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AIR POLLUTION ASPECTS
OF
BIOLOGICAL AEROSOLS
(MICROORGANISMS)
Prepared for the
National Air Pollution Control Administration
Consumer Protection & Environmental Health Services
Department of Health, Education, and Welfare
(Contract No. PH-22-68-25)
Compiled by Harold Finkelstein, Ph.D.
Litton Systems, Inc.
Environmental Systems Division
7300 Pearl Street
Bethesda, Maryland 20014
September 1969
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ABSTRACT
Biological aerosols—suspensions of microorganisms in
the air—can cause diseases in humans, animals, and plants
and degradation of inanimate materials. Several typical air-
borne infections of humans include tuberculosis, pneumonia,
the common cold, and influenza. In addition, there is evi-
dence that biological aerosols and nonbiological air pollu-
tants may act synergistically to produce harmful effects.
Some airborne diseases of animals are tuberculosis, hog
cholera, and Newcastle disease. Plants are susceptible to
airborne pathogens that cause such diseases as wheat rust,
potato blight, and almond brown rot. Organic constituents of
protective paint coatings and other inanimate surfaces are
subject to microbial attack and damage. The present know-
ledge pertaining to the relationships between dose-effect,
viability, survival of microorganisms in aerosols, and other
factors is insufficient for establishing standards for either
indoor or outdoor environmental air concentrations.
The source of most human and animal airborne pathogens
is the host organism that recently harbored the pathogens.
However, since biological aerosols generally are detrimentally
affected by exposure to the atmosphere, they are usually found
in spaces close to the host. However, certain plant pathogens
are more resistant to the atmospheric environment, and these
are often rapidly dispersed hundreds of miles by air within a
few days.
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The abatement and control of biological aerosols have
been successful only in environmentally-controlled indoor
spaces. There has been no adequate way to estimate either
the cost of the effects of biological aerosols, or the cost
of abatement and control.
The available methods of analysis for biological aero-
sols tend to be specialized according to atmospheric condi-
tions, biological types, and particle size; consequently,
many different individual sampling devices are used.
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CONTENTS
FOREWORD
ABSTRACT
1. INTRODUCTION 1
2. EFFECTS 3
2.1 Effects on Humans 3
2.1.1 Airborne Diseases 3
2.1.1.1 Bacterial Diseases 3
2.1.1.2 Fungal Diseases 4
2.1.1.3 Viral Diseases 4
2.1.1.4 Hypersensitivity Reactions .... 6
2.1.2 Synergistic Effects 6
2.2 Effects on Animals 10
2.2.1 Commercial and Domestic Animals 10
2.2.1.1 Bacterial Diseases 10
2.2.1.2 Fungal Diseases 10
2.2.1.3 Viral Diseases 11
2.2.2 Experimental Animals 11
2.2.2.1 General Experiments 12
2.2.2.2 Synergistic Experiments 12
2.3 Effects on Plants 15
2.4 Effects on Materials 15
2.5 Environmental Air Standards 16
3. SOURCES 17
3.1 Natural Occurrence 17
3.2 Production Sources 18
3.3 Product Sources 26
3.4 Environmental Air Concentrations 26
4. ABATEMENT 3!
5. ECONOMICS 40
6. METHODS OF ANALYSIS 44
7. SUMMARY AND CONCLUSIONS 47
REFERENCES
APPENDIX
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LIST OF FIGURES
1. Daily Bacterial Counts in Urban Area 62
2. Hourly Bacterial Counts in Nonurban Area .... 62
3. Airborne Organisms in a Surgery Room 63
4. Effect of Distance Downwind of Treatment Unit . . 64
5. Relative Position of Filter and Blower to
Confine Contamination Inside or Outside Room . . 65
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LIST OF TABLES
1. Age-Standardized Inception Rates of Incapacity
Among Men in Three Different Occupational Groups . . 9
2. Isolation of Cryptococcus Neoformans 21
3. Bacteria in Air in New York City, January-June
1936 „ 28
4. Average Number of Alternaria Spores at One Site
in Manhattan, Kansas ° ° 29
5. Room Contamination in Organisms per Cubic Foot
at End of One Hour and at Steady State 36
6. Resource Costs of Diseases Associated with Air
Pollution . . . . o 41
7. Common Airborne Bacterial Infections of Humans ... 66
8. Common Airborne Fungal Infections of Humans .... 70
9. Viral and Related Agents Presently Recognized
as the Cause of Human Respiratory Diseases 72
10. Possible Airborne Virus Diseases of Animals .... 75
11. Common Laboratory Animals Used in Studies of
Airborne Disease 76
12. Average Micropopulation per Cubic Meter Found
Simultaneously During 30-Hour Sampling Mission ... 77
13. Quantitative Results from the Balloon-Borne
Direct-Flow Samplers 77
14. Air Dispersion of Small Organisms 78
15. Recommended Conditions for Use of Common Germicidal
Substances at Room Temperature (25°C) ..<><>... 81
16. Mathematical Model on Hospital Ventilation „ . . 0 . 82
17. Roughing Filters o .... o ... 0 o . 0 84
18. Medium-Efficiency Filters 85
19. High-Efficiency Filters 87
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LIST OF TABLES (Continued)
20. Ultra-High Efficiency Filters 89
21. Penetration of Tl Phage and Bacterial Aerosols
Through Commercial Air Filters 91
22. Effect of Eradicant Fungicides on Sporodochia
Production, Conidial Germination, and Blossom
Blight Caused by Monillia Laxa on Drake Almond,
1958 93
23. Tuberculosis Hospital Use 94
24. Death Rate for the 10 Leading Causes of Death,
1966 „ . . . o . . 95
25. Death Rate (1950 to 1966) and Deaths (1965 and
1966) from Selected Causes 95
26. Specified Reportable Diseases: Cases Reported,
1945-1966 ......... o 96
27. Respiratory Diseases in the United States, July
1966-June 1967 97
28. Age-Specific Disease Rates per 100,000 Population
per Year, 1959-61 98
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1. INTRODUCTION
Biological aerosols are defined as biological contam-
inants occurring as solid or liquid particles in the air.
These particles can vary in size from virus units of less than
0.1 (a* to fungal spores of 100 |a or larger. The particles may
occur as single, unattached organisms or as aggregates of or-
ganisms. They may also adhere to a dust particle or be sur-
rounded by a film of dried organic or inorganic material.
Viable microorganisms are known to occur up to an altitude of
about 20 miles, and fungal spores have been found in air flights
over the North Pole. For the purpose of this report, emphasis
will be on those micoorganisms occurring as aerosols that can
be pathogenic for humans, animals, and plants and can cause
damage to inanimate materials. The microorganisms (microbes)
generally involved are bacteria, fungi (yeasts and molds), and
viruses. Other microorganisms—such as algae, protozoa, and
rickettsiae—generally do not cause disease by transmission as
aerosols. Some fungi have been implicated in hypersensitivity
(allergic) reactions in humans, but this subject is discussed
in a separate report of this series, "Air Pollution Aspects of
Aeroallergens."
The importance of disease transmission by biological
aerosols has been in part a function of urbanization. Because
microorganisms do not generally survive very long as aerosols,
* i \
|j=micront s;.
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airborne transmission of human and animal diseases is limited
to indoor or crowded outdoor spaces. The appearance of crowded
cities in what had been primarily a low population-density
agricultural society for the previous 1,000 years was a contri-
buting factor in the plague epidemic of 1348. Since then,
respiratory diseases have been correlated with the extent of
crowded conditions in the cities. Although progress in modern
medicine dramatically decreased the potential mortality rate
during the influenza pandemic of 1968, the incidence of the
disease demonstrated that we are far from an adequate control
of such diseases.
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2. EFFECTS
Biological aerosols have been shown to produce diseases
in humans, animals, and plants and microbial degradation of
inanimate materials. When airborne dissemination is involved
in transmission of diseases, the actual number of microorganisms
dispersed by the host is relatively small, and if dispersed
into the open air, the living organisms represent a very small
fraction of the total ambient air. These pathogenic micro-
organisms cannot reproduce in the air and generally do not sur-
vive long because of adverse conditions of humidity, temperature,
and sunlight. Airborne transmission of human and animal patho-
gens is therefore essentially limited to indoor spaces or to
closely confined outdoor spaces. The general exceptions to
this fact are certain microorganisms that multiply saprophyt-
ically in the soil and can be pathogenic to humans and animals.
These microorganisms are not dependent upon a host reservoir
for survival and can be more widely dispersed by air. In
general, the symptoms produced by airborne infectious agents
are those of a respiratory disease, but transmission often can
be by other means and results in symptoms other than respiratory
ones.
2.1 Effects on Humans
2.1.1 Airborne Diseases
2.1.1.1 Bacterial Diseases
The most common airborne bacterial infections of humans
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are the following:12'17'38'95'105'112'114
Pulmonary tuberculosis
Pulmonary anthrax
Staphylococcal respiratory infection
Streptococcal respiratory infection
Meningococcal infection
Pneumococcal pneumonia
Pneumonic plague
Whooping cough
Diphtheria
Klebsiella respiratory infection
Staphylococcal wound infection
The causative agent and the symptoms of each of these diseases
are presented in Table 7 in the Appendix.
2.1.1.2 Fungal Diseases
The most common airborne fungal infections of humans are
the following:12'17'38'95'105'112'114
Aspergillosis
Blastomycosis
Coccidioidomycosis
Cryptococcosis
Histoplasmosis
Nocardiosis
The causative agent and symptoms of each of these diseases are
presented in Table 8 in the Appendix.
2.1.1.3 Viral Diseases
The most common airborne viral respiratory diseases of
humans are these:12'17'38.51,91,95,105,112,114
Influenza
Febrile pharyngitis or tonsillitis
Common coId
Croup
Bronchitis
Bronchiolitis
Pneumonia
Febrile sore throat
Pleurodynia
Psittacosis
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More than 90 viral agents have been identified as the etio-
logical factor in respiratory tract illnesses. Others remain
yet unrecognized by present laboratory techniques, which at
best identify the causative viral agent in only 50 to 60 per-
cent of respiratory infections. Table 9 (Appendix) lists the
names of the viral, the one rickettsial (Q-fever),64/113
and related diseases in which airborne transmission is primarily
involved.
In addition to those diseases listed in Table 9, several
viral diseases in which airborne transmission is at least
partly involved produce symptoms other than respiratory ones.
These are as follows:17'91'105'112
Mumps is a swelling and tenderness of the parotid glands
that is sometimes accompanied by orchitis.
Rubella (German measles) is a mild exanthematous disease
of childhood resembling measles. However, its occurrence in
women during the early months of pregnancy is associated with
a high incidence of congenital malformations.
Rubeola (measles) is the commonest disease of childhood.
The median number of cases reported per year ,in this country
exceeds half a million. Rubeola is characterized by a cough
and fever and a macular or maculopapular rash tending to become
confluent.
The transmission of several other viral diseases can be due
in part to airborne contaminated dust and skin scales: ''91'105
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Variola (smallpox) is characterized by vesicles over
most of the skin surfaces. Although it is endemic elsewhere
in the world, no confirmed cases have been reported in this
country since 1954.
Varicella (chickenpox) is a common, highly contagious,
exanthematous disease of childhood that occurs in epidemic
form.
Herpes zoster (shingles) is similar to varicella but
occurs more frequently in adults.
2.1.1.4 Hypersensitivity Reactions
A number of fungi, and possibly algae as well, have
been implicated in hypersensitivity (allergic) reactions in
humans. Evidence has been presented in recent years that
the symptoms of such diseases as farmer's lung, mushroom
lung, and other diseases formerly considered to be infectious
were the results of hypersensitivity responses. These
syndromes will not be discussed in this report but are in-
cluded in another report in this series, "Air Pollution Aspects
of Aeroallergens. "
2.1.2 Synergistic Effects
As modern air pollution information has accumulated,
it has become apparent that increases in respiratory infection
morbidity and mortality of the exposed population may be re-
lated to excessively high levels of nonbiological air pol-
lutants. That is, the two types of pollutants—biological and
nonbiological—may produce synergistic or potentiating effects.
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However, as so often in the study of natural human infections,
one is limited to conclusions based upon medical statistics
on uncontrolled events and situations. The number of model
situations in which high levels of air pollution were ac-
companied by marked increases in respiratory disease morbidity
and mortality .and adverse weather conditions has been limited.
