AIR QUALITY CRITERIA
P ARTICULATE MATTER
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Consumer Protection and Environmental Health Service
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450R69101
AIR QUALITY CRITERIA
FOR
PARTICULATE MATTER
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Consumer Protection and Environmental Health Service
National Air Pollution Control Administration
Washington, D.C.
January 1969
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National Air Pollution Control Administration Publication No. AP—49
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Preface
Air quality criteria tell us what science has
thus far been able to measure of the obvious
as well as the insidious effects of air pollu-
tion on man and his environment. Such cri-
teria provide the most realistic basis that we
presently have for determining to what point
the levels of pollution must be reduced if we
are to protect the public health and welfare.
The criteria that we can issue at the pres-
ent time do not tell us all that we would like
to know. If all of man's previous experience
in evaluating1 environmental hazards pro-
vides us with a guide, it is likely that im-
proved knowledge will show that there are
identifiable health and welfare hazards as-
sociated with air pollution levels that were
previously thought to be innocuous. As our
scientific knowledge grows, air quality cri-
teria will have to be reviewed and, in all
probability, revised. But the Congress has
made it clear that we are expected, without
delay, to make the most effective use of the
knowledge we now have.
The Air Quality Act of 1967 requires that
the Secretary of Health, Education, and Wel-
fare ". . . from time to time, but as soon as
practicable, develop and issue to the States
such criteria of air quality as in his judgment
may be requisite for the protection of the
public health and welfare. . . . Such criteria
shall . . . reflect the latest scientific knowl-
edge useful in indicating the kind and extent
of all identifiable effects on health and wel-
fare which may be expected from the pres-
ence of an air pollution agent. ..."
Under the Air Quality Act, the issuance of
air quality criteria is a vital step in a pro-
gram designed to assist the States in taking
responsible technological, social, and politi-
cal action to protect the public from the ad-
verse effects of air pollution.
Briefly, the Act calls for the Secretary of
Health, Education, and Welfare to define the
broad atmospheric areas of the Nation in
which climate, meteorology, and topography,
all of which influence the capacity of air to
dilute and disperse pollution, are generally
homogeneous.
Further, the Act requires the Secretary to
define those geographical regions in the
country where air pollution is a problem—
whether interstate or intrastate. These air
quality control regions will be designated on
the basis of meteorological, social, and po-
litical factors which suggest that a group of
communities should be treated as a unit for
setting limitations on concentrations of at-
mospheric pollutants. Concurrently, the Sec-
retary is required to issue air quality criteria
for those pollutants he believes may be harm-
ful to health or welfare, and to publish re-
lated information on the techniques which
can be employed to control the sources of
those pollutants.
Once these steps have been taken for any
region, and for any pollutant or combination
of pollutants, then the State or States respon-
sible for the designated region are on notice
to develop ambient air quality standards ap-
plicable to the region for the pollutants in-
volved, and to develop plans of action for
implementing the standards.
The Department of Health, Education, and
Welfare will review, evaluate and approve
these standards and plans, and once they are
approved, the States will be expected to take
action to control pollution sources in the man-
ner outlined in their plans.
At the direction of the Secretary, the Na-
tional Air Pollution Control Administration
has established appropriate programs to
carry out the several Federal responsibilities
specified in the legislation.
Air Quality Criteria for Particulate Mat-
ter is the culmination of intensive and dedi-
cated effort on the part of many persons—so
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many, in fact, that it is not practical to name
all of them.
In accordance with the Air Quality Act, a
National Air Quality Criteria Advisory Com-
mittee was established, having a member-
ship broadly representative of industry, uni-
versities, conservation interests, and all lev-
els of government. The committee, whose
members are listed following this discussion,
provided invaluable advice on policies and
procedures under which to issue criteria, and
provide major assistance in drafting this
document. To facilitate the committee's work,
subcommittees were formed to provide inten-
sive efforts relating to specific pollutants—
initially for particulate matter and for sul-
fur oxides.
With the help of the Subcommittee on Par-
ticulate Matter, expert consultants were re-
tained to draft portions of this document,
with other segments being drafted by staff
members of the National Air Pollution Con-
trol Administration. After the initial draft-
ing, there followed a sequence of review and
revision by the subcommittee, and by the full
committee, as well as by individual review-
ers especially selected for their competence
and expertise in the many fields of science
and technology related to the problems of at-
mospheric pollution by particulate matter.
These efforts, without which this document
could not have been completed successfully,
are acknowledged individually on the follow-
ing pages.
As also required by the Air Quality Act of
1967, appropriate Federal departments and
agencies, also listed on the following pages,
were consulted prior to issuing this criteria
document. A Federal consultation committee,
comprising members designated by the heads
of seventeen departments and agencies, re-
viewed the document, and met with staff per-
sonnel of the National Air Pollution Control
Administration to discuss their comments.
This Administration is pleased to acknowl-
edge the efforts of each of the persons specif-
ically named, as well as the many not named
who contributed to the publication of this
volume. In the last analysis, however, the Na-
tional Air Pollution Control Administration
is responsible for its content.
JOHN T. MIDDLETON,
Commissioner, National Air Pollution
Control Administration
IV
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NATIONAL AIR QUALITY CRITERIA ADVISORY COMMITTEE
Chairman
DR. JOHN T. MIDDLETON, Commissioner
National Air Pollution Control Administration
Dr. Herman R. Amberg
Manager, Manufacturing Services Dept.
Central Research Division
Crown Zellerbach Corp.
Camas, Wash.
Dr. Nyle C. Brady
Director, Agricultural Experiment
Station
Cornell University
Ithaca, N.Y.
Dr. Seymour Calvert
Director, Statewide Air Pollution
Research Center
University of California, Riverside
Riverside, Calif.
Dr. Adrian Ramond Chamberlain
Vice President
Colorado State University
Fort Collins, Colo.
*Dr. Raymond F. Dasmann
Senior Ecologist
Conservation Foundation
Washington, D.C.
Mr. James R. Garvey
President and Director
Bituminous Coal Research, Inc.
Monroeville, Pa.
Dr. David M. Gates
Director
Missouri Botanical Gardens
St. Louis, Mo.
* Resigned, October 14, 1968.
Dr. Neil V. Hakala
President
Esso Research & Engineering Co.
Linden, N.J.
Dr. Ian T. Higgins
Professor, School of Public Health
The University of Michigan
Ann Arbor, Mich.
Mr. Donald A. Jensen
Executive Engineer
Ford Motor Co.
Dearborn, Mich.
Dr. Herbert E. Klarman
Professor of Public Health Administration
and Political Economy
School of Hygiene and Public Health
Johns Hopkins University
Baltimore, Md.
Dr. Leonard T. Kurland
Professor of Epidemiology
Mayo Graduate School of Medicine
Head, Medical Statistics
Epidemiology and Population Genetics
Section, Mayo Clinic
Rochester, Minn.
Dr. Frederick Sargent II
Dean, College of Environmental
Sciences
University of Wisconsin
Green Bay, Wis.
Mr. William J. Stanley
Director, Chicago Department of
Air Pollution Control
Chicago, 111.
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CONTRIBUTORS AND REVIEWERS
Dr. Donald F. Adams
Head, Air Pollution Research Division
College of Engineering
Washington State University
Pullman, Wash.
Dr. Mary 0. Amdur
Associate Professor of Toxicology
Department of Physiology
School of Public Health
Harvard University
Boston, Mass.
Dr. Rodney R. Beard
Executive Head, Department
of Preventive Medicine
Stanford University Medical School
Palo Alto, Calif.
Dr. Francis E. Blacet
Emeritus Professor of Chemistry
University of California at Los Angeles
Los Angeles, Calif.
Dr. L. J. Brasser
Head, Atmospheric Pollution Division
Research Institute for
Public Health Engineering
Delft, The Netherlands
Dr. Leslie A. Chambers
Professor and Chairman
Department of Environmental Health
School of Public Health
University of Texas
Houston, Tex.
Dr. Robert Charlson
Research Associate Professor of
Atmospheric Chemistry
Department of Civil Engineering
University of Washington
Seattle, Wash.
Dr. Morton Corn
Associate Professor, Department of
Occupational Health
Graduate School of Public Health
University of Pittsburgh
Pittsburgh, Pa.
Dr. Ellis F. Darley
Plant Pathologist
Statewide Air Pollution Research Center
University of California at Riverside
Riverside, Calif.
Dr. Arthur DuBois
Department of Physiology
Graduate School of Medicine
University of Pennsylvania
Philadelphia, Pennsylvania
Dr. James G. Edinger
Professor of Meteorology
University of California
Los Angeles, Calif.
Dr. Lars Friberg
Chief, Department of Hygiene
Karolinska Institute of Hygiene
Stockholm, Sweden
Dr. Sheldon K. Friedlander
Professor of Chemical Engineering
and Environmental Health Engineering
California Institute of Technology
Pasadena, Calif.
Dr. John R. Goldsmith
Chief, Environmental Hazards
Evaluation Unit
Department of Public Health
State of California
Berkeley, Calif.
Dr. Leonard Greenburg
Professor of Preventive and
Environmental Medicine
Albert Einstein College of Medicine
New York, N.Y.
Dr. Alexander Goetz
Senior Staff Consultant
National Center for Atmospheric
Research
Altadena, Calif.
Dr. Paul Gross
Director, Research Laboratory
Industrial Hygiene Foundation of
America, Inc.
Mellon Institute
Pittsburgh, Pa.
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Dr. Harry Heimann
Research Associate, Department of
Physiology
School of Public Health
Harvard University
Boston, Mass.
Dr. Walter W. Holland
Professor, Department of Clinical
Epidemiology and Social Medicine
St. Thomas' Hospital Medical School
University of London
London, England
Mr. John H. Jacobs
Principal Research Physicist
Bell & Howell Research Center
(Chicago, 111.)
Pasadena, Calif.
Dr. P. E. Joosting
Medical Service
Research Institute for
Public Health Engineering
Delft, The Netherlands
Mr. Elmer R. Kaiser
Senior Research Scientist
School of Engineering and Science
New York University
New York, N. Y.
Dr. Herbert Landesman
Consulting Chemist
Pasadena, Calif.
Dr. Phillip A. Leighton
Emeritus Professor of Chemistry
Stanford University
Palo Alto, Calif.
Dr. Mark H. Lepper
Professor of Preventive Medicine
University of Illinois College
of Medicine
Chicago, 111.
Mr. Robert H. Linnell
Staff Associate, Departmental Science
Development Section
National Science Foundation
Washington, D.C.
Mr. Benjamin Linsky
Professor, Department of Civil Engineering
West Virginia University
Morgantown, W. Va.
Dr. James P. Lodge
Program Scientist, National Center
for Atmospheric Research
Boulder, Colo.
Dr. Thomas C. Lloyd, Jr.
Associate Professor, Department of
Physiology
School of Medicine
Case Western Reserve University
Cleveland, Ohio
Mr. John A. Maga
Executive Officer
Air Resources Board, State of
California
Sacramento, Calif.
Dr. Roy McCauldin
Professor, Department of Environmental
Engineering
College of Engineering
University of Florida
Gainesville, Fla.
Dr. Herbert C. McKee
Assistant Director, Department of
Chemistry and Chemical Engineering
Southwest Research Institute
Houston, Tex.
Dr. Paul E. Morrow
Professor of Radiation Biology and
Biophysics
School of Medicine and Dentistry
University of Rochester
Rochester, N. Y.
Dr. Edward D. Palmes
Professor of Environmental Medicine
Institute of Environmental Medicine
New York University Medical Center
New York, N. Y.
Dr. James N. Pitts, Jr.
Professor of Chemistry
University of California at Riverside
Riverside, Calif.
Dr. Walter A. Quebedeaux, Jr.
Director, Harris County Air
and Water Pollution Control Division
Houston, Tex.
Vll
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Dr. Donald D. Reid
Professor of Epidemiology and Director
of Department
Department of Medical Statistics and
Epidemiology
London School of Hygiene and
Tropical Medicine
London, England
Dr. Elmer Robinson
Chairman, Environmental Research
Department
Stanford Research Institute
Menlo Park, Calif.
Dr. Stanley N. Rokaw
Chief, Pulmonary Research Section
Rancho Lcs Amigos Hospital
Los Angeles, Calif.
Dr. August T. Rossano
Professor, Air Resources Program
Department of Civil Engineering
University of Washington
Seattle, Wash.
Mr. Jean J. Schueneman
Chief, Division of Air Quality Control
Maryland State Department of Health
Baltimore, Md.
Dr. Wayne T. Sproull
Consultant in Physics
Pasadena, Calif.
Dr. Gordon H. Strom
Department of Aeronautical
Engineering
College of Engineering
New York University
New York, N. Y.
Dr. 0. Clifton Taylor
Associate Director
Statewide Air Pollution Research Center
University of California at Riverside
Riverside, Calif.
Dr. Moyer D. Thomas
Editor, Inter-Society Committee Manual of
Methods for Ambient Air Sampling and
Analysis
Riverside, Calif.
Dr. Amos Turk
Professor, Chemistry Department
The City College of the City University
of New York
New York, N. Y.
Mr. Hans K. Ury
Special Consultant
Environmental Hazards Evaluation Unit
California State Department of Public Health
Berkeley, Calif.
Mr. Ralph C. Wands
Director, Advisory Center on Toxicology
National Research Council
Washington, D.C.
Dr. Richard P. Wayne
Oxford University
London, England
Visiting Professor in Photochemistry
University of California at Riverside
Riverside, Calif.
Dr. Phillip W. West
Professor of Chemistry
College of Chemistry and Physics
Louisiana State University
Baton Rouge, La.
Dr. Warren Winkelstein, Jr.
Professor and Head, Division of
Epidemiology
School of Public Health
University of California
Berkeley, Calif.
Dr. Harold Wolozin
Professor and Chairman
Economics Department
University of Massachusetts
Boston, Mass.
Mr. John E. Yocom
Senior Research Engineer
Travelers Research Center, Inc.
Hartford, Conn.
via
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FEDERAL AGENCY LIAISON REPRESENTATIVES
Department of Agriculture
Kenneth E. Grant
Associate Administrator
Soil Conservation Service
Department of Commerce
Paul T. O'Day
Staff Assistant to the Secretary
Department of Defense
Colonel Alvin F. Meyer, Jr.
Chairman
Environmental Pollution Control Committee
Department of Housing and Urban
Development
Charles M. Haar
Assistant Secretary for Metropolitan
Development
Department of the Interior
Harry Perry
Mineral Resources Research Advisor
Department of Justice
Walter Kiechel, Jr.
Assistant Chief
General Litigation Section
Land and Natural Resources Division
Department of Labor
Dr. Leonard R. Linsenmayer
Deputy Director
Bureau of Labor Standards
Department of Transportation
William H. Close
Assistant Director for Environmental
Research
Office of Noise Abatement
Department of the Treasury
Gerard M. Brannon
Director
Office of Tax Analysis
Federal Power Commission
F. Stewart Brown
Chief
Bureau of Power
General Services Administration
Thomas E. Crocker
Director
Repair and Improvement Division
Public Buildings Service
National Aeronautics and Space
Administration
Major General R. H. Curtin, USAF (Ret.)
Director of Facilities
National Science Foundation
Dr. Eugene W. Bierly
Program Director for Meteorology
Division of Environmental Sciences
Post Office Department
Louis B. Feldman
Chief
Transportation Equipment Branch
Bureau of Research and Engineering
Tennessee Valley Authority
Dr. F. E. Gartrell
Assistant Director of Health
Atomic Energy Commission
Dr. Martin B. Biles
Director
Division of Operational Safety
Veterans Administration
Gerald M. Hollander
Director of Architecture and Engineering
Office of Construction
IX
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AIR QUALITY CRITERIA FOR
PARTICULATE MATTER
TABLE OF CONTENTS
Chapter Pa»e
Preface . iii
Introduction xiii
1 Atmospheric Particles: Definitions, Physical Properties, Sources
Concentrations 1
2 Effects of Atmospheric Particulate Matter on Solar Radiation and
and Climate Near the Ground 33
3 Effects of Atmospheric Particulate Matter on Visibility 47
4 Effects of Atmospheric Particulate Matter on Materials 63
5 Economic Effects of Atmospheric Particulate Matter 77
6 Effects of Atmospheric Particulate Matter on Vegetation 87
7 Social Awareness of Particulate Pollution 97
8 Odors Associated with Atmospheric Particulate Matter 103
9 The Respiratory System: Deposition, Retention, and Clearance of
Particulate Matter 109
10 Toxicological Studies of Atmospheric Particulate Matter 127
11 Epidemiological Appraisal of Atmospheric Particulate Matter 145
12 Summary and Conclusions 179
Appendices
A—Symbols 192
B—Abbreviations 193
C—Conversion Factors . 194
D—Glossary . 195
Author Index . 204
Subject Index 208
Acknowledgements . . 211
XI
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INTRODUCTION
Pursuant to authority delegated to the
Commissioner of the National Air Pollution
Control Administration, Air Quality Criteria
for Particulate Matter is issued in accord-
ance with Section 107bl of the Clean Air Act
(42U.S.C. 1857c-2bl).
Air quality criteria are an expression of
the scientific knowledge of the relationship
between various concentrations of pollutants
in the air and their adverse effects on man
and his environment. They are issued to as-
sist the States in developing air quality
standards. Air quality criteria are descrip-
tive; that is, they describe the effects that
have been observed to occur when the am-
bient air level of a pollutant has reached or
exceeded specific figures for a specific time
period. In developing criteria, many factors
have to be considered. The chemical and
physical characteristics of the pollutants and
the techniques available for measuring these
characteristics must be considered, along
with exposure time, relative humidity, and
other conditions of the environment. The cri-
teria must consider the contribution of all
such variables to the effects of air pollution
on human health, agriculture, materials, vis-
ibility, and climate. Further, the individual
characteristics of the receptor must be taken
into account. Table A, which appears at the
end of this introduction, is a listing of the
major factors that need to be considered in
developing criteria.1
Air quality standards are prescriptive.
They prescribe pollutant exposures which a
political jurisdiction determines should not
be exceeded in a specified geographic area,
1 Calvert, S. Statement for air quality criteria
hearings held by the Subcommittee on Air and Water
Pollution of the U.S. Senate Committee on Public
Works. July 30, 1968.
and are used as one of several factors in de-
signing legally enforceable pollutant emission
standards.
The particulate matter commonly found
dispersed in the atmosphere is composed of
a large variety of substances. Some of
these—flourides, beryllium, lead, and asbes-
tos, for example—are known to be directly
toxic, although not necessarily at levels rou-
tinely found in the atmosphere today. There
may very well be others whose toxic effects
have riot yet been recognized. To evaluate
fully the effects on health and welfare of the
presence of each of these substances in the
air requires that they be given individual at-
tention, attention as classes of similar sub-
stances, or that they be considered in con-
junction with other substances where syner-
gistic effects may occur. Such evaluations
will be made at a later time in separate docu-
ments.
This document focuses on total particulate
matter of the kind normally measured by
high-volume sampling methods, by paper-
tape sampling methods, and by dustfall col-
lection. Further, this document considers the
effects of particulate matter in conjunction
with some gaseous materials, such as sulfur
dioxide, where important synergistic effects
are observed. (Atmospheric sulfur oxides
are treated in detail in a companion criteria
document: Air Quality Criteria for Sulfur
Oxides.) No attempt is made in this docu-
ment to set up dose-response relationships
for specific particulate pollutants. Also, the
large and diverse contributions of agricul-
tural and forest management operations to
air pollution, such as insecticide spraying and
slash burning, .and the ingestion hazard to
animals and man of toxic particulate matter
deposited on plant materials, are treated only
for a few selected examples; details are be-
Xlll
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yond the scope of this document.
Methods of measuring the effects of partic-
ulate matter on meteorological conditions, at-
mospheric visibility, and materials are docu-
mented, as well as is the resulting economic
loss. The effects of particulate matter are
further considered as they relate to vegeta-
tion damage. Public awareness of air pollu-
tion and the role of particulate matter in the
odor problem are assessed. There is a chap-
ter on the respiratory system, and particu-
late deposition therein and removal there-
from, necessary to understanding of the final
chapters which survey toxicological effects
of particulate matter and the epidemiological
data for man and animals.
In general, the terminology employed fol-
lows usage recommended in the publications
style guide of the American Chemical So-
ciety. A glossary of terms, list of symbols and
abbreviations list of conversion factors for
various units of measurement, author index,
and subject index are provided.
The literature has been generally reviewed
on a worldwide basis through March 1968.
The results and conclusions of foreign in-
vestigations are evaluated for their possible
application to the air pollution problem in
the United States. This document is not in-
tended as a complete, detailed literature re-
view, and it does not cite every published
article related to atmospheric particulates.
However, the literature has been reviewed
thoroughly for information related to the
development of criteria, and the document
not only summarizes the current scientific
knowledge of particulate air pollution, but
points up the major deficiencies in that
knowledge and the need for further research.
Technological and economic aspects of air
pollution control are considered in compan-
ion volumes to criteria documents. The best
methods available for controlling the sources
of particulate air pollution, as well as the
costs of applying these methods, are de-
scribed in: Control Techniques for Particu-
late Air Pollutants.
Table A.—FACTORS TO BE CONSIDERED IN
DEVELOPING AIR QUALITY CRITERIA
Properties of Pollution:
Concentration
Chemical composition
Mineralogical structure
Adsorbed gases
Coexisting pollutants
Physical state of pollutant
Solid
Liquid
Gaseous
Rate of transfer to receptor domain
Measurement Methods:
Hi-Vol sampler
Spot-tape sampler
Dust fall bucket (rate of deposition)
Condensation nuclei counter
Impinger (liquid filled)
Cascade impactor
Electrostatic precipitator
Light scattering meter
Chemical analysis
Gas analysis (non-adsorbing)
Adsorbed gas analysis
Light scattering or attenuation
(Ringleman or visibility observation)
Colored suspension
Nucleation of precipitation
Stabilization of fog
Odor
Taste
Exposure Parameters:
Duration
Concomitant conditions, such as
Temperature
Pressure
Humidity
Characteristics of Receptor:
Physical characteristics
Individual susceptibility
State of health
Rate and site of transfer to receptor
Responses:
Effects on health (diagnosable effects, latent
effects, and effects predisposing the organism
to disease) :
Human health
Animal health
Plant health
Effects on human comfort
Soiling
Other objectionable surface deposition
Corrosion of materials
Deterioration of materials
Effects on atmospheric properties
Effects on radiation and temperature
XIV
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Chapter 1
ATMOSPHERIC PARTICLES: DEFINITIONS, PHYSICAL
PROPERTIES, SOURCES, AND CONCENTRATIONS
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Table of Contents
A. INTRODUCTION
B. PROPERTIES OF ATMOSPHERIC PARTICIPATE MATTER .
1. Surface Properties . .
2. Motion .
3. Optical Properties
C. CHEMICAL REACTIONS OF ATMOSPHERIC PARTICULATE
MATTER .
D. SOURCES OF ATMOSPHERIC PARTICULATE MATTER . .
E. ATMOSPHERIC PARTICULATE MATTER IN URBAN AREAS.
1. Suspended Particulate Matter
2. Dustfall
F. SAMPLING AND ANALYSIS OF ATMOSPHERIC
PARTICULATE MATTER
1. Particles Larger than 10^ . .
2. Particles 0.1,* to 10ft
a. Tape Samplers for Suspended Particulate Matter
b. High-Volume Samplers for Suspended Particulate Matter .
3. Particles Smaller than O.L/
G. SIZE, CHEMICAL COMPOSITION, AND SOURCE STRENGTHS
OF PARTICULATE MATTER FROM SELECTED EMISSION
SOURCES .
1. Open Hearth Furnaces
a. Chemical Composition . . .
b. Particle Size . ....
2. Incineration
a. Chemical Composition
b. Particle Size . . . . ..
3. Sulfuric Acid Manufacture: Chamber Process
a. Chemical Composition .
b. Particle Size . . . .
4. Sulfuric Acid Manufacture: Contact Process . . .
a. Chemical Composition . .
b. Particle Size
5. Cement Plants .
a. Chemical Composition . . . .
b. Particle Size .
6. Motor Vehicles .
a. Chemical Composition . . .
b. Particle Size
Fuel Oil Combustion
7.
8.
a. Chemical Composition
b. Particle Size
Combustion of Coal
a. Chemical Composition
b. Particle Size
Page
8
8
9
9
10
10
11
11
16
17
17
19
20
22
23
23
23
23
23
24
24
25
25
25
25
25
25
25
25
25
26
26
26
26
26
26
27
27
27
27
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Page
H. SUMMARY 27
I. REFERENCES . . . . 29
List of Figures
Figure
1-1 Sizes of Atmospheric Particulate Matter . . 6
1-2 Setting Velocities in Still Air at 0°C and 760 mm Pressure for Par-
ticles Having a Density of 1 g/cm3 as a Function of Particle Diameter 7
1-3 Log-Normal Distribution of Particles Showing Various Average 7
Diameters
1-4 Particle Size Distribution of Figure 1-3, Plotted Logarithmically 7
1-5 Cumulative Log—probability Curve for the Distribution of
Figure 1-4 8
1-6 Horizontal Elutriator Cut-off Characteristics . ... 17
1-7 Dustfall Data for Six Cities . 18
List of Tables
Table
1-1 Emission Inventory of Particulate Material, Tons Per Year 12
1-2 Suspended Particle Concentrations (Geometric Mean of Center
City Station) in Urban Areas, 1961 to 1965 13
1-3 Distribution of Selected Cities by Population Class and Particle
Concentration, 1957 to 1967 15
1-4 Distribution of Selected Nonurban Monitoring Sites by Category
of Urban Proximity, 1957 to 1967 . . . 15
1-5 Arithmetic Mean and Maximum Urban Particulate Concentrations
in the United States, Biweekly Samplings, 1960 to 1965 16
1-6 Emission Factors for Selected Categories of Uncontrolled Sources
of Parti culates . ... 24
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Chapter 1
ATMOSPHERIC PARTICLES: DEFINITIONS, PHYSICAL PROPERTIES,
SOURCES, AND CONCENTRATIONS
A. INTRODUCTION
Atmospheric particles are chemically a
most diverse class of substances; they do,
however, have a number of physical proper-
ties in common, and for this reason are gen-
erally classed in a single category, sometimes
referred to as aerosols.
Some workers restrict the concept of par-
ticulate matter to the solid phase; this dis-
tinction is, however, difficult to make in prac-
tice and is probably not proper. Others refer
to airborne particles as nuclei because of
their role in the nucleation of condensation,
especially of liquid or solid water. In this
document, the term "particle" is used to mean
any dispersed matter, solid or liquid in which
the individual aggregates are larger than
single small molecules (about 0.0002/t in di-
ameter), but smaller than about 500/x. [One
micron (/*) is one-thousandth of a millimeter
or one-millionth of a meter.] Particles in this
size range have a life-time in the suspended
state varying from a few seconds to several
months.
Many disciplines are involved in the study
of particles, and each appears to have devised
its own system of nomenclature to differenti-
ate classes of particles with respect to size,
physical state, origin, etc. Periodic, but rath-
er unsuccessful attempts have been made to
resolve the confusion.1 The present document
will discuss the several classes of particles by
specifying the size or size interval in microns
(AI) and, where appropriate, the physical
state. Figure 1-1 provides a graphic scheme
for relating meteorologic nomenclature for
aerosols to the particle sizes. Nonspherical
particles may be idealized as spheres which
would have the same settling rate, but even
so, size designations have frequently been
ambiguous. For example, "size" has been
taken to mean both diameter and radius.
Again some workers interpret size to mean
the physical or geometrical size, while others
mean some equivalent size based, for ex-
ample, on optical laws relating the size of
aerosol particles to the measured scattering
of a light beam. In this document, "size" ordi-
narily refers to particle diameter or Stokes'
diameter as defined below.
Particles larger than about a micron in di-
ameter settle in still air at velocities approxi-
mated by Stokes' Law:
gd2
(1-D
1871
where
v is velocity in cm/sec (settling
velocity or terminal velocity),
g is the acceleration of gravity in
cm/sec2,
d is particle diameter in cm,
PI and p., are the densities of the
particle and of air respectively
in g/cm3, and
7i is viscosity of air in poise.
The expression is precisely true only for
spheres. An upper limit to its applicability is
set by the fact that, when a certain settling
velocity is reached, the particle generates a
significant "wake". A lower limit is reached
when the particles become small enough,
around 1/x, that air resistance is no longer
continuous but is rather the result of individ-
ual collisions with air molecules. Under these
conditions the particles "slip" between mole-
cules and the Stokes' equation underesti-
mates their falling velocity. Correction fac-
tors exist to allow for this behavior, but they
need not be given here for the qualitative dis-
cussion which follows. The approximate set-
-------
NOMENCLATURE
ATOMS,
MOLECULES
(Not Particles)
AIR
ELECTRICITY
ATMOSPHERIC
OPTICS
Active
Condensation
Nuclei
CLOUD
PHYSICS
Particles
Which Contain
Main Aerosol Mass
AIR
CHEMISTRY
Suspended
Particulate Matter
ROUTINE AIR
POLLUTION
MEASUREMENTS
10-
DIAMETER.fi
FIGURE 1-1. Sizes of Atmospheric Particulate Matter2 (The figure shows the ranges of particle size (diam-
eter) of various types of participate matter which are found in the earth's atmosphere.)
tling velocities in still air at 0°C and 760 mm
pressure for particles having a density of 1
g/cm3 are:
0.1/i, 8 x 10~5 cm/sec; 1/t, 4 x 1(H cm/sec;
10/i, 0.3 cm/sec; 100//., 25 cm/sec; and
1,000/t, 390 cm/sec. (See Figure 1-2.)
In the case of a nonspherical particle, sub-
stitution of v, g, Pl, p2, and n in equation
(1-1), Stokes Law, leads to a fictitous diam-
eter, d, which is known as the Stokes or aer-
odynamic diameter. Unless otherwise stated,
the word "diameter," as applied to particles
suspended in air or gas, ordinarily means
Stokes diameter.
If the density, />, of the particles is not
known, it may arbitrarily be assigned a value
of 1 g/cm 3; in this case d is no longer the
"Stokes diameter" but rather the "reduced
sedimentation diameter"—that is, the diam-
eter of a spherical particle of unit density
having the same terminal fall velocity in still
air as the particles in question.
The geometrical diameter of a particle will
be smaller than the reduced sedimentation di-
ameter if the particle has a density greater
than 1. A few quantitative examples can be
given:3 a l-/t sphere of lead with a density of
approximately 11 has a reduced sedimenta-
tion diameter of 3.4,*; a bubble of air in water
with an outer diameter of I/* and a water
film thickness of 0.1/t and consequently a den-
sity of approximately 0.5 g/cm3 has a reduced
sedimentation diameter of 0.7/t. Nonspherical
particles can also be assigned a "diameter"
based on their settling rate. A rectangular
plate of density 1 g/cm3, and dimensions 5 X
5x0.5ju, has a reduced sedimentation diam-
eter near 2/j..
Some of the smallest particles may be no
more than statistical aggregations of gas
molecules which act as a particle at one in-
stant and cease to exist at the next. Solid
particles and liquid droplets may be formed
in the atmosphere by condensation of a va-
por. Solid particles produced by abrasion or
grinding are not sphercial and are called
dust.
This discussion of size classes must not
obscure the fact that there is a continuous
spectrum of sizes among the particles in the
-------
COUNT MODE (0.619/i)
COUNT MEDIAN (1.0//>
ARBITRARILY SET AT ONE
COUNT MEAN (1.272U)
DIAMETER OF AVERAGE
MASS (2.056 H)
AREA MEDIAN (2.614W
AREA MEAN (3.324 JZ)
MASS MEDIAN (4.226U)
MASS MEAN -
(5.374/Z)
2345
PARTICLE DIAMETER, U
ID'1
10-
DIAMETER OF PARTICLE, MICRONS
FIGURE 1-2. Settling Velocities in Still Air at 0° C
and 760 mm Pressure for Particles Having a Den-
sity of lg/cm3 as a Function of Particle Diameter.
(This graph shows that, for spherical particles of
unit density suspended in air near sea level, Stokes
law applies over a considerable range of particle
sizes, where the line is straight, but that correction
is required at the extremes where the line begins
to curve.)
atmosphere and a corresponding continuous
gradation of all their size-dependent proper-
ties. The distribution of particle sizes usually
encountered approximates closely a log-nor-
mal distribution. In this distribution, the
familiar symmetrical bell-shaped probabili-
ty curve appears for a frequency graph plot-
ted against the logarithm of the particle size.
In this graph, the ordinate is the number of
particles per unit log (particle size) interval.
Figures 1-3 and 1-4 show the direct and
logarithmic frequency distribution curves for
for the log-normal distribution. In practice, a
cumulative distribution is plotted on special
graph paper with log-probability scales so
FIGURE 1-3. Log-normal Distribution of Particles
showing Various Average Diameters.1 (The graph
is drawn from probability theory, assuming a count
median diameter of lju, and shows the numerical
values relative to that diameter of several other
weighted average diameters discussed in the text.)
.0.5)
PARTICLE SIZE, JU
FIGURE 1-4. Particle Size Distribution of Figure 1-3,
Plotted Logarithmically. (If the particle size distri-
bution is log-normal, the graph is symmetrical
when plotted logarithmically. The figure should be
contrasted with Figure 1-3.)
-------
that a straight line is obtained if the distribu-
tion is truly log normal; the best line is fitted
either by eye or mathematically. Such a plot
is shown in Figure 1-5, and the experimental
points give an idea of the extent to which the
size distribution of a typical industrial dust
approximates to log-normal.
A distribution curve based on an exact
mathematical function can be specified in
terms of two parameters. In the case of the
log-normal distribution, two frequently used
defining parameters are (1) the most proba-
ble size, which in this distribution is identical
with the geometric mean, Mg, and (2) the
geometric standard deviation,
-------
specifically by a chemical interaction between
the surface and the gas, the process is known
as chemisorption. Absorption refers to the
situation in which the gas is dissovled into
the particle.
A vapor (i.e., a gas below its critical tem-
perature) , present in amounts comparable to
its equilibrium vapor pressure, may lead to
a deepened sorbed layer, which then takes on
the character of a layer of true liquid or solid.
If the vapor is supersaturated, a droplet or
crystal may grow by further condensation on
the sorbed layer. The net result is nucleation,
a phenomenon which deserves more consid-
eration. A pure vapor, free of particles, must
be highly supersaturated before a condensed
phase will form from it, because an energy
barrier separates the molecular from the par-
ticulate state.
Two like molecules of gas will not general-
ly stick together, and an aggregate of three
molecules is still less likely to retain its iden-
tity for any length of time. A small aggregate
of molecules is therefore unstable. On the
other hand, if a particle is split in two, energy
is required to create the new surfaces, since
the combined surface area of the two frag-
ments is greater than that of the original
particle (surface energy increases with a de-
crease in size). At some point, these two
trends of decreasing stability meet at a maxi-
mum which corresponds to a certain particle
size. If a molecular aggregate can reach this
size, then the addition of a single molecule
puts it over the energy barrier and it will be- -
come more stable by collecting still more mol-
ecules. Conversely, the loss of a single mole-
cule from a nucleus of critical size can de-
stroy its stability with the probable result
that it will return to the molecular or gaseous
state.
The important point is that the critical
particle generally contains some tens of mole-
cules which must all come together at once.
Unless the vapor concentration is high, this
is an improbable event; for some substances,
homogeneous nucleation may even require
supersaturations of many hundredfold. How-
ever, a complete sorbed layer on a particle
surface behaves like a drop of the same diam-
eter as the particle, and the energy barrier to
producing a droplet is avoided. Since parti-
cles are always present in the atmosphere,
nucleation on them is of widespread occur-
rence.
The last of the surface properties of conse-
quence is adhesion. All available evidence
suggests that solid particles with diameters
less than l/i (and liquid particles regardless
of size) always adhere when they collide
with each other or with a larger surface.
Other factors being equal, reentrainment or
rebound becomes increasingly probable with
increasing particle size. Alternatively, the
adhesive property can be considered in terms
of the surface energy of small particles or
in terms of the more complex shear forces
acting to dislodge the larger particles.
2. Motion
The second major class of properties com-
mon to all particles, regardless of composi-
tion, is their mode of motion. Particles with
sizes less than 0.1/t undergo large random
(Brownian) motions caused by collision with
individual molecules. Particles larger than
1/i have significant settling velocities, and
their motions can vary significantly from the
motion of the air in which they are borne.
For particles between O.I/* and I/*, settling
velocities in still air, though finite, are small
compared with air motions. Despite fairly
high concentrations, coagulation is some-
what slower as compared with particles
smaller than 0.1/« because of decreased
Brownian motion. Nevertheless, the oper-
ation of this mechanism, together with the
processes which generate larger particles and
which remove particles from the air, causes
the whole population of particulate matter in
the air to tend towards a constant size dis-
tribution.
Although actual settling times in the at-
mosphere tend to differ from those computed
from Stokes Law, because turbulence tends
to offset gravitational fall, the particles
larger than 5/x or 10/j. are removed to a large
extent by gravity and other inertial proc-
esses.
3. Optical Properties
The final class of physical properties to
be discussed is that of the behavior of par-
ticles towards light. This behavior is clearly
-------
of importance in effects on visibility, and it
is through their optical effects that particles
are usually perceived in the atmosphere.
Once again, particles in the size range O.I/*
to Ip. exhibit properties showing a transition
between two extreme cases.
Particles below O.l/* are sufficiently small
compared to the wavelength of light to obey
approximately the same laws of light scatter-
ing as molecules do. This so-called Rayleigh
scattering varies as the sixth power of the
particle diameter and is fairly inconsequen-
tial in its effects on visibility. On the other
hand, particles very much larger than 1/x
are so much larger than the wavelength of
visible light that they obey the same laws
as macroscopic objects, intercepting or scat-
tering light roughly in proportion to their
cross-sectional area. Particles in the inter-
mediate size range obey complex scattering
laws set forth by Mie;7 these laws are be-
yond the scope of the present discussion. Be-
cause the particle dimensions are of the same
order of magnitude as the wavelength of visi-
ble radiation, interference phenomena play
a complicating role, and a given scattering
behavior may correspond to several particle
sizes. Unfortunately, this is precisely the
size range which is most effective in light
scattering and thus most needful of study.
A more complete discussion of optical effects
is given in Chapter 3.
C. CHEMICAL REACTIONS OF
ATMOSPHERIC PARTICULATE
MATTER
In view of the diverse chemical composi-
tions of particles, it is not possible to make
general statements about the chemical reac-
tions of particulate atmospheric pollutants,
and the following discussion refers to some
specific reaction systems that have been
studied. Both particle-gas and particle-par-
ticle reactions can occur, but the latter class
has been studied to an even lesser extent
than the former. Such particle-particle re-
actions should certainly occur in the size
range below 0.1/x where collision between
particles is frequent, but, in particles large
enough to be readily studied, collisions are
relatively infrequent in the atmosphere be-
cause of low concentrations. Samples of par-
ticles collected on filters may, however, react
and subsequent analysis can be very mislead-
ing if this fact is not taken into account.
One of the particle-gas systems, the reac-
tion between sulfuric acid mist and ammonia
gas, was investigated by Robbins and Cadle.8
At high humidities the reaction rate was lim-
ited by diffusion of ammonia to the mist
droplets. At low humidities the droplets
were viscous enough to result in diffusion of
the reaction product away from the surface
of the drops being the rate-determining step.
This work shows the effect of accumulation
of reaction products, and attempts to explain
the role of humidity in a gas-particle reac-
tion.
Goetz and Pueschel9 reported a study
which fully reveals the complexity of even
a simplified model of the photochemical air
pollution found in Los Angeles. The one
clear relationship is that the amount of re-
action product deposited on nuclei supplied
from the gas phase is proportional to the
surface area of the nuclei. The humidity ef-
fect is complex and depends upon the
amounts and the order of addition of the
other substances present. The obvious re-
actants (olefins, nitrogen dioxide, and sul-
fur dioxide) differ in action as well. Amounts
of sulfur dioxide of the order of 2 ppm
depress aerosol formation, while larger
amounts (15-16 ppm) increase it. Nitrogen
dioxide is more effective if mixed with nuclei
before mixing with the olefin.
Interactions between sulfur dioxide and
metal oxide aerosols have recently been stud-
ied by Smith et al.10 at ambient conditions of
temperature and humidity. In measurements
that included an adsorption isotherm for sul-
fur dioxide on dispersed particles, preferen-
tial chemisorption on iron oxide and alumi-
num oxide aerosols was observed at low
sulfur dioxide concentrations (up to 2 ppm)
followed by multilayered physical adsorption
at higher concentrations.
D. SOURCES OF ATMOSPHERIC
PARTICULATE MATTER
In a broad sense, particles in the atmos-
phere are produced by two mechanisms:
those in the size range below l/i arise prin-
cipally by condensation, while larger par-
10
-------
tides result from comminution, although
there is considerable overlap. For example,
Preining et al.11 showed the presence of
many particles smaller than l/j. in the spray
from a nebulizer, while the formation of very
small drops during the rupture of bubbles
has been demonstrated.12 Dry grinding proc-
esses are rarely efficient in producing par-
ticle sizes below a few microns because of
the rapid increase in energy necessary to
produce the additional surface.
Combustion is complex in that it may pro-
duce four distinct types of particles. These
may arise in the following ways:
1. The heat may vaporize material which
subsequently condenses to yield parti-
cles in the size range between 0.1/t and
V,
2. the energy available produces particles
of very small size (below O.l/*); these
particles may be of short life as a result
of their being simply unstable molec-
ular clusters,
3. mechanical processes may reduce either
fuel or ash to particle sizes larger than
I/* and may entrain it,
4. if the fuel is itself an aerosol during
combustion, a very fine ash may escape
directly, and
5. partial combustion of fossil fuels may
result in soot formation.
Particles larger than 10/j, frequently re-
sult from mechanical processes such as wind
erosion, grinding, spraying, etc., although
raindrops, snowflakes, hailstones, or sleet
are obviously not produced in this way.
The sources of dust are usually apparent.
For example, a dustfall sample nearly always
contains particles of local soil. Another large
fraction will be materials dropped on the
ground and pulverized by vehicles, pedestri-
ans or wind action. Although actual soot
floes are increasingly absent as better home
heating is used, there may be partially burnt
trash from inefficient incinerators. Finally,
the process dust characteristic of local in-
dustry will be present. In urban locations
particles between 1/x and 10/x generally re-
flect industrial and combustion processes
with some local soil also present. In mari-
time locations, the bulk of the airborne sea
salt will be found in particles of this size.
The finer process dusts (ash, etc.) also fall
into this category. In short, atmospheric
particles in the l-/i to 10-/i range tend to have
a composition characteristic of local sources
and soil.
As mentioned before, it is difficult to form
small particles by size reduction. The class
of particles between O.l/* and 1/t compared
with the larger particles therefore tends to
contain increasing amounts of condensation
products. Products of combustion begin to
predominate together with photochemical
aerosols. Particles below 0.1/< have not been
characterized chemically but the increase
over the natural level, characteristic of cities,
seems to be entirely the result of combustion.
Table 1-1 shows typical particulate emis-
sion source data. Section G—1 gives some
typical analytical data on particulate matter
by industry source.
E. ATMOSPHERIC PARTICULATE
MATTER IN URBAN AREAS
1. Suspended Particulate Matter
The fraction of aerosol mass in the par-
ticles below 0.1/x is small and concentrations
are normally reported in number per unit
volume. Even the cleanest air rarely contains
fewer than some hundreds of particles per
cubic centimeter, and the particle count in
very polluted urban air 17 may reach 105/cm3.
The bulk of current data on suspended
particles generally does not discriminate on
the basis of size. Most data come from the
National Air Surveillance Network (former-
ly the National Air Sampling Network.18-19
Blifford 20 has applied factorial analysis to
these data to show relationships among in-
dividual pollutant species. Average sus-
pended particle mass concentrations range
from about 10 /*g/m3 in remote nonurban
areas to about 60 /ug/m3 in near urban loca-
tions. In urban areas, averages range from
60 /xg/m3 to 220 /ug/m3, depending on the size
of the city and its industrial activity. In
heavily polluted areas, values of up to 2000
yug/m3 have been recorded.
Table 1-2 lists the average suspended par-
ticle concentrations for a number of stand-
ard metropolitan statistical areas through-
11
-------
Table 1-1.—EMISSION INVENTORY OF PARTICIPATE MATERIAL, TONS PER YEAR.
Metropolitan Area
Source Class
New York-
New Jersey l3
1966
Tons Percent
Fuel combustion
Power generation
Coal ... .
Anthracite .
Bituminous
Fuel Oil
Distillate
Residual-
Natural Gas
Industrial
Coal
Anthracite
Bituminous
Fuel Oil
Distillate
Residual.. . - -
Natural Gas
Domestic
Coal
Anthracite
Bituminous
Fuel Oil
Distillate
Residual
Natural Gas
Commercial and Government
Coal
Anthracite _
Bituminous
Fuel Oil
Distillate
Residual
Natural Gas
Refuse disposal _ . _ .
Incinerator _ _ _ .
Open burning
Transportation _ - - -
Motor Vehicles . _
Gasoline
Diesel - . _
Aircraft . _ _ .
Shipping _ - _
Railroads
Industrial Process
Asphalt Batching
Asphalt Roofing
Cement Plants
Chemical Plants
Coffee Processing
Coke Plant _
Glass and Frit -
Grain Industry
134,
40,
31,
31,
7,
7,
33,
23,
8,
15,
9,
1,
8,
41,
17,
16,
1,
21,
15,
6,
1,
19,
8,
4,
3,
10,
3,
7
41,
35,
33,
22,
11,
1,
19,
__ Not
_- Not
410
042
722
47
675
593
593
727
599
442
022
420
569
479
090
588
073
767
561
206
580
326
254
726
696
139
432
707
894
281
613
663
734
245
761
630
131
,484"
914
reported
reported
58.1
17.3
13.7
13.7
3.3
3.3
14.5
10.5
3.5
6.7
4.1
0.6
3.5
17.8
7.7
7.2
0.5
9.3
6.6
2.7
0.7
8.5
3.5
1.9
1.6
4.7
1.4
3.3
18.0
15.2
14.6
9.8
4.8
0.6
8.6
Washington u
1965-66
St. Louis I5
1963
Tons Percent
19,
9,
9,
3,
1,
1,
5,
3,
3,
1,
1,
8,
280
912
890
22
19
3
351
135
135
182
23
159
34
166
735
685
50
839
154
685
592
851
891
153
738
814
661
153
146
155
6,245
5,678
4,031
1,647
410
157
1,110
Not
Not
reported
reported
55
28
28
0
0
1
0
0
0
0
0
0
9
2
2
0
5
3
2
1
16
11
0
10
5
1
3
0
23
18
16
11
4
1
0
3
.4
.5
.4
.1
.1
.0
.4
.4
.5
.1
.5
.1
.1
.1
.0
.1
.3
.3
.0
.7
.8
.2
.4
.7
.2
.9
.3
.4
.4
.0
.3
.6
.7
.2
.5
.2
Tons
86,800
22,400
22,400
68
39,000
37,990
683
423
19,900
18,873
671
354
5,500
5,450
34
27
15,800
1,700
14,100
7,100
4,700
4,100
600
211
670
1,500
37,500
198
NA
3,600
NA
38
73
NA
6,695
Percent
58.9
15.2
15.2
26.5
25.8
0.5
0.3
13.5
12.8
0.5
0.2
3.7
3.7
10.7
1.2
9.6
4.8
3.2
2.8
0.4
0.1
0.5
1.0
25.4
0.1
2.4
4.5
Los Angeles w
1965
Tons Percent
8,580
4,825
730
2,425
18.8
10.5
1.6
6.6
Included with
domestic
365
365
21,535
17,155
16,425
730
4,015
365 b
13,865
365
1,095
No plants
2,920
Not reported
No plants
730
Not reported
0.8
0.8
47.0
37.5
35.9
1.6
8.8
0.8
33.5
0.8
2.4
6.8
1.6
See footnotes at end of table.
12
-------
Table 1-1 (continued).—EMISSION INVENTORY OF PARTICULATE MATERIAL, TONS PER YEAR.
Source Class
New York-
New Jersey 13
1966
Metropolitan Area
Washington 14
St. Louis 15
Los Angeles 16
1965-66
1963
1965
Tons Percent Tons Percent Tons Percent Tons Percent
Metals
Ferrous
Nonferrous
Solvent Uses c
Sulfuric Acid Mfg
Superphosphate Mfg_
Other
12,433
12,392
41
NA
192
223
14,063
8.3
8.3
0 . 1
0.2
9'.5
2,920
1,460
1,460
5,470
6.4
3.2
3.2
11.9
Not reported
No plants
365 0.8
Total 231,303 100.0 34,790 100.1 147,400 100.0 44,345
100.0
• Both aircraft and shipping.
b Both shipping and railroads.
° Includes chemical plant emissions of solvents.
NA Not available.
Table 1-2.—SUSPENDED PARTICLE CONCENTRATIONS (GEOMETRIC MEAN OF CENTER CITY STA-
TION) IN URBAN AREAS, 1961 TO 1965.
Standard metropolitan statistical area
Total
suspended particles
Benzene-soluble
organic particles
/ig/m3
Rank
Mg/m3
Rank
Chattanooga
Chicago-Gary-Hammond-East Chicago
Philadelphia
St. Louis
Canton
Pittsburgh
Indianapolis
Wilmington
Louisville
Youngstown
Denver
Los Angeles-Long Beach
Detroit
Baltimore
Birmingham
Kansas City
York
New York-Jersey City-Newark-Passaic-Patterson-Clifton_
Akron
Boston
Cleveland
Cincinnati
Milwaukee
Grand Rapids
Nashville
Syracuse
Buffalo
Reading
Dayton
Allentown-Bethlehem-Easton
Columbus
Memphis
180
177
170
168
165
163
158
154
152
148
147
145.5
143
141
141
140
140
135
134
134
134
133
133
131
128
127
126
126
123
120.5
113
113
1
2
3
4
5
6
7
8
9
10
11
12
13
14.5
14.5
16.5
16.5
18
20
20
20
22.5
22.5
24
25
26
27.5
27.5
29
30
31.5
31.5
14.5
9.5
10.7
12.8
12.
10.
12.
10.
9.6
10.5
11.7
15.5
8.4
11.0
10.9
8.9
8.1
10.1
8.3
11.7
8.3
8.8
7.4
7.2
11.9
9.3
6.0
8.8
7.5
6.8
7.5
7.6
2
19.5
12.5
4
5
12.5
6
15
18
14
8.5
1
28
10
11
23
34
16
30.5
8.5
30.5
25
42
44.5
7
23
56
25
40.5
50
40.5
39
13
-------
Table 1-2 (continued).-
-SUSPENDED PARTICLE CONCENTRATIONS (GEOMETRIC MEAN OF CENTER
CITY STATION) IN URBAN AREAS, 1961 TO 1965.
Standard metropolitan statistical area
Total
suspended particles
Benzene-soluble
organic particles
Rank
Mg/m3
Rank
Portland (Oreg.)
Providence
Lancaster
San Jose
Toledo
Hartford
Washington
Rochester
Utica-Rome
Houston
Dallas
Atlanta
Richmond
New Haven
Wichita
Bridgeport
Flint
Fort Worth
New Orleans
Worcester
Albany-Schenectady-Troy _
Minneapolis-St. Paul
San Diego
San Francisco-Oakland
Seattle
Springfield-Holyoke
Greensboro-High Point
Miami
108
108
108
105
105
104
104
103
102
101
99
98
98
97
96
93
93
93
93
93
91.
90
89
80
77
70
60
58
34
34
34
36.5
36.5
38.5
38.5
40
41
42
43
44.5
44.5
46
47
50
50
50
50
50
53
54
55
56
57
58
59
60
9.5
17.7
6.8
14.0
5.6
7.1
9.4
6.1
7.0
6.8
8.8
7.8
8.3
7.3
5.2
7.2
5.3
7.8
9.7
8.2
6.6
6.5
8.5
8.0
8.3
7.0
6.3
5.7
19.5
38
50
3
58
46
21
55
47
50
25
36.5
30.5
43
60
44-5
59
36.5
17
33
52
53
27
35
30.5
47.5
54
57
out the United States. For the most part,
measurements were taken at a single sam-
pling station in the downtown area of the
city.
Based on ten years of sampling at ap-
proximately 370 sites, the highest seasonal
average will exceed the annual mean by 15
to 20 percent. Seasonal averages for the
high 2 percent of the sites exceeded the an-
nual mean by 50 percent and the lowest 2
percent exceeded the annual mean by about
5 percent. Individual 24-hour maximum
sample concentrations vary widely from the
annual mean, and on the average this vari-
ation is from 280 to 300 percent. Variations
as high as 700 percent of the annual mean
are found for the high two percent of the
samples. Sunday and holiday data are us-
ually 15 to 20 percent below weekday con-
centrations. Table 1-3 shows the relation
of population class of urban areas to particle
concentration for the period 1958-1967,
while Table 1-4 shows the frequency distri-
bution of particle concentration in nonurban
areas for the same period.
Particle concentrations in air have both
diurnal and annual (seasonal) cycles which
for most cities are generally predictable in
shape. A city with cold winters will experi-
ence a seasonal maximum in midwinter as
a result of increased fuel use for space heat-
ing. A daily maximum in the morning,
probably between 6 and 8 o'clock, usually re-
lates to a combination of meteorological fac-
tors and an increase in the strength of
sources of particulates, including the auto-
mobile traffic.
A reflection of the effect of the strength of
various sources can also be seen in the pre-
viously mentioned lower weekend and holi-
day versus weekday concentrations.
In cities where photochemical pollution
14
-------
Table 1-3. DISTRIBUTION OF SELECTED CITIES BY POPULATION
CLASS AND PARTICLE CONCENTRATION, 1957 TO 1967.
[Avg. particle concentration A»g/m8]
Population class
>3 million
1-3 million
0 7—1 million
400-700,000
100^400,000 -
50-100,000- -
25-50,000
10-25,000
<10,000
Total urban
40
<40 to
59
3
2
5
7
1 5
1 22
60
to
79
1
7
20
24
18
7
77
80 1
to
99 :
4
30
28
12
19
15
108
LOO :
to
119 :
2
5
24
16
12
9
11
79
120 1
to
139 :
6
17
12
10
5
2
52
140 :
to
159 :
1
2
4
1
12
6
2
2
1
31
160 1
to
179 1
1 .
1
3
5
1
3
2
16
80
to :
99
1
1
2
1
?,
1
8
1
>200 (
in
1
3
3
7
fotal
:ities
table i:
2
3
7
18
99
93
71
64
44
401
Total
cities
n. U.S.A.
2
3
7
19
100
180
"5,453
' Incorporated and unincorporated areas with population over 2,500.
Table 1-4.—DISTRIBUTION OF SELECTED NON-
URBAN MONITORING SITES BY CATEGORY
OF URBAN PROXIMITY, 1957 TO 1967.21
Average particle
Category concentrations, jug/m3 Total
<20 20-39 40-59 60-79
Near urban •___
Intermediate b
Remote ° 4
Total
nonurban 4
1
5
5
11
3
6
9
1 5
11
9
1 25
a Near urban—although located in unsettled areas,
pollutant levels at these stations clearly indicate in-
fluence from nearby urban areas. All of these stations
are located near the northeast coast "population cor-
ridor."
b Intermediate—distant from large urban centers,
some agricultural activity, pollutant levels suggest that
some influence from human activity is possible.
c Remote—minimum of human activity, negligible
agriculture, sites are frequently in state or national
forest preserve or park areas.
predominates, the maximum in concentra-
tion of particles in the range from 0.1/t to I/*
may come around noon, after the sun has
had an opportunity to cause photochemical
reaction. Under these conditions, the highest
concentration of particles below O.I/* will
come earlier, and there may be no clear trend
for larger particles.
The above concentrations generally relate
to samples taken in the center-city commer-
cial district. This portion of the community
will generally not show annual average con-
centrations as high as those found in various
industrial areas; however, they are among
the higher area concentrations in a com-
munity. Annual concentrations in nearby
suburban residential areas generally will be
about one-half of that found in center city.
Particulate air pollution is not only
source- and location-dependent but is also
a function of meteorological factors causing
a variation in the natural ventilation of a
community. Air pollution episodes are char-
acterized by minimum natural ventilation,
and particulate concentrations at such times
may rise dramatically as indicated by the
following examples: during the November-
December, 1962, episode in the Eastern
United States, particulate concentrations in
several communities rose to two-to-three
times normal; 22 during the Thanksgiving
1966 episode, again in the Eastern United
States, particulate concentrations increased
by about a factor of two over mean autumn
levels. In fact, maximum citywide average
concentrations in Philadelphia, Worcester,
and Boston exceeded maximum concentra-
tions recorded for an autumn period since
1961 at the National Air Surveillance Net-
work (NASN) stations.23
Table 1-5 gives concentrations of certain
specific contaminants found in total sus-
15
-------
Table 1-5. ARITHMETIC MEAN AND MAXIMUM URBAN PARTICULATE CONCENTRATIONS IN THE
UNITED STATES, BIWEEKLYY SAMPLINGS, 1960 TO 1965.18
Pollutant
Number of
stations
Concentrations
Arith. average '
Maximum
Suspended particulates
Fractions:
Benzene-soluble organics_
Nitrates
Sulfates
Ammonium
Antimony
Arsenic
Beryllium
Bismuth
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Tin
Titanium
Vanadium
Zinc
Gross beta radioactivity..
291 105
218
96
96
56
35
133
100
35
35
103
35
103
104
104
103
35
103
85
104
99
99
323
6.8
2.6
10.6
1.3
0.001
0.02
<0.0005
<0.0005
0.002
0.015
<0.0005
0.09
1.58
0.79
0.10
<0.005
0.034
0.02
0.04
0.050
0.67
(0.8 pCi/ms)
1254
39.7
101.2
75.5
0.160
0.010
0.064
0.420
0.330
0.060
10.00
22.00
8.60
9.98
0.78
0.460
0.50
1.10
2.200
58.00
(12.4pCi/m3)
a Arithmetic averages are presented to permit comparable expression of averages derived from quarterly com-
posite samples; as such they are not directly comparable to geometric means calculated for previous years' data. The
geometric mean for all urban stations during 1964-65 was SO yug/m3, for the nonurban stations, 28 /jg/m3.
b No individual sample analyses performed.
pended participate matter. Certain sub-frac-
tional contaminants found in total particu-
lates may be related to community param-
eters; for example, average ambient vana-
dium concentrations correlate well with the
kind of residual oil used, iron and manganese
correlate and are attributed to their joint
emission from ferromanganese blast fur-
naces, and annual gasoline sales correspond
with the average lead fraction of suspended
particulates. Similarly, sulfates correlate
with particulates in those communities which
derive large amounts of energy from the
higher sulfurous fuels.24
2. Dustfall
Dustfall is the usual index of particles in
the size range greater than 10/i, and it has
mainly been reported in short tons per
square mile per month, arrived at by extra-
polation from a jar a few inches in diam-
eter to a square mile. Metric units are pref-
erable and the current trend is clearly in
their favor. Typical values for cities are
0.35 to 3.5 mg/cm-'-month (10 to 100 tons/
mile"-month), while values approaching 70
mg/cm2-month (2000 tons/mile2-month) have
been measured near especially offensive
sources.
A search for scientific interpretations or
correlations of dustfall data has been unsuc-
cessful. There is no question that, within a
given city, dustfall tends to increase with
the intensity of human activity. Further-
more, dustfall measurements are certainly
valuable in obtaining evidence against major
sources of dust. However, trying to extract
detailed information from small fluctuations
in dustfall appears to be an exercise in fu-
tility. Dustfall is complex, being affected by
the number of unvegetated vacant lots, ve-
hicular traffic, uncontrolled heavy industry,
and wind velocity. D:;sfiness of the environ-
16
-------
ment is an obvious nuisance and a compo-
nent of the economic cost of pollution.
F. SAMPLING AND ANALYSIS OF
ATMOSPHERIC PARTICULATE
MATTER
1. Particles Larger Than 10/t
Particles larger than 10/<, exist in the at-
mosphere in very low numerical concentra-
tions. The high concentrations that are
sometimes found in ducts or in work spaces
are the province of industrial hygiene and
are not considered here.
Since the largest particles have appre-
ciable settling velocities and impact readily
at low velocities, they are usually determined
gravimetrically following collection by depo-
sition in a dustfall jar.23 Although a cylin-
drical jar might be expected to collect the
equivalent of the dust content of an air col-
umn of its own diameter extending to the
top of the atmosphere, in fact the aerody-
namic effects of the jar edges, of the mount-
ing brackets for the jar, and of adjacent
structures tend to complicate the collection
pattern. Only relative significance may be
attached to the resulting data, and only then
if conditions are carefully standardized.26-28
(There is a legend of a city which decreased
its reported dustfall by half in a single year
by changing the height of its dustfall jars
from 8 to 20 feet above ground level.) There
is no definitive study of the effect on meas-
ured dustfall of the height of the collector
above ground.
Gruber29 has successfully used an adhe-
sive coating on the outside of cylindrical con-
tainers to ascertain the wind direction corre-
sponding to maximum dust content of the
air. This often permits identification of ma-
jor dust sources. Evaluation is visual. Euro-
pean practice favors flat adhesive surfaces
placed horizontally as dust collectors.30 The
advantages are not apparent, and analogous
studies using greased microscope slides for
pollen collection have shown them to be
highly variable in collection efficiency.31
Cyclonic collectors have been employed in
combination with high-volume samplers for
the selective sampling of particles.32 While
such collectors can remove virtually all parti-
cles above 5/x, they also remove a significant
amount of smaller particles. During an in-
vestigation of atmospheric protein, a small
cyclone separator was used ahead of a high-
volume sampler. Particles exhausted through
the cyclone outlet were collected on a filter of
the high-volume sampler. The samples col-
lected on the filter of the combination unit
averaged about one-half the weight of those
collected at the same time on the filter of a
high-volume sampler with no cyclone at-
tached.
A few studies 32~34 have used long horizon-
tal tunnels as fractional elutriators to deter-
mine particle size distributions. The elutria-
tor acts as a prefilter for the removal of
larger-sized particles in a manner similar to
the cyclone high-volume sampler combina-
tion. Both the cyclone and the elutriator, op-
erating on aerodynamic principles, have a
graded selectivity (Figure 1-6) rather than
a sharp cut-off point at a specific particle size.
The size range of the particles which pene-
trate the elutriator but are retained on the
filter at the outlet duct depends on the air-
flow rate through the system (Figure 1-6).
Other methods for the selective removal of
larger (nonrespirable) particles have been
described by Lippmann and Harris 36 and by
Roesler.37
The first stage of most cascade impactors 3S
collects particles larger than about 5 to 10/u.
Since, except in very dusty atmospheres, the
mass mean diameter is smaller than this, col-
lections on the first stage will be meager un-
less the sampling time is set specifically to
AERODYNAMIC SIZE,/!
FIGURE 1-6. Horizontal Elutriator Cut-off Charac-
teristics.35 (This graph shows that the elutriator
collects all particles larger than 3%^ diameter
when operated at 10 cfm, but at 50 cfm some par-
ticles as large as 7^ diameter escape.)
17
-------
give ample material. Adhesion of such large
particles is poor (Section B-l), so an ad-
hesive may be necessary to avoid bounce-off
or reentrainment.
A variation is a single-stage impactor with
size discrimination developed by Dessens.39
He used a coarse slit followed by a shaped
channel to induce turbulent deposition of
particles along a microscope slide with a
size gradation from larger to smaller.
It appears, therefore, that no presently
used technique for the concentration meas-
urement of particles larger than about 10/x is
superior to a properly installed dustfall jar;
this method is also the least expensive. How-
ever, the jar lacks time resolution since it
must usually be exposed for two weeks to a
month to obtain a significant sample. Dust-
fall jars should be more widely standardized,
and more study is needed of alternative
means of sampling the largest particles in the
atmosphere. Chapter 11 shows some correla-
tions of health effects with air pollution, us-
ing dustfall as an index of air pollution.
Any collection technique can provide a
sample for subsequent analysis, although the
adhesives used in many of the methods de-
scribed can, unless carefully chosen, inter-
fere severely with characterization of the
particles. The standard techniques used to
analyze dustfall samples generally reveal
which elements are somewhere in the sample
without giving any information as to which
particles contain which elements or what
compounds these elements represent. Never-
theless, such general chemical composition
data are often helpful. One simple type of
chemical characterization which gives this
sort of information for particles larger than
KV is morphological identification under the
microscope. Although this may be applied to
smaller particles as well, it is most effective
in the largest size range. McCrone40 has
published a photomicrographic atlas of dust
components which should permit recognition
of up to 90 percent of the particles above 10/x
in a typical urban sample. In the hands of an
experienced microscopist, this technique is
one of the most potent tools in dust analysis.
X-ray diffraction techniques will identify
chemical compounds present rather than
merely the elements.
Dustfall levels have decreased in most
cities (Figure 1-7) and there is a trend
i-
o
O
LU
250 -
200
150
DC
LU
> 100
50
PITTSBURGH ^
— — "*" CINCINNATI
CHICAGO
10
I
z
O
!
EC
LU
1935
1940
1945
1950
1955
1960
1965
FIGURE 1-7. Dustfall Data for Six Cities. (This graph is from a U.S. Government publication, but
original source of the data is unknown.)
the
18
-------
toward abandoning routine dustfall measure-
ments, as they may no longer be indicative of
pollution levels. This viewpoint is defensible,
although, since excessive dustfall is one of
the most noticeable nuisances consequent
upon air pollution, there is public pressure to
abate high dust emissions (Chapter 7).
2. Particles O.l^i to 10/*
A single group of sampling and analysis
methods generally serves for the size range
from O.lju to ID/*. This size range includes
both the bulk of the particulate mass and a
large fraction of the numbers. The prepon-
derant optical effects also arise from parti-
cles in this portion of the size spectrum, and
most of the estimation methods not involving
collection are optical. Collection and analysis
techniques in this size range have been re-
viewed by Lodge41- *'-' and discussed in two
chapters of the 1968 treatise, Air Pollution,
edited by Stern.43-44
The simplest optical technique involves use
of a photometer developed in its present form
by Volz 4" for determining air turbidity. A
simple photocell is pointed at the sun through
a series of small apertures and a glass filter
peaking at a wavelength of 500/x. An attached
sight and spirit level allow measurement of
sun angle, which corrects the reading for air
layer thickness along the path between the
instrument and the sun. A nomogram may
then be used to obtain the turbidity coeiffi-
cient. Greater accuracy, if warranted, may
be achieved by using a computer; a simple
program has been developed for the calcula-
tion.46 McCormick" found that turbidity
measurements from the bottom and from
the top of a high building gave, by difference,
a reasonable estimate of the concentration of
the intervening particulate matter. This is
the cheapest and simplest technique, although
it cannot measure continuously nor can it be
used at night or during cloudy weather.
Next in complexity is the "nephelometer"
described by Charlson.48 This device meas-
ures light scattered by particles suspended in
a defined volume of air. It is illuminated by a
flash tube placed so that nearly the total solid
angle from full forward to direct back-scat-
tering occurs. Integral scattering is recorded
and, in the absence of a powerful nearby
particle source, is very nearly a linear func-
tion of mass concentration. A disadvantage
of the method is that a constant particle-size
distribution and composition must be as-
sumed.
Other light-scattering instruments include
total forward-scattering and right-angle-
scattering photometers as well as instru-
ments which count and size individual parti-
cles.49 The latter consist of:
1. A sampling system which dilutes the
sample stream with purified air until
only one particle at a time is likely to
be in the sensitive portion of the de-
vice,
2. a light source and optics to illuminate
a small volume (a few mm3 at most)
at a defined angle,
3. a phototube (usually a multiplier)
sensitive enough to detect the indi-
vidual flashes of light as particles
pass the illuminated volume, and
4. a pulse height analyzer and counting
electronics.
A number of other principles for size an-
alysis of particles without collection were
surveyed during World War II and the im-
mediate postwar years, but none seem to
have warranted commercial exploitation ex-
cept one device to measure mobility in an
electric field. This latter technique is more
applicable to smaller particles and will be
discussed in that connection (see Section
G-3).
Cascade impactors 3S have been found to
be useful devices for simultaneously collect-
ing and classifying particles throughout most
of this size range, thereby yielding consider-
able information •r'°-"3 on the urban aerosol
size distribution of selected chemical com-
ponents including sulfate, lead, and other
metals. Similar information has been ob-
tained by use of a helical-channel centri-
fuge 54-56 as a classifier.
Goetz •~>7 has described a single-stage mov-
ing-slide impactor with some novel features.
It is part of a system which includes mirror-
surfaced collecting slides and incident dark-
field microphotometry which is particularly
well adapted to physical characterization of
particles from roughly 0.2,*, to 2/*. Informa-
19
-------
tion on coalescence tendency and heat lability
is easily obtained.
Spurny58 has studied the application of
recently developed filter material to particle
research. The filter is a plane film of polycar-
bonate which is exposed to fission fragments
and then treated to remove the radiation
damage. A number of pore sizes are avail-
able; the pores are uniform, straight, and cir-
cular in cross section. The plane upper sur-
face is ideal for both optical and electron mi-
croscopy (the latter after replication), and
the filtration characteristics are excellent.
The uniformity of the material commends its
use for gravimetric purposes and for "smoke
shade" determination. The only evident dis-
advantage at the moment is its price.
