United States
               Environmental Protection
               Agency	
Risk Reduction
Engineering Laboratory
Cincinnati. OH 45268
               Research and Development
EPA/600/SR-92/049   April 1992
EPA       Project  Summary
               Permeation  of  Multifunctional
               Acrylates through  Three
               Protective  Clothing  Materials
               Rosemary Goydan and Thomas Stolki
                Permeation tests were conducted
               with trimethylolpropane triacrylate
               (TMPTA),  1,6-hexanedioI diacrylate
               (HDDA), arid two mixtures  of  1,6-
               hexanediol diacrylate with 2-ethylhexyl
               acrylate (EHA) to better understand the
               permeation behavior of multifunctional
               acrylate compounds.  The tests were
               conducted using the ASTM F739-85 per-
               meation method with a silicone rubber
               sheeting material as the collection me-
               dium because of the  low vapor pres-
               sure and low water solubility of the
               acrylate compounds. Permeation tests
               were performed at 20°C with butyl, ni-
               trile, and natural rubber glove materi-
               als. None of the acrylate compounds
               nor mixtures was detected to permeate
               the butyl or nitrile rubber at the condi-
               tions and sensitivity of the method. Per-
               meation of the natural rubber  was de-
               tected in tests with pure HDDA, a  50%
               HDDA/50% EHA mixture, and a  25%
               HDDA/75% EHA mixture. TMPTA  per-
               meation through the natural rubber was
               also detected but only in one of the
               triplicate tests after the 360-480  min
               sampling interval. For pure HDDA, the
               breakthrough detection time was 30-60
               min and the steady-state  permeation
               rate was 0.92 jig/cm2-mih. For  the
               HDDA/EHA mixtures,  permeation of
               both mixture components was detected
               at the same time in each test. The break-
               through detection time was 30-60  min
               for  the 50% HDDA/50% EHA  mixture
               and was from 15-30 to 30-60  min for
               the 25% HDDA/75% EHA mixture.  The
               HDDA  steady-state permeation rates
               from the mixtures were somewhat
               higher  than that  measured for pure
HDDA: 1.02 ng/cm2-min for  the 50%
HDDA/50% EHA mixture and 1.35 jig/
cmz-min for the 25% HDDA/75% EHA
mixture. The slight increase in perme-
ation rate is attributed to the presence
of the  more rapidly permeating EHA
carrier solvent, which has a permeation
rate of 11.7 uxj/cntf-min from the 50%
HDDA/50% EHA mixture and 20.0 ng/
cm2-min from the 25% HDDA/75% EHA
mixture. Permeation tests with pure
EHA, however, were not performed.
  This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).

Introduction
  Section 5 of the Toxic Substances Con-
trol Act requires prospective manufactur-
ers or importers of new chemicals to sub-
mit Premanufacture Notifications (PMNs),
which are reviewed by the EPA Office of
Toxic  Substances (OTS) before their
manufacture or  import. One objective of
the review is to assess the potential risks
to human health that could result from
dermal or inhalation exposures during the
manufacture, processing, and end use of
the PMN chemical. In those cases in which
the PMN submitter recommends protec-
tive'clothing as a way to minimize dermal
contacts, OTS evaluates the ability of the
protective clothing  to act as a barrier to
the PMN chemical.  Since 1985, the EPA
Office of Research  and Development, in
support of OTS,  has explored approaches
to developing predictive models, test meth-
                                                              Printed on Recycled Paper