Conditions in the laboratory with experimental animals are
subject to better control, but there are, nevertheless,
limitations in applying results to human disease processes.
Several reports are available on the potentiation of
air pollution and influenza. Both high levels of air pollution
and influenza occurred in London in December 1952 in which
4,000 deaths occurred,73'87 and again in 1958 to 1959.65 The
observations indicated a parallel correlation between the
increase in air pollution and an increase in the disease.
Greenburg et al.,44 in a study of pediatric and adult clinic
visits, found an increase in upper respiratory illness during
the New York City air pollution incident of November 1953.
They investigated the influenza epidemic in New York City
during the fall of 1957 but could not ascertain quantitative
relationships between air pollution and influenza.45 However,
during the period of January 29 to February 12, 1963, another
occurrence of influenza in New York City did show a correlation
with air pollution. During this period, 809 deaths occurred
in excess of the overall average number of deaths for the
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8
same 15-day periods in 1961, 1962, 1964, and 1965. This in-
crease in mortality took place primarily in the older age
groups—45 to 64, and 65 and over.45 Dohan25 reported a de-
crease in respiratory illnesses in Pittsburgh in the years
following the intensive efforts to control air pollution.
Douglas and Waller26 in 1966 reported on a study of a
group of schoolchildren performed as part of the National
Survey of Health and Development in Great Britain. The pur-
pose of the study was to examine the relationship between
respiratory infections and prolonged exposure in areas of
high and low air pollution. Douglas and Waller followed the
medical histories of 5,362 children born during the first
week of March 1946 until they reached the age of 15 in 1961.
At that time 4,592 were still living in Great Britain, and
complete medical records were available for 3,866. The in-
vestigators concluded that upper respiratory tract infections
were not related to the amount of air pollution, but that lower
respiratory tract infections were. Also, the frequency and
severity of the lower respiratory tract infections increased
with the amount of air pollution exposure, and both boys and
girls were affected equally. An association between lower
respiratory tract infection and air pollution was found at
each age examined (6,7,11, and 15 years). There were no dif-
ferences observed between children in middle- and working-class
families.
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Lunn et al.63 collected respiratory illness data on
819 schoolchildren between 5 and 6 years old who had lived in
the Sheffield area most of their lives. These investigators
reported a relationship between both upper and lower res-
piratory illnesses and air pollution. However, socioeconomic
factors—such as social class, number of children in the house, and
and sharing of bedrooms—appeared to have little influence upon
the respiratory illnesses among the children.
Alderson2 presented data from the British Ministry of
Pensions and National Insurance which showed that different
illness patterns existed among individuals of three occupations.
Coal miners had more respiratory illnesses than professional
and technical personnel, who in turn had more than agricul-
tural workers. The illness patterns are presented in part in
Table 1.
The results of animal experiments in relation to
synergistic effects are discussed in Section 2.2.2, Experi-
mental Animals.
TABLE 1
AGE-STANDARDIZED INCEPTION RATES OF INCAPACITY AMONG
MEN IN THREE DIFFERENT OCCUPATIONAL GROUPS2
Diagnosis
Acute upper
respiratory
infection
Influenza
Bronchitis
Men Incapacitated per 100 at Risk
Agricultural
Workers
40
60
47
Coal Miners,
Face Workers
284
234
205
Professional and
Technical Personnel
87
80
51
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2.2 Effects on Animals
2.2.1 Commercial and Domestic Animals
Few diseases of commercial and domestic animals can be
attributed to airborne aerosols. Most animal diseases are
transmitted by contact by insect bites, and through ingestion
of contaminated food and water.
2.2.1.1 Bacterial Diseases
Two bacterial airborne diseases of animals are tuber-
culosis (Mycobacterium bovis) of cattle, swine, sheep, dogs,
and cats, the control of which in the United States has been
by slaughter; and glanders (Actinobacillus (Malleomyces) mallei),
a tuberculosis-like, high-mortality disease of horses, mules,
and asses.11'69'70
2.2.1.2 Fungal Diseases
Several fungal diseases of animals that may possibly be
J.-U * i-i 11,69,70
airborne are the following:
Aspergillosis occurs in domesticated birds, pigeons,
ducks, and chickens. It can occur as a superficial infection
of the air sacs, which become covered with a mat of green
mycelium; a nodular tubercle-like mass; or a diffusely infil-
trated pneumonic infection of the lung. In chicks, an epidemic
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11
form is known as "brooder pneumonia," the source being inhala-
tion of grain and straw heavily contaminated with mold. A
nodular or pneumonic form can occur also in cattle and sheep,
and especially in horses.
Cryptococcosis can occur in the lungs of horses and
result in granulomas. Emmons35 found virulent strains of
Cryptococcus neoformans in pigeon manure. It has also been
described as the etiological agent in a severe outbreak of
bovine mastitis.12
Coccidioidomycosis is endemic in areas of the South-
west United States. It occurs naturally in domestic animals,
including cattle, horses, sheep, swine, and dogs, and also
in certain wild rodents (pocket mouse, kangaroo rat, and
grasshopper mouse).
2.2.1.3 Viral Diseases
The most common viral diseases of animals are as
follows:11'69'70
Hog cholera
Equine influenza
Swine influenza
Feline distemper
Canine distemper
Newcastle disease
Infectious bronchitis
The symptoms of these diseases are presented in Table
10 in the Appendix.
2.2.2 Experimental Animals
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2.2.2.1 General Experiments
Table 11 (Appendix) lists the airborne bacterial and
fungal diseases and the common laboratory animals which have
been used in aerosol studies. However, the use of laboratory
animals—mice, rabbits, guinea pigs, and monkeys—has generally
been limited in virus aerosol studies because of the specific
host-parasite relationship of viruses.
2.2.2.2 Synergistic Experiments
Because of the difficulties in studying the potential
synergistic effects of nonbiological and biological air
pollutants on humans, many experiments have been made using
experimental animals exposed to mixtures of artificially pro-
duced aerosols under the relatively controlled conditions of
the laboratory.
Miller and Ehrlich studied the effect of ozone on
susceptibility to respiratory infection in mice exposed to
aerosols of Klebsiella pneumoniae and various streptococcus
species. The mice were also exposed to ozone concentrations
of 0.4 to 4.4 ppm for periods ranging from 3 to 100 hours.
The time between ozone exposure and subsequent aerosol exposure
or challenge was 1 hour. Exposure to ozone significantly
reduced resistance to infection as measured by mortality rate
QQ
and survival time. In a later study, it was found that the
mice's resistance was reduced for as long as 19 hours between
ozone exposure and aerosol challenge. Coffin and Blommer15
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13
reported that exposure to 0.7 to 0.9 ppm ozone for 2 hours
enhanced mortality to streptococcal pneumonia in mice. The
exposure to the streptococcal aerosol occurred 30 minutes
following the ozone. The mortality rate was further enhanced
by exposure of the mice to a cold temperature (6 to 9° C) for
3 hours prior to the ozone and streptococcus aerosol. The
authors believed that the effect of the cold temperature was
to potentiate the ozone effect. Thienes et al. were un-
able to demonstrate a potentiation effect between ozone and
tuberculosis in mice.
Ehrlich^ has reviewed the effects of nitrogen dioxide
(N02) on the resistance of laboratory animals to K. pneumoniae
infections. A single 2-hour exposure of mice to 3.5 ppm of
nitrogen dioxide before or after respiratory challenge with
aerosol of f\. pneumoniae significantly increased mortality.
To produce the same effects in hamsters and squirrel monkeys,
35 ppm was required. The effect of the single 2-hour exposure
was not persistent, and it was observed that normal resistance
to the infection returned within 24 hours after cessation of
the exposure to nitrogen dioxide. Continuous exposures to
0.5 ppm for 3 months or longer, as well as intermittent daily
exposures over a 30-day period, produced the same effect in
mice as the single 2-hour exposure to 3.5 ppm. Intermittent
exposure of mice to 0.5 ppm for 6 to 18 hours per day for 6
33
months also resulted in a significantly increased mortality.
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Henry et al.49 in studying the combined effects of
nitrogen dioxide and K. pneumoniae microorganisms on squirrel
monkeys, reported that a combined stress of 50 ppm N02 and
104 cells of K. pneumoniae—neither in itself fatal—produced
death. At N02 concentrations of 35 ppm or less, death did
not occur, but bacterial clearance from the lungs was delayed
or prevented. Monkeys exposed only to the challenge dosage of
K. pneumoniae showed no bacteria in their lungs 15 to 57 days
following challenge. However, if preceded with 10 ppm NO,,
^
K. pneumoniae could be found in the lungs 19 to 51 days later.
Coffin and Blommer1 have reported results indicating
that light-irradiated automobile engine exhaust enhanced the
pneumonia mortality rate of mice exposed to a streptococcal
aerosol.
t
Inert dust particles have been reported to potentiate
infections in laboratory animals. Tacquet1 observed an
increase in pathogenicity and in the number of mycobacteria
isolated from the lungs of guinea pigs following inhalation
61
of inert carbon dust. Laurenzi x reported that the natural
clearance of aerosolized staphylococci from the lungs of mice
was impaired by inhalation of cigarette smoke or intraperitoneal
40
injections of ethyl alcohol. Green and Kass have made similar
observations.
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2.3 Effects on Plants
Plants are susceptible to bacterial, fungal, and viral
diseases. Some of these diseases are disseminated by means of
insects, birds, animals, or water; but many—primarily the
fungi—are subject to airborne dispersal. The following is
a list of such, airborne plant diseases:3'14'22'90'124'129
Almond brown rot
Azalea flower spot
Beet downy mildew
Blossom infection
Cedar rust
Apple rust
Chestnut blight
Crown rust of oats
Downy mildew
Leaf spots on tulips
Loose smut of wheat
Maize rust
Onion mildew
Potato late blight
Powdery mildew on barley
Stem rust of wheat and rye
Tobacco blue mold
White pine blister rust
2.4 Effects on Materials
Microorganisms are essential in normal decay processes.
Therefore, all material surfaces in contact with the air are
theoretically subject in some degree to microbial degradation
by saprophytic microorganisms. The most obvious general
example of this is food spoilage, a continual problem. The
magnitude of this problem is related to the local climate:
maximum spoilage occurs in a-hot, humid climate and minimum
spoilage in a cold, dry climate.
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Saprophytic fungi can grow on the surfaces of many
inanimate materials where there is high humidity- The or-
ganisms may utilize either the coating or the underlying
surface as food, and may produce corrosive acid or alkali
wastes as a result of their metabolic processes. These wastes
may in turn attack the surfaces on which they are growing.
For example, the modern field of miniaturized electronics is
faced with this problem: the miniaturized circuits, unless
protected by varnishes containing fungicides, can be damaged
by the growth of fungi. Larsen60 in 1957 pointed out that
organic constituents of protective paint coatings may be
subject to microbial attack and damage.
2.5 Environmental Air Standards
There are no environmental air standards applicable to
biological aerosols at the present time. Current knowledge
pertaining to the relationship between dose-effect, viability,
survival of microorganisms in aerosols, sampling procedures,
and aerosol production is insufficient for establishing stand-
ards for either indoor or outdoor environmental air concentra-
tions.
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3. SOURCES
3.1 Natural Occurrence
Microorganisms are ubiquitous in nature. However, all
microorganisms found in the air had as their original habitat
either soil, water, humans, animals, or plants. Microorgan-
isms become airborne from the soil and from plants by wind
disturbances, and from water by wave and wind action. They
come from animals through shedding, excreta, and respiratory
droplets, and from humans through shedding from skin and
clothing and through respiratory droplets produced by speech,
coughing, and sneezing. Some types of organisms are more
plentiful in the air than others, because of their size
(i.e., they are small enough to remain airborne), the magni-
tude of the emission source, the death rate of organisms sus-
pended in the air,- and other factors. Microorganisms have
been found at various altitudes. Fulton39 in sampling the
air above San Antonio, reported average peak concentrations
of 250, 75, and 35 microorganisms per cubic meter at 690,
1,600, and 3,127 meters' altitude respectively (Table 12,
Appendix) . Microorganisms have also been recovered in balloon
flights up to 90,000 ft.10 (Table 13, Appendix).