Frank and Lodge 59 have described the use
of electron microscopy for morphological
identification of several species of particles
smaller than I/*. Although the technique is
not so broadly applicable as is optical mi-
croscopy of dusts, it may permit some an-
alyses, including the identification of sulfuric
acid droplets below I//,.
In view of the extensive literature involv-
ing filter tape and high-volume samplers,
some further discussion of these devices is in
order, especially since air quality criteria
must ultimately relate to accurate measure-
ments. Both samplers are inexpensive and
durable, and both provide data which have
stringent limitations that are not always
understood.
a. Tape Samplers for Suspended Particulate
Matter
The tape sampler most widely used in the
United States has been the AISI (American
Iron and Steel Institute) sampler developed
by Hemeon and his colleagues.60 Other ver-
sions exist, but all are alike in function. A
series of portions of filter paper, usually suc-
cessive areas of a paper tape, are positioned
so as to be clamped between an intake tube
and a vacuum connection. Air is drawn
through the filter for a selected time, usually
one to four hours, and a new portion of tape
is then moved into position and sampling is
resumed.
The fundamental basis of evaluating sam-
ples is optical, although a few nonoptical
methods have been studied. The visual color
of the spots may be compared with a stand-
ard gray scale. The reflectance may be meas-
ured photometrically. The transmittance of
light through both filter and deposit may be
compared with transmittance through a clean
portion of the filter. Visual and reflectance
measurements determine the blackness of the
deposit, while transmittance measures a
function of all particles collected, and under
some circumstances measurements made by
the two techniques may not be identical. For
example, a gram of magnesium oxide smoke
collected in a single spot would not be visibly
gray and might even increase reflectance, but
would transmit no light at all. Urban particu-
late matter is not, however, pure magnesium
oxide, and, in fact, the three measures (vis-
ual, reflectance, and transmittance) gener-
ally correlate fairly well in the short run.
Over longer periods, the introduction of new
sources and the removal of old ones may be
expected to change the composition of the
particles enough to cause divergence of the
different techniques. For example, if a resi-
dential area abruptly converts from coal
heating to gas, the virtual disappearance of
soot will have an enormous effect on reflect-
ance which may not appear so strikingly in
transmittance.
Transmittance is by no means a unique
function of the total concentration of partic-
ulate matter. Stalker et «L61 compared trans-
mittance and particle concentrations in dif-
ferent parts of Nashville, Tennessee. The
slopes of the regression lines varied by a fac-
tor greater than three, and at some locations
i o correlations appeared to exist between the
two measurements.
Additional complications arise in three
ways. First, none of the methods of measure-
ment exhibit a linear relationship between
the quantity determined and the number of
particles collected. Reflectance changes will
depend on whether later deposits are re-
tained on the surface of, or penetrate deeply
into, the layers first deposited. Measurements
of transmittance are similarly dependent on
whether an added increment simply adds
thickness to the collected deposit or fills pores
and gaps, thus increasing the bulk density
but not the thickness of the layer.
20
-------
Second, the rate of sampling is not con-
stant but depends on the amount of material
already collected and the structure of the
deposit.62 Hence the assumption of a constant
sampling rate will be seriously in error, es-
pecially for heavy deposits. Averaging initial
and final sampling rates, or recording the
sampling rate continuously, represent im-
provements at the cost of greatly increased
attention to the instrument, or of increased
complexity and expense.
Third, reflectance methods lose all discrim-
ination beyond a certain deposit density.
Once the filter is covered with particulate
matter, only the exposed surface of the de-
posit affects the reflectance; the reflectance
then become a measure of the composition,
but not the amount of material collected. This
problem is recognized, but not solved, in a
proposed European standard method.63
Transmittance, which is most widely^ meas-
ured in the United States, is normally con-
verted into units of coh's per thousand linear
feet of air passing through the filter. Coh
stands for "coefficient of haze." A coh unit is
defined as that quantity of light-scattering
solids (on the filter) which produces an opti-
cal density equivalent of 0.01 when measured
by light transmission. Optical density is de-
fined as the common (decadic) logarithm of
the opacity (inverse of fractional transmis-
sion) . Thus if one-fifth of the incident light
is transmitted through the paper, as com-
pared with clean paper, the opacity is five.
A coh measurement is routinely reduced to
coh per 1,000 linear feet of air passing
through the filter tape by dividing the unre-
duced coh value by the number of thousands
of feet actually drawn in the test.
For reflectance, a RUDS test is made by
measuring the percentage reflectance of the
filter tape and similarly reducing the meas-
urement to 1,000 linear feet of air. Reflect-
ance of clean paper tape is the reference
standard, set at 100 on the reflectometer.
RUDS is an acronym for "reflectance unit of
dirt shade."
Reflectance measurements are used in vari-
ous European countries for calculating am-
bient air concentrations of "smoke" or "dark
suspended matter." 63 The darkness of the
filter stain is not considered proportional to
total particle concentration in the air but to
the concentration of "dark suspended mat-
ter" resulting primarily from combustion.
The darkness of the stain, as measured by a
reflectometer, is converted to surface concen-
tration of smoke by means of a calibration
curve. The derived surface concentration is
then translated into an ambient concentra-
tion using the relationship:
SA
C= (1-2)
V
where C = the concentration of smoke in the
air (/xg/m3),
S = the derived surface concentration
(jug/cm2),
A = the area of the filter stain (cm2),
and
V = the volume of air sampled (m3).
Experimental work on the form of the
calibration curve for deriving surface con-
centrations has been carried out in France,
the Netherlands, and the United Kingdom.
The Working Party on Methods of Measur-
ing Air Pollution and Survey Techniques of
the Organization for Economic Cooperation
and Development has proposed a Standard
International Calibration Curve (the mean
of the curves developed in the three countries
listed above) as well as a standard sampling
and measurement procedure.63
The use of the conversion curves to make
international comparisons is potentially dan-
gerous. The method has the disadvantage of
credibility; that is, it is too easy to overlook
the arbitrary nature of the units, and to be-
lieve that actual airborne particle concen-
trations have been measured. This is of con-
cern for those areas of the United States for
which air quality standards already exist; in
most cases the standards include separate
values for "airborne particulate matter" ex-
pressed in gravimetric units, and for "atmos-
pheric soiling" determined by transmittance
or reflectance measurements on deposits of
the sort described here.
For many purposes, the International
Standard Calibration Curve will be found in-
convenient. It is the empirical product of a
complex physical phenomenon (light absorp-
tion and scattering) and an arbitrary instru-
ment response. The curve is not a mathe-
21
-------
matical one, and hence computer reduction of
data is made awkward.
Still other conversion formulae have been
suggested by Kemeny64 in South Africa, by
Ellison 65 in England, and by Sullivan ee in
Australia. These workers, following Clark,67
have attempted to convert their readings
mathematically into units of milligrams per
cubic meter of "smoke" in the air. As Sander-
son and Katz 6S have correctly stated, "There
is considerable doubt whether a truly satis-
factory expression exists for the translation
of optical density readings into units related
to smoke and haze concentrations." The re-
sults of Stalker et al.,ei previously mentioned,
suggest that this may be an understatement.
The method yields only an index of and not a
measurement of absolute concentrations of
suspended particulate matter.
Notwithstanding its limitations, the tape
sampler is cheap, simple, and rugged, and it
will certainly continue to be used. It should,
however, be used with the knowledge that its
measurements, in whatever units, are arbi-
trary and artificial and without absolute
meaning. Their relative values can be useful
if the samplers, as well as their locations,
their installation, and the technique of meas-
urement, are rigorously standardized. Fur-
thermore, it must be kept in mind that long-
term trends may reflect changes in com-
position as well as in amount of airborne
particles.
6. High-Volume Samplers for Suspended
Particulate Matter
The original high-volume sampler con-
sisted of the motor and blower of a tank-type
vacuum cleaner, suitably enclosed and fitted
with a holder for flat filter paper in place of
a dust bag. Present versions are more re-
fined, but little different in concept. The use
of a blower necessitates a filter of large area1
and low air resistance, and also makes the
sampling rate very dependent on the mass of
material collected.
Current samplers J9 are generally exposed
inside a case which places the filter surface
horizontal, facing upward, under a roof
which keeps out rain and snow, and generally
prevents collection of particles larger than
about 100/i. Filters are felts of glass or syn-
thetic organic fiber. Since the fibers are sub-
stantially less than 1/j. in diameter, these fil-
ters are highly efficient despite their open
structure and consequent low resistance to
airflow. Samples are normally collected for
24 hours and sampling rates are measured at
the beginning and end of the period.
Since the filters are weighed before use, it
is possible to determine the weight of col-
lected material if one standardizes the weigh-
ing conditions, optimally at 25 °C and at rela-
tive humidities below 50 percent. Thereafter,
samples may be extracted, heated, or in-
cinerated, and determination can be made of
organic content, carbon, minerals or any
other suitable and/or interesting fraction,
element, or substance. The collected sample
is the particulate content of approximately
2,000 m3 of air, and is large enough for
nearly any sort of analysis, although care
must be used in interpreting the data. There
are a few studies on interactions between col-
lected species, loss through volatilization, and1
similar problems. The performance charac-
teristics of high-volume samplers today are
quite well understood, though reactions on
sampler filters are not.
Many analyses are plagued by the lack of a
universally applicable filter material. Glass
fiber filters are convenient for determining
total particle concentration. However, the
very fine glass fibers are water and acid sol-
uble, and the glass contains significant
amounts of a large number of metals, as well
as sulfate, silicate, and other anions. Hence
inorganic analyses are performed over a
background from the filter which-is by no
means constant. Polystyrene fiber filters can
be made extremely low in inorganic content,
but are virtually useless for organic analysis.
Membrane filters are very useful in special
applications, e.g., when alkaline metals are to
be determined.
Suspended particle concentrations, deter-
mined by high-volume samplers in urban
areas, are shown in Table 1-2. The column
listing "Benzene soluble organic particles" is
a measure of the organic particulate matter
in the total sample. Much of this material is
derived from the incomplete combustion of
fuels. The data on organics may be further.
analyzed for polycyclic aromatic hydrocarbon
22
-------
content; a possible significance of these com-
pounds in carcinogenesis is discused in Chap-
ter 10.
3. Particles Smaller Than O.l/*
Several techniques have been used sys-
tematically for the characterization of parti-
cles smaller than 0.1/t.
1. Saturation of the air and subsequent
rapid expansion to cause a high su-
persaturation: the resulting droplet
count is assumed equal to the total
particle concentration. Successively
smaller degrees of supersaturation
presumably activate only larger parti-
cles to act as nuclei. Size spectra may
be generated in this way, although the
results do not necessarily agree with
those of other methods. Most of the
available data were obtained by this
technique.69
2. Passage of the air through a long
narrow channel: The smallest parti-
cles will be removed most rapidly by
diffusion, and the extend of the ef-
fect can be calculated.70 Differential
condensation nuclei counts after dif-
ferent diffusion lengths permit deter-
mination of a size spectrum.
3. Measurement of the mobility of
charged particles in an electric field:
It is necessary to assume or to com-
pute the efficiency of electrical charg-
ing of these smallest particles to de-
rive numbers and effective sizes. Orr
and his coworkers 71 used this method
to study changes in the size of hygro-
scopic particles with relative humid-
ity, and Whitby 72 has set up a facility
for obtaining count-size distributions
of particles in air, using a series of
instruments with overlapping ranges.
4. Electron microscopic techniques have
been used to obtain particle counts as
well as information on the size and
morphology of these small particles.
Of these methods only the electrical mobil-
ity separator has been used n for chemical
characterization of particles below O.lju, but
little analytical information is now available.
The electron microscopic methods of Frank
and Lodge,59 and the earlier work of Tufts
and Lodge,73 provide some insight into the
chemical composition of the particles, al-
though even in the most favorable cases, the
authors were able to account for the com-
position of less than half of the particles
seen.
G. SIZE, CHEMICAL COMPOSITION, AND
SOURCE STRENGTHS OF PARTICULATE
MATTER FROM SELECTED EMISSION
SOURCES
A listing of source strengths is given in
Table 1-6. Composition of particles and,
where available, data on particle size distri-
bution from various sources follow.
1. Open-Hearth Furnaces
a. Chemical Composition
Analysis 7* of particulate emissions from a
200-ton oxygen-lanced open-hearth furnace,
a composite sample for all process stages, in-
dicates the following chemical composition:
Compound
Fe,03
FeO
Si02
A1203
MnO
Alkalis
P205
S
Percent
89.1
1.9
0.9
0.5
0.6
1.4
0.5
0.4
Fluorides may be present in open-hearth fur-
nace particulate emissions if fluorspar fluxes
or fluoride-containing ores are used. While
fluoride emissions are generally insignificant,
problems have been reported in the vicinity
of at least one plant which uses fluorspar
fluxes and one which uses an ore with a high
fluoride content.75
b. Particle Size
By number, the majority of particles emit-
ted by an open-hearth furnace are below
O.lju, in diameter.76 Size analysis 74 of a com-
posite sample over the entire hearth indi-
cated the following distribution:
23
-------
Diameter
(fj
2
5
10
20
40
Weight percent
less than stated size
20
46
68
85
93
2. Incineration
a. Chemical Composition
Analysis of emissions from municipal in-
cinerators in Los Angeles " indicated 20 per-
cent by weight of the discharge to be con-
densable and approximately 5 to 15 percent
of the condensate to be sulfuric acid. The
remaining- 80 percent was particulate mat-
ter containing silicon, lead, aluminum, cal-
cium, iron, and traces of other elements.
Particulate samples from the stack effluent
of municipal incinerators in Milwaukee,78
ashed and subjected to spectographic and
Table 1-6.—EMISSION FACTORS FOR SELECTED CATEGORIES OF UNCONTROLLED SOURCES OF
PARTICULATES."
Emission source
Emission factor
Natural gas combustion:
Power plants
Industrial boilers
Domestic and commercial furnaces
Distillate oil combustion:
Industrial and commercial furnaces
Domestic furnaces
Residual oil combustion:
Power plants
Industrial and commercial furnaces
Coal combustion:
Cyclone furnaces
Other pulverized coal-fired furnaces
Spreader stokers
Other stokers
Incineration:
Municipal incinerator (multiple chamber)
Commercial incinerator (multiple chamber)
Commercial incinerator (single chamber)
Flue-fed incinerator
Domestic incinerator (gas-fired)
Open burning of municipal refuse
Motor vehicles:
Gasoline-powered engines
Diesel-powered engines
Grey iron cupola furnaces
Cement manufacturing
Kraft pulp mills:
Smelt tank
Lime kiln
Recovery furnaces b
Sulfuric acid manufacturing
Steel manufacturing:
Open-hearth furnaces
Electric arc furnaces
15 Ib/million ft3 of gas burned
18 Ib/million ft3 of gas burned
19 Ib/million ft3 of gas burned
15 Ib/thousand gallons of oil burned
8 Ib/thousand gallons of oil burned
10 Ib/thousand gallons of oil burned
23 Ib/thousand gallons of oil burned
2X (ash percent) Ib/ton of coal burned
13-17X (ash percent) Ib/ton of coal burned
13X (ash percent) Ib/ton of coal burned
2-5X (ash percent) Ib/ton of coal burned
17 Ib/ton of refuse burned
3 Ib/ton of refuse burned
10 Ib/ton of refuse burned
28 Ib/ton of refuse burned
15 Ib/ton of refuse burned
16 Ib/ton of refuse burned
12 Ib/thousand gallons of gasoline burned
110 Ib/thousand gallons of diesel fuel burned
17.4 Ib/ton of metal charged
38 Ib/barrel of cement produced
20 Ib/ton of dried pulp produced
94 Ib/ton of dried pulp produced
150 Ib/ton of dried pulp produced
0.3-7.5 Ib. acid mist/ton of acid produced
1,5-20 Ib/ton of steel produced
15 Ib/ton of metal charged
a For more detailed data, consult "Control Techniques for Particulate Air Pollutants," U.S. Department of
Health, Education, and Welfare, Dec. 1968
b With primary stack gas scrubber
24
-------
wet chemistry analysis, had the following
composition:
SPECTOGRAPHIC ANALYSIS
Elements reported in percent of ashed material
Element
Calcium
Silicon
Sodium
Nickel .
Aluminum
Zinc
Magnesium
Titanium
Iron
Barium
Percent
10 +
5 +
1-10
1-10
1-10
1-10
1-10
0.5-5.0
0.5-5.0
0.1-1.0
Small amounts (less than 1 percent) of man-
ganese, chromium, copper, vanadium, tin, sil-
ver, boron, beryllium, and lead were present.
WET CHEMICAL ANALYSIS
Phosphorus
Silicate
Phosphates
Nitrates
Sulfates
Chlorides
Percent
1.46
0.88
0.62
5.0
0.02
Analysis of fly ash collected at three New
York 79 incinerators and of that emitted from
their stacks showed the following chemical
composition:
Weight percent
Collected Emitted
49.5
22.9
6.3
8.8
Silicon as Si02
Aluminum as A1203
Iron as Fe203
Calcium as CaO
Magnesium as MgO
Sodium as Na2O 1
Potassium as K2OJ
Titanium as Ti02
Sulfur as S03 .
2.2
6.0
1.3
3.0
36.3
25.7
7.1
8.8
2.8
10.4
0.9
8.0
b. Particle Size
Analysis of the particulate emissions from
the Los Angeles municipal incinerators in-
dicated 30 percent (by weight) of the par-
ticles were less than 5/t in diameter. Particle
size analysis of the samples collected at the
Milwaukee7S incinerators showed the fol-
lowing distribution:
Diameter
(ft)
5
10
20
30
44
Weight percent
less than stated size
6.0
20.5
47.2
68.7
89.2
3. Sulfuric Acid Manufacture: Chamber
Process
a. Chemical Composition
Acid mist emissions contain sulfuric acid
and dissolved nitrogen oxides. The nitrogen
oxides constitute approximately 10 percent
by weight of total acid mist emissions.
b. Particle Size
The weight percentage of acid mist par-
ticles less than 3^i in diameter found in sam-
ples from two chamber acid plants, one using
molten dark sulfur and one using solid sul-
fur, were 10.1 percent and 3.5 percent re-
spectively.
4. Sulfuric Acid Manufacture: Contact
Process so
a. Chemical Composition
Discharge gases contain sulfuric acid mist
as well as unabsorbed sulfur trioxide, which
converts to acid mist upon reaching the at-
mosphere. Trace amounts of nitrogen ox-
ides may arise if the fuel used in the proc-
ess contains nitrogenous matter.
b. Particle Size
In plants where particle size has been de-
termined, the weight percentage of particles
3//. or less in diameter leaving the absorber
unit ahead of any mist recovery equipment
ranged from 7.5 percent to 95 percent. The
mean percentage was 63.5.
When oleum is produced, the proportion
of acid mist particles smaller than 3/i in di-
ameter increases. In one plant, the percent-
age rose from 9.5 percent to 54 percent.
5. Cement Plants
a. Chemical Composition
Chemical analysis of the raw kiln feed
dust and the kiln dust from the precipitator
outlet of portland cement plants in the Le-
25
-------
high Valley, Pennsylvania, region showed
the following composition:
Weight percent
Compound*
CaO
CaCO3
SiO,
A1203
Fe203
MgO
Na20
K20
MnO
Ti02
CuO
Ignition Loss
*No determination
Raw kiln
feed dust
(Average for
three types
of cement)
75.9
13.4
3.7
2.1
Dust from
precipitator
outlet (Average
of three
samples)
40.9
18.8
7.1
9.6
2.5
1.1
7.3
0.2
0.1
Trace
12.7
of sulfur made.
b. Particle Size
Examples of the distribution of particle
sizes in cement plant raw kiln feed and kiln
emissions are indicated below:
Raw kiln feed Kiln emissions
Diameter weight percent weight percent
(tt) less than stated size less than stated size
Ref. 81 Ref. 81 * Ref. 1
60
50 .
40 .
30 .
20 .
10
5
2.5
a Average of two samples
6. Motor Vehicles
a. Chemical Composition
Particles contained in vehicle exhaust in-
clude lead compounds, carbon particles, motor
oil, and nonvolatile reaction products formed
from motor oil in the combustion zone. The
reaction products include high molecular
weight olefins, carbonyl compounds (alde-
hydes and ketones), and free acids. Lead
particles in the exhaust are principally in the
from of PbClBr, the <* and /3 forms of NH4C1.
81.4
73.1
63.8
53.3
41.5
23.5
10.8
96.5
92.9
84.6
56.3
15.5
97-100
95-100
85-95
70-90
50-70
30-55
20-40
10-35
2PbClBr and 2NH4C1 • PbClBr. Particulates
discharged through the blowby consist al-
most entirely of unchanged lubricating oil.82
b. Particle Size
Analysis83 of diluted exhaust from automo-
biles operated at crusing conditions showed
a particle concentration of 40 to 52/ng per
liter of exhaust. From 62 to 80 percent of the
particulate mass consisted of particles with
aerodynamic diameters below 2/j at unit den-
sity. The lead content of particulate emis-
sions averaged about 40 percent and ap-
peared to be independent of particle size.
Measurements S4 with undiluted auto exhaust
indicate that about 90 percent by weight of
exhaust lead is contained in particles with
diameters below 0.5/i.
7. Fuel Oil Combustion
a. Chemical Composition
The probable constituents 85 of fly ash from
oil combustion have been identified as A1203,
A12(S04)3, CaO, CaS04, Fe203, Fe2(S04)3,
MgO, MgS04, NiO, NiSO4 Si02, Na2S04,
NaHS04, Na2S2O7, V203, V2O4.V2O5, ZnO,
ZnS04, Na»C.V203> 2Na2O.V205, 3Na2O.V205,
2NiO.VL,05, 3NiO.V205, Fe203.V203, Fe203.
2V20,, Na,O.V204.5V205 and 5Na20-V204.
HV20.,.
Analysis 8e of fly ash from a plant using
residual oil produced the following percent-
age composition:
Element
Carbon
Ether Soluble
Ash (900°C)
Sulfates as S03
(Including H2S04)
Iron as Fe203
Nickel as NiO
Vanadium as V203
Silicon as Si02
Aluminum as A1203
Sodium as Na20
Test A Test B
Total solids Total solids
from burn- from burn-
ing PS 400 ing 4° API
oil (Col- oil (Col-
lected in a lected in a
laboratory glass
Electrical filter sock
precipitator at 300°F)
at230°F)
(Weight (Weight
percent) percent)
58.1a 18.1
2.3 4.4
17.4 51.2
17.5 25.0
3.1 3.7
1.8 13.2
2.5 4.7
0.6 9.7
1.6 14.9
0.9 3.0
a May include some hydrogen
26
-------
Less than 1 percent of the following ele-
ments or compounds was present: Cl, N03,
Cr02, Co203, BaO, MgO, PbO, CaO, CuO,
Ti02, Mo02, B203, Mn02, ZnO, P205, SrO,
TiO.
6. Particle Size
A literature survey8T of the size distribu-
tion of particles emitted by large oil-burning
units gave the following results:
SIZE DISTRIBUTION
(Percent by number)
0/j. to
to 2
2to
Largest size
48.4
64.2
93.5
94.8
28.8
18.8
3.2
2.2
16.7
10.0
2.0
1.5
6.1
7.0
1.3
1.0
15/i
15/i
20/i
20/x
One reference indicated 47 percent, by
weight, was less than 3/i diameter.
8. Combustion of Coal8S
a. Chemical Composition
The following ranges in chemical composi-
tion were indicated by analysis of fly ash
emissions from a variety of coal combustion
units. The figures are the extreme values
Particle Size
(/i)
10
20
40
60
80
100
200
H. SUMMARY
Aerodispersed solid and liquid particles
constitute a significant fraction of the pollut-
ants found in urban atmospheres. Such par-
ticulate matter vary greatly in chemical com-
position and consist of multimolecular assem-
blies that may range in complexity from salt
crystals and acid droplets to heterogeneous
liquid and solid aggregates and living cells.
In this document, a particle is any dispersed
matter, solid or liquid, in which the indi-
WEIGHT PERCENT LESS THAN
Pulverized Fuel Cyclone
Fired Furnace Furnace
30 76
50 83
70 90
80 92
85 94
90 95
96 97
STATED SIZE
Spreader
Stoker-Fired
Furnace
10
20
37
47
54
60
—
found in four investigations, each of which
reports wide ranges also.
Percentage
Compound of fly ash
Carbon, C 0.37-36.2 *
Iron (as Fe203 or Fe304) . . 2.0 -26.8
Magnesium (as MgO) 0.06- 4.77
Calcium (as CaO) 0.12-14.73
Aluminum (as A1203) 9.81-58.4
Sulfur (as SO,) 0.12-24.33
Titanium (as TiOa) 0 - 2.8
Carbonate (as CO3) , 0-2.6
Silicon (as Si02) 17.3 -63.6
Phosphorus (as P2O5) . 0.07-47.2
Potassium (as KL,0) 2.8 - 3.0
Sodium (as Na20) 0.2 - 0.9
Undetermined 0.08-18.9
a Ignition loss
b. Particle Size
Estimated particle size distributions 8S for
four broad classifications of combustion
equipment are listed below. All distributions
represent the size of the particles leaving the
boiler or furnace before any control equip-
ment. The distributions reported for all four
equipment classifications ranged widely;
those shown in the table are considered
"typical."
Stoker-Fired
(Other-than
Spreader)
7
15
26
•36
43
50
66
vidual aggregates are larger than single
molecules (about 0.0002/*), but smaller than
about 500/i diameter.
Atmospheric particles have size-dependent
dynamic, optical, and electrical properties,
and are characterized by such surface activi-
ties as sorption, nucleation, and adhesion.
Particles in the size range below O.I//, dis-
play a behavior similar to that of molecules
and are characterized by large random mo-
tions caused by collisions with gas molecules.
27
-------
In addition, they frequently collide with each
other and form larger aggregates. Particles
larger than I//, have significant settling veloci-
ties; their motions deviate from the motion
of the air in which they are borne, and their
rates of coagulation into larger aggregates
are low. The aerodynamic behavior of parti-
cles with diameters from 0.1/t to 1/t is transi-
tional between these two regimes. Particles
larger than 10/* have rapid settling velocities
and therefore remain in the air for relatively
short durations. The size range between 0.1/t
and 10/t accounts for the bulk of the particu-
late mass in the atmosphere.
Particles below 0.1/* obey the same laws of
light scattering as molecules do and their ef-
fects on visibility are inconsequential. Parti-
cles very much larger than I//, obey the same
optical laws as macroscopic objects, inter-
cepting or scattering light roughly in propor-
tion to their cross-sectional area. Particles
between O.l/* and a few microns obey the very
complex scattering laws set forth by Mie.
This is the particle size range that is most ef-
fective in scattering light. (See Chapter 3.)
Particles in the atmosphere can be said to
originate by two types of mechanism. Small
particles in the size range below I/* arise prin-
cipally by condensation and combustion,
while the larger particles with the exception
of rain, snow, hail, and sleet, result from
comminution. Although the chemical compo-
sition of particles below O.I//, diameter has
not been widely studied, the increase over
natural levels of particles in this size range
seems to be entirely due to combustion. Com-
bustion products and photochemical aerosols
make up a large fraction of the particles in
the range of 0.1-/x to I-/* diameter. Particles
between I/* and 10/i generally include local
soil, fine dusts emitted by industry and, at
maritime locations, airborne sea salt. Indus-
trial sources of particulate matter include
municipal incineration, cement plants, steel
mills, sulfuric acid manufacturing, industrial
furnaces, kraft pulp mills, and others. Parti-
cles larger than 10/x diameter frequently re-
sult from mechanical processes such as high-
way construction, wind erosion, grinding,
spraying, etc., and include material that is
dropped on the ground and pulverized by ve-
hicles and pedestrians.
Dustfall measurements provide a rough
index of those particles which readily settle
out of the air. Typical values encountered in
urban areas range from 0.35 mg/cm2-month
to 3.5 mg/cm2-month (10 tons/mi2-month to
100 tons/mi2-month) while values approach-
ing 70 mg/cm2-month (2000 tons/mi2-month)
have been measured close to very severe
sources. Levels of dustfall have apparently
declined in cities, and dustfall measurement
is probably not useful as an index of overall
particulate levels. Nevertheless, dustfall it-
self constitutes a nuisance, and its measure-
ment provides some indication of urban
dirtiness.
A number of methods are available to
measure the mass concentration of suspended
particles. Optical techniques, such as the sun
photometer, the integrating nephelometer,
and light-scattering counters, provide an in-
dication of particle concentrations in the size
range from 0.1/* to 10/*. Two of the most com-
mon instruments for measuring mass con-
centrations are spot samplers and high-vol-
ume samplers. In the former, air is drawn
through an exposed portion of a paper tape;
then the tape is moved to expose another
spot. The spots that result on the tape are
evaluated optically by measuring their light
reflectance or transmittance. Although the
spot sampler is cheap, simple, and rugged, its
use is better suited to the determination of
relative rather than absolute mass concen-
trations. High-volume samplers employ a
blower which sends air through a special
filter over a specified time period. By weigh-
ing the material collected by the filter, the
mass concentration can be readily deter-
mined; chemical analyses also can be carried
out. High-volume sampling is the method of
choice for measuring particulate levels. As
with any other point-sampling method, the
location of the sampling instrument is very
critical, and data for an entire city should not
be based on a single sample located at a
single place.
Most of the data on suspended particulates
come from the National Air Surveillance Net-
work (NASN), which employs the high-vol-
ume sampler. NASN currently consists of
about 200 urban and 30 nonurban stations,
and it is supplemented by State and local
28
-------
networks. Based on these data, annual geo-
metric mean concentrations of suspended
particulate matter range from 60 jug/m3 to
about 200 /xg/m3 in urban areas. The maxi-
mum average concentrations for 24-hour
periods is about 3 times the annual mean
with values of 7 times the mean occurring in
about 2 percent of the communities. In gen-
eral, mean particulate concentrations corre-
late with urban population class, but there is
a wide range of concentrations within each
urban population class, and many smaller
communities have higher concentrations than
larger ones. In nonurban areas, typical geo-
metric mean concentrations range between
10 /xg/m3 and 60
I. REFERENCES
1. Kreichelt, T. E., Kemnitz, D. A., and Cuffe, S. T.
"Atmospheric Emissions from the Manufacture
of Portland Cement." U.S. Dept. of Health, Edu-
cation, and Welfare, National Center for Air
Pollution Control, Cincinnati, Ohio. PHS-Pub-
999-AP-17, 1967.
2. Corn, M. "Nonviable Particles in the Air." In:
Air Pollution, Chapt. 3, Vol. 1, 2nd edition, A. C.
Stern (ed.), Academic Press, New York. 1968,
pp. 47-94.
3. Goetz, A. "Parameters for Biocolloidal Matter in
the Atmosphere." Proc. Atmos. Biol. Conf., 1965,
pp. 79-97.
4. "Deposition and Retention Models for Internal
Dosimetry of the Human Respiratory Tract."
Task Group on Lung Dynamics for Committee II
of the International Radiological Protection Com-
mission, Chairman, P. E. Morrow. Health Phys-
ics, Vol. 12, pp. 173-207, 1966.
5. Cadle, R. D. "Particle Size." Reinhold, New York,
1965, 390 pp.
6. Drinker, P. and Hatch, T F. "Industrial Dust,
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32
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Chapter 2
EFFECTS OF ATMOSPHERIC PARTICULATE MATTER ON
SOLAR RADIATION AND CLIMATE
NEAR THE GROUND
-------
Table of Contents
Page
A. INTRODUCTION 35
B. EFFECTS OF PARTICULATE MATTER IN THE ATMOSPHERE
ON VISIBLE RADIATION 35
C. EFFECTS OF PARTICULATE MATTER IN THE ATMOSPHERE
ON TOTAL SOLAR RADIATION . 38
1. Physical Factors ... 38
2. Seasonal Variations . . 39
3. Weekly Variations 39
4. Other Variations . 40
D. INFLUENCE ON PRECIPITATION 40
E. RELATION TO WORLDWIDE CLIMATE CHANGE 42
F. SUMMARY 43
G. REFERENCES . 44
List of Figures
Figure
2-1 Relation of Solar Transmissivity to Height Above Ground in "Pol-
luted" and "Clean" Areas . 36
2-2 Annual Variation of the Ratio of Illumination Levels in Central Lon-
don and at Kew (•), and of Concentration of Particulate matter at
kew (o) . 37
2-3 Causes of Cyclical Diurnal Smoke Variations 41
2-4 Yearly Cycle (Averaged Over Six Years) of Deposited Pollutants 41
2-5 Precipitation Values at Selected Indiana Stations and Smoke-Haze
Days at Chicago . 42
List of Tables
Table
2-1 Approximate Association Between Atmospheric Aerosol Concentra-
tions and Relative Solar Radiation Levels 39
2-2 Loss of Sun's Radiation in Three European Cities Over That in the
Adjacent Country . .... 40
2-3 Mean Number of Condensation Nuclei for Various Ranges of Dust
Concentrations in City Air ... . .40
34
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Chapter 2
EFFECTS OF ATMOSPHERIC PARTICULATE MATTER ON SOLAR RADIATION
AND CLIMATE NEAR THE GROUND
A. INTRODUCTION
Particles in the atmosphere play several
roles in the behavior and determination of
the weather. Among the most obvious is the
effect they have on the radiation from the
sun. They scatter the light to greater or lesser
extents in different wavelength regions, de-
pending on their size, character, and concen-
tration, and thus provide the sky with its
variable hues, its colorful dawns and sunsets,
and also dense hazes and dark urban palls.
More subtle changes are occasioned by parti-
cles when they reduce the amount of solar en-
ergy that reaches the ground.
Particles play a less advertised but very
essential role in the formation of clouds.
Without them, liquid water clouds could not
form except at supersaturations of several
hundred percent. However, the sort of parti-
cles required (called condensation nuclei) are
provided in overabundance by natural proc-
esses. Only to the extent that higher-than-
normal nuclei concentrations can affect the
cloud-forming process, does man's introduc-
tion of additional particulate material into
the atmosphere produce changes in observed
cloud structure and occurrence.
The kinds of particles which cause precipi-
tation from clouds, in contrast to those neces-
sary for cloud formation, are frequently in
short supply in the atmosphere. In warm
(above freezing) clouds, the requirement is
a wide distribution of condensation nuclei,
some of which are giant hygroscopic nuclei
larger than 1/x. These "giants" promote the
rapid growth of cloud droplets by producing
some droplets large enough to fall with re-
spect to the others. These grow rapidly by
sweeping up smaller drops and very soon be-
come massive enough to fall from the base of
the cloud as rain.
Another kind of particle is required to
stimulate the rapid transformation of cloud
droplets into precipitation in supercooled
(subfreezing) parts of clouds. Such particles
are termed freezing nuclei. Without these,
the water droplets would not freeze except
at temperatures below — 40°C. Once frozen,
small ice particles grow rapidly at the ex-
pense of the surrounding water droplets and
begin to fall as snow. They may later melt to
become rain. Dramatic changes in cloud
structure have been achieved by seeding su-
persaturated clouds with appropriate freez-
ing nuclei. There is evidence, discussed below,
that some observed changes in precipitation
patterns in a few sections of the country can
be ascribed to the inadvertent seeding of
clouds by industrial contaminants.
Finally, tentative as our current informa-
tion and understanding may be, the long-
range potential effect of adding more and
more particles to the atmosphere cannot be
ignored. As more is learned about the general
circulation of the atmosphere and the deli-
cate balance between incoming and outgoing
radiation (the "throttle on the atmospheric
engine"), it seems increasingly possible that
small changes such as those occasioned by in-
creasing particle loads in the atmosphere
may produce very long-term meteorological
effects.
B. EFFECTS OF PARTICULATE MATTER
IN THE ATMOSPHERE ON VISIBLE
RADIATION
Stable particles of negligible fall velocity
are probably the most common and persistent
air pollutants. Their optical effects in produc-
35
-------
WJLHOI3H
VI
g
•
36
-------
ing haziness, atmospheric turbidity, and a
reduction of visibility which hampers the
safe operation of aircraft and motor vehicles,
are well known. (See Chapter 3.) The solar
radiation transmissivity (![A]/!O[A] where
I [A.] is the intensity of the normal-incidence
solar radiation and IO[A] is the extra-terres-
trial value at this wavelength) varies with
height and is strongly influenced by the dust
loading in the lower atmosphere.1 Figure 2-1
illustrates the relation of transmissivity at
A = 5000 A to height in the atmosphere above
an urban area under varying conditions of
particulate loading. In the case of heavily
polluted air, this radiation may be reduced by
more than one-half in the lowest 300 meters
of the atmosphere. There is also an increased
attenuation of visible radiation near the
ground in clean air but the amount is small
by comparison (Figure 2-1).
It is well known that the reduction or at-
tenuation of visible radiation in industrial-
ized urban areas, and the attendant gloom
caused by excessive concentrations of sus-
pended particles in the air, create a need
for additional artificial illumination in of-
fices, factories, and homes, and produces
added economic stresses. This is particularly
true in winter, when the days are shorter
and the particulate content of the urban
air is greater because of greater combustion
of fuels. Data given by Shepherd 1 illustrate
some relationship, shown in Figure 2-2, be-
tween particle concentrations and relative
visible radiation levels in London during
summer and winter months. Daylight illumi-
nation was measured at two sites, one in cen-
tral London, the other in Kew Observatory, a
slightly less heavily polluted area 13 miles
WSW of the first site. As another example,
the average loss of sunlight in the city of
Leningrad compared to the countryside was
estimated to be 40 percent over the period of
a year; in winter the loss was estimated to
reach 70 percent in the city, while in summer
the loss was about 10 percent.3
Haze in the atmosphere due to forest fires,
dust storms, or smoke from other sources,
may become so concentrated at times that
the sun appears red in the sky despite the
absence of clouds. Just after sunrise or just
before sunset, the haze may reduce the in-
VISIBLE RADIATION
LONDON/KEW
o o
M
PARTICULATE LOADING
AT KEW, mg/m3
FIGURE 2-2. Annual Variation of the Ratio of Visi-
ble Radiation Levels in Central London and at
Kew (•), and of Concentration of Particulate
Matter at Kew (o) * (This figure indicates the
relative attenuation of light at two sites in a large
city.)
tensity of the direct sunlight so much that
one can look directly at the sun without eye
strain or injury. In other words, haze in
the atmosphere due to suspended particles
scatters the light from the sun, making it
appear dim.
Scattering of the sunlight by the particles
makes the air seem "turbid," and an optical
device called the Volz sun photometer has
been devised to measure this "turbidity"
quantitatively.4 Starting with equations 3-2
in Chapter 3 (Lambert's Law), one calcu-
lates from the readings of this instrument
a "turbidity coefficient," B, related to the
extinction coefficient b in equation 3-2, Chap-
ter 3, or more specifically to bscat defined
there. The relationship between B and b
is outlined by McCormick and Baulch,2 who
found that in a city Bz, the value of B meas-
ured by the Volz instrument at a height of
z meters above the ground, is related to B0,
the value of B measured near ground level,
by the equation
Bz=B0e-°-00346z (2-1)
37
-------
From scattering theory, McCormick and
Baulch estimate that at any height, z, up to
200 meters above the ground, the number of
particles per cubic meter, n' (z), in the ra-
dius range between 0.7/* and 1/x is given by
n'(z)=17.3xl09B0e-°-00346z . (2-2)
Both of these equations are rough approxi-
mations for light-wind, clear-sky conditions
in a city during moderate to heavy pollu-
tion situations. In terms of mass loading
near the ground, [m' (o)],
m'(o)«a03B0 Ugm-3) (2-3)
C. EFFECTS OF PARTICULATE MATTER
IN THE ATMOSPHERE ON TOTAL
SOLAR RADIATION
Landsberg 5 reports that cities in general
receive 15 percent to 20 percent less insola-
tion (on a horizontal surface) than do their
rural environs. Insolation, as used here,
means the total solar radiation received at
the earth's surface per unit area per unit
time. This discussion considers the part that
airborne particles take in the diminution of
insolation received by cities.
1. Physical Factors
The attenuation of solar radiation through
the atmosphere is caused by a number of
physical factors: -• 6-10
1. Scattering of radiation, known as
Rayleigh scattering, by the air mole-
cules, such as N2 and O,, and par-
ticles in size ranges less than the
wavelength of the solar radiation
(the scattering coefficient is inversely
proportional to the fourth power of
the wavelength of the incident ra-
diation; hence the short wavelength
radiation is scattered most, so that
the sky appears to be blue) ;
2. Selective absorption by the gaseous
constituents of the atmosphere such
as ozone and C02, and by water va-
por; and
3. Scattering and absorption by atmos-
pheric dusts and particulate matter
of size greater than in (a) .
The attenuation of solar radiation by wa-
ter vapor and ozone is negligible in the visible
wavelength region usually studied.6-T- "
The scattering of light by aerosol particles
in ambient air is a complicated process. Part
of the incident light is transmitted, part is
reflected in all directions either at the front
surface of the particle or at an internal dis-
continuity, and part is absorbed. The trans-
mission factor for scattering is a function
of the wavelength of the incident light and
the physical qualities of the scattering me-
dium. In simple cases where the form, size,
and composition of the scattering particles
are known, the factor can be derived on a
theoretical basis and is known as "Mie" scat-
tering. Chapter 3 provides a more extended
discussion.
Diffuse radiation is an important factor
in the amount of heat and light received at
any given location.3-10 The intensity and
spectral distribution of direct sunlight and
scattered daylight, and the varation of in-
tensity with time of day, season, latitude,
altitude, and atmospheric conditions such as
turbidity, are important because they affect
photosynthesis in plants and the distribu-
tion of plants and animals on earth, the
weathering of natural and man-made ma-
terials, climate, and illumination for human
activity.9 The percentage of direct solar ra-
diation which will remain after its attenua-
tion by smoke and other atmospheric con-
Xtituents depends both on the atmospheric
turbidity caused by the smoke, and on the
altitude of the sun above the horizon, as well
as on the other factors 3 previously noted.
Except in cases of heavy particulate pollu-
tion of the atmosphere, such as may occur
in large urban centers or heavy industry
areas, it appears that the effect of turbidity
is to scatter radiation out of the direct solar
beam and to add an almost equal amount of
radiation to the diffuse beam arriving from
the rest of the sky by forward-scattering.
In cases of heavy particle concentrations,
however, the loss from the direct solar beam
greatly exceeds the gain in the downward
scattered beam, the difference being lost to
back-scattering off the top of the pollution
layer and to absorption within the polluted
layer or column.
Studies indicate a fair approximation of
38
-------
the association between atmospheric aerosol
concentration and relative solar radiation
levels, as shown in Table 2-1.
Table 2-1.—APPROXIMATE ASSOCIATION BE
TWEEN ATMOSPHERIC AEROSOL CONCEN-
TRATIONS AND RELATIVE SOLAR RADIA-
TION LEVELS.
Solar radiation, percent of
Aerosol concentration,
tig ni-3
value for 100 ^.g m-3
Total Ultraviolet
50
100
200
400
105
100
95
90
104
100
92
77
The reduction in ultraviolet light reaching
the surface may be as important as the at-
tenuation of other, longer wave, components
of solar radiation. Available data are sparse
but one study12 indicates that ultraviolet in-
tensity decreased by about 7.5 percent for
each 100 jug/m-3 increase in aerosol con-
tent of the atmosphere with an average de-
ficiency of over 20 percent in the city as com-
pared with its environs in winter. Some
studies suggest that a 5 percent reduction
in total solar radiation resulting from smoke
almost completely eliminates the ultraviolet
component.3-12 Even in a comparatively
clean atmosphere, the effective ultraviolet
drops to very low values when the sun's ele-
vation is below 30 degrees.13
The net influence of atmospheric turbidity
on surface temperature is uncertain, but for
typical turbidity indices in the United States,
it is likely to be small. The effect on solar
radiation (warming in the upper region of
the pollution layer due to extinction by the
upper region) tends to be compensated by
the effect on radiation returning to space
from the earth's surface and atmosphere.
The extent to which the solar radiation effect
prevails over the terrestrial radiation effect,
or vice versa, is dependent on a number of
factors which include:
1. the time of day and year (on which
the intensity of solar radiation is it-
self dependent);
2. the total mass and vertical distribu-
tion of the particles;
3. the size distribution of the particles;
4. relative humidity, which, in the case
of hygroscopic aerosols, may alter
the effective absorptivity and reflec-
tivity of the particles; and
5. temperature of the air and ground
(on which the intensity of the terres-
trial radiation depends).
2. Seasonal Variations
The concentration of suspended particu-
late matter which ranges from less than 60
jug/m3 to 1700 /ig/m3 in various American
cities shows a notable annual variation.
Autumn and winter particulate levels are in-
variably highest, and summer levels lowest.
The weakening of radiation caused by smoke
is less during the summer when the sun is
high than in the winter. This would be
true even if there were the same degree of
pollution in the air. The losses in intensity
of direct total solar radiation during its pas-
sage through an atmosphere polluted by
smoke may become as high as one-third in
the summer and two-thirds in the winter.3
Landsberg5 has summarized the radiation
loss data compiled by Steinhauser 13 for three
Central European cities—Frankfurt, Leip-
zig, Vienna—and their adjacent rural areas,
for the four seasons of the year. There are
contrasts in loss of solar radiation between
spring or summer and winter, as will be
seen in Table 2-2. Steinhauser and co-
workers " also reported that Vienna receives
a lesser total radiation than the nearby coun-
tryside: in winter 85 percent of the total
solar radiation of suburban Hoche Warte,
in spring 92 percent, in summer 92 percent,
and in autumn 87 percent.R-13 The absorp-
tion is strongest in the short (ultraviolet)
wavelengths.s- "• "•14
This annual cycle is observed to be a func-
tion of latitude, dependent on the changing
midday sun angle. The scattered radiation
during the summer months (May-August)
may amount to approximately 60 percent to
65 percent of the direct radiation at 60° lati-
tude and to about 45 percent at 40° latitude.
3. Weekly Variations
In addition to the seasonal and diurnal
variations or patterns of total solar radia-
39
-------
tion in urban communities, a weekly cycle
of intensity of total solar radiation has been
observed,15^17 which is related to the weekly
cycle of industrial and commercial activity.
In general, the total solar radiation received
is inversely related to the concentration of
smoke and suspended particles; thus solar
radiation measurements may be used, in the
absence of clouds, as a crude index of par-
ticulate air pollution.
Table 2-2.—LOSS OF SUN'S RADIATION IN
THREE EUROPEAN CITIES OVER THAT IN
THE ADJACENT COUNTRY.5
Solar Elevation
Season
10°
20°
30°
45°
Winter
Spring
Summer
Autumn
Percent
36
29
29
34
Percent
26
20
21
23
Percent
21
15
18
19
Percent
—
11
14
16
Mateer17 studied the total solar and sky
radiation patterns in metropolitan Toronto
from October 1937 to 1960 and compared the
radiation received on Sundays to the aver-
age of the weekday radiation readings at
the same central site. The average radiation
on Sundays for this period was 313.8 lang-
leys (1 langley = l g cal/cm2) while the mean
for the weekday radiation was 305.2 lang-
leys, a difference of 8.6 langleys or 2.8 per-
cent. The probability of obtaining such a
difference by chance was less than 0.5 per-
cent. Thus, while a real difference in radia-
tion exists between Sundays and weekdays,
the magnitude is rather small.
4. Other Variations
Hand 1S has noted that the average daily
solar radiation in various cities was signifi-
cantly higher over the entire year 1932 than
over the prior year. The largest increase in
solar radiation was found to be in New York
City ( + 21.9 percent), while Pittsburgh and
Washington showed yearly increases of 6.2
percent and 8 percent respectively. The busi-
ness depression was probably a major factor
in this increase. Records for New York,
Chicago, and Pittsburgh for the year 1932
showed the marked diminution in dust and
smoke levels resulting from the falling off
in the amount of manufacturing during this
period.
D. INFLUENCE ON PRECIPITATION
There is evidence that some of the parti-
cles introduced into the atmosphere by man's
activities can act as nuclei in processes which
affect the formation of clouds and precipi-
tation.
Condensation nuclei in the size range
greater than l/j. are often made up of hygro-
scopic particles.19-20 Because of their affinity
for water, these particles play an important
role in the transformation and condensation
of water vapor into liquid water droplets or
solid ice particles, and are of vital impor-
tance in the formation of fog, clouds, and
rain. Combustion products of man's indus-
try and technology, as well as volcanic erup-
tions and ocean spray, are significant sources
of these nuclei. A parallelism exists between
the concentration of dust and that of conden-
sation nuclei in city air. (See Table 2-3.)
Table 2-3.—MEAN NUMBER OF CONDENSATION
NUCLEI FOR VARIOUS RANGES OF DUST
CONCENTRATIONS IN CITY AIR.19
Number of
dust particles
per cm3
<500
500-999
>999
Mean number of
condensation nuclei
per cm3
189,000
211,000
223,000
A pronounced parallelism can also be
found with respect to diurnal and annual
variations in the contents of atmospheric
dust and nuclei.16-19~22 The excess production
of condensation nuclei in the air over cities
is a long established fact,5-20-23 and has been
reaffirmed with many amplifying circum-
stances.22- 23 Evidence has been presented
that giant nuclei, which may initiate the coa-
lescence process, are more abundant in in-
dustrial areas than elsewhere.16
The diurnal, weekly, and yearly cycles of
both suspended and dustfall particle concen-
trations, correspond closely to man's pattern
of activities and combustion requirements.
There are usually two diurnal peaks (see
40
-------
Figure 2-3), greater midweek concentrations
compared to Sundays, and greater mean con-
centrations in winter than in summer (see
Figure 2-4).16
A correlation has been found between pat-
terns of precipitation over cities and the ad-
n
8
CT| I I* 1 j«,, i — ii | | | | j j y j
INEFFICIENT SMOKE FROM NEIGHBORING
•COMBUSTION^^ DISTRICTS
4°JEFFECT "^Im/ SMOKE
30
X ^"*^v^
/EFFECT OF 5?
f TURBULENCE^*
'EFFECT OF
TURBULENCE'
X.COAL CONSUMPTION
V
024 6 8 10 12 14 16 18 20 22 24
CLOCK TIME
FIGURE 2-3. Causes of Cyclical Diurnal Smoke Vari-
ations.16 (This figure shows causes of changes in
the diurnal airborne particulate concentration in
an urban location.)
2.0
I
§1.6
I
CM
31.0
5
in
O
0.5
TOTAL INSOLUBLE MATTER
TOTAL DISSOLVED MATTER
OC > Z J O fc H > O
FIGURE 2-4. Yearly Cycle (Averaged Over Six
Years) of Deposited Pollutants. (This figure illus-
trates the variation of amount of pollutants de-
posited at Leicester town hall averaged over the
six years ending March 1939, and shows the
greater mean concentration in winter as compared
with summer.)
jacent countryside and the variations of par-
ticle concentrations in the atmosphere.22-24
The influence of cities on precipitation is
complex; however, there is a general tend-
ency for urban factors to increase precipita-
tion.23 These factors, not necessarily in order
of importance, are:
1. water vapor addition from combus-
tion sources and processes;
2. thermal updrafts from local heating;
3. updrafts from increased friction tur-
bulence;
4. added condensation nuclei leading to
more ready cloud formation; and,
5. added nuclei which may act as freez-
ing nuclei for super-cooled cloud par-
ticles.
Landsberg 23 cites as evidence the gradual
increase of rainfall which followed the
growth of Tulsa, Oklahoma, from a village
to a city in five decades and the concomitant
increase in particle concentrations. A study
by Kline and Brier 25 in metropolitan Wash-
ington, D.C., indicates that there is a con-
siderably higher level of freezing nuclei in
the metropolitan area than there is in the ad-
jacent countryside.
Ashworth 24 first suggested the correlation
between the weekly cycle of smoke in indus-
trial areas and that of precipitation. Fred-
erick,26 in a more recent analysis, showed a
definite minimum Sunday rainfall for a ten-
year period in Louisville, Pittsburgh, and
Buffalo.23'26 Precipitation occurred in these
less often on Sundays than on other days
of the week, and the average rainfall was
less for Sundays than for weekdays. A
strong city influence is also suggested in the
snow patterns in Toronto.27
An interesting and significant increase in
precipitation has been observed at La Porte,
Indiana, since 1925. La Porte is 30 miles
east of the large complex of heavy indus-
tries in the metropolitan Chicago area.
Changnon28 compared precipitation at La
Porte, Valparaiso, and South Bend, Indiana,
with a five-year moving average of the num-
ber of smoky and hazy days in Chicago (Fig-
ure 2-5). The temporal distribution of the
smoke-haze days after 1930 is rather similar
to the La Porte curve. A notable increase in
41
-------
smoke-haze days began in 1935, becoming
more marked after 1940, coincident with the
sharp increase in the La Porte precipitation
curve. The reduction in the frequency of
smoke-haze days after the peak reached in
1947 also generally matches the decline of
the La Porte curve since 1947.28
Stout29 has shown that the shape of the
time-series curve for La Porte precipitation
also generally matched a time-series curve
for annual steel production in the Chicago
industrial complex. Between 1905 and 1965,
peaks in steel production, which occurred
when production in most other industries
was also high, were all associated with high
points in the La Porte precipitation curve.
The effect of industrial pollution on pre-
cipitation has also been studied by Telford.30
He found that smoke from steel furnaces was
a prolific source of freezing nuclei, increas-
ing counts by a factor of 50 over those in
nearby clean air. He concluded that there
should be increased rainfall downwind of
such installations.
E. RELATION TO WORLDWIDE
CLIMATIC CHANGE
Theoretical considerations and empirical
evidence indicate that atmospheric turbidity,
itself a function of aerosol concentration, is
an important factor in the heat balance of
the earth-atmosphere system. The observed
increase in turbidity over the past few dec-
ades may play a role in the reported decrease
in worldwide air temperature since 1940 by
increasing the planetary albedo.7-31
300
270
o
z
o
(L
O
240
210
180
150
CHICAGO
SMOKE HAZE
DAYS
OBSERVER
CHANGES AT
LA PORTE
1800
1400
1000
600
o
UJ
N
X
Q
2
<
UJ
C/J
I
_
O
DC
HI
CQ
5
200
1910
1920
1930
1940
1950
1960
ENDING YEAR OF 5-YEAR MOVING AVERAGE
FIGURE 2-5. Precipitation Values at Selected Indiana Stations and Smoke-Haze Days at Chicago. (This figure
shows the way in which precipitation trends at La Porte follow the haze changes in Chicago. The results are
plotted as five-year moving averages.)
42
-------
Angstrom estimated roughly that a change
in the albedo from 0.40 to 0.41 corresponds
to a change in the mean temperature of the
earth-atmospheric system of close to 1° C.32
Humphreys 33 made similar calculations with
roughly the same results, and also showed
that the interception of outgoing radiation
by fine atmospheric dusts is wholly negligible
in comparison with the interception of in-
coming solar radiation. Temporal and spa-
tial changes in the atmospheric turbidity of
100 percent, corresponding to albedo changes
of 10 percent to 15 percent, from one day
to the next or from one locality to another,
are very commonplace.31 Even though these
figures may well overestimate the actual
changes brought about in atmospheric tem-
peratures, the course of atmospheric turbid-
ity over the earth is an important climatic
factor.
There are data available 31-34 from which
the trend in turbidity during1 the past cen-
tury can be estimated. Angstrom gave 0.098
as the value of the mean annual turbidity at
Washington, B.C. (1903 to 1907)," and
0.024 as the value at the Davos Observatory,
Switzerland (1914 to 1926). The values for
Washington were determined from data on
solar transmission (by wavelength) pub-
lished by the Smithsonian Institution; those
for Davos were from data attributed to Lind-
holm on dust absorption. In 1962, deter-
minations of the atmospheric turbidity were
begun at the Continuous Air Monitoring
Program station 31-35 of the Public Health
Service, near the Smithsonian Institution;
the mean annual turbidity recorded for 1962
to 1966 was 0.154,35 a 57 percent increase
over the 1903 to 1907 values. From 1957
to 1959, determinations of atmospheric tur-
bidity were again made for Davos by Valko 3G
and were given as 0.043, a 70 percent in-
crease.
When the scattering theory with a Junge
distribution of particle size4 is used, the
values of turbidity change imply an increase
in the average annual number of aerosol par-
ticles, in the range of O.l/i to 1/j. radius, of
2.8xlOTcm2 and 0.95xlOT/cm2 over Wash-
ington and Davos respectively, during the
periods shown. Nearly two-thirds of the
Washington increase might be attributed to
the increased population and urbanization of
the District since the turn of the century.
A significant remainder, however, as judged
by the Davos increase, may be indicative of
a much more general buildup of atmospheric
aerosol.
When the above facts are put together,
they indicate that for Washington, D.C., dur-
ing the period 1903 to 1966, there has been
a possible decrease of nearly 3 percent in
the total available solar energy at ground
level and a possible increase in the average
annual number of aerosol particles of
2.8 X 107cm-'. The net effect of this apparent
secular increase in turbidity (which from
the Davos, Switzerland, and other evidence 34
appears likely to be worldwide) is probably
to increase the mean albedo of the planet
and reduce the mean temperature of the
earth-atmosphere system.
The increase in atmospheric turbidity
consequent upon volcanic eruptions may
have temporary effects on atmospheric tem-
peratures. Mitchell37 concluded that tem-
peratures over large areas of the world may
be depressed by 0.5° F or more in the first
or second year following an unusually violent
eruption. However, McCormick and Lud-
wig 31 suggest that the effects of man's pol-
lution of his environment are increasing
steadily along with the world population.
The emission of long-lived particles, keeping
pace with the accelerated worldwide produc-
tion of CO;., may well be leading to the de-
crease in world air temperature in spite of
the apparent buildup of CQ2.™
F. SUMMARY
Atmospheric particles scatter and absorb
light from the sun, thus reducing the visible
radiation available to cities and the solar
radiation that reaches the earth. The gloom
due to reduced illumination in urban areas
creates a need for artificial lighting in offices,
factories, and homes and produces related"
economic stresses. The average year-round
illumination (i.e., the portion of the spec-
trum that is visible to the eye) may be re-
duced by one-third or more in some cities.
Daylight illumination in the center of Lon-
don, for example, was found to be 20 per-
cent less than that found at a slightly less-
43
-------
polluted part of the city quite near the center.
Part of the sunlight reaching the earth
comes from the direct beam and part from
that scattered from the rest of the sky. The
total solar energy reaching the earth is the
sum of both the direct and the scattered ra-
diation. In general, cities receive 15 per-
cent to 20 percent less total solar radiation
than do rural environments, although the net
reduction may be considerably greater under
some circumstances. For a typical urban
area in the United States, with a geometric
mean annual concentration of roughly 100
/ig/m3, the total sunlight is reduced approxi-
mately 5 percent for every doubling of par-
ticle concentration. This effect is more pro-
nounced on the ultraviolet portions of the
spectrum.
Diurnal, weekly, and yearly cycles of both
suspended particulates and dustfall particles
correspond closely to man's pattern of activi-
ties and his combustion requirements. There
are usually two daily peaks, greater midweek
concentrations compared with Sundays, and
greater mean concentrations in autumn and
winter than in spring and summer. The sea-
sonal variations are due largely to the use
of coal and heavy fuel oil for heating pur-
poses. Solar radiation attenuation patterns
also show weekly and seasonal variations.
On weekdays, the attenuation is slightly
more than on Sundays, and the losses in in-
tensity of the direct beam during its passage
through an atmosphere polluted by smoke
may become as high as one-third in the sum-
mer and two-thirds in the winter. Even vari-
ations from year to year have been noted;
for example, levels of total solar radiation
measured in various cities were significantly
higher in 1932 than in the prior year, un-
doubtedly because of the decline in manu-
facturing and industrial activity brought
about by the depression. Reductions in the
intensity of solar radiation or changes in its
spectral distribution have significance for
the photosynthesis of vegetation, the distri-
bution of plants and animals on the earth,
the weathering of natural and manmade ma-
terials, and man's aesthetic enjoyment and
physical well-being.
The increased emission of fine particles
into the atmosphere also may cause changes
in the delicate heat balance of the earth-
atmosphere system, thus altering worldwide
climatic conditions. The rise in atmospheric
turbidity increases the planetary reflectivity,
or albedo, and reduces the solar energy avail-
able to maintain surface temperatures. This
phenomenon may be responsible for the re-
ported decrease in worldwide temperature
since the 1940's. Comparisons at different
sites over the world covering periods as long
as fifty years suggest that a general world-
wide rise in turbidity may be taking place.
This may well be indicative of a gradual
buildup of worldwide background levels of
suspended particulates. The increasing lev-
els of atmospheric carbon dioxide resulting
from man's combustion of fuels probably
exerts an opposite effect on worldwide tem-
peratures, but the emission of long-lived par-
ticles to the air may gradually depress world
air temperature despite the apparent build-
up of carbon dioxide.
Some of the particles introduced into the
atmosphere by man's activities also can af-
fect the weather by serving as condensation
nuclei that influence the formation of clouds,
rain, and snow. The large airborne particles
generated in metropolitan areas serve as a
base for the condensation of moisture and
lead to the rapid formation of rain droplets
or ice crystals. Patterns of precipitation
over cities and the adjacent countryside have
shown a correlation with particle concentra-
tions in the atmosphere. Some cities display
a definite minimum rainfall on Sundays,
when participate levels are usually lowest,
and records over several decades reveal that
rainfall levels may increase with the con-
comitant rise in particulate levels that gen-
erally accompanies urban growth. In addi-
tion, long-term changes in the frequency of
smoke-haze days in one city may affect rain-
fall levels in a nearby downwind city.
Thus airborne particles can, through a
number of mechanisms, influence man's sur-
roundings and have considerable impact on
weather and climatic conditions.
G. REFERENCES
1. Sheppard, P. A. "The Effect of Pollution on
Radiation in the Atmosphere." Intern. J. Air
Pollution, Vol. 1, pp. 31-43, 1958.
44
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2. McCormick, R. A. and Baulch, D. M. "The Vari- 17.
ation with Height of the Dust Loading over a
City as Determined from the Atmospheric Tur-
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pp. 492-496, 1962. 18.
3. Sheleikhovskii, G. V. "Smoke Pollution of
Towns." Akademiya Kommunal'nogo Khzyaistva
im. K. D. Pamfilova. [Academy of Municipal 19.
Economy im. K. D. Pamfilova.] IzdatePstvo Min-
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"Klima und Bioklima von Wien." Wetter und 30.
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14. Kenrick, G. W. and Ortiz, H. "Measurements
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15. Meetham, A. R. "Atmospheric Pollution in 32.
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16. Meetham, A. R. "Atmospheric Pollution: Its
Origin and Prevention." Pergamon Press, New
York, 1961.
Mateer, C. L. "Note on the Effect of the Weekly
Cycle of Air Pollution on Solar Radiation at
Toronto." Intern. J. Air Water Pollution, Vol.
4, pp. 52-54, 1961.
Hand, I. F. "Solar Radiation Measurements
During December 1932." Monthly Weather Rev.,
Vol. 60, pp. 256-257, 1932.
Neuberger, H. "Condensation Nuclei: Their Sig-
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Vol. 70, pp. 221-225, 1948.
Landsberg, H. "Atmospheric Condensation Nu-
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Giner, R. and Hess, V. F. "Studie uber die Ver-
teilung der Aerosole in der Luft von Innsbruk
und Umgebung." Gerlands Beitr. Geophys., Vol.
50, pp. 22-43, 1937.
Georgii, H. W. "Probleme und Stand der Erfor-
schung des Atmospharischen Aerosols." Ber.
Deutsche Wetterdienste., Vol. 7, pp. 44-52, 1959.
Landsberg, H. "City Air—Better or Worse."
In: Air Over Cities Symposium, U.S. Dept. of
Health, Education, and Welfare, Robert A. Taft
Sanitary Engineering Center, Cincinnati, Ohio,
Technical Report A62-5, 1962, pp. 1-22.
Ashworth, J. R. "The Influence of Smoke and
Hot Gases from Factory Chimneys on Rainfall."
Quart. J. Roy. Meteorol. Soc., Vol. 55, pp. 341-
350, 1929.
Kline, D. B. and Brier, G. W. "Some Experi-
ences on the Measurement of Natural Ice Nu-
clei." Monthly Weather Rev.. Vol. 89, pp. 263-
272, 1961.
Frederick, R. H. Personal communication. U.S.
Weather Bureau.
Potter, J. G. "Changes in Seasonal Snowfall in
Cities." Canadian Geographer, Vol. 5, pp. 37-42,
1961.
Changnon, S. A. Jr. "The La Porte Weather
Anomaly, Fact or Fiction." Bull. Am. Meteorol.
Soc., Vol. 49, pp. 4-11, 1968.
Stout, G. E. "Some Observations of Cloud Ini-
tiation in Industrial Areas." In: Air Over Cities
Symposium, U.S. Dept. of Health, Education,
and Welfare, Robert A. Taft Sanitary Engineer-
ing Center, Cincinnati, Ohio, Technical Report
A62-5, 1962, pp. 147-153.
Telford, J. W. "Freezing Nuclei from Industrial
Processes." J. Meteorol., Vol. 17, pp. 676-679,
1960.
McCormick, R. A. and Ludwig, J. H. "Climate
Modification by Atmospheric Aerosols." Science,
Vol. 156, pp. 1358-1359, 1967.
Angstrom, A. K. "Atmospheric Turbidity, Glo-
bal Illuminators and Planetary Albedo of the
Earth." Tellus, Vol. 14, pp. 435-450, 1962.
Humphreys, W. J. "Volcanic Dust and Other
Factors in the Production of Climatic Changes
and their Possible Relation to Ice Ages." Bull.
Mount. Weather Observatory, Vol. 6, pp. 1-34,
1914.
45
-------
34. Peterson, J. T. and Bryson, R. A. "Atmospheric
Aerosols: Increased Concentrations During the
Last Decade." Science, Vol. 162, pp. 120-121,
1968.
35. "Atmospheric Turbidity Report." U.S. Dept. of
Health, Education, and Welfare, National Cen-
ter for Air Pollution Control, Cincinnati, Ohio.
(Quarterly)
36. Valko, P. "Untersuchung iiber die vertikale
Triibungsschichtung der Atmosphare." Arch.
Meteorol. Geophys. Bioklimatol., Ser. B, Vol. 11,
pp. 143-210, 1961.
37. Mitchell, J. M., Jr. "Recent Secular Changes in
Global Temperatures." Ann. N.Y. Acad. Sci.,
Vol. 95, pp. 235-250, 1961.
38. "Restoring the Quality of Our Environment."
Report of the Environmental Pollution Panel,
President's Science Advisory Committee, The
White House, Washington, D.C., November 1965,
pp. 111-131.
46
-------
Chapter 3
EFFECTS OF ATMOSPHERIC PARTICULATE
MATTER ON VISIBILITY
-------
Table of Contents
Page
A. INTRODUCTION 51
B. IMPORTANCE OF ATMOSPHERIC AEROSOLS TO THE GEN-
ERAL OPTICAL PROBLEM 51
C. PHYSICAL RELATIONSHIPS BETWEEN VISIBILITY AND PAR-
TICLE CONCENTRATION . 52
D. COMPLICATIONS AND LIMITATIONS IN THE VISIBILITY
PROBLEM 53
1. Smoke Plumes . 53
2. Natural Aerosols and Hazes . 53
3. Fogs 54
E. THE LOW-HUMIDITY, WELL-AGED HAZE . . 54
1. Size Distribution . ... 54
2. Mie Solutions ... 54
3. Dependence of Extinction of Particle Size for the Atmospheric Case
4. The Mass-Light Scattering Relationship . 55
F. DETERMINATION OF WELL-DEFINED CASES OF MASS-
VISIBILITY RELATIONSHIPS . . 58
G. METHODS FOR DETERMINING LIGHT SCATTERING COEFI-
CIENT-MASS CONCENTRATION RELATIONSHIP ... 59
H. SUMMARY .. 60
I. REFERENCES . ... 61
List of Figures
Figure
3—1 Four Typical Measured Size Distributions of Atmospheric Suspended
Particles Together with the Corresponding Visibilities 54
3-2 The Relation of Scattering Cross-Section to Particle Size for Parti-
cles of Three Different Refractive Indices 55
3-3 Cross Section Curve for Typical Atmospheric Size Distribution . 55
3-4 The Dependence of Scattering Coefficient (m-1) on Volume of Aero-
sol Particles (/*3/cm3) Calculated from Measured Size Distributions 56
3-5 Measured Dependence of Mass of Aerosol Particles per Volume (/tig/
m3) on the Light Scattering Coefficient (nr1) in Seattle, November-
December 1966 56
3-6 Histogram of Equivalent Visual Range-Mass Concentration Product
at Several Locations . ... 57
3-7 Relation Between Visual Range and the Mass Concentration 57
3-8 Three Horizontal Profiles through the City of Seattle Taken under
Differing Meteorological Conditions . . 59
48
-------
List of Tables
Table Pa<>e
3-1 Relation Between Equivalent Visual Range and Particle Concentra-
tion . . 57
3-2 The Relative Humidity at which Phase Change Occurs in Some De-
liquescent Aerosols . 59
49
-------
-------
Chapter 3
EFFECTS OF ATMOSPHERIC PARTICULATE MATTER ON VISIBILITY
A. INTRODUCTION
One of the dramatic effects of air pollu-
tion is a degradation of the visibility. Visi-
bility in the atmosphere is reduced by two
optical effects which air molecules and aero-
sol particles have upon visible radiation. One
is the attenuation by the molecules and par-
ticles of the light passing from object to ob-
server. It is the result both of absorption
of light and of the scattering of light out of
the incident beam. The light received from
the object and that received from its back-
ground are diminished by this attenuation,
and the difference between the two (con-
trast) is consequently diminished with the
result that the eye's ability to distinguish the
object from its background is reduced. The
other optical effect that degrades the contrast
between object and background is the illumi-
nation of the intervening air which results
when sunlight is scattered into the line of
sight by the molecules and particles in the
line of sight. It is a common observation
that dark objects become progressively
lighter in shade as they become more distant.
