38
NA
36
NA
36
36
31
-------
Table 8. (continued)
Compound
Class
Rodenticides
Controlled
Substances
Compound
Crimidine
Methyl
fluoroacetate
Strychnine
Nicotine
Phencyclidine
Wipe Material
NA
NA
NA
NA
NA
Wetting Solvent
NA
NA
NA
0.1% ascorbic
acid
NA
Wipe
Surface
NA
NA
NA
non-
upholstered
living room
and bedroom
furniture; 10
cmx 10 cm
NA
Determinative
Step
NA
NA
NA
GC/MS
NA
Reference
NA
NA
NA
39
NA
NA = Information not available in the literature
DCM = dichloromethane
IPA = isopropyl alcohol
GC/MS = gas chromatography/mass spectrometry
GC/FPD = gas chromatography/flame photometric detector
32
-------
5.2 CWAs, CWA Precursors, and CWA Degradation Products
In a Norwegian study, different types of wipe samples for collecting HD and GB on solid
surfaces were used after the chemical agents had been applied to the area (35). Q-tips, cotton
cloth (10 cm2), felt (1.5 cm diameter), and filter paper (1.5 cm diameter) were used as the wipe
media. Acetone, IP A, ethyl acetate, and DCM were used as the wetting solvent with each wipe
media. Two surfaces were tested as part of this experiment: a painted metal surface with
combined layers of epoxy, polyurethane, and alkyd paint (similar to a military vehicle) and a
concrete surface (to simulate a building). An artery clamp was used to hold the cotton cloth
during sampling while disposable pincers were used for the filter paper and felt. Wipe materials
were wetted with one of the aforementioned solvents, and wipe samples were taken from the
sampling surface at 5 minutes, 6 hours, and 24 hours after the CWA application. Wipe samples
were also taken using dry wipe media. For surface samples contaminated with HD, ethyl
acetate-wetted Q-tips had the highest recoveries from painted metal surfaces (between 50 percent
and 60 percent). Cotton cloths, however, are recommended by the OPCW (36). Higher
recoveries were seen for wet over dry wipes after six and 24 hours. Recoveries were less than
0.5 percent for dry Q-tips after six hours and 0.003 percent after 24 hours. Recoveries for Q-tips
wetted with ethyl acetate were between 2 percent and 6 percent after six hours and 0.05 percent
after 24 hours. Other wetting solvents gave recovery rates similar to that of ethyl acetate.
On concrete surfaces, ethyl acetate wetted wipes gave recoveries of < 6 percent after 5 minutes
for both HD and GB. Recovery rates were even lower after 6 hours (< 1 percent for HD). There
were no significant differences between Q-tip and cotton cloth wipe recovery rates for HD from
concrete surfaces. The Q-tip, however, proved to be easier to use in the field.
Overall, the Q-tip was viewed to be the best medium for sampling solid surfaces for HD and GB
(35). Better recoveries were found with wetted versus dry wipes, and ethyl acetate was the
solvent of choice. It was also discovered that an increase in the amount of time that transpires
between the initial application of the CWA and the wipe sample leads to lower recoveries of the
agent from the surface. Recovery rates for HD using a Q-tip wetted with ethyl acetate dropped
from 44 percent after five minutes on a painted metal surface to 2.4 percent after six hours to
0.05 percent after 24 hours. Thus, the condition of the solid surface as well as the length of time
after a contamination would influence the ability to determine the presence of CWAs.
Various other wipe sampling methods have been employed for CWAs. The U.S. and Finland
Joint Document describes the use of wipe samples for GA, GB, GD, HD, VX, and Lewisite
using a 3" x 3" portion of as well as full Texwipe Clean Cotton Wipes, which are a
polyester/cotton blend (37). Further sampling details were not provided. In an extension of the
U.S./Finnish study evaluating the method's ability to extract all of the CWAs from one wipe, a
9" x 9" TX™ 1020 polyester/cotton blend wipe was used (35). The wipe was moistened with
IPA before spiking tests were performed.