Most of the microorganisms found in the air are
saprophytic and generally are not pathogenic. Those which are
pathogenic, with some exceptions, come from a living host.
Since they are usually detrimentally affected by exposure to
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18
the atmosphere, they are only found in close proximity to the
host. However, certain plant pathogens can have rapid and wide-
spread aerial dispersal over hundreds of miles within a few
days.I0?
The survival of biological aerosols has been studied
rather intensively in recent years, primarily in laboratory
studies. Most of these studies have been concerned with
bacteria, and relatively little is known of the behavior of
viruses and fungi. No simple relationship has been found
between the degree of survival and age of the aerosol. The
half-life of the aerosol is affected by such variable factors
as the species of microorganisms (spore-former or non-spore-
former); metabolic state of the microorganism; the relative
humidity, gaseous composition, and temperature of the air;
radiation; collection method; and others. Because of the
large number of these variables and their interrelationship,
both the results and the interpretations of aerosol survival
studies are markedly dependent upon the precise technique
employed.^
3.2 Production Sources
The spread of influenza, the common cold, and other such
diseases in the home, office, or schoolroom is readily apparent.
Similar disease transmission takes place in hospitals as well.
For example, the spread of staphylococcal infections in hospi-
tals has been a considerable problem. Staphylocoecus aureus
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19
is commonly found in the normal nasal flora of 30 to 50 per-
cent of healthy adults (carriers). Studies on nasal car-
riers showed that while direct dispersal did not take place to
any great extent under normal conditions, large numbers of
infectious airborne particles might be produced by active
movements. The bedclothing of carriers also becomes rapidly
infected.77-96 Wilkoff et al.125 studied the viability of
Staphylococcus aureus dispersed by aerosol on various fabrics
(wool blanket, wool abardine, cotton sheeting, cotton knit
jersey, cotton terry cloth, and cotton wash-and-wear material).
He found that staphylococcal populations persisted long enough
(4 to 24 weeks) to be of epidemiological importance. Davies
91
and Noble observed under a microscope that airborne parti-
cles from a hospital ward included many skin scales containing
staphylococci. In addition, they found that the skin scales
and bacterial content of the air rose significantly during bed-
making .
Eichenwald et al.34 have described a direct dispersal
of smaller than normal (< 5 |j) particles containing staphylococci
from the upper respiratory tract of newborn infants in a nurs-
ery. These "cloud babies" had a respiratory virus infection
and, apparently because of the slightly restricted air passages,
were producing "clouds" of staphylococci. Staphylococci
are commonly found on the healthy skin and, therefore, skin
desquamation is an important source of hospital staphylococci.
Some individuals are prolific dispersers.
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20
Airborne dust containing streptococci has been found
in hospital wards containing patients with streptococcal in-
fections. M. tuberculosis has also been found in the dust
of sanitariums, and the diphtheria organism in floor dust near
diphtheria patients.114
Gip was able to isolate airborne dermatophytes from
a commercial bathhouse, a dressing room in an automobile fac-
tory, and a hospital, as well as in a gymnasium during a
basketball game. However, the role of such isolated derma-
tophytes as exogenous agents of fungus infection is still
open to question.
Procknow in 1967 reported isolating Histoplasma
capsulatum annually for 15 years from the dust of an unused
silo. At the time of its abandonment in 1950, the silo was
the source of histoplasmosis contracted by a farm family of six.
Emmons36 was able to isolate H. _capsulatum from all 10
soil samples collected in a downtown park in Washington, B.C.
He attributed the presence of the fungus to droppings from
starlings roosting in trees.
D'Alessio20 reported an urban epidemic of histoplasmosis
which occurred in Mason City, Iowa, in 1962. The source of
the fungus, proved by the recovery of the organism from the
soil, was a starling roost in the center of town. The airborne
epidemic had occurred after bulldozing of vegetation in the
area had produced clouds of dust. It was concluded that about
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21
2,400 schoolchildren and about 6,000 adults had been infected
during the epidemic.
Virulent strains of Cryptococcus neoformans have been
found in pigeon manure in old pigeon nests and under roosting
35
sites. The organism was isolated from 63 of 91 specimens
obtained in arid around Washington, B.C. (Table 2).
TABLE 2
ISOLATION OF CSYPTOCOCCUS NEOFORMANS
35
Sources of Collection
Warehouse, former barn
Old school building, now offices
Grain mill establishment
Cupola on high school building
Window ledges, Federal and municipal
office buildings
Public parks
Railroad station
Barns (Virginia and Maryland)
Total
Number of
Specimens
Collected
15
10
5
7
18
7
4
25_
91
Number of
Specimens
Positive
14
7
3
7
17
0
1
14
63
Wells,-^l in the 1930's, concluded from his studies that
bacterial contamination of air by sewage works existed and that
organisms causing respiratory diseases could remain airborne
and viable for long periods of time. Randall and Ledbetter89
sampled the air of an activated sludge sewage treatment unit
and found that 6 percent of all bacteria emitted by the waste
liquid were of the Klebsiella species, potential respiratory
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22
tract pathogens. About 40 percent of the viable airborne
bacteria in the immediate vicinity of the activated sludge
units were of a size that permits lung penetration (5 |a or
less). The bacterial population persisted for a considerable
time and distance (the farthest sampling point being at 100
feet); the distance was strongly dependent on the wind velocity.
76
Napolitano and Rowe sampled the air of sewage treat-
ment plants and found that in one plant, the unit discharging
most organisms was the aeration tank. In a second plant,
the comparable units were the trickling filters. Emitted
bacteria were found at the farthest sampling point, 150 feet
downwind of the unit. The investigators did not attempt to
isolate pathogens per se.
Albrecht demonstrated that the distance traveled and
the number of bacteria found downwind of a trickling filter
were correlated directly with the wind velocity. Jensen-^"
surmised from his studies that tuberculosis organisms could
become airborne from liquids in a sewage plant and were a
real danger to the operating and supervisory personnel of the
plant. Dixon and McCabe^4 attempted to determine whether the
incidence of infection in sewage plant workers had increased,
but the results were inconclusive because of incomplete em-
ployee medical records.
Spendlove10^a has studied the aerosol production in an
animal rendering plant. He painted slurries of harmless tracer
bacteria (a spore-former and a non-spore-former) onto the
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23
carcasses before the rendering process began, and later col-
lected air samples at various places inside and outside the
plant as processing proceeded. His results showed that the
rendering process in use created aerosols of viable micro-
organisms. Both the vegetative and spore-forming tracer or-
ganisms were found in air samples taken inside the plant and at
100 feet downwind from the exhaust stack. These findings
supported the suspicion that some of the workers in the plant
had become infected with ornithosis at an earlier date when
diseased turkeys had been processed. Other diseases which
potentially could have been transmitted by this rendering plant
include anthrax, brucellosis, tularemia, glanders, sylvatic
plaque, Q fever, and virus equine encephalitis. Tnis situation
was a health hazard both to the workers within the plant and
to the population in surrounding areas.
Many microorganisms—bacteria, yeasts, and molds—are
used in industrial fermentations to produce a number of econo-
mically important materials. The latter include butanol,
acetone, ethanol, vitamins 62 and B12,lactic acid, amylase,
dextran, diacetyl, acetic acid (vinegar), antibiotics, indus-
trial alcohols, beverage alcohols, citric acid, corticosterone,
and gibberellin, as well as dairy products such as butter,
I O QD
cheese, and various fermented milks. -3'0 However, even though
huge quantities of microorganisms are involved in the production
of these materials, no information was found on these fermentations
as a source of outdoor or indoor air pollution. Ashe has
-------
24
stated that to his knowledge, no industry has been reported to
produce a disease in the general population through air pol-
lution by living organisms.
Production of vast numbers of spores in periodic waves
is a characteristic of many fungi, and the retention of via-
bility is of fundamental importance, especially during pro-
longed air transport. High temperature, radiation, and low
humidities may have an adverse effect on spores of many of the
airborne fungi. Full sunlight is known to decrease the via-
bility of many plant pathogens. Failure to demonstrate
high germination rate may not be from lack of viability, but
from a lack of nutrient, ' or presence of inhibitors129
and factors still unknown.
Murrow et al. have summarized the most frequently
isolated molds from 41 sampling stations across the country-
No two stations had the same lists, but a basic group of
dominant genera appeared to occur. These were the following:
Alternaria
Homodendrum
Aspergillus
Penicillium
Pullularia
Phoma
Trichoderma
Fusarium
Helminthosporium
Cryptocoecus
Rhodotorula
Similar genera of fungi were observed in Tucson and
71 Al 30
Phoenix, Ariz., '^ in Albuquerque, N.Mex. and in Los
103
Angeles, Calif.
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25
Altman et al. have tabulated the observations of
many investigators on dispersal parameters of fungi pathogenic
for plants. Their tabulation is reproduced in part in Table
14 (Appendix).
The extent to which pathogenic fungi will spread is
dependent upon the occurrence of those particular conditions—of
humidity, temperature, winds, and presence of plant host—
that favor a particular disease. A classical example has
been described by Stakman and Harrar in which all conditions
were favorable for wheat rust disease. In 1935, spring was
late, and in northern Texas the rainfall was twice the normal
amount. Rust (Puccinia graminis tritici) developed quickly.
Spores of the fungus were blown northward and encountered
favorable conditions for development in the late crops of
Kansas and Nebraska. Furthermore, cold weather in May and
June had delayed the wheat crop in Minnesota and North and
South Dakota. The first half of July was still wet, but hot,
and when the masses os spores were blown into these fields
from Kansas and Nebraska, wheat rust developed in epidemic
proportions. It is estimated that 135 million bushels of
wheat were lost in Minnesota, North Dakota, and South Dakota
alone.
Species of algae and protozoa have been reported as
67 98 99
making up part of the aerial biota. ' ' Viable samples
have been obtained under extreme environmental conditions,
-------
26
including rain, heavy snow, and fog during fall, winter, and
9
spring. Brown et al. found that the quantity of algal cells
in the air exceeded that of mold spores. However, algal cells
have not been known to cause any infectious disease, and their
role as aeroallergens has yet to Joe definitely established.
3.3 Product Sources
Although large quantities of microorganisms are pro-
duced as a result of various industrial fermentations, Ashe
stated in 1959 that there has been no evidence so far that
this has resulted in a health hazard to the general popula-
tion. Except for the observations of Spendlove a (see
Section 3.2), no other information relating to this point has
been found in the literature.
3.4 Environmental Air Concentrations
It is not valid to present any one set of values for
the aerial microbial concentration of a given area, such as
a schoolroom or a playground. Any count is influenced by the
temperature, meteorological conditions, vegetation, human
and animal population, and time of day, as well as by the
inability to determine all types of microorganisms by any one
sampling procedure. With due consideration to the latter fact,
the following are some values which have been reported. Table
3 presents the bacterial counts of several areas obtained
127
in New York City in 1936. Figure 1 (Appendix) presents
mean counts of outside air obtained in Detroit for a 3-month
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27
127
period in 1953. Air samples collected during the winter
indicated a lower concentration of airborne bacterial particu-
lates than in the spring. Hourly fluctuation in counts for
air samples collected in an open field of a nonurban area in
Georgia in 1951 is shown in Figure 2 (Appendix). The fluctua-
tions in the number of airborne microorganisms in a surgery
room due to movement are presented in Figure 3 (Appendix).
Wright et al.^-27a have reported the results of a pilot
study to evaluate the types and number of viable microorganisms
present in the air of an urban area such as Minneapolis-St.
Paul. Air samples were obtained at four points (35, 70, 170,
and 500 feet) along a 500-foot television tower by means of
an Anderson sampler. Sampling was performed at intervals over
a 6-month period, and wind, rainfall, humidity, and temperature
conditions were recorded with each sample. The mean viable
counts were as follows:
58 particles per ft3 (2,047 per m3) at 35 ft
38.4 particles per ft3 (1,355 per m3) at 75 ft
32.7 particles per ft3 (1,155 per m3) at 170 ft
22.4 particles per ft3 (790 per m3) at 500 ft
The range of all counts observed was 3.5 particles per ft3
(123 per m3) to 141 particles per ft3 (4,977 per m3), with no
consistent relationships between the counts and any of the
meteorological parameters. Regardless of altitude, molds con-
stitued approximately 70 percent of the total airborne micro-
flora, bacteria between 19 and 26 percent, and yeast and
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28
actinomycetes the remainder. A significant portion of the
viable microorganisms in the air were in the particle size
range of 3 to 5 \i.