The most distant mountain that one can dis-
tinguish typically is almost as light or bright
as its sky background.
In those cases where a clear-cut relation-
ship can be shown to exist between visibility
and the mass of suspended particles per vol-
ume of air (mass concentration), it is pos-
sible to use some of the meteorological visi-
bility records to infer the amount of pollu-
tion in past years as well as to study trends.
In fact, many such studies have been made
even without a substantive knowledge of the
relationship. Holzworth 1 used existing visi-
bility data both as an indication of the
amount of pollution for comparison of an
urban (Columbus, Ohio) area with a rural
area, and for the qualitative inference of
trends of both increasing and decreasing
amounts of smoke or other atmospheric aero-
sol. Robinson - also discussed the use of me-
teorological visibility records and their
interpretation. Both Holzworth 1 and Robin-
son - demonstrated that visibility degrada-
tion can be associated with air pollution.
Neither, however, developed the sort of cor-
relation between mass of suspended particu-
late matter per volume of air and visibility
that is needed for air quality criteria. Rob-
inson indicated doubt in the existence of a
generally applicable relationship between
mass concentration and visibility. This
doubt was based on experimental results as
well as on the complexity of the problem.
Recent experimental and theoretical ad-
vances make possible some useful conclu-
sions, and this chapter will define a simple
relationship between mass of suspended par-
ticles and visibility, specify the circum-
stances under which it can be expected to be
reliable, and describe the conditions which
are too complex for this simple treatment.
In the United States, the words visibility
and visual range are usually used synony-
mously to mean the distance at which it is
just possible to perceive an object against
the horizon sky. Middleton3 reports that
the originator of both terms intended that
only visual range be considered as a distance,
while visibility should convey a more quali-
tative judgment about the clearness of see-
ing. In this chapter, however, the terms visi-
bility and visual range will be used inter-
changeably to mean a distance.
B. IMPORTANCE OF ATMOSPHERIC
AEROSOLS TO THE GENERAL
OPTICAL PROBLEM
Decreased visibility obviously interferes
with certain important human activities,
51
-------
such as the safe operation of aircraft and
automobiles and the enjoyment of scenic
vistas. The effect of decreased visibility on
the large-scale operations of commercial air-
craft in metropolitan areas is a problem of
growing concern. The Federal Air Regula-
tions of 19674 (paragraphs 91.105 and
91.107) prescribe limitations on aircraft op-
eration that become increasingly severe as
visibility decreases below five miles. Most re-
strictions are invoked when the visibility is
below three miles. In areas with a high den-
sity of aircraft traffic, visibilities much below
five miles tend to slow down operations by
maintaining larger separations between air-
craft. Even though most commercial air-
planes always fly under Instrument Flight
Rules rather than Visual Flight Rules, good
visibility increases both the safety and per-
mitted traffic density. Light airplane opera-
tions are limited even more severely when
visibility is less than three miles, because of
their limited instrument flight capability.
A 1963 report by the Civil Aeronautics
Board to the Committee on Public Works,
U.S. Senate,5 states that records of both au-
tomobile and aircraft accidents show cases
where poor visibility due to smoke and air
pollution was an important causal factor.
Evidence presented at Federal air pollution
abatement conferences e-7 shows the exist-
ence of air pollution that curtails visibility,
endangering the safety of people traveling
by both land and air, and in addition, causing
inconvenience and economic loss to the pub-
lic and to transportation companies due to
disruption of traffic schedules.
C. PHYSICAL RELATIONSHIPS
BETWEEN VISIBILITY AND
PARTICLE CONCENTRATION
Many derivations of visibility theory have
been published. Although Robinson's2 ap-
proach is directed towards the air pollution
problem, Middleton's 3 book presents a more
complete view of the problem of atmospheric
clarity.
For the simplest case of attenuation of a
light beam along its path, the intensity, I,
decreases by an increment dl over the in-
crement of path dx. The relationship be-
tween intensity and distance is:
dl
or, in integrated form,
(3-1)
(3-2)
abs-gas'
where b is the extinction coefficient assumed
to be constant over x, and I0 represents the
intensity of light at x = 0.
The extinction coefficient, b, is the sum of
four terms:
1. the scattering coefficient of the air mole-
cules, b^ . . , ;
Rayleigh
2. the scattering coefficient of particles or
aerosol, b , :
scat
3. the light absorption by gases, b
and,
4. the light absorption by the aerosol, b
abs-aerosol.
Of these four, the scattering due to aerosol
is usually assumed to dominate in haze.2 The
process of scattering amounts to the removal
of light from the original beam and its redis-
tribution in different directions. Scattering
thus differs from absorption in which the
light energy is lost to the absorber; in scatter-
ing, the light energy is only spatially redis-
tributed. Nonetheless, this removal of light
from the beam (or line of viewing) does re-
sult in extinction. It suffices to state only the
final result in equation 3-2 for the usual
assumption of 2% contrast threshdld for an
"average" human eye.2-3
3.9
b
scat
(3-3)
Here, Lv is the visual range in meters and
b is, as before, the extinction coefficient per
meter along the path of sight for the case of
a black object. If b is determined at a point
without knowledge of the entire sight path,
then Lv is "equivalent visual range," i.e., the
distance one could see if the extinction coeffi-
cient were constant along the sight path. A
discussion of the dependence of extinction
coefficient on the amount of atmospheric
aerosol follows in Section F.
52
-------
"Visual quality" as perceived by even the
well-trained observer is not so easily describ-
ed. Among the complications is the fact that
particles responsible for urban haze scatter
more light in a direction close to that of the
original beam (so-called forward-scatter)
and less light in a backward direction. Thus,
the same haze may appear to be much more
dense when looking toward the sun and less
dense when looking away from the sun.
Besides this directional factor, there is also
a wavelength (or color) dependence. Ang-
strom,8 Junge,9 and others have shown that
the extinction coefficient of hazes in general
is inversely proportional to a power of wave-
length:
b = —
Aa
(3-4)
where a has measured values of around 1.0 to
1.5. This relation indicates that blue light (of
shorter wavelengths) will be scattered to a
greater degree than red light (of longer
wavelengths). It is for this reason that the"
sun's disc, when observed through a haze that
is dense enough to permit such viewing, ap-
pears red, orange or even brown though light
absorption is not necessarily occurring.
D. COMPLICATIONS AND LIMITATIONS
IN THE VISIBILITY PROBLEM
1. Smoke Plumes
Conner and Hodkinson,10 in tests on the
optical properties of well-controlled experi-
mental smoke, found that visual effects are
not inherent properties of the plumes but
vary with the background of the plume and
with illuminating and viewing conditions.
Variation was much greater with white
plumes than with black. Tests conducted with
trained smoke inspectors showed that their
evaluations of non-black smoke plumes were
significantly influenced by these variations.
At least two real difficulties exist in making
any generalizations about visual aspects of
smoke plumes. First, it is not possible to de-
termine the mass emitted per unit time from
a smokestack solely on the basis of visually
perceived light scatter or absorption. The
mass per unit time emitted from the stack
and not the appearance or optical properties
of the plume is pertinent to the eventual air
composition, even though appearance may be
aesthetically objectionable.
Secondly, although many meteorological
mixing equations have been proposed, they
cannot describe individual eddies of smoke as
the plume disintegrates. The equations were
meant for describing averages and not an
instantaneous property such as the extinction
of light in some particular eddy of smoke as
determined by eye, perhaps with the aid of a
Ringelmann Chart.
Because of these problems, the topics of
plumes and plume optics are discussed only
briefly in this chapter, and the presentation
is concerned primarily with the aerosol pro-
duced after the initial meteorological mixing
of the plume has occurred. The reader is re-
ferred for further information on plume op-
tics to the study by Conner and Hodkinson.10
The Ringelmann number may provide an
objective measurement of public sentiment
regarding the disagreeable appearance of
smoke plumes, although aesthetic aspects are
difficult to quantify. Robinson " shows the as-
sumptions and size distribution information
that are necessary for relating plume opacity
to the aerosol content of smoke.
The difficulties inherent in visual evalua-
tion of smoke plumes do not eliminate the
possibility of using such observations as an
aid in controlling air pollution. In principle,
the Ringelmann Chart should be useful in
estimating the obscuring of vision by plumes
and in setting limits to control the visibility
degradation downwind from a source of par-
ticulate matter. In practice, however, the
problem is extremely complex and requires
extensive study to develop better techniques
for measuring the contribution of individual
plumes to visibility problems.
2. Natural Aerosols and Hazes
The general problem of natural particu-
late matter—from whatever source—must
be considered. The oceans produce salt parti-
cles, trees produce terpenes that may result
in organic particles,11 forest fires make
smoke, and so on. Man has little hope of con-
trolling the quality of air that enters the
urban areas from uninhabited lands. None-
theless, these low-humidity aerosols some-
53
-------
times cause dramatic reduction in the visual
range. In order to properly evaluate the im-
portance of natural aerosols, the visibility
of the air mass should be determined before
it enters a populated area.
3. Fogs
When the relative humidity exceeds ap-
proximately 70 percent, many types of parti-
cles exhibit deliquescent behavior and grow
into fog droplets. Natural particles such as
sodium chloride from the sea as well as many
products of human activity can thus act as
condensation nuclei (Chapter 2). The prop-
erty of deliquescence and the relative humid-
ity at which rapid and large change in parti-
cle size occurs are both very dependent on
the chemical composition and original size
of the particles. As a result, unless the chem-
ical composition as a function of particle size
is known for the aerosol, very little can be
said about the relationship between visibil-
ity in even "thin" fog and the amount of
material present as pollutant.12
Because little deliquescence occurs below
70 percent relative humidity, the relation-
ships to be presented here will be limited to
the range of humidity from 0 percent to 70
percent. In cases of higher humidity, it is
possible to decrease the relative humidity of
the air by heating it for optical evaluation
of the amount of particulate matter, as de-
scribed by Charlson et ai.13 This humidity
limitation has already been adopted in Cal-
ifornia.14
E. THE LOW-HUMIDITY, WELL-AGED
HAZE
1. Size Distribution
Recent advances in both theory and tech-
nology have resulted in a simplification of
the description of well-aged aerosols. Junge,9
Friedlander,15 Whitby,16 and others" have
shown that aerosols in the lowest region of
the atmosphere (troposphere), whether over
urban areas or not, tend to have similar size
distributions. Figure 3-1 shows several typi-
cal size distributions to illustrate this fea-
ture.
If it is assumed that this recurring size
distribution exists in general, then it is pos-
3.
Z
cc
LU
z
w10s
2
0
y
I-
<102
u.
O
IT
Z
3-4 miles haze - low wind speed-
high pressure over area. Seattle
4-5 miles haze - deep low pressure
area southwest of area. Seattle
6-7 miles-rain showers and cumulus
clouds - tops near 10,000 feet.
Seattle
v __ 10-20 miles (ocean) - high pressure
over area. Washington seacoast
.01
0.1
PARTICLE RADIUS,
1.0
FIGURE 3-1. Four Typical Measured Size Distribu-
tions of Atmospheric Suspended Particles To-
gether with the Corresponding Visibilities.1* (The
figure shows that aerosols in the lowest region of
the atmosphere (the troposphere) tend always to
have similar size distributions.)
sible to relate the optical properties of the
haze to the amount or mass concentration of
material present. This generalization may
not apply to freshly-formed smoke. Brief
guidelines for determining when the size
distribution has become sufficiently well-
defined will be given later.
2. Mie Solutions
As mentioned earlier, another important
assumption which is usually made is that, of
the four extinction components, light scatter-
ing by aerosols dominates. Current research
indicates that this is probably a justifiable
assumption.13 Figure 3-2 shows typical scat-
tering cross sections for green light as a
function of particle size for aerosol particles
important in haze, computed via the theory
of Gustav Mie.18 For some particle sizes, dif-
ferences in the scattering coefficient of a fac-
tor of three exist between the two refractive
indices which span the realistic range for
the atmospheric case. However, Pueschel and
54
-------
10-7F
m= 1.60
___m = 1.33
m= 1.59-0.66i
Sot r3
lio-6
PARTICLE RADIUS, JU
FIGURE 3-2. The Relation of Scattering Cross-Sec-
tion to Particle Size for Particles of Three Dif-
ferent Refractive Indices.13 (The figure shows that
the scattering cross-section of atmospheric par-
ticles varies roughly as the cube of their radius
within the range 0.1^ to 1.0^. The range of re-
fractive indices, 1.33 to 1.6, for which the propor-
tionality holds includes most materials found in
atmospheric aerosols.)
Noll19 conclude that the extinction coefficient
of aerosols in the troposphere is nearly inde-
pendent of the refractive index of the parti-
cles if the size distribution is close to those
described in Figure 3-1.
3. Dependence of Extinction on Particle
Size for the Atmospheric Case
If the data in Figures 3-1 and 3-2 are
broken down into narrow radius intervals
(e.g., 0.01/i), and a calculation performed to
yield the extinction coefficient for each ra-
dius interval, the particle size dependence of
atmospheric extinction of green light is re-
vealed. Figure 3-3 shows the results for a
typical size distribution of spherical parti-
cles having a refractive index of 1.5.
In general, this procedure shows that a
narrow range of particle sizes, usually from
O.lfjL to I/* radius controls the extinction coef-
ficient and therefore the visibility. If the
values of the extinction coefficient for each
radius interval are then summed, the total
cc
111
E>
Q
CC
IJ10-'
5
cc
O
u.
H
UJ
O
LU
O
O
(3
CC
HI
E«
u
i-S
10'6 cm'1
0.1 0.2 0.3 0.4 0.5
PARTICLE RADIUS,(/I)
0.6 0.7
FIGURE 3-3. Cross Section Curve for a Typical At-
mospheric Size Distribution.19 (The figure shows
the particle size dependence of atmospheric ex-
tinction obtained by breaking down the data of
Figures 3-1 and 3-2 into 0.01^-radius intervals,
to yield the extinction coefficient of each radius
interval.)
extinction coefficient, due to scatter, bscat, is
obtained.
t. The Mass-Light Scattering Relationship
It is also possible to calculate the volume
of particulate matter per unit volume of air
(i.e., in cubic microns of aerosol per cubic
centimeter of air). The familiar quantity of
areosol mass concentration (yug/m3) is pro-
portional to this volume ratio via the particle
density. Figure 3-4 shows the calculated rela-
tionship of aerosol volume (fi3/cm3) to scat-
tering coefficient per meter (for green light
[5500A] and for a refractive index of 1.6)
based on 32 individual measured size distri-
butions. Sixteen of these size distributions
used in Figure 3-4 were measured in Seattle
under varying meteorological conditions. The
remaining 16 were obtained in the Austrian
Alps under conditions where, presumably,
55
-------
1000
°g300
_JJ
n
a.
ui 100
5
_l
o
> 30
_i
8
o
S 10
3
1 0
m \
E •
' SEATTLE, WASHINGTON »^*'
0
•«
r > '
-
O~O KALKALPEN, AUSTRIA
: o
7 0
_
1UUU
300
n
E
-^.
«100
2
O
H
< 30
cc
H
UJ
^ 10
O
o
§ 3
DC
111
**
-
•
•
r «fc v
F •'*• " *
-
9 ' V
-•
-
-
„
1 1 , , . 1 1 ,lll 1 1 1 1 ,1 .1
0.1 0.3 1.0 3 10 30 xlO"4 ""0.1 o.3 1.0 3 10 30 x 10"
LIGHT SCATTERING COEFFICIENT
FIGURE 3-4. The Dependence of Scattering Coeffi-
cient (w1) on Volume of Aerosol Particles
(///cm3) Calculated from Measured Size Distri-
butions.13 (The solid circles are based on Seattle,
Washington, data and the open circles on Kalkal-
pen, Austria, data.)
only natural aerosol was present. The im-
plication of these calculations is that the
volume, and thus the mass concentration of
well-aged aerosol, is approximately propor-
tional to the light scattering coefficient for
atmospheric aerosols originating naturally
or as the result of man's activity.13
It follows, therefore, that even though the
aerosol mass is distributed over perhaps two
or three decades of size, and light scatter is
caused by particles of one narrow size range,
a proportionality can exist between the num-
ber of particles scattering light and the total
mass concentration of particles. Constant
shape of the size distribution here implies
that for all radius intervals, the number of
particles in an interval is proportional to the
number in the corresponding interval in a
reference size distribution.
Figure 3-5 shows data obtained by an in-
tegrating nephelometer 1S for a wavelength
of 5000 A confirming this calculated depend-
ence. The relationship can be summarized as
follows:
mass (/ig/m3)~3xl05 bscat/m. (3-5)
Figure 3-6 shows data like those of Figure
LIGHT SCATTERING COEFFICIENT b^^/m
FIGURE 3-5. Measured Dependence of Mass of Aero-
sol Particles per Volume (/jg/m3) on the Light
Scattering Coefficient (wr1) in Seattle, November-
December 1966.13
3-5 plotted in a different fashion to illustrate
their distribution.20 From equations 3-3 and
3-5, the product of equivalent visual range
and mass concentration (Lvxconc) can be
obtained.
Since
3.9
(3-3)
multiplying both sides of the equation by
concentration gives
3.9 X cone
LTxconc = (3-3a)
bgcat
The units on both sides of this equation are
mass per area (e.g., /xg/m2). If we use the
particular proportionality in equation 3-5,
then:
Lv x cone-1.2 x 106 /.g/m2 = 1.2 g/m2. (3-6)
This product has a simple physical signifi-
cance: it is the mass of material in a column
of length Lv and one square meter in cross
section. In other words, it is the amount of
material per square meter between the ob-
server and a point at the limit of visibility.
Each point of Figure 3-5 can be used to form
this number since each pair of values of mass
concentration and scattering coefficient can
56
-------
35
30
25
20
t5
10
5-
0
0 15,
u.
O
E 10
UJ
CO
I 5
z
0
5'
w
UJ
0
10
5
0
A. All 238 cases.
B. New York City, 62 cases.
C. San Jose, California,
48 cases.
D. Seattle, Washington
Area. 45 cases
E. Seattle, Washington, high
volume air sampler data.
0.8 1.6 2.4 3.2
Lv x MASS, grams / m'
FIGURE 3-6. Histogram of Equivalent Visual Range-
Mass Concentration Product at Several Loca-
tions.1* (The figure shows the number of cases
with a given range of values of the product of
mass and equivalent visual range for data at vari-
ous locations studied. This product represents the
mass required to determine the visibility in a col-
ume one square meter in cross section along the
light path.)
be used to obtain a different proportionality
of the sort shown in equation 3-5. Figure 3-6
consists of histograms showing the number
of occurrences for different values of the
quantity Lv x cone found at various locations.
Here, since the modal value is about 1.2
g/m2, one can write:
LTxconc~1.2:j;2 (g/m2)
to include virtually all cases.
(3-7)
100:
J ioj
3
1
i To 160
MASS CONCENTRATION,
FIGURE 3-7. Relation Between Visual Range and
Mass Concentration.22 (This figure shows the in-
verse proportionality between visual range and
mass concentration described by equations 3-7 and
3-8.)
Equation 3-5 can also be rewritten to include
these upper and lower limits:
mass (/*g/m3) ~
X 105 b9Cat/m. (3-8)
Data in essential agreement with this result
have also been obtained recently by visual
methods in Oakland, California.21 As the
data indicate that equation 3-8 is applicable
in a wide variety of cases,20 and because
these locations seem to include a wide variety
of air pollution character, it is anticipated
that this generalization may be useful in
many urban areas. The relationship is shown
in Figure 3-7 and Table 3-1. 22 However, ex-
perimental verification of the mass-light ex-
tinction relationship is desirable for each
location in question.
Table 3-1.— RELATION BETWEEN EQUIVALENT
VISUAL RANGE AND PARTICLE CONCENTRA-
TIONS
Mass
concentra-
tion jug/m3
10«o
- 5
30^
100«oo
- 60
300^°°
-TBO
1000+10°°
Scattering Equivalent
coefficient visual
due to aerosol, range,
bscat/m km
0.3 X10-4
i.oxio-'
3.3X10-'
lo.oxio-1
33.0X10-'
120.0
40.0
12.0
4.0
1.2
Equivalent
visual
range,
miles
75.00
25.00
7.50
2.50
0.75
57
-------
The accuracy of equations 3-7 and 3-8
depends on many factors and assumptions.
This research area is an active one, and new
data are constantly being acquired. Improve-
ments in the understanding of these phe-
nomena and the accuracy of descriptions will
no doubt occur in the near future. However,
these values are known to be accurate to well
within one significant figure for the cases
measured, and their utility for criterion pur-
poses is therefore clear.
Photochemically produced aerosols, as well
as other organic aerosols, can be expected to
have similar visibility effects if their size
distribution remains reasonably constant.
Since the physical processes governing size
distribution are assumed to be largely in-
dependent of the chemical nature of the par-
ticles,13 the size distribution should be similar
to those shown in Figure 3-1. However, if
such particles are volatile or metastable to
oxidation as suggested by Goetz,23 the mass
determination may be difficult. Although vis-
ibility degradation is evident in photochem-
ical smog, experimentally determined size
distribution data are needed.
It can be seen from Figure 3-5 that the
practical unit of light scattering coefficient
for 5000 A wavelength is 10~4/m. The value
1 x 10-4/m represents fairly clean air with a
particle mass concentration of about 30
jug/m3, while 10 x 10~4/m represents more
polluted air (concentration about 300 /ig/
m3) . Of course, the reciprocal relationship
(equation 3-3) could be used in combination
with equation 3-5.
(Km)~1.2^xl03/conc
(3-9)
(See also Figure 3-7 and Table 3-1.) How-
ever, reciprocal relationships are harder to
visualize than are direct proportionalities,
and the extinction coefficient due to scatter
(or just scattering coefficient) itself can
serve as an index for particulate pollution.
It is interesting to compare the results of
equation 3-7 with Robinson's 2 calculation of
0.34 g/m2 for an oil aerosol in which all par-
ticles have the same 0.6/x diameter. Since this
estimate represents a case in which all the
particles are involved in the light scattering,
it is not surprising that a mass smaller than
that suggested by equation 3-7 is necessary
for determining the visibility. In the atmos-
phere, a large percentage of the mass of the
particulate matter is outside the size class
important for light scatter (see Figures 3-1
and 3-3) and a somewhat higher mass per
unit area is needed to determine the visibility.
F. DETERMINATION OF WELL-DEFINED
CASES OF MASS-VISIBILITY
RELATIONSHIPS
As discussed above, any generalization
about the visibility-particle (aerosol) con-
centration relationship is dependent on a
well-defined and nearly constant size distri-
bution. The following list summarizes the
cases in which equation 3-8 applies:
1. the relative humidity should be below
70 percent. (For a discussion of the
relationship between visibility and
concentrations of sulfur dioxide at
various relative humidities, see a
companion volume to this document,
Air Quality Criteria for Sulfur Ox-
ides.) Absolute humidity is relatively
unimportant since the interaction of
water vapor and hygroscopic aero-
sols depends mainly on relative hu-
midity. In the case of a particularly
hygroscopic aerosol, the 70 percent
figure may be unreliable. Table 3-2
shows a list of compounds and the
approximate humidity at which they
deliquesce. If such a substance is
present as a large percentage of the
total aerosol, even though the rest
of the following conditions may hold,
the applicability of equation 3-5
might be open to doubt.
2. the size distribution must be well-
established and close to the recurring
form discussed earlier. Little experi-
mental information is available on
the length of time required for vari-
ous types of fumes to attain a reason-
ably well-defined size distribution by
coagulation and sedimentation. Meas-
urement of this parameter is there-
fore desirable before any generaliza-
tions are made about visibility. The
58
-------
Table 3-2.—THE RELATIVE HUMIDITY AT WHICH
PHASE CHAIN UK UCCUKfe
CENT AEROSOLS.24
Substance
Sodium hydroxide
Calcium chloride
Sulfuric acid
Magnesium chloride
Sodium iodide
Magnesium nitrate
Sodium bromide
Potassium iodide
Sodium nitrate
Sodium chloride
Potassium bromide
Potassium chloride
Barium chloride
1JN SUMJi UJiLiHiUffiB-
Approximate
percent relative
humidity at
which phase
change occurs
at 25°C
7
29
35
33
38
53
58
69
74
75
80
84
90
g
Eo
o
b
. * -7
I— i
z
m
I 6
LL
LU
o 5
z
^ 4
m •»
<
8 3
H
O i
— • *
1
0
_
31 AUGUST 1967 K I
1000-1030 PDT \\ I
FOGGY I I I
LOWWINDSPEED / I /
/
/
•*N /
\ I
+'r \
\f\ \
A / \ '\ / ' \
/ \J "" \,' I \
/ 30 AUGUST 19671 l\
*J 1530-161 5 PDT I/ A^
" / HAZE V \ -
/ LOWWINDSPEED \
x 5 SEPTEMBER 196T~ ^v
* 1530-1630 PDT "*
STRONG SOUTH WIND— x
,'~\'\ 7 \x
*'"' *"" ^**-_
i i i i i i i i i
most important qualification appears
to be that the aerosol in question
must not be freshly formed as in a
smoke plume. Times of the order of
one hour may be adequate for the
establishment of a well-defined size
distribution from a combustion-pro-
duced fume.
3. if visual observations are used, the
line of sight cannot pass through
smoke plumes or freshly formed
clouds of fumes. As mentioned ear-
lier, the light extinction coefficient is
a spatial variable and thus the mass
inferred by visual methods repre-
sents an average over a large dis-
tance. If the optical quantity (i.e. ex-
tinction coefficient due to scatter) is
to be related to concentration meas-
urements made at one point in space,
then it should be determined at the
same point. To illustrate the possible
magnitude of the visibility variation,
Figure 3-8 shows the variation of
scattering coefficient measured with
an integrating nephelometer across
the city of Seattle on three days with
different meteorological conditions.
The results also emphasize the haz-
ards inherent in visual observations.25
20 15 10 5 0 5 10 15 20 25 30
N S
DISTANCE FROM UNIVERSITY HIGH BRIDGE, Km
FIGURE 3-8. Three Horizontal Profiles Through the
City of Seattle Taken Under Differing Meteorolog-
ical Conditions.35 (The figure illustrates the pos-
sible magnitude of variations in visibility.)
G. METHODS FOR DETERMINING LIGHT
SCATTERING COEFFICIENT-MASS
CONCENTRATION RELATIONSHIP
Methods for determining the extinction
coefficient and/or the visibility (as related
through equation 3-3) are not as well-es-
tablished as for many meteorological quan-
tities (e.g. wind, temperature) or for air
pollution quantities (dustfall, mass concen-
trations, etc.). Three basic approaches can
be differentiated:
1. the method of choice is an instantane-
ous point measurement of the ex-
tinction coefficient. The extinction co-
efficient due to scatter (which is as-
sumed to dominate) can be measured
with an integrating nephelometer
such as was used by Charlson
et al™> 25>26
2. the next most desirable methods in-
volve the measurement of total ex-
tinction coefficient using light trans-
59
-------
mission. Telephotometers of the
shortest possible base line might be
used, but once again have poor sen-
sitivity for typical urban haze. Spe-
cially devised instruments have been
designed and used with great diffi-
culty in the range of extinction found
in cities. Typical airport transmis-
someters are designed to be useful in
fog and are thus of little value except
in cases of extreme pollution and fog.
3. visual methods, though frequently
used, should be avoided because of
the subjectivity of the eye as a sen-
sor and the variations between ob-
servers, as well as the spatial varia-
tion problem mentioned above. If it
Is necessary to use visual observa-
tions, the observers must be methodi-
cal and should use the rules adopt-
ed by the United States Weather
Bureau.27
Ordinary methods (i.e. the high-volume
air sampler) for the determination of mass
concentration (/«g/ni3) may suffice if care is
taken to eliminate spurious large particles
such as insects, etc. As recent data taken in
Seattle show, newer sampling methods using
newer types of niters are becoming available
and allow a much shorter sampling time.
H. SUMMARY
The visual range, sometimes called the
"visibility," is reduced by particulate matter
in the air. It refers to the distance at which
it is just possible to perceive and object
against the horizon sky. Both the attenua-
tion of light from the object and illumination
of the air between the object and the ob-
server tend to reduce visibility, since they
reduce the perceived contrast between the
object and its background. Attenuation of
light passing through the air results from
two optical effects which air molecules and
small particles have on visible radiation: (1)
the absorption of light energy and (2) the
scattering of light out of the incident beam.
In general, reduced visibility is primarily a
result of scattering due to particulate mat-
ter. The "extinction coefficient," bscat, is a
measure of the degree of scattering, and it
is related to the visual range of a black ob-
ject as follows:
3.9
Lv= (m) . (3-3)
bscat
Suspended particulates found in the atmos-
phere cover a broad range of size; however;
the visibility is affected by a relatively nar-
row segment of this size distribution, usually
from about 0.1/i to Ip. radius. Once particu-
late matter has been suspended in the air for
some time, the distribution of particles by
size tends to take on a typical pattern. Be-
cause of this, and because the visible light
scattering is caused primarily by particles
of one narrow size range, the scattering can
be empirically related to the particulate con-
centration. This relationship is as follows:
LT~-
AxlO3
(from 3-9)
where G'=particle concentration (ju,g/m3)
LT = equivalent visual range
A = 1.2j;-* for LT expressed in kilome-
ters and
G.751^ for Lv expressed in miles.
The ranges that are shown for the constant,
A, cover virtually all cases studied. Devia-
tions from equation 3-9 would be expected to
occur when the relative humidity exceeds 70
percent, since many particles exhibit deli-
quescent behavior and grow into fog drop-
lets. (For a discussion of the relationship
between visibility and sulfur dioxide concen-
trations at various relative humidities, see
a companion volume to this document, Air
Quality Criteria for Sulfur Oxides.) Parti-
cles composed of sodium chloride, for ex-
ample, would act as condensation nuclei and
show rapid and large changes in size under
such circumstances. Also, this relationship
may not hold for photochemical smog, since
it is not known whether its size distribution
conforms to the necessary pattern.
Equation 3-9 provides a convenient means
for estimating the expected visibility for dif-
ferent levels of particulate concentrations,
under the conditions stated. With a typical
rural concentration such as 30 /xg/m3, the
visibility is about 25 miles; for common
urban concentrations, such as 100 /ig/m3
and 200 /*g/m3, the visibility would be 7.5
60
-------
miles and 3.75 miles, respectively. In addi-
tion to aesthetic degradation of the environ-
ment, reduced visibility has many conse-
quences for the safe operation of aircraft
and motor vehicles. When airports have
heavy traffic, visibility below 5 miles tends
to slow operations, since it is necessary to
maintain larger distances between aircraft.
Federal air regulations prescribe limitations
on aircraft operating under conditions of re-
duced visibility; they become increasingly
severe as the visibility decreases from 5
miles (150 j«g/m3) to 3 miles (250 ^g/m3)
to one mile (750 ^g/m3). Based on the empir-
ical variations in equation 3-9, the same vis-
ibilities could occur under certain circum-
stances, at concentrations one-half of these
calculated values. Thus, a concentration of
75 jug/m3 might produce a visibility of 5
miles in some instances.
I. REFERENCES
1. Holzworth, G. C. "Some Effects of Air Pollu-
tion on Visibility in and near Cities." In: Air
Over Cities Symposium, U.S. Dept. of Health,
Education, and Welfare, Robert A. Taft Sani-
tary Engineering Center, Cincinnati, Ohio, Tech-
nical Report A62-5, 1961, pp. 69-88.
2. Robinson, E. "Effects of Air Pollution on Visi-
bility." In: Air Pollution, Chapt 11, Vol. 1,
2nd edition, A. C. Stern (ed.), Academic Press,
New York, 1968, pp. 349-400.
3. Middleton, W. E. K. "Vision Through the Atmos-
phere." University of Toronto Press, 1952.
4. "Federal Aviation Regulations." Federal Avia-
tion Agency, 1967.
5. "A Study of Pollution—Air." A staff report
to the Committee on Public Works, U.S. Senate,
Washington, D.C., 1967.
6. "New York-New Jersey Air Pollution Abatement
Activity, Phase II—Particulate Matter." U.S.
Dept. of Health, Education, and Welfare, Na-
tional Center for Air Pollution Control, Wash-
ington, D.C., 1967.
7. "Kansas City, Kansas-Kansas City, Missouri,
Air Pollution Abatement Activity, Phase II—
Pre-conference Investigations." U.S. Dept. of
Health, Education, and Welfare, National Cen-
ter for Air Pollution Control, Washington, D.C.,
March 1968.
8. Angstrom, A. K. "On the Atmospheric Trans-
mission of Sun Radiation II." Geograph. Ann.
(Stockholm), Vol. 12, pp. 139-159, 1930.
9. Junge, C. E. "Air Chemistry and Radioactivity."
Academic Press, New York, 1963.
10. Conner, W. D. and Hodkinson, J. R. "Optical
Properties and Visual Effects of Smoke-Stack
Plumes." U.S. Dept. of Health, Education, and
Welfare, National Center for Air Pollution Con-
trol, PHS-Pub-999-AP-30, 1967.
11. Went, F. W. "Dispersion and Disposal of Or-
ganic Materials in the Atmosphere." Preprint
Series 31, University of Nevada, Desert Re-
search Institute, 1966.
12. Pilat, M. J. and Charlson, R. J. "Theoretical
and Optical Studies of Humidity Effects on the
Size Distribution of a Hygroscopic Aerosol." J.
Rech. Atmospheriques, Vol. 2, pp. 165-170, 1966.
13. Charlson, R. J., Horvath, H., and Pueschel, R. F.
"The Direct Measurement of Atmospheric Light
Scattering Coefficient for Studies of Visibility
and Air Pollution." Atmos. Environ., Vol. 1,
pp. 469-478, 1967.
14. "California Standards for Ambient Air Quality
and Motor Vehicle Exhaust—Technical Report."
Dept. of Public Health, Berkeley, California,
1960.
15. Friedlander, S. K. and Wang, C. S. "The Self-
Preserving Particle Size Distribution for Co-
agulation by Brownian Motion." J. Colloid In-
terface Sci., Vol. 22, pp. 126-132, 1966.
16. Whitby, K. T. and Clark, W. E. "Electric Aero-
sol Particle Counting and Size Distribution
Measuring System for the 0.15^ to 1/j. Size
Range." Tellus, Vol. 18, pp. 573-586, 1966.
17. Peterson, C. M. and Paulus, H. J. "Microme-
teorological Variables Applied to the Analysis
of Variation in Aerosol Concentration and Size."
Preprint. (Presented at the 60th Annual Meet-
ing, Air Pollution Control Association, Cleve-
land, Ohio, June 11-16,1967.)
18. Mie, G. "Beitrage zur Optik triiber Medien,
Speziell Kolloidaler Metallosungen." Ann.
Physik, Vol. 25, pp. 377-455, 1968.
19. Pueschel, R. F. and Noll, K. E. "Visibility and
Aerosol Size Frequency Distribution." J. Appl.
Meteorol, Vol. 6, pp. 1045-1052, 1967.
20. Charlson, R. J., Ahlquist, N. C., and Horvath, H.
"On the Generality or Correlation of Atmo-
spheric Aerosal Mass Concentration and Light
Scatter." Atmos. Environ., Vol. 2, pp. 455-464,
1968.
21. Noll, K. E., Mueller, P. K., and Imada, M. "Visi-
bility and Aerosol Concentration in Urban Air."
Atmos. Environ., Vol. 2, pp. 465-475, 1968.
22. Charlson, R. J. "Atmospheric Aerosol Research
at the University of Washington." J. Air Pol-
lution Control Assoc., Vol. 18, pp. 652-654, 1968.
23. Goetz, A., Preining, O., and Kallai, T. "The
Metastability of Natural and Urban Aerosols."
Rev. Geofis. Pura Appl. (Milano), Vol. 60, pp.
67-80, 1961.
24. Acheson, D. T. "Vapor Pressures of Saturated
Aqueous Salt Solutions." Proc. Intern. Symp.
Humidity and Moisture, Washington, D.C., May
1963, pp. 521-530.
61
-------
25. Ahlquist, N. C. and Charlson, R. J. "Measure- Air." J. Air Pollution Control Assoc., Vol. 17,
ment of the Vertical and Horizontal Profile of pp. 467-469, 1967.
Aerosol Concentration in Urban Air with the
Integrating Nephelometer." Environ. Sci. Tech- 27. "Manual of Surface Observations (WBAN)."
nol., Vol. 2, pp. 363-366,1968. Circular N, 7th Edition (Revised to include
26. Ahlquist, N. C. and Charlson, R. J. "A New In- changes 1 through 14), U.S. Weather Bureau,
strument for Evaluating the Visual Quality of January 1968.
62
-------
Chapter 4
EFFECTS OF ATMOSPHERIC
PARTICULATE MATTER ON MATERIALS
-------
Table of Contents
Page
A. INTRODUCTION 65
B. EFFECTS OF PARTICULATE MATTER ON METALS 65
C. EFFECTS OF PARTICULATE MATTER ON BUILDING
MATERIALS . 69
D. SOILING AND DETERIORATION OF PAINTED SURFACES 71
E. SOILING AND DEGRADATION OF TEXTILES 71
F. SUMMARY 72
G. REFERENCES , . 74
List of Figures
Figure
4-1 Plot of Rate of Rusting Versus Dustfall at Four Locations 66
4—2 Weight Loss from Zinc Specimen as a Function of Exposure Time . 67
4-3 District Building, Washington, D. C. 67
List of Tables
Table
4-1 Corrosion of Open-Hearth Iron Specimens in Different Locations 66
4-2 Corrosivity of Atmospheres towards Steel and Zinc at Selected Loca-
tions Relative to that at State College . . 68
4—3 The Corrosion Rates of Metals in Various Locations 70
64
-------
Chapter 4
EFFECTS OF ATMOSPHERIC PARTICULATE MATTER ON MATERIALS
A. INTRODUCTION
Airborne particles may damage surfaces
merely by settling on them. A light deposit of
dust makes surfaces appear dingy, and the
frequent cleaning necessary in a dusty atmos-
phere weakens materials and costs money.
Particles can also cause direct or chemical
deterioration of materials. The nature and
extent of the deterioration depends on the
chemical activity of the particles in their en-
vironment and the relative susceptibility of
the receiving material. Particles may cause
chemical deterioration either by acting as
condensation nuclei for the retention of ad-
sorbed gases or harmful acids, or by their
own innate corrosive action.
In the following sections it will be seen
that particulate air pollution plays an impor-
tant role in the corrosion of metals; in the
soiling, damage, and erosion of coatings and
painted surfaces, building stones, marble,
and other building materials; and in the soil-
ing and degradation of textiles.
B. EFFECTS OF PARTICULATE MATTER
ON METALS
Atmospheric particles may accelerate the
corrosion of iron, steel, and various nonfer-
rous metals.
Metals are generally resistant to attack in
dry air,1 and even clean moist air does not
cause significant corrosion.1-2 Furthermore,
inert dust and soot particles without sulfur
compounds as constituents do not of them-
selves cause marked corrosion.1-3 Particles
may, however, contribute to accelerated cor-
rosion in two ways.4 First, they may be in-
trinsically active, and secondly, although in-
active, they may be capable of absorbing or
adsorbing active gases (such as S02) from
the atmosphere.
Those particles which are inactive and
have negligible capacity for absorption or
adsorption have little effect other than that
of acting as droplet nuclei in the atmosphere.
For example, silica particles do not acceler-
ate the rate of metal corrosion even in the
presence of S02. On the other hand, char-
coal (carbonaceous) particles in atmos-
pheres with relative humidities below 100
percent cause a large increase in the rate of
corrosion in the presence of S02 traces, pre-
sumably through the local concentration of
the gas by adsorption.4 The laboratory re-
search which led to these findings was based
on particulate concentrations of 0.4 mg/cm2
(equivalent to 0.3 tons/mi2) and abnormally
high S02 concentrations of 100 ppm.
Active hygroscopic particles such as sul-
fate and chloride salts and sulfuric acid aero-
sol serve as corrosion nuclei. Their presence
in the atmosphere can initiate corrosion, even
at low relative humidities.5 Laboratory stud-
ies of bare and varnished steel test panels,
properly polished and degreased, and then
inoculated with finely divided particles of
various substances such as are commonly
found in the atmosphere, were conducted by
Preston and Sanyal.5 Particles of chloride,
sulfate, chromate, and oxide salts, and boiler
and flue dusts were used. The metal test pan-
els were exposed to atmospheres of pure
clean air and of air containing S02 at vari-
ous humidities, and the resulting corrosion
was measured. Filiform corrosion, character-
ized by a filamental configuration, the pri-
mary phase in electrolytic corrosion, was
noted in all cases. Corrosion rates are low
when the relative humidity is below 70 per-
cent, but they increase at higher humidi-
ties.4- e In most of the cases in this study,
corrosion increased with increased humidity
even in clean air. The addition of traces of
65
-------
S02 to the test atmosphere greatly increased
the rate of corrosion in all instances.5
Field experiments show that the rate of
corrosion of various metals is accelerated in
urban and industrial areas because of the
greater atmospheric concentrations of both
particulate matter and sulfur compounds.
Standardized open-hearth iron specimens,
after exposure for one year at a number of
diverse locations throughout the world, were
observed by Hudson7 to have a manifiold
variation in weight loss. Iron specimens ex-
posed for one year to desert and arctic en-
vironments, the least polluted areas, were
the least corroded, i.e., had the smallest
losses in weight. Those speimens exposed at
heavily-polluted urban industrial sites were
the most corroded, more so than similar
specimens exposed at many marine and trop-
ical locations, Table 4-1. Hudson, Figure 4-1,
also correlated the rate of rusting of mild
steel specimens and dustfall levels for four
diverse areas, from a heavily industrialized
area in Sheffield, England, to a rural area
(Llanwrtyd Wells). The iron specimens cor-
roded four times as fast in the polluted in-
dustrial atmosphere as they did in the rural
atmosphere.
Committee B-3 of the American Society
of Testing Materials (ASTM)8'9 studied cor-
UJ
5
2
CC
U.
o
UJ 1
<
cc
OJ
SHEFFIELD
WOOLWICH
CALSHOT
LLANWRTYD WELLS
16 32 48 64 80
DUST FALL, TONS / Ml2- MONTH
96
FIGURE 4-1. Plot of Rate of Rusting Versus Dust-
fall at Four Locations.7 (The figure plots the rate
of rusting of mild steel versus dustfall, and shows
that corrosion is four times as rapid in an in-
dustrial area (Sheffield) as it is in the rural area
(Llanwrtyd Wells)).
rosion rates of steel and zinc panels exposed
for one year at several locations in the United
States. The relative corrosivities of various
atmospheres at 19 sites were compared to
that of the rural site of State College, Penn-
sylvania, which was used as a base. This
study (Table 4-2) confirms Hudson's ob-
servations that industrial locations with
Table 4-1.—CORROSION OF OPEN HEARTH IRON SPECIMENS IN DIFFERENT LOCATIONS.7
Location
Khartoum, Sudan
Abisko, North Sweden
Aro, Nigeria
Singapore Malaya
Basrah Iran
Apapa, Nigeria - -
State College Pa , USA
Berlin Germany
Llanwrtyd Wells British Isles
Calshot British Isles
Sandy Hook N J USA
Motherwell British Isles
Pittsburgh Pa USA
Sheffield Univ British Isles
Derby South End, British Isles
Derby North End, British Isles
Frodineham. British Isles. — _
Type of atmosphere
Dry inland, . __ . _ .
Unpolluted
Tropical inland
Tropical marine
Dry inland
_ Tropical marine _ . . _.
Rural
Semi-industrial
Semi-marine . _ ____
Marine
Marine-scmi-industrial
Marine
Industrial
Industrial
Industrial
Industrial _ _
Industrial
Industrial
. . _ _ Industrial
Annual
weight
loss, g
0.16
0.46
1.19
1.36
1.39
2.29
3.75
4.71
5.23
6.10
7.34
7.34
8.17
8.91
9.65
11.53
12.05
12.52
14.81
Relative
corro-
sivity
1
3
8
9
9
15
25
32
35
41
50
50
55
60
65
78
81
84
100
66
-------
high concentrations of particles and of ox-
ides of sulfur are more corrosive to steel and
zinc than less industrialized areas. As shown
in Table 4-2, steel specimens corroded in one
year approximately 3.1 times as much in
New York City (spring exposure) and 3.3
times as much in Kearny, New Jersey, as
similar specimens at State College, Pennsyl-
vania. Zinc specimens corroded 3.6 and 2.6
times as much in New York City (spring ex-
posure) and Kearny respectively, as similar
specimens exposed at State College. Both
steel and zinc specimens in New York City
(fall exposure when the particle and S02
concentrations in the atmosphere are greater
than in spring) corroded 6.0 and 3.7 times as
much respectively as similar steel and zinc
speciments at Sate College.8 The authors of
the resulting papers did not give mean con-
centrations of suspended particulate matter
for the various locations; but approximate
concentrations, based on NASN measure-
ments 10 made after the corrosion studies, are
given here. Based on Table 4-3, a town the
size of State College, Pa., could have a mean
suspended particulate-matter level of 60 //,g/
m3 to 65 /xg/m3. The mean suspended par-
ticulate matter concentrations were 176
Table 4-2.—CORROSIVITY OF ATMOSPHERES TOWARDS STEEL AND ZINC AT SELECTED
LOCATIONS RELATIVE TO THAT AT STATE COLLEGE, PENNSYLVANIA.8
Location
Type of atmosphere
Relative corrosivity
of one-year test for
Steel
Zinc
Norman Wells, N.W.T., Canada _
Esquimalt, Vancouver Is., Canada __ __
Saskatoon, Sask., Canada _ -
Perrine, Fla ... _ _ _____
State College, Pa
Ottawa, Canada
Middletown, Ohio_
Trail, B.C., Canada
Montreal, Que., Canada _ __ . _ _
Halifax, N.S., Canada
South Bend, Pa
Kure Beach, N.C., 800-ft site
Point Reyes, Calif
Sandy Hook, N. J _ _ _
New York, N.Y. (spring exposure)
Kearny, N. J _______
Halifax, N.S., Canada__ _ __ _
New York, N.Y. (fall exposure) _
Daytona Beach, Fla
Kure Beach, N.C., 80-ft site
Polar-Rural ._ .
Rural-Marine a___ _
Rural
Rural
Rural
Semi-Rural - - - _ _
Semi-Industrial __
_ . Semi-Rural . _ __ __
... Industrial .
Rural-Marine _ _ .
Semi-Rural . _ _
Marine (800 ft from ocean) _ _
Marine _ _ _
Industrial-Marine _ _ _ _
Industrial - _ ,
Industrial-, ____ __. ___
Industrial-Marine b _ _
Industrial
Marine _. . _
Marine (80 ft from ocean). __ _._ _.
0.03
0.5
0.6
0.9
1.0
1.0
1.2
1.4
1.5
1.5
1.5
1.8
1.8
2.2
3.1
3.3
3.8
6.0
7.1
13.0
0.4
0.4
0.5
1.0
1.0
1.2
.9
1.6
2.2
1.6
1.5
1.7
1.8
1.6
3.6
2.6
18.0
3.7
2.6
5.7
a While test site is 1500 ft. from brackish water, prevailing winds are from inland and prevent deposition of salt
water spray.
b Test site is near a smokestack; prevailing winds blow fumes over the test site.
Table 4-3.—THE CORROSION RATES OF METALS IN VARIOUS LOCATIONS.9
Corrosion rate, mil/year
Test Site
Altoona, Pa. (Heavy industrial-R.R.)
New York, N.Y. (Urban-industrial)
State College, Pa. (Rural-farm) .
Phoenix, Ariz. (Rural-semiarid)
Nickel
200
.. . . 0.222
0.144
0.0085
0.0015
Monel
alloy 400
0.076
0.062
0.007
0.002
Copper
0.055
0.054
0.017
0.005
67
-------
in New York City and 131 ng/m3 at
Elizabeth, New Jersey, near Kearney,10 it
should be pointed out that there are signifi-
cant differences in levels of gaseous pollution,
particularly sulfur dioxide, between State
College and the larger industrial communi-
ties. Consequently, the differences in corro-
sion rates cannot be solely attributed to the
effects of particulates.
In Chicago and St. Louis, steel panels were
exposed at a number of sites, and measure-
ments were taken of corrosion rates and of
levels of sulfur dioxide and particulates.11 In
St. Louis, except for one exceptionally pol-
luted site, corrosion losses correlated well
with sulfur dioxide levels, averaging 30 per-
cent to 80 percent higher than corrosion
losses measured in nonurban locations. Over
a 12-month period in Chicago, the corrosion
rate at the most corrosive site (mean S02
level of 0.12 ppm) was about 50 percent
higher than at the least corrosive site (mean
S02 level of 0.03 ppm). Sulfation rates in St.
Louis, measured by lead peroxide candle,
also correlated well with weight loss due to
corrosion. Although suspended particulate
levels measured in Chicago with high-volume
samplers correlated with corrosion rates, a
covariance analysis indicated that sulfur di-
oxide concentrations had the dominant in-
fluence on corrosion. Measurements of dust-
fall in St. Louis, however, did not correlate
significantly with corrosion rates. Based on
these data, it appears that considerable cor-
rosion may take place (i.e., from 11 percent
to 17 percent weight loss in 'steel panels) at
annual average sulfur dioxide concentrations
in the range of 0.03 ppm to 0.12 ppm, and
although high particulate levels tend to ac-
company high sulfur dioxide levels, the sul-
fur dioxide concentration appears to have the
more important influence.
Comparative studies of the rates of cor-
rosion of zinc-coated steel panels exposed
to various community atmospheres were con-
ducted by Committee B-3 of the ASTM.9 The
corrosion rates of zinc at four of the loca-
tions over a six-year period are shown in
Figure 4-2, as weight loss versus time. For
each location, the corrosion rate is essential-
ly constant with time. The atmosphere of
New York City with greater concentration
NEW YORK CITY
(INDUSTRIAL)
A KEARNY, N.J.
(INDUSTRIAL)
234
EXPOSURE, YEARS
FIGURE 4-2. Weight Loss from Zinc Specimen as a
Function of Exposure Time.8 (The figure shows
the rate of corrosion of zinc at four locations in
the United States, and indicates that corrosion is
more rapid in industrial areas.)
of particles and sulfur oxides produces a
steeper rate of corrosion of zinc than that
of Kearny, New Jersey, which is also heavily
polluted. Zinc corrodes at a greater rate
in both industrial communities than in the
rural or semirural sites in South Bend,
Pennsylvania, and State College, Pennsyl-
vania.8
Studies of the effects of air pollution on
the atmospheric corrosion of three metals
(nickel 200, Monel alloy 400, and copper)
exposed to four diverse atmospheres (heavy-
industrial, urban-industrial, rural-farm, and
rural-semiarid) were conducted over a 20-
year period.9 Nickel 200 is 99.5 percent nickel
and Monel 400 is essentially 30 percent cop-
per and 70 percent nickel. Though these
metals are relatively corrosion-resistant, it
will be noted from Table 4-3 that they are
68
-------
corroded more in industrial atmospheres
than in rural ones. However, because of the
corrosion resistance of the metals, all of the
rates are relatively low when compared to
those for unalloyed iron or steel. In the in-
dustrial locations, nickel 200 corroded at
rates two to four times greater than Monel
(nickel-copper) alloy 400, while in the rural
locations, its corrosion rate was about equal
to that of Monel alloy 400, and only one-half
the rate for copper. Even Monel 400, with
its superior corrosion resistance, when used
as a gutter in an industrial installation, be-
came pitted when the soot was permitted to
accumulate.9 Unburned carbon in the soot
led to the formation of local galvanic cor-
rosion cells. The result was premature per-
foration and accelerated attack of the metal
sheet.
Larrabee12 confirmed that the corrosion
resistance of steel is greatly improved by the
addition of small amounts of copper, or low
alloys of chromium, nickel, copper, and phos-
phorus. The additional cost of such alloy
steels when they are used to resist atmos-
pheric corrosion is attributable to air pollu-
tion.
Particles can cause corrosion of electronic
gear of all types even where pervious metals
are used to minimize such corrosion. Elec-
trical instruments and electronic components
are factors of growing importance in the
computer and missile industries, and also
monitor and control an increasingly large
share of manufacturing processes.13 Oily or
tarry particles, commonly found in industrial
and urban areas, are serious factors in the
corrosion and failure of electric contacts,
connectors, and components.13
Dust can act mechanically or chemically on
electric contacts. It can deposit on the sur-
faces and interfere with electrical contact
closure, it can become imbedded in the sur-
faces of contacts, or it can induce wear by
abrasion if the contacts slide.13-14 Hygro-
scopic dusts, accumulated on contacts, will
absorb water to form thin electrolytic films
which are corrosive to base metals.5 If the
contact members are not of identical com-
position, galvanic corrosion may occur. The
tarnish and corrosion films impair or cause
failures in electrical conductivity, and can be
avoided or minimized only by fabricating the
electrical contacts out of nonreactive metals,
by encapsulation, or by air purification de-
vices such as filters or by gas-absorbing
chemicals. Any of these solutions to the prob-
lem increases costs.
C. EFFECTS OF PARTICULATE MATTER
ON BUILDING MATERIALS
Building materials and surfaces are soiled,
disfigured, and damaged by atmospheric par-
ticles. Some of these stick to surfaces of
stone, brick, paint, glass, and composition
materials, forming a film of tarry soot and
grit which may or may not be removed by
the action of the rain. The result is a dingy,
soiled appearance (Figure 4-3), a loss in
aesthetic attractiveness- and, in many cases,
a physical-chemical degradation or erosion of
these surfaces.
In cities where large quantities of soot-
providing fuel are burned, the problem is
particularly severe. Much money and effort
have been spent on sandblasting off the sooty
layers which have accumulated on prominent
buildings in burning soot-producing fuel
cities.15^17 The tarry substances or carbona-
ceous material resulting from inefficient com-
bustion of soot-producing fuel are likely to
be sticky and also acidic;2 if not flushed off
by rain they will adhere to surfaces and cor-
rode them over extended periods of time.18
Smoke particles may also act as a reservoir
for adsorbed gases, such as S02, and harmful
acids, including sulfurous, sulfuric, and hy-
drochloric acids, as well as hydrogen sulfide.
These materials cause the deterioi ation of
many of the less resistant tyes ol° mason-
ry_19, 20
Buildings in polluted areas bee ime un-
sightly quickly and require periodic cleaning
and maintenance to remove the t irry as-
phalt-like deposits. In Washington D.C.' it
was found necessary to clean the si loke and
grime from the new Supreme Court building
even before initial occupancy (in "he mid-
thirties).16 While the soiling effect < f soot is
by far the most evident to the eye, il does not
in itself cause the deterioration oi building
material. The destruction is due to acids
alone or to acids adsorbed on particulate
matter.
69
-------
§
bo
•J3
.n
T3
bo
3
-Q ^
O O
•s g
s-a
-^
o a
o n!
ra SH
sf
o 2
,„ 1>
.2 ft
H *
~ be
Q-S
c
2
.g
is
'3
m
03
s
70
-------
D. SOILING AND DETERIORATION OF
PAINTED SURFACES
Painted surfaces, walls, and ceilings of
homes and other buildings are soiled by tarry
and other particulate substances in the at-
mosphere. Furthermore, there are both liq-
uid and solid particles present in polluted
air in the form of fumes and mists of vary-
ing chemical composition which react with
painted surfaces.18-21 The damage done is
both aesthetic and material, and may affect
not only buildings but also paintings and
other works of art.
Auto finishes have been observed to be-
come pitted and stained by iron particles
deposited on them from a metal grinding op-
eration nearby,6-22 while chromic acid mist
from an electroplating operation formed a
brown stain on light colored cars and a
"blushing" on darker shades of paint. Re-
painting was required because the color
changes were not reversible by washing or
polishing.18-23 Cars parked near demolition
operations of brick buildings have been se-
verely damaged by alkali mortar dust in the
presence of moisture.18 Characteristic pitting
of painted surfaces is also caused by sodium
carbonate particles from such industrial
processing as soda ash manufacture.
Water soluble chlorides and sulfates—
mostly the iron, copper, calcium, and zinc
salts—are commonly found in particulate
samples from cities21'23-24 and in rainwa-
ter.23 These water-soluble particles are po-
tential sources of osmotic blistering of
painted surfaces. The effects on weathering
by small quantities of such particles have
been examined 21 during laboratory studies
of accelerated aging of various paint panels.
The presence of 0.1 ppm of iron in the water
in the accelerated weather apparatus pro-
duced yellow staining, while 0.5 ppm of cop-
per produced severe brown staining. These
same effects may be expected on natural ex-
posure.21
Dust particles settling on wet varnish and
paint films produce visible imperfections and
reduction in the electrical resistance and
anticorrosive properties of such films.25 In
laboratory tests to examine the relationship
to corrosion of dust particles under the pro-
tective coatings, two sets of metal panels
were coated with a varnish formulation un-
der a "dust-free" apparatus, and then one set
was removed from the apparatus so that the
varnish films dried in contact with the lab-
oratory air. The panels were then immersed
in 3 percent aqueous sodium chloride for
seven and one-half months. Where the var-
nish film had dried in "normal" laboratory
room air, considerable rusting occurred on
the panels after six months of immersion; no
corrosion occurred on the panels dried in the
"dust-free" environment. Clearly the dust
particles that settled on the films of the pan-
els during the drying period were a pre-
dominant factor in initiating corrosion of the
metal.25
The exteriors of buildings in industrial
areas, when repainted, collect numerous
black specks on their surfaces even before
the paint has dried.26 Within two to four
years- depending on the degree of particle
concentration, these building exteriors are
distinctly soiled and require repainting.16-26
E. SOILING AND DEGRADATION
OF TEXTILES
Soiling of clothing, curtains, and other
textiles not only diminishes their aesthetic
appeal but also reduces their functional ef-
fectiveness. A garment which soils readily
will not have the same user appeal as one
which does not, even though its performance
may be equal in other respects. Economic
costs are therefore involved both in the extra
cleaning of garments which soil readily and
in the development and manufacture of soil-
resistant textiles.
The extent of soiling of textiles, such as
curtains, is influenced by various external
factors such as temperature, relative humid-
dity, and wind speed- and the specific size
and characteristics of the atmospheric par-
ticles. In addition, the degree of soiling is de-
pendent on the construction and finish of the
textile material and the type of fiber from
which it is made.27
When large particles are deposited on the
surface of the textile, the soiling may be
superficial. In moving air, however, the par-
ticles may be directly intercepted by the indi-
vidual fibers or may be thrown onto the fibers
71
-------
as air sweeps through the intricate channels
between them, i.e., the material behaves as a
filter. The soiling of curtains and flags is an
illustration of this effect. Airborne particles
can also affect the cleanliness of yarns and
fabrics during their manufacture. Economic
loss to textile manufacturers can occur unless
suitable air filters are used in manufacturing
plants.27 Laboratory studies by Rees,27 using
a dust circulating apparatus under controlled
conditions; show that a closely woven fabric
of low porosity best resists soiling by air-
borne particles.
If an exposed textile material acquires an
electrostatic charge, for example by friction,
and is able to retain its charge, charged par-
ticles of opposite sign will be attracted to it,
thereby increasing its rate of soiling.27 Cel-
lulose acetate and some of the synthetic tex-
tiles acquire, by friction during spinning and
weaving, electrostatic charges which, be-
cause of the high insulating properties of
these materials, are retained for a long peri-
od of time. This results in troublesome "fog-
marking," caused by attraction of airborne
particles to the charged textile.27
In laboratory investigations of the electro-
static attraction of airborne particles to cot-
ton textiles, Rees 27 found that soiling is more
rapid when the fabric is charged than when
uncharged, and that the rate of soiling is
increased by raising the applied electric po-
tential (which increases the charge density
on the fabric). For any given potential, the
rate of soiling appears to be greater for a
positively charged fabric specimen than for
a negatively charged one.
The vulnerability of textile fabrics and
furnishings to the acid components of par-
ticulate matter depends on the chemical com-
position of the textiles.28 Cellulosic fibers,
such as cotton, linen, hemp, jute, and man-
made rayon are particularly sensitive to at-
tack from such substances as sulfurous and
sulfuric acids, while animal fibers, such as
wool and furs, are more resistant to acid
damage.28
Curtains are particularly vulnerable to air
pollutants and often deteriorate quickly
hanging at open windows; soiling occurs to
some extent even when windows are closed.
The curtain material acts more or less as a
filter for acid-laden dust and soot. Airborne
metallic iron and zinc particles, constituents
of city dust,23- 28> -g are catalysts and pro-
mote oxidation of sulfur dioxide to sulfuric
acid, which may contribute to textile degra-
dation. Curtains weakened by conditions of
exposure arising partly from atmospheric
soiling and acidity give way in a character-
istic manner by splitting in parallel lines
along the folds where the greatest number
of particles accumulated.
F. SUMMARY
Airborne particles—including soot, dust,
fumes, and mist—can, according to their
chemical composition and physical state,
cause a wide range of damage to materials.
They may cause deterioration merely by
settling on surfaces and soiling them thus
creating a need for more frequent clean-
ing which in itself weakens materials. More
importantly, they can cause direct chemi-
cal damage to materials in two ways: First,
through their own intrinsic corrosiveness,
and secondly, through the action of corrosive
chemicals which they may have absorbed
or adsorbed. Airborne particulates have
been implicated in the corrosion of metals
and metallic surfaces; in the soiling, dam-
age, and erosion of buildings and other
structures; in the discoloration and destruc-
tion of painted surfaces; and in the aesthetic
degradation and damage of fabrics and
clothing.
Metals ordinarily can resist corrosion in
dry air alone, or even in moist clean air.
Even inert dust or soot, in the absence of
active chemical agents- has little effect on
metal surfaces. However, hydroscopic par-
ticles commonly found in the atmosphere can
corrode metal surfaces although no other
pollutants may be present. This was shown
in laboratory studies in which steel test pan-
els were dusted with various common par-
ticulates. Although corrosion rates were low
at relative humidities under 70 percent, they
tended to increase with increased humidity.
The addition of sulfur dioxide to the lab-
oratory air greatly accelerated the rates of
corrosion.
In general, there is an increasing rate of
corrosivity as we go from dry, unpopulated
72
-------
environments, the least polluted areas, to
heavily polluted urban industrial sites. Sam-
ples of iron, for example, have shown weight'
loss due to corrosion that is four times
greater in industrial atmospheres than in
rural atmospheres. Steel samples corroded
in one year 3.1 times as much in New York
City (spring exposure), where the particu-
late concentration was 176 /«g/m3, as in the
rural atmosphere of State College, Penn-
sylvania, where the mean concentration
could be expected to range about 60 /ig/m3
to 65 /ig/m3. Steel samples exposed in New
York in the fall of the year, when the par-
ticulate and sulfur dioxide levels are higher
than in the spring, corroded 6 times faster
than the samples at State College. Similarly,
zinc samples exposed in New York corroded
about 3.6 times as much as those at State
College, while zinc samples at Kearny, New
Jersey, corroded about 2.6 times as much
(the concentration was 131 /*g/m3 at Eliza-
beth, New Jersey, near Kearney).
It should be concluded, however, that the
variation in corrosion rates referred to above
are due only to differences in particulate
matter, since there are significant differ-
ences in gaseous pollutant concentrations be-
tween State College and the other areas.
Even highly resistant metals have shown
corrosion rates which are progressively
larger over the following range of environ-
ments; (1) a rural semiarid site; (2) a
rural farm enviornment; (3) an urban in-
dustrial area; (4) a heavy industrial area.
In Chicago and St. Louis, steel panels were
exposed at a number of sites, and measure-
ments were taken of corrosion rates and of
levels of sulfur dioxide and particulates. In
St. Louis, except for one exceptionally pol-
luted site, corrosion losses correlated well
with sulfur dioxide levels, averaging 30 per-
cent to 80 percent higher than corrosion
losses measured in nonurban locations. Over
a 12-month period in Chicago, the corrosion
rate at the most corrosive site (mean S02
level of 0.12 ppm) was about 50 percent
higher than at the least corrosive site (mean
S02 level of 0.03 ppm). Sulfation rates in
St. Louis, measured by lead peroxide candle,
also correlated well with weight loss due to
corrosion. Although suspended particulate
levels measured in Chicago with high-vol-
ume samplers correlated with corrosion
rates, a covariance analysis indicated that
sulfur dioxide concentrations had the domi-
nant influence on corrosion. Measurements
of dustfall in St. Louis, however, did not
correlate significantly with corrosion rates.
Based on these data, it appears that consid-
erable corrosion may take place (i.e., from
11 percent to 17 percent weight loss in steel
panels) at annual average sulfur dioxide
concentrations in the range of 0.03 ppm to
0.12 ppm, and although high particulate lev-
els tend to accompany high sulfur dioxide
levels, the sulfur dioxide concentration ap-
pears to have the more important influence.
Particles play a significant role in corro-
sion and damage to electronic equipment of
all kinds, even when precious metals are
used to minimize such effects. The contacts
in electrical switches are vulnerable to chem-
ical or mechanical action by particulates.
The particulates commonly found in indus-
trial and urban atmospheres are serious fac-
tors in the corrosion and failure of electrical
connectors and circuits.
The ability of particulates to damage and
soil buildings, sculpture, and other struc-
tures is particularly great in cities where
large quantities of coal and sulfur-bearing
fuel oil are burned. Particles may cause de-
terioration to many types of masonry by
acting as reservoirs for the harmful acids
generated by the combustion of these fuels.
In addition to direct erosion and physical
degradation of materials, particles stick to
surfaces with which they come in contact,
forming a film of tarry soot and grit which
may or may not be removed by the action
of rain. The result is a dingy, soiled appear-
ance, and much money and effort must
be spent to sandblast off the sooty layers that
accumulate.
Particles also may soil the painted sur-
faces of walls, ceilings, and the exteriors
of homes and buildings, and, under certain
circumstances, may cause them to become
stained and pitted. Automobile finishes, for
example, have been damaged by particulate
matter emitted from nearby industrial op-
erations. Water soluble chlorides and sul-
fates—mostly the iron, copper, calcium, and
73
-------
zinc salts—are commonly found in particu-
late samples from cities and in rainwater
and may cause blistering and enhance the
weathering of painted surfaces. Particles
may settle on painted surfaces before the
paint has dried, thus producing imperfec-
tions and reducing the ability of the paint
to protect the surface. Such surfaces are
likely to soon require refinishing.
The soiling of clothing, curtains, and simi-
lar textiles makes them unattractive and di-
minishes their use. The extent of soiling
is influenced by a number of factors, includ-
ing the temperature, the relative humidity,
and the wind conditions. Small particles
may penetrate deep into the fibers of cur-
tains hanging in open windows. Curtains
weakened by such exposure to atmospheric
soiling and acidity deteriorate in a charac-
teristic manner. The vulnerability of tex-
tile products to the acid components of air-
borne particles also depends on the compo-
sition of the material. Cellulosic fibers, for
example, such as cotton, linen, hemp, jute,
and man-made rayon, are particularly sensi-
tive to attack from such substances as sul-
furous and sulfuric acids. In addition to
the aesthetic degradation and the nuisance
created by particulate matter, direct costs
may be associated with the increased rate
of deterioration of textiles, the extra clean-
ing required, and the manufacturing ex-
penses for fabrics that are more resistant to
air pollution.
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Vol. 7, pp. 779-786, 1963.
25. Graff-Baker, C. "The Effect of Dust Particles on
the Electrical Resistance and Anti-Corrosive
Properties of Varnish and Paint Films." J. Appl.
Chem., Vol. 8, pp. 500-598, 1958.
26. Parker, A. "The Destructive Effects of Air Pol-
lution on Materials." The Sixth Des Voeux
Memorial Lecture. (Presented at the Annual Con-
ference of the National Smoke Abatement Soci-
ety, Bournemouth, England, September 28,
1955.)
27. Rees, W. H. "Atmospheric Pollution and Soiling
of Textile Materials." Brit. J. Appl. Phys., Vol.
9, pp. 301-305, 1958.
28. Petrie, T. C. "Smoke and the Curtains." Smoke-
less Air, Vol. 18, pp. 62-64, 1948.
29. Tebbens, B. D. "Residual Pollution Products in
the Atmosphere." In: Air Pollution, Chapter 2,
Vol. 1, 1st edition, A. C. Stern (ed.), Academic
Press, New York, 1962, pp. 23-40.
