United States
Environmental Protection
Agency
National Exposure Research
Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-97/107 January 1998
Project Summary
Round-Robin Testing of
Methods for Collecting
Dislodgeable Residues from
Carpets
Christopher R. Fortune
A round-robin test was conducted
using six volunteers to evaluate three
dislodgeable residue methods sampling
new carpets treated with a commercial
pesticide formulation. Seven separate
tests were performed, each using a for-
mulation containing three target pesti-
cides (chlorpyrifos, pyrethrin I, and pip-
eronyl butoxide). Strict QA/QC guide-
lines were followed as each participant
collected three replicate samples each
with the polyurethane foam (PDF) roller,
the California roller, and the Dow drag
sled methods. Sampling precision was
high for all three methods for measure-
ments of this type. The overall results
(mean %RSD, relative standard devia-
tion, N=21) show the Dow sled with the
best sampling precision (25.4% RSD),
followed by the California roller (30.7%),
and then the PUF roller (37.9%). Mean
transfer efficiency, the ratio of the
method transfer rate to the pesticide
deposition rate, was highest for the
California roller (5.0%), followed by the
Dow sled (2.1%) and the PUF roller
(1.7%). The mean transfer efficiency
rates in this study were substantially
higher than those reported in earlier
studies of this type.
Information relating to ease of use,
simplicity, time requirements, and other
criteria for each of the test methods
was obtained from written subjective
evaluation and critique by each volun-
teer. A compilation of that information
revealed that both the Dow sled and
PUF roller methods were rated highly
and equal to one another, while the
California roller was rated lower. Fur-
ther testing is recommended to deter-
mine the effect on transfer efficiency
rates due to carpet age, type and prior
cleaning or chemical treatment.
This Project Summary was developed
by EPA's National Exposure Research
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
A recent study was conducted to test
the performance of three dislodgeable pes-
ticide residue methods on floor surfaces.
One result of that study was a recommen-
dation to conduct a round robin study of
the same three methods, following strict
QA/QC guidelines, using volunteers to
perform the testing and provide written
evaluations of the procedures. This report
presents the results of that round-robin
study using six volunteers.
The PUF roller, the California roller and
the Dow drag sled methods were evalu-
ated. Written standard operating proce-
dures (SOPs) were prepared, tested and
modified, where necessary, for each
method prior to the onset of the testing.
Volunteers were trained in the use of each
procedure just prior to beginning the sam-
pling activities. For each test a new, ny-
lon, plush cut-pile, stain resistant carpet
was treated with a commercial pesticide
formulation used to control a heavy infes-
tation of fleas. Field blank and field spike
samples were collected along with the
replicate samples collected using the three
test methods.
Test samples, along with both field and
laboratory QA/QC samples, were extracted
and then analyzed by a referee laboratory
using a GC/MS SIM mode procedure. The
analytical results for the three target
analytes, chlorpyrifos, pyrethrin I and pip-
eronyl butoxide, were used to calculate
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the method sampling precision and the
transfer efficiency rate for each test pro-
cedure. Upon the conclusion of each test,
the volunteer provided a written evalua-
tion pertinent to a wide variety of specific
performance characteristics for each test
method used in the study.
Study Design
Six volunteers were recruited from local
agricultural and chemical research organi-
zations. Half of the participants were from
large organizations and the other half were
from smaller companies. An 8- x 20-ft
modular trailer unit was leased for use in
performing the tests. Participants were pro-
vided advanced copies of the SOPs and
general instructions concerning the
planned training and testing activities. On
the morning of each scheduled test, the
staff collected field blanks from a new 6- x
14-ft carpet test sample and then treated
the carpet with the freshly prepared test
formulation. A mixture of 0.5% chlorpyrifos,
0.05% pyrethrin I, and 0.5% piperonyl bu-
toxide was sprayed on the carpet surface
at a manufacturer's recommended rate of
1 gal/1600 ft2. The carpet was divided into
three equal sections for sampling layout
purposes, and a 4- x 4-in. a-cellulose
deposition coupon was placed in each
section prior to spraying in order to pro-
vide a measure of the actual pesticide
deposition rate for each test.
Shortly after arriving at our test facility,
the volunteers were given a thorough dem-
onstration and hands-on familiarization
session with the three dislodgeable resi-
due test methods. After a 4 hour drying
period and complete ventilation, the test-
ing session was initiated. A set of field
spikes of each of the four sample matri-
ces was collected in the laboratory. The
volunteers then performed the replicate
sampling using each test method to col-
lect one sample in each of the three sec-
tions of the test carpet. The exposed depo-
sition coupons were collected from each
section individually at the time test samples
were collected.