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ods, and data review procedures for esti-
mating protective clothing barrier proper-
ties. Chemical permeation of clothing ma-
terials has been the focus because it is an
important mechanism by which chemicals
can move through protective clothing. OTS
can, when available, use permeation data
for the  PMN substance or for  a  similar
compound to judge permeation resistance.
The  PMN submitter,  however, is not re-
quired to provide data that demonstrate
acceptable clothing permeation resistance.
For most PMN substances, therefore, suit-
able permeation data are not available to
judge permeation resistance.
  OTS identified a specific  need for per-
meation data for the general class of com-
pounds known as multifunctional acrylates.
Several recent PMN submissions have in-
volved such compounds, and a search of
the literature and  databases uncovered
essentially no permeation data for these
compounds. Consequently, OTS selected
several  representative multifunctional ac-
rylates and requested that permeation tests
be performed to establish  a better basis
for estimating the permeation behavior of
such compounds. Performing these tests
is not routine, however, because of the
solubility and physical properties  of the
compounds. Similar to many organophos-
phorus pesticides, multifunctional acrylates
nave low vapor pressure and low water
solubility. Thus, a collection medium other
than those now specified by ASTM F739—•
water or an inert gas—must be used  to
perform permeation tests. A silicone rub-
ber sheeting material has been used suc-
cessfully as an alternative collection me-
dium and was used here.
  In this study we measured the perme-
ation of TMPTA, HDDA, and mixtures  of
HDDA with EHA, an  acrylate carrier sol-
vent, through 3 protective clothing materi-
als:  butyl rubber, natural rubber, and ni-
trile  rubber. The laboratory program re-
quired  a methods development task be-
fore performing the permeation tests:
  • to establish the collection capacity and
    efficiency of the silicone sheeting for
    the acrylate compounds, and
  • to validate the methods for extracting
     and quantifying the amounts of the
    acrylate  compounds that permeate
     and are collected by the silicone
    sheeting. •
The data generated in this study  are in-
tended for  use by OTS to  better under-
stand the permeation of  multifunctional
acrylates through protective clothing ma-
terials.
Experimental Methods and
Procedures

Materials
  Permeation tests were conducted with
two multifunctional acrylates, TMPTA and
HDDA,  as  pure chemicals. Tests  were
also conducted with two mixtures of HDDA
with EHA: 50% HDDA/50% EHA and 25%
HDDA/75% EHA. The mixtures were pre-
pared on a percent volume basis.  Proper-
ties of these compounds are given in Table
1. The permeation tests were conducted
with 3 protective clothing materials: butyl
rubber, natural rubber, and nitrile rubber.
Descriptions and sources of these cloth-
ing  materials are provided in Table2.

Permeation Test Procedure
  The permeation tests were conducted
according to ASTM Method F739-85 with
a modification for collecting low water solu-
bility, low vapor pressure permeants. In a
previous EPA study,  several  candidate
media were evaluated for the efficient col-
lection of the low water solubility, low vola-
tility pesticides. These studies found that
a commercially available, 0.051-cm (0.02-
in.)  silicone  rubber sheet material
(Silastic®, Dow Corning Corporation') was
more efficient at collecting the permeating
materials than were the other collection
media evaluated: aqueous solutions con-
taining surfactants or other solubilizing
compounds, filter  paper,  and synthetic
gauze.
  The  ASTM  permeation  test cell  was
modified by replacing the standard collec-
tion chamber of the cell with a 7.62-cm (3-
in.) long section of flanged 5.08-cm (2-in.)
ID glass pipe.  Thus, the standard ASTM
F739  clothing  material surface area for
chemical contact was  maintained at 20.3
cm2. The silicone rubber sheeting material
used as the collection  medium was cut to
the size of the pipe ID and placed on the
collection side of the protective clothing
material to be tested. A tight-fitting,  2.54-
cm (1-in) long Teflon® piston was placed
in the glass pipe to ensure good contact
of the silicone rubber disc  with the  cloth-
ing material and to minimize evaporation
of the permeant collected.  The challenge
side of the  test cell was  also modified to
minimize the handling of large challenge
chemical volumes.The standard challenge
chamber was  replaced with a stainless
1  Mention of trade names or commercial products does
  not constitute endorsement or recommendation for
  use.
steel plate machined  to  hold 10  mL of
challenge solution. The challenge  cham-
ber is connected through an overflow line
to a vial containing additional challenge
solution to ensure both a continuous chal-
lenge and a closed system. A schematic
of the modified test cell is shown in  Figure
1.
  The collection medium was sampled by
using stainless steel forceps to remove
the silicone rubber disc after a predeter-
mined sampling period. In these tests, the
silicone rubber discs were removed and
replaced with fresh discs at 0, 15, 30, 60,
120, 180, 240, 360, and 480 min. After
removal, each collection disc was trans-
ferred to a screw cap vial for extraction
and analysis. Each test was conducted in
triplicate and  concluded  after  480 min.
The permeation tests  were  performed at
20°C in a controlled temperature and hu-
midity laboratory.