75
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Chapter 5
ECONOMIC EFFECTS OF ATMOSPHERIC
PARTICULATE MATTER
-------
Table of Contents
Page
A. INTRODUCTION 79
1. The Role of Economic Analysis . 79
2. Gross Estimates . 80
B. EARLY ECONOMIC STUDIES 81
1. Pittsburgh 81
2. Other Early Economic Studies . . 81
C. RECENT EFFORTS . .81
1. Household Effects . .... 81
2. Property Value Studies . 83
3. Productivity Studies .... 84
D. SUMMARY .84
E. REFERENCES 85
List of Figures
Figure
5—1 Maintenance Frequency as a Function of Particle Concentration in
the Upper Ohio River Valley and the National Capital Area (for
Households of Above-average Income) . . . . . 82
List of Tables
Table
5-1 Estimated Costs Due to Air Pollution (Mellon Institute Pittsburgh
Study) . . . . 81
5-2 Differences in Cleaning Costs Incurred at Steubenville and at Union-
town . 82
78
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Chapter 5
ECONOMIC EFFECTS OF ATMOSPHERIC PARTICULATE MATTER
A. INTRODUCTION
1. The Role of Economic Analysis
It is, perhaps, misleading to cordon off the
so-called economic effects of particulate pol-
lutants from the effects which are the grist
of this document. All of the effects discussed
in this document have an economic dimen-
sion. Some of the economic dimensions are
easier to measure than others. It is difficult
to determine, for example, what is the value
of preserving the health, or indeed the life,
of individuals adversely affected by pollu-
tion. It is somewhat easier to discover dif-
ferences in expenditure patterns attributable
to the presence of air pollution.
Difficult or easy, such valuation is a logi-
cally necessary part of the air quality stand-
ards decision process. Communities desir-
ous of a more favorable environment are
confronted with the need for two bodies of
fact. First, there are the physical and tech-
nological laws that govern the generation,
transport, and control of air pollution. Sec-
ond, there are the undesirable effects of
pollution on man and his environment. Fur-
thermore' these two realities conspire to pro-
duce a dilemma. On the one hand, if the
undesirable effects of air pollution are to
be avoided, economic resources that might
otherwise be used to satisfy other worthy
community objectives will have to be used
for air pollution control instead, and the
other objectives foregone. If, on the other
hand, all these other objectives are retained
undiminished, the effects of a polluted en-
vironment must be endured. It is evident
that some sort of balance must be struck.
Precisely where this balance is achieved is
a matter for the individual community to
decide.
The tools of economic analysis can illu-
minate the nature of this dilemma and can
even, with some qualification, indicate a way
out. It is sometimes suggested, for instance,
that the monetary value of the undesirable
consequences of not controlling air pollution
be balanced against the consequences of in-
stituting control. This is the thrust of the
much-heralded cost-benefit analysis, under
which the decision maker must consider the
available alternatives and choose that which
seems most favorable. Comparisons are
made insofar as possible in monetary terms,
with the dollar serving as a common denomi-
nator. It is the purpose of this chapter to
review the as-yet-small body of literature on
the economic value of the effects listed
throughout this volume.
A major difficulty in assessing damages
due to particulate air pollution lies in iso-
lating the effects of particulates from those
of other classes of air pollutants, such as sul-
fur oxides, ozone, oxides of nitrogen, and
others, including odors. The present state
of the arts with respect to the measurement
transport, ambient dosages, and the short-
term and long-term effects of the several
air pollutants in various concentrations,
durations, and conditions, demands that in-
creased attention, including an expanded
research effort, be given to the determina-
tion of the effects of air pollution and the
economic costs of those effects.
It is a major objective of research into
the economic effects of air pollution to estab-
lish quantitative relationships between vary-
ing levels of pollution and outcomes (the
effects of those levels) and ultimately to
arrive at acceptable measures of the eco-
nomic costs attributable to them. In turn,
when such costs are averted they become the
benefits of air pollution control.
79
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2. Gross Estimates
A review of the physical effects cited in
previous chapters suggests the possibility
of estimating damage factors and costs of
damages. The basic measurement procedure
involves four steps:
1. Identification of nonoverlapping cate-
gories of air pollution damage;
2. An estimate of the total value of the
category, regardless of the air pol-
lution effects;
3. Determination of an air pollution
damage factor incorporating assump-
tions or knowledge of the relation-
ships between the total size of the
category and the damages due to air
pollution; and
4. Application of this damage factor to
the total value of the category, in
order to estimate the damages due
to air pollution and those due to the
particular pollutant.
For example, one category of effects is the
corrosion of steel structures which necessi-
tates painting. An estimate might be devel-
oped along the following lines. The Steel
Structures Painting Council, Pittsburgh,
Pa., estimated the annual cost of corrosion-
inhibiting coatings applied to steel struc-
tures at $500 million in 1965.1* This figure
is adjusted at an annual rate of increase of
6 percent, yielding a 1968 estimate of $590
million.2 The Council estimated that a large
proportion of the paint was applied because
of factors such as humidity and chemicals.
They suggested that particulate air pollu-
tion may be responsible for about 5 percent
of the need for corrosion-inhibiting paints.
This factor was used to determine damages
due to air pollution and the cost of the paint,
estimated at $29.5 million. Added to this
is the labor required to apply the paint.
Labor is approximately 2.5 times the cost
of the paint as shown in the 1949 study by
Uhlig3** The total paint and labor gives
* Estimate supplied on March 11, 1965; contacted
again on April 24, 1968, but no' further work had
been done.
** This 2.5 labor factor still holds true, as can be
seen by comparing total recorded household repair
expenditures versus expenditures for materials in re-
cent years. In 1963, for example, the ratio was 2.3.
a total estimate of $103 million per year as.
the cost of painting steel structures because
of air pollution.
Commercial laundering, cleaning, and dye-
ing is another category of loss due to dirty
air. In 1963, commercial laundering, clean-
ing, and dyeing costs amounted to $3,475
million.4 Between 1958 and 1963, these costs
were increasing by 5 percent annually. The
adjusted figure for this category for 1968
thus becomes $4,350 million.
The Beaver Report found evidence sug-
gesting that one-third of laundry costs in
England were attributable to the effects of
air pollution.6 A damage factor for this
category for the United States for the cost
of commercial laundering, cleaning, and dye-
ing due to air pollution becomes $870 million.
Transportation delays is another good ex-
ample of an economic loss. Air pollution is
a major cause of reduced visibility. The
Civil Aeronautics Board reported that in
1962 low visibility resulting from smoke,
haze, dust, and sand in the air possibly
caused 15 to 20 plane crashes.7 Other costs
of low visibility include travel delays, diver-
sions, cancellations, and the cost of trans-
portation to individuals who wish to escape
polluted areas on weekend trips. Land trans-
portation costs may well include similar
losses. In air travel alone, the total costs of
diversion, cancellation delays, and crashes
were estimated at $803 million for I960.8
Today, the cost would be higher. If as little
as 5 to 10 percent is attributed to air pollu-
tion, $40 to $80 million or more is involved.
Automobile washing is another example.
Expenditures on automobile washing
amounted to $143 million in 1963.9 This cate-
gory grew by almost 10 percent per year be-
tween 1958 and 1963. Extending this rate,
yields an estimate of $210 million for car
washing in 1968. The $210 million is in-
creased by another 50 percent to $300 million
also, to adjust for the fact that washing by
the car owner is not included in the lower
figure.
The largest proportion of automobile
washing is probably caused by particulate
air pollution. A damage factor of 80 per-
cent is assumed for car washing, and ex-
penditures for automobile washing due to
80
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the effects of air pollution would be about
$240 million for 1968.
If this procedure could be repeated for
nonoverlapping categories of damage due
to particulate air pollution, additional esti-
mates of such damages could be developed.
B. EARLY ECONOMIC STUDIES
1. Pittsburgh
One of the first comprehensive surveys of
damage due to air pollution in the United
States was conducted in Pittsburgh during
the years 1912 to 1913 by the Mellon Insti-
tute. The estimates in the Pittsburgh in-
vestigation were based on economic losses
due to dustf all and smoke and were obtained
through interviews of individuals. The
items of cost and the total cost to the com-
munity were ascertained as shown in Table
5-1.
The Mellon Institute investigators arrived
at an annual per capita cost of $20 in 1913.
Health effects were not included; aesthetic
losses at the time were judged to be $5 per
person above the $20.10
Table 5-1.—ESTIMATED COSTS DUE TO AIR POL-
LUTION (MELLON INSTITUTE PITTSBURGH
STUDY.10
Causes of expenditure Cost
To smoke maker:
Imperfect combustion , .... $1,520,740
To individual:
Laundry bills 1,500,000
Dry cleaning bills . . . 750,000
To household:
Exterior painting . . ... 330,000
Sheet metal work 1,008,000
Cleaning and renewing wall paper . 550,000
Cleaning and renewing lace curtains 360,000
Artificial lighting .. . 84,000
To wholesale and retail stores:
Merchandise . . 1,650,000
Extra precautions 450,000
Cleaning . ... 750,000
Artificial lighting . . 650,000
Department stores 175,000
To quasi-public buildings:
Office buildings 90,000
Hotels . ... 22,000
Hospitals . . . 55,000
Total .. $9,944,740
2. Other Early Economic Studies
A comprehensive study of the economic
effects of air pollution in Great Britain is
described in the Beaver Report in 1954.6
This study considered both direct costs and
efficiency losses. The direct costs included
laundry and domestic cleaning; the clean-
ing, painting, and repair of buildings; the
corrosion of metals and consequent cost of
replacement and of providing protective
coverings; damage to goods; additional light-
ing; and extra hospital and medical services.
Efficiency losses were represented by the
effects on agriculture of damage to soil,
crops, and domestic animals; interference
with transport; and reduced human effi-
ciency due to illness.
Le Clerc, writing in 1961 about economic
losses due to air pollution, cited data from
France and Great Britain, as well as some
general data on economic losses in the United
States. The foreign data were quoted in
local monetary units, which have varied over
the years in relation to the value of the dol-
lar. Even those figures relating to the
United States are cited in the context of
the value of the dollar at the time of study.
Some of the data contained estimates on
medical services; others did not.11
In these two studies no attempt was made
to relate economic losses to the ambient par-
ticle concentration.
C. RECENT EFFORTS
1. Household Effects
More recent attempts to assess specific
economic losses due to air pollution have
been made by Michelson and Tourin in the
Upper Ohio River Valley and elsewhere.12-16
The investigators made a comparative analy-
sis of Steubenville, Ohio and Uniontown,
Pennsylvania. The socioeconomic and cli-
matic data were generally comparable,
whereas the air pollution levels, using par-
ticle concentration (/*g/m3) as an index,
were dissimilar. Uniontown had an annual
average of 115 /ig/m3, while Steubenville had
an annual average of 235 ju.g/m3.
Six categories of possible loss were studied
in each community:
1. Outside maintenance frequencies of
houses (cleaning painting, etc.) ;
81
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2. Inside maintenance frequencies of
houses and apartments (walls, win-
dows, drapes, curtains, Venetian
blinds, carpets, and furniture);
3. Laundering and dry cleaning of
clothing (with distinction between
summer and winter maintenance
practices);
4. Maintenance of women's hair and
facial care;
5. Inside maintenance of offices (clean-
ing and painting); and
6. Store operation and maintenance
(cleaning, painting, and other main-
tenance items; losses due to spoilage
of merchandise).
Data from only the first four categories
were used in the comparative analysis owing
to the heterogeneity of the establishments
interviewed and the small number of re-
spondents for the last two categories, nos.
5 and 6. It will be noted that these items
of cost are related for the most part to the
effects of particulate matter rather than to
all air pollutants.
For each loss category three types of data
were sought:
1. Activity frequency;
2. Incidence (i.e., the proportion of the
population to which various frequen-
cies were applicable); and
3. Socioeconomic characteristics (i.e.,
household income, educational level).
Questionnaires were designed separately for
each area of activity to collect accurate in-
formation on frequency of maintenance op-
erations. Although income data were ob-
tained in steps of $2000, only two income
categories were used in the final compara-
tive analysis: "less than $8000" and "over
$8000." The maintenance frequency factor
was calculated, and the frequency factors
were converted into dollar values.
Table 5-2 shows the calculated extra per
capita and total costs incurred by Steuben-
ville as a result of air pollution.
The Upper Ohio River study also included
a third city, Martins Ferry, Ohio, where the
particle concentrations were roughly mid-
way between those of the first two cities.
Table 5-2.—DIFFERENCES IN CLEANING COSTS
INCURRED AT STEUBENVILLE AND AT UN-
IONTOWN.12
Gross cost
Activity Differences
(Steubenville over Union town)
Per
Annual Capita*
Outside maintenance of
houses $ 640,000 $17
Inside maintenance of
houses and apartments 1,190,000 32
Laundry and dryclean-
ing 900,000 25
Hair and facial care 370,000 10
Total
$3,100,000
$84
* Based on estimated 1959 population of 36,400.
The average frequency of maintenance op-
erations in Martins Ferry fell almost pre-
cisely midway between those in Steuben-
ville and Uniontown.
The curve relating costs of air pollution
and suspended particle concentrations, the
latter being used as an index of air pollu-
tion, was found by these investigators to be
essentially a straight line. Using these data,
the authors extrapolated the straight line
of Figure 5-1 back to the average particle
concentration of the rural stations of the
National Air Sampling Network (NASN).
4.5i
O 4.0 •
K 3.5
O
ss-
3.0 •
212.5
<->S
z-e
|3l.5
ui
Z 1.0
D BASED ON TWO PI LOT STUDIES
(10 MAINTENANCE ITEMS EACH)
•BASED ON TOTAL OF 23 ITEMS
(UPPER OHIO RIVER STUDY
DATA ONLY)
1 STEUBENVILLE
2 MARTINS FERRY
3 UNIONTOWN
4 SUITLAND
5 ROCKV1LLE
6 FAIRFAX CITY
0 25 50 75 100 125 150 175 200 250 300
MEAN ANNUAL SUSPENDED PARTICLES (fig / m3)
FIGURE 5-1. Maintenance Frequency as a Function
of Particle Concentration in the Upper Ohio River
Valley and the National Capital Area (for House-
holds of Above-average Income). (This figure
shows that maintenance frequency increases al-
most linearly with the mean suspended particle
concentrations.)
82
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The mean annual rural station concentra-
tion of suspended particulate matter for
1959 to 1961 was 25 /x/m3.
A similar investigation of comparative
costs due to air pollution was conducted by
Michelson and Tourin in the metropolitan
Washington, D.C., area in 1967. The char-
acter of metropolitan Washington differs
markedly from that of Steubenville, the lat-
ter having much heavy industry (steel mills,
etc.). The Washington pilot study was has 3d
on a selection of families in private dwellings
only.
Four communities of the Washington, B.C.
area (Rockville- Maryland; Suitland, Mary-
land; Hyattsville, Maryland; and Fairfax
City, Virginia) were originally selected for
study because they represented extremes in
particle concentrations for outlying areas.
At the time, they all had a large proportion
of middle-income families. The returned
questionnaires were processed (according to
the replies) by income group. Since it was
expected that families in the very low and
very high income brackets would be rela-
tively insensitive to particulate pollution,
only the data in the $10,000-to-$14,000
bracket were utilized. Deficiencies in the air
quality data for Hyattsville precluded its in-
clusion in the analysis.
Results from the three suburban Wash-
ington communities compared quite favor-
ably with the results from the Upper Ohio
River Valley study on the ten items which
were common to both studies. Figure 5-1
shows the relationship between suspended
particle concentrations and maintenance fre-
quency ratio (urban/rural) for the two
studies combined, as well as for the Upper
Ohio River Valley study alone.
It may be noted that in both sets of data
the association between the maintenance fre-
quency ratios and suspended particulates is
taken to be linear over the range of the ac-
tual data, rather than an expected leveling
out of the "curve" at extremely high con-
concentrations of particulates. Maintenance
frequency ratios were not translated into
costs in the suburban Washington communi-
ties because of widely different socioeco-
nomic and time differences between the two
study areas. The importance of the studies
lies not so much in the estimates of cost,
which are likely to vary in place and time,
but in the estimates of differences in main-
tenance. It should be noted that the use of
common cost/maintenance operation has the
effect of understating the true difference in
expenditures for the items studied between
the two areas.
The Michelson-Tourin studies have sug-
gested one approach to the problem of esti-
mating the costs of some of the effects of
particulate air pollution. The results of in-
vestigations to date are highly suggestive of
the existence of a significant relationship be-
tween the costs of household and personal
maintenance and the existence of air pollu-
tion.
A word of caution in the interpretation
of these results is in order. It is well known
that causation and statistical correlation are
not one and the same. There are a number
of other factors, not investigated in the
studies of Michelson and Tourin, which could
be highly correlated with air pollution, and
which could be casually related to the fre-
quency with which the various personal hy-
giene and property maintenance routine
studied are performed. For example, highly
urbanized areas are likely to have both rela-
tively high levels of air pollution and a rela-
tive abundance of the materials and skills
necessary for the performance of hygiene
and maintenance operations (e.g., dryclean-
ing establishments, beauticians, etc.). More
work is needed to find out unambiguously
just what forces are operating.
2. Property Value Studies
In 1967 the results of investigations into
the effect of air pollution on property and
other values in St. Louis, Syracuse, and
Philadelphia were published in a book by
Dr. Ronald Ridker entitled Economic Costs
of Air Pollution—Studies in Measurement.17
The studies were somewhat inconclusive;
they dealt generally with air pollution effects
and did not attempt to isolate the effects of
particulates. Nevertheless, the effort repre-
sents an important methodological milestone
because it describes some important attempts
to determine the economic extent of air pol-
lution damage and includes some practical
83
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suggestions for the guidance of investiga-
tors. For example, in the chapter on "Soil-
ing and Material—Damage Studies," Dr.
Ridker expresses pessimism with respect to
the value of additional studies based on
analysis of currently available data and, cit-
ing the high cost of surveys, proposes as
an alternative "a special type of experimen-
tal approach to the gathering of the relevant
economic information."
The recommended approach would seek to
establish the physical and biological effects
of various types and combinations of air pol-
lution in varying concentrations and dura-
tions. It would include study of the effects
of weather conditions and attempt to estab-
lish predictive relationships that could de-
scribe the amount of damage that would re-
sult from specific exposure conditions. The
resulting damage functions could then be
subjected to economic analysis in an effort
to translate effects into costs.
Ridker's studies of air pollution and prop-
erty values were limited to cross section
studies. They tended to show an inverse re-
lationship between property values and air
pollution levels as measured by mean values
for sulfation rates.
Other investigators, including T. D.
Crocker,18 have demonstrated that the dif-
ference in land value between a polluted and
a nonpolluted area is an appropriate measure
of potential gain from an abatement policy.
The results of property-value studies ap-
pear encouraging in that they are a step in
the direction of defining a function relation-
ship between reductions in air quality and
economic loss. They supplement the studies
of effects of air pollution described previ-
ously.
3. Productivity Studies
Many feel and some are convinced that
air pollution, and especially the combination
of suspended particulates with sulfur di-
oxide, is associated with an increasing inci-
dence of lung and respiratory ailments and
heart disease.19-20
To the extent that particulate air pollu-
tion affects the respiratory tract and pro-
duces or contributes to illness among the
working population, it may substantially re-
duce human productivity and result in eco-
nomic losses. Economic losses would result
from work-loss days, reduced worker pro-
ductivity, and a shortened productive work
life. At this time, it is not possible to do
more than speculate about the possible mag-
nitude of this possibly significant economic
loss.
Efforts to provide useful economic esti-
mates of the effects of disease have long been
a major problem for economists. Neverthe-
less, estimates have been made for a number
of diseases and agreement appears to be de-
veloping on measurement methods. The
most economically useful measure of the
effects of reduced productivity would be the
capitalized value or the present discounted
value of gross lost production.21-22 Progress
is reported in methods of valuing a human
life, apart from livelihood. All efforts to con-
struct acceptable estimates of the costs of
poor health or early death attributable to air
pollution depend on the results of research
that can establish dependable cause and ef-
fect relationships.
D. SUMMARY
The cost of painting steel structures be-
cause of air pollution, particularly due to
particulate matter, has been estimated at
about $100 million a year. The annual cost
of commercial laundering, cleaning, and dye-
ing due to air pollution is estimated at $850
million. The adverse effects of air pollution
on air travel were estimated minimally at
$40-$80 million in 1960; obviously, they
would be greater today. Expenditures for
car washing, including washing by the car-
owner involved, due to air pollution are esti-
mated at about $250 million in 1968. This
assumes the principal cause of frequent car
washing is particulate air pollution. The
Michelson and Tourin studies, despite their
stated deficiencies, reveal a general relation-
ship between levels of particulate air pollu-
tion and increased frequency of household
maintenance operations. Unfortunately, it
is not readily possible to convert these re-
lationships into cost relationships that would
be uniformly applicable to all communities.
Studies of air pollution and residential
property values, while limited by data avail-
ability, strongly suggest that a statistically
84
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significant inverse relationship may exist
between higher levels of particulate and
other air pollution and residential property
values.
Efforts to provide useful economic infor-
mation about the effects of air pollution
(particulates) on human health and pro-
ductivity losses are incomplete because they
depend on results of other research efforts
aimed at the establishment of dependable
cause and effects relationships.
It may be possible to develop acceptable
gross estimates of air pollution damage
based on analysis within a group of non-
overlapping damage categories- as suggested
in the introduction to this chapter. If such
efforts are carried out with care, they may
provide useful guides to policy determina-
tion. Considerably more attention needs to
be given to the physical and biological ef-
fects of air pollution before definitive esti-
mates of the economic costs of air pollution
effects can be made.
Such estimates are not the final step, how-
ever. It will then be necessary to determine
the costs averted (or benefits) by a par-
ticular mechanism or program of air pol-
lution control, in relation to the costs of
control.
E. REFERENCES
I. Steel Structures Painting Council, Pittsburgh,
Pa., Correspondence dated March 11, 1965.
2. "Statistical Abstract of the United States:
1967." 88th edition, U.S. Bureau of the Census,
Washington, B.C., 1967, Table 1067.
3. Uhlig, Herbert H., "The Cost of Corrosion to
the United States." Chem. Eng. News, Vol. 27,
pp. 2764-2767, 1949.
4. "Statistical Abstract of the United States, 1967."
88th edition, U.S. Bureau of the Census, Table
1193.
5. "U.S. Census of Business: 1963, Selected Serv-
ices." Vol. 6, U.S. Dept. of Commerce, Washing-
ton, D.C., 1963, Table I.
6. "Committee on Air Pollution Report, A Report
to the Minister of Housing and Local Govern-
ment, Sir Hugh Beaver, Chairman." Her Maj-
esty's Stationery Office, London, 1954.
7. "The Polluted Air We Breathe." American Fed-
erationist, Vol. 71(2), pp. 6-11, 1964.
8. Fromm, Gary, "Civil Aviation Expenditures,"
In: Measuring Benefits of Government Invest-
ments, The Brookings Institution, Washington,
D.C., 1965, Table 2.
9. "U.S. Census of Business: 1963, Selected Serv-
ices Area Statistics," Vol. 7, U.S. Dept. of Com-
merce, Washington, B.C., 1963, Table 1-8.
10. O'Connor, J. J., Jr. "The Economic Cost of the
Smoke Nuisance to Pittsburgh." University of
Pittsburgh, Mellon Institute of Industrial Re-
search and School of Specific Industries, Pitts-
burgh, Pa., Smoke Investigation Bulletin 4, 1913.
11. Le Clerc, E. "Economic and Social Aspects of
Air Pollution." In: Air Pollution (World Health
Organization), Columbia University Press, New
York, 1961, pp. 279-291.
12. Michelson, I. and Tourin, B. "Comparative
Method for Studying Cost of Air Pollution."
Public Health Rept. Vol. 81(6), pp. 505-511,
June 1966.
13. Michelson, I. and Tourin, B., "Report on Study
of Validity of Extension of Economic Effects
of Air Pollution Data from Upper Ohio River
Valley to the Washington, D.C. Area." Public
Health Service Contract PH 27-68-22, Novem-
ber 8, 1967.
14. Michelson, I. and Tourin, B., "Household Cost
of Living in Polluted Air Versus the Cost of Con-
trolling Air Pollution in the Twin Kansas Cities
Metropolitan Area." Public Health Service Con-
tract PH27-68-21.
15. Michelson, I. and Tourin, B., "Household Cost
of Living in Polluted Air in the Washington
Metropolitan Area." Washington, D.C. Metro-
politan Area Air Pollution Abatement Confer-
ence, January 1968.
16. Huey, N. "Economic Benefit from Air Pollu-
tion Control." Preprint. (Presented at the New
York-New Jersey Metropolitan Area Air Pollu-
tion Abatement Activity, February 5, 1968.)
17. Ridker, R. G., "Economic Costs of Air Pollu-
tion: Studies in Measurement." Frederick A.
Praeger, New York, 1967.
18. Crocker, T. D., "Some Economic Aspects of Air
Pollution Control with Special Reference to Polk
County, Florida." Research Report to U.S. Pub-
lic Health Service, Grant AP-00389.
19. Committee on Pollution, National Research
Council, "Waste Management and Control." A
Report to the Federal Council for Science and
Technology, National Academy of Science, Na-
tional Research Council, Washington, D.C., Pub.
1400, 1966.
20. "Restoring the Quality of Our Environment."
Environmental Pollution Panel, President's Sci-
ence Advisory Committee, The White House,
November 1965.
21. Weisbrod, B. A., "Economics of Public Health."
University of Pennsylvania Press, Philadelphia,
1961.
22. Klarman, H. E., "Syphillis Control Programs."
In: Measuring the Benefits of Government In-
vestments, R. Dorfman (ed.), The Brookings
Institution, Washington, D.C., 1965.
85
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Chapter 6
EFFECTS OF ATMOSPHERIC PARTICULATE
MATTER ON VEGETATION
-------
Table of Contents
Page
A. INTRODUCTION , 89
B. EFFECTS OF SPECIFIC DUST ON VEGETATION 89
1. Cement-Kiln Dust 89
a. Direct Effects 89
(1) Nature of Dust Deposition 89
(2) Range of Effects . . 91
(3) Dust Components Involved . 92
b. Indirect Effects . . 93
2. Flourides 93
3. Soot . . 94
4. Magnesium Oxide . 94
5. Iron Oxide . 94
6. Foundry Dusts . . ... 94
7. Sulfuric Acid Aerosols . . 94
C. EFFECTS OF DUSTS ON ANIMALS BY INGESTION OF
VEGETATION . 95
D. SUMMARY 95
E. REFERENCES . . 96
List of Figures
Figure
6-1 Bean Plants Dusted with Cement-Kiln Particles . 90
6-2 Cement-Kiln Dust on Fir Tree Branches 91
6-3 Cement-Kiln Dust on Fir Tree Branches . ..91
-------
Chapter 6
EFFECTS OF ATMOSPHERIC PARTICULATE MATTER ON VEGETATION
A. INTRODUCTION
Little is known about the effects of par-
ticulate matter on vegetation and little re-
search has been done on the subject. There
has been far more research on gaseous pol-
lutants, many of which are readily recog-
nized as serious toxicants to a variety of
plants. Published experimental results,
mostly from Germany, are confined princi-
pally to settleable dusts emitted from the
kilns of cement plants. There are a few re-
ports on effects of fluoride dusts, soot' and
particulate matter from certain types of
metal processing. Sulfuric acid aerosols have
also been studied in Los Angeles, where depo-
sition of acid droplets has injured the
leaves of vegetation. Most of the research
was related to the direct effects of dusts on
leaves, twigs, and flowers as opposed to in-
direct effects from dust accumulation in the
soil. Because of the dearth of experimental
results, the tenor of many reports is directed
as much to the question, "Do dusts in fact
have deleterious effects on plants ?" as to the
question of extent of injury. It is thus rea-
sonable to anticipate some disagreement.
Such information as there is refers to spe-
cific dusts rather than to the conglomerate
that is usually measured as urban or rural
dustfall (Chapter 1). The various specific
pollutant dusts and their injurious effects
on vegetation are discussed in the following
sections.
B. EFFECTS OF SPECIFIC DUSTS
ON VEGETATION
1. Cement-Kiln Dust
Cement-kiln dust is the dust contained in
waste gases from the kilns and is not derived
directly from processing of cement. It is ap-
parent from some reports, however, that the
composition of wastes from different kilns
operating at different efficiencies varies con-
siderably, and at times the effluents may con-
tain cementitious materials that more prop-
erly belong in the finished product. Another
important factor to consider is that literature
reports describing effects of dust deposited
on various plants in the field relate to kiln-
stack materials, whereas experimental dusts
applied in laboratory or field studies were
taken from various collectors in the waste-
gas system between the kiln and the stack.
Differences in results that may be due to this
factor have not been reconciled.
ft. Direct Effects
(1) Nature of Dust Deposition.—Most of
the reports concerning harmful effects of
cement-kiln dust on plants stress the fact
that crusts form on leaves, twigs, and flow-
ers. As early as 1909-1910 Peirce* and
Parish 2 noted in California that settled dust
in combination with mist or light rain formed
a relatively thick crust on upper leaf surfaces
of affected plants. The crust would not wash
off and could be removed only with force.
The central theme about which Czaja 3~6
builds his case for harmful effects is the crust
formation in the presence of free moisture.
He states that crust is formed because some
portion of the settling dust consists of the
calcium silicates which are typical of the
clinker (burned limestone) from which ce-
ment is made. When this dust is hydrated on
the leaf surface, a gelatinous calcium silicate
hydrate is formed, which later crystallizes
and solidifies to a hard crust. When the crust
is removed, a replica of the leaf surface is
often found, indicating intimate contact of
dust with the leaf. The relatively thick crust
formed from continuous deposition is con-
fined to the upper leaf surface of deciduous
species but completely encloses needles of
89
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conifers. Prolonged dry periods during the
time dust is deposited provide no opportunity
for hydration, and crusts are not formed.
Dust deposits which are not crusted are
readily removed by wind or hard rain.
Darley 3 applied kiln dusts of particle size
less than 1
-------
FIGURE 6-2. Cement-kiln Dust on Fir Tree Branches/
(Incrustation has built up on the older twigs of a
fir tree exposed to a cement-kiln dustfall probably
in excess of 1 mg/m2-day. Needles have fallen
prematurely.)
The net effect was a shortening of each suc-
ceeding year's flush of growth. A dead tree
had heavy incrustations on the branches
(Figure 6-3).
(2) Range of Effects.—PeirceJ demon-
strated that incrustations of cement-kiln dust
on citrus leaves interfered with light re-
quired for photosynthesis and reduced starch
formation. This was later confirmed by
Czaja 5 and Bohnee in a variety of plants.
More recently, Steinhubel7 compared starch
reserve changes in undusted common holly
leaves and those dusted with foundry dust.
He concluded that the critical factor in starch
formation was the light absorption by the
dust layer, and that the influence on tran-
spiration or over-heating of leaf tissue was
FIGURE 6-3. Cement-kiln Dust on Fir Tree Branches.4
(Very heavy incrustation on a branch of a dead
fir tree exposed to cement kiln dust (dustfall rates
probably in excess of 0.1 mg/cma-day).)
of minor significance. Lecenier and Piquer
(see Czaja 5) attributed the reduced yields
from dusted tomato and bean plants to in-
terference with light imposed by the dust
layer. Darley 3 demonstrated that dust de-
posited on bean leaves in the presence of free
moisture interfered with the rate of carbon
dioxide exchange, but no measurements of
starch were made.
Czaja 5 stated that the hydration process
of crust formation released calcium hydrox-
ide. The hydrated crusts gave solutions of
pH 10-12. Severe injury of naturally dusted
leaves, including killing of palisade and pa-
renchyma cells, was revealed by microscopic
examination. The alkaline solutions pene-
91
-------
trated stomata on the upper leaf surface,
particularly the rows of exposed stomata on
needles of conifer species, and injured the
cells beneath. Czaja 5 stated that' on broad-
leaved species with stomata only on the lower
leaf surface, the alkaline solutions first sa-
ponified the protective cuticle on the upper
surface, permitting migration of the solu-
tion through the epidermis to the palisade
and parenchyma tissues. Typical alkaline pre-
cipitation reaction with tannins, especially
in leaves of rose and strawberry, was evi-
dence that calcium hydroxide penetrated the
leaf tissue. Bohne6 described similar "cor-
rosion" of tissues under the crust formed on
oak leaves.
Czaja 8 has presented good histological evi-
dence that stomata of conifers may be
plugged by dust, preventing normal gas ex-
change by the leaf tissue. Uninhibited ex-
change of carbon dioxide and oxygen by leaf
tissue is necessary for normal growth and
development.
Bohne6 reported a marked reduction of
growth of poplar trees located about one mile
from a cement plant after production in the
plant was more than doubled. The change in
growth rate was determined by the width of
annual rings in the wood. Darley 3 observed
a reduction of spring growth elongation on
conifers in Germany, where the oldest nee-
dles were incrusted. He also noted that plants
were stunted and had few leaves in the heav-
ily dusted portions of an alfalfa field down-
wind from a cement plant in California.
Plants appeared normal in another part of
the field where there was no visible dust de-
posit. The dusted plants were also heavily in-
fested with aphis and it was not clear wheth-
er the poor growth was due to the aphis
feeding or a direct effect of the dust. Ento-
mologists suggested that the primary effect
of the dust may have been to eliminate aphid
predators, thus encouraging high aphid popu-
lations, which in turn cause poor plant
growth because of their feeding.
Anderson9 observed in New York that
cherry fruit set was reduced on the side of
the tree nearest a cement plant. He demon-
strated that the dust on the stigma prevented
pollen germination. Schonbeck10 treated a
field planting of sugar beets biweekly with
2.5 g/m2 of dust and observed that infection
by leaf-spotting fungus, Cercospora beticola,
was significantly greater than in nondusted
plots. He postulated that the physiological
balance was altered by dust increasing sus-
ceptibility to infection.
Pajenkamp" reviewed the unpublished
work of several German investigators, some
of whom had applied dust artificially to test
plants, and stated that he was opposed to the
view that dusts are harmful to plants. He
concluded that depositions of from 0.75 g/m2-
day to 1.5 g/m2-day (the latter amount rep-
resenting the maximum that might be found
in the vicinity of a cement factory) had no
harmful effect on plants.
Raymond and Nussbaum 12 also stated that
cement dusts have little effect on wild plants.
On the other hand, Guderian 13 and Wentzel"
disagreed with Pajenkamp and stated that
the limited evidence at best presented a con-
tradictory picture and that Pajenkamp had
not cited Czaja's earlier work.5-8-15-16 They
also pointed out that a deposit of 1.5 g/m2-day
was not maximum, since other workers had
found up to 2.5 g/m2-day, and Bohne6 has
since reported weekly averages of up to 3.8
g/m2-day.
According to Czaja,5 Ewert concluded that
cement-kiln dust did not clog the stomata and
that the crust might have a beneficial effect
as protection against transpirational losses
and a defense against fungi. Czaja also noted
that the interpretation of evidence by Ewert
is open to question because control plants
were heavily infested with flea beetles, while
test plants were not.
(3) Ditst Components Involved—Detail on
the injury to be expected from certain ce-
ment-kiln precipitator dusts was given by
Czaja.8 His work is based on comparisons of
chemical composition of dusts and resultant
injury to leaf cells of a sensitive moss plant,
Mnium punctatum. A cut leaf was mounted
in water on a microscope slide, and dust was
placed in contact with the water at the edge
of the cover slip. Any effect of the resultant
solution on leaf cells could be observed di-
rectly. Eighteen of the dusts tested in this
way fell into the following categories:
1. No permanent injury to living cells,
but some plasmolysis from the con-
92
-------
centration effect of the solution;
2. Slight injury to readily accessible
cells, disruption of the cytoplasm, and
displacement of chloroplasts; and
3. Severe injury to all cells of the leaflet.
Dusts were further described as follows:
group 1, pH of 9.5-11.5, a relatively high rate
of carbonation, and intermediate amount
(19-29 percent) of clinker phase (calcium
silicates), and characterized by a high (36-
79 percent) amount of secondary salts; group
2, pH about 11, a high rate of carbonation, a
lower (13-16 percent) clinker phase and
characterized by a high (81-85 percent) pro-
portion of raw feed; group 3, pH 11-12, a
very slow carbonation rate- and characterized
by a high (17-49 percent) clinker phase. The
greater injury was thus related to the larger
amounts of clinker phase, which in turn re-
sulted in higher and prolonged alkalinity. But
Czaja also pointed out that the composition
of dusts within the three groups was not con-
sistent, and that, although not yet demon-
strated, the constituents of a given dust un-
doubtedly influence one another.
In short-term experiments of two to three
days, Darley 3 dusted the primary leaves of
bean plants with fractionated precipitator
dust obtained from Germany. The dust con-
tained relatively high amounts of potassium
chloride, KC1. When a fine mist was applied
to dusted leaves, a portion of the leaf tissue
was killed (up to 29 percent) and it was pre-
sumed that the action was due to KC1. In
later experiments4 other fractions of the
same dust containing very little KC1 caused
an almost equivalent amount of injury, thus
indicating that KC1 was apparently not the
only factor involved. Current laboratory in-
vestigations with different particle-size frac-
tions of precipitator dusts collected around
the United States have demonstrated varying
degrees of injury to bean leaves when dew is
formed on the leaves. There appears to be no
effect from dry dusts alone. Inasmuch as
these dusts contain very little clinker phase,
it is apparent that some components other
than those connected directly with hydration
of calcium silicates may also be responsible
for injury.
(4) Indirect Effects.—Pajenkamp " re-
ported on unpublished work by Scheffer in
Germany during two growing seasons, indi-
cating that even considerable quantities of
precipitator dust applied to the soil surface
brought about no harmful effects and no
other lasting effects on growth or crop yield
of oats, rye grass, red clover, and turnips.
The dust had a content of about 29.3 percent
limestone (analyzed as lime, CaO) and 3.1
percent potassium oxide, K20. The maximum
rate of deposit was 0.15 mg/cm2-day. Discon-
tinuous dustings were made at 0.25 mg/cm2-
day to give an average of 0.075 mg/cm2-day.
In one year, the yield of red clover and the
weight of turnips were higher in the dusted
plots, although the yield of leaves in the latter
crop was reduced. Acid manuring of the soil
appeared to increase yield but the interaction
of dusting and manuring was not understood.
While Scheffer et al." found no direct in-
jury to plants, they indicated that there
might be indirect effects through changes in
soil reaction, which in time might impair
yield.
Stratmann and van Haut1S dusted plants
with quantities of dust ranging from 0.1
mg/cm2-day to 4.8 mg/cm2-day; dust falling
on the soil caused a shift in pH to the alkaline
side, which was unfavorable to oats but fa-
vorable to pasture grass.
2. Fluorides
Particles containing flouride appear to be
much less injurious than gaseous flourides to
vegetation. Pack et al.w reported that 15
percent of gladiolus leaf was killed when
plants were exposed four weeks to 0.79 jug/m3
fluoride as HF, but no necrosis developed
when plants were exposed to fluoride aerosol
averaging 1.9 /ig/m3 fluoride. Inasmuch as the
material was collected from a gas stream
which was treated with limestone and hy-
drated lime, the aerosol was probably calcium
fluoride. Moreover, when the accumulated
levels of fluoride in leaf tissues were about
the same, whether from gas or particulate,
injury from the latter was much less.
McCune et al.20 reported an increase of
only 4 mm tipburn on gladiolus exposed to
cryolite (sodium aluminum fluoride dust),
wherein the washed leaf tissue from this
treatment showed an accumulation of 29 ppm
93
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fluoride. A 70-mm increase in tipburn would
have been expected if a similar accumulation
had occurred from exposure to HF. Except
for the slight tipburn noted above, these
authors found that cryolite produced no vis-
ible effects on a variety of plants nor did it
reduce growth or yield.
It is evident from the work of McCune
et al.20 that fluoride in plant tissue is accumu-
lated from cryolite treatment, but the rate of
accumulation is much slower than would be
expected from a comparable treatment with
HF. For example, when comparing washed
leaf samples, exposure of gladiolus to HF for
three days at 1.01/tg/m3 fluoride resulted in
an accumulation of 26.4 ppm fluoride, where-
as only 34 ppm was accumulated from an ex-
posure to cryolite for 40 days at 1.7/xg/m3
fluoride. Pack et al.w reported only one-third
as much fluoride accumulated from particu-
late matter as from gaseous forms.
Both the investigations cited above indi-
cate that much of the particulate matter re-
mains on the surface of the leaf and can be
washed off, although that which remains
after washing is not necessarily internal
fluoride. Reduced phytotoxicity of particulate
fluoride is ascribed in part to the inability of
the material to penetrate the leaf tissue. In
addition, McCune et al.20 suggest that in-
activity of particles may be due to their in-
ability to penetrate the leaf in a physiologi-
cally active form.
3. Soot
Jennings 21 noted the suggestion that soot
may clog stomata and prevent normal gas ex-
change but that most investigations tend to
discount this effect. Microscopic examination
failed to show enough clogging of stomata on
leaves of shade trees (broad-leaved species)
to be significant. He further states that inter-
ference with light can be more serious but
he offers no data from critical experiments to
substantiate this theory.
A well-illustrated report by Berge22 showed
plugged stomata on conifers growing near
Cologne, Germany. He also stated that
growth was adversely affected.
Necrotic spotting was observed on leaves
of several plants where soot from a nearby
smokestack had entered a greenhouse.23 The
necrosis was attributed to acidity of the soot
particles. Plants outside the greenhouse were
not damaged, possibly because the particles
had been removed by rain before severe in-
jury could occur.
4. Magnesium Oxide
The possible indirect effect on vegetation
of magnesium oxide falling on agricultural
soils was reported by Sievers.24 He noted
poor growth in the vicinity of a magnesite-
processing plant in Washington. Experi-
ments were designed to grow plants in soil
collected at various distances from the proc-
essing plant, in normal soil and in soil to
which magnesium oxide was added. Suppres-
sion of plant growth was demonstrated with
the high levels of magnesium. After the proc-
essing plant ceased operation, injury to crops
in the area became less pronounced, indica-
ting that the injurious effect was not a per-
manent one.
5, Iron Oxide
Berge,25 in Germany, dusted experimental
plots with iron oxide at the rate of 0.15
mg/cm2-day over one- to ten-day intervals
through the growing season for six years.
The plots were planted with cereal grains or
turnips, and effects of treatment on the pri-
mary product, on straw, and on leaves were
noted. No harmful effect of the dust was de-
tected on either crop. There was a tendency
for improvement of yields of grain and tur-
nip roots, but this was not statistically sig-
nificant.
6. Foundry Dusts
Changes in starch reserves were compared
in common holly leaves, untreated, and
treated with dusts emitted from foundry
operations.6 The critical factor was the
amount of light absorbed by the dust layer,
and the influence on transpiration or over-
heating of leaf tissue was of minor signifi-
cance. These observations agree with some of
those reported above on the range of effects
of cement-kiln dust on vegetation.
7. Sulfuric Acid Aerosols
These particles too may settle on plants
and cause injury. They are not discussed here,
however, as the subject is covered in some
94
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detail in Air Quality Criteria for Sulfur
Oxides, a companion document.
C. EFFECTS OF DUSTS ON ANIMALS BY
INGESTION OF VEGETATION
Particles which contain chemical compo-
nents detrimental to animal health may be
assimilated through ingestion of plant ma-
terials. The toxic components may be ab-
sorbed into the plant tissues or may remain
as a surface contaminant on the plants. When
evaluating the potential harm to animals
from ingested vegetation, both absorbed and
deposited particles should be considered.
Fluorosis in animals has been reported
from ingestion of vegetation covered with a
fluoride-containing particulate matter.26 In-
jury occurs when absorbed plus deposited
fluoride on the plants reached 40 ppm to 50
ppm. Arsenic poisoning of cattle and sheep
has occurred from ingestion of arsenic-con-
taining particles settled on vegetation.27
D. SUMMARY
There has been relatively little research on
the effects of particulate matter on vegeta-
tion, and most of the experiments done to
date have dealt with specific kinds of dusts
rather than the conglomerate mixture nor-
mally encountered in the atmosphere.
The significance of dusts as phytotoxicants
is not yet entirely clear but there is con-
siderable evidence that certain fractions of
cement-kiln dusts adversely affect plants
when naturally deposited on moist leaf sur-
faces. Dry cement-kiln dusts appear to have
little deleterious effect, but in the presence
of moisture the dust solidifies into a hard ad-
herent crust which can damage plant tissue
and inhibit growth. Moderate damage has
been observed on the leaves of bean plants
dusted at the rate of about 0.47 mg/cm2-day
(400 tons/mi2-month) for two days and fol-
lowed by exposure to naturally occurring
dew. Similarly, a marked reduction in the
growth of poplar trees one mile from a
cement plant was observed after cement pro-
duction was more than doubled. At levels in
excess of 0.1 mg/cm2-day (85 tons/mi2-
month), incrustations have been observed on
the branches of fir trees, with the result that
needles fell prematurely, shortening each
succeeding year's flush of growth. Although
the mechanism by which injury occurs is not
entirely understood, it is possible that the
crust intercepts the light needed for photo-
synthesis and starch formation, causes alka-
line damage to tissues, and prevents normal
gas exchange in leaf tissues. Injury due to
the direct effect of high pH on cell constitu-
ents does occur. Plugging of stomata and
reduced growth of trees may occur within a
short distance of cement plants.
It should be noted, however, that the harm-
ful effect of cement dusts on vegetation is not
fully substantiated and has been questioned
by some workers. The controversy that sur-
rounds this subject is not surprising in view
of the limited research to date. In addition,
not all studies have been carried out under
identical conditions or with dusts of the same
composition. Studies of the effects of cement-
kiln dusts deposited on the soil also raise
questions. Some investigators report no
harmful effects at levels from 0.15 mg/cm2-
day to 0.75 mg/cm2-day (130 tons/mi2-month
to 640 tons/mi2-month), while others report
that concentrations from 0.1 mg/cm2-day to
4.8 mg/cm2-day (86 tons/mi2-month to 4,000
tons/mi--month) cause shifts in the soil alka-
linity which may be favorable to one crop but
harmful to another.
Fluorides in particulate form are less dam-
aging to vegetation than gaseous fluorides.
Fluoride may be absorbed from depositions
of soluble fluoride on leaf surfaces. However,
the amount absorbed is small in relation to
that entering the plant in gaseous form. The
fluoride from particulates apparently has
great difficulty penetrating the leaf tissue in
a physiologically active form. The research
evidence suggests that few if any effects oc-
cur on vegetation at fluoride particulate con-
centrations below about 2/*g/m3. Concentra-
tions of this magnitude can be found in the
immediate vicinity of sources of fluoride par-
ticulate pollution, but they are rarely found
in urban atmospheres. Fluorides absorbed
or deposited on plants may be detrimental to
animal health. Fluorosis in animals has been
reported due to the ingestion of vegetation
covered with particulates containing fluo-
rides. In a similar manner arsenic poisoning
of cattle and sheep has occurred from in-
95
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gestion of arsenic-containing particulate that
had settled on vegetation.
Soot may clot stomata and may produce
necrotic spotting if it carries with it a soluble
toxicant, such as one with excess acidity.
Magnesium oxide deposits on soils have been
shown to reduce plant growth, while iron
oxide deposits appear to have no harmful ef-
fects and may be beneficial. Sulfuric acid
aerosols will cause leaf spotting. The levels
at which these materials may produce a toxic
response are not well defined.
E. REFERENCES
1. Peirce, G. J. "An Effect of Cement Dust on
Orange Trees." Plant World, Vol. 13, pp. 283-288,
1910.
2. Parish, S. B. "The Effects of Cement Dust on
Citrus Trees." Plant World, Vol. 13, pp. 288-291,
1910.
3. Darley, E. F. "Studies on the Effect of Cement-
Kiln Dust on Vegetation." J. Air Pollution Con-
trol Assoc., Vol. 16, pp. 145-150, 1966.
4. Darley, E. F. Unpublished data.
5. Czaja, A. T. "Uber das Problem der Zementstaub-
wirkungen auf Pflanzen." Staub, Vol. 22, pp. 228-
232, 1962.
6. Bohne, H. "Schadlichkeit von Staub aus Ziment-
werken fur Waldbestande." Allgem. Forstz., Vol.
18, pp. 107-111, 1963.
7. Steinhubel, G. "Zmeny v skrobovych rezervach
listov cezminy po umelom znecisteni pevnym po-
praskom." Biologia, Vol. 18, pp. 23-33, 1962.
(Abstract, in German, pp. 32-33, with the title:
Veranderungen in den Starkereserven der Blat-
ter der gemeinen Stechpalme nach einer kunst-
lichen Verunreinigung durch Staub.)
8. Czaja, A. T. "Uber die Einwirkung von Stauben,
speziell von Zementofenstaub auf Pflanzen."
Angew. Botan., Vol. 40, pp. 106-120, 1966.
9. Anderson, P. J. "The Effect of Dust from Cement
Mills on the Setting of Fruit." Plant World, Vol.
17, pp. 57-68, 1914.
10. Schonbeck, H. "Beobachtungen zur Frage des
Einflusses von industriellen Immissionen auf die
Krankbereitschaft der Pflanze." Berichte der
Landesanstalt filr Bodennutzungsschutz (Bo-
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11. Pajenkamp, H. "Einwirkung des Zementofen-
staubes auf Pflanze and Tiere." Zement-Kalks-
Gips, Vol. 14, pp. 88-95, 1961.
12. Raymond, V. and Nussbaum, R. "A propos des
poussieres de cimenteries et leurs effets sur
1'homme, les plants, et les animaux." Pollut.
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13. Guderian, R. and Pajenkamp, H. "Einwirkung
des Zementofenstaubes auf Pflanzen und Tiere."
Staub, Vol. 21, pp. 518-519, 1961.
14. Wentzel, K. F. and Pajenkamp, H. "Einwirkung
des Zementofenstaubes auf Pflanzen und Tiere."
Zeit. fur Pflanzenkrankh, Vol. 69, p. 478, 1962.
15. Czaja, A. T. "Die Wirkung von verstaubtem Kalk
und Zement auf Pflanzen." Qualitas Plant Mater.
Vegetabiles, Vol. 8, pp. 184-212, 1961.
16. Czaja, A. T. "Zementstaubwirkungen auf Pflan-
zen: Die Entstehung der Zementkrusten." Quali-
tas Plant Mater. Vegetabiles, Vol. 8, pp. 201-238,
1961.
17. Scheffer, F., Przemeck, E., and Wilms, W. "Un-
tersuchungen fiber den Einfluss von Zementofen-
Flugstaub auf Boden and Pflanze." Staub, Vol.
21, pp. 251-254, 1961.
18. Stratmann, H. and van Haut, H. "Vegetations-
versuche mit Zementflugstaub." (Unpublished in-
vestigations of the Kohlen-Stoff-biologischen For-
schungsstation) Essen, Germany, 1956.
19. Pack, M. R., Hull, A. C., Thomas, M. D., and
Transtrum, L. G. "Determination of Gaseous and
Particulate Inorganic Fluorides in the Atmos-
phere." Am. Soc. Testing Mater., Spec. Tech.
Pub. 281, 1959, pp. 27-44.
20. McCune, D. C., Hitchcock, A. E., Jacobson, J. S.,
and Weinstein, L. H. "Fluoride Accumulation and
Growth of Plants Exposed to Particulate Cryo-
lite in the Atmosphere." Contrib. Boyce Thomp-
son Inst., Vol. 23, pp. 1-22, 1965.
21. Jennings, O. E. "Smoke Injury to Shade Trees."
Proc. Nat. Shade Tree Conf., 10th, 1934, pp.
44-48.
22. Berge, H. "Luftverunreinigungen im Raume
Koln." Allgem. Forstz., Vol. 51-52, pp. 834-838,
1965.
23. Miller, P. M. and Rich, S. "Soot Damage to
Greenhouse Plants." Plant Disease Reptr., Vol.
51, p. 712, 1967.
24. Sievers, F. J. "Crop Injury Resulting from Mag-
nesium Oxide Dust." Phytopathology, Vol. 14,
pp. 108-113, 1924.
25. Berge, H. "Emissionsbedingte Eisenstaube und
ihre Auswirkungen auf Wachstum und Ertrag
landwirtschaftlicher Kulturen." Zeit. Luft-
vereinigung (Dusseldorf), Vol. 2, pp. 1-7, 1966.
26. Shupe, J. L., Miner, M. L., Harrison,. L. E., and
Greenwood, D. A. "Relative Effects of Feeding
Hay Atmospherically Contaminated by Fluoride
Residues, Normal Hay Plus Calcium Fluoride,
and Normal Hay Plus Sodium Fluoride to Dairy
Heifers." Am. J. Vet. Res., Vol. 23, pp. 777-787,
1962.
27. Phillips, P. H. "The Effects of Air Pollutants on
Farm Animals." In: Air Pollution Handbook, P.
L. Magill, F. R. Holden, and C. Ackley (eds.),
McGraw-Hill, New York, 1956.
96
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Chapter 7
SOCIAL AWARENESS OF PARTICULATE POLLUTION
-------
Table of Contents
Page
A. INTRODUCTION 99
B. THE STUDIES 99
1. St. Louis, Missouri . . 99
2. Nashville, Tennessee 100
3. Birmingham, Alabama , 101
4. Buffalo, New York 101
C. SUMMARY 102
D. REFERENCES 102
List of Figures
Figure
7-1 Proportion of Population in St. Louis Stating Air Pollution Present
in Their Area of Residence, and Proportion of St. Louis Population
Bothered 100
7-2 The Level of Air Pollution Related to Public Opinion in Three In-
come Groups (Nashville, Tennessee) 101
7-3 Radial Distribution from the Center of Nashville of Air Pollution
Levels, Socioeconomic Status and Public Concern About Air Pollu-
tion . 101
98
-------
Chapter 7
SOCIAL AWARENESS OF PARTICIPATE POLLUTION
A. INTRODUCTION
The nuisance of air pollution is to some
extent a subjective perception, and its signifi-
cance is therefore influenced to some extent
by the way the public feels about pollution.
Nevertheless, it is acceptable practice to con-
clude that nuisance and levels of pollution
are related if it can be demonstrated that a
nuisance response by a sample population is
positively related to average levels of actual
pollution. The development of such evidence
is difficult because public reaction probably
reflects pollution peaks rather than the mean
value for an extended time period. This prob-
lem has been considered by McKee 1 in a re-
cent paper.
Several studies have attempted to assess
the annoyance to a population of community
air pollution, but not all have taken advan-
tage of available aerometric data to establish
the relationships between air pollution levels
and attitudes and opinion among' the affected
population. The chief value of these surveys
lies in demonstrating that a significant pro-
portion of the public is aware of, and con-
cerned about, air pollution, and is willing to
act to abate the nuisance.2-3 One of the most
obvious indications of the nuisance of air pol-
lution is citizen complaints. Generally speak-
ing, the person who is willing to take the
time to telephone or write a complaint about
air pollution is probably seriously irritated by
it. And those who actually complain may rep-
resent only the top of the iceberg. There are
many who may be irritated who will not com-
plain because they do not believe complaining
will do any good. There are others, conspicu-
ous by their absence, who have moved away
because of the effects of air pollution on their
health, or because of the aesthetic degrada-
tions of their neighborhood. Unfortunately,
very little work has been done in this partic-
ular area of measuring the response of the
public to the nuisance of air pollution.
It is important to note that application of
present control technology may result in a
much larger reduction in larger particles
than in smaller particles. The remaining
smaller particles will not be as readily dis-
cernible to the public, and awareness of par-
ticulate pollution may diminish.
The effect of particulates on the total eco-
logical system and man's enjoyment of his
environment cannot as yet be fully evaluated.
B. THE STUDIES
1. St. Louis, Missouri
One major investigation of the relation-
ship between public opinion and particulate
air pollution concentrations is that conducted
in the Greater St. Louis area.3- * This area
comprises portions of St. Louis County, Mis-
souri, and portions of Madison and St. Clair
Counties, Illinois. It includes St. Louis, East
St. Louis, and Granite City, and thus most
of the population residing in the St. Louis
metropolitan area, as denned by the Bureau
of the Census. Persons interviewed were
asked whether they believed that air pollu-
tion was present and whether they regarded
it as a nuisance. The responses were related
to the pollution level measured both as sus-
pended particle concentration and as soiling
index. (See Chapter 1 for a discussion of this
latter measure of pollutant concentration.)
Figure 7-1 shows the results obtained for
both questions in terms of suspended particle
concentrations. It will be seen that the popu-
lation becomes aware of pollution before it
regards it as a nuisance. Where the average
annual geometric mean of particles was 80
3, better than 30 percent of the popula-
99
-------
100
5 80
EC CO
SI1
^40
o
tr
HI
Q_
20
POLLUTION PRESENT
NUISANCE
0 50 100 150 200
SUSPENDED PARTICLES, flg/m3-
(ANNUAL GEOMETRIC MEAN)
FIGURE 7-1. Proportion of Population in St. Louis
Stating Air Pollution Present in Their Area of
Residence, and Proportion of St. Louis Popula-
tion Bothered. (This figure presents the results
obtained from interviews.)
tion indicated awareness of air pollution.
Fifty percent and 75 percent of the survey
population were aware of air pollution in the
area where the average annual levels of par-
ticulate matter were 120 /xg/m3 and 160 jug/m3
respectively. None of the population ap-
peared to be bothered by particle concentra-
tions below 50 /xg/m3, 10 percent of the popu-
lation was bothered at a level of about 80
/xg/m3, 20 percent was bothered about 120
tig/m3, 33 percent at 160 /xg/m3, while 40
percent regarded a concentration of 200
/xg/m3 as constituting a nuisance. The data
on the nuisance response in Figure 7-1 can
be expressed approximately in the form
y~0.3x-14
over the range studied, where y is the per-
centage of the population expressing dissatis-
faction, and x is the annual geometric mean
of suspended particle concentration in /xg/m3.
The equation assumes that the character of
the pollution is the same for areas of both
high and low pollution.
2. Nashville, Tennessee
A study by Smith et al.5 reveals the com-
plexity of public opinion surveys. The method
used was similar to that in other surveys:
public opinion data were compared with aero-
metric data from the nearest air sampling
station. One group of questions in the public
opinion survey dealth specifically with nui-
sance aspects of air pollution, asking re-
spondents to indicate whether the outside of
the house got too dirty, whether automobiles
got dirty too fast, and whether too much dust
collected on porches and window sills. An-
other question, measuring "bother" by air
pollution was embedded in a series of ques-
tions relating to health, and responses to it
should not be compared directly with re-
sponses of general concern and nuisance in
other surveys. The proportion of affirmative
responses to the question concerning too
much dust and dirt on porch and window sills
showed a clear increase with increasing par-
ticle concentrations. The data do not, how-
ever, permit a predictable quantitative state-
ment of this responsibility.
Survey results indicated that up to 3.8
percent of the respondents voluntarily ex-
pressed awareness and concern about air
pollution as a health problem; an extension
of the sample population of about 2,850 to
the total population indicated that this figure
equated to approximately 9,000 residents.
In response to a direct question, 23 percent
of the respondents—or approximately 50,000
residents, if the sample were projected to the
total population—stated they were bothered
in some way by air pollution. In response to
direct questions, several specific non-health
aspects of smog—soiling, decreased visibility,
odors, and property damage—were cited as
affecting from 18 percent to 51 percent of
the respondents, or between 40,000 to 100,000
of all residents, as based on the sample popu-
lation. It was also concluded that the fre-
quency of days of acute pollution had an ad-
ditional influence on the proportion of people
who would express concern and annoyance.
The study indicated some relationships be-
tween level of concern and socioeconomic
status. At high levels of air pollution, con-
cern was greater among women of high socio-
economic status than among women of low
socioeconomic status, although at low levels
of air pollution, those of low socioeconomic
status expressed more concern than those of
high status. There was also a relationship
between socioeconomic status and the dis-
tance of residence from the center of Nash-
ville (the more affluent living farther away
in general). Figures 7-2 and 7-3 together
100
-------
demonstrate the interlocking relationship;
Figure 7-2 uses arbitrary scales for both
variables and should not be taken to indicate
the exact form of the relationships.
3. Birmingham, Alabama
Stalker and Robison 6 compared data from
21 air sampling stations with public re-
sponses from a sample of 7200 households.
Data were gathered only from people living
within one mile of an air sampling station.
The investigators found that 10 percent of
the population believed a nuisance existed at
a seasonal (summer) mean suspended parti-
cle concentration between 60 jug/m3 and 180
ju.g/m3, and more than 30 percent of the popu-
lation believed a nuisance existed at levels
between 100 jug/m3 and 220 /xg/m3. The au-
thors use their dustfall data to demonstrate
that for each increment of 10 tons/mile2-
month another 10 percent of the affected
public would become concerned and consider
that level a general nuisance. Although the
published data indicates that the relation-
I- w
p
< oc
-------
suspended particles. There was also a posi-
tive relationship between the frequency of
days of acute levels of these pollutants and
public opinion.
C. SUMMARY
Public opinion survey data in several cities
indicate a positive relationship between the
concern expressed about air pollution by a
population and the actual levels of particulate
pollution—used as an index of air pollution.
In general, over the ranges studied, an in-
creasing proportion of the population ex-
presses dissatisfaction over air pollution as
concentrations of particulate matter increase.
However, while the several studies agree, for
the most part, in this qualitative relationship,
it is difficult to compare the studies quantita-
tively. Each study used different sampling
schemes, questionnaire schedules, and meth-
ods of interviewing. In addition, the socio-
economic characteristics of the population
sampled varied from city to city. The St.
Louis data has been singled out for quantita-
tive expression because it showed the most
consistent association between air pollution
and public awareness. However, it is in-
tended to serve only as an example.
Over the approximate range 50 /ig/m3 to
200 /ug/m3, the expression
y~0.3x-14
relates roughly the percentage of concerned
St. Louis population, y, and the annual geo-
metric mean suspended particle concentra-
tion x (/tg/m3). Thus, 10 percent of the study
population was bothered by air pollution in
areas where the annual geometric mean value
of suspended particulates was about 80.
/ig/m3. About 20 percent of the study popula-
tion was bothered in areas with an annual
geometric mean value of 120 ^g/m and 33
percent with a mean of 160 ^g/m3. The re-
sponses are probably associated with the
short term fluctuations in particulate levels
which underlie any averaging time period.
Other studies show that when dustfall
levels exceeded an annual mean of 10 tons/
mile2-month, at least 10 percent of the af-
fected population expressed concern about a
nuisance situation.
The available literature also indicates that
the extent to which a population considers air
pollution an annoyance is related to the fre-
quency of days with acute pollution as well
as to the average level that the level of con-
cern is related to socioeconomic status, and
that the population becomes aware of pollu-
tion at particle concentrations lower than
those at which they consider that it consti-
tutes a nuisance.
In the St. Louis study, 30 percent of the
study population were aware of pollution in
areas where the annual geometric rnean value
of suspended particulates was 80 jug/m3, 50
percent in areas with 120 jug/m3 and 75 per-
cent in areas with 160 /jg/m3.
D. REFERENCES
1. McKee, H. C. "Why a General Standard for Par-
ticulates?" (Presented at the Symposium on Air
Quality Standards: The Technical Significance,
156th National Meeting, American Chemical So-
ciety, September 12, 1968.)
2. de Groot, I. and Samuels, S. W. "People and Air
Pollution: A Study of Attitude in Buffalo, New
York. An Interdepartment Report." New York
State Dept. of Health, Air Pollution Control
Board, 1965. (See also de Groot, I., Loring, W.,
Rihm, A., Samuels, S. and Winkelstein, W., same
title, J. Air Pollution Control Assoc., Vol. 16, pp.
245-247, 1966.)
3. "Public Awareness and Concern with Air Pollu-
tion in the St. Louis Metropolitan Area." U.S.
Dept. of Health, Education, and Welfare, Div. of
Air Pollution, Washington, D. C., May 1965. (See
also Schusky, J., same title, J. Air Pollution Con-
trol Assoc., Vol. 16, pp. 72-76, 1966.)
4. Williams, J. D. and Bunyard, F. L. "Interstate
Air Pollution Study, Phase II Project Report,
Vol. VII—Opinion Surveys and Air Quality Sta-
tistical Relationships." U.S. Dept. of Health,
Education, and Welfare, Div. of Air Pollution,
Cincinnati, Ohio, 1966.
5. Smith, W. S., Schueneman, J. J., and Zeidberg,
L. D. "Public Reaction to Air Pollution in Nash-
ville, Tennessee." J. Air Pollution Control Assoc.,
Vol. 14, pp. 418-423, 1964.
6. Stalker, W. W. and Robison, C. B. "A Method
for Using Air Pollution Measurements and
and Public Opinion to Establish Ambient Air
Quality Standards." J. Air Pollution Control
Assoc., Vol. 17, pp. 142-144. 1967.
102
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Chapter 8
ODORS ASSOCIATED WITH
ATMOSPHERIC PARTICULATE MATTER
-------
Table of Contents
Page
A. INTRODUCTION 105
B. EVIDENCE FOR THE ASSOCIATION OF ODOR WITH
PARTICLES . 105
C. HYPOTHETICAL MECHANISM FOR THE ASSOCIATION OF
ODOR WITH PARTICLES 106
1. Volatile Particles 106
2. Desorption of Odorous Matter by Particles 106
3. Odorous Particles 107
D. COMMON ODOR PROBLEMS 107
E. SUMMARY . 107
F. REFERENCES 108
List of Tables
Table
8-1 Most Frequently Reported Odors . . 107
104
-------
Chapter 8
ODORS ASSOCIATED WITH ATMOSPHERIC PARTICULATE MATTER
A. INTRODUCTION
The human olfactory sense has the ability
to detect and respond to thousands of differ-
ent materials or chemical compounds. Some
odorants can be detected in concentrations as
low as one part per billion. Modern instru-
mentation lacks both the selectivity and the
sensitivity possessed by the olfactory sense
for the detection of many odorants.
Odorants in themselves may not cause or-
ganic disease; however, the discomfort and
disagreeableness that may be brought about
by obnoxious odors can cause some tempo-
rary ill effects. The effects that border upon
ill health include lowered appetite, lowered
water consumption, impaired respiration,
nausea, vomiting, and insomnia.
Particulate matter in itself is not consid-
ered to be capable of directly stimulating the
olfactory sense. However, this should not be
interpreted to mean that all airborne particu-
late matter, as a pollutant category, is in-
capable of stimulating the odor sense nor
that particles cannot be involved in the de-
livery of the odorant to the receptor cells.
There is evidence that some particles can
stimulate the sense of smell because the parti-
cle itself is volatile or because this particle is
desorbing a volatile odorant.1 There is also
speculation 2 that some particulate matter is
capable of stimulating the sense of smell. Re-
gardless of the mechanism of how particles
are involved in the stimulation of the olfac-
tory sense, the important fact is that they
definitely appear to be involved.
B. EVIDENCE FOR THE ASSOCIATION
OF ODOR WITH PARTICLES
The idea that odors are associated with
particles is supported by observations that
nitration of particles from an odorous air
stream can reduce the odor level. Rossano and
Ott2 showed that the removal of particulate
matter from diesel exhaust by thermal pre-
cipitation effected a marked reduction in
odor intensity. The precipitation method was
selected because it provides minimal con-
tact between the collected particles and
the gaseous components of the diesel ex-
haust stream. Thus, effects that could be
produced by a filter bed, such as removal
of odorous gases by absorption in the fil-
ter cake, are eliminated. The observed odor
reduction must, therefore- have resulted di-
rectly from the removal of particulate mat-
ter. The particles collected by Rossano and
Ott were aggregates of spherical balls about
0.04ft. to 0.05ft. in diameter. Particulate matter
from diesel exhaust collected on glass fiber
filters by Linnell and Scott3 yielded a heavy
"diesel" odor. Analysis of the particulate
matter showed that it contained no acrolein
or formaldehyde, although it did release N02
on being heated to 100°C. The authors con-
clude that "no appreciable gas phase con-
centration changes for acrolein or formalde-
hyde will result from particulate removal."
Other more or less casual observations on the
role of particulate matter in community odor
nuisance problems appear occasionally in the
literature.4
A second piece of evidence that implicates
the association of particles with odors is the
production of a mild odor, sometimes de-
scribed as "yeasty," in air that is passed
through a bed of activated carbon. Turk and
Bownes •• have shown that this odor is not
produced by any detectable desorption of
gaseous matter from the carbon, and that
the same odor can be produced by passing
air through silica gel.6 It is possible that
subfilterable particles are associated with
this phenomenon.
Evidence for the association of particulate
105
-------
matter with outdoor odors has sometimes
been sought in the gross errors in odor in-
tensities preducted on the basis of gas-phase
dispersion of an odor source. However, the
interpretation of these experiments is open
to doubt, and it is probable that the effects
are a result of fortuitous fluctuations in emis-
sion. For example, Walter and Amberg 7 have
found that concentrations of hydrogen sulfide
in a kraft paper pulp mill recovery furnace
can vary from 100 ppm to as much as 1,000
ppm. Such wide variations in emission may
help to explain the discrepancy, reported by
Wohlers 8 for a kraft mill, between the odor
intensities observed and those predicted from
odor threshold concentrations and dilutions
calculated by Button's formula.9 The likeli-
hood that errors in calculations of the atmos-
pheric dispersal of true gases are compara-
tively small is supported by experiments with
gas tracers like sulfur hexafluoride (SF6).
Collins et al.w and Turk et al.11 have shown
agreement between calculated and observed
concentrations of a tracer gas at distances up
to about three miles from the emission point
to be within about 25 percent. It is true that
olfactory sensation is responsive to concen-
trations that may be present for only brief
intervals, whereas dispersion calculations
refer to time averages for intervals of about
one-half hour, and the tracer gas studies cited
used 20-minute integrated samples. Some of
the discrepancy between results of odor meas-
urements on the one hand, and results from
calculations or tracer gas tests on the other,
may therefore be accounted for by the peak-
to-mean ratios that result from the effects of
turbulence and eddies in the air stream.
