t
                                     united states
                                     Environmental Protection
                                     Agency
                                 Environmental Sciences Research--
                                 Laboratory
                                 Research Triangle Park NC 27711
Research and Development
EPA-600/S2-81-106 Oct 1981
                                     Project Summary
                                     Potential  Atmospheric
                                     Carcinogens:  Phases  2/3.
                                     Analytical  Technique  and
                                     Field  Evaluation
                                     D. S. West, F. N. Hodgson, J. J. Brooks, D. G. DeAngelis, A. G. Desai, and
                                     C. R. McMillin
                                       A sampling system was developed
                                     to collect 20 significant probable or
                                     possible atmospheric carcinogens
                                     from ambient air. The sampling system
                                     was designed using a combination of
                                     solid sorbent materials consisting of
                                     Tenax-GC, Porapak R, and Ambersorb
                                     XE-340, arranged in series. Air samples
                                     were drawn through this system using
                                     a Nutech Model 221-1A pump.
                                       The system was evaluated in sam-
                                     pling trips to Los Angeles, California;
                                     Niagara Falls, New York; and Houston,
                                     Texas. Analysis of the samples for the
                                     20 selected compounds, as well as
                                     additional broad-scan organic data,
                                     was  accomplished  using  thermal
                                     desorption of the sorbent  materials
                                     followed by capillary column  gas
                                     chromatography/mass spectrometry
                                     (GC/MS). A sample collected in
                                     Houston was.also analyzed using a
                                     multi-detector capillary column  GC
                                     system  having a conventional flame
                                     ionization detector,  a nitrogenphos-
                                     phorus selective flame ionization
                                     detector,  photoionization  detector,
                                     and an  electron capture detector. A
                                     comparison of  GC/MS  and  multi-
                                     detector GC results was made.
                                       This Project Summary was devel-
                                     oped by EPA's Environmental Sciences
                                     Research  Laboratory, Research  Tri-
                                     angle Park, NC, 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
                                   The general population, particularly
                                 in urban areas, is exposed to a wide
                                 variety of  atmospheric  pollutants.
                                 Currently, the health hazard posed by
                                 this situation cannot be adequately
                                 defined because of the complexity of the
                                 problem and the lack of sufficient,
                                 reliable data. To accurately assess this
                                 exposure problem, a reliable screening
                                 technique is needed to determine what
                                 substances, at what concentrations, are
                                 present in our ambient atmosphere.
                                   The ability to assess the extent of the
                                 potential health hazard in ambient air
                                 requires at least three things:
                                   (1) Knowledge of the materials that
                                      pose the hazard,
                                   (2) A reliable sampling technique for
                                      collecting these materials, and
                                   (3) Adequate technology for accurate
                                      analyses of these materials.
                                   These three requirements provided
                                 direction for this research program. The
                                 objective of this program was to develop
                                 sampling and analytical techniques for
                                 20 of the most significant, potentially
                                 carcinogenic, atmospheric pollutants
                                 and to demonstrate these techniques
                                 with field tests in selected urban areas.
                                   To fulfill this objective, the program
                                 was divided into three phases that

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roughly paralleled the three years of the
contract. Phase 1  included a background
study, during which time atmospheric
pollutants were prioritized,  and 20
compounds were selected to be moni-
tored.  In  addition, a review of  the
carcinogen  cofactor  literature was
conducted, and isopleths for potential
sampling sites were generated using
the Monsanto Research Corporation
(MRC) Source Assessment Data Base
and the EPA Climatological Dispersion
Model. Results from these first three
activities of Phase  1 have been previ-
ously reported (1).
  Phase  2 of the program dealt with
selection and  laboratory testing of  a
broad-range sampling system, based on
commercially available sorbent materials
and the associated methodology needed
to complete sample  analyses. This
phase  had  much in common with  a
companion program (EPA contract 68-
02-2774) aimed at developing a portable
collection system  for carcinogens in
ambient air.  The  related  contract
included research on the selection and
evaluation of candidate sorbent mate-
rials, and development of the rationale
for  selecting  the final combination of
materials to use  in  a portable sampling
system. Capillary gas chromatography/
mass spectrometry (GC/MS) techniques
were evaluated for use as the "analytical
finish" to the sampling system.
  The final phase of the program (Phase
3) involved field  evaluation of  the
system in actual  sampling applications.
Samples were collected in Los Angeles,
Niagara Falls, and  Houston using the
sampling system developed during this
program.
  An additional study  evaluating  a
multi-detector capillary GC system for
the analysis of the samples  was con-
ducted in conjunction with the Houston
sampling trip. This study was the first
attempt to evaluate the  possibility of
using GC with  various  selective  and
nonselective detectors as an alternative
to GC/MS for the analysis of complex
environmental samples.