The OPCW provides guidance for inspectors in collecting on-site wipe samples for scheduled
chemicals. Scheduled chemicals include HD, H, HT, Lewisite 1, Lewisite 2, Lewisite 3, GB,
GD, GF, GA, thiodiglycol, trimethyl phosphite, dimethyl phosphite, and chloropicrin. OPCW
33
-------
indicates that a packaged wipe from the sample collection kit should be used for the wipe
material (36). This is usually an adsorbent wipe made of lint-free cotton. Some of the wipes are
wetted with 2 mL of DCM while other are wetted with 2 mL of methanol. To take a sample, a
DCM-wetted wipe is held with tweezers or haemostats and rubbed with force in a circular
motion over the surface of interest. As necessary, the procedure is repeated with a methanol-
wetted wipe.
5.3 Rodenticides
No wipe sampling information was found in the literature for crimidine, methyl fluoroacetate or
strychnine.
5.4 Controlled Substances
Matt et al. (39) collected wipe samples for nicotine analysis from living room and bedroom (non-
upholstered) furniture using pre-screened wipes. The wipes were soaked in 0.1 percent
(weight/volume) ascorbic acid. A 100 cm2 area was sampled. No information was found for
PCP.
5.5 Summary
Table 8 summarizes the wipe sampling methods found in the literature for the compounds of
interest listed Table 1. Unfortunately, much of the information that was sought for this report
was not found in the literature, as indicated by the large number of "NA" designations in the
table. In these instances, "NA" indicates that a particular category of information was not found
in the reference that is cited. In many cases, only the sampling method was presented in the
paper, not the analytical techniques required to test a given sample. Furthermore, most of the
cited articles did not specify a particular surface on which to perform the wipe sampling. While
most wipe sampling is generally performed on smooth, hard, non-porous surfaces, samples are
often taken from many other surface types, as discussed in Chapter 3. Not providing a sampling
surface in the referenced documents in Table 8 most likely indicates that the robustness of a
particular sampling method beyond general non-porous surface sampling has not been explored.
Before these methods could be used on different or novel surface types, surface residue
extraction efficiencies would have to be investigated.
34
-------
Chapter 6
Summary and Data Gaps
6.1 Summary of Available Wipe Sampling Information for Compounds of Interest
Limited wipe sampling information was found in the literature for the compounds of interest
presented in Table 1. This section summarizes the literature information that was found by
compound class. Information found in the literature summarized in Chapter 5 is used to discuss
reasonable extrapolations as to what types of wipe, wetting agents, and techniques might be
appropriate for the compounds for which no literature information was found. A general
discussion of the information found throughout the report is also presented.
6,1.1 OP Pesticides
As shown in Table 8, literature information was only available for chloropicrin and methyl
parathion. The wipe materials used in these studies were lint-free cotton, filter paper, and gauze
pads; the wetting solvents used were DCM, methanol, water, and IPA. Surfaces wiped were
only noted for methyl parathion wipe samples; the surfaces wiped in those studies were smooth
and non-porous.
Specific wipe sampling information was not found for the remaining OP pesticides of interest to
this study. However, multiple wipe sampling methods were discussed for chlorpyrifos in Section
3.2. Chlorpyrifos is an OP pesticide. Thus, it would be expected that sampling methodologies
for chlorpyrifos could also be applied to other OP pesticides. However, the literature does not
provide a consensus on which wipe sampling method is appropriate for all OP pesticides. The
chlorpyrifos sampling methods included the use PUF rollers and cotton gauze pads moistened
with water, IPA, and isooctane. The use of a cotton gauze pad, wetted with IPA has been used by
more than one study and is the current method supported in multiple EPA studies.
6.1.2 CWAs, CWA Precursors, and CWA Degradation Products
The literature on CWAs and their precursor and degradation products indicated that cotton or
polyester/cotton blend wipes, as well as Q-tips, have been used for sampling these compounds.
The wetting solvents included mostly IPA, DCM, and methanol; with the exception of one study
for Sarin (GB) and Mustard (HD) which also used acetone, IPA and ethyl acetate. Water could
not be used for CWA wipe samples due to rapid hydrolysis. The studies cited in Table 8 did not
agree on what wipe materials and wetting agents were preferable for CWAs. Limited
performance data were only available for one study that only focused on wipe sampling for HD
and GB (35).
35
-------
Surfaces wiped were only noted in one study by Opstad et al. where painted metal and concrete
were sampled. This study determined that an increase in the amount of time that transpires
between the initial application of the CWA and the wipe sample leads to lower recoveries of the
agent from the surface. This implies that the condition of the solid surface as well as the length
of time after a contamination would influence the ability to determine the presence of CWAs.
