United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-94/187 November 1994
EPA Project Summary
Ambient Measurement
Methods and Properties of the
189 Clean Air Act Hazardous Air
Pollutants
Thomas J. Kelly, R. Mukund, Sydney M. Gordon, and Melinda J. Hays
The state of development of ambient
measurement methods for the 189 Haz-
ardous Air Pollutants (HAPs) in Title III
of the 1990 Clean Air Act Amendments
(CAAAs) was surveyed. Measurement
methods for the HAPs were identified by
reviews of established methods and by
literature searches for novel research
techniques. Methods were segregated
by their degree of development into
Applicable, Likely, and Potential meth-
ods. This survey identified a total of
171 methods, applicable to one or more
HAPs, at varying degrees of method
development. As a basis for classify-
ing the HAPs and evaluating the appli-
cability of measurement methods, a
survey of chemical and physical prop-
erties of the HAPs was also conducted.
The properties compiled include vapor
pressure, boiling point, water solubil-
ity, polarizability, aqueous reactivity,
and atmospheric reactivity. The results
of both the methods and properties sur-
veys were tabulated for each of the 189
HAPs.
The full report was submitted in par-
tial fulfillment of Contract No. 68-DO-
0007 by Battelle under the sponsor-
ship of the U.S. Environmental Protec-
tion Agency (EPA). This report summa-
rizes the results obtained under work
assignment 44 and covers a period from
March 1993 through March 1994. The
work was completed as of March 1994.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory, Re-
search Triangle 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 CAAAs accelerated the pace of
regulating toxic air pollutants by establish-
ing a list of 189 HAPs. The HAPs are a
remarkably diverse group of compounds,
including metals, pesticides, chlorinated
and hydrocarbon solvents, industrial
chemicals and intermediates, combustion
by-products, complex chemical mixtures,
and chemical groups such as polychlori-
nated biphenyls. Some of the HAPs are
volatile organic compounds commonly
measured as air pollutants. Many other
HAPs are widely recognized as toxic but
have previously only been addressed in
workplace environments. A few HAPs are
not likely to exist under atmospheric con-
ditions because of their reactivity.
To meet the CAAA goals of defining
and reducing human health risks from
HAPs, ambient measurements are needed.
However, ambient measurement methods
for the HAPs are generally lacking. The
present study was conducted to identify
existing and potential ambient measure-
ment methods for HAPs. This study dif-
fered from previous such surveys in that
physical and chemical properties of the
HAPs were compiled and used as the
basis for evaluating the applicability of
measurement methods. This survey also
identified novel research methods, rather
than relying solely on published compila-
tions of standard methods. Finally, this
Printed on Recycled Paper
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survey categorized the HAPs measure-
ment methods by their state of develop-
ment, distinguishing workplace or labora-
tory methods from methods actually tested
In ambient air.
Objectives
The primary objective of this study was
to identify and categorize measurement
methods for the 189 HAPs in ambient air.
The secondary objective was to compile
chemical and physical property data for
the HAPs as the basis for evaluating meth-
ods.
Results and Discussion
The chemical and physical properties of
the HAPs were first compiled to serve as
the basis for identifying measurement
methods. The 189 HAPs were first sepa-
rated into 166 organic and 23 inorganic
chemicals. Each group was then further
divided into four categories based on va-
por pressure, i.e., nonvolatile compounds,
semivolatile compounds, volatile com-
pounds, and very volatile compounds.
Properties of the HAPs in each volatility
class were compiled from recent hand-
books and data bases and were tabulated
for the entire HAPs list. The properties
compiled were vapor pressure, boiling
point, water solubility, polarizability, and
reactivity in the aqueous phase and in the
atmosphere.
The survey of measurement methods
included a review of standard methods,
such as EPA Screening Methods, Con-
tract Laboratory Program methods, and
Compendium methods. Methods published
by the National Institute for Occupational
Safety and Health, Occupational Safety
and Health Administration, American So-
ciety for Testing Materials, and other or-
ganizations were also reviewed. Recent
surveys of ambient concentration data and
atmospheric transformations of the HAPs
were also useful. Literature searches were
also made of journals, meeting proceed-
ings, and reports to identify additional in-
formation on measurement methods. The
identified methods were assigned to one
of three categories, depending on the state
of development of the method relative to
ambient measurements: 1) Applicable
methods, established and documented to
a reasonable degree for the target HAP in
ambient air; 2) Likely methods, established
for the target HAP or a closely similar
HAP in workplace air, but not in ambient
air, or needing further testing before des-
ignation as an Applicable method; and 3)
Potential methods, needing extensive fur-
ther development for adaptation to ambi-
ent air measurements. The chemical and
physical properties of the HAPs were used
in identifying Likely and Potential meth-
ods.