There are no published data on the minimum
time duration required for odor detection or
odor nuisance responses. Efforts by Turk and
coworkers to determine the ratio of "instan-
taneous" (one second) to average (20 min-
ute) concentrations of tracer gas failed to
show significantly high values, possibly be-
cause such occurrences are rare and escaped
the sampling grid. In any event, the peak-to-
mean ratios would have to be in the 1,000 to
10,000-fold range to explain observed discrep-
ancies, and we have no data that are based on
meteorological factors alone to support such
extreme values.
C. HYPOTHETICAL MECHANISMS FOR
THE ASSOCIATION OF ODOR WITH
PARTICLES
1. Volatile Particles
Liquid or even solid aerosols may be suffi-
ciently volatile that their vaporization on en-
tering the nasal cavity produces enough gas-
eous material to be detected by smell. Such
aerosols may be relatively pure substances,
such as particles of camphor, or they may be
mixtures which release volatile components.
The retention of the odorous properties of
volatile aerosols will, of course, depend on the
prevailing temperature and on the length
of time they are dispersed in air. In a cold
atmosphere, the relatively greater tempera-
ture rise accompanying inhalation will accel-
erate the production of gaseous odorant.
2. Desorption of Odorous Matter by
Particles
Goetz 12 has treated the kinetics of the in-
teraction between gas molecules and the sur-
face of airborne particles. His theoretical
considerations were directed to the question
of transfer of toxicants by particles, but are
also applicable to odors. Even if a given aero-
sol is intrinsically odorless, it could act as an
odor intensifier if: 1. the sorptive capacity of
the aerosol particles for the odorant were
smaller than the affinity of the odorant for
the nasal receptor and at the same time, 2.
the sorptive capacity of the aerosol particles
were large enough to produce an accumula-
tion of odorant on the particle surface. Such
aerosol particles would concentrate odorous
molecules on their surfaces, but the odorous
matter would be transferred to olfactory
receptors when the aerosol entered the nasal
cavity. The odorous matter would then be
present at the receptor sites in concentrations
higher than in the absence of the aerosol. The
resulting effect would be synergistic. See
Chapter 10-C-3 for a discussion of syner-
gistic effects of particles and irritants. These
synergistic effects may be analogous to par-
ticle-odorant synergism. If an odorant is
more strongly adsorbed by the aerosol parti-
cles than by the olfactory receptors, transfer
of the odorant to the receptors would be im-
peded and the particles would actually at-
tenuate the odor.
106
-------
3. Odorous Particles
No study has ever rigorously defined the
upper limit of particle size for airborne odor-
ous matter. Particles up to about 8 or 10 x
10 4 ju. in diameter are considered to be mole-
cules that can exist in equilibrium with a
solid or liquid phase from which they escape
by vaporization. The vapor pressure de-
creases as the molecular weight increases,
and particles above about 10~3 ^ do not gener-
ally exist in any significant concentration in
equilibrium with a bulk phase; hence we do
not consider them to be "vapors." Nonethe-
less, it is possible that odorant properties do
not disappear when particle sizes exceed
those of vapor molecules. Our knowledge
about particles in the size range of 1 to 5 X
10~3 n (up to about the size of small viruses)
is relatively meager, and we do not know
whether or not they can be odorous, nor what
the effect of an electrical charge on their
odorous properties might be. Larger parti-
cles may also be intrinsically odorous, al-
though their more significant role may be to
contribute to odor by absorbing and desorb-
ing odorous gases and vapors.
D. COMMON ODOR PROBLEMS
Kerka and Kaiser13 surveyed State and
local air pollution control personnel and com-
piled the list of most frequently reported
odors shown in Table 8-1.
Of the 35 listings in Table 8-1, nine are
either known to be or suspected to be particu-
late-borne. These nine include gasoline- and
diesel-engine exhaust, coffee roasting, restau-
rant odors, paint spraying, roofing and street
paving, asphalt manufacturing, home incin-
erators and backyard trash fires, city inciner-
ator burning garbage, and open-dump fires.
E. SUMMARY
Airborne particulate matter, as an air pol-
lutant category, is normally not considered
as a source of odor stimulation. However,
there is evidence that some particulates hav-
ing volatile components can produce an odor
response in human receptors.
Further, by a suggested mechanism of ad-
sorption and subsequent desorption, an odor-
ant may be transferred by a particulate sub-
Table 8-1.—MOST FREQUENTLY REPORTED
ODORS
Number
Source of odor reported
Animal odors:
Meat packing and rendering plants 12
Fish oil odors from manufacturing
plants 5
Poultry ranches and processing 4
Odors from combustion processes:
Gasoline and diesel engine exhaust 10
Coke-oven and coal-gas odors (steel
mills) 8
Maladjusted heating systems 3
Odors from food processes:
Coffee roasting .. 8
Restaurant odors . 4
Bakeries . . 3
Paint and related industries:
Manufacturing of paint, lacquer, and
varnish . 8
Paint spraying 4
Commercial solvents . 3
General chemical odors
Hydrogen Sulflde 7
Sulfur Dioxide 4
Ammonia 3
General industrial odors
Burning rubber from smelting and
debonding . . 5
Odors from dry-cleaning shops 5
Fertilizer plants 4
Asphalt odors—roofing and street
paving 4
Asphalt odors—manufacturing 3
Plastic manufacturing 3
Foundry odors
Core-oven odors 4
Heat treating, oil quenching, and
pickling 3
Smelting 2
Odors from combustible waste:
Home incinerators and backyard
trash fires 4
City incinerators burning garbage 3
Open-dump fires 2
Refinery odors:
Mercaptans 3
Crude oil and gasoline odors 3
Sulfur . 1
Odors from decomposition of waste:
Putrefaction and oxidation—organic
acidsa 3
Organic nitrogen compounds—decom-
position of protein a 2
Decomposition of lignite (plant cells) 1
Sewage odors:
City sewers carrying industrial waste 3
Sewage treatment plants 2
a Probably related to meat processing plants.
107
-------
strate. When one examines the various types
of odor sources which result in public aware-
ness of an undesirable situation, a significant
number of these listings are either known to
be or suspected to be particulate-borne. A
survey of State and local air pollution control
officials revealed that approximately one-
fourth of the most frequently reported odors
are those which are known to be, or are sus-
pected to be, associated with particulate air
pollution. The sources of these odorous parti-
cles are diverse, including diesel- and gaso-
line-engine exhaust, coffee-roasting opera-
tions, paint spraying, street paving, and the
burning of trash. Despite the absence of an
exact mechanism to explain the association
of odor with particulates, their intimate in-
volvement in multiple categories of citizen
nuisance complaints cannot be ignored.
F. REFERENCES
1. Roderick, W. R. "Current Ideas on the Chemical
Basis of Olfaction." J. Chem. Educ., Vol. 43, pp.
510-520, 1966.
2. Rossano, A. T. and Ott, R. R. "The Relationship
Between Odor and Particulate Matter in Diesel
Exhaust." Preprint. (Presented at the Annual
Meeting of the Pacific Northwest International
Section, Air Pollution Control Association, Port-
land, Oregon, November 5-6, 1964.)
3. Linnel, R. H. and Scott, W. E. "Diesel Exhaust
Composition and Odor Studies." J. Air Pollution
Control Assoc., Vol. 12, pp. 510-515, 1962.
4. Quebedeaux, W. A. "New Applications for Indus-
trial Odor Control." Air Repair, Vol. 4, pp. 141-
142, 170-171, 1954.
5. Turk, A. and Bownes, K. "Inadequate Stimula-
tion of Olfaction." Science, Vol. 114, pp. 234-236,
1951.
6. Turk, A., Kakis, F., and Morrow, J. "The Ad-
sorbent Odor." Preprint. (Presented at the Amer-
ican Chemical Society meeting, New York, Sept.
1960.)
7. Walther, J. E. and Amberg, H. R. "Continuous
Monitoring of Kraft Mill Stack Gases with a
Process Gas Chromatograph." Tappi, Vol. 50,
pp. 19-23, 1967.
8. Wohlers, H. C. "Odor Intensity and Odor Travel
from Industrial Sources." Intern. J. Air Water
Pollution, Vol. 7, pp. 71-78, 1963.
9. Sutton, O. G. "The Theoretical Distribution of
Airborne Pollution from Factory Chimneys."
Quart. J. Roy. Meteorol. Soc., Vol. 73, pp. 426-
436, 1947.
10. Collins, G. F., Barlett, F. E., Turk, A., Edmonds,
S. M. and Mark, H. "A Preliminary Evaluation
of Gas Air Tracers." J. Air Pollution Control
Assoc., Vol. 15, pp. 109-112, 1965.
11. Turk, A., Edmonds, S. M., Mark H. L., and Col-
lins, G. F. "Sulfur Hexafluoride as a Gas-Air
Tracer." Environ. Sci. Technol., Vol. 2, pp. 44-
48, 1968.
12. Goetz, A. "On the Nature of the Synergistic
Action of Aerosols." Intern. J. Air Water Pollu-
tion, Vol. 4, pp. 168-184, 1961.
13. Kerka, W. F. and Kaiser, E. R. "An Evaluation
of Environmental Odors." J. Air Pollution Con-
trol Assoc., Vol. 7, pp. 297-301, 1958.
108
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Chapter 9
THE RESPIRATORY SYSTEM: DEPOSITION, RETENTION,
AND CLEARANCE OF PARTICULATE MATTER
-------
Table of Contents
Page
A. INTRODUCTION Ill
B. ANATOMY OF THE HUMAN RESPIRATORY TRACT 111
C. FACTORS AFFECTING THE DEPOSITION AND RETENTION OF
PARTICULATE MATTER IN THE RESPIRATORY SYSTEM 112
1. Physical-Mathematical Treatments . 112
a. Deposition Mechanisms . 112
b. Aerodynamic Factors 113
c. The Models . .. .114
2. Experimental Studies of Factors Affecting Deposition and
Retention . 116
a. Total Deposition in the Respiratory Tract . . ..117
(1) Effect of Particle Size 117
(2) Physiological Parameters . ... 117
b. Regional Deposition . 118
(1) Nasal Fractionation 118
(2) Lung Deposition . 118
(3) Comparative Human and Animal Retention . . 119
3. Conclusions Reached about Alveolar Deposition . . . 119
D. FACTORS AFFECTING THE CLEARANCE OF PARTICULATE
MATTER FROM THE RESPIRATORY SYSTEM . . 119
1. Clearance Model . 120
2. Clearance from the Tracheobronchial System . .. 121
3. Clearance from the Alveolar Surface 122
E. SUMMARY 123
F. REFERENCES 123
List of Figures
Figure
9-1 The Major Anatomical Features of the Human Respiratory System 112
9-2 The Terminal Bronchial and Alveolar Structure of the Human Lung 112
9-3 Calculated Fraction of Particles Deposited in the Respiratory Tract
as a Function of Particle Radius . . 114
9-4 Fraction of Particles Deposited in the Three Respiratory Tract Com-
partments as a Function of Particle Diameter . .115
9-5 Data from Figure 9-4 for the Nasopharyngeal Compartment Plotted
as a Log-probability Function (Minute Volume: 20 1/min) . 116
9-6 Data from Figure 9-4 for the Pulmonary Compartment Plotted as a
Log-probability Function (Minute Volume: 20 1/min) . . . 116
9-7 Schematic Portrayal of Dust Deposition Sites and Clearance Proc-
esses . . . .... 120
List of Tables
Table
9-1 Respiratory Airflow Patterns for a Group of Healthy Young Men . 113
110
-------
Chapter 9
THE RESPIRATORY SYSTEM: DEPOSITION, RETENTION, AND
CLEARANCE OF PARTICULATE MATTER
A. INTRODUCTION
In urban communities, exposure to atmos-
pheric pollutants may constitute a health
hazard that is the most serious single conse-
quence of air pollution. Chapters 10 and 11
discuss the effects of particulate pollutants
on health in terms of toxicological and epide-
miological studies. Pollutants are likely to
enter the human body mainly via the respira-
tory system; other routes of entry are of
minor importance. Damage to the respiratory
organs may follow directly, or the pollutant
may be transported by some mechanism to a
remote susceptible organ. It is apparent that
a study of the effect on health of particulate
atmospheric pollutants requires an under-
standing of the mechanisms and efficiencies
of deposition of particles in the respiratory
system, and of the subsequent retention with-
in, and clearance from- the system, as well
as its secondary relocation to other sites in
the body. This chapter provides a brief intro-
duction to the physics and physiology of de-
position, retention, and clearance in the res-
piratory system. More complete descriptions
may be found in several reviews.1-3
Experimental studies of the several fac-
tors involved in deposition, retention, and
clearance processes have been backed up by
theoretical treatments and, in the discussion
which follows, descriptions of these theoreti-
cal models precede those of experimental
work. One of the latest theoretical models is
that developed by the Task Group on Lung
Dynamics for Committee II of the Interna-
tional Radiological Protection Commission.4
The Task Group's report establishes the use-
fulness of the Stokes (mass median) diam-
eter (cf. Chapter 1-A) of a particle as a
measure of deposition probability. This is of
practical importance, since the Stokes diam-
eter may readily be determined under field
conditions.
The anatomy of the respiratory system
plays an important part in determining the
effects of inhaled particles, and a very short
description of this anatomy is provided. Sev-
eral extensive presentations of morphological
studies are available,5-6 and Davies 7 gives a
formalized concept of the anatomy of the
human respiratory tract.
B. ANATOMY OF THE HUMAN
RESPIRATORY TRACT
The respiratory system is usefully broken
down into three main sections:
1. the nasopharyngeal structure;
2. the tracheobronchial system; and
3. the pulmonary structure, within
which oxygen and carbon dioxide are
exchanged between respired air and
blood.
Figure 9-1 shows the location of these fea-
tures. The nasal passages lead, via the naso-
pharyngeal structure and the larnyx, to the
trachea and the bronchi, which are made up
of 23 generations of dichotomous branching
tubes terminating in the alveolar (air) sacs.
Figure 9-2 is a schematic representation in
greater detail of the terminal bronchiole and
pulmonary structure.
Estimates of numbers of alveoli differ
somewhat from one experimenter to another:
a recent suggestion 8 is that there are 300 mil-
lion, together with 14 million alveolar ducts.
The alveoli are probably between 150/t and
400/i in diameter, so that the total alveolar
surface varies between about 30 m2 and 80
m2. The increasing total cross-sectional area
with progression down the respiratory tract
111
-------
NASAL
CAVITY
ORAL
CAVITY
TERMINAL
BRONCHIOLES
LEFT
BRONCHUS
RIGHT LUNG
LEFT LUNG
FIGURE 9-1. The Major Anatomical Features of the
Human Respiratory System. (The diagram shows
the major divisions of the human respiratory tract
into nasopharyngeal, tracheobronchial, and pul-
monary compartments.)
leads to a marked decrease in the velocity of
air movement with depth.
The nasopharyngeal and tracheobronchial
structures possess ciliated epithelium covered
with mucus arising from goblet cells and
secretory glands. These structures also make
up the anatomical "dead space," since oxygen
exchange between the blood and air does not
occur here. If the volume of this dead space
is Vd, the lungs must draw in a volume V in
order to obtain a volume V-Vd of fresh air,
which is called the tidal volume. The surface
of the pulmonary structure consists of non-
ciliated moist epithelium that, although de-
void of the secretory element found in the
tracheobronchial tree, is covered by a sur-
face-active material, without which alveoli
would totally collapse (atelectasis) at the end
of respiration.
C. FACTORS AFFECTING THE
DEPOSITION AND RETENTION OF
PARTICULATE MATTER IN THE
RESPIRATORY SYSTEM
1. Physical-Mathematical Treatments
The theoretical physical-mathematical
TERMINAL
BRONCHIOLE
RESPIRATORY
BRONCHIOLE
ALVEOLI
FIGURE 9-2. The Terminal Bronchial and Alveolar
Structure of the Human Lung. (The diagram
shows the pulmonary structure of the respiratory
tract.)
treatments use information on the anatomical
structure and airflow rates in the respiratory
tract, together with knowledge of the physi-
cal factors influencing the deposition of par-
ticles. The deposition mechanisms will be
considered first; aerodynamic factors con-
nected with airflow and gas mixing in the
respiratory system will then be mentioned
before proceeding to a discussion of the three
main models which have been developed.
a. Deposition Mechanisms
Three mechanism are of importance in the
deposition of particulate matter in the respi-
ratory tract—inertial impaction, gravitation-
al settling (sedimentation), and diffusion
(Brownian motion). The relative significance
of these deposition mechanisms varies with
anatomical and physiological factors, with
the nature of the airflow, and with the char-
acteristics of the aerosol such as particle
shape and density.
Particles in an ni"«t~eam impinge onto a
112
-------
surface when the inertia of the particle is
great enough to overcome the resistive forces
of the medium and intercept the surface of
the obstacle. If gravity is neglected, the path
of the particle is determined by the air veloci-
ty, the mass and air resistance of the par-
ticle, and size and shape of the obstacle. In-
ertial impaction is therefore of greatest im-
portance in the deposition of large particles
of high density, and at points in the respira-
tory system where the direction of flow
changes at branching points in the airways.
The size of the particle as well as its densi-
ty are singificant factors in determining the
importance of deposition by gravitational set-
tling. The terminal velocities (settling veloci-
ties) of spheres of unit density in air for
10-ju,, l-/x, and 0.1-,u particles are 2.9 xlQ-1
cm/sec, 3.5 XlO-3 cm/sec, and 8.6X10-5 cm/
sec respectively. Density also plays a part
since the sedmimentation behavior of a 0.5-
n particle of density 10 g/cm3 would be
equivalent to that of a unit density particle of
1.5-fi diameter. Hence, gravitational settling
is most important in the depositon of large
particles or of high-density particles such as
dusts of heavy metals. Irregularly shaped
particles will have an aerodynamic size less
than the size predicted on the basis of the
measured geometric diameter.
The third main mechanism active in bring-
ing about deposition of particles in the res-
piratory tract is Brownian movement or dif-
fusion; it is the result of bombardment of the,
particles by air molecules which are in rapid,
random, thermal motion. Diffusion is negli-
gible for large particles (say above 0.5-^,
diameter), while it may be the major mecha-
nism for the deposition of small particles
(below Q.lp.) in the lower pulmonary tract,
where airflow rates are lower and the dis-
tances to the walls are less.
b. Aerodynamic Factors
Two aerodynamic factors, namely, flow
rates and gas mixing, are incorporated in
the models of the respiratory system.
During the respiratory cycle, the actual
airflow rate varies from zero up to a maxi-
mum value and then back down to zero. Usu-
ally the expiratory phase is longer than the
inspiratory phase and there may be pauses
between the two phases. A study of the res-
piratory airflow patterns of healthy young
men at rest and under a wide range of work
loads was made by Silverman et al.9 The max-
imum inspiratory flow rate increased from a
mean value of 40 1/min in sedentary subjects
to 100 1/min at an exercise level of 622 kg-
m/min and to 286 1/min at an exercise level
of 1660 kg-m/min. The corresponding values
for maximum expiratory flow rates were 32,
107, and 322 1/min. The collected results are
shown in Table 9-1.
Changes in flow rate resulting from physi-
cal activity have a profound effect on particle
deposition in the respiratory system; this ef-
fect in turn depends upon the aerodynamic
size of the particulate material inhaled. It has
been demonstrated by Amdur, Silverman,
and Drinker 10 that the inhalation of irritant
particulate material, such as sulfuric acid
mist, can decrease the maximum inspiratory
and expiratory flow rate in human subjects.
Such alterations produced by irritant par-
Table 9-1.—RESPIRATORY AIRFLOW PATTERNS
FOR A GROUP OF HEALTHY YOUNG MEN.8
Exercise Inspiratory flow Expiratory flow
level rate 1/min (max) rate 1/min (max)
Sedentary
622 kg-m/min
1660 kg-m/min
40
100
286
32
107
322
tides could also affect deposition patterns of
particulate matter in general, and may re-
present the physiological defense response of
the body.
Another factor to be considered in the dep-
osition of particulate matter in the lung is
the role of mixing of intrapulmonary gas
flow. A study of this factor has been made
by Altshuler and co-workers " using 0.4-/*
particles suspended in air. From the meas-
ured wash-in and wash-out rates (after re-
turn to particle-free air), the authors were
able to calculate the volume of new air which
mixed with the residual air. Their data
showed that at a tidal volume of 500 ml, not
more than 11 percent to 27 percent of new air
in each successive breath actually mixed with
the residual air. It follows that nondiffusible
113
-------
particles (above 0.5 //.) will tend to penetrate
only to the depth of the new air, while smaller
particles will have great enough diffusion
velocities to move independently into the
static air in the lung, in the same way that
gas molecules do.
c. The Models
For the present purposes, the most impor-
tant model is that of the Task Group on Lung*
Dynamics.4 However, two earlier studies,
those of Findeisen 12 and Landahl,13 are of
significance, since they were both considered
as a basis for the Task Group model. The
Task Group finally selected Findeisen's ana-
tomical model, since it appeared that the
rather more sophisticated treatment of
Landahl gave no better estimates of deposi-
tion values. Further, the cumulative volume
down to the end of the terminal bronchioles
in the Findeisen model is more in keeping
with the anatomical dead space as determined
by physiological measurements.
Findeisen12 predicted the percentage of
deposition and the site of deposition of par-
ticles of various sizes in the respiratory tract.
He estimated there would be a critical parti-
cle size of about 0.3-/x to 0.4-/i radius for
which a minimal amount of 34 percent would
be deposited. This deposition would occur
predominantly in the terminal airways and
alveoli, thus suggesting that particles of this
size should not be dismissed as toxicologically
unimportant. Findeisen also estimated that
the percentage deposition of O.S-/i radius par-
ticles would be 68 percent as much as that of
l-fi radius particles. His calculated deposi-
tions are shown in Figure 9-3. Experimental
work on deposition of particles smaller than
l-/x diameter have borne out Findeisen's pre-
dictions.
Findeisen's concepts of the anatomy of the
pulmonary tract have been criticized by
Weibel.14 Findeisen assumed equal and con-
stant flow rates for inspiration and expira-
tion, a situation which does not prevail dur-
ing the respiratory cycle. Furthermore, this
simple respiratory pattern does not take into
account the unique distribution of air in the
lungs, or the factors of intrapulmonary mix-
ing of tidal and residual air in the lungs.
Landahl13 made a similar theoretical study
i.o-
0.9-
Q0.8
LU
bo.7
en
0.2
0.1
(X,
DEPOSITIOIM IN RESPIRATORY/
SYSTEM
DEPOSITION IN ALVEOLAR
REGION ONLY
10-
,-2
10-
10°
10'
RADIUS, JU
FIGURE 9-3. Calculated Fraction of Particles De-
posited in the Respiratory Tract as a Function
of Particle Radius.12 (The figure represents the
calculated efficiencies of deposition of particles of
various sizes, in the tracheobronchial and alveolar
regions of the respiratory system, and shows the
size for minimum efficiency.)
of the problem of particle deposition in the
respiratory tract, but included the mouth and
pharynx in his anatomical model. He em-
ployed several tidal volumes and breathing
frequencies in his calculations, but in all cases
assumed a constant flow for both the inspira-
tory and expiratory phases. The calculations
yielded deposition values for both phases' and
took into account the progressively smaller
fraction of each tidal volume which pene-
trated to the various depths. Deposition in
various regions for spheres of unit density in
the size range 20 ^ to 0.2 ^ was predicted to
fall to a minimum at the size where the pre-
dominant force bringing about deposition is
shifting from gravitational settling to dif-
fusion. An increase was found in retention
with larger tidal volumes.
Landahl15 also made a separate considera-
tion of deposition in the nasal passages. Ear-
lier studies did not take into account impac-
tion of particles on nasal hairs, or deposition
by inertial forces as the airflow changes di-
rection, or sedimentation within the nasal
chamber. Assuming a flow rate of 18 1/min,
about 75 percent of W-/JL particles would be
retained in the nose. Corresponding values
would be about 50 percent for 5-/* particles
114
-------
and 10 percent for l-/i particles. Landahl
calculated that at flow rates greater than 18
1/min, essentially 100 percent of the particles
above 10 /*. would be retained in the nose and
that there also would be substantial retention
of 2-/x to 5-/i particles. Nasal deposition is
negligible for particles below 1 ^ in diameter.
It follows that the estimated pulmonary dep-
osition values of Findeisen would have to be
revised downward for the large particles.
The Task Group on Lung Dynamics used
the conventional division of the respiratory
tract into three compartments, and made
three fundamental assumptions in the de-
velopment of their model. These were:
1. The log-normal (Chapter 1-B) fre-
quency distribution is generally ap-
plicable to particle sizes in the atmos-
phere. It should be noted that this as-
sumption is by no means universally
accepted.
2. The physical activity of the individual
affects deposition primarily by its ac-
tion on ventilation, since physiological
adjustment to the demands of in-
creased minute ventilation is to in-
crease tidal volume more than respi-
ratory frequency. In terms of produc-
ing the greatest change in deposition
throughout the respiratory tract, the
effect of an increase in volume at a
constant respiratory frequency was
considered. (A frequency of 15
breaths per minute was used together
with tidal volumes of 750, 1450, and
2150 cm3 (BTPS); the lowest tidal
volume is considered representative
of a mild-to-moderate activity state.)
3. The aerodynamic properties of the
particle, the physiology of respira-
tion, and the anatomy of the respira-
tory tract provide a basis for a mean-
ingful and reliable deposition model.
The Task Group's aim was to amalgamate
size-deposition relationships into a general-
ized form which would directly permit the
prophetic use of dust-sampling information.
By conventional sampling methods, the count
median diameter or the mass median diam-
eter is obtainable along with the geometric
standard deviation,
-------
to characterize the deposition probabilities of
the entire particle size distribution from
which it emerged. Other parametric func-
tions of the particle distribution failed to
produce such simple cohesive relationships.
The effect of the varying tidal volumes is
shown in the original report (Figure 12, Ref-
erence 4), but it is possible, for practical pur-
poses, to use a mean curve for 1450 ml to
represent all three respiration states. This
implies that the minute volume will control
the total amount of particulate material de-
posited but will not ordinarily have much
effect on the percentage deposition.
The final step was to plot the combination
of mean distribution versus mean respira-
tory performance curves on log-probability
paper, a manipulation suggested by the sig-
moid shape of the nasopharyngeal and pul-
monary deposition curves. The results are
shown in Figure 9-5 and Figure 9-6. The
deposition in the tracheobronchial compart-
ment is considered, for practical purposes,
as constant at approximately 8 percent of
the inspired particulate matter.
The results of the Task Force's calcula-
tions suggest the type of atmospheric sam-
pling data that will be most meaningful in
the correlation of atmospheric particle con-
centrations and human health. In particular,
the insensitivity of the model to aerodynamic
size distribution leads the Task Force to pro-
pose the concept of "respirable" dust sam-
ples, in which the samplers are designed and
calibrated to provide data from which one
can determine the mass median diameter in
aerodynamic terms. Such considerations
have a special significance in connection with
particles, such as asbestos, which possess an
abnormal deposition behavior.
2. Experimental Studies of Factors
Affecting Deposition and Retention
Experimental studies of the deposition of
inhaled particulate material may be divided
into two broad categories. The first group
101
<£
til
UI
5
10°
ui
10"
1 fl-
I
102
10 30 50 70
DEPOSITION, %
90
99 99.9
FIGURE 9-5. Data from Figure 9-4 for the Naso-
pharyngeal Compartment Plotted as a Log-proba-
bility Function. (Minute volume: 20 1/min).
(The figure shows that there is a roughly linear
relationship between deposition efficiency and the
logarithm of the particle size.)
IT
111
UJ
ea
z
5
111
5
101
10°
10-
I I
10 30 50 70 90
DEPOSITION^
99 99.9
FIGURE 9-6. Data from Figure 9-4 for the Pulmo-
nary Compartment Plotted as a Log-probability
Function (Minute Volume: 20 1/min). (This fig-
ure shows that there is a roughly inverse linear
relationship between deposition efficiency and the
logarithm of particle size.)
116
-------
deals with the measurement of total deposi-
tion in the respiratory tract, and the second
group is concerned with regional deposition
within the various areas of the respiratory
tract.
a. Total Deposition in the Respiratory Tract
Experimental studies of deposition were
first made by Lehmann et al.,16 Saito,17
Owens,18 Baumberger,19 and Sayers et al.w
Drinker et al.,21 measured respiratory deposi-
tion in man with simultaneous recording of
respiratory frequency and minute volume.
The concentration of particulate matter was
measured in the chamber, from which air
was inhaled, and in the exhaled air. An aver-
age retention value of 55 percent at a fre-
quency of six to 18 respirations per minute
was found.
(1) Effect of Particle Size.—The first sys-
tematic study of the influence of particle size
on the percentage deposition of inhaled dust
was made in 1940 by Van Wijk and Patter-
son.22 The subjects- at rest, inspired min-
eral dust particles from the air of South Af-
rican gold mines. Percentage deposition ap-
proached 100 percent above 5 //, and had de-
creased to about 25 percent at 0.25 /i, to the
limit of the measuring technique.
Brown 23> 24 made a series of tests on hu-
man subjects in which he found that the per-
centage deposition is directly proportional
to the particle size and to the density of the
suspended material. (Size refers here to the
physical dimensions of aggregates of par-
ticles rather than to unitary particles.)
More sophisticated experiments by Alt-
shuler et al.23 have used a homogeneous aero-
sol of triphenyl phosphate, with particle
sizes in the range 0.14 i*. to 3.2 /x to study
deposition in human subjects. It was found
that deposition was dependent on particle
size and that the minimum deposition diam-
eter was 0.4 yu., which is in reasonable accord
with the prediction made by Findeisen (0.6
/x to 0.8 ju) 20 years earlier.
The deposition of coal dust in human sub-
jects has been shown 26 to rise from a mini-
mum efficiency of about 30 percent at 0.5 p
to almost 60 percent at 0.1 /* (mass median
diameter). Such an overall efficiency sug-
gests that the absolute efficiency of deposi-
tion of the particles smaller than 0.1 /i in
the pulmonary air spaces is close to 100 per-
cent. Direct measurement of the particulate
matter concentration in samples of alveolar
air showed an efficiency of removal of essen-
tially 100 percent down to about 0.5 /x and
better than 80 percent for particles well be-
low 0.1 ^.2T
A hygroscopic particle may collect suffi-
cient water to increase its size significantly
over that in the dry state. Dautrebande and
Walkenhorst26 have therefore compared the
deposition of sodium chloride with that of
coal dust. Using the dry size of the salt par-
ticles, deposition curves different from those
for coal dust were obtained, but on correcting
(by a factor of seven) to account for the
growth of salt to liquid droplets in the res-
piratory tract, the curves were quite similar
for the two particles. This result is of con-
siderable practical significance, as it means
that hygroscopic particulate air pollutants
will be deposited to a higher degree than
mineral particles of an equal size. The Task
Force Report4 gives equations which may
be applied to correct for the effect of hygro-
scopicity on deposition.
(2) Physiological parameters.—In Brown's
experiments,23'24 the effect of varying res-
piratory frequency, tidal volume, and minute
volume was determined by making measure-
ments on subjects breathing at rest, under
various work loads on a bicycle ergometer,
and breathing air containing added C02. The
conclusions of this work were:
1. Percentage deposition is inversely
proportional to respiratory rate for
rates below 20 per minute and an
increase in frequency above 30 per
minute causes no further change in
percentage deposition;
2. Percentage deposition is inversely
proportional to the minute volume;
and
3. Percentage deposition is unaffected
by tidal volume, vital capacity, or
relative humidity of the inspired air.
The results are essentially in agreement
with the predictions of Findeisen and Lan-
dahl (although no effect of tidal volume on
deposition was observed).
In general agreement with Brown's result
117
-------
for respiratory rate, Altshuler et al.25 found
in their experiments that slower, deeper
breathing gave greater deposition than
faster, shallow breathing. It is also shown
that, in agreement with prediction, the dif-
ferences due to respiratory frequency are
greater for 1.6-/* particles than for 0.14-/*
particles. For the 1.6-/* particles, impaction
and settling are the dominant mechanisms
of deposition, and the number settling varies
as the first power of time. With the 0.14-/*
particles, Brownian motion is the dominant
deposition mechanism, and the number set-
tling varies as the square root of time.
Experiments with stearic acid particles 28
have revealed an interesting phenomenon of
minimal deposition at normal breathing fre-
quencies of 15 to 20 breaths per minute and
an increase when the frequencies were either
higher or lower than this. A range of res-
piratory rates from less than 5 per minute
to more than 35 per minute was used, and
particle diameters lay between 1 /* and 5 /*.
On the other hand, Morrow and Gibb 2Q find
that the deposition of 0.04-/X sodium chloride
particles in dogs and human subjects de-
creases with an increase in breathing fre-
quency. The deposition percentages them-
selves (66.5 percent in dogs, 63.4 percent in
man) are close to those predicted by Fin-
deisen. An increase in tidal volume increased
the deposition in these experiments in dis-
tinction to the absence of a tidal volume ef-
fect found by Brown.
There appears to be a direct relationship
between percentage deposition and holding
time in the lungs for particles of 0.55 /* di-
ameter.30
b. Regional Deposition
The experimental study of regional depo-
sition of particles is more complex than is
the determination of overall total deposition
in the respiratory tract. Various specialized
techniques such as the inhalation of radio-
active particles followed by external count-
ing over specified portions of the chest, or
radioautography of the lungs, have been em-
ployed. The technique of fractionating ex-
haled air and counting the particles in each
fraction has also been used.
(1) Nasal Fractionation. — Lehmann,31
using a test dust of unspecified size, found
a median nasal deposition of 46 percent in
185 normal subjects and 27 percent in 241
silicotics. Dust-laden air was blown through
the nose and out through a tube in the mouth.
Tourangeau and Drinker 32 found deposition
efficiencies of 10 percent to 25 percent with
airflow rates through the nose of 4 to 12
liters per minute. Their dust was calcium
carbonate of a size comparable to the silica
particles found in silicotic lungs. Reversal
of the direction of flow did not alter the
values.
The most extensive experimental studies
of nasal penetration have been made by Lan-
dahl's group.33-34 The results, especially for
corn oil particles, confirm theoretical predic-
tions,15 and nasal deposition is found experi-
mentally to have a strong dependence on air-
flow rate.
(2) Lung Deposition.—Wilson and La
Mer35 used an aerosol of glycerol containing
Na24Cl as a tracer in seven normal subjects
who breathed through the mouth at varying
frequencies. Particle sizes were in the range
of 0.2 p. to 2.5 fi. External chest counts en-
abled estimates of lung burden to be made,
and the pulmonary deposition curve showed
a maximum of about 80 percent for particles
of about 1.6-ju, diameter. A second peak at
0.4 n was interpreted in terms of the differ-
ing optimum sizes for deposition in the finest
airways and in the pulmonary air spaces;
deposition in these two areas was not dis-
tinguished by the method employed.
Indirect estimates of upper respiratory,
alveolar, and total deposition in human sub-
jects were made by Brown et al'.,3S using a
technique for fractionating the exhaled air.
In each successive portion, the C02 content
was measured together with the particle
count and thus the amount of lung air in
each portion of the sample could be esti-
mated. Equal removal efficiencies in both
directions were assumed, and a series of ex-
pressions was developed for calculating total,
alveolar, and upper respiratory deposition.
The median particle size of the china clay
test dust ranged from 0.24 /* to above 5 /*,
and the total retention decreased systemati-
cally from 90 percent or more for particles
5 /j. and greater, down to 25 percent to 30
118
-------
percent for 0.25-/* particles. Tracheobron-
chial retention also decreased systematically
with particle size but reached zero at a finite
size above 1 p. Alveolar retention, calculated
as the percentage of the number of particles
reaching the alveoli, remained between 90
percent and 100 percent for all sizes down to
about 1 fi; below that, it decreased in pro-
portion to total retention. The calculated
curve for alveolar deposition showed an opti-
mum size at 1 /*.
(3) Comparative Human and Animal Re-
tention.—A technique essentially similar to
that used by Brown in his experiments on
human subjects (see Section C-2-a-(2)
above) has been employed by Palm, McNer-
ney, and Hatch 37 for studies on guinea pigs
and monkeys. This provides a valuable
chance to compare results of experiments on
laboratory animals and man. The test dusts
included china clay, carbon, antimony tri-
oxide, and bacillus subtilis var. niger. The
overall pattern of the results was similar in
the experimental animals and in man. The
actual deposition and retention values were
very close for the monkey and for man. For
the guinea pig, total retention was close to
100 percent for 3-/t particles and fell sys-
tematically with decreasing particle size. In
comparison with man, the total retention
was higher, especially in the lower size range.
Alveolar retention was essentially the same
in both species, and it is the tracheobron-
chial retention which i^ higher in the guinea
pig than in man. Although alveolar deposi-
tion in the guinea pig was much lower for
1.5-/J. particles than in man, because of the
removal of these particles in the tracheo-
bronchial tract, the optimum size for alveolar
deposition was similar in both species.
3. Conclusions Reached about Alveolar
Deposition
Three important conclusions may be
reached about the effect of particle size on
alveolar deposition:
1. There is a maximum efficiency of
deposition at a size between about 1 /*
and 2 p.;
2. There is minimum efficiency for a
size of around 0.5 /*; and
3. The percentage of particle deposition
for sizes less than 0.1 p. is just as
great as for sizes more than 1 p (Fig-
ure 9-3). This last conclusion is not
always given enough weight, even
though its prediction by Findeisen 12
has been adequately confirmed ex-
perimentally.26- 29
On the other hand, the importance of the
second conclusion above should not be over-
emphasized, as it refers only to the proba-
bility of deposition. If their number, and
therefore the mass deposited, is relatively
great (as may well be for aged aerosols),
then particles in the 0.1-/J, to 0.5-ju size re-
gion may be as important as smaller and
larger particles in provoking toxic response.
This is also important when considering par-
ticles containing absorbed material.
D. FACTORS AFFECTING THE
CLEARANCE OF PARTICULATE
MATTER FROM THE RESPIRATORY
SYSTEM
A well-known response of a living orga-
nism to foreign matter is its attempt to rid
itself of, or in some way inactivate, the un-
wanted material. The overall effectiveness
of clearance mechanisms in the lung is well
illustrated by the finding that the actual
amount of mineral dust found in the lungs
of miners or city dwellers at autopsy is only
a minor fraction of the total dust that must
have been deposited there during their lives.
The clearance of certain particles may be
very slow. The rate is dependent upon size,
site of deposition, and chemical constitution.
Relative to other factors, the importance
of removal from the respiratory system of
trapped particulate materials depends on the
rate at which the material elicits a patho-
logical or physiological response. The effect
of an irritant substance which produces a
rapid response may depend more on the
amount of initial trapping than on the rate
of clearance. On the other hand, materials
such as carcinogens, which may produce a
harmful effect only after long periods of ex-
posure, may exhibit activity only if the rela-
tive rates of clearance and deposition are
such that a sufficient concentration of mate-
rial remains in the body long enough to cause
119
-------
(a)
NASOPHARYNGEAL
COMPARTMENT
BLOOD
TRACHEOBRONCHIAL
COMPARTMENT
T
(b)
Id)
TT
lf)J *(g)
PULMONARY
COMPARTMENT
GASTRO-
INTESTINAL
TRACT
FIGURE 9-7. Schematic Portrayal of Dust Deposition Sites and Clearance Processes. (This diagram illus-
trates the various deposition sites and clearance mechanisms used in the model of the lung developed
by the Task Group on Lung Dynamics, and described in the text.)
pathological change. In such a case, the
amount of initial deposition will be of rela-
tively minor importance.
Different clearance mechanisms operate in
the different portions of the respiratory tract,
so that the rate of clearance of a particle
will depend not only on its physical and
chemical properties such as shape and size,
but also on the site of initial deposition. Fur-
thermore, the presence of a nonparticulate
irritant or the coexistence of a disease state
in the lungs may interfere with the efficiency
of clearance mechanisms and thus prolong
the residence time of particulate material in
a given area of the respiratory tract. Kotin
and Falk 38 have emphasized the possible im-
portance of this interaction in the patho-
genesis of lung cancer (Chapter 10).
1. Clearance Model
The Task Group on Lung Dynamics * con-
sidered the respiratory clearance of particu-
late matter, as well as its deposition, and the
model they developed provides a convenient
starting point for a discussion of experimen-
tal work on clearance.
Figure 9-7 presents a schematic diagram
of all deposition sites and clearance proc-
esses. The three conventional compartments
of the respiratory tract discussed in connec-
tion with the deposition model are used here.
DI is the particulate material inhaled; D2
is the material in the exhaled air; D3, D4, and
D5 are the particles deposited in the naso-
pharyngeal, tracheabronchial, and pulmonary
compartments respectively, expressed as per-
centages of Dj and determinable from the
deposition model. In addition to the respira-
tory tract, three other compartments are
listed: The gastrointestinal tract, systemic
blood, and the lymph. The different absorp-
tion and translocation processes which are
associated with the clearance of various com-
partments are as follows:
120
-------
a. Rapid uptake of material deposited
in the nasopharynx directly into the
bloodstream.
b. Rapid clearance of all particulate
matter from the nasopharynx by cil-
iary transport of mucus. This route,
and d, have clearance half-times of
minutes.
c. Rapid absorption of particles de-
posited in the tracheobronchial com-
partment into the systemic circula-
tion.
d. The rapid ciliary clearance of the
tracheobronchial compartment. Par-
ticles cleared by this route go quan-
titatively to the gastrointestinal tract.
e. The direct translocation of material
from the pulmonary region to the
blood.
f. The realtively rapid clearance phase
of the pulmonary region dependent
on recruitable macrophages. This in
turn is coupled to the ciliary mucus
transport process for which a half-
time of 24 hours has been suggested.
g. A second pulmonary clearance proc-
ess, much slower than f, but still de-
pendent upon endocytosis and ciliary
mucus transport. This process is
rate-limited in the pulmonary region
by the nature of the particles per se.
h. The slow removal of particles from
the pulmonary compartment via the
lymphatic system.
i. A secondary pathway in which par-
ticles cleared by pathway h are intro-
duced into the systemic blood.
j. The collective absorption of cleared
material from the gastrointestinal
tract into the blood. No attempt is
made to include this factor in the de-
velopment of the model.
The use of the model requires a knowledge
of values for two parameters for each of the
pathways just described. These are the
amount of material residing in the compart-
ment which follows a particular exit path
(regional fraction), and the rate at which
that fraction of the material is cleared (bio-
logical half-time). In some cases the kinetic
values are physiologically controlled and are
more or less independent of the nature of
the particulate material. In other cases the
physiochemical nature of the deposited mate-
rial is the critical factor.
A classification of inorganic compounds is
given in the Task Force Group Report, which
contains the best available information on"
both deposition and clearance of inhaled
particles.
The Task Force Group stressed the need
for research in the area of solubilities of
various compounds in water, in very dilute
alkali, and in the presence of proteins. Some
of the work done by Morrow et al.39 corre-
lates clearance of material from the lungs
with other properties such as ultrafilterabil-
ity and clearance from intramuscular injec-
tion sites. These data will be of value in
understanding the effect of physiochemical
properties on clearance.
It will be seen that the clearance mecha-
nisms can be divided broadly into those de-
pending on ciliary action and those which
operate in the virtually nonciliated pulmo-
nary region. The two sections which follow
describe experimental work concerned with
these two general subdivisions.
2. Clearance from the Tracheobronchial
System
A blanket of mucus in the tracheobron-
chial region is kept in continual upward
movement by the ciliary activity of the col-
umnar epithelium lining which extends down
as far as the terminal bronchioles. The fre-
quency of the ciliary beat has been found 40-41
to be 1,300 per minute in the rat, while the
overlying mucous fluid was found to move
at an average rate of 13.5 mm per minute.
Similar transport rates of 15 mm per min-
ute in excised trachea, and 18 mm per min-
ute in intact animals, have been reported by
Antweiler.42 In this latter study, several par-
ticulate materials were used, including soot,
coal dust, lycopodium spores, cork dust, alu-
minum powder, and glass and lead spheres.
Transport rates seemed to be unaffected by
size- weight, or shape of the particles except
in the case of the glass spheres, which were
said to be sufficiently smooth to allow the
121
-------
mucus to flow over them rather than to trans-
port them.
It has been demonstrated 43-44 that in the
human lung the mucus flows over only 10
percent to 20 percent of the theoretically
available surface at the dividing passages
where the airways branch. The mucous
blanket divides and flows in two directions
around the margins of the opening. This
phenomenon, taken together with the greater
probability of impact deposition at bifurca-
tions, may explain why histological sections
show accumulations of particles at bronchial
branch points.45
In studies of respiratory system clearance,
use has been made of mono-disperse aerosols
tagged with radioactive substances to per-
mit the subsequent fate of the material to
be followed by external counting techniques.
In general, the results indicate that clear-
ance occurs in two distinct phases of about
two and ten hours duration, probably repre-
senting the clearance of particles from the
proximal and distal parts of the bronchial
tree. Albert et al,46 studied clearance from
the human lung of 3-/x and 5-/* iron oxide
particles tagged with 51Cr and 198Au. The
rapid phase of clearance was completed with-
in one day, and in most cases within 12
hours. The clearance curves obtained in
these studies did not differ substantially
from those obtained earlier by Albert and
Arnett" who used a heterogeneous iron ox-
ide aerosol, suggesting that.the actual dis-
tribution function of particle sizes may be
of little importance in determining clearance
rates. However- Holma48 generated a "bi-
disperse" aerosol of 6-//, and 3-/x polystyrene
particles, tagged respectively with 19sAu and
46Sc, and measured simultaneous clearance
of the two sizes in rabbits. The larger par-
ticles cleared more rapidly than the smaller
ones. The mean half-life for the initial phase
was 0.48 hours for the Q-/J. particles and 1.07
hours for the S-/* particles. The respective
half-lives for the long clearance phase were
69.7 hours and 210 hours.
The effect of irritant gases on clearance of
particles is obviously of significance where
air pollution involves this combination of
factors.
Dalhamn's40-41 studies showed that the
acute response to irritant gases such as am-
monia, formaldehyde, or sulfur dioxide was
a cessation of ciliary beat. The time to ces-
sation was dose-related. Chronic exposure
of rats to one of the irritants (sulfur dioxide)
slowed down or caused a complete cessation
of the transport of tracheal mucus, but the
average beat frequency of the cilia was the
same as in normal animals. The cessation
of clearance was a result of an increase in the
thickness of the mucous layer of from 5 //.
to 25 /x.
The material carried upward by ciliary
action is swallowed and thus enters the gas-
trointestinal tract. Brieger and LaBelle49
exposed animals to a water-insoluble dye and
demonstrated that 24 hours after the termi-
nation of exposure, over 50 percent of the
total dye found in the body was in the in-
testinal tract. This phase could persist for
several days, during which time a significant
intestinal burden was present. The concen-
tration of dye finally fell to very low values
after a week or so, and most of the dye that
remained in the body was found in the lung,
indicating that the rapid phase of ciliary
clearance was finished. It has also been
shown 50 that uranium dioxide, cleared from
the respiratory system to the gastrointestinal
tract by ciliary action, is responsible for the
high urinary uranium levels seen during the
first days after exposure to uranium dioxide
dust. The possibility of consequences of rela-
tively high concentrations of an atmospheric
pollutant appearing in organs remote from
the lungs must not be overlooked. In this
connection, the high incidence of stomach
cancer in areas suffering from high levels
of atmospheric pollution takes on a particu-
larly ominous appearance.
3. Clearance from the Alveolar Surface
Particles deposited on the alveolar sur-
face may be removed by any of the mecha-
nisms (e) to (i) given in the clearance model
of Section D-l, and they may also become
sequestered by a tissue reaction within the
lung (pneumoconiosis), or become bound to
protein material in the lungs. Of the sev-
eral clearance mechanisms, the most rapid is
that involving recruitable macrophages
(phagocytic cells contained on the alveolar
122
-------
surface epithelium). Phagocytosis may also
serve to render the particles incapable of in-
juring or irritating the alveolar surface epi-
thelium and may to some extent prevent the
penetration of the particles into the inter--
stitium of the lung. The origin and behavior
of these alveolar macrophages have been
the subjects of active research in recent
years.45- 51~53
LaBelle M-5S demonstrated that the clear-
ance of particulate matter by phagocytosis
can be markedly influenced by the dust load
presented to the lung. The initial observa-
tion was made that clearance curves obtained
with microgram quantities of activated ura-
nium dioxide were noticeably different from
those obtained earlier using milligram
amounts. When carbon particles were added
to the activated uranium dioxide to bring
the total weight of administered dust into
the range of the earlier studies, the clearance
curves were quite similar. In seeking the
reason for this finding. LaBelle demon-
strated that the number of free phagocytes
washed out of the lungs was related to the
dust load and that the amount of dust elimi-
nated from the lungs during the early post-
exposure period was proportional to the num-
ber of free phagocytic cells present. Within
the limits of experimental error, the kinetics
of elimination of particles and the kinetics
of the disappearance of the phagocytic cells
following exposure were identical for both
inhalation and intratracheal exposures.
The relationship between concentrations in
the different respiratory regions during al-
veolar clearance has been the subject of a
short-term study by Gross, Pfitzer, and
Hatch.58 The clearance of four kinds of dust
burdens (antimony trioxide, ferric oxide,
quartz, and coesite) was followed in rats
whose lungs had been loaded using the in-
halation and intratracheal injection tech-
niques. Initially, although the greater con-
centration of dust was to be found in the
proximal alveoli, dust deposition was also
prominent in alveoli distal to alveolar ducts.
However, within 3 or 4 days, the dust in the
distally situated alveoli had largely disap-
peared and had apparently become concen-
trated in the proximal alveoli. This stagna-
tion of dust in the evaginating alveoli of the
respiratory bronchioles and alveolar ducts
may help to explain the greater vulnerability
of these regions to inhaled irritants.
E. SUMMARY
The respiratory system may be divided
into three sections—nasopharyngeal, tra-
cheobronchial, and pulmonary systems. Dep-
osition and clearance mechanisms may differ'
for the various parts of the respiratory tract.
A particle of any size which passes the naso-
pharyngeal region may be deposited in the
remainder of the respiratory tract and, al-
though the actual mechanism of deposition
is primarily dependent upon the particle size,
the shape of the particle can also affect the
efficiency of its deposition. Consequently, if
atmospheric dust loads are to be related
quantitatively to health hazards, the dust
samplers used for monitoring should have
collection characteristics similar or the same
as the human lung. The fast phases of the
lung clearance mechanisms are different in
ciliated and nonciliated regions. In cil ated
regions, a flow of mucus transports the par-
ticles to the entrance of the gastrointestinal
tract, while in the nonciliated pulmonary re-
gion phagocytosis by macrophages can trans-
fer particles to the ciliated region. The rate
of clearance is an important factor in de-
termining toxic responses, especially for
slow-acting toxicants such as carcinogens.
In addition, since the clearance of particles
from the respiratory system primarily leads
to their entrance into the gastrointestinal
system, organs remote from the deposition
site may be affected. The models developed
by the Task Group on Lung Dynamics are
used in this chapter as a basis for discussion
of experimental data on the deposition, re-
tention, and clearance of particles. These
models provide a useful representation of
the deposition and clearance mechanisms and
have been shown to yield predictions which
have often been substantiated by experimen-
tal findings.
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cles and Vapours, Vol. II, C. N. Davies (ed.),
Pergamon Press, London, 1967, pp. 361-378.
47. Albert, R. E. and Arnett, L. C. "Clearance of
Radioactive Dust from the Lung." Arch. Ind.
Health, Vol. 12, pp. 99-106, 1955.
48. Holma, B. "Short Term Lung Clearance in Rab-
bits Exposed to a Radioactive Bi-disperse (6
and 3) Polystyrene Aerosol." In: Inhaled Parti-
cles and Vapours, Vol. II, C. N. Davies (ed.),
Pergamon Press, London, 1967, pp. 189-203.
49. Brieger, H. and LaBelle, C. W. "The Fate of
Inhaled Particulates in the Early Postexposure
Period." Arch. Ind. Health, Vol. 19, pp. 510-515,
1959.
50. Downs, W. L. "Excretion of Uranium by Rats
Following Inhalation of Uranium Dioxide."
Health Physics, Vol. 13, pp. 445-453, 1967.
51. Casarett, L. J. "Some Physical and Physiologi-
cal Factors Controlling the Fate of Inhaled Sub-
stances. II. Retention." Health Physics, Vol.
2, pp. 379-386, 1960.
52. Casarett, L. J. and Milley, P. S. "Alveolar Re-
activity Following Inhalation of Particles."
Health Physics, Vol. 10, pp. 1003-1011, 1964.
53. Policard, A., Collet, A., and Pregermain, S.
"Structures alveolaires normales du pneumon
examines au microscope electronique." Semaine.
Hop. (Paris), Vol. 33, p. 385, 1957.
54. LaBelle, C. W. and Brieger, H. "Synergistic
Effects of Aerosols. II. Effects on Rate of Clear-
ance from the Lung." Arch. Ind. Health, Vol. 20,
pp. 100-105, 1959.
55. LaBelle, C. W. "Patterns and Mechanisms in
the Elimination of Dust from the Lung." In:
Inhaled Particles and Vapours, Vol. 1, C. N.
Davies (ed.), Pergamon Press, London, 1961, pp.
356-368.
56. Gross, P., Pfitzer, E. A., and Hatch, T. F. "Al-
veolar Clearance: Its Relation to Lesions of the
Respiratory Bronchiole." Am. Rev. Respirat.
Diseases, Vol. 94, pp. 10-19, 1966.
125
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Chapter 10
TOXICOLOGICAL STUDIES OF
ATMOSPHERIC PARTICULATE MATTER
-------
Table of Contents
Page
A. INTRODUCTION .129
B. MECHANISMS OF TOXICOLOGICAL ACTION OF PARTICULATE
MATTER 129
1. Intrinsic Toxicity 129
2. Absorbed Substances . . . 130
3. Reduction of the Toxicity of Irritant Gases . . 130
C. TOXICOLOGICAL STUDIES OF SPECIFIC PARTICULATE
MATERIALS 131
1. Pathological Studies of Smoke and Carbon Particles 131
2. Physiological Studies of Response to Particulate Material . 132
3. Experimental Studies of Mixtures of Irritant Gases and Particulate
Material . . 134
D. CARCINOGENESIS 137
1. Carcinogens . 137
2. Polynuclear Aromatic Hydrocarbons as Carcinogens in Polluted
Atmospheres 138
3. Pathology of Carcinogenesis . 141
E. SUMMARY . 141
F. REFERENCES . . .... 142
List of Tables
Table
10—1 Effect of Exposure of Rabbits to 2 ppm Ozonized Gasoline on Re-
tention of Inhaled Soot . . 134
10-2 Benzo (a) pyrene Concentrations in Several Urban and Nonurban
Areas ... . 138
10-3 Benzo (a) pyrene as a Fraction of the Total Aromatic Hydrocarbon
Content of Several Urban Atmospheres . 138
10-4 Effect of Various Conditions of Exposure on the Destruction of
Some Polynuclear Aromatic Hydrocarbons 139
10-5 Percentage Recovery of Polynuclear Aromatic Hydrocarbons from
0.5m Soot Particles and from Plasma after Incubation with Plasma
for Varying Periods . 140
10-6 Distribution of Lung Cancer by Site of Origin . 141
128
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Chapter 10
TOXICOLOGICAL STUDIES OF ATMOSPHERIC PARTICIPATE MATTER
A. INTRODUCTION
Experimental toxicology, using specific
atmospheric pollutants, would be the best
means for deriving air quality criteria, pro-
vided that man could be used as the experi-
mental animal. However, the ethical impos-
sibility of performing experiments using
human exposures to varying concentrations
of a wide range of compounds precludes so
direct an approach. Although a limited
amount of intentional human experimenta-
tion may be possible, most of the data for
human toxocology are derived from acci-
dental or occupational exposures. The use of
laboratory animals in toxicological experi-
ments is more straightforward, but the ob-
vious anatomical and metabolic differences
between the animals and man require the ex-
ercise of considerable caution in applying the
results of animal exposures to human health
criteria. Furthermore, many of the animal
experiments performed have left something
to be desired in terms of air pollution toxicol-
ogy, since the "end-point" of the experiments
has frequently been the death of the animals
at exposures to concentrations far in excess
of those likely to be found, or tolerated, in the
atmosphere. There is a great need for chronic
inhalation studies to define long-term effects
occurring over a lifespan.
The difficulties and limitations of toxico-
logical studies discussed in the last para-
graph should not obscure the fact that an in-
creasing amount of data useful for air quality
criteria is being amassed; it is, however, al-
ways essential to bear in mind the limitations
of the data. Toxicological studies have shown
that atmospheric particles may elicit a path-
ological or physiological response in at least
three ways. First, the particle may be in-
trinsically toxic; second, the presence of an
"inert" particle in the respiratory tract may
interfere with the clearance of other air-
borne toxic materials; and third, the particle
may act as a carrier of toxic material. There
is also evidence that the presence of particles
may occasionally reduce the toxicity of a
second pollutant; this phenomenon is de-
scribed briefly. From an air pollution stand-
point, one of the most ubiquitous particulate
pollutants is smoke; some pathological stud-
ies involving this material are presented.
Studies of physiological response to irritant
particles and to mixtures of particulate mat-
ter with irritant gases are described.
A final section of this chapter then deals
with carcinogenesis and atmospheric pol-
lutants.
B. MECHANISMS OF TOXICOLOGICAL
ACTION OF PARTICULATE MATTER
1. Intrinsic Toxicity
Few common atmospheric particulate pol-
lutants appear to be intrinsically toxic; of
these, the most important toxic aerosol is
sulfur trioxide (S03) (either as the free
oxide, or hydra ted as sulfuric acid—H2SO4),
which has a high degree of toxicity, at least
for the guinea pig. Although silica (from fly
ash) is frequently present as a pollutant, at-
mospheric concentrations are normally too
low to lead to silicosis. In recent years, how-
ever, concern has been expressed over a num-
ber of less common toxic particulate pollut-
ants, including lead, beryllium, and asbestos.
Increasing amounts of lead (as oxides and
salts) are being discharged into the atmos-
phere as a result of the burning of gasoline
containing lead additives; on the other hand,
other sources contributing to atmospheric
lead seem to be decreasing and, according to
Stokinger and Coffin,1 toxic effects due to
129
-------
lead do not seem to present a serious risk to
the population at large. Beryllium (as the
oxide BeO) can lead to chronic pulmonary
disease with a high fatality rate. Accidental
exposures have shown that there may be a
considerable latency period before disease
develops, and some alarm has been generated
over the use of beryllium as a rocket fuel,
although the rocket effluent is predominantly
a "high-fired," relatively inert form of beryl-
lium oxide. The situation with regard to as-
bestos is also potentially serious. Brief in-
dustrial or accidental exposures to asbestos
can lead, after a latency period of 40 years
or more, to the development of diffuse meso-
theliomas of the pleura or peritonium, and it
is possible that sufficient levels of asbestos
might be generally present in the atmosphere
to constitute a definite health hazard. This
possibility is made more likely by the greatly
increased use of asbestos since the occur-
rence of the exposures which are only now
leading to the development of mesotheliomas.
A series of autopsies has shown that an ap-
preciable fraction (20 percent to 50 percent)
of the population at large has "asbestos
bodies" in its lungs. More detailed discussions
of both asbestos 2 and beryllium3 toxicity
may be found in recent reviews.
Several other potential carcinogens are
known to be present as relatively minor at-
mospheric pollutants; these may be particu-
late in nature, and they are discussed in
Section D.
2. Adsorbed Substances
Toxic substances may be adsorbed on the
surface of particulate matter, which may
then carry the toxic principle into the respi-
ratory system. The presence of carbon or
soot as a common particulate pollutant is
noteworthy, as carbon is well known as an
efficient adsorber of a wide range of organic
and inorganic compounds. Some specific stud-
ies involving mixtures of particulate matter
and irritant gases are presented in Section
C-3; the present section is concerned mainly
with the general principles of adsorption and
desorption.
The role played by the affinity for the ad-
sorbate by the particle is complex. A high af-
finity will mean that relatively large loads of
adsorbate may be carried by each particle. If
the adsorbate in its free state is slowly re-
moved from the air in the respiratory system,
then the deposition of particles carrying high
concentrations may constitute a greater toxic
hazard, especially at the localized deposition
points. Whether or not the effect is signifi-
cant depends on the efficiency of the desorp-
tion and elution process relative to that of the
clearance process. The chemical nature of
both adsorber and adsorbate, and the size of
the adsorbing particle, all play a part in de-
termining these various efficiencies, and each
system will show its own individual charac-
teristics. Carcinogens, which may produce
their effect only after long or repeated ex-
posure, present a particularly involved situa-
tion, because it is not clear whether slow re-
lease of small concentrations of the carcino-
gen is more dangerous than the rapid release
of larger quantities. Experimental evidence
on the elution of a specific series of carcino-
gens is described in Section D-2.
3. Reduction of the Toxicity of Irritant
Gases
The finding that a preexposure to particu-
late material will tend to protect animals
against the action of an irritant gas is not an
uncommon one.
Pattle and Burgess " found that, with mice
and guinea pigs, the previous inhalation of
smoke reduced the toxicity of sulfur dioxide
(measured in terms of the dosage required
to produce death). They postulated that the
reduced toxicity of SOo produced by preex-
posure to smoke was due either to the action
of the smoke in reducing the volume breathed
(and thus the S02 dose received), or to a
stimulation of secretions which may protect
the mucosa from the irritant action of the
gas. This explanation is given weight by their
findings that increased toxicity resulted from
the administration of mixtures of smoke and
sulfur dioxide. A similar study by Salem and
Cullumbine 5 indicated that the effect of kero-
sene smoke on the toxicity of irritant sub-
stances depended to some extent on the spe-
cies of animal, although the toxicity of acro-
lein and acetaldehyde seemed to be decreased
in most cases.
Wagner et al.® observed that the preex-
130
-------
posure of mice to oil mists would protect
against the later action of inhaled ozone and
nitrogen dioxide. The greatest protection was
obtained when the oil mist was given 18
hours prior to the exposure to the irritant
gas; when the oil mist and irritant gas were
given together, there was an enhancement of
toxicity. The relative degree of this enhance-
ment was consistent with the known depth of
penetration of nitrogen dioxide and ozone in
the respiratory tract and the relative solubil-
ity of the two gases in mineral oil. The hy-
pothesis for the protective action of the pre-
treatment with oil is the formation of an oil
film on the aveolar surface.
Again- Amdur and Devir,7 using guinea
pigs, have observed that the presence of an
aerosol of 2.5/* triphenyl-phosphate particles
at a concentration of 50 mg/m3 to 100 mg/m3
lessens the increase in pulmonary flow re-
sistance due to inhalation of sulfur dioxide.
They then studied the eifect of treatment
with the particulate material before expo-
sures to sulfur dioxide alone. This sequence
afforded excellent protection against the re-
sponse to the sulfur dioxide, and the degree
of protection was related to the total amount
of aerosol inhaled.
C. TOXICOLOGICAL STUDIES OF
SPECIFIC PARTICULATE MATERIALS
1. Pathological Studies of Smoke and
Carbon Particles
Smoke from burning bituminous coal was
used for a study on rabbits and rats by
Schnurer and Haythorn.8 Four rabbits and
eight rats were exposed for periods of 80
days to smoke with a concentration of 125
million particles/ft3 (4410 particles/cm3), of
which 8 percent was free Si02. Control ani-
mals received clean filtered air. One control
rabbit and two exposed rabbits died of bron-
chial pneumonia before the end of the expo-
sure. One rabbit and six rats were autopsied
immediately after exposure, and the rest at
intervals up to 429 days. Lesions typical of
nonoccupational anthracosis were noted in
the lungs of the animals killed immediately
after exposure, while fibrous reactions de-
veloped around the carbon deposits (with the
formation of collagen strands) in the animals
that were examined several months to a year
after the exposure. The authors state that
these lung changes were analogous to those
seen in a milder grade of bituminous pneu-
moconiosis of soft-coal miners, and they also
concluded that the pneumonitis and fibrosis
were attributable to the carbon rather than
to the small amount of silica present.
Schnurer h has also attempted to compare
the response to the burning of equal weights
of anthracite coal, coke, and bituminous coal.
Unfortunately, widely differing particle con-
centrations were obtained from burning equal
weights of fuel, so that it is impossible to
place any simple interpretation on the re-
sults of the experiments.
Pattle et al.w studied the acute toxic effects
of smoke, generated by burning tetrahydro-
naphthalene in the concentration range of
700 mg/m3 to 1100 mg/m3. They found that
the median dosage to death for guinea pigs
and mice lay between 147,000 mg—min/m3 to
351,000 mg—min/m3. In mice, the cause of
death was blockage of the air passages and
delayed death resulting from the exposure
was unusual. The guinea pigs showed hemor-
rhagic lesions, and delayed deaths were more
common. The action of smoke on rats re-
sembled that on mice. No data are provided
to show that unburnt tetrahydronaphthalene
did not enter the smoke stream in these ex-
periments, since toxic effects are well known
for this substance.
In the course of a study of mixtures of
sulfur dioxide and smoke, to be discussed in
Section C-3, Pattle and Burgess * reported
some data on the effect of smoke alone on
mice. The smoke was generated by a burning
kerosene lamp, and its concentration was
about 50 mg/m3. The experiment continued
for 36 hours followed by a gap of 11 hours.
The experiment was subsequently continued
for 30 hours. There were no fatalities and
none occurred after the experiment. Histo-
logical examination of the lungs shewed that
at the end of exposure the soot particles were
partly spread over the lining of the bron-
chioles and alveoli and partly aggreg ated into
patches. There were no signs of edema, con-
solidation, hemorrhage, or emphysema' and
capillary congestion was slight. The lungs
were normal except for the presence of car-
131
-------
bon particles, and animals killed 3 months
after exposure showed phagocytosis and
gradual clearance of smoke from the lungs.
Salem and Cullumbine5 also make brief
mention of the exposure of mice and guinea
pigs to smoke from a kerosene lamp. The
animals survived exposure to 664 mg/m3 of
smoke for 6 hours, and autopsy revealed no
obvious damage to the lungs.
The physiological effects on mice of ex-
posure to carbon black by ingestion, skin con-
tact, subcutaneous injection, and inhalation
were examined by Nau et aZ.11-" Channel
black (particle diameter 0.025//,) and furnace
black (particle diameter 0.035/x.) were used in
concentrations of 2.4 mg/m3 and 1.6 mg/m3
respectively for the inhalation experiments.
Mice, hamsters, guinea pigs, rabbits, and
monkeys were exposed for prolonged periods
to the dust, but no effect other than the ac-
cumulation of carbon particles in the lungs
was demonstrated.
The problem of whether exposure of rats
to coal dust or smoke would alter their sus-
ceptibility to infection by Type I pneumo-
cocci was examined by Vintinner and Baet-
jer 15 as part of a series of studies on the ef-
fect of fibrous, inert, and adsorptive dusts on
susceptibility to infection in experimental
animals.16-18 The concentration of coal dust
varied between 400 and 850 million particles/
ft3 with an average of 700 million particles/
ft3. The smoke level in the chambers would
have been considered as "dense" on visual
inspection, or equivalent to about a Number
3 reading on the Ringelmann Chart. Analyses
of the particulate matter in mg/m3 in the
smoke chamber averaged as follows: Total
solids—570, carbon—470, ash—93, silica—
46, iron—15, and sulfur—9, that is, about
100 times the values listed as "average com-
position of susupended dust during the win-
ter months for all cities." The exposures
ranged from 5 days to 165 days for the bitu-
minous coal dust and from 2 days to 154 days
for the smoke. On the basis of their extensive
data, the authors concluded that the inhala-
tion of smoke did not alter the susceptibility
to infection when the organisms, either in
broth or in mucin, were administered by in-
trabronchial injection. The bituminous coal
dust seemed to exert a slight protective effect
when the organisms were suspended in mucin
but not when they were injected in a broth
medium.
Based upon the reported studies, smoke or
carbon black on its own apparently produces
little major damage to the respiratory system
of animals even at exposure levels some
orders of magnitude greater than those en-
countered in polluted atmospheres.
2. Physiological Studies of Response
to Particulate Material
Certain particulate materials are pulmon-
ary irritants which have been shown to pro-
duce alterations in the mechanical behavior
of the lungs, the alteration being predomi-
nantly an increase in flow resistance. This
was demonstrated by Amdur 19 for sulfuric
acid, and by Amdur and Corn20 for am-
monium sulfate, zinc sulfate, and zinc am-
monium sulfate, using the guinea pig as an
assay animal. (The decreased flow rates ob-
served by Amdur, Silverman, and Drinker 21
in human subjects exposed to sulf uric acid
mist probably reflect an increase in flow re-
sistance, although, since the resistance was
not measured in those experiments, such a
statement cannot be conclusive.) A series of
papers making use of the increase in pulmon-
ary flow resistance as an assay tool has been
published by Amdur,22-27 and "response" to
an irritant in discussion of her work general-
ly refers to this increase.
Nadel et al.z* report a correlation between
the alterations in pulmonary mechanics and
actual anatomical change in cats exposed to
aerosols of histamine and zinc ammonium
sulfate. The authors discuss the physiological
mechanisms which may operate to bring
about such alterations in pulmonary me-
chanics.