Summary
  The 20 compounds selected for this
study  were  acrolein,  acrylonitrile,
benzene, benzidine, benzo(a)pyrene,
benzyl  chloride,  carbon  tetrachloride,
chrysene, 1,2-dichloropropene, di-(2-
ethylhexyl)  phthalate,  1,4-dioxane,
ethylene dibromide, ethylenedichloride,
ethylene oxide,  hexachloro-1,3-buta-
diene, pentachlorophenol, styrene.
tetrachloroethylene, toluene-2,4-dia-
mine, and vinyl acetate.
  A few general problems were asso-
ciated with the 20 selected compounds.
For example, highly volatile compounds
could not be quantitatively retained on
solid sorbents if the sampling volume
was  very high, and nonvolatile com-
pounds, such as benzo(a)pyrene, which
exist in the atmosphere at concentra-
tions  lower  than volatile compounds,
generally could not be detected analyt-
ically  without  very high sampling
volumes. Also,  reactive compounds,
such  as  styrene and  ethylene oxide,
which  tend  to   polymerize on active
surfaces, were more effectively retained
on sorbents that had relatively more
active surfaces. These conflicts indicated
areas where compromises were required
to develop a  single  sampling system.
  Six commercially available  sorbent
materials (Tenax-GC, Porapak N,
Chromosorb  104, Ambersorb XE-340,
SKC, Inc., and activated charcoal) were
evaluated as candidates for the collection
media in this   study.  The sorbent
properties of these materials  were
evaluated using  elution profile  tech-
niques in a  laboratory study. This
involved a matrix of 18 test compounds
representing a wide variety of polarities,
volatilities, and  functionalities. Based
on this study,  and on  other known
sorbent properties (e.g., upper tempera-
ture limit  and thermal background), the
following  materials  were selected for
use in the sampling system:

  Tenax GC - The only high temperature
  (350°C) adsorbent available  that
  allows  the  quantitative thermal de-
  sorption of organic compounds with
  low volatility.

  Porapak  R -  One  of the  highest
  capacity polymeric adsorbents, with a
  reasonable background level (better
  than Porapak N) and a  range of utility
  overlapping with Tenax-GC.

  Ambersorb XE-340 - The adsorbent
  anticipated to have the least difficulty
  with desorption  of compounds of
  intermediate volatility. Also, Amber-
  sorb XE-340  is  expected  to have
  fewer detrimental effects from water
  and less reactivity with collected sam-
  ples than is charcoal. Ambersorb XE-
  340's  range   of  utility  leaves  the
  smallest gap between  polymeric and
  carbonaceous adsorbents for the
  types of compounds collected.
                                                                                                                  1
These  three sorbent  materials were
placed  in separate glass tubes in series
to complete the sampling system.
  Analyses of collected samples involved
thermal desorption of the sorbent tubes,
followed  by cryogenic reconcentration
in a capillary trap.  The trap was
subsequently  heated to  introduce the
sample, in the form of a compact "plug",
into  a  capillary gas chromatograph/
mass spectrometer  system.  This was
accomplished using either a specially
fabricated inlet system or a commercially
available Nutech  Model 320 thermal
desorption system.
  The  following summarizes the pre-
ferred  analytical techniques used for
this project:

  Instrument:  Hewlett-Packard  Model
  5985B  GC/MS.  Column: Methyl
  silicone (OV101, SE-30, SP2100 or
  equivalent) capillary (fused silica or
  glass),  50 m, 0.2-0.25 mm  i.d. for
  inner diameter.

  Temperature Program: Subambient (-
  30°C) during tube desorption. Rapid
  rise  (~30°C/min)  to 0°C.  More
  gradual temperature rise(~8°C/min)
  to  ~30° below  upper  temperature^
  limit of column.                    \

  Inlet System: Nutech Model 320
  thermal desorption system, capillary
  direct coupling.

  Mass Spectrometer:  Scan mode.

