United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-83-027 June 1983
v>EPA Project Summary
Volatile Organic Chemicals in the
Atmosphere: An Assessment of
Available Data
R. Brodzinsky and H. B. Singh
A significant body of information is
currently available to characterize the
burden of possibly-hazardous organic
chemicals (HOCs) in ambient environ-
ments. However, these data have not
been accessible in an organized for-
mat, and no attempt had been made to
study their significance or to integrate
them into a useful and cohesive docu-
ment. In this study, ambient data
covering 151 chemicals were sought
from 241 references primarily from the
years 1970 through 1980. The data
were collected and collated into a
computer-accessible data base. The
data were classified into four data-
quality categories-excellent, good, ac-
ceptable, and questionable. The data
were then analyzed to assess their
reliability and usefulness in concen-
tration trend analysis. Significant gaps
were found in the available data. For
any specific HOC, relatively little data
are available with which health assess-
ments or trend analysis can be made.
Data acquisition has been limited pri-
marily to a few geographical regions,
and most sampling programs have
been performed in the warmer months
and during daylight hours.
Specific recommendations are made
for future studies regarding data re-
porting. A strategy for an effective
national monitoring program for HOCs
in the atmosphere is presented.
A computer-compatible data tape
listing all of the referenced atmospheric
data has been prepared. The data tape
contains information on each of the
132 chemicals for which data were
actually obtained.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search 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
information at back).
Introduction
Significant quantities of organic chem-
icals are released into the ambient en-
vironment as a necessary outcome of day-
to-day human activities. In recent years, it
has become evident that many of these
chemicals may be toxic at concentrations
significantly higher than those found in
the ambient atmosphere. The degree of
risk associated with current exposures is a
matter of active debate, and this effort
focuses upon the gaseous organic chem-
icals in the ambient environment, especial-
ly those which may be hazardous. The
term "hazardous organic chemicals" (HOCs)
used here is not intended to imply that a
proven human health hazard exists: in
most cases toxicity studies are incom-
plete and entail extrapolation of animal
data to humans.
This report attempts to integrate a
diverse body of information on ambient
concentrations of HOCs into a useful and
cohesive document describing the spe-
cies measured, the locations and times of
the measurements, the concentrations
which were observed, and the quality of
the reported measurements. The objec-
tives of the task were: (1) review, sum-
marize and critically evaluate available
(both published and unpublished) atmos-
pheric data on HOCs in the air environ-
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ment, (2) assess the extent, quality, relia-
bility and representativeness of these data,
(3) compile all "acceptable" data into a
master data file and subject these data to
comprehensive statistical analysis, and (4)
identify major gaps in available data and
recommend a research strategy for de-
velopment of a measurement program to
generate a national data base on HOCs in
the air.
Procedure
A list of compounds to be included in
the data base was developed, a literature
search was conducted, and the gathered
data were compiled into a computerized
data base. Table 1 presents a listing of the
151 chemicals chosen as target com-
pounds for this study. The chemicals were
grouped into categories for organizational
purposes in the study. The table also
identifies certain chemicals as bacterial
mutagens (BM) or suspected carcinogens
(SC). This information was obtained from
literature and studies which have evaluated
large bodies of available data. Information
about bacterial mutagenicity is based
largely on the "Ames Salmonella Micro-
some Assay." Mutagenic tests are direct
and simple, but the carcinogenicity in-
formation is based upon animal tests that
include consideration of epidemiology and
a critical and a comprehensive evaluation
of carcinogen, mutagen, and other toxi-
cological data. Evidence for the mutagen-
icity of toluene and the carcinogenicity ol
trichloroethylene is currently in some
dispute for lack of sufficient data..
Compounds concentrated indoors (e.g.,
in industrial environments) as well as
those concentrated in aquatic or soil en-
vironments (e.g., pesticides) or on aero-
sols were excluded from this study. In all,
more than 1 7,000 data points from 241
references were incorporated into the date
base.