In connection with a study of the effect of
various aerosols on the increase in pulmonary
flow resistance in guinea pigs produced by
sulfur dioxide, Amdur and Underhill22 first
examined the response to the aerosols alone.
These aerosols included spectrographic car-
bon at 2 mg/m3 and 8 mg/m3, activated car-
bon at 8.7 mg/m3, manganese dioxide at 9.7
mg/m3, open hearth dust at 7.0 mg/m3, iron
oxide (Fe203) at 11.7 mg/m3 and 21.0 mg/m3,
manganous chloride and ferrous sulfate at
132
-------
1 mg/rn3- and sodium orthovanadate at 0.7
mg/m3; the particle sizes were less than 0.5/*.
Standard one-hour exposures were used in
this routine bioassay method, with the ex-
ception of the iron oxide exposures, which
were extended to two hours. In no instance
did any of the aerosols produce an alteration
in flow resistance. The failure of the aerosols
to produce an increase in resistance in these
experiments suggests that if they cause bron-
chial constriction, it must be only in extreme-
ly high concentrations. From the point of
view of air pollution toxicology, none of them
would be classed on this basis as pulmonary
irritants. An uncharacterized "fly ash" from
an oil-fired burner was also tested and proved
inert.
At a concentration of 1 mg/m3, ferric sul-
fate aerosol produced a 77 percent increase in
flow resistance in a group of 15 animals
which was statistically significant at the level
of P<0.001. Ferric sulfate, in distinction to
ferrous sulfate, must be classed as an irri-
tant.
On the other hand, Dautrebande and Du-
Bois 29'30 have reported constriction and in-
creased airway resistance in isolated guinea
pig lungs and in human subjects with a wide
variety of supposedly "inert" particulate mat-
ter. The relationship of their results to Am-
dur's work is not clear since Dautrebande's
particle concentrations appear to be ab-
normally high. Total lung capacity and vital
capacity were not altered by the inhalation
of particulate material in healthy subjects,
but the vital capacity in patients with pul-
monary disease was reduced by the inhala-
tion of particulate materials. It is interesting
in this connection that guinea pigs with an
initially high pulmonary flow resistance
showed a greater response to low concen-
trations of irritant aerosols or of inert aero-
sol-irritant gas combinations than animals
with average control flow resistance values.31
The possibility that the conflict between
Amdur's and Dautrebande's work may be
resolved in terms of the doses involved is
given credence by studies which suggest that
human response to coal dust may be dose-
related.32 Coal dust clouds similar to those in
mines have been produced in the laboratory,
and the number and weight of respirable par-
ticles have been measured. Clouds containing
8 mg/m3, 9 mg/m3, 19 mg/m3, 33 mg/m3, and
50 mg/m3 dust in the size range of I/* to Ip
were used. Normal subjects inhaled the dust
for 4 hours, and airway resistance was meas-
ured with a body plethysmograph. No chang-
es were obtained after the inhalation of coal
dust from clouds containing 8 mg/m3 or 9
mg/m3; but with concentrations of 19 mg/m3,
33 mg/m3. and 50 mg/m3, significant in-
creases in airway resistance occurred and
the response was correlated with the quan-
tity of dust. One hour after exposure ceased,
the airway resistance was about two-thirds
back to normal. With the two highest concen-
trations, the respiratory rate increased
throughout the 4 hours, and subjects com-
plained of difficulty in breathing after one to
two hours. It would appear that if 8 mg/m3
or 9 mg/m3 produced no lung function change
in a 4-hour period, the material (cold dust)
and perhaps other "inert" particulate matter
would be unlikely to do so at any concentra-
tions likely to occur in air pollution. In Chap-
ter 1, Table 1-2 shows a maximum geometric
mean concentration of urban particulates in
1961 to 1965 of 180 ^g/m3.
Particle size may "play an important part
in determining the potency of an irritant.
For example, at a mass concentration of 1.4
mg/m3 to 1.9 mg/m3, sulfuric acid mist of
0.8/i produces a 51 percent increase in pul-
monary flow resistance in guinea pigs as
compared to control values,19 and zinc am-
monium sulfate particles of 0.84//, produce a
21 percent increase.25 If the zinc ammonium
sulfate size is 0.3/x' the corresponding in-
crease in pulmonary flow resistance is 130
percent.20 The studies on zinc ammonium
sulfate were carried out by Amdur and
Corn 20 with nonhomogeneous aerosols with
mean sizes by weight of 0.24/*, 0.51/j., 0.74^,
and 1.4/x, at several concentrations. As the
particle size decreased over the range 1.4ju
to 0.29/*, the response to an equal mass con-
centration rose. When dose-response curves
of percent increase in flow resistance against
concentration in mg/m3 were plotted for the
different particle sizes, the slopes increased
as the particle size decreased. A similar study
was undertaken by Amdur and Creasia33
using m-terphenyl as the aerosol (size range
133
-------
0.3/* to 2.0^); this aerosol does not absorb
water during passage through the respira-
tory tract. An essentially, identical pattern to
that seen for zinc ammonium sulfate
emerged, with the irritant potency increasing
with decreasing particle size, and the slopes
of the dose-response curves steeper than
those for the smaller particles. All of the
particles used in these studies fall within
the "respirable size range." The possible im-
plications for air pollution are:
1. Particles below lju. may have greater
irritant potency than larger species,
and
2. A small increase in concentration
could produce a greater-than-linear
increase in irritant response when
the particles are smaller than 1^.
The effect of particulate matter on clear-
ance mechanisms has already been men-
tioned. The deposition of particles affects
mucous secretion and ciliary action most
markedly at branchings; e.g., miniature
ridges throughout the tracheobronchial tree
as contrasted with intervening areas, and it
is in the ridge areas that alterations in the
morphology are initially most intense and
prolonged and ultimately irreversible. The
adverse effect is manifested by a slowing of
the flow of the mucous stream, alteration in
the physical and chemical properties of
mucus, and changes in ciliary action.
Examination of sections of respiratory
epithelium removed from the lungs reveal
hyperplastic and metaplastic changes earli-
est at these sites. The exaggerated effect of
the impingement of irritants on respiratory
epithelium at branch points taken together
with less efficient clearance is consistent with
this result. Thus, abnormal retention and ac-
cumulation of soot (and possibly carcinogenic
particles) may occur, especially in segmental
bronchi. The accompanying peribronchial
and peribronchiolar inflammatory response
further interferes with physiologic mechan-
isms of defense.
Experimental confirmation of enhanced re-
tention in the presence of irritant material
is to be found in the work of Tremer et al.,3i
who exposed rabbits first to synthetic smog
and then to soot. The results are shown in
Table 10-1.
The main conclusions of this section are:
1. The predominant physiological effect
of irritants is to increase pulmonary
flow resistance;
2. Exceptionally heavy loads of rela-
tively inert particles may cause some
increase in flow resistance; and
3. The intensity of physiologic response
may increase with a decrease in par-
ticle size for any given irritant.
3. Experimental Studies of Mixtures of
Irritant Gases and Particulate Material
The possible influence of inert particulate
matter on the toxicity of irritant gases has
been the subject of considerable specula-
tion 3r>-37 and a limited amount of experimen-
tal work. Such interaction of gaseous and
particulate pollutants might be important
to understanding the complicated toxicologi-
cal picture of the air pollution disasters.
Table lfr-1.—EFFECT OF EXPOSURE OF RABBITS TO 2 PPM OZONIZED GASOLINE ON RETENTION
OF INHALED SOOT.
Specimen
Smog
exposure,
hours
Room air
(recovery),
hours
Soot
exposure,
hours
Room air
(recovery),
hours
Soot in
lung,
mg
No recovery period after smog exposure:
Control .. 0
Animal No. 1 1
Animal No. 2 . . 1
With varying recovery periods:
Control . . . 0
Animal No. 1 1
Animal No. 2 1
Animal No. 3 ... 1
0
0
0
0
4
8
24
0
0
24
0
0
0
0
3.7
7.9
5.4
1.1
7.4
5.2
2.0
134
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The first experimental evidence that an
inert aerosol could alter the response to an'
irritant gas was presented in 1939,38 when
it was reported that concentrations of mus-
tard gas which were relatively harmless to
rats would produce pulmonary edema and
death when administered in combination
with an inert aerosol (sodium chloride). It
was postulated that the adsorption of gas
on the particles had increased the amount
of irritant vapor reaching the critical tar-
get areas of the lung. Dautrebande and his
co-workers 39> 40 studied the sensory response
of human subjects to pollutants thought to
be constituents of the Los Angeles smog and
found that the presence of particles of so-
dium chloride, oil mist, or smoke, increase
the irritation of eye, nose, and throat by sul-
fur dioxide, formaldehyde, and other gaseous
pollutants.
LaBelle et al.*1 studied the effect of par-
ticulate matter on the survival time of mice
exposed to formaldehyde, acrolein, and ox-
ides of nitrogen. The particles used included
triethylene glycol, ethylene glycol, mineral
oil, glycerin, sodium chloride, two commer-
cial filter grades of diatomaceous earth, and
a commercial silica gel. From theoretical
considerations, the probable percent penetra-
tion of the upper respiratory tract by vari-
ous gases was calculated. If the gas pene-
trated to a greater extent than the particles,
then adsorption on the particles would de-
crease the amount of irritant gas reaching
the lungs and the toxicity would decrease.
Such a situation exists with oxides of nitro-
gen. Conversely, if the gas did not readily
penetrate the upper respiratory tract, ad-
sorption on small particles would tend to
carry more gas to the lungs and thus in-
crease the toxicity. Such a situation exists
with formaldehyde. The theoretical calcula-
tions coincided with experimental results in
over 70 percent of the gas-particle combina-
tions. The theory partially explains the po-
tentiation of irritant gases by particulate
material (often termed a synergistic effect),
but subsequent research has shown that the
problem is not as simple as had been as-
sumed.
A synergistic effect was reported by Dal-
hamn and Reid42 with ammonia and carbon
particles. Ammonia is a highly soluble gas,
so that synergism would have been predicted
by LaBelle et a/.41 Rats were exposed for
60 days to 100 ppm ammonia alone, 7 mg/m3
carbon alone, and to 119 ppm ammonia plus
3.5 mg/m3 carbon. The carbon particles
were 95 percent smaller than 3 /* and 65
percent smaller than 1 p. In the group ex-
posed to both ammonia and carbon, there was
a high frequency of mucosal damage, and the
ciliary activity seemed to be significantly
impaired. The trachea of rats exposed to
ammonia alone showed less severe damage,
and the trachea was histologically normal in
about 80 percent of the rats exposed to car-
bon alone.
Boren " exposed mice to carbon alone, to
nitrogen dioxide, and to carbon which had
previously been exposed to nitrogen dioxide.
He stated that around 550 mg of nitrogen
dioxide was adsorbed per gram of carbon.
Samples of air taken from the chamber dur-
ing the exposure of mice to carbon with ad-
sorbed nitrogen dioxide indicated that there
was about 25 ppm to 30 ppm free nitrogen
dioxide. Although this is a high concentra-
tion of nitrogen dioxide, mice exposed to even
higher concentrations (250 ppm) of nitro-
gen dioxide alone developed pulmonary ede-
ma, but neither single nor repetitive ex-
posure produced parenchymal lung lesions.
Control mice and mice exposed to carbon
alone showed no anatomic abnormality of
the lungs. Mice exposed to the carbon with
adsorbed nitrogen dioxide developed focal
destructive pulmonary lesions. The expo-
sures in this group were 6 hours per day,
5 days a week, for 3 months.
The typical lesions of pneumonitis were
observed by Gross et al.4t in the lungs of
hamsters, rats, and guinea pigs exposed to
a "sufficiently large number of carbon par-
ticles with either adsorbed sulfur dioxide or
nitrogen dioxide." Exposure was 8 hours
per day, 5 days per week, for 4 weeks. The
particle size of the carbon, and the meaning
of the phrase "a sufficiently large number
of carbon particles" were not given. There
was no record of the amount of either gas
adsorbed by the activated carbon particles.
Histological sections were from animals
killed about a month after the end of ex-
135
-------
posure, whereby it is concluded that the le-
sions were persistent. They were concen-
trated in the regions of the respiratory bron-
chioles and alveolar dusts and consisted of
cellular wall thickening.
Pattle and Burgess 4 studied the effect of
mixtures of sulfur dioxide and smoke on
mice and guinea pigs. Their concentrations
of sulfur dioxide were in the range of 2,700
mg/m3 to 12,000 mg/m3 (900 ppm to 4,000
ppm), and the smoke concentrations were in
the range of 50 mg/m3 to 135 mg/m3. Their
end point was the dosage required to produce
death. With concentrations of this magni-
tude, the results obtained have little appli-
cability to air pollution criteria. Although
they found that the lethality of mixtures of
sulfur dioxide and smoke was greater than
the lethality of the sulfur dioxide alone, they
considered the effect to be a simple additive
one resulting from the action of smoke in
blocking the bronchi and alveoli.
Salem and Cullumbine 5 studied the effect
of kerosene smoke on the acute toxicity of
sulfuric acid, sulfur dioxide, acrolein, and
acetaldehyde in guinea pigs, mice, and rab-
bits. As in the work by Pattle and Burgess,4
the concentrations were many magnitudes
above those found in air pollution episodes.
The administration of smoke prior to the
exposure to the irritant substances did not
alter the toxicity, although the effects of
smoke on the toxicity of the irritants were
highly variable when the two agents were
given simultaneously. In guinea pigs, the
toxicity of sulfuric acid was increased by the
presence of smoke, the toxicity of acetalde-
hyde and sulfur dioxide was decreased, and
the toxicity of acrolein was unchanged. In
mice, the toxicity of sulfur dioxide was in-
creased, while that of acetaldehyde and acro-
lein was decreased. In rabbits, the toxicity
of acrolein and acetaldehyde was decreased
by the smoke. The end point in all cases was
the mean fatal dose.
A series of studies of the effect of hygro-
scopic particles on physiological response to
irritants has been undertaken by Amdur,22-27
using the pulmonary flow resistance tech-
nique. It was found initially that the re-
sponse to sulfur dioxide was potentiated by
particles of sodium chloride below 1 p, but
not by 2.5-/U particles, at concentrations of
about 10 mg/m3. With sulfur dioxide 24 and
with formaldehyde 25 as irritants, decreasing
the concentration of the aerosol, or the total
dose of aerosol by shortening the exposure
time,22 decreased the degree of potentiation
observed from the addition of sodium chlo-
ride. The hypothesis of LaBelle et a£.41 that
irritant gases with high water solubility
would be potentiated by particles did not
explain adequately the data obtained. Sul-
fur dioxide, formaldehyde, acetic acid, and
formic acid all have high water solubility,
but it was found that the first two were po-
tentiated by sodium chloride 23>24 and that
the latter two were not.25-27 Although both
sulfur dioxide and formaldehyde were po-
tentiated by sodium chloride, there are dif-
ferences which suggest that the guiding
mechanism in the case of sulfur dioxide may
be chemical change and for formaldehyde
may involve surface adsorption.24
Another paper - examines further the ef-
fect of various physical and chemical factors
on the potentiation of sulfur dioxide by par-
ticulate material. The degree of potentiation
observed could be correlated to some extent
with the solubility of sulfur dioxide in the
solutions of sodium chloride, potassium chlo-
ride, and ammonium thiocyanate.
Aerosols of soluble salts of ferrous iron,
manganese, and vanadium, which had been
shown by Johnstone and co-workers45-46 to
be capable of catalyzing the conversion of
sulfur dioxide to sulfuric acid when they
were present as nuclei of fog droplets,
showed a major potentiating action where
present at concentrations of about 1 mg/m3.
On the other hand, dry manganese dioxide,
activated or spectrographic carbon, iron ox-
ide fume, open hearth dust, and triphenyl
phosphate did not alter the response even
when present in concentrations of 8 mg/m3
to 10 mg/m3.
It is clear from the data presented 22 that
all particulate material does not potentiate
the response to sulfur dioxide any more than
one particulate (sodium chloride) has po-
tentiated the response to all irritant gases
tested. Both solubility of sulfur dioxide in
a droplet and catalytic oxidation to sulfuric
acid play a major role in the observed poten-
136
-------
tiation of sulfur dioxide by certain particu-
late matter.
D. CARCINOGENESIS
1. Carcinogens
The incidence of cancer, and the insidious
nature of the onset of malignant cell activity,
together make essential the utmost effort in
determining whether factors associated with
air pollution can lead to increased occurrence
of lung cancer in susceptible individuals, or
to increased susceptibility to cancer in the
population at large. In various parts of the
world, and especially in the United States,
the relative mortality due to lung cancer has
been increasing.47 Furthermore, urban resi-
dents exhibit a greater liability to the de-
velopment of lung cancer than do those liv-
ing in rural areas,48 and data from several
investigations suggest that the epidemiologi-
cal association between urban residence and
lung cancer is of pathogenetic signifi-
cance.49"51 The association between lung can-
cer and cigarette smoking is too well docu-
mented to need further amplification here.
There is, however, one feature common to
both air pollution and cigarette smoking
studies which should be emphasized. In no
case, for the reasons explained in the intro-
duction to this chapter, has a suspected car-
cinogen in fact been demonstrated experi-
mentally to produce a lung tumor in man,
although the epidemiological considerations
to be developed in the next chapter may well
show a significant association between the
suspected material and cancer. Thus, sub-
stances such as the polynuclear aromatic hy-
drocarbons (of which benzo(a)pyrene, BaP,
is the prime example) may or may not pro-
duce lung cancer in man. However, they
do increase tumor incidence in laboratory
animals and, in addition, have produced ma-
lignancies when in combination with spe-
cific particles or viral infection. The mini-
mum possible risk should always be taken
with a potentially toxic substance whose ef-
fect may appear after a long period of la-
tency. The bulk of the ensuing discussion is
therefore based on the hypothesis that carci-
nogens effective in animals may be signifi-
cant in increasing human malignant tumor
incidence, and the word "carcinogen" will
be used without qualification.
A portion of the organic material present
in the atmosphere as suspended particles
(Table 1-2) may be carcinogenic, and carci-
nogenic materials have been identified in the
atmosphere of virtually all large cities in
which studies have been conducted. The in-
complete combustion of organic matter is one
of the major sources of such substances; the
photochemical reaction products of aliphatic
and aromatic constituents of gasoline in the
presence of the atmospheric gases also pos-
sess some potency for generating tumors ex-
perimentally.
Chemical and physical studies of polluted
urban air have been paralleled by carcino-
genic investigations using skin painting, sub-
cutaneous injection, and inhalation tech-
niques. The carcinogenicity (as measured
by these techniques) of extracts of mate-
rials collected from air as well as such pol-
lutant sources as chimney soots, road dusts,
and vehicular exhausts, has been established
by many investigators. It should be noted
first that, in many cases, use was made of
mice (A-strain) particularly susceptible to
tumor development; and second, only two of
the studies, those involving ozonized gaso-
line, used inhalation as a route o'f adminis-
tration. The observed response in the case
of A-strain mice inhaling ozonized gasoline
was the relatively rapid development of mul-
tiple adenomas in the lung which, although
tumors, are not malignant.52
More recently, sequamous cell cancers of
the lung were induced in C57 black mice fol-
lowing infection with influenza virus and
continuous exposure to an aerosol of ozon-
ized gasoline. The tumors produced were
histologically identical with those observed
most frequently in man.53
Measurable concentrations of inorganic
substances, such as metal dusts and asbestos,
demonstrated to be occupationally associated
with increased liability to lung cancer de-
velopment, are also emitted into the atmo-
sphere.54"60 Additional laboratory experi-
mentation is needed to verify such carcino-
genic potential relative to interacting effects
and respective ambient atmospheric concen-
trations.
137
-------
2. Polynuclear Aromatic Hydrocarbons as
Carcinogens in Polluted Atmospheres
Polynuclear aromatic hydrocarbons are
commonly regarded with extreme suspicion
as possible carcinogens, and much of the
experimental work performed has concerned
these compounds. This section deals with
the presence and stability of the hydrocar-
bons in the atmosphere, and with their elu-
tion from soots on which they may be ad-
sorbed.
The concentration of benzo(a)pyrene
(BaP) as a representative carcinogenic hy-
drocarbon in selected urban and nonurban
areas within the United States is shown in
Table 10-2;61 in Table 10-3,62 the benzo(a)-
pyrene content is given as a fraction of the
Table 10-2. — BENZO(A)PYRENE CONCENTRA-
TIONS IN SEVERAL URBAN AND NONURBAN
AREAS.
State
BaP/lOOOm3 air
Urban
Nonurban
Alabama
Indiana
Maryland
Missouri
North Carolina
Oregon
Pennsylvania
South Carolina
24
39
14
54
39
8
61
24
0.076
1.8
0.70
0.025
0.25
0.01
1.9
1.1
Table 10-3.— BENZO(A)PYRENE AS A FRACTION
OF THE TOTAL AROMATIC HYDROCARBON
CONTENT OF SEVERAL URBAN ATMOS-
PHERES
City
BaP fraction of
total aromatic hydrocarbon,
Lot 19
Lot 20
Atlanta
Birmingham
Cincinnati
Detroit
Los Angeles
Nashville
New Orleans
Philadelphia
San Francisco
1,800
2,300
2,800
3,800
660
5,900
2,100
2,500
680
1,900
3,400
5,200
4,500
260
4,900
1,600
?
290
total aromatic hydrocarbon content of air
pollutants of nine American cities.
The physical stability of aerosols in pol-
luted atmospheres has already been described
in general terms (Chapter 1). Chemically,
benzo(a)pyrene seems to be relatively stable
and, even in the presence of a strongly oxi-
dizing atmosphere, such as that found in
photochemical smog characteristic of Los
Angeles, the rate of disappearance of ben-
zo(a)pyrene is smaller than that of many
other hydrocarbons. Table 10-4 63 shows the
destruction under certain conditions of ex-
posure of various polynuclear aromatic hy-
drocarbons present in air.
Polynuclear aromatic hydrocarbons may
exist in the atmosphere adsorbed on carrier
particles as well as in their free state. As
was mentioned in Section C-2, in the respira-
tory system, particle size influences the rate
and extent of elution of adsorbates either
into the macrophages, or onto the respira-
tory epithelium. Polycyclic aromatic hydro-
carbons cannot be readily eluted from soots
of very small particle size; in fact, particles
with an average diameter of less than 0.04 /*
will remove these compounds from their im-
mediate environment because of high sur-
face adsorption. Particles above 0.04-ju, aver-
age size range will generally release adsorbed
aromatic polycyclic hydrocarbons in the
presence of appropriate solvents, which in-
clude plasma and cytoplasmic proteins. As
particle size increases, release becomes more
rapid and greater in extent. The elution of
polycyclic aromatic hydrocarbons from 0.5-//,
soot particles after incubation with plasma
for various time intervals is shown in Table
10-5.64
In studies on skin carcinogenesis, Falk
and Steiner,65 using commercial carbon
blacks, related the biological activity of ad-
sorbed carcinogens to the size of the soot
particle and the presence of natural eluting
substances at the site of deposition. They
advanced the principles of natural and con-
ditional carcinogens, of solvent elution, and
of adsorption, to explain some clinical and
epidemiological observations of human skin
and lung cancers, and of the role of preced-
ing pathological lesions in predisposing to
pulmonary tumors.
138
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Table 10-4.—EFFECT OF VARIOUS CONDITIONS OF EXPOSURE ON THE DESTRUCTION OF SOME
POLYNUCLEAR AROMATIC HYDROCARBONS
Percent destroyed
Pure unadsorbed
Adsorbed on soot
Hydrocarbons
Compound X
Anthanthrene
Phenanthrene
Pyrene
Fluoranthene .
3, 4 Benzpyrene
1, 2 Benzpyrene .
1, 12 Benzperylene
Coronene
Chrysene
By
air
in dark
24
100
.. 44
39
24
17
0
0
0
0
48
49
61
43
20
0
0
0
0
By air
in
24
100
42
34
20
16
21
0
0
11
light
48
44
60
42
24
22
0
0
0
By smog
in light
Hours
1
100
83
59
50
27
5
15
By air
in light
48
12
5
1
4
10
7
0
By smog
1
72
55
58
59
18
51
67
The interaction of carcinogens with other
particulate agents has been studied toxico-
logically, utilizing laboratory animals. Ex-
periments have shown that the addition of
seemingly inert particulates to carcinogens
results in the production of malignant neo-
plasms in the lung. Pylev66 produced an
appreciable incidence of lung cancers in rats
by the intratracheal administration of 9,
10-dimethyl-l, 2 benzathracene (DMBA) in-
corporated with india ink in a 4-percent
casein solution, whereas Gricute67 was un-
successful with the same material when it
was suspended only in physiological saline.
Saffiotti6S'69 has produced a variety of ma-
lignant tumors in the lungs of hamsters by
intratracheal instillation of saline suspen-
sions of BaP ground together with hematite
(Fe^Os) as a carrier dust in amounts equiv-
alent to 3 mg of each chemical, once weekly
for 15 injections. Not only was a high in-
cidence of lung cancers produced but also
these lung cancers mimicked all the various
cell types seen in human cancers, i.e., squa-
mous cell carcinoma, anaplastic carcinoma,
adeno-carcinoma, and even tracheal cancers.
Dose-response effects were suggested, as
were indications that a single high dose
could induce cancers in this system.69 Ac-
cording to Saffiotti et al.''0 the increased ac-
tion for the carcinogen is thought to be
brought about by its adherence to the fine
inert particulate which in turn carries it
through the respiratory bronchioles and
alveoli into the lung parenchyma. The carci-
nogens may then be eluted from the particu-
lates and spread diffusely to reach the target
tissue. They infer that there is also a re-
duction in the speed in which BaP is re-
moved from the respiratory tract brought
about by the hermatite dust. Shabad et al.71
have reported that when india ink was in-
cluded in the inoculum, BaP was eliminated
more slowly from the lung. One must con-
sider the possibility that the carrier material
itself might be contributing some effect.
Faulds and Stewart72 reported increased in-
cidence of carcinoma in the lungs of hema-
tite miners. However, it is difficult to assess
the exact role of iron in such a complicated
exposure situation, since silica and other
dusts are certain to be present. Bonser
'.it al.73 suggest that iron oxide may play a
role in converting the fibrogenic effect of
silica into a carcinogenic process. Haddow
and Horning 74 have reported that the car-
139
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Table 10-5.—PERCENTAGE RECOVERY OF POLYNUCLEAR AROMATIC HYDROCARBONS FROM 05M
SOOT PARTICLES AND FROM PLASMA AFTER INCUBATION WITH PLASMA FOR VARYING
PERIODS.
Incubation time, hours
Compound
Pyrene
Fluoranthrene
C ompound-X
1 ,2-i . nzpyrene
3 , 4-Benzpyrene
1 ,12-Benzperylene
Anthanthre'ne
Coronene - -
Concentration, Fraction
8 4 Soot
Plasma
Total
1 . 0 Soot
Plasma
Total
2 8 Soot
Plasma
Total
2 . 9 Soot
Plasma
Total
1 . 7 Soot
Plasma
Total
9.2 Soot
Plasma
Total
2.4 Soot
Plasma
Total
10.0 Soot
Plasma
Total
1.5
9
81
90
trace
100
100
0
100
100
trace
52
52
18
82
100
31
66
97
25
54
79
40
36
76
16
Percentage
34
61
95
present
present
trace
93
93
17
41
58
41
59
100
67
33
100
54
33
87
66
26
92
96
recovery
9
50
59
0
present
0
present
0
21
21
6
23
29
5
15
20
trace
17
17
12
8
20
192
6
61
67
present
present
0
39
39
0
21
21
18
18
36
11
13
24
13
13
20
15
10
25
cinogenic action of an iron-dextran complex
cannot be entirely explained by the dextran
content alone. Consequently, iron cannot be
excluded as a possible contributing factor
or cofactor in cancer production. Epstein
et aV5 have recently applied methods em-
ploying the injection of crude benzene-solu-
ble extracts of atmospheric particulate into
suckling mice. The total dosages adminis-
tered ranged from 5 to 55 mg and produced
a high incidence of tumors in surviving mice
as compared to controls. At 50 weeks post-
inoculation, a variety of tumors was evi-
dent, the most significant being lymphomas,
hepatomas, and multiple pulmonary adeno-
mas. In mature mice injected subcutaneous-
ly with carcinogens, the tumors usually de-
velop in the vicinity of the site of inocula-
tion. However, in newborn mice, the tumors
frequently develop at distal points such as
the liver, lungs, or lymph nodes.
More recently, Kuschner76 has demon-
strated the interaction of a known carcino-
gen with the gaseous air pollutant, S02. In-
halation exposures of rats indicated that S02,
alone, produced proliferative and metaplastic
changes in the bronchial epithelium; benzo-
(a)pyrene, alone, failed to cause the develop-
ment of tumors, but the inhalation of benzo-
(a)pyrene in the presence of S02 caused the
140
-------
development of bronchogenic squamous cell
carcinoma.
3. Pathology of Carcinogenesis
Rather little experimental evidence is
available on the pathology of carcinogenesis
following exposure to air pollutants; much
more experimentation has been carried out
in relation to smoking and lung- cancer. The
results of the extensive work on the latter
topic by Auerbach et al.'11 are reported briefly
because of the possible similarities between
carcinogenic mechanisms in cigarette smok-
ing and air pollution. The authors describe
a series of changes which are characterized
by loss of cilia, increase in the number of
cell rows, and the presence of atypical cells
in the thickened epithelium. Their findings
suggest a progression of changes from ini-
tial goblet cell hyperplasia to metaplasia,
metaplasia with atypism, carcinoma in situ,
and invasive cancer. Their data further sup-
port the epidemiologic observation of a dose
response to cigarette smoke. Carnes 78 also
observed a clear and pronounced association
between the extent of epithelial change and
exposure to pollutants, and emphasized the
similarity of epithelial changes in man to
"hyperplasia and other changes in the bron-
chial epithelium of mice." Indistinguishable
histologic counterparts can be identified in
both man and experimental animals.
The sequence of hyperplasia, metaplasia,
metaplasia with atypical change, cancer in
situ, and invasive cancer is likely to occur
first at sites of impingement and particulate
retention. In experiments with animals, par-
ticle deposition and retention occur most
readily in the more distal segments of the
tracheobronchial tree, a result which ap-
peared at first to be incompatible with early
clinical and pathologic observations that pri-
mary bronchial carcinomas originated chiefly
in the main stem bronchi. Early clinical ob-
servations, however, included a majority of
cases in which tumor size was great and
point of origin was difficult to ascertain, and
recent reports question the concept that most
primary lung cancers are hilar or central in
origin. For example, Table 10-6 shows the
distribution of lung cancer by sites of origin
given by Kotin.79
Table 10-6.—DISTRIBUTION OF LUNG CANCER
BY SITE OF ORIGIN
Percentage
Site of origin of
incidence
Main bronchus (including intermediate) 11
Lobar bronchus 29
Segmental bronchus 29
Segmental area (i.e., peripheral tumor) 31
E. SUMMARY
This chapter reviews toxicological studies
of various types of particulate matter known
to be present in ambient atmospheres. These
studies are primarily concerned with the
disciplinary areas of pathology, physiology,
and carcinogenesis. In addition, the mecha-
nisms of the toxicological action of particu-
late matter are discussed and considerations
concerning mixtures of irritant gases and
particulate matter are given proper empha-
sis. To date, studies utilizing laboratory ani-
mals have, in the main, been concerned with
levels of particulate materials far in excess
of ambient concentrations. Although direct
extrapolations from the laboratory animal
to man are impossible, animal experimenta-
tion is useful and necessary for rapidly de-
fining the toxicological mechanisms of ac-
tion and for pinpointing the primary bio-
logical systems affected by a specific particu-
late material alone or in the presence of an
irritant gas. Findings obtained from animal
experimentation can be tested under com-
munity conditions with human populations
via epidemiological studies.
Particulate matter may exert a toxic effect
via one or more of three mechanisms:
1. The particle may be intrinsically
toxic due to its inherent chemical
and/or physical characteristics;
2. The particle may interfere with one
or more of the clearance mechanisms
in the respiratory tract;
3. The particle may act as a carrier of
an adsorbed toxic substance.
The last of these mechanisms can lead to a
"potentiating" effect in which particles con-
taining an adsorbed toxic substance increase
the physiological response to the adsorbed
141
-------
substance to a level above that which one
would expect if the substance were present
in the absence of the particle. Conversely,
prior exposure of an animal to particulate
matter can sometimes afford a degree of pro-
tection to subsequent exposure to irritant
gases. Particle size and dust load both con-
tribute toward determining the toxicity of
any specific chemical substances: reduction
in particle size generally increases toxicity,
while even an "inert" particle may elicit
toxic responses when present in high enough
concentrations. Finally, it has been clearly
demonstrated that a number of substances
(metal dusts, asbestos, polynuclear aromatic
hydrocarbons, etc.) known to be carcinogenic
in animals are present in polluted atmos-
pheres. When linked with urban-rural dif-
ferences in lung cancer frequency revealed
from epidemiologic investigations, this evi-
dence indicates that such substances in urban
polluted atmospheres may be potential car-
cinogens for the exposed human population.
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Chapter 11
EPIDEMIOLOGICAL APPRAISAL OF
PARTICIPATE MATTER
-------
Table of Contents
Page
A. INTRODUCTION 148
B. APPLICATION OF EPIDEMIOLOGY TO AIR POLLUTION . 148
1. Indices 148
2. Cautions . . . .... 148
C. INDICES OF HUMAN RESPONSE: THE EPIDEMIOLOGIC
STUDIES 150
1. Acute Episodes . . 150
a. Mortality . . 150
b. Morbidity . 154
2. Chronic (Long-Term) Air Pollution 156
a. Day-to-Day Variations in Mortality and Morbidity 156
b. Geographical Variation in Mortality . . 156
1. Studies Based on Available Data 156
2. Special Studies Involving the Collection of New Data ... 158
c. Geographic Variations in Morbidity—Special Studies . 161
d. Morbidity—Incapacity for Work 164
3. Studies of Children . . . .165
4. Studies of Pulmonary Function . ... 167
5. Studies of Panels of Bronchitic Patients . ... 168
D. SUMMARY . 169
E. REFERENCES 176
List of Figures
Figure
11-1 Mortality Figures for the January 1956 and December 1957 Smog
"Episodes" in London . ...... 151
11-2 Mortality and Air Pollution in Greater London during the Winter of
1958-1959 152
11-3 Death Rates and Air Pollution Levels in Dublin, Ireland, for 1938-
1949 . 155
11-4 Average Annual Death Rate from all Causes . . 160
11-5 Average Annual Death Rate from Asthma, Bronchitis, or Emphy-
sema Indicated on the Death Certificate . . . 160
11-6 Average Annual Death Rate from Gastric Cancer . 161
11-7 Age-Standardized Morbidity Rate per 1,000 for Three Diseases in
Japan .. 162
11-8 Effect on Bronchitic Patients of High Pollution Levels (January
1954) 169
146
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List of Tables
Table Page
11-1 Pollution Levels in Salford (seasonal daily averages) 159
11-2 Average Annual Death Rates Per 1,000 Population From All Causes
According to Economic and Particluate Levels, and Age: White
Males 50-69 Years of Age, Buffalo and Environs, 1959-1961 . . 159
11-3 Average Annual Death Rates Per 100,000 Population from Chronic
Respiratory Disease According to Economic and Particulate Levels,
and Age: White Males 50-69 Years, Buffalo and Environs, 1959-
1961 . . .160
11-4 Average Annual Death Rates Per 100,000 Population for Gastric
Cancer According to Economic and Particulate Levels: White Males
50-69 Years of Age, Buffalo and Environs, 1959-1961 . . 161
11-5 Response of Telephone Workers in the U.K. and the U.S.A. to Air
Pollution 163
11-6 Summary Table of Epidemiological Studies 171
147
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Chapter 11
EPIDEMIOLOGICAL APPRAISAL OF PARTICIPATE MATTER
A. INTRODUCTION
Health effects produced by atmospheric
particulate matter are discussed in this chap-
ter in terms of epidemiologic studies. Be-
cause particulate matter tends to occur in
the same kinds of polluted atmosphere as
sulfur oxides, few epidemiologic studies have
been able adequately to differentiate the ef-
fects of two pollutants. It follows, therefore,
that the studies presented in this chapter are
frequently identical with those described in
the companion document, Air Quality Cri-
teria for Sulfur Oxides.
Epidemiologic studies, as distinguished
from toxicologic or experimental studies,
analyze the effects of pollution from ambi-
ent exposure on groups of people living in
a community. Such studies have the advan-
tage of examining illness where it occurs
naturally, rather than in a laboratory, but
carry the disadvantage of not being able to
control precisely all the factors of possible
importance. Nevertheless, the preparation
of air quality criteria must rest on epidemio-
logic studies because of the very severe limi-
tations of toxicologic and industrial studies
for this purpose. Other countries, notably
the Netherlands and Sweden, have based
their air quality criteria solely on epidemio-
logic studies.
In determining whether or not an asso-
ciation is causal, consideration must be given
to several aspects of association which in-
clude strength, consistency, specificity, tem-
porality, biological gradient, plausibility, co-
herence, and analogy.1 A judgment of the
value of an epidemiologic study requires an
understanding of these aspects. Many types
of epidemiologic evidence suggest that air
pollution may exert considerable influence on
health, as well as on the "satisfaction with
life," of major segments of the world popu-
lation.
Several health indices are described in
Section B-l; certain precautions which
should be observed in the application of epi-
demiologic methods to air quality criteria
are suggested in Section B-2. The studies
themselves are listed in Section C, accord-
ing to the index employed.
B. APPLICATION OF EPIDEMIOLOGY
TO AIR POLLUTION STUDIES
1. Indices
Various indices of health may be used for
correlation with air pollution by the oxides
of sulfur. Among the possible indices are:
1. mortality (greater than expected)
(i) deaths from all causes
(ii) deaths from specific causes
(iii) deaths among the different age
and sex groups
2. morbidity
(i) incidence of disease—chronic
bronchitis, pulmonary emphy-
sema, diffuse interstitial pneu-
monitis, cancer of respiratory
tract, disease of remote organ
(e.g., gastrointestinal, ophthal-
mic, and cardiovascular sys-
tems)
(ii) prevalence of diseases—same
examples as for "incidence"
(iii) prevalence of respiratory symp-
toms (e.g., changes in quality
and/or quantity of sputum
production)
(iv) exacerbation of diseases—rhi-
norrhea, asthma, tracheobron-
chitis, and chronic illness, and
148
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enhancement of infection: pne-
umonia, sinusitis, otitis, mas-
toiditis
(v) changes in clinical conditions
(e.g., bronchitic patients)
3. changes in various aspects of lung
function
(i) ventilatory function—decrease
in peak flow rate, decrease in
spirometric volumes, impair-
ment of flow-volume relation-
ship, and increased airway re-
sistance
(ii) blood/gas distribution—impair-
ment of lung-gas distribution
(iii) blood/gas exchange—impair-
ment of pulmonary blood-gas
exchange
(iv) increased work of breathing
Definitions of the various disease states are
to be found in the glossary; most of the pul-
monary function methods have been men-
tioned in Chapters 9 and 10.
The manner of presentation of the state of
epidemiological knowledge of effects of par-
ticulate matter in the ambient atmosphere
when accompanied by the oxides of sulfur is
outlined in the Table of Contents.
2. Cautions
In the first place, as discussed in Chapter
1, methods of measurement vary from coun-
try to country and place to place. Results
from the high volume sampler and the results
from smoke stain calibration are very dis-
similar. Also, coh values cannot be compared
with ju,g/m3.
Secondly, particle size plays an important
part in the appropriateness of the measuring
technique as it does in determining the site
and effectiveness of deposition in the respira-
tory tract. (See Chapter 9.) However, size
distribution of particles has nearly always
been ignored in field studies.
Thirdly, pollution and health indices are
not always measured over the same time
periods. It is to be hoped that the pollution
levels cited bear some relation to those extant
during the time when the chronic disease
states were developing. Further, acute effects
require frequent short-term pollution meas-
urements to enhance detection, while long-
term chronic processes may be adequately
related to long-term sampling intervals. Air
pollution measurements useful in studies of
acute health effects are becoming available;
a less satisfactory situation exists for the
long-term effects studied.
In many instances the possible role of cig-
arette smoking has not been considered. It is
expected that future epidemiologic studies
involving adults will routinely collect data on
smoking habits of the study group. Other
factors are significantly related to respira-
tory disease. These include occupational and
other past exposures; infections, past and
present; and allergy and heredity.
Few or no epidemiologic studies have been
possible where the pollution challenge has
been limited to particulate matter, unaccom-
panied by significant amounts of other pol-
lutant substances. Indeed, most of the availa-
ble conclusions link particulate levels with
those of concurrently measured sulfur di-
oxide; some studies attempt statistical sep-
aration of the culpability of one factor from
the other in the effects cited.
In seeking the possible effects on popula-
tions resident in areas of differing air pollu-
tion, factors such as smoking, type and condi-
tions of employment' ethnic group, and mobil-
ity in response to experienced irritation or
disease have sometimes been considered.
There has, however, been a minimum of at-
tention paid to the indoor or domestic envi-
ronments and their potential contribution.
Measurement of such indoor exposures might
be difficult, but omission of the information
could well modify the appraisal of the im-
portance of particulate pollution.
Toxicologic studies indicate a specific po-
tential of some particulate materials to pro-
duce human responses. The levels used in
toxicologic studies are far higher than those
found in the communities in the epidemio-
logic studies under review. Thus the actual
responsibility of "particulate matter" for
the community responses is uncertain, and
it is sometimes necessary to invoke addition-
al concepts; for example, the idea of syn-
ergism with other known or unkown ambient
pollutants, or the idea that particulate matter
is but an index of availability of some other
149
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substance (s) which are fully responsible for
the effects reported.
Over a short period of time, mortality
fluctuates considerably, and only a syste-
matic, long-term approach will allow a valid
determination of the real role of air pollution.
Cassell et al.2 have reviewed the problem of
detecting peaks in mortality and relating
them to any single variable. The danger with
episodic studies is that short-term fluctuation
in the death rate, when picked to coincide
with an air pollution incident, may appear
to be causally related; in the long term, how-
ever, numerous other unassociated peaks are
found in both the death rates and the air pol-
lution levels.
Specific substances encountered as respira-
ble particles, and associated with disease en-
tities (beryllium, asbestos, arsenic, vanadi-
um, lead, airborne pathogens, etc.) are not
assessed in this report. They deserve consid-
eration, however, as exemplars of the modes
of response of which the human is capable,
and which may delay or confound the recog-
nition of the importance of "particulate mat-
ter" inhalation. The demonstration of the
importance of aerodynamic behavior rather
than of mass or particle dimension for both
impingement and retention of asbestos is
striking. Long-delayed effects from relatively
brief community dispersion exposures to as-
bestos and beryllium are significant (see
Chapter 10). Furthermore, penetration of
"poorly cleared" particles of asbestos to re-
mote body sites suggests complex body trans-
port mechanisms, differing organ or tissue
sensitivities, and the need for evaluation of
as yet untested relationships between disease
entities and respirable offenders. These mod-
els confer some sense of urgency to establish-
ing the relationships of human disease and
dysfunction to air pollution by "general par-
ticulate matter."
The concept of "susceptible population"
demands consideration. Human responses to
toxicants, and to community air pollution,
show wide variations, which contribute in no
small way to the difficulty in assessing in a
general manner the effects of pollutants.
Since air quality criteria must, unless other-
wise specified, consider "all" population rath-
er than just major segments of it, studies
must consider especially the impact of air
pollution on the "most sensitive" responders.
Many factors seem to enhance susceptibility
or sensitivity to air pollution. These include
being at the extremes of age (i.e., infants and
the very old); having pre-existing chronic
respiratory disease (e.g., pulmonary emphy-
sema or chronic bronchitis); having pre-
existing cardiovascular disease (functional
capacity not defined); regularly smoking cig-
arettes; or living in overcrowded or depressed
socioeconomic strata. Some of these factors
have been singled out for attention in the
references to be cited, and the level of pol-
lutant said to have an "effect" may take cog-
nizance of such special sensitivity.
The effects discussed are related insofar as
possible to specific pollution over specific time
intervals; it must be emphasized that lower
values by no means imply a "no effect" level
of the pollutants.
C. INDICES OF HUMAN RESPONSE:
THE EPIDEMIOLOGIC STUDIES
1. Acute Episodes
a. Mortality
In conurbations, such as London, New
York, Chicago, and Detroit, it has been pos-
sible to observe deviations from the moving
averages of deaths during various seasons,
and to relate such deviations to the coincident
period levels of air pollutants.3
In writing about the Meuse Valley episode
in 1936, Firket stated that if there were a
similar phenomenon in London, some 3,200
death might occur.*-5 Unfortunately, he was
quite accurate in his estimate since, in Decem-
ber 1952, the world's most disastrous smog
incident occurred in London, causing about
4,000 excess deaths throughout the Greater
London area. Marked increases were noted
in both respiratory and cardiovascular deaths
(and for almost every cause except traffic
accidents; presumably the smog was too thick
for people to drive). Since some of the diseas-
es such as lung cancer and tuberculosis were
obviously existent before the pollution ep-
isode, much of the effect of the fog was clear-
ly to hasten the death of people who were
already ill. Detailed investigations were made
of 1,280 post-mortem reports of persons who
150
-------
had died before, during, or shortly after the
episode. No fatalities were found which could
not have been explained by previous respira-
tory or cardiovascular lesions. In this episode
as in others, the elderly and persons with pre-
existing pulmonary and cardiac disease were
most susceptible.
A number of investigations have analyzed
and compared the various London episodes.
The report by Brasser et al.6 appears to cover
all the episodes and to present a detailed
analysis of each of these episodes, pointing
out the importance of the duration of the
maximum values. More recently, Joosting7
has examined the relationship between the
duration of maximum values of sulfur dioxide
and smoke during air pollution episodes, as
well as the differential relationship between
sulfur dioxide and smoke levels and the re-
sulting mortality.
Gore and Shaddick8 and Burgess and
Shaddick9 reviewed acute "fog" episodes
which occurred in London in 1954,1955,1956
(January and Decmeber), and 1957 (Decem-
ber), in terms of excess mortality above a
moving average, related to the mean of daily
readings at seven stations for smoke and S02.
Figure 11-1 shows mortality figures for the
January 1956 and December 1957 episodes.
Somewhat differing patterns of onset of
mortality rise, of age of population suffering
most heavily, of deaths related to bronchitis
and to other respiratory diseases, and of total
deaths, were noted in these acute episodes.
JANUARY, 1956
DECEMBER. 1957
200r
ALLAGES
70+YEARS
0-69 YEARS
31 5 10 15 20 25
25 30 5 10 15
DEC. JAN.
NOV. DEC.
FIGURE 11-1. Mortality Figures for the January 1956 and December 1957 Smog "Episodes" in London.0 (The
figure shows the increase in numbers of deaths during smog "episodes" (shaded periods), especially in the
older age group.)
151
347-335 P.O. 3 69-461 REV. REPRO
-------
Common to them, however, were elevations
in the mean daily levels of S02 and smoke,
measured at seven different stations, from
two to four times the winter average levels;
"effects" were estimated at 2,000 /ig/m3 black
suspended matter together with 0.4 ppm
(1,145 Atg/m3) S02 (representing all acidic
gases). Deaths ascribed to bronchitis were
materially affected, but deaths due to other
causes also increased. Deaths appeared to
begin to increase before the onset of the ep-
isodes; during the episodes, of course, they
increased substantially. Scott10 observed a
similar relationship, for similar periods of
"fog," with "effective pollutant" levels at
seven different stations in London of 2,000
/ug/m3 for smoke and 0.4 ppm for S02. There
was a sharp impact on the elderly and the
greatest proportionate rise, for cause of
death, in bronchitics.
Martin and Bradleyll correlated daily
mortality (all causes) and daily bronchitis
mortality with mean daily black suspended
matter (see Figure 11-2) measured at seven
locations in London for the winter of 1958-
1959, and also found a significant positive as-
t-
tr
O
z in
— LU
i!
|3
LU <
O
80
60
40
20-
-20 -
-40
-60
-80
•v-:. s
• •. -
••
•!•* •
••• •
*.«*/
CORRELATION COEFFICIENT r = 0.613
i I I I I I
1.0 1.2
1.4
1.6 1.8
2.0
2.2 2.4
sociation between mean daily sufur dioxide
levels and deaths (all causes). Bronchitis
deaths showed a lower correlation with the
pollution level, and the authors suggest the
need for consideration of effects of air pol-
lution on patients with cardiovascular di-
sease. In addition, excess deaths have been
related to increases (on the day preceding
death) of mean daily black suspended matter
by more than 200 jug/m3, and rises in mean
daily S02 of more than about 75 /ag/m3 (2.5
pphm). In a later paper,12 data are shown to
suggest an increase in mortality from all
causes, and of respiratory and cardiac mor-
bidity, associated with levels of smoke about
1,000 /ttg/m3, and S02 concentrations of 715
^g/m3 (25 pphm). This "effect" is properly
related to abrupt rises in the concentration of
smoke and/or S02, with perhaps a continuum
of effects at lower levels. Since these meas-
urements were obtained at a single point in
Central London, it should be presumed that a
relatively wide range of values around these
levels actually contributed to the mortality
statistics which were correlated. A reanalysis
by Lawther13 of these mortality studies
20
10-
tc
O
HI
Q
-20-
•••
CORRELATION COEFFICIENT r = 0.411
1.0 1.2 1.4
1.6
1.8 2.0 2.2 2.4
OF BLACK SUSPENDED MATTER CONCENTRATION)
FIGURE 11-2. Mortality and Air Pollution in Greater London during the Winter of 1958-1959." (The figure
shows increased mortality due to "all causes" and to bronchitis during a period of high pollution.)
152
-------
places the mortality "effect" at about 750 jug/
m3 for smoke and about 715 jug/m3 (0.25
ppm) for S02. Joosting states that the maxi-
mum sulfur dioxide concentration above
which significant correlation occurs with
death and disease is 400 /*g/m3 to 500 //g/m3
(0.15 ppm to 0.19 pppm)* when there is a
high soot content.
The Dutch report on sulfur dioxide,6 which
discusses in detail seven air pollution episodes
in London, states that in the December 1956
episode, 400 excess deaths, or 25 percent
above expected, were observed in Greater
London at maximum 24-hour levels of 1,200
(Ug/m3 for smoke and 1,100 /tg/m3 (0.41
ppm) * for S02. The report also notes that in
January 1959, 200 excess deaths were observ-
ed in Greater London, or 10 percent above
expected mortality, at a level of 1,200
/j.g/m3 for smoke and 800 /xg/m3 (0.30 ppm) *
for S02. The episodes all took place during
winter; cold weather seems to have been an
important feature of London air pollution
mortality.
In Martin's review 12 in 1964 of daily mor-
tality in London during the winters of 1958-
1959 and 1959-1960, he concluded: "From
the data it would be difficult to fix any thresh-
old value below which levels of air pollution
might be regarded as safe." However, his
review included data with smoke concentra-
tions ranging upward from 500 yug/m3 and ac-
companied by sulfur dioxide concentrations
of about 400 /*g/m3 (0.14 ppm) and above.
As a result of smoke control regulations,
the particle content of London air has steadi-
ly decreased since the 1950's, but the sulfur
dioxide concentrations have not decreased
proportionately. At the same measuring sites
as in 1952, sulfur dioxide was actually slight-
ly higher in the 1962 episode than in that of
1952, but smoke levels were considerably
lower. Also, as Brasser et a/.6 have noted
there was only one day of maximum pollution
values in 1962 as contrasted with the 2 days
of maximum pollution in December 1952.
Although the smoke levels appear to be bet-
*SO2 is converted from ppm to /ig/m* in the Dutch
report by using the equivalency 2,700 llg/TK'=\ ppm;
Scott apparently used 2,850 jug/m8=l ppm; this re-
port uses 2,860 /ltg/ms= 1 ppm.
ter related to the amount of excess mortality,
other factors must be considered as possibly
also reducing the number of deaths. Since
1952, a great deal of publicity has been given
to the harmful effects of smog, and more sus-
ceptible individuals have been encouraged to
use masks and filters and stay indoors. In
addition, when episodes come close together,
a large number of susceptible individuals
might not accumulate, since some are killed
off each time. An effect as large as that seen
in the first incident would not, therefore, be
expected.
The number of deaths in New York City
was reviewed for excess mortality in rela-
tion to the air pollution episode of November
1953, by Greenburg et al.u Excess deaths
were related to elevations of concentrations
of sulfur dioxide and suspended particles.
Average daily suspended particulate matter
measured in Central Park was in excess of
5.0 coh units, while the S02 rose from the
New York City average ranges of 430 /*g/m3
to 570 jug/m3 (0.15 ppm to 0.20 ppm) to a
maximum level of 2,460 /ig/m3 (0.86 ppm).
For this episode, there was a "lag effect,"
and distribution of excess deaths among all
age groups was noted. The number of deaths,
although not showing the marked rise seen
in some of the London episodes, was above
average for comparable periods in other
years during and immediately after the in-
cident. For the November 15 to 24, 1953,
period, the average number of deaths per
day was 244, whereas during the three years
preceding and following 1953, the average
was 224 deaths per day for the same calen-
dar period.
A later episode (1962) was studied,15 But
Greenburg et al. did not discern an excess
mortality. However, McCarroll and Brad-
ley,16 reviewing episodes in New York City
in November and December of 1962, January
and February of 1963, and February and
March of 1964, compared 24-hour average
levels of various pollutants with New York
City mortality figures, employing daily de-
viations from a 15-day moving average; the
measurements were performed at a single
station in lower Manhattan and fluctuations
in the values at this station were known to
correlate well with those at another station
153
-------
6.5 miles away. Excess deaths on December
1, 1962, followed a daily average S02 concen-
tration of 2,060 /*g/m3 (0.72 ppm) and smoke
shade in excess of 6 coh units, during a pe-
riod of atmospheric inversion and low-
ground-wind speed. The increased death
rates were shared by the 45-to-64 age group,
as well as by the age group over 65. In a
later episode (January 7, 1963) associated
with an S02 concentration of 1,715 /xg/m3
(0.6 ppm) and smoke shade at 6 coh units,
there was a peak of death rate apparently
superimposed upon an elevated death rate
average due to the presence of influenza vi-
rus in the community. Two further epi-
sodes "•" also suggest the relationship of
excess deaths to abrupt rises in both S02 and
suspended smoke at times of air stagnation.
An example of the inherent danger of re-
lating mortality peaks to air pollution is
shown by Leonard et al.18 in the Dublin stud-
ies. During the war and post-war years of
1941 to 1947, peat was burned as the main
fuel rather than coal, and air pollution (as
measured by particle concentrations) was
markedly decreased. Sulfur dioxide levels
varied in a manner similar to those of sus-
pended particulate matter. The winter peaks
in death, however, were unaffected, and thus
do not seem to be related to air pollution.
When coal again became available in 1948,
the air pollution levels rose with no appar-
ent effect on the death rate (see Figure 11-
3). Unfortunately, it is not possible to assess
the effects of changing medical practices and
the advent of antibiotics for use in treat-
ing respiratory diseases on these data.
In Detroit19 a rise in infant mortality and
deaths in cancer patients occurring over a
3-day period accompanied a rise in the 3-
day mean suspended particulate matter for
the same period above 200 /xg/m3 accom-
panied by an S02 maximum of 2,860 jug/m3
(1.0 ppm) (September 1952). This is not
believed to be related to the cold temper-
atures which have characterized the London
episodes.
In Osaka, Japan, Watanabe20 reported on
excess deaths in a December 1962 smog epi-
sode. There were 60 excess deaths related
to mean daily concentrations of suspended
matter greater than 1,000 /ig/m3, with ac-
companying S02 greater than 285
(0.1 ppm); the measurements were made at
a single station in the central commercial
area of the city.
When a marked increase in air pollution
is associated with a sudden dramatic rise in
the death rate or illness rate lasting for a
few days and both return to normal shortly
thereafter, a causal relationship is strongly
suggested. Sudden changes in weather, how-
ever, which may have caused the air pollu-
tion incident, must be considered as another
possible cause of the death rate increase.
Over the years, a number of such acute epi-
sodes have been reported, and there seems
little doubt that air pollution was the cause.
The British studies presented in this sec-
tion suggest that excess mortality, a small
rise in the daily death rate, is detectable in
large populations if the concentrations of
smoke and S02 rise abruptly to levels above
750 /xg/m3 and 715 /xg/m3 (about 0.25 ppm)
respectively; the same effects are noted in
American cities for S02 concentrations above
1,700 tig/m3 (about 0.6 ppm) and a "smoke
shade" of 6 coh units. The major targets are
the aged population, patients with chronic ob-
structive pulmonary disease, and patients
with cardiac disease. A more distinct rise
in deaths is noted generally when particulate
matter reaches about 1,200 /xg/m3 for one
day and sulfur dioxide levels exceed 1,000
/xg/m3 (about 0.35 ppm). Daily concentra-
tions of suspended particulates exceeding
2,000 /xg/m3 for one day in conjunction with
levels of sulfur dioxide in excess of 1,500
/xg/m3 (~0.5 ppm) appear to be associated
with an increase in the death rate of 20 per-
cent or more over baseline levels.
b. Morbidity
The acute episodes have resulted in sub-
stantial increases in illness. Thus a sur-
vey 21 of emergency clinics at major New
York City hospitals in November 1953 indi-
cated a rise in visits for upper respiratory
infections and cardiac diseases in both chil-
dren and adults in all of the four hospitals
studied. "Smoke shade" was close to 3 coh
units, and sulfur dioxide concentrations had
not yet exceeded 715 /xg/m3 (0.25 ppm) when
hospital admissions clearly rose.14
Again, the number of emergency clinic
154
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visits for bronchitis and asthma at seven
large New York City hospitals was examined
during the Thanksgiving 1966 air pollution
episode.22 There was a rise in the number
of such visits on the third day of the epi-
sode, among patients age 45 and over, at
three of the seven hospitals investigated. Un-
fortunately, the Thanksgiving holiday great-
ly complicated evaluation of the emergency
clinic visits over the holiday period.17
In the investigation of the London episode
of December 1952, information on illness
was collected from as many sources as pos-
sible including sickness claims, applications
for hospital admission, pneumonia notifica-
tions and records of physicians. The analy-
sis demonstrated a real and important in-
crease in morbidity, though there was some
indication that the increase in illness was
not as large proportionately as the increase
in deaths and the effects were not so sudden
in producing a marked rise in the early days
of the episode. In a number of other severe
London episodes the increase in morbidity
put a considerable strain on the health serv-
ices.
These episodes reflect results which fall
into Level IV of the World Health Organiza-
tion's "guides to air quality."23 These
"guides," equivalent in usage to our term
"criteria," cover sets of concentrations and
exposure times at which specified types of
effects are noted or at which no effect is
noted. Level IV includes "concentrations and
exposure times at and above which there is
likely to be acute illness or death in sus-
ceptible groups of the population."
2. Chronic (Long-Term) Air Pollution
Kurland 24 has called to our attention that
air pollution episodes represent, by defini-
tion, massive, overwhelming, and unusual ex-
posure, and thus the most significant patho-
logic effects. There is an "iceberg" effect
in that such data represent the obvious, while
the greater share of the problem remains
submerged. We are dealing with an essen-
tial dose-response situation, the upper limits
of which are represented by these episodes.
a. Day-to-Day Variations in Mortality and
Morbidity
In a systematic approach to analyzing res-
piratory and cardiac morbidity daily in Lon-
don, Martin 12 examined deviations in mor-
bidity from a 15-day moving average in Lon-
don during the winters of 1958-1959 and
1959-1960. Both smoke and sulfur dioxide
concentrations appear to be about equally
related to morbidity rates, and a definite ex-
cess in morbidity seemed to exist as it did for
mortality, though there was a somewhat
greater degree of irregularity.
An approach similar to Martin's, but limit-
ed to observations on mortality, was used by
McCarroll and Bradley16 in New York City.
Covering a 3-year period (1962-1964) they
examined a number of peaks in New York
City mortality associated with periods of
high air pollution. There are examples given
where sulfur dioxide and smoke shade ap-
pear to be related to mortality. The authors
present other episodes, however, where the
relationship to air pollution is not nearly as
clear, although the death rate fluctuates to
even higher peaks. Reference to this analy-
sis has already been made in our discussion
of the data on episodes in Section B.I.
McCarroll et al.22 studied residents of a
New York City housing project, using week-
ly questionnaires. Exact levels of air pol-
lutants which could be used for establish-
ment of air quality criteria were not given;
however, the data indicate that sulfur diox-
ide rather than particulate matter was asso-
ciated with eye irritation. Symptoms of
cough were also shown to be related to air
pollution but were not well differentiated be-
tween association with particles and sulfur
dioxide. The particular time-series analysis
used with these data is not well known, and
the biases inherent in its use have not been
fully determined.
b. Geographical Variations in Mortality
1. Studies Based on Available Data.—
Mortality and morbidity statistics each have
advantages as well as disadvantages. Rec-
ords of illness should be more fruitful in de-
fining subtle effects, since illness precedes
death and since all illness does not result
in death. Mortality statistics are collected
in every country and are available for quick
tabulation. Unfortunately, the quality of
mortality statistics varies. One of the prob-
156
-------
lems is that with the present system of tabu-
lating mortality data, a single cause of death
must be selected and coded, even though
more than one cause may be involved in the
death. The single cause of death designated
(e.g., specific chronic respiratory disease)
depends largely on the judgment of the at-
tending physician and has little, if any, rela-
tion to epidemiologic use. While contributing
causes of death appear on the death cer-
tificate, they are not reflected in summary
tabulations. The coding of only the "under-
lying" cause of death minimizes the impor-
tance of such diseases as emphysema which
often appear on the death certificate as con-
tributory or associated causes of death.25
Almost all studies of the effects of long-
term exposure on death rates compare the
rate in one area with that in another. Mor-
tality as well as morbidity studies are ham-
pered by the possibility of differences other
than air pollution existing between the areas,
such as social class, occupation, age, and sex
composition of the population, and cigarette
smoking. Assuming that almost all deaths
are recorded and tabulated, comparison of
total mortality rates (i.e., deaths from all
causes) obviates the bias of diagnostic selec-
tion, but does not lessen the chances of other
associated factors having caused the differ-
ence.
Buck and Brown 26 reported in 1964 the
relation of standardized mortality ratios for
the 5-year period 1955-1959 to four vari-
ables: daily smoke and S02 concentrations
for March 1962 (presumed representative of
the study period), population density in 1961,
and a social index of 1951. The studies in-
volved populations in 214 areas of the United
Kingdom (19 London boroughs, 49 county
boroughs, 70 boroughs, 61 urban districts,
and 15 rural districts).
Statistical studies indicate that bronchitis
mortality had a significant positive associa-
tion with both the smoke and the S02 con-
centrations encountered in these residential
areas, and also with social index. The stand-
ardized mortality rates for lung cancer were
not, in general, significantly associated with
smoke or S02 concentrations in the residen-
tial areas. Examination of the tables given
by Buck and Brown suggests that the ex-
cess of bronchitis mortality occurred for
classes of area where the average daily smoke
and S02 concentrations both exceeded 200
fi.g/m3. Although smoking habits were re-
viewed and were apparently uniform from
area to area, occupational and domestic in-
door environmental exposures were not con-
sidered. The pollutant values selected for
the correlations do not cover the same time
period as the mortality figures.
A series of papers by Stocks et al.,27-31
related atmospheric pollution in urban and
rural localities with mortality due to lung
cancer, bronchitis, and pneumonia. Stand-
ardized mortality ratios apparently refer to
the period 1950 to 1953 for bronchitis and
pneumonia and to the period 1950 to 1954
for lung cancer. Lung cancer mortality was
found to be strongly correlated with smoke
density in the atmosphere for 26 areas of
northern England and Wales, for 45 districts
of Lancaster and Yorkshire, and for 30
county boroughs. (Similar but weaker cor-
relations were observed within Greater Lon-
don.) Further, social differences in the popu-
lations concerned only partially explain this
correlation. Bronchitis and pneumonia for
males and bronchitis for females similarly
showed strong correlations with smoke den-
sity in the atmosphere. Cancers of the stom-
ach and intestine in the county boroughs
were also related significantly to smoke con-
centrations, and other relationships are de-
scribed for various areas of the country. It
is, however, difficult to extract specific quan-
titative "effect" levels for smoke or the other
pollutants studied. Papers 30> 31 describe the
statistical elimination applied to develop sig-
nificant correlations of spectographic analy-
ses of 13 trace elements with mortality rates.
Reanalysis of the data by Anderson 32 con-
firmed the importance of smoke levels, as
well as social and population parameters, to
mortality from lung cancer; vanadium is also
identified as an important independent con-
tributor to lung cancer, female cancer, and
pneumonia mortalities.
In summary, the results of this analysis
of long-term mortality indicate effects which
would coincide with Level III of the World
Health Organization's "guides to air qual-
ity." 23 Level III is defined as "concentrations
157
-------
and exposure times at and above which there
is likely to be impairment of vital physiologic
functions or changes that may lead to chronic
diseases or shortening of life."
2. Special Studies Involving the Collection
of New Data.—In 1964, also, Wicken and
Buck 33 reported on a study of bronchitis and
lung cancer mortality in six areas of North-
east England, one in Eston, another in Stock-
ton and four in rural districts. The deaths
covered the period 1952 to 1962. The survey
of decedents with cause of death from bron-
chitis or lung cancer was matched against
the survey of decedents with cause of death
from nonrespiratory disease controlled for
age and sex; the basis for the diagnostic
classifications was not stated in the report.
Personal interviews were carried out with
next of kin. Personal interviews of a ran-
dom sample of households were also con-
ducted to obtain sex, age, smoking habits and
occupation of the population at risk, the liv-
ing population. The survey of decedents was
carried out between January and October
1963; the survey of the living population was
carried out between December 1963 and
March 1964. Smoke and sulfur dioxide con-
centrations were measured in the Eston ur-
ban district. One year's aerometric data was
obtained. The study was excellent in prin-
ciple though, unfortunately, sulfur dioxide
and particulate values were available only
for the Eston urban district.
Eston, itself, as a sub-study, was subdi-
vided into North Eston and South Eston.
North Eston contains or lies near heavy in-
dustrial plants, whereas South Eston is a
residential area. During the period May
1963 to April 1964, mean weekly observa-
tions of the sulfur dioxide and smoke con-
centrations were carried out in two sites in
North Eston and one station in South Eston.
Smoke values were 160 /tg/m3 and 80 /ag/m3
for North and South Eston respectively. The
sulfur dioxide value in North Eston on the
yearly average was 115 /ig/m3 (0.040 ppm)
and for South Eston it was 74 yug/m3 (0.026
ppm). The deaths studied occurred between
1952 and 1962. Adjustments were made for
differences in age composition, smoking hab-
its, and social class, and these were insuffi-
cient to explain the differences in lung can-
cer and bronchitis mortality rates between
the two localities. Occupational exposure to
pollution was then taken into account in the
analysis. The conclusion was that there is
an association between the degree of air
pollution and the incidence of lung cancer
and bronchitis mortality in the two areas of
the Eston urban district. Though both sul-
fur dioxide and smoke values and concen-
trations are furnished in the report and the
effects apparently cannot be separated, Bras-
ser et al.s apparently have used the sulfur
dioxide concentration as the more relevant
measure of this study.
The community of Salford was classified
into three pollution areas by Burn and Pem-
berton,34 according to Table 11-1. Five sam-
pling stations in the area were employed.
Despite the closeness of the ranges of values,
a high rate of bronchitis mortality, of lung
cancer mortality, and of deaths from all
causes, was observed in the high, compared
to the lower pollution wards. It appears (see
Section C-4) that there was also an increased
rate of bronchitis morbidity in the highly
polluted wards.
Winkelstein et al.35~31 analyzed pollution
effects in a group of studies made in the
Buffalo, New York, area. In July of 1961,
21 air sampling stations were set up in and
around the city of Buffalo, and daily values
for suspended particulates, dustfall, and ox-
ides of sulfur were taken until June of 1963.
Suspended particulate levels were used as
the index of air pollution. On the basis of
the measurements, the study area was di-
vided into four contiguous areas "according
to their levels of air pollution. Level 1 was
less than 80 /xg/m3 (2-yr. geometric mean);
level 2, 80 /*g/m3 to 100 /xg/m3; level 3,
100 jug/m3 to 135 (Ug/m3; and level 4, greater
than 135 ju.g/m3. Each area was also divided
into five economic groupings. Mortality fig-
ures for the area were taken from the period
1959 to 1961, with the 1960 census provid-
ing the population basis.
Annual death rates per 100,000 popula-
tion for (1) all causes of death; (2) chronic
respiratory disease; (3) malignant neo-
plasms of the bronchus, trachea, and lung;
and (4) gastric carcinoma were related to
the four areas of air pollution intensity and
158
-------
Table 11-1.—POLLUTION LEVELS IN SALFORD (SEASONAL DAILY AVERAGES)*4
Pollution area
classification
High
Intermediate
Low
SO2 A
-------
dioxide concentrations and soiling indices
from 36 stations. All codable deaths regis-
tered between 1949 and 1960 (32,067) were
then distributed among census tracts rated
according to high, moderate, and low pollu-
tion levels, and upper, middle, and lower eco-
nomic classes, and then further coded by age,
sex, race, and underlying cause of death.