  As previously mentioned, field tests in
Los Angeles, Niagara Falls, and Houston
were conducted. Only four of the target
compounds (benzene, tetrachloroeth-
ylene, benzyl  chloride,  and  carbon
tetrachloride) were  observed in any  of
the  field samples. Concentrations
ranged from 0.1 to 8 /ug/m3. Numerous
additional compounds were observed
and identified by mass spectrometry.
  The system functioned as anticipated,
demonstrating the need,  in  certain
instances, for additional  collection
capacity beyond a single Tenax collector.
However, the  degree  of breakthrough
into  the subsequent  Porapak  R  and
Ambersorb XE-340 tubes varied greatly
with the  sampling environment. In the
Los Angeles samples, substantial "pre-
fractionation" was  obtained,  with
significant amounts of pollutants  in
varying ranges collected on each of the
three sorbents. In the Houston samples,
compounds were observed only on the j
Tenax and Porapak tubes. In contrast toJ

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t
the Los Angeles and Houston samples,
the Niagara Falls samples were collected
in  an indoor  environment. In this
environment, no sample breakthrough
occurred from  the Tenax tube to the
Porapak and Ambersorb sorbents.
  Although all  of the factors  involved
have not been fully defined, it is clear
that sampling volume  is not the only
factor determining selection of proper
sampling materials. Climatic conditions
such as temperature and humidity, as
well as sample composition, are doubt-
lessly factors as well. For very  low
sample volumes, breakthrough from
one sampling material to the next would
not  be expected. The  continually in-
creasing need for lower detection limits,
however, requires that a large volume of
air  be sampled to  assure sufficient
material  for  analyses.  Data obtained
during the Niagara Falls sampling show
that, even with a large volume, Tenax
may retain all the organic constituents
under certain conditions. The sample
volume taken  at Niagara Falls  was
greater than that taken during Houston
sampling and nearly as great as that
taken at Los Angeles. Moreover, loading
of specific compounds of interest was
greater than found at the other locations.
  Compound retention on Tenax sorbent
may be affected by factors other than
those  mentioned. The evaluation of
these factors  are beyond the scope of
this program.  These may include selec-
tive displacement effects by other
matrix compounds; interaction with
water whereby an immiscible compound
pair, having a combined vapor pressure
higher than that of either compound (as
in steam distillation),  is formed; and
change in the surface characteristics of
the  Tenax due to atmospheric constitu-
ents such as ozone or NOX.
  A multi-detector capillary gas chro-
matographic [MD(GC) ] system devel-
oped at MRC was used to analyze one of
the  samples collected in Houston. In this
system, the effluent from the capillary
chromatographic column is split between
four detectors:  a conventional flame
ionization detector (FID), a nitrogen-
phosphorus selective flame ionization
detector (N-PFID), an electron capture
detector (BCD),  and a photoionization
detector (PID).
  The principle behind the use of such a
system depends upon  the  detectors'
degree of selectivity. When  operated
simultaneously during an analysis, the
ratioing of different detector responses
for  compounds  "seen" by more than
one detector is permitted. When used in
conjunction  with  GC retention times,
detector response  ratios provide  an
additional parameter that greatly im-
proves  the  confidence  of compound
specificity from a  GC analysis. The
objective of this work was to conduct a
preliminary  investigation of multiple
selective detection and  detector  re-
sponse  ratioing as  an alternative
technique to mass spectrometry for the
detection of the compounds of interest.
  Results of the MD(GC)2 analyses of
the Houston field samples indicated the
presence of  benzene in the Tenax and
Porapak R tubes, as also observed by
capillary GC/MS. Tetrachloroethylene,
determined  by (GC)2/MS to also  be
present in  the Tenax and Porapak R
tubes, was not indicated by the MD(GC)2
analyses. Conversely, carbon tetra-
chloride, acrylonitrile, vinyl acetate,
1,4-dioxane, and ethylene dibromide
were tentatively identified in the field
samples by MD(GC)2.
  The detectors of the MD(GC)2 system
are  more sensitive than the mass
spectrometer detector, so some of these
tentative identifications might be correct,
yet fall below the detection level of the
mass spectrometer. Alternately, some
of the  discrepancies in compound
indentification  might be  due  to a
combination  of the  limitations for
MD(GC)2 analyses,  including shifts in
retention times due  to matrix effects.
  Results indicated that although
MD(GC)2 is  much more selective and
specific than  (GC)2 or GC,  it  cannot
replace GC/MS for the  unequivocal
identification of compounds. MD(GC)2
can  be  used to  indicate  the possible
presence of selected  compounds,  al-
though  matrix effects and other limita-
tions can imply the presence of  com-
pounds not actually present, or the
absence of compounds that are present.
Perhaps a better use for MD(GC)2willbe
to identify various types of compounds
in samples  and  compile  their  "total"
amounts. This would  provide much
more information than a total chroma-
tographable organics analysis (TCO)
about the composition of an air sample,
and  could perhaps  be an indicator of
overall air quality in terms of organic
pollutants.