Collection Medium  Extraction
and Analysis Sequence
  The collection medium  samples  re-
moved from the permeation test cell were
placed in individual vials and  extracted
with 10 mL of isopropanol (Fisher  Scien-
tific ACS grade).  The  samples were ex-
tracted for 30 min with sonication.  An ali-
quot of the isopropanol extract was then
analyzed, without concentration, to deter-
mine the concentration of the permeant.
For each permeation test set (i.e., each
set of triplicate samples at the 9 sampling
intervals over the 480 min test duration),
the 240 min samples were first extracted
and analyzed to determine  if permeation
was detected. If measurable quantities of
permeant(s) were detected  in  any of the
three replicates, all remaining samples for
that set were analyzed. If no measurable
quantities of permeant were detected in
the 240 min samples,  only the  180, 360,
and 480 min samples were analyzed. At
this  point,  if  permeant was detected in
any of the 180 min samples, the remain-
ing samples (0, 15, 30, 60, and 120 min)
were also analyzed.

Analytical Methods
  Gas chromatographic/FID methods were
validated and used to  determine TMPTA,
HDDA,  and EHA  concentrations  in the
collection medium extracts.

Quality Assurance and Control
Procedures
  To determine the method detection limit
(MDL),  we analyzed seven replicates of

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Table 1. Chemical Properties*
Chemical name/
CAS Registry No.
TMPTA
CAS No. 1S62S-89-5
HDDA
Molecular
weight
(daltons)
296.32
226.28
Liquid
density f
(g/mL)
1.11
1.01
Vapor
pressure *
(mm Hg)
0.01
0.05
Solubility
in water*
Insoluble
Insoluble
CAS No. 13048-33-4

EHA
CAS No. 103-11-7
184.28
                0.89
                               0.1
Insoluble
'  Chemical source: Aldrich Chemical Company, Milwaukee, Wl.
* At20PC.
Table 2. Glove Materials Tested
                                                                  Thickness
Generic material
Butyl rubber
Natural rubber
Nitrite rubber
Manufacturer
North
Pioneer
Edmont
Model
Butyl
Ivory White L-1 18
Solvex37-155 '•
. Nominal
(cm)
0.041
0.046
0.038
Actual
(cm)
0.046
0.048
0.037
the spiked silicone rubber matrix  at or
near an estimated detection limit. The stan-
dard deviation of the concentration values
for the seven spiked samples was used to
calculate the MDL The precision and ac-
curacy of the analytical method were es-
tablished by analyzing four spiked silicone
rubber samples each at three concentra-
tion levels: 2 x MDL, 5 x  MDL, and 10 x
MDL.  These samples were analyzed over
2 consecutive days. From the spiked sili-
cone  results, the average percent recov-
ery (P), the standard deviation of the av-
erage percent recovery (Sp), and the rela-
tive standard deviation (RSD) were calcu-
lated.  The  accuracy  of the method was
defined as a percent recovery interval from
P - 2Sp to P + 2Sp. The RSD was used to
assess the precision  of the method. The
results of the method validation effort are
summarized in Table 3. These results met
the quality assurance  objectives  estab-
lished for this laboratory program.
  Quality assurance  and control proce-
dures  followed throughout the test  pro-
gram included daily analysis of calibration
standards and a spiked silicone standard,
analysis of replicate samples, and the mea-
surement of permeant "absorbance." In
addition  to characterizing  the  average
permeant recovery in spiking tests, we
attempted to measure the absorbance or
                 the mass of  chemical  absorbed by the
                 silicone rubber versus the total mass of
                 chemical that permeates through the cloth-
                 ing material during each permeation test.
                 At the  end of the 360-480 min sampling
                 period, we rinsed the collection medium
                 side of the clothing material sample with
                 chilled isopropanol and analyzed the rinse
                 for  the permeant.  The absorbance was
                 calculated as:
                                                    ua
                    Absorbance-(%) = 100 x.
    TMPTA
     The results of the TMPTA permeation
    tests with natural rubber, reported in Table
    5, show that TMPTA permeation was de-
    tected in one of the 3 replicate tests in the
    360-480 min sample. No TMPTA was de-
    tected in any of the isopropanol rinses of
    the natural rubber samples at the conclu-
    sion of  the permeation tests (i.e., absor-
    bance equalled 100%).