CWA nerve agents are also OP compounds and behave similarly to OP pesticides. This would
seemingly indicate that wipe sampling methods for OP pesticides could be used for the nerve
agents in Table 1. In fact, the joint U.S./Finnish method tested wetting the CWA sampling wipes
with IP A, the same wipe solvent used in multiple EPA studies (e.g., CTEPP and CHEERS) and
is recommended in the ASTM method (10).
6.1.3 Rodenticides
No information was found on wipe sampling for the two rodenticides on the target compound
list. The ASTM method (10) for organic compounds, however, specifies using a gauze wetted
with IP A, which could be appropriate for these compounds as well.
6.1.4 Controlled Substances
As described in Section 5.4, only literature on wipe sampling for nicotine was found: cotton
gauze, wetted with 0.1 percent ascorbic acid. Non-upholstered furniture were sampled in the
cited study. This technique works well for nicotine because of its basic properties. Since PCP is
also considered a basic drug, this wipe sampling method could be appropriate for it, too.
6.1.5 General Thoughts on Available Wipe Sampling Information
The literature review of each compound class indicated that cotton wipes are most commonly
used. Most hard surface collection techniques for chlorpyrifos (and other OP pesticides) involve
the use of some type of gauze pad. The OPCW recommends the use of a cotton cloth for CWA
wipe sampling. Cloth or gauze wipes are easily transported, readily wetted, and are convenient
for sampling most surfaces. Wipe samples that use cloth or gauze can even be used on more
uniquely shaped surface areas. Of course, surfaces such as cement could snag or tear such a
wipe material. In these instances, filters, cotton swabs or Q-tips, found to be the best performers
in a CWA residue study (35), might be better. However, the amount of area that a swab could
cover might be problematic. As the ASTM method (77) alludes to, gauze pads have been found
to contain high background concentrations of potential interferents, depending on what chemical
is to be sampled. In such instances where there is an interference, the wipes must be pre-cleaned,
removing the potential interferent, before any sampling can occur. This can be costly and time-
consuming. In this case, Q-tips or even filters might be better, alternative wipe media to avoid
this issue.
As Table 3 indicates, most of the target compounds are readily soluble in organic solvents. The
use of water as a wetting agent would then not be desirable, if not for this reason then for the
reason that it would cause many of these chemicals to hydrolyze, eliminating the parent
compound and leaving behind the hydrolysis products. Alcohol can be used as a suitable solvent
for many of the compounds, and IPA appears to have the potential to be a reasonable wiping
36
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solvent for most of the compounds of interest. Even for studies like CHEERS, the IP A wipe was
intended not only for sampling of OP pesticides, but also for collecting PBDEs, other pesticides,
pesticide metabolites, and perfluorinated compounds. The ASTM method also notes IPA's
utility in collecting other compounds besides OP pesticides. Thus, IPA might also be an
appropriate solvent for many of the compounds used in Table 1.
One issue of potential concern with IPA-wetted wipes is that heavily wetted wipes are thought to
extract chemical residues from within the sampling surface, not just residues on top of the
surface. However, when sampling for the chemicals in Table 1, particularly after an attack or
decontamination effort, this sampling effect may not be a concern.
IPA was chosen for many studies because of its low toxicity, familiarity to study participants,
and ability to not disturb most furniture finishes, because it was to be used mainly around
children in EPA studies and on or near people for other studies. If the compounds in Table 1 are
to be sampled in a less sensitive environment, then stronger solvents could potentially be used.
DCM and methanol are recommended by the OPCW for collecting residual CWAs on surfaces.
Ethyl acetate was determined to be a good wipe wetting solvent for the collection of HD and GB
from surfaces. This solvent has also proven robust for sampling pesticides and other organic
contaminants in exposure assessments, but is not often used because it can mar furniture finishes.
Ethyl acetate wipes can, however, be easier to extract than those containing IPA. Given its past
performance and ability to work for CWA sampling, ethyl acetate could also be a good wipe
wetting solvent for most of the compounds in Table 1. Other solvents, including acetone and
DCM, were also found to work reasonably well. These solvents could likely be applied to wipes
for other CWAs or pesticides from Table 1, especially if the toxicity of the solvent or the
possible destruction of furniture finishes is not a concern.