All pertinent data were extracted frorr
the literature reports and put into a com-
Table 1. Target Hazardous Organic Chemicals in the Ambient Air
Category A
Category B
Category C
Category D
Name
Number
Name
Number
Name
Number
Name
Number
Benzene (SC) 001
Methyl chloride IBM) 002
Methyl bromide (BM/ 003
Methyl iodide (SC BM) 004
Methylene chloride (BM) 005
Chloroform (SCBM) 006
Carbon tetrachloride (SC) 007
1,2 Dichloroethane (SCBM) 008
1,2 Dibromoethane (SCBM) 009
1,1,1 Trichloroethane (BM) 010
1,1,2 Trichloroethane (SC) 011
1,1,2,2 Tetrach/oroethane (SCBM) 012
Hexach/oroethane (SC) 013
1,2 Dichloropropane (BM) 014
Vinyl chloride (SC BM) 015
Vinylidene chloride (SC BM) 016
(cis) 1,2 Dich/oroethylene (BM) 017
Trichloroethylene (SC BM) 018
Tetrachloroethy/ene (SC) 019
A/lyl chloride 020
Chloroprene (BM) 021
Hexachloro 1,3 butadiene (BM) 022
Monochlorobenzene (BM) 023
o-Dichlorobenzene (BM) 024
m-Dichlorobenzene (BM) 025
p-D/chlorobenzene (BM) 026
Tnchlorobenzene (BM) 027
Tetrachlorobenzene (BM) 028
o-Chlorotoluene (SC.BM) 029
Hexachlorocyclopentadiene (BM) 030
Ethylene oxide (BM) 031
Propylene oxide (SCBM) 032
Formaldehyde (SCBM) 033
Acetaldehyde 034
Phosgene 035
o-Cresol(SC) 036
p-Cresol(SC) 037
m-Cresol (SC) 038
Acrolein (SC) 039
bis- Chloromethyl ether (SC BM) 040
bis-12-Chloroethyl) ether (SC) 041
Acrylonitrt/e (SCBM) 042
Nitrobenzene 043
Dimethyl nitrosamine (SC) 044
Diethyl nitrosamine (SC) 045
2-Nitropropane (SC) 046
Key:
Category A Ubiquitous toxic chemicals in urban ambient environment; Category B: Ubiquitous suspect toxic chemicals in urban ambient environment
Category C: Toxic chemicals that are likely to be site specific and Category D: Chemicals considered to be nontoxic.
BM: Bacterial mutagens; SC: suspected carcinogens.
2
Toluene
o-Xylene
m/p-Xylene
Styrene (BM)
1,3 Butadiene (BM)
n-Dodecane (SC)
n-Decane (SC)
n-Undecane (SC)
n-Octadecane (SC)
o-Pinene (BM)
Dodecylbenzene (BM)
Fluorcarbon-22 (BM)
Ethyl chloride
1,1 Dichloroethane
1,1,1,2 Tetrachloroethane
1,4 Dichlorobutane
1,2 Dibromopropane
(trans) 1,2 dichloroethylene
Benzaldehyde
Tolualdehyde (isomers)
Phthalaldehyde (isomers)
Phenol
Peroxyacetyl nitrate
Peroxypropionyl nitrate
Peroxybenzoyl nitrate
Diethyl sulphate (SCBM)
Dimethyl sulphate (BM)
Carbonyl sulfide
Carbon disulfide
Tetramethyl lead
Tetraethyl lead
Trimethyl ethyl lead
Dimethyl diethyl lead
Methyl triethyl lead
101 Dibromomethane
102 Bromodichloromethane
103 Chlorodibromomethane
104 Dichlorodibromomethane
105 Bromoform
106 1-Chloro-2-bromoethane
107 Pentachloroethane
108 Bromopropane (isomers)
109 Chlorobromopropane (isomers)
110 1-Chtoro-3-bromopropane
111 Dibromochloropropane
112 1-Chloro-2,3-dibromopropane
113 1,1 Dibromo-2-chloropropane
114 Dichloropropene {isomers)
115 1-Chloro-3 bromopropene
116 Bromobenzene
117 Bromotoluene
118 Dichlorotoluene
119 Tnchlorotoluene
120 Tetrachlorobenzene
121 Tetrachlorotoluene
122 Pentachlorobenzene
123 Chloronitrobenzene
124 Dichloronitrobenzene
125 Chloroaniline
126 Ch/orobenzaldehyde
127 Epichlorohydrin
128 Maleic anhydride
129 1,4 Dioxane
130 Aniline
131 Benzonitrite
132 fi-Chloro ethers
133 Polychloronapthalenes
134 Ally! bromide
201 Methane 301
202 Ethane 302
203 Ethylene 303
204 Acetylene 304
205 Propane 305
206 Propene 306
207 i-Butane 307
208 n-Butane 308
209 Butenes (isomers) 309
210 i-Pentane 310
211 n-Pentane 311
212 i-Pentene 312
213 2-Methylpentane 313
214 3-Methylpentane 314
215 n-Hexane 315
216 2,4-Dimethyl pentane 316
217 Ethylbenzene 317
218 1,3,5 Tnmethylbenzene 318
219 1,2,4 Trimethy/benzene 319
220 1,2,3 Trimethylbenzene 320
221 Naphthalene 321
222 o-Methy/naphtha/ene 322