All samples were stored in pre-labled
containers, packed on dry ice, and shipped
to the laboratory by overnight express de-
livery service. Participants were debriefed
following the testing and were asked to
rate the test procedures by filling out ques-
tionnaires provided for that purpose.
The analytical laboratory services were
provided by Southwest Research Institute,
San Antonio, TX. Having had previous
experience in studies of this kind, the labo-
ratory followed written protocols in per-
forming the extraction and GC/MS analy-
sis of the test samples and laboratory QA/
QC samples. The resulting data were used
to determine the overall quality of the
sample extraction and analysis procedures,
the uniformity of pesticide applications, and
the overall sampling precision and trans-
fer efficiency of each test method under
evaluation.
Test Methods
a-Cellulose Deposition Coupon
The deposition coupons used were 100-
mm squares of cellulose filter paper at-
tached to aluminum foil-covered backing
sheets of the same size. Each coupon
was marked by pencil line so that a 12.5-
mm (0.5 in.) border on all sides was avail-
able to allow handling. Prior to extraction,
the coupon border was trimmed away to
leave a 75-mm square (56.25 cm2) filter
sample for analysis in the laboratory. Esti-
mates of the deposition rate for a given
sample were determined from the ratio of
the mass of pesticide residue found on
the coupon to its area and were usually
reported in units of micrograms per square
centimeter.
PUF Roller
The PUF roller dislodgeable residue
sampling method used a prototype me-
chanical apparatus having two rear wheels,
a cylindrical aluminum roller at the front,
and a handle for pushing or pulling at-
tached at the rear. Two stainless steel
blocks (total weight = 3.875 kg) were at-
tached to the center portion of the frame.
A polyurethane foam (PUF) ring measur-
ing 90-mm o.d.- x 30-mm i.d.- x 76 mm in
length was fitted onto the aluminum cylin-
der, which was then attached to the front
of the sampler assembly.
The location of the sample was marked
on the test surface by placing a metal
guidebar adjacent to the planned track of
the device. The 100-cm sample traverse
distance was marked off in 10-cm seg-
ments on the bar. A solvent-washed thin
aluminum sheet was placed at the start-
ing position to serve as a platform to hold
the PUF roller before starting the test.
A sample traverse consisted of two
passes, one forward and one backward,
over the 100 cm pathlength. At the end of
the second pass, the roller was immedi-
ately lifted off the carpet. The aluminum
cylinder was then detached from the as-
sembly and the PUF ring was recovered
and stored in its container. The marks at
10 cm intervals on the guidebar were used
to maintain the sampling rate at about 10
cm/s.
California Roller
The California roller method used a de-
vice resembling a large rolling pin to col-
lect surface dislodgeable residues on a
percale sheet cloth matrix. The roller con-
sisted of a 63-cm-long PVC pipe, 13 cm
in diameter, fitted with PVC endcaps hav-
ing roller handles. The roller was covered
with a 1-cm thick foam cover, 51 cm in
length, and is filled with a quantity of small
to medium-size steel ball bearings suffi-
cient to bring the total weight of the roller
to 25 Ib.
The sampling medium, consisting of a
precleaned 17- x 17-in. cloth cut from
percale bedsheet material (50% combed
cotton, 50% FortrelŪ polyester, 180 thread
count), was placed flat on the carpet sur-
face and covered with a plastic sheet (e.g.
medium-size plastic trash bag, 20- x 24-
in.) Sampling$"as performed by moving
the roller back and forth ten times at a
steady rate over the sample medium (20
total passes). A special metal handle as-
sembly was fabricated for use in these
tests to permit the operator to more com-
fortably move the roller without exerting
any downward pressure on the handles.
After the final sample pass, the roller and
handle assembly were removed from the
test area, the plastic sheet discarded and
forceps used to collect and fold the per-
cale cloth for insertion into its sample con-
tainer.
Dow Drag Sled
The Dow drag sled procedure used a 3-
x 3-in. piece of 3/4-in. thick plywood as
the base for a sled with a ridge contructed
on the top to hold an 8-lb round downrigger
weight. A screw eye was placed in the
center of one edge of the block, to which
a 24-in. long wire and pull handle were
attached. The base and sides of the sled
were covered with two layers of aluminum
foil attached with staples.