Conclusions
  The sampling  system  operated  as
anticipated  in  field  sampling applica-
tions. The need for additional, comple-
mentary sorbent capabilities to those of
Tenax  was demonstrated  in  the  Los
Angeles and Houston samples, where
significant amounts of  organics were
observed on the subsequent (Porapak
and Ambersorb) tubes.  A partial frac-
tionation was  also observed on  the
various sorbent materials where differ-
ent ranges of  compounds (based  pri-
marily  on volatility) were found. There
appeared to be some influence exerted
by matrix and/or humidity effects on the
amount of breakthrough observed  on
the latter  sorbents. Niagara  Falls
samples were  collected in an interior
environment and exhibited little, if any,
compound breakthrough to the Porapak
and Ambersorb materials.
  The number  of compounds from the
target  list of 20 probable  or  possible
carcinogens  observed in  actual field
samples was small. The largest number
and highest concentrations  of these
targeted compounds were observed in
the Niagara Falls samples.
  The  analytical methodology was
based  primarily on capillary column
GC/MS,  using  thermal desorption to
recover the sample from the sorbents
for analysis. Samples collected in high
humidity environments  (e.g.,  Houston)
caused particular problems during
analysis due to high concentrations of
water  collected  on  the Porapak and
Ambersorb sorbents. However, it was
found that by changing certain analytical
parameters (e.g., initial GC temperature),
a  satisfactory  analysis  could  be  per-
formed in these instances.
  One  sample  set from Houston  was
also analyzed  using a  multidetector
capillary GC technique. Results showed
that the multidetector approach offered
advantages over conventional GC in
terms  of selectivity and  specificity...
However, it cannot replace  GC/MS for
unequivocal identification of compounds.
This approach  might be applied more
appropriately to  assessment  of  com-
pound types as a more general indicator
of overall air quality.


Recommendations
  The following recommendations  are
made  as the  result  of the  research
conducted during this program:
  (1) The sampling system developed
     during this project  should  be
     extensively evaluated  in other
     field sampling situations to further
     define its operational capabilities.
  (2) The sampling technique employed
     should be used primarily as a
     "screen" for  the  presence/

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         absence of specific compounds or
         for wide-scan evaluation of organic
         composition in ambient air, much
         as the EPA Priority Pollutant
         Protocol is used as a "screen" for
         organics in industrial effluents.
      (3) Only after the  system has been
         validated for a specific compound(s)
         in a particular air matrix should it
         be used to generate quantitative
         data.
      (4) Validation should use spikes tode-
         termine actual  recoveries of the
         compounds of interest. Stable,iso-
         topically-labeled compounds
         should be used whenever possible
         to allow differentiation  between
         the spike and the native compound.
      (5) When a compound of concern is
         identified through the screening
         process, confirming studies should
         be made  to  determine if the
         compound is real, or is an artifact
         of the sampling/analytical tech-
         niques.
      (6) The multi-detector GC approach
         should be further evaluated  to
         determine its value. This would
         include development of computer-
         assisted data reduction techniques
         to combine the vast amounts of
         information and  to compare  re-
         sponses from the various detectors.
           D. S. West, F. N. Hodgson. J. J. Brooks, D. G. DeAngelis, A. G. Desai, and C. R.
             McMillin are with Monsanto Research Corporation, Dayton, OH 45407.
           James Mulik is the EPA Project Officer (see below).
           The complete report, entitled "PotentialAtmospheric Carcinogens: Phases 2/3.
             Analytical Technique and Field Evaluation," (Order No. PB 82-102476; Cost:
             $20.00, 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:
                   Environmental Sciences Research Laboratory
                   U.S. Environmental Protect ion Agency
                   Research Triangle Park, NC 27711
                                                                                      1
                                              US GOVERNMENT PRINTING OFFICE; 1981 — 559-017/7413
    References
    1. McMillin, C. R., L B. Mote, and D. G.
       DeAngelis.  Potential Atmospheric
       Carcinogens, Phase 1: Identification
       and  Classification. EPA-600/2-80-
       015, U.S. Environmental Protection
       Agency, Research Triangle Park, NC,
       January  1980. 253 pp.
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300

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