United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
Research and Development
EPA/600/S8-87/002 Jan. 1 988
&ER& Project Summary
Characteristics, Deposition and
Fate of Inhaled Paniculate
Matter
David Armentrout and Barbara Locke
Accurate estimates of deposition and
fate for particulate matter in the
respiratory tract are difficult to make
because of complexities in particle
composition and morphology. Several
deficiencies in information further
complicate the ability to make accurate
estimates. Available models for making
estimates range from simple models
based on assumed particle size distri-
bution to more complex models based
on a variety of parameters. Most work
in the area of estimating particle fate
following inhalation has been done on
aerosols of known composition. Addi-
tional work is needed to categorize
properties of inhalable particles with
respect to compositon in addition to
morphology. Additional research is
needed to define the effects of pulmo-
nary disease on particle clearance from
the lung. Additional research also is
needed to better explain the mechanics
of clearance from the pulmonary region
of the lung.
This Project Summary was devel-
oped by EPA's Office of Health and
Environmental Assessment, Washing-
ton. DC, to announce key findings of
the research project that is fully doc-
umented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Site- and/or situation-specific expo-
sure assessments often require incorpo-
ration of new procedures and new
information. One area where additional
information is needed is that of exposure
assessments dealing with the fate of
inhaled particulate matter. The purpose
of this report is to present information
available for use in estimating the
fractions of inhaled particles that are
absorbed by the lung and for estimating
the fate of these particles following
absorption.
The final project report, summarized
herein, includes the following specific
areas of investigation:
• Summary of current information on
types and characteristics of inhalable
particulate matter. The final report
defines the commonly used terms for
classes of particulate matter, and also
summarizes size and chemical com-
position of particulate matter from the
most common broad categories of
combustion and process emissions
sources.
• Summary of information that may be
useful in describing current tech-
niques for estimating absorption of
particulate matter. The final report
summarizes current information on
deposition and clearance of particles
developed from a survey of studies
identified through a literature search.
• Determination of the influence of
various physical parameters on
regional distribution and retention of
particles within the respiratory tract.
Summary of information on breathing
patterns, age, effects of pulmonary
disease, and the general influence of
physical and chemical particle char-
acteristics relative to depositon of
particulate matter.
• Description of lung damage caused by
particulate matter and the relation-
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ship of the damage to altered retention
characteristics. A discussion of the
type of information available is
presented.
• Provision of information on the dis-
tribution of paniculate matter to target
organs of the body following lung
absorption or absorption through the
gastrointestinal tract following elim-
ination from the lung. A discussion of
the problems associated with the
pollutant-specific nature of the avail-
able information is included.
An extensive literature search was
conducted to determine the availability
of data in each subject area and the
applicability of the data to improving
current risk estimating techniques. The
literature search produced a list of 405
references, the most pertinent of which
are included in the final report.
Similarly, a large volume of informa-
tion is available for use to improve the
current method of estimating the fate of
inhaled particulate matter; unfortu-
nately, this information is not in sum-
mary forms that can be readily applied.
Additional work is needed to develop
adequate particulate matter classifica-
tions and data summaries. Because of
the volumes of data involved, the devel-
opment of useful summaries would
require an effort beyond the scope of the
present effort.
Discussion
Existing models can predict particle
deposition and retention in the respira-
tory tract. These models are based
primarily on the behavior of particle
classifications according to size and
solubility. Literature searches identified
several of those models which show
reasonable correlation with predicted
results.
More is known about deposition and
clearance mechanisms in the extratho-
racic and tracheobronchial region than
in the pulmonary region. More studies
are needed to provide better definition
of the mechanics of macrophage clear-
ance from the pulmonary region as well
as the mechanics of clearance through
the lymph system. This research is
critical to providing accurate estimates
of total dose, including dose to target
organs resulting from absorption of
inhaled particles.
Summaries of gross classifications of
particles based on size distribution and
solubility characteristics are included in
the final report. These summaries were
taken primarily from two sources pub-
lished in 1982 and in 1967. Expanded
summaries more adequately character-
izing common aerosols are probably now
available, and a new literature search
may reveal better data regarding aerosol
composition and physical and chemical
characteristics. Existing industry-
specific studies provide more in-depth
characterization of emissions from
industrial processes. Compound-specific
aerosol data may provide a better basis
for estimating probable particle size
distribution in cases where the particle
size distribution is not known.
Studies have shown the importance of
age, breathing patterns, physical and
chemical properties of particles, and
pulmonary disease on particle deposi-
tion. Relatively few studies have been
performed, however, regarding the
effects of age and pulmonary disease,
and significantly more research is
needed in those two areas. With respect
to physical and chemical properties, a
number of studies have been conducted
concerning the influence of electrostatic
charge, particle morphology, hygroscopic
properties, surface coating, and toxicity
on absorption. For example, numerous
studies have attempted to characterize
the effects of inhalation of various
sulfates. Data are also available to
characterize the physical and chemical
properties of classes of organic and metal
compounds. These data are not consid-
ered in available exposure models, but
they are important for assessing the
clearance and distribution characteris-
tics of metal and organic compounds.
Summaries of data useful for exposure
assessments are not available in the
present references; compilation of such
data is beyond the scope of this report.
Classification and summarization of data
on specific organic and metal compound
classes from the voluminous available
data should significantly enhance the
capability for making exposure
estimates.
In conjunction with classifying and
summarizing available data on the
chemical and physical properties of
inhalable particulate matter, a compar-
ison of the assumptions used in the most
commonly available exposure models
would be useful in assessing the state
of the art for estimating exposure.
Literature sources discuss experimental
results related to specific models, but a
comparison of assumptions and param-
eters used in the various models has not
been documented.
The most immediate needs for improv-
ing exposure assessment techniques are
the development of an improved classi-
fication system for estimating particle
size distribution and a compilation of
pollutant-specific or compound class-
specific chemical and physical character-
istics. These would improve the basis for
estimating clearance and distribution
over what is available from current
summaries. The basic data needed to
accomplish this may be available from
existing sources. Assembly of a usable
data base is needed.
The needs for expanded information on
the mechanics of clearance from the
pulmonary region and for information on
the effects of pulmonary disease are
equally critical to the development of an
improved risk-assessment methodology.
These areas, however, will require
significant resources and time, as they
would involve extensive laboratory and
clinical testing.
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David Armentrout and Barbara Locke are with PEI Associates Inc Cincinnati
OH 45246.
Michael H. Shapiro is the EPA Pn iect Officer (see below)
The complete report, entitled "Ch iractenstics. Deposition and Fate of Inhaled
Paniculate Matter." (Order No. PB 87-2J4 854/AS; Cost: $13.95. subject
to change J 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:
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Washington, DC 20460
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
U.S.GFRCIALM.
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Official Business
Penalty for Private Use $300
EPA/600/S8-87/002
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60604
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