The sampling media consisted of
precleaned 4- x 4-in. undyed cotton denim
cloth squares. A thin aluminum sheet start-
ing platform and a guidebar were used
with the Dow sled procedure. A sample
traverse consisted of a single pass with
the sled over a distance of 48 in. using
guide marks at 4 in. intervals to achieve
an approximate sampling rate of 10 cm/s.
The denim cloth sampling media was
attached to the base of the sled by using
plastic-headed pushpins positioned
through the overlapping edges of the cloth
and into the front and sides of the wooden
sled. With the denim cloth securely in
place, the sled was placed on the alumi-
num starting platform, and the 8-lb. weight
was put into its position on top of the sled.
The drag line was then attached to the
screw eye on the front of the sled. Keep-
ing the drag line at a low angle relative to
the floor, the operator pulled the sled for-
ward at a steady rate until the front of the
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sled reached the 48-in. mark on the
guidebar. The sled was then quickly lifted
from the carpet surface and the denim
cloth was removed from the sled, folded
and stored in its container.
Sample Analysis
Test samples were prepared for analy-
sis by Soxhlet extraction in ether: n-hex-
ane (6:94) for 16 hours followed by a
Florisil cleanup. A surrogate compound (p
terphenyl-d14) was added to each sample
as a QC check on the process.
Analysis was performed with a Fisons
VG MD800 GC/MS instrument in selected
ion monitoring mode. A DB-5 column, 0.25-
mm-i.d. - x 30-m, was used for the analy-
sis. Quantitation was based on a five-
point standard calibration curve, and con-
tinuing calibration was performed by us-
ing the mid level standard.
Results and Discussion
The analytical results for blanks, field
spikes, surrogate recoveries, and GC/MS
calibrations were acceptable for all seven
sets of test samples analyzed. Pesticide
formula applications were uniform with the
results of deposition coupon analysis yield-
ing an average of 23% RSD for three
replicates per test.
The results for method sampling preci-
sion, shown in Table 1, indicate that all
three methods achieved relatively good
precision. From a total of 63 sets of tripli-
cate results (7 tests x 3 methods x 3
pesticides), the overall average sampling
precision was 31.3% RSD (range = 2.4
86.1% RSD). The Dow sled achieved the
best sampling precision with an average
of 25.4% RSD, followed by the California
roller method at 30.7%, and the PUF roller
at 37.9%. Using the calculated average
deposition rate for each test, the mean
transfer efficiency rate was determined for
the three replicate samples collected us-
ing each test method. The average re-
sults for the seven tests performed in the
study are shown in Table 2. The results
indicate that the transfer efficiency for each
method is generally quite consistent for all
three target pesticides and over the whole
range of subject operators. The California
roller produced the highest transfer effi-
ciency results, with an overall average of
5.0%. The rates for the PUF roller and
Dow sled methods were similar, with the
Dow sled showing only slightly higher val-
ues on average. The PUF roller averaged
a 1.7% tranfer efficiency rate, while the
Dow sled averaged 2.1%. Since both of
these test methods were designed to mimic
the exposure of a 20-lb child to surface
residues, it is not surprising that the trans-
fer efficiency results are similar. The Cali-
fornia roller method seemed to be subject
to problems during execution of the tech-
nique by several operators. On many oc-
casions the dosimeter was observed to
move or slide on the carpet surface dur-
ing the rolling operation. This problem
might account for higher transfer efficiency
results for some of the test samples col-
lected relative to tests during which the
dosimeter remained stationary during the
rolling operation.
Table 1. Round-Robin Test Results Summary - Sampling Precision*
Chlorpyrifos Pyrethrin I Piperonyl Butoxide
Average
PUF Roller
California Roller
Dow Drag Sled
28.3%
27.1%
23.5%
45.7%
35.2%
26.8%
39.7%
29.7%
25.8%
0.379
0.307
0.254
* Mean % RSD for 3 replicates per test, average results for 7 tests.
Table 2. Round-Robin Test Results Summary - Transfer Efficiency*
Chlorpyrifos Pyrethrin I Piperonyl Butoxide
Average
PUF Roller
California Roller
Dow Drag Sled
1.4%
4.2%
1.9%
1.9%
4.2%
2.1%
1.8%
6.6%
2.3%
1.7%
5.0%
2.1%
' Mean % transfer for 3 replicates per test, average results for 7 tests.
The results of this study were com-
pared to those of the study that led to the
recommendation for this round robin test.