Microbial counts in nonurban areas are usually rela-
tively lower than in urban areas, and in both areas are
influenced primarily by the degree of activity and dust in the
immediate area as well as by seasonal and climatic conditions.
TABLE 3
BACTERIA IN AIR IN NEW YORK CITY, JANUARY-JUNE 1936127
Location
Indoor
Schools
Subway
Theater
(nonventilated)
Theater
(ventilated)
Outdoor
Streets
Park
No. of
Samples
707
290
104
149
143
13
No. of
Bacteria
per ft3
29.6
19.2
13.2
3.1
11.2
3.0
Nn . nf Si-r^n-t-nnnnr'i rx=T -F1-.3
All
Types
0.20
0.10
0.04
0.03
0.05
Beta
Hemolytic
0.01
0.0003
0.001
0.0005
0.0001
Alpha
Hemolytic
0.18
0.085
0.38
0.26
0.45
QQ
Randall and Ledbetter, ^ in sampling the air of an
activated sludge sewage treatment unit, found an increase from
about eight viable particles per cubic foot (283 particles per
cubic meter) on the upwind side to 1,170 per cubic foot (17,900
per cubic meter) on the downwind side. Figure 4 (Appendix)
shows the decrease in numbers with distance downwind from a
(~> J
treatment unit.
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29
The number of airborne fungi changes from season to
to season, from day to day, and even from hour to hour. Table
4 illustrates the average hourly fluctuation observed by
83,84
84
Pathak and Pady of Alternaria spores sampled in Manhattan,
Kansas. Some fungi appear to have a diurnal periodicity.
One explanation offered for the latter fact is that a single
crop of spores—of Cladosporium, for example—is produced per
24-hour period, maturing at night and ready to be released
just before daylight. Morning turbulence carrying the spores
into the air for a monitoring peak, e.g., 100 per cubic foot
(3,500 per cubic meter). Decreasing air turbulence later in
the day allows the spores to settle, producing a late after-
92
noon or early evening peak.
TABLE 4
AVERAGE NUMBER OF ALTERNARIA SPORES
AT ONE SITE IN MANHATTAN, KANSAS84
Time Number per Ft3
5 a.m. 12
6 7
7 9
9 13
11 16
1 p.m. 17
2 13
5 16
6 19
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30
Q p
Pady found fungus spores present in the atmosphere at
an elevation of 150 feet throughout the year at one site atop
a building in Manhattan, Kans., with peaks in July and August.
In summer the number varied from 50 to 700 particles per cubic
foot (1,765 to 24,700 per cubic meter), while in winter they
ranged from 5 to 20 per cubic foot (175 to 700 per cubic meter)
Cladosporium was present throughout the year, comprising the
bulk of the spores in summer.
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31
4. ABATEMENT
The problem of abatement and control of biological
aerosols and their effects is a most difficult one. In gen-
eral, knowledge is incomplete concerning the various parameters
of biological aerosol production, the survivial and transmission
of the aerosol, the sampling procedures, and other factors.
There are further complications when air is not the only route
by which a given pathogen is spread. It is often difficult
to decide just how and when some infections were acquired. In
addition, the quantitative nature of the dose-effect relation-
ship is influenced by both the host and the pathogen, as well
as by the possible synergistic relationships with other pol-
lutants.
The abatement of some diseases, such as influenza, is of
such complexity that some researchers believe that control will
be dependent upon individual protection by immunization.10^
However, attempts have been made to control airborne infections
1 9 "3
indoors by the use of ultraviolet light. Wells et al.
reported success in the control of a measles epidemic in Phila-
delphia in 1941 by irradiating the air of classrooms with
85
ultraviolet light. Perkins et al., however, found several
years later that similar attempts at irradiation of class-
room air did not reduce the incidence of measles. The early
success of Wells was attributed to the social structure of the
communities where ultraviolet light was used; apparently the
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32
transmission of measles took place primarily at school. In
later studies, Wells and Holla122 and Wells121 attempted to
approach the broad problem of airborne infections on a
community-wide basis. They attempted to irradiate with ultra-
violet light the air of public buildings—schools, churches, a
theater, clubs, certain stores, and other places where children
gathered—in Pleasantville, N.Y. A neighboring community
served as a control. The results after 4 years showed that the
irradiation had little effect upon the total incidence of air-
borne infections. In another study, however, ultraviolet light
was used successfully to control influenza in a hospital build-
ing. One building was irradiated while a similar building
was not. No attempt was made to control the hospital staff
working in the two buildings. After 8^ months in 1957 to 1958,
2 percent of the 209 patients in the irradiated group had con-
tracted influenza as compared to 19 percent of the 396 patients
in the control group. Ultraviolet irradiation has also been
used successfully in special situations, such as above a surgery
table.
The control of hospital-acquired infections, especially
staphylococcal infections, has become a problem of considerable
magnitude. There is evidence that suggests that the inhalation
of airborne bacteria in dust has a greater quantitative effect
than inhalation of directly expelled particles in producing
disease.12 Therefore, control measures directed toward the
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33
suppression of dust have been employed, such as use of particle-
retaining oils on blankets and floors in hospitals. In addition,
the use of residual disinfectants, more frequent changes of bed
coverings, and the use of different fabrics have helped control
transmission.
10 9
Selwyn found that for those spreading staphylococcal
organisms, treatment of the skin with antibiotics greatly re-
duced both dispersal of staphylococci and the risks of acquisi-
tion of the organisms by new patients. Solberg106 found the
same to be true for nasal carriers in hospital wards. Washing
the skin with hexachlorophene-containing soaps also reduced
skin dispersal of staphylococci.
The use of disinfectants to control undesirable micro-
organisms in hospitals and elsewhere is common. However,
the disinfectants must be correctly used. Table 15 in the
Appendix, from Jemski and Phillips, 4 lists some common germi-
cides and conditions for their use.
High-speed photography has dramatically demonstrated the
value of surgical masks in reducing the number of particles
emitted during a sneeze. However, to minimize discomfort in
wearing them and to improve retention efficiency, newer
masks are being developed and tested. Guyton and Deker47 tested
the efficiency of masks of different designs. One type de-
signed for resterilization and reuse had a filtering efficiency
for airborne particles (1 to 5 |j diameter) of 99 percent. Two
-------
34
of the disposable types had an efficiency of greater than 80
percent.
Healthy hospital personnel have been shown to be car-
riers and dispersers of staphylococci. Control of this problem
has been accomplished either by antibiotic therapy, use of
masks, or removal of these personnel from their positions in
the hospital.
Within recent years, a number of air-filtration devices
have become commercially available that are capable of re-
moving extremely small particles, including microorganisms.
These devices have been produced in different sizes and ef-
ficiencies. Units as small as face masks and helmets and others
large enough to be used in air-conditioning systems are avail-
able, with efficiencies of up to 99.999 percent for removal of
submicron particles. These filters have been used to
remove microorganisms from air in hospitals, commercial fer-
mentation plants, and other controlled environmental systems.
In designing a filter system for a controlled environ-
ment, the relative position of the blower and filter in the
system is important to avoid leakage of unfiltered air. Figure
5 (Appendix) shows the positioning of the blower and filter
both when the contamination is inside the room and when the
contamination is outside the room.23 To be of value in a con-
trolled environment, a filter sytem need not be 100 percent
efficient. Table 5 derived from a mathematical model
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35
(Table 16, Appendix), presents microbial air concentrations
in a 500-cubic-foot room using filters of different efficien-
cies and with different microbial loadings.23 The tabulation
indicates that good reductions in microbial numbers can be
obtained even with less than 100-percent-effective filters,
especially since roughing filters generally are used in con-
junction with the higher efficiency filters. Some of the
commercially available filters and their characteristics—
efficiency, composition, etc.—are listed in Tables 17, 18
19, 20, and 21 in the Appendix. The ultra high-efficiency
units are capable of removing 0.1 u viral particles. °'^*
The results of one series of tests are presented in Table 21
(Appendix).
Public health authorities have made recommendations
for the control of some diseases for which the infectious
agent can survive for extended periods of time in soil and
dust. For example, in endemic areas of coccidioidomycosis or
histoplasmosis, dust control measures—oiling of roads and
planting of grass—should be practiced, or local areas should
be sprayed with disinfectants. Individuals from nonendemic
areas should not be brought into endemic coccidioidomycosis
areas for work in dusty occupations, such as cotton pick-
ing or road construction. Control of pigeons and starlings
should be attempted in areas where histoplasmosis or cryptococ-
cosis are potential hazards. Protective masks should be worn
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36
TABLE 5
ROOM CONTAMINATION IN ORGANISMS PER CUBIC FOOT
AT END OF ONE HOUR AND AT STEADY STATE23
% Filter Efficiencya
30
60
90
100
Orqanisms beinq generated per minute
1,000
3.80085
(4.00000)
1.99504
(2.00000)
1.33316
(1.33333)
1.19994
(1.20000)
10,000
38.00852
(40.00000)
19.95042
(20.00000)
13.33163
(13.33333)
11.99946
(12.00000)
100,000
380.08520
(400.00000)
199.50420
(200.00000)
133.31630
(133.33333)
119.99460
(120.00000)
Assumptions: 5,000 cubic feet in room; clean at start.
Then air changes 10 times per hour through filters. Complete
mixing obtained at all times.
•'-'First figure in the body of the table gives concentra-
tion in organisms per cubic foot reached at end of one hour.
The second figure, in parentheses, gives the equilibrium or
steady-state concentration. For development of the mathematical
solution of this problem, see Table 16, Appendix.
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37
by persons exposed to known or potential sources of infection,
such as the cleaning or destruction of old buildings—chicken
houses, barns, and silos, for example—where starlings and
pigeons have roosted. All articles contaminated by persons
or animals infected with blastomycosis, tuberculosis, and other
such infectious diseases, as well as their sputum, should be
disinfected prior to disposal.
Ledbetter has suggested that elimination of any
potential biological aerosol hazards associated with sewage
treatment units could be effected by enclosing the process
and venting the waste air through an incinerator with the
proper controls for trapping particles and gases. The cur-
rently available devices for the control of industrial emmi-
sions are discussed in detail in the National Air Pollution
Control Administration report18 "Central Techniques for Particu-
late Air Pollutants."
The control of mildew and other fungi on painted sur-
faces has not been very successful. Paint formulas with
zinc, titanium, and tin have been able to retard somewhat the
growth of fungi but have not been completely inhibitory -
The problem of food storage in recent years has been
solved successfully by the use of refrigeration. Sulfur dioxide,
benzoates, and other preservatives have also been beneficially
employed.
There are incidents in which abatement procedures have
been employed before the need was evident. That is, no information
-------
38
was available beforehand as to the extent, if any, of a problem,
but abatement was attempted because of "common sense." For
example, in one report, the requirement of counterguards for
protecting food from aerosols in cafeterias seems to have arisen
without any specific data to show the need for it. A study
was performed to determine whether the general existing guard
designs were of any value. The data did indicate that guards
were of value in shielding food from potential aerosols being
dispersed by the patrons. However, it is still not known how
extensive this problem can be and whether the presently used
designs give sufficient protection.