6.2 Gaps
As described throughout this report, many gaps still exist in determining the best wipe sampling
method for the compounds listed in Table 1. Specific wipe sampling information, such as the
wipe material and wetting solvent, was not available for many of the compounds of interest.
Furthermore, details on the precise wipe method used as well as the performance of the method
were often lacking. Before a wipe sampling method can be used for these compounds, existing
methods must be fully validated and the gaps that exist must be filled in.
Besides wipe sampling information being missing for many of the compounds of interest (see
Table 8), one of the largest data gaps that was found was information on the effects of various
surfaces. Wipe samples could potentially be taken from a variety of surfaces. Limited
information was obtained from the literature on what techniques or materials are best on different
surfaces, or even if there are any surface characteristics (e.g., porous versus non-porous) that
might affect or interact with the compounds of interest and affect what is available for collection
by a wipe. Gauze pads can be used on most surfaces, and they have been used extensively in the
past (and present) to sample multiple household surfaces, toys, furniture, carpet, and hands
among others. As noted in Section 3.7, PUF roller samplers have been used for turf and carpet
sampling. Most of the sampling methods that were obtained for the compounds in Table 1,
37
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however, do not explore the usefulness of that method on various surfaces. Wiping surfaces from
a building decontamination effort would include a large array of different surfaces that would
need to be sampled. Thus, it is important to understand how different surfaces might affect the
wipe sampling process as well as potentially the compound being sampled. Along these lines, it
is also important to also determine the extraction efficiency of the wipe sampling method to
determine which is appropriate to use either for a given surface, a given compound, or a
combination of the two.
A complicating issue for collecting wipe samples for CWAs (mainly nerve agents and some OP
pesticides) is the fact that these compounds can undergo hydrolysis and other environmental
breakdown, leaving behind degradation products in place of the parent compound. The wipe
sampling discussed in this report focused on the parent compound, not sampling for degradation
products, which can also be toxic. Munro et al. (2) contains a literature review of chemical agent
degradation products and impurities, which can be numerous for a given chemical agent. In this
article, a list of known persistent or toxic degradation products for many of the CWAs is
provided. Degradation products included in the list that are not part of the target list for this study
include diisopropyl methylphosphonate, EA 2192 (S-2-diisopropylaminoethyl
methylphosphonothionic acid), ethylmethyl phosphonic acid, isopropyl methylphosphonic acid,
and methylphosphonic acid. These degradation products tend to be small molecules and are more
polar than the parent compounds. It is possible, however, that the wiping method for the parent
compounds could be applied for the degradation products (i.e., IPA would most likely be the
appropriate solvent). Any efforts to implement a wipe sampling method for CWAs will need to
consider the hydrolysis products and how they fit into the overall sampling and analysis scheme.
Wipe sampling methods have varied across studies found for this report. Some of the methods
rely on vertical and horizontal strokes, while others recommend "S" or "Z" patterns, while still
others call for more or less wipes per area. Sampling specifics for the compounds in Table 1 are
very sparse, if not non-existent. Sampling areas are provided in a couple of studies. For a wipe
method to be used properly and provide dependable and repeatable results, specific sampling
steps must be followed, including how many wipes will constitute a sample, how much solvent
to apply to the wipe, what pattern the area should be wiped in, and the amount of area that should
always be wiped. This review did not attempt to investigate sampling designs, or data quality
objectives, as this was outside the scope of this study, but these are aspects that must also be
considered when applying a wipe sampling method.
6.3 Conclusions
Based on the findings of this literature review, it is clear that there is not an overwhelming
consensus on how to take a wipe sample for collecting CWAs, OP pesticides, and other TICs
from surfaces. Different methods, media, and wetting solvents have been recommended and
used by various groups and studies. Many of the compounds in Table 1 do not even have a
specific wipe sampling methodology for their collection. If the goal is to establish a wipe
sampling method (or methods) for the compounds discussed in this report, then the next steps in
this process must be research to investigate and fill in the gaps in wipe sampling knowledge that
exist, followed by method validation to optimize the methods.
38
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Chapter 7
References
1. Munro, N. B., S. S. Talmage, G. D. Griffin, L. D. Waters, A. P. Watson, J. F. King, and V.
Hauschild, 1999. The Sources, Fate and Toxicity of Chemical Warfare Agent Degradation
Products. Environmental Health Perspectives. 107:933-97.