The results for transfer rates of the three
test methods were similar in both studies
for tests on new carpets. In the earlier
study, however, tests performed on car-
pets that were used and then repeatedly
cleaned by chemical treatment yielded
transfer rates that were ten times lower
than those from tests on new carpets.
The volunteers in the round robin study
provided a written evaluation of all three
test methods following completion of the
testing. The methods were rated numeri-
cally as to (a) ease of use, (b) conve-
nience, (c) transporting apparatus in the
field, and (d) ease of handling the sample
media. Responses were also obtained per-
taining to the time requirements and sim-
plicity of each method. The California roller
method was consistently rated lower in
every catergory, while the PUF roller and
Dow sled methods were generally rated
highly and about equal to one another.
Conclusions and
Recommendations
1. The volunteers were readily able to
perform the dislodgeable residue
sampling procedures with only mini-
mal prior orientation and instruc-
tion.
2. The pesticide application procedure
used for each of the seven round-
robin tests yielded uniform results.
The average deposition rate
(mean+SD, u,g/cm2) was 17.8+4.1
for Chlorpyrifos, 1.33+0.61 for pyre-
thrin I, and 10.1+2.3 for piperonyl
butoxide.
3. One of the primary objectives of
this study was to determine the level
of sampling precision that could be
attained with each of the test meth-
ods when used by typical opera-
tors under controlled conditions. As
measured by the calculated %RSD
for three replicate samples, the Dow
sled method registered the highest
overall sampling precision (25.4%
RSD). The PUF roller method reg-
istered the lowest sampling preci-
sion (37.9% RSD), and results for
the California roller method, modi-
fied to include use of a custom
handle assembly, were slightly bet-
ter than the average (30.7% RSD).
4. The other main objective criterion
measured by the results from the
round-robin testing was that of
method transfer efficiency. Trans-
fer efficiency is defined as the ratio
of a method's transfer rate (|ig/cm2)
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to the deposition rate (|ig/cm2) as 6.
determined by the mean value for
three deposition coupons. The
mean transfer efficiency for the Cali-
fornia roller was high (5.0%), while
the PUF roller and the Dow sled
mean transfer efficiencies were
nearly identical at 1.7% and 2.1%,
respectively.
5. Transfer efficiency for all three
dislodgeable residue test methods
was higher by about one order of
magnitude in the round robin tests 7.
on new carpets as compared to
that determined in similar experi-
ments performed on used carpets
in an earlier study of this type.
Method transfer rate, the ratio of
the amount (|ig) of pesticide col-
lected to the area (cm2) of carpet
surface traversed by the sampler,
may be profoundly influenced, as
the earlier work suggests, by the
type, age, and prior surface treat-
ment of the carpets being tested.
The results of subjective evalua-
tions of the three test methods by
the six round-robin test volunteers
indicated a clear consensus in rat-
ing the California roller method
lower overall as compared to the
PUF roller and Dow sled methods.
The latter two methods were rated
highly and almost equal to one an-
other according to the volunteers'
responses to criteria addressed in
the opinion survey.
The quantitative results of the study
along with the subjective evalua-
tions by the volunteers lead to the
conclusion that the California roller
method is the least suitable of the
three test methods for sampling
dislodgeable residue on carpets. Its
high transfer efficiency (5.0%) is
less representative of actual human
skin transfer efficiency, and the
method involves bulky equipment
that is difficult to use. Both the PUF
roller and the Dow drag sled meth-
ods performed well and are consid-
ered equally suitable.
8. Although the results of this study
show that reproducible and consis-
tent data can be obtained for
dislodgeable pesticide residues on
new carpet by using any of the
three test methods under evalua-
tion, the substantial difference in
measured transfer efficiency rates
between this study and one con-
ducted earlier are cause for con-
cern. We therefore recommend that
tests be conducted with one or more
of the residue sampling methods
on both new and used carpets of
varying types, including carpets that
have, and have not, been chemi-
cally treated.
The work reported herein was performed
by ManTech Environmental Technology,
Inc., under U.S. Environmental Protection
Agency Contract 68-D5-0049, and by
Southwest Research Institute under Sub-
contract 96-0049-01 to ManTech.
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ChristopherR. Fortune is with ManTech Environmental Technology, Inc., Research
Triangle Park, NC 27709
Robert G. Lewis is the EPA Project Officer (see below).
The complete report, entitled "Round-Robin Testing of Methods for Collecting
Dislodgeable Residues from Carpets,"(OrderNo. PB98-117989; Cost: $21.50,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
National Exposure Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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