    HDDA
     The results of the permeation tests with
    pure HDDA, also reported in Table 5, show
    that in  two  of  the replicates the  HDDA
    was first detected in the 30-60 min sample.
    In the third replicate, the HDDA was de-
    tected first in the 60-120 min sample. In
    the subsequent samples, the cumulative
    permeation increased and approached a
    linear permeation rate by the 360-480 min
    sample  interval. The slope of the cumula-
    tive  permeation curve from the 240-360
    min  sample to the 360-480  min sample
    was used to calculate the average steady-
    state permeation rate of  0.92 u-g/crr^-min.
    As  reported in Table 5,  the average ab-
    sorbance of the HDDA was 87.6%,  indi-
    cating that the amount of HDDA found in
    the isopropanol rinses of the natural  rub-
    ber  samples was  small relative  to  the
    amount  collected during the permeation
    test. This result appears to further confirm
    that the  silicone rubber sheeting is a  suit-
    able collection medium for HDDA.

    Mixtures of HDDA and EHA
     No permeation of either HDDA or EHA
    from the mixtures was detected in tests
    with the butyl and nitrile  rubber materials.
    Results  of the permeation tests with  the
    mixtures and natural rubber are summa-
absorbed by silicone
                                               u.g in rinse + ug absorbed by silicone
                 Compound detected in the rinse may rep-
                 resent compound available on the surface
                 of clothing material or compound extracted
                 from the material.  Our objective for the
                 mean absorbance of the permeant  was s
                 80% with  a  coefficient of variation of ±
                 20%.

                 Results
                   The results of the permeation tests, sum-
                 marized in Table 4, indicate that none of
                 the acrylate  compounds or mixtures was
                 detected to permeate the butyl  rubber or
                 nitrile rubber materials. Permeation through
                 the natural rubber material was detected
                 for each challenge compound or mixture
                 and these  results are discussed below.
              rized in Table 6. The results indicate that,
              for the 50% HDDA/50% EHA mixture, per-
              meation of both the HDDA and the EHA
              was first detected at the 30-60 min sam-
              pling interval in all three replicates. Both
              permeants reached a steady-state perme-
              ation rate after the 120-180 min sample.
              The permeation rate of the EHA was much
              higher than that of HDDA from the mix-
              ture: 11.7 (ig/cm2-min versus 1.02 jig/cm2-
              min. The permeation rate  of the  HDDA
              from the 50% mixture is essentially equal
              to that  measured  in the pure HDDA ex-
              periments. Thus, the decrease in concen-
              tration of the  HDDA does not appear to
              affect the permeation rate.  It is important
              to  note, however, that the absorbance

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                                           Piston Holder

                                           Teflon Piston
                                                                        Bolts
                                                  Bolt I
                                          Teflon
                                          Gasket.
                                     Test Material
                                           Centering
                                           Groove
                                                                              Silicone Rubber

                                                                                Clamp
                                                                             Glass Pipe
                                                    \
Challenge
Chemical
Chamber
          Overflow Tubing and
          Containment
1 1 "
1 1 "
^l
1 1
1 1
J 1


\v "^':
:B,;
,_
1— ,
J-* 	 Cl/f I/O/I/O 0
                                                                                     Tubing
Figaro 1. Permeation cell used with silicone rubber collection medium.

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 Table 3. Method Validation Results
                                  TMPTA
                                                   HDD A
                                                                       EHA
 Method Detection Limit

    Concentration in extract             0.74            0.22
    fag/mL)
    Cumulative amount                 0.36            0.11
    permeated per sampling
    interval fog/cnf )*

 Precision and Accuracy *
    Average recovery (%)              98.0            102.2
    Standard deviation (%)              2.4             12.0
    Accuracy                     93.2- 102.8       78.2- 126.2
    Precision (RSD%)                  2.5             11.7
                                          0.20