2. Abercrombie, P. L., 2003. Physical Property Data Review of Selected Chemical Agents and
Related Compounds: Updating Field Manual 3-9. ECBC-TR-294.
3. Boomer, B. A., M. D. Erikson, S. E. Swanson, G. L. Kelso, D. C. Cox, and B. D. Schultz,
1985. Verification ofPCB Spill Cleanup by Sampling and Analysis. EPA-560/5-85-026. U.S.
Environmental Protection Agency, Office of Toxic Substances, Washington, DC.
4. Kelso, G. L., M. D. Erickson, and D.C. Cox, 1986. Field Manual for Grid Sampling ofPCB
Spill Sites to Verify Cleanup. EPA-560/5-86-017. U.S. Environmental Protection Agency,
Office of Toxic Substances, Washington, DC.
5. McArthur, B., 1992. Dermal Measurement and Wipe Sampling Methods: A Review. Applied
Occupational and Environmental Hygiene. 7(9): 599-606.
6. ARCADIS G&M, Inc., 2005. Evaluation of the Effectiveness of Coating in Reducing
Dislodgeable Arsenic, Chromium, and Copper from CCA-Treated Wood. Prepared for U.S.
Environmental Protection Agency, Air Pollution Prevention and Control Division, Research
Triangle Park, NC.
7. ASTM, 2003. E1728-03 Standard Practice for Collection of Settled Dust Samples Using
Wipe Sampling Methods for Subsequent Lead Determination. Annual Book of Standards.
Vol. 04.12.
8. Brookhaven National Laboratory, 2006. Surface Wipe Sampling Procedure. IH75190.
www.bnl.gov/esh/shsd/sop/pdf/IH_SOPS/ffl75190.pdf
9. Federal Register, 2006. Vol. 71, No. 6. 40 CFR Part 745. January 10, 2006.
10. American Society for Testing Materials, 2001. D6661-01 Standard Practice for Field
Collection of Organic Compounds from Surfaces Using Wipe Sampling, May 2006. Annual
Book of Standards. Vol. 11.04.
39
-------
11. U.S. Department of Agriculture, 2003. Collecting Wipe Samples for Residue Analysis. SOP
No. EM-24.
12. Morgan, M. K., L. S. Sheldon, C. W. Croghan, J. C. Chuang, R. A. Lordo, andN. K. Wilson.
A Pilot Study of Children's Total Exposure to Persistent Pesticides and Other Persistent
Organic Pollutants (CTEPP). U.S. Environmental Protection Agency, Air Pollution
Prevention and Control Division, Research Triangle Park, NC.
(http://www.epa.gov/heasd/ctepp/index.htm).
13. Gordon, S., P. Callahan, M. Nishioka, M. Brinkman, M. K. O'Rourke, M. Lebowitz, and D.
Moschandreas, 1999. Residential environmental measurements in the National Human
Exposure Assessment Survey (NHEXAS) pilot study in Arizona: preliminary results for
pesticides and VOCs. Journal of Exposure Analysis and Environmental Epidemiology. 9:
456-470.
14. Black, K. G., and R. A. Fenske, 1996. Dislodgeability of Chlorpyrifos and Fluorescent
Tracer Residue on Turf: Comparison of Wipe and Foliar Wash Sampling Techniques.
Archives of Environmental Contamination and Toxicology. 31: 563-570.
15. Nishioka, M., H. Burkholder, M. Brinkman, S. Gordon, and R. Lewis, 1996. Measuring
Transport of Lawn-Applied Herbicide Acids from Turf to Home: Correlation of Dislodgeable
2,4-D Turf Residues with Carpet Dust and Carpet Surface Residues. Environmental Science
& Technology. 30(11): 3313-3320.
16. Nishioka, M., R. Lewis, M. Brinkman, H. Burkholder, C. Hines, and J. Menkedick, 2001.
Distribution on 2,4-D in Air and on Surfaces inside Residences after Lawn Applications:
Comparing Exposure Estimates from Various Media for Young Children. Environmental
Health Perspectives. 109(11): 1185-1191.