Research is continuing to develop fungus-resistant
varieties of crops. For example, a rust-resistant variety of
wheat was being used in 1935 when a new fungus (race 56)
evolved which ruined the spring wheat. New rust-resistant
varieties of wheat were used following this epidemic, but in
1953 and 1954 fungus race 15B evolved and attacked these vari-
eties. Although even newer varieties of wheat are presently
being used that are resistant to races 56 and 15B, wheat rust
races are known that can attack these newer varieties as well.118
Fungicides—such as copper salt mixtures, sulfur powder mix-
tures, organomercurials, organoarsenicals, and organozincs—
are used extensively on crops.90 Table 22 (Appendix) presents
experimental data on the use of an eradicant fungicide.80
Warning services are available for certain diseases—potato
-------
39
blight (Phytophthora infestans) for example—to tell farmers
when they should spray with fungicides to control the spread
of a disease. These warnings are based upon records of tem-
perature and humidity or rainfall with consideration of the age
of the crop and the susceptibility of the variety.118 In recent
years, aerial photography also has become a useful tool in the
detection and control of crop diseases.8 Sterilization or
pasteurization of the soil is used when an area has become
heavily infested with a pathogen. Heat, although expensive,
has been and still is being used, but it is being replaced by
chemicals—chloropicrin, Vapam, Mylone, formaldehyde, D-D mix-
ture, and ethyl and methyl bromides.1^
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40
5. ECONOMICS
Ridker94 has stated that because in many cases there
are either insufficient or no data concerning the number of
persons with a disease and very little information available
concerning the cost of treatment, the economic loss due to
the health effects of air pollutants is most difficult to
estimate. The task is no less difficult with biological aero-
sols. One approach to the problem is to consider the incidence
and prevalence of certain diseases. This will at least in-
dicate the magnitude of the problem and the relative importance
of the diseases.
One attempt at estimating a conservative dollar value
for some diseases is presented in Table 6.. The partial cost
of tuberculosis is presented in Table 23, Appendix.
The influenza pandemic of 1918 to 1919 resulted in
550,000 deaths in the United States alone. It has been esti-
mated that one-half of the world population suffered from the
illness and that 20 million deaths occurred. The Asian
12
flu pandemic of 1957 affected 45 million persons.
As reported by the United States Bureau of the Census,116
influenza and pneumonia ranked fifth as a cause of death in
the United States in 1966, with an average rate of 32.5 deaths
per 100,000 population. All other pulmonary diseases as a
group were 10th in rank, with 14.5 deaths per 100,000 popula-
tion (Table 24, Appendix). In 1966, the death rate for
-------
TABLE 6
RESOURCE COSTS OF DISEASES ASSOCIATED WITH AIR POLLUTION
94
Type of
Cost
Premature
Death
Premature
Burial
Treatment
Absen-
teeism
Total
Costs Associated with Selected Diseases (Millions of Dollars)*
Cancer of
the Re-
spiratory
System
518
15
35
112
680
Chronic
Bronchitis
18
0.7
89
52
159.7
Acute
Bronchitis
6
0.2
6.2
Common
Cold
200
131
331
Pneumonia
329
13
73
75
490
Emphysema
62
2
64
Asthma
59
2
138
60
259
*Using a discount rate of 5 percent.
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42
tuberculosis of all forms was 3.9, and that for meningococcal
disease was 0.4 (Table 25, Appendix).
Data pertaining to the number of cases of specified
reportable diseases in the United States are presented in
Table 26, Appendix.
It has been estimated that people in the United States
and Great Britain suffer from 2 to 10 acute respiratory ill-
nesses each year. The exact number of such illnesses reported
is dependent upon the age of the person and his environment,
and also on the number of symptoms and signs each investiga-
tor requires before he diagnoses a respiratory illness. The
incidence, the number of days of restricted activity, and the
number of days of bed rest for several respiratory diseases
are presented in Table 27 (Appendix). Table 28 (Appendix)
28
shows the age distribution rates of certain reportable diseases.
The control of plant diseases is a constant problem.
Large epidemics among crops have occurred in the past. An
epidemic of wheat rust in 1925 resulted in a loss of 12 million
bushels of wheat, and another in 1935 in a loss of 135 million
bushels.107
No information has been found on abatement and control
costs pertaining to biological aerosols. However, the economic
advantages of microorganisms in industrial fermentations are
-considerable. In antibiotic fermentation alone, the broad-
and medium-spectrum antibiotics had a drugstore and hospital
-------
43
purchase cost of approximately 200 million dollars, and
penicillin a purchase cost of 50 million dollars annually
CO
during the years 1959 to 1964.
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44
6. METHODS OF ANALYSIS
The problems of obtaining representative samples for
analysis of airborne particles covering the wide range of atmo-
spheric conditions, biological types, and particle size are
such that no single procedure is adequate for all. Therefore,
the methods of analysis tend to be specialized for relatively
narrow fields of study; consequently, many different individual
sampling devices have been -used. The best reviews of the sub-
ject are by Wolf et al.,127 Gregory,46 Noble,78 and May-66
The methods used for sampling biological aerosols are
basically the same as the methods used to sample dust and
other airborne particulates. However, since the objective is
generally to determine the viability of collected particles,
following collection the samples must undergo an additional
step: growth in a suitable nutrient under proper environmental
conditions, followed by observation of the growth and evaluation
of the results.
Since no one method of analysis will yield information
concerning all parameters of a sample, procedures should be
chosen which will yield the information that is of greatest
concern. The basic methods are these:
(1) Sedimentation:93 In this method, particulates suspended
in the air are allowed to settle either on plain surfaces or on
surfaces coated with a nutrient medium. This method can yield
information on the number of viable particles that have settled
during the sampling time, and the total number and size of all
particles that settle in a given time. Results will be influenced
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45
greatly by air movement and diameter of the aerosol particles.
(2) Impingement into liquids:19•37,43,75 Aj_r ^s drawn
through a small jet and is directed against a liquid surface,
and the suspended particles are collected in the liquid. Due
to the agitation of the particles in the collecting liquid,
aggregates are likely to be broken up. Therefore, the counts
obtained by this method tend to reflect the total number of
individual organisms in the air and are higher than the values
obtained by other methods.
(3) Impaction onto solid surfaces:4'2 Air is drawn
through a small jet(s), and the particles are deposited on
dry or coated solid sufaces or on an agar nutrient. Samples
taken by this method have been used to determine total numbers,
size, viable numbers, and variation in numbers per unit of
time during a long sampling period.
(4) Filtration:72'79'101'111 The particulates are
collected by passing the air through a filter, which can be
made of cellulose-asbestos paper, glass wool, cotton, alginate
wool, gelatin foam, or membrane material. The particulates
are washed from the filters and assayed by appropriate micro-
biological techniques. In this method, the viability of
organisms can be detrimentally affected by dehydration in the
air stream and the results thereby biased.
(5) Centrifugation:97'120 The particulates are pro-
pelled by centrifugal force onto the collecting surface, which
can be glass or an agar nutrient. Size and number information
can be obtained by this method.
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46
(6) Electrostatic precipitation: Particles are
collected by drawing air at a measured rate over an electrically
charged surface of glass, liquid, or agar. The total number
of particles or viable number is then determined.
(7) Thermal precipitation: Particles are collected by
means of thermal gradients. The design is based on the princi-
ple that airborne particles are repelled by hot surfaces and
are deposited on colder surfaces by forces proportional to the
temperature gradient. The particle size distribution can be
determined.
Because of the great number of different aerosol samples
used by investigators, general agreement was reached at the
International Aerobiology Symposium (sponsored by the Office
of Naval Research and the University of California in October
1963) that data obtained with any specialized sampler should
be correlated with at least some results obtained with a
standard reference sampler.7 The participants at the Symposium
also agreed that the United States Army Chemical Corps all-
glass impinger (AGI 30 Impinger)127 be recommended as the
standard liquid impinger, and that the Anderson Stacked Sieve
sampler4 be recommended as the standard apparatus for impaction
on solid surfaces.
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47
7. SUMMARY AND CONCLUSIONS
Biological aerosols—suspensions of microorganisms in
the air—can cause diseases of humans, animals, and plants,
and degradation of inanimate materials. The microorganisms
generally involved are the bacteria, fungi (yeast and molds),
and viruses. Bacterial and viral aerosols are detrimentally
affected by the atmospheric environment and, therefore, air-
borne transmission of such diseases is limited to short
distances and crowded conditions. Fungi are better adapted
to aerial dissemination and are known to have been transmitted
hundreds of miles from their source.
Generally, the symptoms produced by airborne infectious
organisms in humans and animals are those of a respiratory
disease. The human diseases in this category include tuber-
culosis, pneumonia, aspergillosis, influenza, the common cold,
and others. As more data are gathered, there is increasing
evidence that biological and nonbiological air pollutants are
capable of producing synergistic effects. An increase in
the incidence of respiratory diseases has been reported in
metropolitan areas during occasions of excessively high air
pollution. This potential effect has been confirmed through
the use of experimental animals in the laboratory. For example,
mice have been found to exhibit a higher mortality rate after
a controlled dosage of Klebsiella pneumoniae when preceded by
exposure to ozone or nitrogen dioxide.
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48
Compared to humans, relatively few diseases of animals
are spread toy airborne transmission. Those that are include
tuberculosis, glanders, aspergillosis, hog cholera, and New-
castle disease.
Plants are susceptible both to specific plant pathogens
and to the indigenous saprophytic decay produced by micro-
organisms present in the soil. Of the plant pathogens, fungi
are the most commonly transmitted by air and in the past have
been the agents for devastating epidemics. For example, wheat
rust destroyed an estimated 135 million bushels of wheat in
1935.
Saprophytic microorganisms are ubiquitous in nature.
Consequently, surfaces of material in contact with a humid
environment often show microbial—especially fungal—growth.
There are no environmental standards applicable to bio-
logical aerosols at the present time.
Sewage treatment plants have been investigated as a
source of hazardous biological aerosols. Although potentially
pathogenic microorganisms have been isolated downwind of
sewage tanks, the full significance of this condition is not
as yet known. Industrial fermentations with microorganisms
produce a number of economically important materials—such as
organic solvents, vitamins, and antibiotics—but no instance
has yet been reported of a disease being transmitted to the
general population as a result of any of these processes.
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49
It is not valid to present any one value for the aerial
microbial concentration of a given area. Any count is influ-
enced by the temperature, meteorological conditions, vegetation,
human and animal population, and time of day, as well as by
the inability to determine all types of microorganisms by any
one sampling procedure. However, some data have been presented
as indicative of certain areas under noted environmental condi-
tions and sampling procedures.
The problem of abatement and control of biological
aerosols is exceedingly difficult and complex. Attempts have
been made to control airborne infections indoors by ultraviolet
light irradiation. Dust control, treatment of carriers with
antibiotics, washing with disinfectant soaps, and the use of
disinfectants and surgical masks have reduced significantly the
spread of airborne disease in hospitals. Within recent years,
a number of air filtration devices have been made commercially
available that are capable of removing extremely small parti-
cles, including microorganisms. These devices have been
produced in different sizes and efficiencies and can be used
in air-conditioning systems. Their full potential in the con-
trol of biological aerosols nas not as yet been realized.
The control of outdoor airborne infections has been
limited essentially to dust control and location and elimination
of sources for specific outbreaks of certain diseases. Progress
in the area has been hindered by lack of knowledge concerning
the outdoor transmission of airborne disease.
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50
There has been no adequate way to estimate the economic
loss due to the effects of biological aerosols. However, the
economic value of microorganisms in industrial fermentations
is considerable.
The methods of analysis available for biological aerosols
tend to be specialized for relatively narrow fields of study,
and consequently many different individual sampling devices
have been used. The basic methods are these: (1) sedimentation,
(2) impingement into liquids, (3) impaction onto solid surfaces,
(4) filtration, (5) centrifugation, (6) electrostatic precipitation,
and (7) thermal precipitation.
Based on the material presented in this report, further
studies are suggested in the following areas:
(1) More studies are needed to delineate the characteris-
tics of biological aerosols with the goal of better under-
standing their production, survival, and dispersal in indoor
and outdoor areas. For example, what is the relative signifi-
cance of the transmission of a disease—such as influenza—
outdoors as compared to indoors?
(2) Further documentation of the synergistic effects of
biological and nonbiological air pollutants is warranted.
(3) Additional information is needed on the value of up-
grading air conditioning systems with filters and ultraviolet
light in schools, office areas, and other places for control of
biological aerosols.
(4) Further delineation of the potential sources of
hazardous biological aerosols is necessary.
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51
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APPENDIX
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23 2425(5 6'9 'lOn'l^ls'ieVls'lds 9 •\d'\3'\4i\51617202'\222324272829'30 4'5 '? '8 '11'121415'18'19'20
Feb.
Mar.
Apr.
May
DAY SAMPLE COLLECTED
'NOTE: Extramural, sieve sampler, heart infusion agar with 5 percent blood added, 37°C incubation for 48 hours, Feb.-May
1953, Detroit, Mich.