223 Carbon tetrafluoride 323
224 Fluorocarbon-12 324
225 Fluorocarbon-11 325
226 Fluorocarbon-113 326
227 Fluorocarbon-114 327
228 Acetone 328
229 Methylethyl ketone 329
230 Methyl isobutyl ketone 330
231 Acetophenone 331
232 Propiophenone 332
233 n-Heptane 333
234 n-Octane 334
n-Nonane 335
4-Ethyl toluene 336
Dimethyl sulfide 337
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Figure 1. Sampling locations reporting data on any of the 151 target chemi-chemicals in this
study. Sparse geographic coverage is obvious.
mon format for inclusion in the data base.
Each entry in the data base includes: the
bibliographic reference number; the lati-
tude, longitude, street address, city and
state of the sampling site; a site type code
(remote, urban, etc.); the reported con-
centration (in parts per trillion and micro-
grams per cubic meter); a code for the
units reported by the original investigator;
the percent relative standard deviation of
the reported values or of the measurement
technique; a quality code describing the
likely accuracy of the data; the number of
samples averaged together to produce the
data base line entry; codes for the sam-
pling and analytical methods; the time
average of the reported data; the maxi-
mum and minimum concentrations re-
ported (in ppt); the date and time at which
sampling began and ended, and the num-
ber of hours between sampling and anal-
ysis; the number of measurements below
the detection limit; the reported detection
limit; any comments necessary about the
data.
The compiled data were analyzed for
quality and quality codes were assigned
based upon comments of the original
researcher, the appropriateness of the
analytic techniques, known limits of the
techniques' accuracy and the magnitude
of the reported concentrations. Although
the assignment of quality codes was as
objective as possible, a considerable a-
mount of subjectivity was still needed in
assigning many of the quality codes. The
generalized characterization for the cate-
gories (excellent, good, acceptable, ques-
tionable) should not be construed as rigid,
for while an error of a factor of two may be
much too high for some compounds (e.g.,
benzene, methane), it may be acceptable
for others (e.g., chlorobenzene). In short,
the authors have integrated the available
published and unpublished information,
along with their own experiences, to arrive
at a means of characterizing the quality of
the available data.
Results
For each chemical the data are sum-
marized and tabulated to show the num-
ber of data points, the average quality, the
first quartile, the median,'and the third
quartile concentrations, for all of the data
and the data grouped by sampling site
classification (i.e., rural and remote, urban
and suburban, source dominated). Appen-
dices list minima, maxima, means and
standard deviations for each location re-
ported for each chemical. References are
also listed so readers may access the
original report for each location.
The full report also includes a brief
analysis of the results for selected chem-
icals: benzene, methylene chloride, chloro-
form, carbon tetrachloride, 1,2-dichloro-
ethane, 1,2-dibromoethane, 1,1,1-trichloro-
ethane, trichloroethylene, tetrachloroeth-
ylene, hexachloro-1,3-butadiene, acetalde-
hyde, cresols, bis-chloroalkyl ethers, di-
methyl nitrosamine, toluene, alpha-pinene,
fluorocarbon-22, benzaldehyde, PAN,
PBzN, and carbonyl sulfide. These chem-
icals are discussed for several reasons: the
data show an interesting pattern, interest
in the chemical is high, or some clarifica-
tion or comment on the data was necessary.