17. U.S. Department of Labor Occupational Safety & Health Administration. Evaluation
Guidelines for Surface Sampling Methods. OSHA Salt Lake City Technical Center, Salt Lake
City, UT.
18. U.S. Department of Labor Occupational Safety & Health Administration. OSHA Technical
Manual. TED 01-00-015 [TED 1-0.15A]. OSHA Salt Lake City Technical Center, Salt Lake
City, UT.
19. Buttner, M.P., P. Cruz, L. D. Stetzenbach, A. K. Klima-Comba, V. L. Stevens, and T. D.
Cronin, 2004. Determination of the Efficacy of Two Building Decontamination Strategies by
Surface Sampling with Culture and Quantitative PCR Analysis. Applied and Environmental
Microbiology. 70(8):4740-4747.
20. Sanderson, W. T., M. J. Hein, L. Taylor, B. D. Curwin, G. M. Kinnes, T. A. Seitz, T.
Popovic, H. T. Holmes, M. E. Kellum, S. K. McAllister, D. N. Whaley, E. A. Tupin, T.
Walker, J. A. Freed, D. S. Small, B. Klusaritz, and J. H. Bridges, 2002. Surface Sampling
Methods for Bacillus anthracis Spore Contamination. Emerging Infectious Diseases.
40
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21. Minnesota Department of Health, Minnesota Pollution Control Agency, 2006. Clandestine
Drug Lab General Cleanup Guidance. (July 2006).
22. Washington State Department of Health, 2005. Guidelines for Environmental Sampling at
Illegal Drug Manufacturing Sites. (November 2005).
23. Chavalitnitkul, C., and L. Levin, 1984. A Laboratory Evaluation of Wipe Testing Based on
Lead Oxide Surface Contamination. American Industrial Hygeine Association Journal.
45(5):311-317.
24. Vostal, J.J., E. Taves, J.W. Sayre, and E. Charney, 1974. Lead Analysis of House Dust: A
Method for the Detection of Another Source f Lead Exposure in Inner City Children.
Environmental Health Perspectives. 7:91-97'.
25. Fenske, R.A., P.B. Curry, F. Wandelmaier, and L. Ritter, 1991. Development of Dermal and
Respiratory Sampling Procedures for Humans Exposure to Pesticides in Indoor
Environments. Journal of Exposure Analysis and Environmental Epidemiology. 1(1):11-30.
26. American Society for Testing Materials, 2006. D5438-05 Standard Practice for Collection of
Floor Dust for Chemical Analysis, October 2006. Annual Book of Standards. Vol. 11.03.
27. Camann, D., H. Harding, P. Geno, and S. Agrawal, 1996. Comparison of Methods to
Determine Dislodgeable Residue Transfer from Floors. EPA/600/SR-96/089. U.S.
Environmental Protection Agency, National Exposure Research Laboratory, RTF, NC
(August 1996).
28. Fortune C., 1998. Round-Robin Testing of Methods for Collecting Dislodgeable Residues
from Carpets. EPA/600/SR-97/107. U.S. Environmental Protection Agency, National
Exposure Research Laboratory, RTF, NC (January 1998).
29. Nishioka, M., H. Burkholder, M. Brinkman, and R. Lewis, 1999. Distribution of 2,4-
Dichlorophenoxyacetic Acid in Floor Dust throughout Homes Following Homeowner and
Commercial Lawn Applications: Quantitative Effects of Children, Pets, and Shoes.
Environmental Science and Technology. 33(9): 1359-1365.
30. Lu, C., and R. Fenske, 1999. Dermal Transfer of Chlorpyrifos Residues from Residential
Surfaces: Comparison of Hand Press, Hand Drag, Wipe, and Polyurethane Foam Roller
Measurements after Broadcast and Aerosol Pesticide Applications. Environmental Health
Perspectives. 107(6): 463-467.
31. Lioy, P. J., R. D. Edwards, N. Freeman, S. Gurunathan, E. Pellizzari, J. L. Adgate, J.
Quackenboss, and K. Sexton, 2000. House dust levels of selected insecticides and a herbicide
measure by the EL and LWW samplers and comparisons to hand rinses and urine
41
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metabolites. Journal of Exposure Analysis and Environmental Epidemiology. 10: 327-340.