FIGURE 1
Daily Bacterial Counts in Urban Area
127
6 -|
. . -i—i—n—i—i
12 2 4 6 8 10 12 2 4 6 8 10 12
N PM M AM N
TIME
•NOTE: Extramural, sieve sampler, heart infusion agar with 5 percent blood added, 37°C incubation for 24 hours, June 27-
July 3, 1951, Oatland Island, Savannah, Ga.
FIGURE 2
Hourly Bacterial Counts in Nonurban Area
127
-------
o
n
o
o
0)
V
u
(O
00
70-,
50-
30-
10-
20
60
100
min.
140
180
1 - 1st patient in
2 - 2nd patient in
3 - Patient rolled over by 5 people
4 - Table moved by 5 people
5 Patient moved on table
6 Patient rolled back
7 3rd patient in
FIGURE 3
Airborne Organisms in a Surgery Room
22
-------
30-
O Nutrient Agar
® Emb Agar
• Coliforms
8
2.
©
o
"5
d
20-
10-
60
Distance Downwind (ft)
FIGURE 4
Effect of Distance Downwind of Treatment Unit
-------
65
A. Contamination Within Room
Inside Pressure Should Be Lower Than Outside
B. Contamination Outside Room
Inside Pressure Should Be Greater Than Outside
FIGURE 5
Relative Position of Filter and Blower to Confine
Contamination Inside or Outside Room
-------
APPENDIX
TABLE 7
COMMDN AIRBORNE BACTERIAL INFECTIONS OF HUMANS12'17'38/95'105'112'114
Disease
Causative Agent
Symptoms and Remarks
Pulmonary tuberculosis
Mycnbacterium tuberculosis
Lesions caused by nodules or tuber-
cles are found in the lungs (or
other parts of the body). In some
cases calcification of the nodules
takes place, and in others there
is a coalescence of the necrotic
tissue
Pulmonary anthrax
Bacillus anthracis
Primarily a disease of animals but
also occurs in man. This is the
most dangerous, although not the
most common, of the three forms of
anthrax. It is characterized by
many of the symptoms of pneumonia
and often progresses into fatal
septicemia
Staphylococcal
respiratory infection
Staphylocoecus aureus
Can result in a gradual cavitating
pneumonia or a fulminating hemor-
rhagic pneumonia
Streptococcal
respiratory infection
Streptococcus pyogenes
May develop into any of a variety
of symptoms, including tonsillitis,
sinusitis, otitis media, broncho-
pneumonia, pharyngitis, or septic
sore throat, and becomes scarlet
fever if the infecting strain pro-
duces erythrogenic toxin
(continued)
-------
APPENDIX
TABLE 7 (Continued)
COMMON AIRBORNE BACTERIAL INFECTIONS OF HUMANS
Disease
Causative Agent
Symptoms and Remarks
Meningococcal
infection
Neisseria meningitidis
Probably becomes established
initially in the nasopharynx
but clinically develops into a
cerebrospinal meningitis
Pneumococcal pneumonia
Diplococcus pneumoniae
Clinically is nearly always lobar
pneumonia. However, the infec-
tion may migrate through the nasal
passages or be distributed via the
vascular system to various parts
of the body and give rise to
localized foci of infection.
Death is due to overwhelming inter-
ference with respiration or to
general systemic toxemia
Pneumonic plague
Pasteurella pestis
Although ordinarily spread by the
bite of fleas, it can occur
secondary to glandular plague and
give rise to a primary pulmonary
form transmitted from man to man;
usually fatal
(contined)
-------
APPENDIX
TABLE 7 (Continued)
COMMON AIRBORNE BACTERIAL INFECTIONS OF HUMANS
Disease
Causative Agent
Symptoms and Remarks
Whooping cough
Bordetella pertussis
Usually a childhood disease which
begins with a catarrhal stage of
a mild cough that progresses in
severity to a paroxysmal stage
characterized by rapid consecutive
coughs and the deep inspiratory
whoop. In the convalescent stage,
the number and frequency of parox-
ysms gradually decrease
Diphtheria
Corvnebacterium
diphtheriae
A childhood disease, usually a
local infection of the mucous
surfaces. The pharynx is most
commonly affected, but infection
of the larynx, or membranous croup,
and nasal diphtheria are not
infrequently observed. Primary
infection of the lungs and other
parts of the body have been
reported
Klebsiella
pulmonary infection
Klebsiella pneumoniae
Produces necrotic lesions of the
lung parenchyma and usually is
fatal if not treated
(continued)
03
-------
APPENDIX
TABLE 7 (Continued)
COMJVDN AIRBORNE BACTERIAL INFECTIONS OP HUMANS
Disease
Causative Agent
Symptoms and Remarks
Staphylococcal wound
infection
Staphvlocoecus aureus
Those surgical wounds which be-
come infected by bacteria
settling from air in the surgery
room. These organisms may be
derived from the surgical team
or may be carried into the oper-
ting room by air currents
-------
APPENDIX
TABLE 8
COMMDN AIRBORNE FUNGAL INFECTIONS OF HUMANS12'17'38'95'105'112'114
Disease
Causative Agent
Symptoms and Remarks
Blastomycosis
Blastomyces dermatitidis
A chronic granulomatous mycosis
clinically resembling tuberculosis
with coughing, pain in the chest,
and weakness
Co cc id io idomy co s i s
Coccidioides immitis
Varies in severity in recognized
primary cases from that of a
common cold to cases resembling
influenza. Many cases are symp-
tomless. The secondary or pro-
gressive coccidioidomycosis
results in cutaneous, subcutan-
eous, visceral, and osseous lesions
with a high fatality rate
Cryptococcosis
Cryptocoecus neoformans
More commonly is a generalized
infection, but can also be a
primary (or secondary) lung in-
fection. It may spread from the
lungs as well
Histoplasmosis
Histoplasma capsulatum
A systemic mycosis of varying
severity, with the primary lesion
usually in the lungs. Clinical
symptoms of the systemic form can
resemble many other diseases
(anemia, leukopenia, Hodgkin's
disease, etc.)
(continued)
-------
APPENDIX
TABLE 8 (Continued)
COMMON AIRBORNE FUNGAL INFECTIONS OF HUMANS
Disease
Causative Agent
Symptoms and Remarks
Nocardiosis
Nocardia asteroides
A chronic disease resembling
tuberculosis, often initiated in
the lungs but sometimes pro-
gressing to a systemic infec-
tion
Aspergillosis
Aspergillosis fumigatus
A chronic pulmonary mycosis
similar to and sometimes mis-
taken for tuberculosis. The in-
fection may be secondary, parti-
cularly to tuberculosis. Pul-
monary infection results from
inhalation of airborne spores
Sporotrichosis
Sporotichum schenckii
A nodular skin infection ulti-
mately forming a necrotic ulcer.
Transmission by inhalation of
spores is rare
-a
-------
APPENDIX
TABLE 9
VIRAL AND RELATED AGENTS PRESENTLY RECOGNIZED AS THE CAUSE OF HUMAN RESPIRATORY DISEASES
51
Group_
Number Serotypes
Causing Serotype
Respiratory Illness Name
Types of Clinical
Syndromes Produced
Comments
1. Myxoviruses
Influenza A
Influenza B
Influenza C
Respiratory
Syncytial (RS)
Influenza/ febrile Causes influenza
pharyngitis or in persons of
tonsillitis, all ages
common cold, croup,
bronchitis, bron-
chiolitis,
pneumonia
Bronchiolitis Most common cause
(infants), pneumonia, of bronchiolitis
bronchitis, common in children
cold, croup
Parainfluenza
Croup (infants),
bron ch i t i s, common
cold, pneumonia,
bronchiolitis
Type 1 is the
most important
agent in the
croup syndrome
2. Adenoviruses
8
1, 2, 3, 4, 5,
7, 4, 21
Bronchitis, common
cold, pneumonia,
brochiolitis, febrile
sore throat
(continued)
vJ
-------
APPENDIX
TABLE 9 (Continued)
VIRAL AND RELATED AGENTS PRESENTLY RECOGNIZED AS THE CAUSE OF HUMAN RESPIRATORY DISEASES
Group
Number Serotypes
Causing Serotype
Respiratory Illness Name
Types of Clinical
Syndromes Produced
Comments
3. Picornaviruses
60+
Coxsackie A
(2, 3, 5, 6,
8, 10, 21)
Coxsackie B
(2, 3, 5)
Rhinoviruses
Febrile sore throat,
common cold
Febrile sore throat,
common cold,
pleurodynia
Common cold, bron-
chitis, pneumonia
Most frequently
isolated viruses
in adults with
upper respiratory
infections
ECHO (11, 20)
Febrile sore throat,
common cold, croup
3a.
4.
Reoviruses
( classification
uncertain )
Herpesviruses
3
3
1
Reovirus
(ECHO-10)
Herpes
Varicella
Minor respiratory
symptoms and diar-
rhea (children)
Pharyngitis ( adults )
Pneumonia
(continued)
-------
APPENDIX
TABLE 9 (Continued)
VIRAL AND RELATED AGENTS PRESENTLY RECOGNIZED AS THE CAUSE OF HUMAN RESPIRATORY DISEASES
Group
Number Sero types
Causing Sero type
Respiratory Illness Name
Types of Clinical
Syndromes Produced
Comments
5. Chlamydozoaceae*
Psittacosis
Psittacosis, pneumonia
6. Mycoplasmataceae
Mycoplasma
pneumoniae
Pneumonia (Eaton agent),
bronchitis, bron-
chiolitis, minor upper
respiratory illness
7. Rickettsiae
Coxiella
burnetii
(Q fever)
Pneumonia
*Not a true virus; nucleic acid core contains both RNA and DNA.
-------
APPENDIX
TABLE 10
POSSIBLE AIRBORNE VIRUS DISEASES OF ANIMALS11'69'70
Disease
Host
Symptoms and Effects
Morbidity and
Mortality
Control
Hog cholera
Swine
Fever, stilted gait,
conjunctivitis, diarrhea
As high as 90%
mortality
Immunization
Equine influenza
Horse
Fever, nasal discharge,
abortion in mares
Low mortality
Immunization
Swine influenza
Swine
Exudative bronchitis
Morbidity almost None
100%, mortality
2% or less
Feline
Canine
distemper
distemper
Newcastle disease
Cat, mink,
raccoon
Dog, fox,
mink
Chicken,
turkey, ducks,
other fowl
Vomiting, diarrhea,
nasal and eye discharge
Fever, diarrhea,
rhinitis
Coughing , sneezing ,
paralysis of legs, loss
of egg production
Recovery usual
Recovery usual
Morbidity 100%,
mortality 5-50%
Immun i z a t ion
Immunization
Immunization
Infectious bronchitis
Chicken
Rales, wheezing, loss
of egg production
Mortality up to
60% in chicks,
neglible in
older birds
Immunization
-------
76
APPENDIX
TABLE 11
COMMON LABORATORY ANIMALS USED IN STUDIES OF AIRBORNE DISEASE1'54'114
Disease
Pulmonary tuberculosis
Pulmonary anthrax
Staphylococcal respiratory
infection
Streptococcal respiratory
infection
Meningococcal infection*
Pneumococcal pneumonia
Pneumonic plague
Whooping cough
Diphtheria
Pulmonary Klebsiella infection
Staphylococcal wound
infections
Aspergillosis
Blastomycosis
Co cc id io idomy cosis
Crypto co ecus
Histoplasmosis
Nocardiosis
Laboratory Animal
Mouse
X
X
X
X
X
X
X
X
X
X
X
Guinea
Pig
X
X
X
X
X
X
X
X
X
X
X
X
X
Rabbit
X
X
X
X
X
X
X
X
X
X
X
-p
(0
tf
X
X
Monkey
X
X
X
X
X
-P
-------
77
APPENDIX
TABLE 12
AVERAGE MICROPOPULATION PER CUBIC METER FOUND SIMULTANEOUSLY
DURING 30-HOUR SAMPLING MISSION39
Time
Altitude (meters) 0600-1200 1200-1800 1800-2400 0000-0600
690 45 250 200 90
1,600 25 65 75 50
3,127 23 30 35 15
TABLE 13
QUANTITATIVE RESULTS FROM THE BALLOON-BORNE
DIRECT-FLOW SAMPLERS10
Altitude Average Volume
(thousand feet) (ft3 air/microbe)
10-30 50-100
30-60 330-500
60-90 2'000
-------
TABLE 14. AIR DISPERSION OF SMALL ORGANISMS
Disease
(Organism)
(Airborne spores)
Beet downy mildew
(Peronospora sp.)