The product of the HAPs methods sur-
vey is an 18-page table, accompanied by
a reference list of 171 separate methods
identified for various HAPs. Sixty-seven of
those methods are novel research meth-
ods found in the scientific literature. The
methods table lists the 189 HAPs in the
same order as in the CAAA and shows
the chemical name, Chemical Abstracts
Number, volatility category, identified meth-
ods, limits of detection, and comments on
the methods, for each HAP. The identified
methods are listed as Applicable, Likely,
or Potential, to indicate the state of ambi-
ent method development for each HAP.
The detection limit is given for at least the
most developed methods for each HAP.
The comments for each HAP point out
existing problems with the identified meth-
ods or indicate the basis for the assign-
ment of Applicable, Likely, or Potential
status.
The products of the survey of chemical
and physical properties are two tables,
one of the properties of the entire list of
189 HAPs and the second showing addi-
tional properties for the volatile and very
volatile HAPs. Also included in the report
is a discussion of the importance of water
solubility and polarizability as defining
characteristics of polar volatile com-
pounds.
This survey identified Applicable meth-
ods for 126 of the HAPs. Applicable meth-
ods were found for 109 of the 166 organic
HAPs and for 17 of the 23 inorganic HAPs.
For many of these HAPs, alternative meth-
ods were also found and were designated
as Likely methods. For 53 other HAPs,
Likely methods, but no Applicable meth-
ods, were found. For 6 HAPs, only Poten-
tial methods could be identified, and for 4
HAPs no measurement methods could be
identified at any stage of development.
These latter 10 HAPs are relatively un-
usual compounds, not normally regarded
as air pollutants. No ambient concentra-
tion data exist for these 10 HAPs, and
virtually no information on their atmo-
spheric reactions and fate.
Conclusions and
Recommendations
The 123 HAPs with Applicable methods
and the 53 HAPs with Likely methods
suggest that for the great majority of the
HAPs ambient measurements should be
achievable with a reasonable further de-
velopment effort. However, caution is war-
ranted, because method development is
not necessarily complete even for the Ap-
plicable methods. For some HAPs, no
ambient measurements have been made
with the indicated Applicable methods, and
ambient sampling and analysis problems
may remain to be resolved for those meth-
ods. Continued development is needed
for many methods. A goal of that effort
should be to consolidate and simplify the
variety of methods identified into a smaller
number of well characterized and broadly
applicable methods. The 67 research
methods identified are particularly appro-
priate candidates for further evaluation,
because they have generally been ap-
plied only to a limited extent by a small
number of investigators.
In terms of method development needs,
the most cost-effective approach will prob-
ably be further development of the Likely
methods that exist for the 53 HAPs with
no Applicable methods. The definition of a
Likely method in this survey means that a
reasonable amount of further development
should result in a method applicable to
ambient air. Those 53 HAPs are primarily
volatile and semivolatile organic com-
pounds, which comprise the majority of
the HAPs list. As a result, further develop-
ment for those compounds would be es-
pecially valuable. The 10 HAPs for which
no methods or only Potential methods were
found would seem to comprise the great-
est gap in measurement capabilities for
the HAPs. Method development should
be conducted for these 10 HAPs, but this
effort should be prioritized based on their
emissions, likely reactivity, and potential
products in air. Linking method develop-
ment with other information will avoid
spending resources on HAPs that are too
reactive or emitted in quantities too small
to be of importance in the atmosphere.
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Thomas J. Kelly, R. Mukund, Sydney M. Gordon, and Melinda J. Hays are with
Battelle, Columbus, OH 43201.
William McClenny is the EPA Project Officer (see below).
The complete report, entitled "Ambient Measurement Methods and Properties of the
189 Clean Air Act Hazardous Air Pollutants," (Order No. PB95-123923; Cost:
$27.00, subject to change) will be available only from:
National Technical Information Service
5285 Pod Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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