                                          0.099
                                         92.2
                                          5.0
                                       82.3-102.1
                                          5.4
 *  Calculated from minimum detectable extract concentration fag/mL), 10 mL total extraction
   volume, and 20.3 cm * exposed surface area.
 f  Based on analysis of spiked samples at2x MDL, 5 x MDL, and 10 x MDL on 2 consecutive
   days.
value for the HDDA in these experiments
was low,  only 40.1% on average. This
value is low compared with the average
value for the EHA absorbance in the same
test, 86.9%, and the average value in the
pure  HDDA permeation tests,  87.6%.
Some puckering of the natural rubber ma-
terials was noted after  the 15-30 min
sample. Possibly this puckering prevented
intimate contact of the natural rubber with
the silicone rubber collection medium  so
that the absorbance was  reduced for
HDDA,  which has a low vapor pressure
relative  to  that of EHA  (see Table  1).
            Higher absorbance may have resulted in
            higher permeation values for the HDDA
            from the mixture.
              Similar results were found in the per-
            meation tests with the 25% HDDA/75%
            EHA mixture and the natural rubber mate-
            rial.  Permeation of  both  the HDDA and
            EHA was first detected in the 15-30 min
            samples as reported in Table 6. As shown
            in Figure 2, the permeation of the HDDA
            from this mixture  (and the 50% mixture)
            was  similar, although somewhat  higher,
            than that measured for pure HDDA. The
            slight increase  in the  HDDA permeation
                       rates from the mixtures relative to that for
                       pure HDDA could possibly result from the
                       presence of the more  rapjdly permeating
                       EHA carrier solvent. In comparison, the
                       EHA permeation rate from the 25% HDDA/
                       75% EHA mixture was much higher than.
                       that for  EHA  permeating  from the 50%
                       HDDA/50% EHA mixture.  The EHA  per-
                       meation  rate is strongly dependent on its
                       concentration in the mixture; however, we
                       did not perform experiments with pure EHA
                       so  that quantitative comparisons are not
                       possible.

                       Conclusions and
                       Recommendations
                        The permeation  of multifunctional aery-
                       late compounds and mixtures can be mea-
                       sured successfully using the ASTM F739
                       permeation  method employing a silicone
                       rubber collection medium. The silicone rub-
                       ber sheeting was suitable as a collection
                       medium  for  TMPTA, HDDA,  and EHA. In
                       general,  the collection  capacity and  effi-
                       ciency were good; however, in the perme-
                       ation tests with HDDA and EHA mixtures,
                      the absorbance for the HDDA was low.
                       Use  of  the permeation  method with
                      permeants that swell or pucker the protec-
                      tive clothing material being tested  needs
                      further investigation.
                        The butyl  rubber and nitrile rubber ma-
                      terials at the material thicknesses tested
                      were more  effective barriers to perme-
                      ation by the multifunctional acrylate com-
                      pounds than was natural rubber under the
                      conditions and sensitivity  of the test
Table 4. Summary of Permeation Test Results*

                                                 Temperature = 2CPC
 Chemical/Mixture                   Butyl rubber                    ,     Natural rubber
                                                                                                  Nitrile rubber
TMPTA


HDDA



50% HDDA/50% EHA




25% HDDA/75% EHA
No permeation detected
No permeation detected
No permeation detected
                              No permeation detected
Permeation detected at 360-48O min
(only 1of3 replicates)

Permeation detected at 30-60 to
60-120 min;
Steady-state rate: 0.92 ^g/cnf-mm

Permeation detected at 30-60 min;
Steady-state rates:
  HDDA: 1.02ng/cml-min
  EHA: 11.7 i3.g/cm*-min

Permeation detected at
15-30 to 30-60 min;
Steady-state rates:
  HDDA: 1.35 \igfcnf-min
  EHA: 20.0 \Lgfcm2-min
                                                                No permeation detected
                                                                No permeation detected
                                                                No permeation detected
                                                                                              No permeation detected
* Detection limits (per sampling interval): TMPTA:  0.36 pa/cm2
                                  HDDA:   0.1 lug/err?
                                  EHA:     0.099 \ig/cmz

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                                                 0.045
                                                                     0.050
Tabto 5. Results for Permeation of TMPTA and HDDA through Natural Rubber

                            Temperature = 20°C
                                               TMPTA               HDDA

Thickness (cm)
Cumulative Permeation
    Time (min)

        0
        15
        30
        60
       120
       180
       240
       360
       480
     Rinse
Breakthrough detection time (min)
Steady-state permeation rate
fog/cm '-min)1

Absorbance (%)*
    nd
    nd
    nd
     0.51*

    nd
360-480, >480,
    >480

   N/A
                                               100.0
  nd'
   nd
   nd
    0.18*
    3.9
   23.0
   57.2
  147.2
  257.5