Blossom infection
(Sclerotinia laxa)
(Bovista plumbea)
Cedar and apple
rust (Gymnosporan-
g-jum sp0 )
Chestnut blight
(Endothia para-
silica)
Crown rust of oats
(Puccinia
coronata)
Downy mildew
( Pseudoperonospora
humuli)
Leaf spots on
tulips
Loose smut of
wheat (Ustilago
tritici)
Maize rust
(Puccinia sorahi)
Onion mildew
(Peronospora
destructor)
Means of
Dispersion
Wind
Wind
Air currents
Air currents
Air currents
Air currents
Wind
Air currents
Raindrop splash
and wind
Air currents
Wind
Air currents
Distances and Units Dispersed
(Horizontal Dispersion)
Degrees north of equator
Fungus colonies on plate
Meters from seed plants
Plants injured, %
Feet from center of
nearest source row
Blossom infection, %
Meters from release
point
Spores caught
Yards from infected
trees
Leaf infections
Feet from spore source
Ascospores found
Feet from inoculum
source
Infections, %
Feet from spore source
Leaves infected, %
Centimeters from
conidia source
Lesions/plant
Meters from spore
source
Smutted heads
Kilometers from spore
source
Plants attacked, %
Feet from onion sets
Lesions/100-ft row
57°30'
3.61
10
28
22
55.7
5
912
0
64
27
23
3
92.9
10
26
I5o2
31.6
2
241
0.5
100
120
1,138
64°20'
0.49
150
8
44
39.1
10
323
55
40
85
11
5
53.4
50
16
34.6
20.1
4
234
205
3
780
98
68°55'
0.48
1,000
1
66
29.3
15
165
110
33
180
8
7.7
35
100
12
5800
1209
24
114
4.5
0.3
1,750
1
71°5'
0.72
68
22.4
20
102
220
26
266
8
10.3
19.5
200
7
79.8
8.5
80
0
6.5
0
2,000
0
440
19
13
0.7
400
3
102.0
Sol
CO
(continued)
-------
TABLE 14. AIR DISPERSION OF SMALL ORGANISMS (Continued)
Disease
(Organism)
Potato late blight
( Phvtophthora
infestans)
Powdery mildew on
barley
( Erys iphe
qraminis)
Stem rust
(Puce in ia
_qraminj-JL)
Stem rust on rye
(P. qraminis
secalis)
(Tilletia tritici)
Tobacco blue mold
(Peronospora
tabacina)
Wheat stem rust
(Puce in ia
qraminis)
White pine blister
rust (.Gronartium
ribicola)
Means of
Dispersion
Wind
Wind
Wind
Wind
Air currents
Wind
Air currents
Air currents
Distances and Units Dispe]
(Horizontal Dispersion
Centimeters from edge
of infective group
Plants infected, %
Meters from source
Plants affected, %
Feet from barberry
hedge
Grass infected, %
Meters from source plant
g/100 ears
Meters from release
point
Spores cauqht
Yards from source
Plant lesions/1,000
in3 of field
Miles from known source
Spores collected
Feet from gooseberry
bush
Diseased trees , %
30
89
1.5
99
15
100
50
47.6
5
800
0
140
200
13,092
50
75
90
63
3.5
84
125
41
300
92.3
10
168
4
8
360
10,768
150
55
rsed
150
43
5.5
76
225
5
1,000
122.3
15
49
8
1
580
8,883
350
40
(Vertical Dispersion)
Azalea flower spot
(Ovulinia azaleae)
Onion mildew
(Peronospora
destructor)
Air currents
Air currents
Inches above ground
Infections
Altitude, feet
Spores/ft3 air
4
42
100
32
10
28
200
102
18
17
700
451
210
22
7.5
70
325
1
3,000
149.7
20
30
12
0.5
740
7,920
450
36
270
5
8.5
68
425
0.5
940
6,975
650
29
48
0
1,200
801
(continued)'
-------
APPENDIX
TABLE 14- AIR DISPERSION OF SMALL ORGANISMS (Continued)
Disease
(Orqanism)
Wheat stem rust
(Puce in ia
graminis)
Means of
Dispersion
Air currents
Distances and Units Dispersed
(Vertical Dispersion)
Feet above barberry
bushes
Aeciospores caught
Altitude, feet
Urediospores
Elevation, meters
Spore s/cm2 /min
1,000
19
1,000
48,200
30
1,458
2,000
14
5,000
7,730
400
490
7,000
5
10,000
144
600
339
12,000
1
14,000
40
800
231
00
o
-------
81
APPENDIX
TABLE 15
RECOMMENDED CONDITIONS FOR USE OF COMMON GERMICIDAL
SUBSTANCES AT ROOM TEMPERATURE (25° C)54
Sermicide
Phenol
Lysol
Quaternary ammonium com-
pounds (Roccal, Purasan,
Hyamine, etc. )
Hypochlorites + 1% wet-
ting agent (Naccanol,
etc. )
Caustic sodium hydroxide
Formalin (37%HCHO)
Steam formaldehyde vapor
(closed areas)
beta-Propiolactone vapor
Ethylene oxide gas
Concentration and Exposure Time for
Typical Classes of Microorganisms
Vegetative
Bacteria
5% (5 min)
2% (5 min)
0.1-1.0%
( 5 min )
200-1,000
ppm (1 min)
2% (15 min)
5% so In
( 10 min )
Bacterial
Spores
NRa
NRa
NRa
500-5,000
ppm (5
min)
5% (30
min)
10% so In
(10 min)
Funqi
5% (15 min)
3% (15 min)
NRa
2,000 ppm
(10 min)
10% (30
min)
5% so In
(10 min)
1 ml/ft3 in air with RHb
above 80% ( 30 min )
200 mg/ft3 in air with RHb
above 80% ( 30 min )
300 mg/liter (8-16 hr )
Bacterial
Toxins
NRa
NRa
NRa
NRa
5% soln
(pH 11.5)
(15 min)
5% soln
(10 min)
NRa
NRa
NRa
aNR = not recommended.
= relative humidity,
-------
82
APPENDIX
TABLE 16
MATHEMATICAL MODEL ON HOSPITAL VENTILATION23
Let
N = number of organisms/ft present at time t in minutes
V = volume of room in cubic feet
K = number of .complete changes of room volume/hour
b = total number of organisms/minute entering because of human
presence
a = efficiency of the filter
Then,
NKV (1-a) A t = total number of organisms/ft entering the
V60 interval A t because of the inefficiency of
the filter.
]._ b A t = total number of organisms/ft3 entering during interval
V At because of contamination from individuals.
— -g^— A t = total number of organisms/ft3 leaving during A t.
A N = (total number of organisms/ft3 entering) - (total number
of organisms/ft3 leaving)
(1-a)
60
A N _ b _ KNa
At V 60
dN _ b _ KaN _
dt V 60
= k (1 - aKVN )
V ( 60b~J
1-aKVN V "u
6 Ob
-aKVdn
60b [* 6Ob = [• b dt
1-aKVN J ~V
6 Ob
(Continued)
-------
83
APPENDIX
TABLE 16 (Continued)
MATHEMATICAL MODEL ON HOSPITAL VENTILATION
6 Ob In Cl - aKVN_) = b t + C If t = 0
aKV (. 60b ) v N = 0
then, C = 0
_ 6Ob i 1 - aKVN) _ b_
aKV \ 60b f~ v fc
_ 60 -r^ (l ~ aKVN)_ ^
aK ^" J 60b^ u
In fl - aKVN) _ aKT
(_ 60b ^ 60
Cl - aKVN) = exp _ aKt
1 60b \ 60
6 Ob
aKV
1 - exp
-------
APPENDIX
TABLE 17
ROUGHING FILTERS
23
(Particle Retention3 10 to 60 Percent-13)
Nomenclature
AAF type HV 2
AAF PL 24 with
type G media
Drico puff-
glass
Farr-Air HP- 2
Farr 44-68
Manufacturer
American Air
Filter Corp. ,
Louisville,
Ky.
American Air
Filter Corp.
Drico Indus-
trial Corp.
Passaic, N.J.
Farr Filter
Co . , Los
Angeles ,
Calif.
Farr Filter
Co.
Media
Adhesive-coated
V- crimped wire
screen mesh
Glass filament
Spun glass
fiber
Pleated cotton
fabric
Crimped screen
and wire mesh
Capacity
cfm/ft2
of Face A
250
to
430
up
to
250
32
to
1,000
250
to
435
250
to
435
Face
Velocity
( f t/min )
300
to
500
250
300
250
to
435
250
to
435
Pressure
Drop
(HoO)
0.004"
0.06 '
0.08"
to
0.11"
0.045"
to
0.115"
0.040"
Maximum
operation
temperature
110°F
250°F
175°F
255°F
275°F
to five
"
"Inclusion of any particular filter in this table does not constitute endorsement by
the United States Government or by the authors.
-------
APPENDIX
TABLE 18
MEDIUM-EFFICIENCY FILTERS23
(Particle Retention3 60 to 90 Percent13)
Nomenclature
AAF deep bed
Type 100 FG
AAF PL 24
frame
Type 25 FG
Aero solve 45
Expandure
Manufacturer
American Air
Filter Corp. ,
Louisville,
Ky.
American Air
Filter Corp.
Cambridge
Filter Corp. ,
Syracuse, N.Y.
Flanders
Filters,
Riverhead ,
N.Y.
Media
Fiberglass
Fiberglass
Glass fibers
Fiberglass
Capacity
cfm/ft"5
of Face A
50
to
250
50
to
250
up
to
500
250
Face
Velocity
( f t/min )
250
200
250
to
500
250
Pressure
Drop
(H20)
0.24"
0.09"
0.16"
to
0.25'
0.38"
Maximum
operation
temperature
700°F
400°F
400°F
200°F
(continued)
oo
en
-------
APPENDIX
TABLE 18 (Continued)
23
MEDIUM-EFFICIENCY FILTERS
(Particle Retention3 60 to 90 Percent")
Nomenclature
Type CA
U-Lok
Manufacturer
Microtron
Corp . ,
Charlotte,
N.C.
Union Carbide
Development
Co., N.Y.,
N.Y.
Media
Polyester/
acetate
adhesive-
coated
Dynel fibers
Capacity
cfm/ft2
of Face A
200
to
250
200
to
500
Face
Velocity
( f t/min )
200
to
250
300
Pressure
Drop
(H20)
0.08"
to
0.13"
0.10"
Maximum
operation
temperature
350°F
180°F
aOne to five |_i.
^Inclusion of any particular filter in this table does not constitute endorsement by
the United States Government or by the authors.
oo
-------
APPENDIX
TABLE 19
,23
HIGH-EFFICIENCY FILTERS'
(Particle Retention3 90 to 99 Percent13)
Nomenclature
Multi-Pakc
with 50 FG
Deep bed with
50 FG
Micretain
Aerosolve 85
Aero solve 95
Manufacturer
American Air
Filter Corp. ,
Louisville,
Ky.
American Air
Filter Corp.
Cambridge
Filter Corp.
Syracuse,
N.Y.
Cambridge
Filter Corp.
Cambridge
Filter Corp.
Media
Glass fiber
Glass fiber
Glass-asbestos
pleated
Glass fibers
pleated
Glass fiber
pleated
Capacity
cfm/ft~2
of Face A
125
to
250
40
to
200
50
to
250
125
to
500
125
to
500
Face
Velocity
( f t/min )
250
200
Up
to
250
250
to
500
250
to
500
Pressure
Drop
(H?0)
0.42"
0.42"
0.4"
0.22"
to
0.32"
0.35"
to
0.45 '
Maximum
Operation
Temperature
400°F
400°F
22o°F
to
800°F
400°F
400°F
oo
(continued)
-------
APPENDIX
TABLE 19 (Continued)
HIGH-EFFICIENCY FILTERS
(Particle Retention3 90 to 99 Percent*3)
Nomenclature
HP-100
HP-200
Manufacturer
Farr Filter
Co.,
Los Angeles,
Calif.