Standardized mortality ratios (for total res-
piratory disease, and for pneumonia, influ-
enza, bronchitis, emphysema, tuberculosis,
and lung and bronchial cancer) were then
50
140
40
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1234
PARTICULATE LEVELS
(all economic levels)
FIGURE 11-4. Average Annual Death Rate from All
Causes. (The graph shows the death rate per 1,000
population for white males between 50 and 69 years
of age for four levels of particulate matter, Buffalo
and environs, 1959-1961.)
HI
I
LU
D
D
Z
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120
100
80
60
40
20
SiSSS-iS:
•;•$:$:•:':•£•
'•ffffftt-S:
mm®
:•:•:•:•:•:•:•:•:•*
PARTICULATE LEVELS
(all economic levels)
FIGURE 11-5. Average Annual Death Rate from Asth-
ma, Bronchitis, or Emphysema Indicated on the
Death Certificate. (The graph shows the death
rate per 100,000 population for white males be-
tween 50 and 69 years of age for four levels of par-
ticulate matter, Buffalo and environs, 1959-1961.)
Table 11-3.—AVERAGE ANNUAL DEATH RATES PER 100,000 POPULATION FROM CHRONIC RESPI-
RATORY DISEASE ACCORDING TO ECONOMIC AND PARTICULATE LEVELS, AND AGE: WHITE
MALES, 50-69 YEARS OF AGE, BUFFALO AND ENVIRONS, 1959-1961.
Economic
Level
Particulate Level
1 (Low)
a Rate based on less than five deaths.
160
4 (High)
Total
1 (low)
2 . .
3
4
5 (high)
Total
. .
64
—
35
. . 42
44
0*
75
65
47
63
62
126
96
51
114
0*
94
188
105
103 a
—
129
133
84
64
52
50
72
-------
100
z
o
o
Q.
50
w
<
LLI
Q
PARTICULATE LEVELS
(economic levels 2, 3, and 4)
4
(HIGH)
FIGURE 11-6. Average Annual Death Rate from Gas-
tric Cancer. (The graph shows the death rate per
100,000 population for white males between 50 and
69 years of age for four levels of particulate mat-
ter, Buffalo and environs, 1959-1961.)
related to the pollution indices obtained dur-
ing 1959. The statistically significant mor-
tality increases were those for all respira-
tory diseases related to sulfation and soil-
ing; lung and bronchial cancer mortality, and
bronchitis and emphysema mortality were
not clearly related. "High" pollution in these
studies referred to soiling at more than 1.1
coh units/1,000 linear feet and S02 concen-
trations of more than about 30 ng/ms (.01
ppm). A later paper40 derived from the same
study period, analyzed infant and fetal death
rates between 1955 and 1960. For white in-
fant mortality, significant regressions were
obtained for sulfation; dustfall (alone, or as
an interaction variable) was the most fre-
quently related variable. In the study, ac-
count was not taken of smoking habits of
the deceased; also, the "middle class" group
covered a relatively large segment of the
decedents.
It is intresting to note that the associa-
tion between suspended particulate levels
and gastric cancer in the Buffalo study which
appeared to be independent of economic sta-
tus was also observed in the Nashville
study.38
c. Geographic Variations in Morbidity—
Special Studies
It has been postulated that the study of
records of illness rather than mortality
should be more fruitful in defining subtle
effects, since morbidity is an earlier and
more sensitive index of deviation from nor-
mal health. A much larger insult must pre-
sumably be given to the body to cause death
than to cause illness. Routinely collected
morbidity data are, however, not generally
available. Data may occasionally be obtained
from group insurance plans, hospital admis-
sion records, or existing school records. Since
such data are usually not collected in a uni-
form, precise manner, most morbidity stud-
ies require expensive and time-consuming
field surveys with questionnaires or actual
medical examinations of the subjects.
Morbidity studies of adults involving long-
term exposures are frequently not as useful
Table 11-4.—AVERAGE ANNUAL DEATH RATES PER 100,000 POPULATION FOR GASTRIC CANCER
ACCORDING TO ECONOMIC AND PARTICULATE LEVELS: WHITE MALES, 50-69 YEARS OF
AGE, BUFFALO AND ENVIRONS, 1959-1961.
Economic
Level
1 (low)
2 .
3
4 . . . :
5 (high)
Total
Particulate Level
1 (Low)
.
45(5)
—
15(3)
26(5)
26(13)
2
0(0)
41(12)
39(9)
38(9)
16(3)
34(33)
3
63(10)
48(10)
51(6)
63(5)
0(0)
53(31)
4 (High)
136(8)
84(8)
51(2)
—
— -
—
Total
77(18)
50(35)
44(17)
33(17)
20(8)
42(95)
Figures in parentheses indicate numbers of deaths
161
-------
as desired due to the presence of complicat-
ing factors such as occupation and smoking.
Accordingly, Anderson 30 has recommended
that children and housewives be used to de-
termine the health effects of air pollution.
A study was conducted by Petrilli et al.41
in Genoa, Italy, which followed Anderson's
recommendation. The subjects were women
over 65 years of age, nonsmokers who had
lived for a long period in the same area and
who had no industrial work experience. Eco-
nomic and social conditions in the areas of
residence were thus considered as well as
the levels of pollution in the areas of their
residence. Pollutant measurements were car-
ried out between 1954 and 1964 in 19 differ-
ent areas, and morbidity indices were cal-
culated for 1961 and 1962 for this popula-
tion, which received free medical care from
the municipality and therefore was under
continuous medical observation. There was
a significant correlation between the fre-
quency of bronchitis with mean annual sul-
fur dioxide levels (r = 0.98) and a nonsig-
nificant correlation for mean annual sus-
pended matter (r = 0.82) and mean annual
dustfall (r = 0.66).
Toyama,42 in a comprehensive study of air
pollution and its health effects in Japan,
charts the age-standardized morbidity rates
(per thousand) secured by interview survey
in 1961, and describes a gradient of respira-
tory disease morbidity from the highly in-
dustrialized (and presumably polluted) areas
to the rural areas of Japan. Further, the
pulmonary disease morbidity ratio was
higher in the industrialized, polluted areas
than were the ratios for other disease group-
ings. The gradient was not noted for cardio-
vascular diseases nor for gastrointestinal
diseases. Unfortunately, specific pollutant
concentrations are not clearly indicated to
accompany these data on morbidity. The
age-standardized morbidity rates per thou-
sand for several cities in Japan are shown
in Figure 11-7.
Holland et al.43 studied the prevalence of
chronic respiratory disease symptoms and
performance of pulmonary function tests in
a comparative study of outdoor telephone
workmen in London, in rural England, and
on the east and west coasts of the United
States. Types of occupational exposure, use
of cigarettes, and socioeconomic matching
were considered. The annual mean concen-
tration of suspended particulate matter in
the British exposures was approximately 200
/tg/m3, and approximately 120 /ig/m3 in the
American case. For sulfur dioxide, the mean
concentrations were: in London 300 /tg/m3
(—0.1 ppm), in rural areas of England 60
jug/m3 (~0.02 ppm), and in the United
States between 30 /ig/m3 and 120 /*g/m3
(~0.01 ppm and ~0.04 ppm). Persistent
C RESPIRATORY
r
! I
V
\
1
1
J .
II]
3 —~*
C III
0 10 20 30 (
CARDIOVASCULAR
ZH
I
I
I
zn
1
) 10 (
GASTROINTESTINAL
I
I
I
I
I I
) 10 20 3
KAWASAKI
YOKOHAMA
FUJI NO
KAINAN
DAITO
0
RATE PER THOUSAND
FIGURE 11-7. Age-Standardized Morbidity Bate per 1,000 for Three Types of Diseases in Japan." (The
mortality rate for respiratory diseases shows a clear correlation with pollution levels. There is no such clear
correlation for cardiovascular or gastrointestinal disorders.)
162
-------
cough, phlegm, and chest illness episodes and
increased sputum volume were all signifi-
cantly more frequent in men (between the
ages of 50 and 59) in the London area than
in rural England; and pulmonary function.
was poorer in relation to the levels of smoke
and sulfur dioxide. It is possible, therefore,
that an increase in smoke concentration from
120 ju.g/m3 to 200 |U.g/m3 (with an equivalent
increase in sulfur dioxide level) increases
the risk to older workers of deteriorated pul-
monary function and increased symptomatol-
ogy of chronic respiratory disease. Table
11-5 summarizes some of the results ob-
tained.
Holland and Reid 44 reviewed respiratory
symptoms, sputum production, and lung
function levels in post office employees both
in central London and in peripheral towns.
Over the age of 50, the London men had more
frequent and more severe respiratory symp-
toms, produced more sputum, and had sig-
nificantly lower lung function tests. Socioeco-
nomic factors were presumed the same, the
occupational exposures were homogenous,
and corrections were applied for smoking.
There were some physique differences in the
rural areas and allowances were made for
these in the statistical evaluation. Unfortu-
nately, no quantitative air quality determina-
tions accompanied these results. The authors
nevertheless concluded that the most likely
cause of the difference in respiratory mor-
bidity between the men working in Central
London and those in the three rural areas
was related to the differences in the local air
pollution.
In a group of Canadian veterans studied
by Bates et al.,i5 a relationship between air
pollution and both bronchitis and pulmonary
function measurements has been reported.
There are, unfortunately, inadequate data
on the levels of smoke, sulfur dioxide, and
other pollutants, in the four Canadian cities
compared, to derive specific relationships be-
tween the levels of these pollutants and the
Table 11-5.—RESPONSE OF TELEPHONE WORKERS IN THE U.K. AND U.S.A. TO AIR POLLUTION.'3
United Kingdom
London
Age
40-49
Number of men examined - -
Persistent cough and phlegm
(percent)
Persistent cough and phlegm and
chest illness episode (percent)
FEVi.o (liters) mean values:
Non smokers
Cigarette smokers:
1-14 per day ...
15-24 per day
25 or more per day
Sputum volume 2 cc. or more
(percent)
113
25.
10.
2.
2.
2.
2.
28.
7
6
8
6
6
5
9
Age
50-59
137
38.7
10.9
2.6
2.3
2.2
2.1
42.9
Age
40-49
267
24.
7.
3.
2.
2.
2.
22.
0
5
0
8
8
7
1
Rural
areas
Age
50-59
159
18.
5.
2.
2.
2.
2.
23.
9
0
8
6
5
5
5
United
Baltimore
Washington
Westchester
County
Age
40-49
396
22.2
6.8
3.5
3.4
3.2
3.2
7.1
Age
50-59
229
25.8
7.0
3.1
3.0
2.8
2.9
10.0
States
San Francisco
Los Angeles
Age
40-49
361
21.6
4.0
3.7
3.4
8.6
Age
50-59
119
24.4
7.6
3.3
2.8
14.3
Suspended particulate matter,
24 hr (/.g/m«):
Mean
Maximum
Sulfur dioxide, 24 hr (>ig/m3),
ppm in parentheses:
Mean
Maximum
220
4000
290 (0.1)
3700 (1.3)
200
3000
60 (0.02)
740 (0.26)
120
500
110 (0.04)
715 (0.25)
120
340
30 (0.01)
170 (0.06)
163
-------
prevalence or exacerbation of disease or the
deterioration of pulmonary function. How-
ever, there is an association in the "dirty"
cities (Montreal and Toronto) versus the
"clean" cities (Halifax and Winnipeg) of
increased prevalence and severity of bron-
chitis, and poorer pulmonary function per-
formance.
Anderson and Ferris 46> 47 completed a com-
parison of respiratory disease incidence and
air pollution in three residential areas of
Berlin, New Hampshire, by prevalence sur-
vey. Subjects who were nonsmokers and
those who were moderate smokers were spe-
cifically evaluated. The different levels of
air pollution at one or more stations in each
area were recorded in relation to monthly
dustfall and to sulfur dioxide concentration.
Prevalence of respiratory disease and pul-
monary function determinations (FEVi.ft
and peak expiratory flow rate) were made.
The mobility of the population, variations
of concentrations of pollutants within a given
area, possible effects from the area of occu-
pation, and differences in the in-home en-
vironment, were considered as contributors
to the lack of consistent effect on the studied
parameters of air pollution. In a later
study "8 these authors compared this "pol-
luted" town in New Hampshire with a con-
trol community in British Columbia and
again found an obscuring of the effects of air
pollution on respiratory symptoms and pul-
monary function performance, suggesting
perhaps the overwhelming effect of cigarette
smoking in symptom production. It should
be noted, however, that the pollution levels
and the ranges were possibly too low or too
small to show a relationship.
The Nashville air pollution study49 re-
viewed total morbidity in relation to air pol-
lution. A wide matrix of sampling stations
was used to group the residence of individ-
uals into areas of high, moderate, and low
pollution according to geometric mean an-
nual measurements, and the morbidity data
were secured by home interview. Significant
"direct correlations" of total morbidity with
levels of pollution (measured by soiling in-
dex and 24-hour sulfur dioxide levels) were
observed for individuals over 55 in the mid-
dle socioeconomic class. Cardiovascular dis-
eases were directly correlated with the aero-
metric parameters. There was no statistical
evidence of increased respiratory disease
morbidity or morbidity of other organs and
systems. The same qualifications noted for
the mortality data in this study apply to
these data on morbidity.
d. Morbidity—Incapacity for Work
Dohan50 reviewed the incidence of res-
priatory disease producing absence from
work in a population of women employed
in several branches of an electronics com-
pany in the eastern part of the United
States. Pay scales were roughly equivalent
and presumptions were made, therefore, that
the socioeconomic status and smoking pat-
terns were uniform. Air measurements were
made from areas near the town of employ-
ment (for suspended particulate sulfates, ni-
trates, copper, zinc, vanadium, nickel, and
acetone-soluble organic matter, as well as
total suspended particulate matter). Ab-
sences for a respiratory illness in excess of 7
days were calculable from company-employ-
ment and health-insurance records. There
was a significant correlation of respiratory
disease absence frequency with the concen-
tration of suspended • particulate sulfates,
with 24-hour values measured biweekly; al-
though the level of total suspended particu-
late matter ranged from 100 /tg/m3 to 190
jug/m3 in the various cities, a correlation was
not demonstrated. The implication of the
significantly correlated datum "suspended
particulate sulfate" is not clear, as it might,
for example, be an index of the community
fuel consumption or an index of sulfur di-
oxide irritation.
Burn and Pemberton 3* reviewed the in-
creased number of certificates of incapacity
issued to workers in Salford in relation to
smog episodes. When mean daily smoke pol-
lution, based on data from five sampling
stations, exceeded 1,000 /xg/m3 for 2 consecu-
tive days, the number of "bronchitis cer-
tificates" issued exceeded the expected num-
ber by a factor of two, on four or five oc-
casions in 1958.
During 1961-1962 a study of the inci-
dence of incapacity for work was conducted
by the British Ministry of Pensions and Na-
164
-------
tional Insurance.51 The population covered
was representative of the working popula-
tion of England and Wales. Rates of sick-
ness absence for bronchitis, influenza, arth-
ritis and rheumatism were related to in-
dices of pollution. There was a significant
correlation between bronchitis incapacity in
middle-aged men (35-54) and the average
seasonal (October through March) levels of
smoke and sulfur dioxide in high-density
residential districts, based on 24-hour meas-
urements. For Greater London, there was a
significant correlation between bronchitis
incapacity and both smoke and sulfur di-
oxide for all age groups taken together, and
for men aged 35 to 54 and 55 to 59. It is
interesting that there was also more incapac-
ity from arthritis and rheumatism in areas
having heavy smoke pollution. Influenza in-
capacity was greater in those areas with
higher pollution levels over Great Britain
as a whole but not within the Greater Lon-
don conurbation, nor was there in this lat-
ter area any association between pollution
and psychosis or psychoneurosis. The low-
est bronchitis inception rates related to
smoke levels between 100 /ug/m3 and 200
/«g/m3 and to sulfur dioxide concentrations
between 150 /*g/m3 and 250 /*g/m3 (0.053
ppm and 0.081 ppm). The highest values
related to particulate concentrations of 400
iug/m3 and 400 //.g/m3 (0.14 ppm) sulfur di-
oxide.
Verma et al.,->2 presented information on
illness absences in relation to air pollution.
Illness data for the employees (males and
females, ages 16 through 64) of a metro-
politan New York insurance company were
obtained through the records of the person-
nel department. They included medical his-
tory, X-ray information, and laboratory re-
sults obtained by the medical department of
the company, and were classified by absences
due to respiratory illness and to nonrespira-
tory illness. Mean daily concentrations of
air pollution and meteorologic data were se-
cured from the monitoring system of metro-
politan New York: smoke shade, sulfur di-
oxide, and carbon monoxide content were re-
ported. The data for the 2 years 1965 and
1966 were examined statistically and several
conclusions were reached. There was a
strong time dependence, and yearly cyclical
behavior; when this factor was removed
there remained no strong positive relation-
ship between respiratory absence and the
pollution variables studied. Respiratory ill-
ness absence rates were at their highest
level when sulfur dioxide and smoke shade
levels were both high on cool days; and a
lag effect for respiratory absences was not
noted.
3. Studies of Children
Comparisons of the prevalence of respira-
tory disease in areas of varying pollution
levels have been made to delineate the role
of air pollution and specific pollutants. A
problem common to all the studies is the
difficulty in guaranteeing that the areas are
similar (except for air pollution) in all fac-
tors that might affect the prevalence of
disease.
Because studies on adults tend to be com-
plicated by smoking habits, changes of oc-
cupations, and changes in address over a
period of years, several studies have been
directed at effects of air pollution on school
children. The advantages of utilizing chil-
dren for research on the primary etiologic
effects of air pollution were first noted by
Reid53 several years ago; Anderson32 has
most recently reaffirmed this view. A major
element of concern is that deleterious effects
on the respiratory system of very young
children may have an effect on the subse-
quent evolution of the chronic bronchitis syn-
drome in the adult population.
The relationships of respiratory infections
to long-term residence in specific localities
have been studied in England by Douglas
and Waller.54 Levels of air pollution, in
terms of domestic coal consumption records,
were used to classify four groups; the auth-
ors include an evaluation of the validity of
this method at the end of their report. The
histories of 3,866 children born during the
first week of March 1946 were followed until
1961, when the children were 15 years of
age. Social class composition of these chil-
dren did not differ significantly from area
to area. Measured concentrations for smoke
and for S02 in 1962 and 1963 were com-
pared with the earlier prediction of pollu-
tion intensity based on the coal consumption
165
-------
data, and indicated an overlap for the greater
London area of low and moderate groupings;
for other areas, the predicted gradient of
concentrations was affirmed. Because of the
age of the subjects, smoking was apparently
not considered in this evaluation. In 1965,
19 percent of the boys and 5 percent of the
girls, aged 11 to 13, smoked at least one
cigarette a week regularly.55
In the Douglas and Waller study, the gen-
eration of pollutants in the indoor home en-
vironment (e.g., by heating and cooking)
was not considered. Interviews were con-
ducted with the mothers when the children
were 2 and 4 years of age; information was
obtained about upper and lower respiratory
illness and recorded hospital admissions for
these and other causes. Data about colds,
coughs, and hospital admissions were also
gathered by school doctors at medical ex-
aminations when the children were 6, 7, 11
and 15 years of age. Between the ages of
6V& and 10i/£, special records for causes of
school absence exceeding one week were re-
viewed with the mothers. A total of 3,131
families remained in the same pollution area
throughout the first 11 years of this study.
The conclusions of the study were that upper
respiratory tract infections were not related
to the amount of air pollution, but that lower
respiratory tract infections were. Frequency
and severity of lower respiratory tract in-
fections increased with the amount of air
pollution exposure, affecting both boys and
girls, and with no differences detectable be-
tween children of middle class and working
class families. This association was found
at each of the examination ages, including
age 15. At age 15, persistence of rales and
rhonchi (chest noise), possibly the prodrome
of adult chronic respiratory disease, was
some tenfold less in the very low pollution
area, and a factor of two less in the low pol-
lution area than that in the high pollution
area. If the 1962-1963 measured concentra-
tions for smoke and S02 can truly be extrap-
olated to the 15-year respiratory illness sur-
vey, then these British school children ex-
perienced increased frequency and severity
of lower respiratory diseases in association
with annual mean smoke concentrations
ranging above 130 /ig/m3 and SO2 above 130
//.g/m3 (0.046 ppm).
The lower respiratory tract findings of
Douglas and Waller were confirmed in a
study by Lunn et a£.56 The patterns of res-
piratory illness in school children of the age
group 5 to 6 have been studied with ref-
erence to residence in four areas of Sheffield.
Mean daily smoke levels measured in each
of four areas ranged from 97 jug/m3 in the
"low" area to 301 /ig/m3 in the "high" area;
S02 concentrations were respectively 123
/ig/m3 (0.043 ppm) and 275 ^g/m3 (0.096
ppm) in the two areas, during 1963-1964.
Somewhat lower pollution levels were noted
the following year, although the gradient be-
tween the districts was preserved. Ques-
tionnaire to the parents, physical examina-
tion, observation for the presence of nasal
discharge, examination of the eardrums, and
recording of both the forced expiratory vol-
ume of 0.75 seconds (FEV0.75) and the
forced vital capacity (FVC), were completed
during each of the summer terms of 1963,
1964, and 1965. Several socioeconomic fac-
tors were compared for the various districts;
smoking was appropriately disregarded for
this age group; internal home environments,
or differences in home heating systems, were
not reported. The authors conclude that
there is an association with the levels of at-
mospheric pollution and chronic upper res-
piratory infections (as indicated by muco-
purulent nasal discharge, history of three
or more colds yearly, or scarred or perfo-
rated eardrum). Further, lower respiratory
tract illness (measured by history of fre-
quent chest colds or episodes of bronchitis
or pneumonia) was similarly associated.
Functional changes, in the form of reduced
FEVo.75 ratios emerged where there was a
past history of pneumonia or bronchitis, of
persistent or frequent cough, or of colds
going to the chest. There appears, there-
fore, to be a persistence of respiratory dys-
function, even in the absence of high-pollu-
tion extant at the time of the function
testing. The lowest "effect" level for smoke
and S02 is not clearly indicated by this
study, but the increased association of "res-
piratory infections" in school children can
be detected for areas whose mean daily fig-
166
-------
ures exceed about 100 /4T/m3 for smoke and
120 jug/m3 (0.042 ppm) for S02.
The exacerbation of acute respiratory ill-
ness of school children in Ferrara, Italy, has
been studied by Paccagnella et ol57 Air pol-
lution measurements from 1959 through
1964 permitted definition of high, medium,
and low zones of pollution. School children
in the age range 7 to 12 had daily examina-
tions, and the date of onset of acute respira-
tory disease was recorded. Although climatic
conditions were related to changes in pollut-
ant levels, the onset of acute respiratory dis-
ease in the children was not correlated sig-
nificantly with changing air pollution values,
except in the poorest socioeconomic area.
The pollutant values for this community are,
however, lower than those encountered in
the British studies previously discussed (20
/xg/m3 to 45 jug/m3 annual mean). In fact,
these are levels which are lower than many
rural values in the United States.
Toyama42 studied two groups of school
children, 10 to 11 years old, in Kawasaki,
Japan. Sulfation rates at the school in the
more polluted area varied from 0.5 to 1.9
and averaged 0.9 mg/100cm2-day Pb02; no
sulfation rates were given for the school in
the area of lower pollution. Dustfall was
considerably less in the area of lower pol-
lution (ranging from about 5 tons/km2-
mo. to 15 tons/km2-mo.) * than in the more
polluted area (ranging from about 15 tons/
km2-mo. to 70 tons/km2-mo.). The children
from the more polluted area had a higher
frequency of nonproductive cough, irritation
of the upper respiratory tract, and increased
mucus secretion. Whether the effect was due
to oxides of sulfur or particulate matter can-
not be determined from this study.
A study by Manzhenko 5S of upper respira-
tory tract conditions in school children in
Irkutsk is difficult to relate to the Sheffield
study. However, the higher incidence of res-
piratory tract conditions and the undefined
abnormal X-ray findings in these children's
lungs are disturbing evidence of the possi-
bility of an association between serious res-
piratory disease and residence in a polluted
community.
4. Studies of Pulmonary Function
Holland et al.*s report decreased perform-
ance of the FEVi.o test in London and Brit-
ish rural outside telephone workers com-
pared with their American counterparts.
For both groups the FEV was further de-
creased in relation to smoking intensity.
FEV differences within the United Kingdom
workers (i.e., London versus rural) could
also be related to the sulfur dioxide concen-
trations accompanying the particulate lev-
els. A more detailed discussion of the study
appears in Section C-4.
Toyama 42 reported measurements of peak
flow rate and total vital capacity perform-
ance in Japanese school children in areas of
differing air pollution, measured monthly;
fluctuations were observed in the mean peak
flow rates of children attending schools and
living in polluted industrial areas; and the
variations were smaller for children in
clearer areas. Total vital capacity was not
significantly different between pupils of the
various schools. There was a substantial
difference in peak flow rates between the
two school districts at times of highest pol-
lution. When pollution values were lowest,
the differences were less. The lowest values
related to dustfall measurements of 60
tons/km2-mo.* and daily sulfur dioxide levels
equivalent to 20 /xg/cm2 (lead candle meas-
urement) .
In Osaka, Watanabe20 studied the peak
flow rate and vital capacity performances by
the children of schools enduring differing air
pollutant concentrations. It was noted that
individual peak flow rates were more mark-
edly decreased in the winter months (Sep-
tember to December, 1963) for the school
in the highly polluted area than for the
school in the low pollution area. Daily mean
concentrations of both dustfall and sulfur
dioxide concentrations were twice as great
in the polluted area as in the unpolluted area.
In a comparison by Prindle et a/.59 of pul-
*In the United States, dustfall is measured in
tons/mi2-mo.
*In the United States, dustfall is measured in
tons/mi2-mo.
167
-------
monary function and other parameters in
two Pennsylvania communities with widely
different air pollution levels, average airway
resistance and specific airway resistance
were measured in persons 30 years of age
and older. These measurements were per-
formed at several stations in each of the com-
munities and indicated differences between
the high-pollution and low-pollution commu-
nities which were probably related to the
sixfold greater dustfall. However, smoking
and occupation were not accounted for.
In the paper by Lunn et al.,5S Sheffield
school children were shown to have reduced
FEVo.75 and FVC ratios in the area of high-
est pollution. The measurements were made
during the summer, when pollution levels
were low and apparent incidence of acute
respiratory infection was diminished, sug-
gesting, in contrast to the Japanese studies
referred to above, that there may be per-
sistence of the respiratory function deterio-
ration in relation to residence in the area of
high pollution; mean daily averages meas-
ured at a single station were: smoke, 300
Mg/m3; SO2, 275 /*g/m3 (0.096 ppm).
The studies relating morbidity and deteri-
oration in pulmonary function to particulate
levels cover effects which are also included
in Level III of the World Health Organiza-
tion's "guides to air quality."23
5. Studies of Panels of Bronchitis Patients
Lawther"° related several episodes of
acute urban pollution to worsening of con-
dition in a group of bronchitic patients, well
studied in a registry at St. Bartholomew's
hospital. Changes in their symptomatology
were recorded in a daily diary and acute
worsening in significant numbers of the
group was associated with daily rises in air
pollution above 300 /xg/m3 of smoke and 600
jug/m3 (0.21 ppm) of sulfur dioxide. Figure
11-8 shows graphically the effects observed
on 29 bronchitic patients of high pollution
levels in January 1954.
Angel et al.S2 reviewed the occurrence of
new respiratory symptoms in men, working
in factories and in offices, most of whom
had prior evidence of chronic bronchitis.
The study group of 85 men observed through
the winter of 1962-1963 was selected from a
group of 1,000 men, age 30 through 59, with-
out apparent classification of either smoking
patterns or possible occupational or residen-
tial exposure differences. Increased sputum
production, deterioration of pulmonary func-
tion performance (FEVi.o), and the more
frequent occurrence of respiratory symp-
toms classified as "upper" (coryza, influenza,
and acute respiratory disease), and "lower"
(chest colds, bronchitis, wheezy attacks,
pneumonia) were all associated with in-
creases in both smoke and sulfur dioxide
concentrations. There was frequently diffi-
culty in defining an exacerbation of disease
in those individuals already experiencing
chronic bronchitis. During this period, ill-
ness peaks (attack rate) may have occurred
with weekly mean concentrations of smoke
exceeding 400 /*g/m3 and of sulfur dioxide
exceeding 460 /ig/m3 (0.16 ppm); weekly
mean concentrations were calculated using
the highest daily mean occurring each week
at each of 13 locations in the area.
BiersteckerS3 surveyed male municipal
employees in Rotterdam for symptoms of
bronchitis and for peak flow meter perform-
ance, and reviewed years of residence in
Rotterdam versus years of residence in a
nonurban environment as well as smoking
habits. The individuals with bronchitis
symptoms were matched with individuals
without such symptoms but with similar age
and background. Significant differences re-
lated to heavy cigarette smoking, but no
reliable statistical indication of an effect of
urban or nonurban residence in the produc-
tion of symptoms was detectable. Since par-
ticulate levels in Rotterdam are very low, the
range of difference between particulate levels
in Rotterdam and the nonurban environment
may have been close to minimal.
Fletcher et al.6i followed 1,136 working
men aged 30 to 59 in West London by sur-
veys at 6-month intervals. The surveys in-
cluded collection and measurement of morn-
ing sputum volume, FEV, and respiratory
symptom questionnaires. While expected
patterns of decline in lung function with age
occurred and this was the most rapid in
cigarette smokers with low lung fuction to
start with, an unexpected finding was a de-
crease in sputum volume in men with con-
stant smoking habits. This was most con-
168
-------
16
17
18
MEAN
TEMP°F
SMOKE
mg/m3
RH
60 PERCENT
so2
ppm
NUMBER
OF
PATIENTS
WORSE
BETTER
JANUARY 1954
FIGURE 11-8. Effect on Bronchitic Patients of High Pollution Levels (January 1954).6061 (The figure repre-
sents the effect on bronchi tic patients of increased pollution levels; patients stated whether they regarded
their condition as "worse" or better".)
sistent in the winter samples, but showed a
significant trend in samples taken together
as well as in the winter samples. (Trend
data are based on 825 men who attended
at least nine periodic examinations.) The
authors felt this was possibly due to a de-
cline in air pollution in London. They pre-
sented data on trends in S02 and black sus-
pended matter which indicated that there is
a consistent downward trend in particulate
pollution (highly significant) but a less
steady decline in S02.
This unique set of data could mean that
with a decrease of smoke pollution (yearly
mean) from 140 jug/m3 to 60 /tg/m3, there is
an associated decrease in mean sputum vol-
ume during the first morning hour from
about 1.5 ml to about 0.75 ml. A contribu-
tion of the decrease in S02 is less likely than
that of the decrease in smoke. Possible
changes in cigarette tars, in methods of
smoking and in techniques for collecting a
sample, or other factors, could have influ-
enced this result.
1st hour sputum volume—In men of
constant smoking habits
1961 1962 1963 1964 1965 1966
Summer 1.65 0.83 0.93 0.93 0.83 0.72
Winter 1.38 1.27 1.20 1,13 0.70 .
D. SUMMARY
This chapter reviews epidemiologic studies
of the relationship between pollutant con-
centrations and their effects on health. In-
dices varying from disturbance of lung func-
tion to death are considered. Concentration
measurements of pollutants are sometimes
available for the period during which the
169
-------
indicators were under review, and in these
cases it is possible to state pollutant levels
at which an effect is noted. However, such
values cannot be taken to mean that effects
will not be noted at lower concentrations.
Most studies involving long-term effects
using a geographic area comparison will use
the cleanest area as the "control" area
against which mortality and morbidity dif-
ferentials are to be found. This necessarily
assumes that this "cleanest" area itself does
not have any effects from its level of pollu-
tion. Conversely, some studies have com-
pared areas with very low particulate load-
ing or with very limited ranges of differ-
ences. It is not possible to demonstrate any
relationship under conditions of minimum
values or minimal differences. Table 11-6
summarizes the epidemiologic studies re-
viewed according to the several indices.
From the material reviewed in this chap-
ter, a selection has been made of data from
those studies which furnish the best quan-
titative information that we have available
at the present time. Levels are given in the
measurement system used in the original
observations, since conversion from one
method to another is not recommended. At-
tention should be given to the difference be-
tween British "smoke" and American "sus-
pended particulate" measurements. Both are
given in micrograms per cubic meter of air,
but they are not identical. Limited data in-
dicate that the American values may be
higher in the same situation. In making
use of these data, attention must also be
given to the averaging time which was em-
ployed in the original observation. Long-
term averages are, of necessity, considerably
lower than selected high daily means in the
same locations.
British studies of acute episodes of in-
creased pollution show excess deaths occur-
ring at smoke levels from 750 /ug/m3 to 2,000
fig/m3. High S03 levels are, of course, con-
currently present. The excesses of mortal-
ity are always accompanied by a very large
increase in illness, mainly exacerbations of
chronic conditions. Similar but less spec-
tacular episodes in New York City have been
associated with smoke shade levels of 5-6
coh units.
Lawther, in reviewing a long series of ob-
servations on the condition of bronchitic
patients, estimated that they tended to be-
come worse when daily levels of smoke ex-
ceeded 300 p.g/m3 with S02 over 600 /*g/m3.
Angel et al. made somewhat similar obser-
vations with smoke above 400 /jg/m3 and
S02 over 460 jug/m3.
Winkelstein found in Buffalo that in-
creases in the mortality rate were signifi-
cantly linked to higher levels of suspended
particulate pollution. His studies showed
that mortality from all causes, from chronic
respiratory diseases, and from gastric car-
cinoma increased from the lowest of his
five levels of pollution (less than 80 /*g/m3)
through the three higher ranges, after the
effects of socioeconomic status had been con-
sidered. Zeidberg found in Nashville sig-
nificant increases in all respiratory deaths
at soiling levels over 1.1 cohs annual aver-
age. Neither of these studies took smoking
habits into account, and the Nashville study
only partially allowed for socioeconomic
factors.
Studies of illness in relation to residence
in more- and less-polluted areas contribute
additional information. Fletcher et al. noted
a proportional decline in the production of
morning sputum in chronic bronchitics in
West London from 1961 to 1966 as smoke
pollution in their residence areas declined
from 140 jug/m3 annual mean. Douglas and
Waller found an increase in frequency and
severity of lower respiratory illness at smoke
and S02 levels over 130 /tg/m3 annual aver-
age. The Sheffield study by Lunn et al.2
shows similar differences occurring with
some morbidity measures between about
100 ng/m3 and 200 ^g/m3 of smoke, and for
others between 200 /ig/m3 and 300 /*g/m8
annual average.
A study of British workmen found in-
creased respiratory illness absence in areas
with smoke levels in excess of 200 /*g/m3.
Physiologic studies of lung function have
also been made in both adults and children.
On the basis of present limited knowledge
it appears that the alterations found may be
both temporary and permanent. The obser-
vations now available relate to long-term
residence in a given area. The Sheffield
170
-------
Table 11-6.—SUMMARY TABLE OF EPIDEMIOLOGICAL STUDIES
1
"3™
•a a
a>.S
T3 *>
Is
Health Index §
VI
A. Acute episodes — Mortality:
1. London, winter
1958-59.
London, winter
1958-59.
London, winter
1958-59.
2. London, fog
episodes,
1954, 1955,
1956, 1957.
London, fog
episode 1962.
3. New York,
November,
1953.
4. New York,
De.cember,
1962.
New York,
December,
1962.
5. New York,
January,
1963.
6. Detroit, >200
September, 3 days
1952.
7. Osaka, 1000
December, (sic)
1962.
B. Acute episodes — Morbidity:
1. New York, . . .
November,
1953.
2. New York,
November,
1966.
C. Long-term air pollution — Day
1. London winters, _ _ .
1958-59,
1959-60.
c
~~? ®
<5 2 M^3 o!
« 1 S3?
£S • '2 > m ff
«pq g £ ca v g
3^. £~| £*§
.3 g " g^ gl s
i"S ~1 r§-s
M"c •-§•» *"8 S
* ^"w O-^ "g
| 0 M g " Findings
M U 42
rise of 200 . _ - rise of 75 Correlation of daily mortality (all
causes) and daily bronchitis
mortality with B.S.M. Signifi-
cant positive association of SO2
and deaths.
1000 _ 715 Increase in mortality (all causes)
750 715 Re-analysis of data of reference 4
2000 1200 Bronchitis death rate increased,
other causes rise also.
2000 1145 Death rates of elderly rose;
greater proportionate rise in
bronchitis deaths.
[51 2460 Excess deaths all age groups;
lag effect noted.
No excess deaths
[6] 2145 Excess deaths in 45-64 age group
and over 65 age group.
[6] 1715 Peak in death rate superimposed
on high deaths due to influenza.
2860 (max) Excess infant mortality and
cancer mortality.
_ - _ . 285 Sixty excess deaths
[3] 715 Increased upper respiratory
infection and cardiac disease
morbidity.
Increased emergency visits for
bronchitis and asthma; analysis
complicated by Thanksgiving
holiday.
to day variations in mortality and morbidity:
>500 >400 Increases in mortality and
morbidity appear positively
associated with fluctuations in
air pollution.
Reference
11
12
13
8,9
10
14
15
16
16
19
20
21
22
12
17]
-------
Table 11-6 (continued).—SUMMARY TABLE OF EPIDEMIOLOGICAL STUDIES
+J
la
rrt bfl
P. *
•rt x G
a g 3
•tjs
bo
sis
^
-------
Table 11-6 (continued).—SUMMARY TABLE OF EPIDEMIOLOGICAL STUDIES
-S
a
w
o
g
si
>*e
a
fe
Findings ^
K
6. Nashville,
Tenn.,
1940-60.
30
E. Long-term air pollution—Geographic variations in morbidity:
1. Genoa, Italy
Air pollution levels did not re-
late to deaths due to cancer of
bronchus, trachea or lung.
Mortality effects also seen in
area with 80 Mg/m3 to 100
Mg/m3.
'High" pollution related to in-
creased respiratory disease
mortality. Lung and bronchial
cancer, bronchitis, and
emphysema mortality not
clearly related.
2. Japan n.a.
3. U.K.-U.S. U.S. U.K.
Comparison. 100 200
n.a.
U.S. 12-30
U.K. 60-300
(Levels not directly comparable)
4. U.K.
In-
adeq.
5. Canada,
4 cities.
6. Berlin,
N. Hamp-
shire, Chilli-
wack, B.C.
7. Nashville,
Tenn.
F. Long-term air pollution—Incapacity for work:
1. U.S 100- _.
190
[11.6] [SOsl.3]
(lyr-
av.)
Inadeq.
34.9
[SOsO.4]
[SO30.05]
38,39
41
42
43
44
45
Frequency of bronchitis signifi-
cantly associated with SO2, not
with suspended matter of
dustfall.
Gradient of respiratory disease
morbidity from industrial to
rural sites.
Increase of smoke concentration
from 100 /jg/m3 to 200 jug/m3
and equivalent SOa increase
leads to higher risk to older
men of poorer lung function and
increased chronic respiratory
disease.
Differences in area respiratory
morbidities attributed by authors
to difference in air pollution.
Increased severe bronchitis, poor
lung function performance in
"dirty" cities versus "clean"
cities.
No observable differences 46-48
Cardiovascular disease directly 49
correlated with aerometric data.
No increased respiratory disease
morbidity.
No correlation of absence in 50
excess of 7 days with sus-
pended particles. Significant
correlation of absence with
"suspended participate
sulfate."
173
-------
Table 11-6 (continued).—SUMMARY TABLE OF EPIDEMIOLOGICAL STUDIES
OJ
0) fl
>H +i £3
||3
o
.
|§
§
&'•§&
i£s
ra 1000 (2
consecu-
tive days)
3. Greater Lon- 100-200
don, U.K.
400
4. New York,
N.Y.
Studies of children:
G. 1. U.K., >130
1946-61.
2. Sheffield, U.K., 100
1963-65.
3. Ferrara district, n.a.
Italy,
1959-64.
4. Japan
150-250
400
[2.7] 540 (7 yr.
(7 yr. mean).
mean).
>130
60
>120
n.a.
[S030.02]
5. Japan.
n.a.
6. Irkutsk,
U.S.S.R.,
time period
not definite.
H. Studies of pulmonary function:
1. U.K.-U.S. -
Comparison.
n.a.
2. Japan.
Bronchitis caused absence greater 34
than expected by factor of 2 in
four of five episodes.
Lowest bronchitis inception rates__ 51
Highest bronchitis inception rates.
Significant correlation of bron-
chitis incapacity with smoke
and SO 2 for all age groups, and
men 35-54 and 55-59.
No strong relation between 52
respiratory illness absence and
COH or SO 2.
Increased frequency and severity 54
of lower respiratory diseases in
school children.
Increased association of "res- 56
piratory infections" for school
children age 5-6.
No correlation of onset of acute 57
respiratory illness to changing
pollutant levels except in poor-
est socioeconomic area.
Total vital capacity of children in 42
polluted and nonpolluted areas
the same. Fluctuations in mean
peak flow rates larger for chil-
dren in polluted areas than in
less polluted areas.
Peak flow rates decreased more in 20
winter for children in polluted
areas than in less polluted areas.
Possible relation of respiratory 58
disease and residence in area of
pollution.
FEVi.o performance of U.K. 43
workers decreased compared to
U.S. counterparts.
Total vital capacity of children in 42
polluted and nonpolluted areas
the same. Fluctuations in mean
peak flow rates larger for chil-
dren in polluted areas than in
less polluted areas.
174
-------
Table 11-6 (continued).—SUMMARY TABLE OF EPIDEMIOLOGICAL STUDIES
o,
•a
Health Index
si!
P
w
o
o
ei! a> g
>» rto
Findings
3. Japan Peak flow rates decreased more in 20
winter for children in polluted
areas than in less polluted areas.
4. Pennsylvania, Possible relation of dustf all and 59
2 com- SO 2 differences in average and
munities. specific airway resistance of
subjects in the two com-
munities.
5. Sheffield, U.K. 100 275 Reduced FEVo.w and FVC in 56
areas of highest pollution.
Possible persistence of respira-
tory function deterioration
related to residence in area of
high pollution.
I. Studies of panels of bronchitic patients:
1. London, 300 >600 Acute worsening of symptoms in 60
November, bronchitis patients.
1955-May,
1956.
2. U.K., October, 400 460 Possible increase in respiratory 62
1962-April, disease attack rates.
1963.
3. Rotterdam, n.a. n.a. No indication of residence effect 63
Netherlands. on bronchitis symptoms.
4. London 140 Mg/m3 200 itg/m3 Decrease in morning sputum 64
declining declining volume with decreasing air
to to pollution levels in bronchitis
60 /ig/m3. 160 jug/m3. patients under observation dur-
ing 6 years.
study shows reduced pulmonary function in
the children in the most polluted area, i.e.,
where smoke concentration is above 300
/ig/m3. Studies in Japan show a decrease
in pulmonary function in school children liv-
ing in areas of high dustfall as compared
with those living in low dustfall areas. In
Osaka the dustfall levels were 6.5 gm/m2-
month and 13.3 gm/m2-month.
The analyses of the numerous epidemio-
logical studies discussed clearly indicate an
association between air pollution, as meas-
ured by particulate matter accompanied by
sulfur dioxide, and health effects of varying
severity. This association is most firm for
the short-term air pollution episodes.
There are probably no communities which
do not contain a reservoir of individuals with
impaired health who are prime targets for
the effects of elevated levels of particulate
matter and sulfur oxides. However, to show
small changes in deaths associated with co-
incident higher levels of air pollutants re-
quires extremely large populations. In small
cities, these small changes cannot be de-
tected statistically.
The epidemiologic studies concerned with
increased mortality also show increased mor-
175
-------
bidity. Again, increases in morbidity as
measured, for example, by increases in hos-
pital admissions or emergency clinic visits,
are most easily detected in major urban
areas.
It is believed that, for the large urban
communities which are routinely exposed
to relatively high levels of pollution, sound
statistical analysis can detect with confidence
the small changes in daily mortality which
are associated with functions in pollution
concentrations. Unfortunately, only limited
analysis has thus far been made, and this
has been attempted only in London and in
New York.
The association between longer-term com-
munity exposures to particulate matter for
respiratory disease incidence and prevalence
rates is conservatively believed to be inter-
mediate in its reliability. Because of the re-
enforcing nature of the studies conducted
to date, the conclusions to be drawn from
this type of study can be characterized as
probable.
The association between long-term resi-
dence in a polluted area and chronic disease
morbidity and mortality is somewhat more
conjectural. However, in the absence of
other explanations, the findings of increased
morbidity and of increased death rates for
selected causes, independent of economic
status, must still be considered consequen-
tial.
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41. Petrilli, F. L., Agnese, G., and Kanitz, S. "Epi-
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42. Toyama, T. "Air Pollution and its Health Ef-
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43. Holland, W. W., Reid, D. D., Seltser, R., and
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44. Holland, W. W. and Reid, D. D. "The Urban
Factor in Chronic Bronchitis." Lancet 1:445-
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45. Bates, D. V. "Air Pollution and Chronic Bron-
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46. Ferris, B. G., Jr. and Anderson, D. O. "The
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R. "Levels of Air Pollution and Respiratory
Disease in Berlin, New Hampshire." Am. Rev.
Respirat. Diseases 90:877-887, 1964.
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Arch. Environ. Health 10:307-311, 1965.
49. Zeidburg, L. D., Prindle, R. A., and Landau,
E. "The Nashville Air Pollution Study. III.
Morbidity in Relation to Air Pollution." Am. J.
Public Health 54:85-97, 1964.
50. Dohan, F. C. "Air Pollutants and Incidence of
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3:387-395, Oct. 1961.
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Insurance, London, England. Her Majesty's
Stationery Office, London, England. 1965.
52. Verma, M. P., Schilling, F. J., and Becker, W.
H. "Epidemiological Study of Illness Absences
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in Relation to Air Pollution." Arch. Environ.
Health. 18:536-543, 1969.
53. Reid, D. D. "Air Pollution and Respiratory Dis-
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54. Douglas, J. W. B. and Waller, R. E. "Air Pol-
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55. Holland, W. W. and Elliott, A. "Cigarette Smok-
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56. Lunn, J. E., Knowelden, J., and Handyside,
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field Infant School Children." Brit. J. Prevent.
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"The Immediate Effects of Air Pollution on the
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Different Air Pollution Levels." Am. J. Public
Health 53:200-218, 1963.
60. Lawther, P. J. "Climate, Air Pollution, and
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262-264, 1958.
61. Waller, R. E. and Lawther, P. J. "Some Obser-
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178
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Chapter 12
SUMMARY AND CONCLUSIONS
-------
Table of Contents
Page
A. SUMMARY .... .181
1. General 181
2. Effects on Health . . .182
3. Effects on Climate Near the Ground ... 184
4. Effects on Visibility . . .184
5. Effects on Materials . . 185
6. Economic Effects of Atmospheric Particulate Matter . . 186
7. Effects on Vegetation . ... 186
8. Effects on Public Concern . . . 187
9. Suspended Particles as a Source of Odor . . . 187
B. CONCLUSIONS . 187
1. Effects on Health ... .... 188
2. Effects on Direct Sunlight .... 189
3. Effects on Visibility . . 189
4. Effects on Materials . . . 189
5. Effects on Public Concern .189
C. RESUME . 189
180
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Chapter 12
SUMMARY AND CONCLUSIONS
A. SUMMARY
1. General
The particulate matter commonly found
dispersed in the atmosphere is composed of a
large variety of substances. Some of these—
fluorides, beryllium, lead, asbestos, for ex-
ample—are known to be directly toxic, al-
though not necessarily at levels routinely
found in the atmosphere today. The evidence
suggests that there may very well be others
whose toxic effects have not yet been recog-
nized. To evaluate fully the effects on health
and welfare of the presence of each of these
substances in the air requires that they be
given individual attention, or attention as
classes of similar substances. Such evalua-
tions will be made in separate documents.
This document considers the effects on
man and his environment of undifferentiated
particulate matter. These effects oftentimes
are produced by a combination of particulate
and gaseous pollutants, the contributions of
which are difficult to distinguish. Moreover,
laboratory studies have shown that a com-
bination of particulates and gases may pro-
duce an effect that is greater than the sum
of the effects caused by these pollutants in-
dividually.
Particles in the atmosphere, whatever
their individual characteristics, exhibit a
number of similar properties, which are for
the most part dependent on the particle size.
Most of the available studies on the effects
of particulate air pollution, however, do not
specify particle size, and this document is
limited to treating particulate matter as a
whole, and to considering the effects which
are generally associated with the presence
of particles in the air.
Particulate air pollution, as used in this
document, refers to any matter dispersed in
the air, whether solid or liquid, in which the
individual particles are larger than small
molecules but smaller in diameter than 500/t.
(One ju, in one millionth of a meter.) Particles
in this size range stay in the air anywhere
from a few seconds to several months.
Generally speaking, particles smaller than
1 fi in diameter originate in the atmosphere
principally through condensation and com-
bustion, while larger particles, with the ex-
ception of rain, snow, hail, and sleet, arise
principally from comminution. Particles
larger than 10 /u, in diameter result from
mechanical processes such as wind erosion,
grinding and spraying, and the pulverizing
of materials by vehicles and pedestrians.
Particles between 1 /* and 10 /*. in diameter
usually include local soil, process dusts and
combustion products from local industries,
and, for maritime locations, sea salt. Com-
bustion products and photochemical aerosols
make up a large fraction of the particles in
the range 0.1 # to 1 /i in diameter, and,
although particles below 0.1 //, in diameter
have not been extensively identified chem-
ically, the typical urban increase over natural
levels of particles in this size range seems to
be entirely due to combustion.
Particles of a size less than 0.1 /* in di-
ameter are characterized by random motions
produced by collisions with gas molecules.
They are highly concentrated, move rapidly,
collide frequently, and through sorption and
nucleation of gas molecules and adhesion
with other particles grow larger quickly.
Particles larger than 1 /x have significant set-
tling velocities, and their motions may devi-
ate significantly from the motion of the air.
Measurements of dustfall are commonly
used to indicate the mass concentration of
181
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the settleable portion of participate air pollu-
tion. Typical values for cities are 10 to 100
tons/mile2-month; as high as 2,000 tons/
mile2-month have been measured in the vicin-
ity of especially offensive sources. Levels of
dustfall have apparently declined in some
American cities, and dustfall measurements
are probably not useful as an index of over-
all particulate air pollution. However, dust-
fall itself constitutes a nuisance, and its
measurement can be used as an index of the
dirtiness of air pollution.
Several methods are available for measur-
ing suspended particulate concentrations.
The most commonly used device is the high-
volume sampler, which consists essentially
of a blower and a filter, and which is usually
operated in a standard shelter to collect a
24-hour sample. The sample is weighed to
determine concentration, and is usually ana-
lyzed chemically. The hi-vol is considered a
reliable instrument for measuring the weight
of total particulate matter. Chemical analysis
of the hi-vol sample, however, may be limit-
ed: the filter material may contaminate the
sample; different substances in the sample
may react with each other; and losses may
occur through volatilization of material.
Tape samplers, which collect suspended par-
ticulate matter on filters and analyze the
sample optically, are also in common use.
While these samplers are inexpensive and
rugged, they yield data which cannot always
be easily interpreted in terms of particulate
mass concentration. Other techniques avail-,
able for measuring particulate pollution in-
clude optical systems, which provide an indi-
cation of concentration without requiring
that a sample be taken.
The averaging time used for measuring
suspended particulates is not as significant a
factor as it is for gaseous pollutants. The
basic unit of time is 24 hours. Values taken
over this period may be combined into week-
ly, monthly, seasonal, and annual means as
required. The relationships between daily
and other longer time periods in the United
States is known with some degree of precis-
ion, as data exist for a 10-year period.
Most of the data on mass concentrations
of suspended particulates come from the
National Air Surveillance Networks,
(NASN), which uses the high-volume samp-
ler. NASN currently operates some 200
urban and 300 nonurban stations, and is
supplemented by State and local networks.
From the NASN data, the annual geometric
mean concentrations of suspended particu-
late matter in urban areas range from 60
/*g/m3 to about 200 /*g/m3. The maximum 24-
hour average concentration is about three
times the annual mean, but values of seven
times the annual mean do occur. Mean par-
ticulate concentrations correlate, in general,
with urban population class, but the range
of concentrations for any class is broad, and
many smaller communities have higher con-
centrations than larger ones. For nonurban
areas the annual geometric mean is typically
between 10 jug/m3 and 60
2. Effects on Health
For the most part, the effects of particu-
late air pollution on health are related to
injury to the surfaces of the respiratory sys-
tem. Such injury may be permanent or tem-
porary. It may be confined to the surface, or
it may extend beyond, sometimes producing
functional or other alterations. Particulate
material in the respiratory tract may pro-
duce injury itself, or it may act in conjunc-
tion with gases, altering their sites or their
modes of action.
Laboratory studies of man and other ani-
mals show clearly that the deposition, clear-
ance, and retention of inhaled particles is a
very complex process, which is only begin-
ning to be understood. Particles cleared from
the respiratory tract by transfer to the
lymph, blood, or gastrointestinal tract may
exert effects elsewhere. Few studies have in-
vestigated the possibility of eye injury by
particles in the air; only transient eye irrita-
tion from large dust particles presently is
known to be a problem.
The available data from laboratory
experiments do not provide suitable quantita-
tive relationships for establishing air quality
criteria for particulates. The constancy of
population exposure, the constancy of tem-
perature and humidity, the use of young,
normal, healthy animals, and the primary
focus on short-term exposures in many lab-
oratory studies make extrapolation from
182
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these studies of limited value for the general
population, and singularly risky for special
risk groups within the population. These
studies do, however, provide valuable inform-
ation on some of the bioenvironmental rela-
tionships that may be involved in the effects
of particulate air pollution on health. The
data they provide on synergistic effects show
very clearly that information derived from
single-substance exposures should be applied
to ambient air situations only with great
caution.
Epidemiological studies do not have the
precision of laboratory studies, but they have
the advantage of being carried out under
ambient air conditions. In most epidemiologi-
cal studies, indices of air pollution level are
obtained by measuring selected pollutants,
most commonly particulates and sulfur com-
pounds. To use these same studies to estab-
lish criteria for individual pollutants is justi-
fied by the experimental data on interaction
of pollutants. However, in reviewing the re-
sults of epidemiological investigations it
should always be remembered that the speci-
fic pollutant under discussion is being used
as an index of pollution, not as a physico-
chemical entity.
In epidemiologcial studies consistency of
results at different times and places is im-
portant in determining the significance of
observations. However, while polluted air has
many similarities from place to place and
from time to time, it is not identical in all
communities or at all times, and complete
consistency between epidemiological studies
should not be expected. There are not a large
number of suitable epidemiological studies
available at present, but those that are avail-
able show some consistency in the levels at
which effects were observed to occur.
Considerable data have been presented on
a number of air pollution episodes in London
and in New York City. In reviewing these
data it should be remembered that British
air pollution measurements are not entirely
comparable with American measurements.
The only published comparison indicates that
the British method of measuring particulates
tends to give somewhat lower readings than
American methods.
Excess deaths and a considerable increase
in illness have been observed in London at
smoke levels above 750 /*g/m3 and in New
York at a smokeshade index of 5-6 cohs. Sul-
fur oxides pollution levels were also high in
both cases. These unusual short-term, mas-
sive exposures result in immediately appar-
ent pathologic effects, and they represent the
upper limits of the observed dose-response
relationship between particulates and ad-
verse effects on health.
Daily averages of smoke above 300 /ig/m3
to 400 p.g/m3 have been associated with acute
worsening of chronic bronchitis patients in
England. No comparable data are available
in this country. Studies of British workmen
found that increased absences due to illness
occurred when smoke levels exceeded 200
/*g/m3.
Two recent British studies showed in-
creases in selected respiratory illness in
children to be associated with annual mean
smoke levels above 120 jug/m3. Additional
health changes were associated with higher
levels. These effects may be of substantial
significance in the natural history of chronic
bronchitis. Changes beginning in young
children may culminate in bronchitis several
decades later.
The lowest particulate levels at which
health effects appear to have occurred in this
country are reported in studies of Buffalo
and Nashville. The Buffalo study clearly
shows increased death rates from selected
causes in males and females 50 to 69 years
old at annual geometric means of 100 /tg/m3
and over. The study suggests that increased
mortality may have been associated with
residence in areas with 2-year geometric
means of 80 pg/m3 to 100 /xg/m3. The Nash-
ville study suggests increased death rates
for selected causes at levels above 1.1 cohs.
Sulfur oxides pollution was also present dur-
ing the periods studied. In neither study
were the smoking habits of the decedents
known.
Corroborating information is supplied
from Fletcher's study of West London work-
ers between the ages of 30 and 59. The data
indicate that with a decrease of smoke pollu-
tion (yearly mean) from 140 /xg/m3 to 60
/xg/m3, there was an associated decrease in
mean sputum volume. Fletcher noted that
183
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there may have been changes in the tar com-
position of cigarettes during the period stud-
ied; such a change could affect the findings.
This study provides one of the rare oppor-
tunities to examine the apparent improve-
ment in health that followed an improvement
in the quality of the air.
3. Effects on Climate Near the Ground
Particles suspended in the air scatter and
absorb sunlight, reducing the amount of solar
energy reaching the earth, producing hazes,
and reducing visibility. Suspended particu-
late matter plays a significant role in bring-
ing about precipitation, and there is some
evidence that rainfall in cities has increased
as the cities have developed industrially.
Suspended particulate matter, in the con-
centrations routinely found in urban areas,
considerably reduces the transmission of
solar radiation to the ground, creating an
increased demand for artificial light. The
effect is more pronounced in the winter than
in the summer, when particulate pollution
loadings are higher, and sunlight must pene-
trate more air to reach the ground. For
similar reasons the effect is also more pro-
nounced during the workweek than on week-
ends, during industrial booms, and in higher
latitudes. For a typical urban area in the
United States, with a geometric mean annual
particulate concentration of roughly 100
/ug/m3, the total sunlight, including that re-
ceived directly from the sun and that reflect-
ed by the sky, is reduced five percent for
every doubling of particle concentration. The
reduction is most pronounced on ultraviolet
radiation.
For urban areas in the middle and high
latitudes, particulate air pollution may re-
duce direct sunlight by as much as one-third
in the summer and as much as two-thirds in
the winter. This effect may have implica-
tions for the delicate heat balance of the
earth's atmospheric system. In spite of an
increase in the carbon dioxide content of the
atmosphere over the past several decades,
which would presumably bring about an
increase in atmospheric temperature, mean
worldwide temperatures have been decreas-
ing since the 1940's. Increased reflection of
solar radiation back to outer space, brought
about by increased concentrations of particu-
late air pollution, may be more than cancel-
ling out the climatic effect of the increased
carbon dioxide. That worldwide particulate
air pollution has been increasing is evidenced
by the fact that in the United States and in
other countries, turbidity, a phenomenon
produced by the back-scattering of direct
sunlight by particles in the air, has increased
significantly over the last several decades.
4. Effects on Visibility
Particles suspended in the air reduce vis-
ibility, or visual range, by scattering and
absorbing light coming from both an object
and its background, thereby reducing the
contrast between them. Moreover, suspended
particles scatter light into the line of sight,
illuminating the air between, to further de-
grade the contrast between an object and its
background.
The scattering of light into and out of the
line of viewing by particles' in the narrow
range of 0.1 p. to 1 p. in radius has the greatest
effect on visibility. Certain characteristics of
behavior of these particles make it possible
to formulate a useful approximate relation-
ship between visual range and concentrations
of particulate matter:
AxlO3
LT—-
G'
where G' = particle concentration
Lv = equivalent visual range, and
A = 1.2.' for LT expressed in kilome-
O.o
ters and 0.75
for Lv expressed in miles
1.5
0.38
The value 1.2 for A is the mid-range value
empirically obtained from observations in a
variety of air pollution situations. The data
indicate that the range 0.6 to 2.4 covers
virtually all cases studied. The relationship
does not hold at relative humidities above 70
percent, nor does it apply to fresh plumes
from stacks, and it may not hold for the
products of photochemical reactions. A com-
panion document, Air Quality Criteria For
Sulfur Oxides, discusses a relationship be-
tween levels of sulfur dioxide and visual
range at various relative humidities.
184
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Within the limitations prescribed, the re-
lationship provides a useful means of esti-
mating approximate visual range from par-
ticulate concentrations. In addition to aesthe-
tic degradation of the environment, reduced
visibility has serious implications for safe
operation of aircraft and motor vehicles. At
a visual range of less than 5 miles, opera-
tions are slowed at airports because of the
need to maintain larger distances between
aircraft. Federal Aviation Administration
restrictions on aircraft operations become
increasingly severe as the visual range de-
creases below 5 miles. Using the upper and
lower bounds of the relationship described
above, visibility could be 5 miles at a par-
ticulate loading as high as 300 /xg/m3 or as
low as 75 jug/m3. However, on the average,
visibility can be expected to be reduced to
approximately 5 miles at a particulate con-
centration of 150 jug/m3. At a level of 100
/ig/m3, visibility is reduced to 73/2 miles. This
limited distance, however, may be related to
particulate concentrations as low as 50 /ng/m3
and as high as 200 /ug/m3.
5. Effects on Materials
Particulate air pollution causes a wide
range of damage to materials. Particulate
matter may chemically attack materials
through its own instrinsic corrosivity, or
through the corrosivity of substances absorb-
ed or adsorbed on it. Merely by soiling ma-
terials, and thereby causing their more fre-
quent cleaning, particulates can accelerate
deterioration.
Laboratory and field studies underscore
the importance of the combination of par-
ticulate matter and corrosive gases in the
deterioration of materials. On the basis of
present knowledge, it is difficult to evaluate
precisely the relative contribution of each of
the two classes of pollution; however, some
general conclusions may be drawn.
Particulates play a role in the corrosion of
metals. In laboratory studies, steel test
panels that were dusted with a number of,
active hygroscopic particles commonly found
in the atmosphere corroded even in clean
air. Corrosion rates were low below a rela-
tive humidity of 70 percent; they increased
at relative humidities above 70 percent; and
they greatly increased when traces of sulfur
dioxide were added to the laboratory air.
It is apparent that the accelerated corro-
sion rates of various metals in urban and
industrial atmospheres are largely the re-
sult of relatively higher levels of particulate
pollution and sulfur oxides pollution. High
humidity and temperature also play an im-
portant synergistic part in this corrosion re-
action. Studies show increased corrosion
rates in industrial areas where air pollution
levels, including sulfur oxides and particu-
lates, are higher. Further, corrosion rates
are higher during the fall and winter sea-
sons when particulate and sulfur oxides pol-
lution is more severe, due to a greater con-
sumption of fuel for heating.
Steel samples corroded 3.1 times faster in
the spring of the year in New York City,
where annual particulate concentrations
average 176 ^g/m3, than did similar samples
in State College, Pennsylvania, where the
average concentrations were estimated to
range from 60 /tg/m3 to 65 /ig/m3. In the
fall of the year, when particulate and sulfur
oxide concentrations in New York were con-
siderably higher than in the spring, the steel
samples in New York corroded six times
faster than the samples at State College.
Similar findings were reported for zinc
samples. Moisture may have contributed to
the corrosion.
In Chicago and St. Louis, steel panels were
exposed at a number" of sites, and measure-
ments taken of corrosion rates and of levels
of sulfur dioxide and particulates. In St.
Louis, except for one exceptionally polluted
site, corrosion losses correlated well with sul-
fur dioxide levels, averaging 30 percent to
80 percent higher than losses measured in
nonurban locations. Sulfation rates in St.
Louis, measured by lead peroxide candle, also
correlated well with weight loss due to
corrosion. Measurements of dustfall in St.
Louis, however, did not correlate significant-
ly with corrosion rates. Over a 12-month
period in Chicago, the corrosion rate at the
most corrosive site (mean S02 level of 0.12
ppm) was about 50 percent higher than at
the least corrosive site (mean S02 level of
0.03 ppm). Although suspended particulate
185
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levels measured in Chicago with high-volume
samplers also correlated with corrosion rates,
a covariance analysis indicated that sulfur
dioxide concentrations were the dominant
influence on corrosion. Based on these data,
it appears that considerable corrosion may
take place (i.e., from 11 percent to 17 per-
cent weight loss in steel panels) at annual
average sulfur dioxide concentrations in the
range of 0.03 ppm to 0.12 ppm, and although
high particulate levels tend to accompany
high sulfur dioxide levels, the sulfur dioxide
concentration appears to have the more
important influence.
Particulate air pollution damages electri-
cal equipment of all kinds. Oily or tarry par-
ticles, commonly found in urban and indus-
trial areas, contribute to the corrosion and
failure of electrical contacts and connectors.
Dusts can interfere with contact closure, and
can abrade contact surfaces. Hygroscopic
dusts will absorb water and form thin elec-
trolytic films which are corrosive.
Particulates soil and damage buildings,
statuary, and other surfaces. The effects are
especially severe in urban areas where large
quantities of coal and sulfur-bearing fuel
oils are burned. Particles may act as reser-
voirs of acids, and thereby sustain a chemical
attack that will deteriorate even the more
resistant kinds of masonary. Particles stick
to surfaces, forming a film of tarry soot and
grit which oftentimes is not washed away by
rain. Considerable money and effort have
been spent in many cities to sandblast the
sooty layers that accumulate on buildings.
Water-soluble salts, commonly found in ur-
ban atmospheres, can blister paint. Other
particles may settle on newly painted sur-
faces, causing imperfections, thereby in-
creasing the frequency with which a surface
must be painted.
The soiling of textiles by the deposition of
dust and soot on fabric fibers not only makes
them unattractive, and thereby diminishes
their use, but results in abrasive wear of the
fabric when it is cleaned. Vegetable fibers,
such as cotton and linen, and synthetic nylons
are particularly susceptible to chemical at-
tack by acid components of airborne
particles.
6. Economic Effects of Atmospheric
Particulate Matter
It is not possible at the present stage of
knowledge to provide accurate measures of
all the costs imposed on society by particu-
late air pollution. Selected categories of
effects can be quantified; it is obvious that
these estimates represent a significant under-
statement of the total cost.
7. Effects on Vegetation
Relatively little research has been carried
out on the effects of particulate air pollution
on vegetation, and much of the work that
has been performed has dealt with specific
dusts, rather than the conglomerate mixture
normally encountered in the atmosphere.
This document reports briefly on some of
these specific particulate studies only to illus-
trate the possible mechanisms through which
particulate matter may affect vegetation.
This information is not presented for the
purpose of establishing air quality standards
on these specific pollutants.
There is considerable evidence that
cement-kiln dusts can damage plants. A
marked reduction in the growth of poplar
trees 1 mile from a cement plant was observ-
ed after cement production was more than
doubled. Plugging of stomates by the dust
may have prevented the exchange of gases
in leaf tissue that is necessary for growth
and development. Moderate damage to bean
plants occurred when the plant leaves were
dusted at the rate of 0.47 mg/cm2-day (400
tons/m2-month) for 2 days and then exposed
to natural dew. The mechanism through
which the leaves are damaged is not en-
tirely understood, but direct alkaline dam-
age to tissues beneath the crust formed by
the dust and moisture has been observed. The
deposits may also plug stomates and block
light needed for photosynthesis. Cement-
kiln dusts may change the alkalinity of soils
to benefit or harm vegetation, depending on
the species.
Dust deposits may also eliminate preda-
tors, and thereby bring on increased insect
injury to plants; they may interefere with
pollen germination; and they may make
plants more susceptible to pathogens.
186
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Fluoride dusts apparently have a difficult
time penetrating leaf tissue in physiologi-
cally active form, and they are much less dam-
aging to vegetation than is gaseous fluoride.
Soluble fluoride dusts may be absorbed by
the plant, but the amount is relatively small
compared to that which can enter the plant
in gaseous form. The evidence suggests that
there is little effect on vegetation at fluoride
particulate concentrations below 2 /*g/m3.
Concentrations of this magnitude and above
can sometimes be found in the immediate
vicinity of sources of fluoride particulate
pollution; they are rarely found in urban
atmospheres.
Ingestion of particles deposited on plants
can be harmful to animal health. Fluorosis
and arsenic poisoning have been brought on
through this medium.
Soot may clog stomates and may produce
necrotic spotting if it carries with it a soluble
toxicant, such as one with excess acidity.
Magnesium oxide deposits on soils have been
shown to reduce plant growth, while iron
oxide deposits on soils have been shown to
reduce plant growth, while iron oxide de-
posits appear to have no harmful effects, and
may be beneficial.
8. Effects on Public Concern
Several studies indicate that there is a
relationship between levels of particulate
pollution, used as an index of air pollution,
and levels of public concern over the prob-
lem. A study conducted in 1963 in the St.
Louis metropolitan region found a direct
linear relationship between the fraction of
a community's population who said air pollu-
tion was a nuisance, and the annual mean
concentration of particulate air pollution in
the community. The relationship, which was
derived from data on communities in the St.
Louis area whose annual concentrations
ranged from 50 ^g/m3 to 200 /*g/m3, was
formulated as:
y=0.3x-14
where y=population fraction (%)
concerned, and
x=annual geometric mean par-
ticle concentration
It is thought that the reaction to suspended
particulates as a nuisance probably occurs
at peak concentrations, and not necessarily
at the values representing annual means.