32. Lemley, A. T., A. Hedge, S. K. Obendorf, S. Hong, J. Kim, T. M. Muss, and C. J. Varner,
2002. Selected Pesticide Residues in House Dust from Farmers' Homes in Central New York
State, USA. Bulletin of Environmental Contamination and Toxicology. 69: 155-163.
33. Clark, J. M., J. Bing-Canar, S. Renninger, R. Dollhopf, J. El-Zein, D. Star, D. Zimmerman,
A. Anisuzzaman, K. Boylan, T. Tomaszewski, K. Pearce, R. Yacovac, B. Erlwein, and J.
Ward, 2002. Methyl Parathion in Residential Properties: Relocation and Decontamination
Methodology. Environmental Health Perspectives. 110(6): 1061-1070.
34. Wasley, A., L. A. Lepine, R. Jenkins, and C. Rubin, 2002. An Investigation of Unexplained
Infant Death in Houses Contaminated with Methyl Parathion. Environmental Health
Perspectives. 110(6): 1053-1056.
35. Opstad, A. M., B. Pedersen, and J. A.Tornes, 1999. Sampling of Solid Surfaces After an
Alleged Use of Chemical Warfare Agent. FFI/RAPPORT-99/04423. Norwegian Defense
Research Establishment, Kjeller, Norway.
36. Swahn, L, 2000. QDOC/LAB/WI/SC005. Work Instruction for Collection of Wipe Samples
On-Site. Organization for the Prohibition of Chemical Weapons.
37. Sample Preparation Method for GC/MS Analysis On Site Joint Document: United
States/Finland, Volume 1 February 1996 - December 1997. Prepared for Defense Threat
Reduction Agency, U.S. Department of Defense.
38. Rohrbaugh, D. K., K. B. Sumpter, and M. W.Ellzy, 2003. Chemical Weapons Convention
Verification Technology Research and Development. Evaluation of a Proposed Joint
US/Finnish Method for Extraction of Chemical Agents and Their Degradation Products from
Wipe Samples. ECBC-TR-315. Prepared for Defense Threat Reduction Agency, Fort Belvoir,
VA. (May 2003).
39. Matt, G. E., P.J.E. Quintana, M. F. Hovell, J. T. Bernert, S. Song, N. Novianti, T. Juarez, J.
Floro, C. Gehrman, M. Garcia, and S. Larson, 2004. Households contaminated by
environmental tobacco smoke: sources of infant exposures. Tobacco Control. 13:29-37.
42
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APPENDIX A
CHEMICAL STRUCTURES FOR THE COMPOUNDS OF
INTEREST
A-l
-------
o
aJL<
[ \\
Cl (-
a N CH,
1,4-Dithiane
1,4-Thioxane
Chloropicrin
Crimidine
ci
o
H3C
O — P — O Cl
/ 1
VCH,
CH,
H,C - O — P — O
O
I
CH,
CH,
CH3 O
Hf—O — P—O- CH3
H3C
Cl Cl
Dichlorovos
Dicrotophos
Dimethyl Phosphite Ethyldichloroarsine (ED)
A-2
-------
H-,C
/
NH
CH,
Fenamiphos
" CH,
Cl
CH,
Cl
As
I
Cl
Cl
Cl
Lewisite (1)
Cl
a
a
ci
Lewisite (2)
Lewisite (3)
. CH,
0 — P —0
A
'CH,
Cl
Cl
Methyl Fluoroacetate Methyl Parathion Mevinphos
Mustard Gas (H)/
Distilled Mustard (HD)
A-2
-------
Cl
Cl
Cl
Cl
CH,
Mustard (HT)
Nicotine
Phencyclidine (PCP)
s
II
H,C
S CH,
H,C
H3C
0
II
O — P — CH3
F
O — P — CH,
CH
a CH,
H3C
CH,
O
II
O — P — CH,
Phorate
Sarin (GB)
Cyclohexyl sarin (GF) Soman (GD)
A-4
-------
o
\ II
M — P •
/ I
0
0 0
Strychnine
0
I
'0^0
I
CH,
H3C
CH,
Tabun (GA)
o
H3C
•O',p
^O
CH,
HO
H,C
CH,
Tetraethyl pyrophosphate (TEPP)
HX: — P — S
H3C
CH,
CH,
OH
Thiodiglycol
CH,
Trimethyl phosphite
VX
A-5
------- |