Farr Filter
Co.
Media
Glass fiber
pleated
Glass fiber
Capacity
cfm/ft^
of Face A
250
250
Face
Velocity
( f t/min )
250
250
Pressure
Drop
(H20)
0.20"
0.38"
Maximum
Operation
Temperature
275°F
275°F
aOne to five |j-
^Inclusion of any particular filter in this table does not constitute endorsement by
the United States Government or by the authors.
GThese filters made to accommodate double thiokness of media.
03
CD
-------
APPENDIX
TABLE 20
.23
ULTRA-HIGH EFFICIENCY FILTERS
(Particle Retention3 More than 99.99 Percent13)
Nomenclature
\AF Type F
(glass)
AAF Type F
( ceramic)
Cambridge
Absolute
Magnamedia
Airpure
absolute
glass F 600
Manufacturer
American Air
Filter Corp. ,
Louisville,
Ky.
American Air
Filter Corp.
Cambridge
Filter Corp. ,
Syracuse,
N.Y.
Farr Filter
Co. ,
Los Angeles,
Calif.
Flanders
Filters,
Riverhead ,
N.Y.
Media
Glass fiber
and kraft
paper or alum
sep.
Ceramic asbes-
tos f ib er and
alum sep.
Glass fiber
asbestos paper
sep.
Glass fiber
Glass fiber
(F 600)
Capacity0
cfm/ft2
of Face A
30
to
400
30
to
250
30
to
345
30
to
400
30
to
400
Face
Velocityd
ft/min
68
to
325
250
Up
to
275
Up
to
250
Up
to
320
Pressure
Drop
(H20)
1.0"
1.0"
1.0"
1.0"
1.0"
Maximum
Operation
Temperature
250°F
to
1,000°F
1,600°F
to
2,300°F
800°F
Up
to
1,000°F
850°F
-------
APPENDIX
TABLE 20 (Continued)
ULTRA-HIGH EFFICIENCY FILTERS
(Particle Retention3 More than 99.99 Percent-'3)
Nomenclature
Airpure
absolute
ceramic-
asbestos
Ultra-Aire
Manufacturer
Flanders
Filters
Mine Safety
Appliance Co .
Pittsburgh,
Pa.
Media
Ceramic-
asbestos
Glass fiber
Capacity0
cfm/ft2
of face A
50
to
250
35
to
250
Face
Velocity0*
f t/min
Up
to
250
Up
to
250
Pressure
Drop
(H20)
1.0"
0.9"
Maximum
Operation
Temperature
1,60QOF
500°F
aOne to five u.
^Inclusion of any particular filter in this table does not constitute endorsement by
the United States Government or by the authors.
cCapacities are in cfm/ft^ of face area, not total area of filter.
velocities are fpm for 1 ft of face area, not media velocity.
o
-------
APPENDIX
TABLE 21
PENETRATION OF Tl PHAGE3 AND BACTERIAL AEROSOLS13 THROUGH COMMERCIAL AIR FILTERS48
Filter type
Ultrahigh-
ef f iciency
Ultrahigh-
eff iciency
Ultrahigh-
eff iciency
Description
Glass micro-fibers
waterproofed ,
plastic base
adhesive, 35 cfm
rated capacity
8" x 8 ' x 3-1/16"
Glass asbestos
fibers with organic
binder, neoprene
type sealer, 30 cfm
rated capacity
8" x 8" x 3-1/16"
All-glass fibers
with no organic
binder, rubber base
type sealer, 30 cfm
rated capacity
8" x 8" x 3-1/16"
Test
Number
1
2
3
Mean
1
2
3
Mean
1
2
3
Mean
Relative
Humidity
%
15
to
20
15
to
20
20
to
25
Test
Air
Flow
25
cfm
25
cfm
25
cfm
Filter
Resistance
( water )
1.04"
0.69'1
0.53"
Penetration
Tl
Phagec
%
3.2xlO~3
4.3xlO~3
4.3xlO~3
3.9xlO~3
1.2xlO~3
6.0x10 4
7.6x10 4
8.5xlO~4
4.6xlO~3
3.9xlO~3
4.7xlO~3
4.4xlO~a
Bacterial
Spores
%
8.7xlO~5
9.6xlO~5
1.4xlO~4
l.lxlO~4
8.4xlO~5
6.1x10 5
7.2x10 5
•— R
7.2x10
4.0xlO~4
1.7x10 4
2.8x10 4
— -1
2.8x10
DOPe
%
0.011
0.02
0.006
(continued)
-------
APPENDIX
TABLE 21 (Continued)
PENETRATION OF Tl PHAGEa AND BACTERIAL AEROSOLS13 THROUGH COMMERCIAL AIR FILTERS
Filter Type
Ultrahigh-
eff iciency
Description
All-glass fibers
with no organic
binder, rubber base
type sealer, 22 cfm
rated capacity
8" x 8" x 12"
Test
Slumber
1
2
3
Mean
Relative
Humidity
%
15
to
20
Test
Air
Flow
22
cfm
Filter
Resistance
( water )
0.75"
Over-all mean for ultrahigh-ef f iciency filter units
High
efficiency
0.5" thick fiberglass
pads containing 1.25
U diameter glass
fibers
1
2
3
Mean
40
to
45
20ft
per
min*
0.50
0.50
0.51
Penetration
Tl
Phagec
%
l.lxlO"3
1.0x10 3
9.9x10 4
1.0xlO~3
3 xlO~3
1.8
2.0
1.9
1.9
Bacterial
Spores"
%
1.9xlO~3
2.2xlO~3
2.8xlO~3
2.3xlO~3
DOPe
0.002
7 x!0~4
0.23
0.26
0.50
0.33
aTl phage aerosol number median diameter (NMD): 0.1 u.
bB_. subtilis var. niger spore aerosol NMD: 1 u.
GPrefilter total sampler (impinger + backup filter) recovery: 10s phage/liter.
Prefilter cotton collector recovery: 105 spores/liter.
eDOP penetration as stamped on filter unit by manufacturer.
Face velocity (1.5 cfm through 3-3/4 inch diameter filter pads).
to
-------
APPENDIX
TABLE 22
EFFECT OF ERADICANT FUNGICIDES ON SPORODOCHIA PRODUCTION,
CONIDIAL GERMINATION, AND BLOSSOM BLIGHT
CAUSED BY MONILIA LAXA ON DRAKE ALMOND, 195880
Fungicide
Dates of
application
Average
number of
sporodochia
per twig
Twigs
with
sporodochia
Conidial
germination
on agar
Amount blossom
blight per 100
20-inch shoots
inspected
SPCP
SPCP plus
LLS
SPCP
Untreated
12/13/57
12/13/57
1/9/58
4.6
1.7
8.8
14.7
Orchard No. 1
SPCPa
SPCP plus
LLSa
SPCP
Untreated
12/12/57
12/12/57
1/22/58
0.58
0.94
0.28
2.04
18
16
20
74
94D
26
34
78
21.2
15.7
42.4
93.1
Orchard No. 2
100
48
76
96
46C
1
3
60
60.9
37.8
78.1
232.0
aSPCP is 8.0 pounds of 37% sodium pentachlorophenoxide in 100 gallons of water
applied at the rate of 400 gal/acre with an airblast sprayer, and LLS is 11.2 gal of
32 Baume calcium polysulfide combined with SPCP.
^Potato dextrose agar.
cWater agar.
co
-------
APPENDIX
TABLE 23
TUBERCULOSIS HOSPITAL USE116
(Rates per 1,000 Population)
94
Year
1935
1945
1955
1965
1966
Admission
Rate
0.7
0.7
0.7
0.3
0.2
Total D.ays
in Hospital
174.2
164.7
145.9
52.4
39.9
Average Length
of Stay (days)
257.4
253.1
218.9
182.5
168.3
Total Expense
per Patient Day
$7.20
$16.70
$18.27
-------
95
APPENDIX
TABLE 24
DEATH RATE FOR THE 10 LEADING CAUSES OF DEATH, 1966116
(Rate per 100,000 Population)
Disease
Death Rate
Diseases of the heart
Malignant neoplasms
Vascular diseases affecting central
nervous system
Accidents
Influenza and pneumonia
Certain diseases of early infancy
General arteriosclerosis
Diabetes mellitus
Other diseases of the circulatory system
Other bronchiopneumonic diseases
371.2
155.1
104.6
58.0
32.5
26.4
19.9
17.7
14.6
14.5
TABLE 25
DEATH RATE (1950 to 1966) AND DEATHS (1965 AND 1966) FROM SELECTED CAUSES116
^11 causes*
Tuberculosis
(all forms)
Meningococcal
infection
Asthma
Influenza and
pneumonia
( except pneu
monia of
newborn)
Influenza
Pneumonia
Bronchitis
Deaths per 100,000 Population Total Deaths
1950
963.8
22.5
0.6
2.9
_31.3
4.4
26.9
2.0
1955
930.4
9.1
0.6
3.6
27.1
1.7
25.4
1.9
1960
954.7
6.1
0.4
3.0
37.3
4.4
32.9
2.4
1964
939.6
4.3
0.4
2.3
31.1
0.9
30.2
2.8
1965
943.2
4.1
0.5
2.3
31.9
1.2
30.8
,3.0
1966
951.3
3.9
0.4
2.2
32.5
1.4
31.0
3.1
1965
1,828,136
7,934
850
4,520
61,903
2,295
59,608
5,772
1966
1,863,149
7,625
876
4,324
63,615
2,830
60,785
6,151
*A11 causes listed in the complete table.
-------
APPENDIX
TABLE 26
SPECIFIED REPORTABLE DISEASES: CASES REPORTED,* 1945-1966116
Disease
Diphtheria
Measles
Meningococcal
infection
Pertussis
(whooping cough)
Psittacosis
Streptococcal sore
throat and scarlet
fever
Tuberculosis (newly
reported active cases
1945
18,675
146,013
8,208
133,792
27
185,570
1950
5,796
319,124
3,788
120,718
26
66,494
1955
1,984
555,156
3,455
62,786
334
147,502
76,245
1960
918
441,703
2,259
14,809
113
315,173
55,494
1963
314
385,156
2,470
17,135
76
342,161
54,062
1964
293
458,083
2,826
13,005
53
404,334
50,874
1965
164
261,904
3,040
6,799
60
395,168
49,016
1966
209
204,136
3,381
7,717
50
427,752
47,767
*Figures should be interpreted with caution. Reporting of some of these diseases
is known to be incomplete and only indicates trends of disease incidence.
-------
97
APPENDIX
TABLE 27
RESPIRATORY DISEASES IN THE UNITED STATES, JULY 1966-JUNE 1967117
Incidence
and Effects
Incidence (x 1000)
Days of restricted
activity (x 1000)
Days of bed
disability (x 1000)
Common
Cold
109,713
263,622
109,999
Influenza
55,382
186,514
102,016
Pneumonia
2,013
26,409
16,406
Bronchitis
3,411
19.966
10,392
-------
APPENDIX
TABLE 28
AGE-SPECIFIC DISEASE RATES PER 100,000 POPULATION PER YEAR, 1959-61
28
-ause
?uberculosis ,
respiratory
. leningococcal
infections
Asthma
Influenza and
pneumonia ( except
of newborn)
Acute bronchitis
Chronic and Unqual-
fied bronchitis
Age distribution
for a standard
million population
Rate per Age Group
0.4
0.22
1.90
0.39
52.95
2.84
1.60
113,320
4-14
0.03
0.20
0.22
2.27
0.14
0.08
197,773
15-24
0.41
0.16
0.39
2.46
0.09
0.08
133,948
25-34
2.18
0.06
0.81
4.12
0.08
0.08
127,247
35-44
5.05
0.06
1.63
8.70
0.16
0.29
134,290
45-54
9.70
0.16
3.44
18.12
0.35
1.06
114,238
55-64
16.00
0.14
7.05
38.81
0.65
3.56
86,839
65-74
23.03
0.15
12.29
101.93
1.10
8.57
61,324
75-84
31.88
0.23
16.91
315.73
2.25
12.79
25,839
85+
36.70
0.19
. 16.08
998.74
7.40
12.68
5,182
All
5.89
0.34
2.69
32.07
0.64
1.63
00
------- |