   33.4
30-60, 30-60,
  60-120

    0.92
                                                                    87.6
                                            method. Comparison of these results with
                                            those reported by other researchers shows
                                            that the multifunctional  acrylates perme-
                                            ate the glove materials (in this case natu-
                                            ral rubber) at much lower rates than those
                                            measured for simple acrylate compounds.
                                              The full report was submitted in fulfill-
                                            ment of Contract  No. 68-C9-0037, Work
                                            Assignment 0-10,  by Arthur D. Little, Inc.,
                                            under sponsorship  of the U.S. Environ-
                                            mental Protection  Agency.
* Values reported are averages of 3 replicates. (-) indicates samples were not
  analyzed, (nd) Indicates that no permeant was detected in the collection medium
  extract for that sampling interval. Detection limits: TMPTA, 0.36 iig/cm2;
  HDDA, 0.11 \ig/cm*.
* Permeant detected in 2 of the 3 replicates: 0.15 \s.g/cnf,0.21 ng/cm2, nd.
* Permeant detected in only 1 of the 3 replicates: 0.51 ^.g/crtf,  nd, nd.
i Values reported are averages of 3 replicates. (N/A) indicates  not applicable.

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 Table 6. Permeation Test Results for HDDA and EHA Mixtures through Natural Rubber

                                                            Temperature =2CPC

                                      50% HDDA/50% EHA
                                                                                  25% HDDAJ75% EHA
                                  HDDA
                                                        EHA
                                                                              HDDA
                                                                                                     EHA
 Thickness (cm)
 Cumulative Permeation fag/cm2)*:
       Time (mm)
0.050
                                              0.048
0
15
30
60
120
180
240
360
480
Rinse
Breakthrough detection time (mm)
Steady-state permeation rate
fag/cnf-min) *
Absorbance (%)*
nd'
nd
nd
2.6
36.2
97.0
153.9
275.9
405.8
605.0
30-60
1.02
40.1
nd
nd
nd
19.0
492.1
1254.6
1994.6
3411.3
4697.9
706.2
30-60
11,7
86.9
nd
nd
. 0.14 *
2.6
26.1
54.8
90.2
196..1
357.8
415.6
15-30, 30-60, 30-60
1.35
46.3
nd
nd
6.28* . . .
88.5
1129.4
2335.6
3525.3
5689.7
8331.3
1235.2
15-30,15-30,30-60
20.0
87.1
   Values reported are averages of 3 replicates, (nd) indicates no permeantwas detected in the collection medium extract for that
   sampling interval. Detection limits: HDDA, 0.11 pg/cm2; EHA, 0.099 ng/cm*.
  HDDA: Permeant detected in 1 of 3 replicates: 0.14 v.g/crrf, nd, nd; EHA: Permeant detected in 2 of 3 replicates-
  0.72 \ng/cm2, 0.55 us/cm* nd.
  Values reported are averages of 3 replicates.
                          10000
                                    O  EHA   (25% HDD A/75% EHA)
                                        HDDA (25% HDDA/75% EHA)
                                     0  EHA   (50% HDDA/50% EHA)
                                        HDDA (50% HDDA/50% EHA)
                                        HDDA (100%)
                                             100
                                                           200           300
                                                              Time (minutes)
                                            400
                                                           500
Figure 2. Permeation of HDDA and EHA from mixtures through natural rubber glove material (Average of 3 replicates, error baris± standard deviation.)
                                                                    irU.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40251

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   FL GoydanandT. Stolkiare with Arthur D. Little, Inc., Cambridge, MA 02140-2390.
   Esperanza P. Renard is the EPA Project Officer (see below).
   The complete report, entitled "Permeation ofMultifunctionalAcrylates through Three
     Protective  Clothing Materials," (Order  No.  PB92-164 797/AS; Cost: $26.00,
     subject to change) wilt 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:
           Risk Reduction Engineering Laboratory
           U.S. Environmental Protection Agency
           Edison, NJ 08837-3679
United States
Environmental Protection
Agency
Center for Environmental
Research Information  "
Cincinnati, OH 45268
     BULK RATE
POSTAGE & FEES PAID
         EPA
   PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/SR-92/049

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