Attempts to use the data for trend
analysis showed that the data are too
sparse within this data set to permit such a
calculation. Even for one of the best data
sets, benzene, trend analysis was impos-
sible. No consistent sampling effort has
been reported, and a much more com-
plete, year-round data base must be as-
sembled before trend analysis can be
properly performed. The geographic spars-
ity of the data is illustrated in Figure 1, in
which every location included in the data
base has been marked with a star. Ob-
viously, sampling for HOCs has been con-
ducted in only a small portion of the
geographic area.
Results and Recommendations
Although this data base contains a large
quantity of data (more than 1 7,000 sep-
arate entries), it is only a beginning--a base
to build upon. Even for the chemicals of
greatest concern, relatively little data are
available with which to assess potential
risk or to develop control strategies.
Future studies should ensure the avail-
ability of "quality control" data, as well as
the measurement data. The format used
within the data base of this study could be
used as a guide. During assembly of this
data base, numerous omissions in data
reporting were noted. Measurements are
reported without any reference to error
limits. Detection limits, where needed, are
frequently not given, elapsed time be-
tween sample collection and analysis is
rarely given, sampling and analytic pro-
cedures used are not always clearly de-
fined. These data are essential to assessing
the integrity of the measurements. Mete-
orological data should also be included.
To assure the usefulness of collected
data, it should be available in a computer-
compatible form, especially when a large
volume of data is being reported. With the
large number of studies being performed
every day, this is the only way that the data
can be quickly brought together, assessed,
and analyzed
The data collected for this study are
primarily from the years 1970 through
1980. Every effort was made to compile
all the available data; however, the size of
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the task assures that data were missed.
The missing data may add to the quantity
of the data in the data base, but the general
conclusions of this study will likely stand--
more data are needed if valid human
health-risk assessments, trend analysis,
and models for control strategies are to be
made.
The comprehensive analysis of the data
base identified three specific shortcomings
in the current HOC data base: (1) Much of
the data available was collected to serve
different objectives and is largely unsuited
for the purposes of exposure characteriza-
tion. Indeed, many of the reported studies
are exploratory and qualitative in nature.
(2) In some cases, inadequately field
tested methods have been extensively
applied, resulting in the collection of a
body of data which is, at least in part, of
poor or unknown quality. (3) The data
coverage is extremely sparse and is often
random in nature. To overcome the ob-
served shortcomings, the authors recom-
mend a three-step approach: (1) generate
a data base mapping the spatial and tem-
poral atmospheric distribution of HOCs for
a preselected region, (2) characterize the
primary and secondary emission patterns
for the HOCs of interest within that region,
and (3) compare the experimentally ob-
served concentrations with predicted val-
ues based upon a modeling effort for the
selected region which relates emissions to
subsequent atmospheric concentrations.
The authors also offer suggestions for
carrying out the three-step strategy, speci-
fically for selection of target areas and the
siting strategy, the sampling strategy,
selection of target chemicals and the ana-
lytical measurement strategy, and the
quality assurance and quality control
strategy.
In summary, a large number of poten-
tially hazardous trace organic chemicals
have been identified in the ambient en-
vironment Available data are not sufficient
to describe the atmospheric distributions
of a majority of these chemicals. It is,
therefore, impossible to assess exposures
to these chemicals from past data. The
data currently available on HOCs in am-
bient air have been compiled and sum-
marized in a single document A plan to
overcome the gaps which now exists in
the data has been described.
R. Brodzinsky and H. B. Singh are with SRI International, Menlo Park. CA 94025.
Larry Cupitt is the EPA Project Officer (see below).
The complete report consists of paper copy and magnetic tape, entitled "Volatile
Organic Chemicals in the Atmosphere: An Assessment of Available Data,"
(Order No. PB 83-195 503; Cost: $19.00. subject to change)
subject to change)
Data Tape Associated with the Report, (Order No. PB 83-195 511; Cost:
$140.00, subject to change)
The above material is 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 Protection Agency
Research Triangle Park, NC 27711
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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