However, the relationship provides a useful
example of how the nuisance effect of air
pollution relates to concentrations. Approxi-
mately 10 percent of the study population'
considered air pollution a nuisance in areas
with suspended particulates at an annual
geometric mean concentration of 80 /ig/m3.
At this same level of pollution, 30 percent of
the study population was "aware of" air
pollution. In areas with 120 /^g/m3 (annual
geometric mean), 20 percent were "bothered
by" and 50 percent were "aware of" air pol-
lution; in areas with an annual geometric
mean of 160 jug/m3, one-third of the popula-
tion interviewed were "bothered by" and
three-fourths were "aware of" air pollution.
Although data from other studies do not
readily lend themselves to quantitative for-
mulation, they do, in general, support the
relationship reported by the St. Louis study.
A study of communities in the Nashville,
Tennessee, metropolitan area in 1957 found
that at least 10 percent of the population ex-
pressed concern about the nuisance of air
pollution at dustfall levels exceeding 10 tons/
mi2-month.
9. Suspended Particles as a Sources
of Odor
Particulate air pollution is not ordinarily
considered a significant source of odors.
However, there is evidence that liquid and
even solid particles of some substances may
be volatile enough to vaporize in the nasal
cavity, and produce sufficient gaseous ma-
terial to stimulate the sense of smell. Fur-
ther, particles may carry absorbed odorants
into the nasal cavity, and there transfer them
to olfactory receptors. A survey of State and
local air pollution control officials revealed
that approximately one-fourth of the most
frequently reported odors are those which
are known to be, or are suspected to be, asso-
ciated with particulate air pollution. The
sources of these odorous particles are div-
erse, including diesel and gasoline engine
exhausts, coffee-roasting operations, paint
187
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spraying, street paving, and the burning of
trash.
B. CONCLUSIONS
The conclusions which follow are derived
from a careful evaluation by the National
Air Pollution Control Administration of the
foreign and American studies cited in previ-
ous chapters of this document. They repre-
sent the Administration's best judgment of
the effects that may occur when various
levels of pollution are reached in the atmos-
phere. The data from which the conclusions
were derived, and the qualifications which
should be considered in using the data, are
identified by chapter reference in each case.
1. Effects on Health
Analyses of numerous epidemiological
studies clearly indicate an association be-
tween air pollution, as measured by particu-
late matter accompanied by sulfur dioxide,
and health effects of varying severity. This
association is most firm for the short-term
air pollution episodes.
There are probably no communities which
do not contain individuals with impaired
health who are particularly susceptible to
the adverse effects of elevated levels of par-
ticulate matter and sulfur oxides. However,
to show small changes in deaths associated
with coincident higher levels of air pollutants
requires extremely large populations. In
small cities, these changes are difficult to
detect statistically.
The epidemiologic studies concerned with
increased mortality also show increased mor-
bidity. Again, increases in morbidity as
measured, for example, by increases in hos-
pital admissions or emergency clinic visits,
are most easily demonstrated in major urban
areas.
For the large urban communities which
are routinely exposed to relatively high levels
of pollution, sound statistical analysis can
show with confidence the small changes in
daily mortality which are associated with
fluctuation in pollution concentrations. Such
analysis has thus far been attempted only
in London and in New York.
The association between longer-term com-
munity exposures to particulate matter and
respiratory disease incidence and prevalence
rates is conservatively believed to be inter-
mediate in its reliability. Because of the re-
enforcing nature of the studies conducted to
date, the conclusions to be drawn from this
type of study can be characterized as prob-
able.
The association between long-term resi-
dence in a polluted area and chronic disease
morbidity and mortality is somewhat more
conjectural. However, in the absence of other
explanations, the findings of increased mor-
bidity and of increased death rates for select-
ed causes, independent of economic status
must still be considered consequential.
Based on the above guidelines the follow-
ing conclusions are listed in order of reliabil-
ity, with the more reliable conclusions first.
Refer to Chapter 11 for cautions to be taken
in comparing British and American air qual-
ity measurement data.
a. AT CONCENTRATIONS OF 750
p,g/ms and higher for particulates on a 24-
hour average, accompanied by sulfur dioxide
concentrations of 715 jug/m3 and higher,
excess deaths and a considerable increase in
illness may occur. (British data; see Chapter
11, Section C-l)
b. A DECREASE FROM HO ^.g/m3 to 60
(annual mean) in particulate concen-
trations may be accompanied by a decrease
in mean sputum volume in industrial work-
ers. (British data; see Chapter 11, Section
C-4)
c. IF CONCENTRATIONS ABOVE 300
/j.g/m3 for particulates persist on a 24-hour
average and are accompanied by sulfur diox-
ide concentrations exceeding 630 /*g/m3 over
the same average period, chronic bronchitis
patients will likely suffer acute worsening of
symptoms. (British data; see Chapter 11,
Section C-3)
d. AT CONCENTRATIONS OVER 200
pg/m" for particulates on a 24-hour average,
accompanied by concentrations of sulfur
dioxide exceeding 250 /*g/m3 over the same
average period, increased absence of indus-
trial workers due to illness may occur. (Brit-
188
-------
ish data; see Chapter 11, Section C-5)
e. WHERE CONCENTRATIONS RANGE
FROM 100 fj.g/m3 to 130 /j.g/m3 and above for
particulates (annual mean) with sulfur di-
oxide concentrations (annual mean) great-
er than 120 jug/m3, children residing in such
areas are likely to experience increased inci-
dence of certain respiratory diseases.
f. AT CONCENTRATIONS ABOVE 100
fiff/m3 for particulates (annual geometric
mean) with sulfation levels above 30 mg/
cm2-mo., increased death rates for persons
over 50 years of age are likely. (American
data; see Chapter 11, Section C-2)
g. WHERE CONCENTRATIONS RANGE
FROM 80 /j-g/m3 to 100 /j.g/ms for particu-
lates (annual geometric mean) with sulfa-
tion levels of about 30 mg/cm2-mo., increased
death rates for persons over 50 years of age
may occur. (American data; see Chapter 11,
Section C-2)
2. Effects on Direct Sunlight
AT CONCENTRATIONS RANGING
FROM 100 p.g/m3 to 150 p.g/m3 for particu-
lates, where large smoke turbidity factors
persist, in middle and high latitudes direct
sunlight is reduced up to one-third in sum-
mer and two-thirds in winter. (American
data; see Chapter 2, Section C-2)
3. Effects on Visibility
AT CONCENTRATIONS OF ABOUT
150 ii.g/ms for particulates, where the pre-
dominant particle size ranges from 0.2 /x to
1.0 /i and relative humidity is less than 70
percent, visibility is reduced to as low as 5
miles. (American data; see Chapter 3, Sec-
tion E-4)
4. Effects on Materials
AT CONCENTRATIONS RANGING
FROM 60 /4T/m3 (annual geometric mean),
to 180 ing/ms for particulars (annual geo-
metric mean), in the presence of sulfur diox-
ide and moisture, corrosion of steel and zinc
panels occurs at an accelerated rate. (Amer-
ican data; see Chapter 4, Section B)
5. Effects on Public Concern
AT CONCENTRATIONS OF APPROXI-
MATELY 70 /j.g/m3 for particulates (annual
geometric mean), in the presence-of other
pollutants, public awareness and/or concern
for air pollution may become evident and in-
crease proportionately up to and above con-
centrations of 200 ng/m* for particulates.
(See Chapter 7, Section B-l)
C. RESUME
In addition to health considerations, the
economic and aesthetic benefits to. be obtain-
ed from low ambient concentrations of par-
ticulate matter as related to visibility, soiling,
corrosion, and other effects should be con-
sidered by organizations responsible for
promulgating ambient air quality standards.
Under the conditions prevailing in areas
where the studies were conducted, adverse
health effects were noted when the annual
geometric mean level of particulate matter
exceeded 80 jug/m3. Visibility reduction to
about 5 miles was observed at 150 jug/m3, and
adverse effects on materials were observed at
an annual mean exceeding 60 Mg/m3. It is
reasonable and prudent to conclude that, when
promulgating ambient air quality standards,
consideration should be given to require-
ments for margins of safety which take into
account long-term effects on health and
materials occurring below the above levels.
189
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APPENDICES
-------
area of the filter stain, cm2
APPENDIX A—SYMBOLS
b
B
B0
Bz
turbidity coefficient (empirical), A = 0.5^
particle concentration in the air, |Ug/m3
turbidity coefficient, measured on the
ground
turbidity coefficient, measured at height
z above the ground
light intensity, usually in ergs/cm2/sec
0 initial or incident light intensity
T equivalent visual range, or visibility, but
calculated on basis of a constant scat-
tering coefficient, b, along the line of
sight
p
probability
P(A)
solar transmission factor for atmos-
phere aerosols; it is a function of A
Q
particle mass concentration in the air,
usually in /j.g/m3
scattering cross-section, cm2/particle
derived surface particle concentration,
V
b
transmissivity, I/I0
volume of air sampled, m3
extinction coefficient, m-1(=b
+b +b +b )
abs gas Rayleigh scat
m
x
abs aerosol
abs aerosol
extinction coefficient due to absorption
by aerosol particles
abs gas
extinction coefficient due to absorption
by gas such as N02
Rayleigh
extinction coefficient due to scatter by
gas molecules
scat
extinction coefficient due to scatter by
aerosols
diameter of a spherical particle, cm
Napierian log base ( = 2.7182818)
acceleration of gravity, cm/sec2
index of refraction
correlation coefficient
settling velocity of a particle, cm/sec
distance, m or cm
height above ground, meters
light scattering coefficient (empirical)
relates b to A
turbidity coefficient for A = ly«.
viscosity of air, or other gas, poises
wavelength of light Angstroms, microns,
or nanometers
probability function, usually expressed
asx2 ("Chi square")
192
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APPENDIX B—ABBREVIATIONS
A Angstrom, lA = l(h8 cm m3
BTPS body temperature, pressure, mg
saturated rni
cm centimeter, 1cm =10 2m mi2
cm2 square centimeter min
cm3 cubic centimeter ml
CMD count median diameter MMD
coh coefficient of haze mo
DMBA 10-dimethyl-l, 2 benzanthracene mu
FEV forced expiratory volume /j.
FVC forced vital capacity /ug
g mass, grams ppm
hr hour RUDS
1 liter sec
m length, meter yr
cubic meter
milligram
mile
square mile
minute
milliliter
mass median diameter
month
millimicron, lm/x=0.001/*
micron, Ip. = ICHcm = 10-6m = 104A
microgram
parts per million
reflectance unit of dirt shade
second
year
193
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To convert —
mg/m3
mg/100 m3
APPENDIX C—CONVERSION FACTORS
To—
/tg/1000 m3
,ug SO2/m3
(0°C, 760 mm Hg)
ppm S02 (vol)
tons/mi2-mo
tons/mi2-mo
tons/mi2-mo
tons/mi2-mo
mg/cm2-mo
g/m2-day
/tor /*m
M
A
A*
bbl
1
ft3
ml
m
Ib
/xg/m3
ppm S02 (vol)
S0a jig/m3 (0° C, 760 mm Hg)
mg/cm2-mo
g/m2-day
metric tons/km2-mo
tons/mi2-mo
tons/mi2-mo
m
A
cm
cm
gal.
ft3
1
in3
ft
g
Multiply by-
1000
10
35.314
3.5 x 10-*
2860
3.5 x 10-2
1.07 XlO-2
3.5 xlO-1
3.5 XlO5
28.5
85.5
10-6
10*
10-8
55
0.0353
28.32
6.1X10-2
3.28
453.6
194
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APPENDIX D—GLOSSARY
Acid, free—an acid which is unneutralized
by other compounds
Acid, stearic—the most common fatty acid
occurring in natural animal and vegetable
fats, almost completely colorless and odor-
less
Acrolein—a toxic colorless mobile liquid al-
dehyde with an acrid odor
Adenocarcinoma—a malignant tumor in
which the cells are arranged in the form
of glands or gland-like structures
Adenoma—an epithelial tumor, usually be-
nign, with a gland-like structure
Adhesion—the attraction of two unlike sub-
stances
Adsorption—the phenomenon by which gases
are attracted, concentrated, and retained
at a boundary surface
Aerodynamics—a phase of the mechanics of
fluids, its study being limited to the re-
actions caused by relative motion between
fluid and solid, the fluid being limited to
air in most cases but occasionally broad-
ened to include any gas
Aerosol—a cloud of solid particles and/or
liquid droplets smaller than 10(V in di-
ameter, suspended in a gas
Aerosol, bidisperse—an aerosol in which all
the suspended particles tend to be of two
sizes (diameter)
Aerosol, monodisperse—an aerosol in which
all the suspended particles are of nearly
equal size (diameter)
Air, residual—the air that stays in the lungs
after forceful expiration
Air, tidal—the air that is carried to and
from the lungs during a respiratory cycle
Airway—any part of the respiratory tract
through which air passes during breathing
Airway resistance—resistance to the flow of
air in the passages to the lungs
Albedo—the ratio of the amount of electro-
magnetic radiation reflected by a body to
the amount incident upon it, commonly ex-
pressed as a percentage
Aldehyde—any of a class of organic com-
pounds containing the group R-CHO, in-
termediate in state of oxidation between
primary alcohols and carboxylic acids
Alveolus (pi. alveoli)—a small, sac-like dila-
tion at the innermost end of the airway,
through whose walls gaseous exchange
takes place
Analysis, factorial—a method of evaluating
certain definite integrals by the use of
gamma functions
Anaplasia (adj. anaplastic)—a'condition in
tumor cells in which normal functional and
physical differentiation is lost
Anthracosis—a disease- of the lungs caused
by inhalation and accumulation of carbon
particles
Antirachitic—opposing or preventing the
development of rickets
Aphid (aphis)—a small sucking insect; a
plant louse
Atelectasis—the collapse of all or part of a
lung, with resultant loss of functioning
tissue
Attenuation—In physics, any process in
which the flux density (or power, ampli-
tude, intensity, illuminance, etc.) of a
"parallel beam" of energy decreases with
increasing distance from the energy source
Auscultation (adj. Auscultatory)—the act of
listening for sounds within the body, us-
ually with the use of a stethoscope
Bacillus subtilis—a common microorganism
found in soil and water and frequently oc-
curring as a laboratory contaminant; rare-
ly implicated in causing disease
195
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Benzo (a) pyrene—a polycyclic aromatic hy-
drocarbon which under certain circum-
stances has been shown to produce cancer
Bifurcation—a site where a single structure
divides into two branches
Blistering, osmotic—paint blisters caused by
moisture picking up water-soluble salts in
its passage through the paint film, result-
ing in an ideal situation for osmosis which
represents a tremendous force formation
of blisters
Bloivby—the leakage of gas or liquid be-
tween a piston and its cylinder during op-
eration
Body, asbestos—a fiber of asbestos sur-
rounded by a deposit of protein material
Bronchiectasis—a chronic dilatation of a
bronchial passage
Bronchiole—one of the finer subdivisions of
the bronchial tree
Bronchitis—an inflammation of the bronchi,
usually manifest clinically by cough and
the production of sputum
Bronchitis, chronic—a long-standing inflam-
mation of the bronchi characterized by ex-
cessive mucus secretion in the bronchial
tree and manifested by a persistent or re-
current productive cough. For the pur-
poses of definition, these symptoms must
be present on most days for a minimum of
3 months of the year for at least 2 suc-
cessive years (American Thoracic Soci-
ety)
Bronchoconstriction—a diminution in the
size of the lumen of a bronchus
Bronchus (pi. bronchi)—one of the larger
air passages in the lung
Broth—a liquid medium for the cultivation
of microorganisms
Capacity, forced vital (FVC)—the largest
amount of gas which can be forcibly ex-
pired from the lungs following a maximal
inspiration
Capacity, functional residual (FRC)—the
volume of gas remaining in the lungs at
the resting end-expiratory level
Capacity, total lung (TLC)—the volume of
gas contained in the lungs at full inspira-
tion
Capacity, vital—the maximum volume of
gas which can be expired from the lungs
following a maximum inspiration
Carbonation—conversion into a carbonate
(which in many cases refers to one or
more members of the calcite, dolomite, and
aragonite groups of minerals) impregna-
tion with carbon dioxide
Carcinogen—a substance capable of causing
living tissue to become cancerous
Carcinogenesis—the production of cancer
Carcinoma—cancer; malignant growth made
up of cells derived from epithelial tissue
Carcinoma, bronchogenic—cancer arising in
bronchial tissue of the lung
Carcinoma, squamous cells—cancer develop-
ing from squamous epithelial cells
Carcinoma in situ—a neoplastic entity in
which tumor cells are present but the in-
vasion of normal tissue has not yet taken
place
Cardoivascular—pertaining to the heart and
blood vessels
Cercospora beticola—a member of the genus
Cercospora, which consists of imperfect
fungi that are leaf parasites with long
slender multi-septate spores
Channel black—carbon black made by im-
pingement of a luminous natural gas flame
against an iron plate from which it is
scraped at frequent intervals; properties
vary widely, but the material has an un-
usually fine state of subdivision and great
surface area
Chloroplast—a specialized body (a plastid)
containing chlorophyll in the cytoplasm of
plants; the site of photosynthesis and
starch formation in plants
Cholinesterase—any one of several enzymes
that hydrolyze choline esters, occurring
most frequently in nervous tissue and the
blood
Cilium (pi. cilia)—small, hairlike process at-
tached to a free surface of a cell, capable
of rhythmic movement
Clearance—the removal of material from
the body or from an organ
Clinker—kiln-fired limestone from which
commercial cement is made
Coalescence—in cloud physics, the merging'
of two water drops into a single larger
drop
196
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Coefficient, absorption—the fractional rate
at which flux density of radiation decreases
by absorption with respect to the thick-
ness of the absorbing medium traversed
Coefficient, extinction—the sum of the ab-
sorption coefficient and the scattering co-
efficient for a medium that both absorbs
and scatters radiation
Coefficient, scattering—the fractional rate
in the transmission of radiation through a
scattering medium (as of light through
fog) at which the flux density of radia-
tion decreases by scattering in respect to
the thickness of the medium traversed
Coh unit—a measure of light absorption by
particles, defined as that quantity of light
scattering solids producing an optical den-
sity of 0.1
Collagen—a fibrous protein forming the
main supportive structure of connective
tissue
Collector, cyclonic—a centrifugal fraction-
ator in which a vortex of air throws par-
ticles out of a stream, where they collect
or stick to the surface of a container
Comminute—to break or crush into small
pieces
Concentration—the total mass (usually in
micrograms) of the suspended particles
contained in a unit volume (usually one
cubic meter) at a given temperature and
pressure; sometimes, the concentration
may be expressed in terms of total num-
ber of particles in a unit volume (e.g.,
parts per million); concentration may
also be called the "loading" or the "level"
of a substance concentration may also per-
tain to the strength of a solution
Conifer—belonging to the coniferales order,
consisting primarily of evergreen trees
and shrubs
Consolidation—the process by which a dis-
eased lung passes from an aerated col-
lapsible state to one of an airless solid
consistency because of accummulation of
exudate
Contrast—in visual range theory, the ratio
of the apparent luminance of a target mi-
nus that of its background to the apparent
luminance of the background
Conurbation—a great aggregation or con-
tinuous network of urban communities
Coryza—an acute catarrhal condition of the
nasal mucous membrane with profuse dis-
charge from the nostrils
Criteria, air quality—a compilation of the
scientific knowledge of the relationship be-
tween various concentrations of pollutants
in the air and their adverse effects
Cryolite—a mineral fluoride consisting also
of sodium and aluminum
Cuticle—a varnish-like layer covering the
surface of a leaf
Cytoplasm—the protoplasm of a cell (ex-
cluding that of the nucleus)
Dead space, anatomic—that part of the air-
way occupied by gas which is unavail-
able (by its location) to take part in oxy-
gen-carbon dioxide exchange through the
walls of the alveoli
Dead space, physiologic—the volume of gas
within the alveoli which does not partici-
pate in the oxygen-carbon dioxide ex-
change through the walls of the alveoli
Dehydrogenase—any one of various enzymes
which accelerate the removal of hydrogen
from metabolities and its transfer to other
substances, thus playing an important role
in biological oxidation-reduction processes
Deliquesce—to dissolve gradually and be-
come liquid by absorbing moisture from
the air
Density—the amount of matter per unit vol-
ume, usually expressed in grams per cubic
centimeter
Density, optical—the degree of opacity of
any translucent medium; the common loga-
rithm of the ratio of the initial intensity
of light to the intensity of transmitted or
reflected light
Desorption—the release of a substance which
has been taken into another substance by
a physical process or held in concentrated
form upon the surface of another sub-
stance; the reverse of absorption or ad-
sorption
Desquamate—to cast off epidermis in shreds
or scales; to peel off in sheets or scales
Deviation, standard geometric (o-gr)—a
measuie of dispersion of values about a
geometric mean; the portion of the fre-
quency distribution that is one standard
geometric deviation to either side of the
197
-------
geometric mean accounts for 68% of the
total samples
Deviation, standard normal—a measure of
dispersion of values about a mean value;
the square root of the average of the
squares of the individual deviations from
the mean
Dextran—a water-soluble polymer used
therapeutically as a plasma substitute
Diameter, count median (CMD)—the geo-
metric median size of a distribution of
particles, based on a numerical count
Diameter, mass median (MMD)—the geo-
metric median size of a distribution of par-
ticles, based upon a weight (usually de-
rived from a Stokes' Diameter)
Diameter, Stokes'—the diameter that a unit
density particle of spherical shape would
have if it behaved the same as the particle
being studied
Dichotomous—dividing in succession into
pairs; showing a dual arrangement
Distal—furthest or most remote from the
median line of the body, from the point
of attachment, or from the origin; periph-
eral (cf. proximal)
Diverticulum (pi. diverticula)—a pouch or
cul-de-sac of a hollow organ
Dosimetry—the accurate measurement and
determination of (medicinal) doses
Dyspnea—difficult or labored breathing
Earth, diatomaceous—a chalky material used
as a filter aid, an absorbent, a filler, an
abrasive, and as thermal insulation
Edema—a condition due to the presence of
abnormally large amounts of fluid in the
intercellular tissue spaces of the body
Effluent—something that flows out, such as
a liquid discharged as a waste
Elution—the process of washing out, or re-
moving with the use of a solvent
Elutriator, fractional—a fractional sampler
which removes coarse particles from the
air by gravity settlement
Emphysema—a swelling due to the presence
of air, usually excess or additional air.
The term is usually used to refer to pul-
monary emphysema
Emphysema, pulmonary—a condition in
which there is overdistension of air spaces
and resultant destruction of alveoli and
loss of functioning lung tissue
Endocytosis—a condition or disease arising
from the inclusion within a cell of ma-
terial which does not properly belong there
Entomology—zoology dealing only with in-
sects
Epidemiology—a science dealing with the
factors involved in the distribution and
frequency of a disease process in a popu-
lation
Epidermis—the outermost layer of skin in
animals; any integument
Epiglottis—a plate of cartilage which covers
the entrance to the larynx during swal-
lowing, thus preventing food or fluid from
entering the windpipe
Epithelium—a closely packed sheet of cells
arranged in one or more layers, covering
the surface of the body and lining hollow
organs
Epithelium, columnar—a type of epithelium
composed of tall, prismlike cells
Epithelium, spuamous—a type of epithelium
composed of plate-like cells
Ergometer—an instrument which measures
work done, e.g., by muscle contraction; a
dynamometer
Evaginate—to turn inside out or protrude
by eversion
Extrapolate—to project data into an area
not known or experienced, and arrive at
knowledge based on inferences of conti-
nuity of the data
Fibrosis—the development of fibres tissue;
sclerosis
Filiform—having the shape of a thread or
filament
Floe—something occurring in indefinite
masses or aggregates
Fluorosis—a pathologic condition resulting
from excessive intake of fluorine
Fluorspar—the mineral fluorite
Flux—a flowing or discharge of fluid; a sub-
stance used to promote fusion (as by re-
moving impurities) of metals or minerals;
the rate of transfer of fluid, particles, or
energy (as radiant energy) across a given
surface
Fume—an aerosol formed by the condensa-
tion of vapors as they cool
Gastric—pertaining to the stomach
Gastrointestinal—pertaining to the stomach
and intestines
198
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Goblet cell—a type of epithelial cell contain-
ing mucus and having the shape of a flask
or goblet
Gravimetric—of or relating to measurement
by weight
Haze—fine dust or salt particles dispersed
through a portion of the atmosphere; the
particles are so small that they cannot be
felt or individually seen with the naked
eye, but they diminish horizontal visibil-
ity and give the atmosphere a character-
istic opalescent appearance that subdues
all colors
Hematite—the mineral iron oxide; Fe2O3
Histamine—a substance which produces di-
latation of capillaries and stimulates gas-
tric secretion, occurring in both animal and
vegetable tissues; /3-imidazolethylamine
Histogram—a graphical representation us-
ing a series of bars
Histology—the study of the anatomy of tis-
sues and their microscopic cellular struc-
ture
Hydrocarbon—a compound containing only
hydrogen and carbon. This group is sub-
divided into alicyclic, aliphatic, and aro-
matic hydrocarbons according to the ar-
rangement of the atoms and the chemical
properties of the compounds.
Hygroscopic—readily absorbing and retain-
ing moisture from the atmosphere
Hyperplasia (adj. hyperplastic)—an in-
crease in the number of cells in and bulk
of a tissue, with retention in normal func-
tion and cellular structure
Illumination—the process in which light is
brought to some surface or object
Impactor, cascade—an instrument which
employs several impactions in series to
collect successively smaller sizes of par-
ticles
Incidence—the rate at which a certain event
or disease occurs
Insolation—the rate at which direct solar ra-
diation (of all wavelengths) is delivered
to a unit area of a horizontal surface, us-
ually at or near ground level
Insulation—the prevention of the transfer
of energy between two conductors by sepa-
ration of the conductors with a non-con-
ducting material; or, the non-conducting
material itself
Interstitial—pertaining to or situated in the
space between cells
In vitro—in a test tube or other artificial
environment
In vivo—within a living body
Isotherm—a line on a chart representing
changes of volume or pressure under con-
ditions of constant temperature; or lines
on a map connecting points having the
same temperature
Ketone—any of a class of organic compounds
that are characterized by a carbonyl group
attached to two carbon atoms, usually con-
tained in hydrocarbon radicals or in a
single bivalent radical, similar to alde-
hydes but less reactive
Lacrimation (lachrymation)—tear forma-
tion, especially in excess
Langley—a unit of energy per unit area,
commonly employed in radiation theory
and equal to one gram-calorie per square
centimeter
Larynx—the organ concerned with the pro-
duction of the voice, situated at the upper
end of the trachea
Lesion—an injury or other circumscribed
pathologic change in a tissue
Logarithm—a number which represents the
power to which a given number must be
raised to produce another given number
Lumen—the inner space of a hollow organ
or tube
Lycopodium—a genus of club-moss; a pow-
der ("vegetable sulfur") used to prevent
the agglutination of pills in a box or as
a dusting powder
Lymph—a fluid that is collected from the
tissues throughout the body, flows in the
lymphatic vessels, and is eventually added
to the bloodstream
Lymphoma—any neoplasm developing from
lymphatic tissue
Macrophage—a large phagocytic cell found
in the connective tissue, especially in areas
of inflammation
Malignancy—something which tends to be-
come progressively worse and if un-
checked could result in death
Mastoiditis—an inflammation of the skull
bone behind the ear
Mean, geometric (M,)—a measure of cen-
tral tendency for a log-normal distribution;
199
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the value, in a given set of samples, above
which 5Qc/c of the values lie
Meatus—a natural body passage, particular-
ly the external opening of a canal
Mesothelioma—a tumor which develops from
the lining of a coelomic body cavity
Metaplasia (adj. metaplastic)—a change in
the cells of a tissue to a form which is not
normal for that tissue
Metastable—marked only by a slight margin
of stability
Meteorological range (standard visibility,
standard visual range)—an empirically
consistent measure of the visual range of
a target; a concept developed to eliminate
from consideration the threshold contrast
and adaptation luminance, both of which
vary from observer to observer
Morbidity—the occurrence of a disease state
Morphology—a branch of biology dealing
with the structure and form of living or-
ganisms
Mortality—the ratio of the total number of
deaths to the total population, or the ratio
of the number of deaths from a given dis-
ease to the total number of people having
that disease
Motion, Brownian—the rapid random mo-
tion of small particles due to bombard-
ment by surrounding molecules which are
in thermal motion
Mucin—a glycoprotein or mucopolysaccha-
ride secreted by mucous glandular cells
Mucopurulent—pertaining to an exudate (or
sputum) that is chiefly purulent (pus) but
also contains significant amounts of mucus
Mucoviscidosis—cystic fibrosis
Mucus (adj. mucous)—the clear viscid se-
cretion of a mucous membrane
Mural—pertaining to the wall of a cavity
Mustard gas—an irritating and toxic volatile
liquid used as a weapon in World War I;
dichloroethyl sulfide
Naris (pi. nares)—a nostril or other open-
ing into the nasal cavity
Nasopharynx—the part of the pharynx
(throat) lying above the level of the soft
palate
Nebulize—to reduce to a fine spray
Necrosis—localized death of cells
Neoplasm—any abnormal growth, such as
a tumor
Nephelometer—a photometric instrument
for the determination of the amount of
light transmitted or scattered by a sus-
pension of particles
Node—a circumscribed swelling
Node, lymph—one of many accumulations of
lymphatic tissue situated throughout the
body
Nomogram—a graph that enables one to
read off the value of a dependent variable
with the use of a straightedge, when the
values of two or more independent vari-
ables are known
Nucleation—the process of particle growth
through collection around a nucleus
Nucleus (condensation nucleus)—a particle
in the size range from O.!/* to I/* which
serves as a nidus on which water or other
vapors in the air can condense to form
liquid droplets
Olefin—a class of unsaturated aliphatic hy-
drocarbons of the general formula CnH2n
Olfactory—pertaining to the sense of smell
Ophthalmic—pertaining to the eye
Otitis—an inflammation of the ear
Palisade tissue—a layer of columnar cells
rich in chloroplasts found beneath the up-
per epidermis of foliage leaves
Parameter—an arbitrary constant which
characterizes a mathematical expression
Parenchyma—the specific or functional tis-
sue of a gland or organ, as opposed to its
supporting framework
Particle—any dispersed matter, solid or liq-
uid, in which the individual aggregates
are larger than single small molecules
(about 0.0002/j, in diameter), but smaller
than about BOOju in diameter
Particulate—existing in the form of minute
separate particles
Pathogenesis—the production or the mode
of origin and development of a disease
condition
Pathology—the study of the essential nature
of disease, particularly with respect to the
structural and functional changes in or-
gans and tissues
Peritoneum—the membrane lining the ab-
dominal cavity and investing the viscera
Phagocyte—a cell that has the power of in-
gesting microorganisms and other small
particles
200
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Phagocytosis—the ingestion of a microor-
ganism or other small particle by a phago-
cyte
Pharynx—the upper expanded portion of the
alimentary canal lying between the mouth,
the nasal cavities, and the beginning of
the esophagus; the throat
Photometer—an instrument for measuring
luminous intensity, luminous flux, illumi-
nation, or brightness by comparison of two
unequal lights from different sources
Photomicrograph—a photograph of a mag-
nified image of a small object
Photosynthesis—the formation of carbohy-
drate from carbon dioxide and water in
the presence of chlorophyll and light, in
plant tissues
Physiology—a science which studies the
function of a living organism or its parts
Phytotoxic—harmful to plant materials
Plasmolysis—the shrinking of the cytoplasm
away from the wall of a living cell due to
water loss by osmotic action
Plethysmograph—an apparatus for the de-
termination and recording of a change in
the size of an organ or limb or body
Pneumococcus (pi. pneumococci)—a bacte-
rial organism which most often infects the
lung and is a common cause of pneumonia;
Diplococais pneumoniae
Pneumoconiosis—a fibrous reaction in the
lungs, caused by the retention of certain
inhaled dusts in the lungs
Pneumonitis—a general term for inflamma-
tion of the lung
Pneumotachygraph—an instrument used to
determine the force and velocity of re-
spired air
Polystyrene—a clear, colorless polymer of
styrene, an unsaturated hydrocarbon of
theformC6H5CH = CH,
Potentiation—synergism, as between two
agents which together have a greater ef-
fect than the sum of their effects when
acting separately
Precipitation—any or all of the forms of
water particles, whether liquid or solid,
that fall from the atmosphere and reach
the ground. It is a major class of hydro-
meteor, but is distinguished from cloud,
fog, dew, rime, frost, etc. in that it must
"fall," and is also distinguished from cloud
and virga in that it must reach the ground
Precipitator, electrostatic—an apparatus for
the removal of suspended particles from
a gas by charging the particles and pre-
cipitating them by applying a strong elec-
tric field
Predator—an organism living by preying on
other organisms
Prevalence—the number of cases of a dis-
ease at a given time
Prodrome—the symptoms preceding the ap-
pearance or recognition of an actual dis-
ease state
Proteinosis—-the accumulation of protein in
excess in the tissues
Proteinosis, alveolar—a chronic progressive
lung disease characterized by the accumu-
lation of granular proteinaceous material
in the alveoli
Proximal—nearest to the center of the body
or the point of origin (cf. distal)
Radioautograph (autoradiogram)—a radio-
graphic portrayal of an object or organism
made by the inherent radioactivity of the
object or organism
Rale—an abnormal respiratory sound heard
in auscultation of the chest
Ratio, standardized mortality—-the ratio of
the number of deaths observed in a given
population over a given period of time to
the number of deaths expected to occur
in the given population over the same pe-
riod of time if the given population be-
haved as any other group of similar com-
position would during that same period
Reflectometer-—a photometric or electronic
device for measuring the reflectances of
light or other radiant energy
Regression—a trend or shift toward a mean.
A regression curve or line is thus one that
best fits a particular set of data according
to some principle
Rhinitis—an inflammation of the nasal mu-
cous membrane
Rhinorrhea—"runny nose"
Rhonchus (pi. rhonchi)—a dry, coarse sound
usually originating from partial obstruc-
tion in a bronchial tube
Scattering, Mie—any scattering produced by
spherical particles, without specific regard
to the comparative size of radiation wave-
length or particle diameter
201
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Scattering, Rayleigh—any scattering proc-
ess produced by spherical particles whose
radii are smaller than about one-tenth the
wavelength of the scattered radiation
Sigmoid curve—a "bell-shaped" curve serv-
ing as a prototype for the normal distri-
bution of data about a mean
Silicosis—a type of pneumoconiosis caused
by inhalation of silica dust and character-
ized by silica-containing nodules of scar
tissue in the lung parenchyma
Sorption—the generalized term for the many
phenomena commonly included under the
terms adsorption and absorption, when the
nature of the phenomenon is unknown or
indefinite
Spirometer—an instrument for the measure-
ment of the volume of gas respired by the
lungs
Spore—a reproductive element of many
lower organisms
Squamous—resembling or covered with
scales
Standards, air quality—levels of air pollut-
ants which cannot legally be exceeded dur-
ing a specific time in a specific geographi-
cal area
Stasis—the slowing down or cessation of the
normal flow
Stigma—the part of the pistil of a flower
which receives the pollen granules and on
which they germinate
Stokes' Law—a law in physics stating that
the force required to move a sphere
through a given viscous fluid at a low uni-
form velocity is directly proportional to
the velocity and radius of the sphere
Stoma (pi. stomata)—a small opening in the
epidermis of a plant
Subcutaneous—beneath the skin
Supercool—to cool below the freezing point
without solidification or crystallization
Supersaturation—a condition of containing
an excess of some material or force, over
the amount required for saturation nor-
mally
Synergism—a situation in which the com-
bined action of two or more agents acting
together is greater than the sum of the
action of these agents separately
Systemic—relating to the body as a whole,
rather than to its individual parts
Tannin—any one of a group of soluble as-
tringent complex phenolic substances that
are widely distributed in plants
Terpene—any one of a class of isomeric hy-
drocarbons of the prototype C10H16 that
are found in many essential oils, but espe-
cially from conifers; may also refer to any
of various compounds derived from ter-
pene hydrocarbons or closely related to
them
Tipburn—a disease of the potato, lettuce, and
other cultivated plants, characterized by
burning or browning of the tips and mar-
gins of the leaflets and caused by loss of
water due to excessive heat and sunshine
Toxicology—the study of poisons, including
their preparation, identification, physio-
logic action, and antidotes
Trachea—windpipe; the airway extending
from the larynx to the origin of the two
mainstem bronchi
Tracheobronchitis—an inflammation of the
trachea and bronchi
Turbidity—in meteorology, any condition in
the atmosphere which reduces its trans-
parency to radiation, especially to visible
radiation
Tyndallometer—an instrument that meas-
ures suspended particle concentration by
the amount of light scattered out of a
beam
Ultrafilterable—capable of being separated
by a dense filter which is used for the
filtration of a colloidal solution holding
back the dispersed particles but not the
liquid
Updraft—an upward movement of air or
other gas
Ventilation, minute—the total volume of gas
respired in one minute, i.e., the tidal vol-
ume multiplied by breaths per minute
Visibility—In United States weather observ-
ing practice, the greatest distance in a
given direction at which it is just possible
to see and identify with the unaided eye
(a) in the daytime, a prominent dark ob-
ject against the sky at the horizon, and
(b) at night, a known, preferably unfo-
cused, moderately intense light source.
After visibilities have been determined
around the entire horizon circle, they are
202
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resolved into a single value of prevailing
visibility for reporting purposes.
Visual range—the distance, under daylight
conditions, at which the apparent contrast
between the specified type of target and
its background becomes just equal to the
threshold contrast of an observer; to be
distinguished from the night visual range.
The visual range is a function of the at-
mospheric extinction coefficient, the albe-
do and visual angle of the target, and the
observer's threshold contrast at the mo-
ment of observation.
Volume, forced expiratory (FEV)—the vol-
ume of gas forcibly exhaled over a given
time interval (usually measured in sec-
onds) after maximum inspiration, e.g.,
FEVi.o for this measurement over a 1.0
second period.
Volume, minute—same as minute ventilation
Volume, tidal—the volume of gas inspired or
expired during each respiratory cycle.
203
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AUTHOR INDEX
Ackley, C., 94
Agnese, G., 162, 172-173
Ahlquist, N. C., 56, 57, 59
Albert, R. E., 122
Alcocer, A. E., 26
Altshuler, B., 113, 117, 118
Amberg, H. R., 106
Amdur, M. O., 113, 131, 132, 133,
134, 136
Andersen, A. A., 17, 19
Anderson, D. O., 150, 161, 164, 165,
173-174
Anderson, P. J., 92
Andrea, J., 140
Angel, J. H., 168, 175
Angstrom, A. K., 38, 39, 43, 53
Antler, M., 69
Antweiler, H., 121
Arnett, L. C., 122
Ashworth. J. R., 41, 44
Auerbach, 0., 141
Axt, C. J., 19
Ayer, H. E., 137
Baetjer, A. M., 132
Balzer, J. L., 137
Barfinkel, L., 141
Barlett, F. E., 106
•Bates. D. V., 163, 173-174
Baulch, D. M., 19, 37
Baumberger, J. P., 117
Bechmann, H., 117
Becker, W. H., 165, 173-174
Belton, J., 154
Berge, H., 94
Biersteker, K., 168, 175
Black, S., 118
Blifford, I. H., 11
Bohne, H., 91, 92, 94
Bonser, G. M., 139
Boren, H. C., 135
Bowden, A. T., 26
Bownes, K., 105
Bradley, W., 152, 154, 156, 171, 172
Brandt, P., 17
Brasser, L. J., 150, 153, 158
Braverman, M. M., 153, 154, 171
Brieger, H., 122
Brier, G. W., 41
Briscoe, W., 122
Brooke, A. G. F., 71
Brown, C. E., 117
Brown, D. A., 157, 172
Brown, J. H., 118
Brown, M. C., 137
Bryson, R. A., 42, 43
Buck, S. F., 157, 172
Bunyard, F. L., 99
Burgess, F., 130, 131, 136
Burgess, S. E., 151, 171
Burn, J. L., 157, 158, 159, 164, 172-
173, 174
Bye, W. E., 167
Cadle, R. D., 8, 10
Cambell, J. A., 137
Capps, R., 135
Carey, W. F., 69
Games, W. H., 141
Cartwright, J., 69, 71
Casarett, L. J., 122. 123
Cassel, E. G., 150, 154, 156, 171, 172
Cefls, F., 139
Chaney, A. L., 26
Changnon, S. A., Jr., 41
Charlson, R. J., 19, 54, 55, 56, 57, 59
Chass, R. L., 24
Christofano, E. E., 135, 136
Clark, J. G., 22
Clark, W. E., 23, 54
Clemo, G. R., 137
Coblentz, H., 39
Coffin, D. L., 129
Collet, A., 123
Collins, G. F., 106
Conner, W. D., 53
Cook, K. M., 118
Cooley, R. N., 132
Cooper, W. C., 137
Copson, H. R., 66, 67, 68, 69
Corn, M., 6, 8, 19, 132, 133
Coughanower, D. R., 136
Cralley, L. J., 137
Creasia, D. A., 133
Crider, W. L., 26
Crowley, D., 154,155
Cuffe, S. T., 5
Cullumbine, H., 130, 132, 136
Czaja, A. T., 91, 92
Dalhamn, T., 121, 122, 135
Barley, E. F., 90, 91, 92, 93
Dautrebande, L., 117, 119, 133, 135
Davies, C. N., Ill, 117, 118, 119,
121, 122, 123, 132, 135, 136
Davies, R. I., 157, 171-172
Day, J. A., 11
De Groot, I., 99, 101
Delly, J. G., 18
De Maio, L., 19
Dennis, W. L., 118
Dessens, J., 18
De Treville, R. T., 135
Devir, S. E., 131
Diamond, J. R., 149, 155, 156, 171,
172
Dickerson, R. C., 20, 22
Diem, M., 17
Djordjevic, N., 11
Dobrogorski, 0. J., 130
Dohan, F. C., 164
Doherty, R. E., 26
Douglas, J. W. B., 165, 173-174
Downs, W. L., 122
Draftz, R. G., 18
Draper, P., 26
Drinker, P., 8, 113, 117, 118, 132
Drolette, B. M., 153, 154, 171
Du Bois, A. D., 133
Eckel, O., 39
Edmonds, S. M., 106
Elliott, A., 166
Ellis. O. B., 66, 67, 68
Ellison. J. M.. 22
Epstein, S. S., 140
Erdhardt, C., 153, 154, 171
Falk, H. L., 120, 134, 137,138,141
Faoro, R. B., 16
Faulds, J. S.. 139
Fensterstock, J. C., 16
Ferris. B. G., Jr., 164, 173-174
Field, F., 153, 154, 171
Fieldner, A. C., 117
Findeisen, W., 114, 115, 119
Finn, J. L., 117
Firket, J., 150
Fischer, W. H., 19
Fish, B. R., 10
Fisher, M., 121
Flesch, J., 132
Fletcher, C. M., 168, 175
Fochtman, E. C., 71
Foster, K. E., 17
Frank, E. R., 20, 23
Frederick, R. H., 41
Friedlander, S. K., 54, 58
204
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Gates, D. M., 38
Georgii, H. W., 41
Gibb, F. R., 117, 119, 121
Gilbert, J., 69
Giles, C. H., 69
Giner, R., 40
Girorer, W., 117
Glasser, M., 154, 155
Goetz, A., 6, 10, 19, 58, 59,, 106
Gong, W. K., 26
Gore, A. T., 151, 171
Graf, P., 132
Graff-Baker, C., 71
Greenburg, L., 68. 69, 153, 154, 171
Greenwood, D. A.. 95
Greenwood, J. A., 69
Greezuitay, L. A., 139
Gross, P.. Ill, 123, 135
Grote. M. J., 139
Gruber, C. W., 17
Gucker, F. T., 19
Guderian, R., 92
Haddow, A., 139
Hagstrom, R. M., 159, 161, 172-173
Haines, G. F., Jr., 20
Hamilton. R. J., 17
Hammond, C., 130
Hammond, E. C.. 141
Hand, I. F., 40
Handyside, A. J., 166, 168, 174-175
Harris, J., 69
Harris, W. B., 17
Harrison, L. E., 95
Hatch, T. F., 8, 111, 119, 120, 123
Haythorn, S. R., 131
Helwig, H. L., 26
Hemeon, W. C. L., 17, 20
Hendrix, W. G., 23
Hess, V. F., 40
Hewson, E. W., 17
Hilding, A. C., 122
Hill, A. C., 93, 94
Hill, I. D., 148, 168, 175
Hitchcock, A. E., 93, 94
Hodkinson, J. R., 53
Hoffman, P., 19
Holbrow, G. L., 71
Holden, F. R., 95
Holland, W. W., 162, 163, 166, 167,
172-173, 174-175
Holma, B., 122
Holzworth, G. C., 51
Horning, E. S., 139
Horton, R. J. M., 164
Horvath, H., 19, 54, 56, 57, 59
Hudson, J. D., 66, 67
Hueper, W. C., 137
Huey, N., 81
Humphreys, W. J., 43
Kurd, F. K., 23
Ide, H. M., 20
Imada, M., 57
Jacobs, M. B., 65, 69, 153,154,171
Jacobson, J. S., 93, 94
Jennings, 0. E., 94
Jens, W., 24, 25
Johnstone, H. F., 136
Jones, E. E., 26
Joosting, P. E., 151, 153, 158
Joshi, S., 140
Junge, C. E., 11, 23, 53, 54
Jurksch. G., 17
Jutze, G. A.. 17
Kaiser, E. R., 25, 107
Kakis, F., 105
Kallai, T., 58, 59
Kanitz, S., 162, 172-173
Katz, M., 17, 22
Keagy, D. M., 21
Keenan, R. G., 137
Kemeny. E., 21
Kemnitz, D. A., 5
Kenrick, G. W., 39
Kerka, W. F., 107
Klarman, H. E., 84
Kline, D. B., 41
Knowelden, J., 166, 168, 174-175
Kolb, L. H., 139
Kolesnichenko, T. S., 139
Korff. F., 39
Kotin, P., 120, 132, 136, 137, 138,
141
Krahl, V.E., 111
Kramer. G. D.. 21, 22
Kreichelt, T. E., 5
Kuepel, R. E., 138
Kurland, L. T., 156
Kuschner, M., 140
La Belle, C. W., 135, 136
Lainhart, W. S., 137
La Mer, V. W., 118
Landahl, H. D., 114, 118
Landau, E., 159, 162, 164, 172-174
Landsberg, H., 38, 39, 40, 41
Langer, G., 71
Larrabee, C. P., 66, 67, 68, 69
Lawther, P. J., 153, 168, 169, 171,
175
Le Clerc, E., 69, 81
Lee, G., 113
Lee, R. E., Jr., 19, 26
Lehmann, C., 118
Lehmann, K., 117
Lemke, E. E., 12
Leonard, A. G.. 154, 155
Linnell, R. H., 105
Lippmann, M., 17, 122
Lloyd, T. C., 167
Lodge, J. P., 19, 20, 23
Long, J. E., 135, 136
Ludwig, F. L., 19
Ludwig, J. H., 42, 43
Lunn, J. E., 166
Lynch, J. R., 137
Mac Phee, R. D., 26
Magill, P. L., 95
Mantel, N., 140
Manzhenko, E. G., 167, 174.-175
Marcus, S. C., 167
Mark, H. L., 106
Markul, I., 138
Markush, R. E., 157
Martin, A. E.( 152, 153, 156, 171-
172
Mateer, C. L., 40
McCaldin, R. O., 167
McCarroll, J., 150, 154, 156, 171-
172
McConnell, W. J., 117
McCormick, R. A., 19, 37, 38, 42,
43
McCrone, W. C., 18
McCune, D. C., 93, 94
McDermott, M., 133
McKee, H. C., 105
McMullen, T. B., 16
McNerney, J., 119
Meeker, G. O., 11
Meetham, A. R., 40, 41
Megaw, W. J., 23
Meller, H. B., 69, 71
Metnieks, A. L., 23
Michelson, I., 81
Middleton, W. E. K., 51, 52
Mie, G.. 10, 55
Miller, A., 135
Miller, E. C., 137
Miller, P. M., 94
Miller, W. S., Ill
Milley, P. S., 123
Miner, M. L., 95
Mitchell, J. M., Jr., 43
Mitchell, R. I., Ill
Moll, A. J., 136
Morrow, J., 105
Morrow. P. E., 111. 118, 119,121
Mountain, I. M., 150, 156, 171-172
Mountain, J. D., 149, 156, 171-172
Mueller, P. K., 26, 57
Nadel, J. A., 17, 132
Nader, J. S., 19
Nagelschmidt, G., 69
Nau, C. A., 132
Neal, J., 132
Nelson, N., 113, 117, 118, 122
Neuberger, H., 40
Ney, F. G., 118
Noll, K. E., 55, 57
Nussbaum, R., 92
205
-------
O'Connor, J. J., Jr., 81
O'Konski, C. T., 19
Orr, C., 23
Ortiz, H., 39
Ott, R. R., 105
Owens, J. S., 117
Ozolins, G., 12
Paccagnella, B., 167, 174-175
Pack, M. R., 93, 94
Pajenkamp, H., 92, 93
Palm, P. E., 119
Palmes, E. D., 113, 117
Parish, S. B., 89
Park, J. C., 21
Parker, A., 71
Pascua, M., 137
Pate, J. B., 19
Patterson, H. S., 117
Patterson, R. K., 19, 26
Pattle, R. E., 130, 131, 136
Paulus, H. J., 154
Pavanello, R., 167, 174-175
Payne, W. W., 138
Peirce, G. J., 89, 91
Pemberton, J., 157, 158, 159, 164,
172-174
Pesarin, F., 167, 174-175
Peterson, C. M., 54
Peterson, J. T., 43
Petrie, T. C., 72
Petrilli, F. L., 162, 172-173
Pfltzer, E. A., 123
Phillips, P. H., 95
Pickard, H. B., 19
Pilat, M. J., 54, 56
Pitts, J. N., Jr., 19
Plotkin, T., 113
Policard, A., 123
Pollack, L. W., 23
Potter, J. G., 41
Pregermain, S., 123
Preining, 0., 11, 58, 59
Preston, R., St. J., 66, 69
Prindle, R. A., 164, 167, 173-174
Przemeck, E., 93
Pueschel, R. F., 10, 19, 54, 55, re,
59
Purvance, W. T., 23
Pybus, F. C., 137
Pylev, L. N., 139
Quebedeaux, W. A., 105
Raymond, V., 92
Reed, J. I., 153, 154, 171
Rees, W. H., 71 ,72
Rehm, F. R., 24, 25
Reid, D. D., 162, 163, 165, 167, 172-
173, 174-175
Reid, L., 135
Rich, S., 94
Rich, T. A., 23
Ridker, R. G., 84
Rinehart, W. E., 135
Robbins, R. C., 10
Robison, C. B., 101
Robinson, E., 19, 51, 52, 53, 58
Robinson, N., 38
Robson, C. D., 17
Roderick, W. R., 105
Roesler, J. R., 19
Ronald, G., 18
Rose, A. H., 24
Rossano, A. T., 105
Rowling, H., 26
Saffiotti, U., 139
Saito, Y., 117
Salem, H., 130, 132, 136
Samuels, S. W., 99, 101
Sanderson, H. P., 15, 22
Sanyal, B., 66, 69
Sauberer, F., 39
Sawicki, E., 138, 140
Sawyers, L. A., 113
Sayers, R. R., 117
Scheffer, F., 93
Schilling, F. J., 165, 173-174
Schnurer, L., 131
Schonbeck, H., 92
Schrader, J. H., 39
Schrenk, H. H., 134
Schueneman, J. J., 101
Schusky, J., 99
Scott, J. A., 152, 171
Scott, W. E., 105
Selikoff, I. J., 130
Seltser, R., 162, 163, 167, 172-173,
174-175
Sensenbaugh, J. D., 17
Seriff, N. S., 153, 171
Shabad, L. M., 139
Shaddick, C. W.. 151, 171
Shaffer, N. R., 12
Shaver, J., 135
Sheesley, D., 11
Shelden, J. M., 17
Sheleikhovskii, G. V., 37, 38, 39
Sheppard, P. A., 37
Shubik, P., 139
Shupe, J. L., 95
Sievers, F. J., 94
Silverman, L., 23, 113
Sisson, L. B., 69, 71
Skidmore, J. W., 69
Slater, R. W., 17
Smith, B. M., 10
Smith, R., 16
Smith, W. S., 27, 101
Speizer, F. E., 168, 175
Spiegelman, J., 122
Sprague, H. A., 159, 161, 172-173
Spurny, K., 20
Stagg, J. M., 39, 40
Stalker, W. W., 20, 22, 101
Stanley, T., 138
Steiner, P. E., 138
Steinhauser, F., 39
Steinhubel, G., 91
Shembridge, V., 132
Stern, A. C., 19, 51, 52, 53, 58, 72
Stevenson, H. J. R., 19
Stewart, M. J., 139
Stocks, P., 157, 171-172
Stoeber, W., 17
Stokinger, H. E., 129, 130, 134
Stone, R. W., 162, 163, 167, 172-
173, 174-175
Stout, A. P., 141
Stout, G. E., 42
Stratmann, H., 93
Strauss, W., 23
Strethlow, C., 122
Sullivan, J. L., 22
Sutton, O. G., 106
Swartetrauber, P., 19
Tabershaw, I. R., 137
Tabor, E. C., 71, 72, 139, 140
Taylor, J. R., 26
Tebbens, B. D., 72
Telford, J. W., 42
Thomas, B. G. H., 117
Thomas, M. D., 93, 94
Thompson, R. M., 117
Tice, E. A., 65, 71
Tinker, C. M., 168, 176
Tomashefski, J. F., 112
Tourangeau, F. J., 118
Tourin, B., 81
Toyama, T., 162, 167, 172-173, 174-
175
Tracewell, T. N., 118
Transtrum, L. C., 93, 94
Tremer, H., 132, 136
Tufts, B. J., 23
Turk, A., 105, 106
Uhlig, H. H., 80
Underbill, D. W., 132, 136
Upham, J. B., 68
Valko, P., 43
Van Haut, H., 193
Van Wijk, A. M., 117
Venezia, R., 12
Verma, M. P., 165, 173-174
Vernon, W. H. J., 65
Verssen, J. A., 12
Vintinner, F. J., 132
Volz, F., 19, 37, 43
Von Zuilen, D., 150, 153, 158
Vorwald, A. J., 134
206
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Wagman, J., 10, 19, 26 Weinstein, L. H., 93, 94 Wohlers, H. C., 106
Wagner, W. D., 130 Weisbrod, B. A., 84 Wolfson, P., 122
Walkenhorst, W., 117, 119 Went, F. W., 53 Wright, G. W., 167
Waller, R. E., 71, 165, 169, 173-174 Wentzel, K. F., 92 Wynder, E. L., 19
Walter, E. W., 150, 156, 171-172 West, P. W., 19 Yancey A R 113
Walther, J. E., 106 Whitby, K. T., 23 Yant W P 117
Walton, W. H., 17 Wicken, A. J., 162 Yarmus ' L.," 113, 117, 118
Wang, C. S., 54, 58 Williams, J. D., 99 Yocom J E 69 71
Warren, W. V.. 71, 72 Williamson, J. B. P., 69 ' ' " '
Watanabe, H., 154, 167, 171, 174- Wilms, W., 93 Zeidberg, L. D., 101, 156, 159, 161.
175 Wilson, I. B., 118 164, 172-173, 173-174
Wedd, C. D., 131 Winkelstein, W., 158, 172-173 Zickmantel, R., 64, 173-174
Weibel, E. W., 114 Wiseley, D. V., 137 Zwi, S., 132
207
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SUBJECT INDEX
Acrolein toxicity, 135, 136
Adhesion properties, 8-9
Adhesive dustfall collectors, 17
Adsorbed substances
discussion of, 130
Adsorption
role in odors, 107
role in toxicity, 130
Aerodynamic factors
respiratory tract, 113-114, 115-
116
Aerosols
pulmonary effects, 131-137
reduction of toxicity, 130-131
toxicity, 129
Age
relationship to mortality, 148,
161, 158, 160
Air pollution episodes, 15, 150-154
Alveolar deposition, 119
Ammonia toxicity, 122, 135
Animal odors, 107
Aromatic hydrocarbons as carcino-
gens, 137-141
Asbestos
toxicity of, 129-130, 150
Automobile exhaust emissions, 26
Automobiles
corrosion of, 71
B
Beryllium
toxicity of, 129-130, 150
Birmingham, Alabama
public opinion survey, 101
Bronchitis
morbidity studies of, 156, 161-
169
mortality studies of, 150-154,
156-161
Brownian motion, 9,113
Buffalo, New York
mortality studies, 158, 160, 161,
170, 171
public opinion survey, 101
Building materials
deterioration of, 69
Buildings
deterioration, 73-74
Canada
morbidity studies, 163, 164, 173
Cancer
lung, 137, 141, 157-162
mortality, 157, 160-162
stomach, 158, 161-162
Carbon black
toxicity of, 132
Carbon particles
toxicity, 135
Carcinogenic hydrocarbons, 137-
142
Carcinogens
discussion of, 137-142
Cascade impactors, 17, 19
Cement plants
emissions from, 24, 25-26
Cement-kiln dust, 89-93
Channel black effects resp. tract,
132
Chemicals
odors from, 107
Chicago mortality studies. 150
Children
morbidity studies, 165-167
Chlorides
corrosive effects, 71
Clearance model
respiratory system, 120-121
Clearance of particulate matter in
the respiratory system, 121-123
Climate
effects of particulate on, 35, 42-
44
Climatic change
world-wide, 42-44
Coal combustion
effects of smoke on animals, 131-
132
emission from, 24, 27
Coal combustion gases
corrosive effects, 69-70
Coal dust
deposition, 117
physiological effects of, 133
Combustible waste odors, 107
Combustion odors, 107
Combustion products
corrosive effects, 69-70
Computer techniques of sampling,
19
Copper alloys
corrosion of, 68—69
Corn oil particles
deposition, 118
Corrosion of metals, 65-69, 72-74
Costs of air pollution damage, 79—
84
Cotton
soiling and deterioration of, 72,
74
Crust formation on plants, 89-93
Cyclonic collectors, 17
D
Deposition
respiratory system, 112-119
Deposition (dust) on vegetation,
89-96
Desorption
odorants, 106-108
Deterioration of materials, 65-74
Detroit
mortality studies, 150, 154, 171
Diurnal variation
particulate, 40, 41
Dublin, Ireland
mortality study, 154, 155
Dust
corrosive effects, 65-74
effects on resp. tract, 112-119
effect on textiles, 71-72, 74
Dust components, 92-93
Dust mineral
deposition, 117
Dustfall
description of, 11, 16-17
seasonal variation, 39
typical urban values, 17
Dustfall collectors, 17-19
Dustfall jars, 17
E
Economic effects, 79-85
Economical level
relationship to mortality, 156-
158, 159-162, 163, 164, 167,
170, 176
Electrical instruments
corrosion of, 69
Electron microscopy, 20, 23
Elutriators, 17
Emission factors, 24
Emission inventories, 12
208
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England
morbidity studies, 154-156,161,
162, 163, 164-169, 171-176
mortality studies, 150-153, 154,
156-159, 171-176
Epidemiological studies, 150-154
Exacerbation of chronic diseases,
148-149, 154-156, 161-176
Extinction
dependence on particle size, 55
Ferric sulfate
toxicity, 132-133
Filters
sampling, 20-22
Fluorides
effects on vegetation, 93-94
Fluorosis
animal, 95
Fog
correlation with mortality, 150-
153
Food odors, 107
Formaldehyde
toxicity, 122, 135, 136
Foundry
odors from, 107
Foundry dust
effects on vegetation, 94
France
economic effects of air pollution
in, 81
Fuel oil combustion
emissions from, 24
G
Gas and particulate mixtures
synergistic pulmonary effects,
134-137
Gases
toxicity of, 134-137
Great Britain
economic effects of air pollution
in, 81
medical effects of air pollution,
150-159, 161-169, 171-176
H
Haze
particulate size distribution of,
52-53
High-volume sampler, 22-23
Hydration process
dust crust, 91-92
Hydrocarbons as carcinogens, 138-
141
Hygroscopic particles
effect on pulmonary irritants,
136
Illumination
seasonal variation, 37
Industrial odors, 107
International Standard Calibration
Curve for reflectometers, 21
Irkutsk (U.S.S.R.)
morbidity studies, 167, 174
Iron
corrosion of, 65-69
Iron dust
effect on textiles, 72
Iron oxide
effects on vegetation, 94
Italy
morbidity studies, 162, 167, 173,
174
Japan
morbidity study, 162, 167, 173,
174-175
mortality study, 154, 171
Leaves
dust effects on, 89-96
Light absorption, 52-53
Light scattering, 9-10, 37-38, 52-
53, 54-58
Linen
soiling and deterioration of, 71-
74
London
morbidity studies, 154-156,162,
163, 165-167, 168-169, 172, 173,
174, 175
mortality studies, 56-158, 171-
172
Lung deposition, 118-119
Lung dynamics
model of, 114-116
M
Magnesium oxide
effects on vegetation, 94
Membrane niters, 20
Messthelioma, 129-130
Metals (see specific metal)
Meuse Valley
mortality studies, 150
Mie solutions, 54-55
Morbidity
correlation with pollution, 148-
149, 154-156, 161-176
in children, 165-167
incapacity for work, 164-165
Mortality
correlation with acute air pollu-
tion episodes, 148, 150-154
exposures to air pollution, 148,
150-154, 156-161, 169-176
Long term, 156-161
Motor vehicles
emissions from, 26
Municipal incineration
emissions from, 24-25
N
Nasal fractionation, 118
Nashville, Tennessee
morbidity studies, 164, 173
mortality studies, 160, 161, 173
public opinion survey, 100-101
Nephelometer, 19
New Hampshire (Berlin)
Morbidity study, 164, 173
New York City
morbidity studies, 154-156,165,
170, 171, 173, 176
mortality studies, 156, 170-171
Nickel
corrosion of, 67-69
Nitrogen dioxide
toxicity, 135
Nucleation properties, 8-9
Nuisance surveys, 99-102
O
Odors
association with particles, 106-
107
emission sources, 107
Open hearth furnaces
emissions from, 24
Optical density, 20-22
Optical properties, 9-10
Osaka
mortality study, 154, 171
Paint odors, 107
Painted surfaces
deterioration of, 71, 72-74
Particle formation mechanisms, 10-
11
Particle-gas reactions, 10
Particle size
role in measuring techniques, 149
role in pulmonary deposition,
114, 118-119
role in pulmonary effects, 132-
133
distribution, 58, 117
Pennsylvania communities
morbidity study, 167-168, 175
Philadelphia, Pennsylvania
economic effects of air pollution
in, 83
209
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Photochemical reaction model, 10
Photometry, 20
Photomicrographic atlas, 19
Physiological response, 132-134
Pittsburgh, Pennsylvania
economic survey of pollution
damage, 180
Plants
dust effects on, 89-93
Pneumocoiosis, 122, 131
Pneumonia
mortality, 157
Polynuclear aromatic hydrocarbons
carcinogenicity of, 137
Post office employees
morbidity studies, 163
Precipitation
influence of particulates on, 40-
42
Public opinion surveys, 99-102
Pulmonary flow resistance, 132-
134
Pulmonary function
alterations in, 132-134
R
Race
relationship to mortality, 156
Rainfall (See Precipitation)
Refinery
odors from, 107
Reflectance, 21
Reflectometer, 21
Respiratory illness
relation to smoke level, 148, 162-
167
Respiratory system
models of, 114-116
Respiratory tract
anatomy of, 111-112
Retention
human vs. animal respiratory
system, 119
respiratory system, 112-119
Rotterdam
morbidity study, 168, 175
Rusting, 65-69, 72-74
Salford, England
morbidity studies, 164
mortality studies, 158-159
Sampling methods, 17-23
Scattering coefficient, 55-58
Settling velocities, 16
Sewage
odors from, 107
Sex
relationship to mortality, 156
Sheffield, England
morbidity studies, 167, 168, 170,
174
Smoke
corrosive effects, 72-74
toxicity of, 150-154
Smoke plumes
optical properties of, 53
Smoke shade
correlation with mortality, 154
Smoking
cigarette, 137, 141, 149-150, 158,
161, 162, 163, 166
Sodium chloride
corrosive effects, 71
Solar radiation
effects of particulates on, 35-38
physical factors effecting, 38-39
seasonal variations, 39-40
weekly variations, 39
Soot
corrosive effects, 65-74
effects on textiles, 71-74
effects on vegetation, 89-94
Sorption properties, 8
St. Louis, Missouri
economic effects of pollution in,
83
public opinion survey, 99-100
Steel
corrosion of, 65-69, 72-74
Stokes law, 5-6
Sulfur dioxide
corrosive effects, 65
odor, 107
toxicity of, 130-131, 132, 136-137
Sulfuric acid
effects on vegetation, 94
Sulfuric acid manufacturing
emissions from, 24
Supersaturation
nuclei, 23
Surface coatings
deterioration of, 69-71, 72-74
Surface properties, 8-9
Surveys of damage, 79-84
Suspended particulate
means for urban areas, 11, 13-16
Synergistic effects
gases and particulate, 135
Synthetic textiles
soiling and deterioration of, 71-
74
Syracuse, New York
economic effects of air pollution
in, 83
Tape samplers, 20-22
Telephone workmen
morbidity studies, 162, 163
Tetrahydro naphthalene
toxicity, 131
Textiles
soiling and deterioration of, 71-
74
Toxicity
adsorbed substances, 130
intrinsic of particulates, 129-130
reduction of, 130-131
Transmissivity
variation with climate, 36
Transmittance, 20-21
Trees
dust effects on, 90-92
Triphenyl phosphate
deposition, 117
Turbidimetry, 19
Turbidity, 37
U
Upper Ohio River Valley
economic survey of pollution
damage, 81, 82
Varnished surfaces
deterioration of, 69-71, 72-74
Vegetables
dust effects 'on, 89-96
Visibility, 51-61
effect of fog upon, 53-54
effects of natural aerosols on, 53
effects of particulates on, 36-38,
53-53
Volatile particles, 106
W
Washington, D.C. (Suburban)
economic effects of air pollution,
83
Waste decomposition
odors from, 107
Wool
soiling and deterioration of, 71-
74
X-ray diffraction, 19
Z
Zinc
corrosion of, 66, 67-68, 72-74
Zinc dust
effect on textiles, 72
Zinc salts
corrosive effects, 71
210
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ACKNOWLEDGEMENTS
The following sources, in most instances
the copyright holders, have granted permis-
sion to the National Air Pollution Control
Administration to include the following fig-
ures and tables in the Air Quality Criteria:
Table 1-1.—Los Angeles data courtesy of Los
Angeles County Air Pollution Control Dis-
trict
Table p. 26.—Chemical Processing Engineer-
ing, London
Table p. 27.—American Society of Mechani-
cal Engineers, New York, N. Y.
Table 2-2.—The Gray Printing- Company,
DuBois, Pennsylvania
Tables 3-1, 8-1.—Air Pollution Control As-
sociation, Pittsburgh, Pa.
Table 3-2.—Reinhold Book Corporation, New
York, N. Y.
Table 4-1.—Iron and Steel Institute, London
Tables 4-2, 4-3.—American Society for Test-
ing & Materials, Philadelphia, Pa.
Table 5-1.—Mellon Institute, Pittsburgh, Pa.
Table 10-2.—American Industrial Hygiene
Association, Detroit, Mich.
Tables 10-3, 10-4, 11-2, 11-3, 11-4.—Ameri-
can Medical Association, Chicago, 111.
Table 10-5.—American Association for the
Advancement of Science, Washington, D.C.
Table 10-6.—National Tuberculosis & Res-
piratory Disease Association, New York,
N. Y.
Table 11-1.—Pergamon Press, Inc., New
York, N. Y.
Figure 1-1.—Academic Press, Inc., New
York, N. Y.
Figures 1-3, 2-2, 3-1, 3-4, 3-5, 3-6, 9-4, 9-5,
9-6, 9-7.—Pergamon Press Inc., New
York, N. Y.
Figure 1-4.—American Industrial Hygiene
Association, Detroit, Mich.
Figures 2-1, 3-7, 7-2.—Air Pollution Control
Association, Pittsburgh, Pa.
Figures 2-3, 2-4,11-2.—Controller, Her Maj-
esty's Stationary Office, London, England
Figures 2-5, 3-1, 3-3.—American Meteoro-
logical Society, Boston, Mass.
Figure 3-8.—American Chemical Society,
Washington, D. C.
Figure 4-1.—Iron and Steel Institute, Lon-
don, England
Fiyuio 4-2.—American Society for Testing
& Materials, Philadelphia, Pa.
Figure 4-3.—District of Columbia Health
Department, Washington, D. C.
Figure 5-1.—Environmental Health & Safety
Research Associates, New Rochelle, New
York
Figures 6-1, 6-2, 6-3.—Ellis F. Darley, Uni-
versity of California, Riverside, Calif.
Figure 11-1.—Royal Society of Health, Lon-
don, England
Figure 11-3.—Royal Dublin Society, Dublin,
Ireland
Figure 11-7.—American Medical Associa-
tion, Chicago, 111.
Figure 11-8.—British Medical Journal, Lon-
don, England
4 U. S. GOVERNMENT PRINTING OFFICE : 1 969—347-lfl 1/32
211
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