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EXCERPTS
Susan S. Schiffman, PhD, Duke University, NC
PAGE 8
Special emphasis was placed on potential health issues related to
odorous emissions from animal manures AND OTHER BIOSOLIDS.
Odors are sensations that occur when a complex mixture of compounds
(called odorants) stimulate receptors in the nasal cavity. Most
odorants associated with animals manures AND BIOSOLIDS are volatile
organic compounds (VOC's) that are generated by bacterial degradation of
protein, fat, and carbohydrates in the organic matter. Reactive
inorganic gases such as AMMONIA and hydrogen sulfide are also important
odorants that can be emitted from animal manures AND BIOSOLIDS.
PAGE 9
Workshop participants discussed three paradigms by which ambient
odors may produce health symptoms in communities with odorous manures
AND BIOSOLIDS.
In the first paradigm, the symptoms are induced by exposure to
odorants at levels that also cause irritation (or other toxicological
effects). That is, irritation -- rather than the odor -- is the cause
of the symptoms, and odor simply serves as an exposure marker.
In this paradigm irritancy (or other toxicity) generally occurs at
a concentration somewhat higher (about 3 to 10 times higher) than the
concentration at which odor is first detected (odor threshold).
While the concentration of each individual compound identified in
odorous air from agricultural and municipal wastewater facilities seldom
exceeds the concentration that is known to cause irritation, the
combined load of the mixture of odorants can exceed the irritation
threshold. That is, the irritation induced by the mixture derives from
the addition (and sometimes synergism) of individual component VOCs.
In the second paradigm health symptoms occur at odorant
concentrations that are not irritating. This typically occurs with
exposure to certain odorant classes such as sulfur-containing compounds
and organic amines at concentrations that are above odor detection
thresholds but far below irritant thresholds.
PAGE 10
v
Health symptoms often reported include a stinging sensation,
nausea, vomiting, and headaches. The mechanism by which health
symptoms are induced by sulfur gases or organic amines for which odorant
potency far exceeds the irritant potency is not well understood.
Noxious odors that are neither irritating nor toxic can set up a
cascade of events such as physiological stress or nutritional problems
(caused by altered food intake) that lead to health effects. The
genetic basis of aversions to malodors is not well understood, but brain
imaging studies suggest that noxious odors stimulate different brain
areas than those that process pleasant odors.
In the third paradigm, the odorant is part of a mixture that
contains a co-pollutant that is essentially responsible for the reported
health symptom. Odorous airborne emissions from confined animal
housing, composting facilities, AND LAND APPLICATION OF SLUDGE can
contain other components that may be the cause of the symptoms such as
bioaerosols consisting of endotoxin, dust from food, airborne manure
particulates, glucans, allergens, microorganisms, or toxins.
Thus, an individual may encounter odors from swine facilities while
simultaneously exposed to dust or gram-negative endotoxin. In this
case, the symptoms or health effects are more likely to result from the
irritant effects of the dust or from other inflammatory responses to
endotoxin exposure rather than from odor.
PAGE 11
A majority of the studies reviewed in this report are taken from
laboratory experiments where greater control is possible and mostly not
from confined animal feeding operations, municipal wastewater or
BIOSOLIDS treatment, OR THE RECYCLING of these byproducts.
PAGE 12
By the review of these studies, examples are given that can help
elucidate the types of health symptoms that may occur from exposure to
odorous volatile compounds and associated particulates from animal
feeding and the processing and recycling of animal manures AND
BIOSOLIDS.
In addition, this review helps establish a basis for future
management and research regarding the potential impacts of odor on human
health from such operations.
The odor exposures that have received the greatest research
attention are those that involve irritation. Physiological responses
to irritation in the upper respiratory trace (nose, larynx) and/or lower
respiratory tract (trachea, bronchi, deep lung sites) have been
documented in both humans and animals.
Irritation of the respiratory tract can alter respiratory rate,
reduce respiratory volume (the amount of air inhaled), increase duration
of expiration, alter spontaneous body movements, contract the larynx and
bronchi, increase epinephrine secretion, increase nasal secretions,
increase nasal airflow resistance, slow the heart rate, constrict
peripheral blood vessels, increase blood pressure, decrease blood flow
to the lungs, and cause sneezing, tearing, and hoarseness.
Release of the potent hormone epinephrine (also called adrenalin)
subsequent to nasal irritation may be a source of feelings of anger and
tension that have been reported by persons exposed to odors.
Epidemiological studies in communities with animal operations and
municipal wastewater facilities have reported increased occurrence of
self-reported health symptoms consistent with exposure to irritants.
The odorous emissions that reach neighbors of animal and municipal
wastewater facilities AND RECYCLING OPERATIONS are a function of the
concentration of volatiles produced at the source as well as their
emission rates, dispersion, deposition, and degradation in the downwind
plume.
Furthermore, numerous sources at a facility can contribute to the
total odor and irritation intensity experienced by neighbors.
Workshop participants concluded that current evidence suggests that
the symptom complaints experienced by neighbors of some odorous animal
operations and municipal wastewater facilities may constitute health
effects.
PAGE 13
This report summarizes (the) current state of knowledge regarding
the health effects of ambient odors with special emphasis on odorous
emissions from animal manures AND OTHER BIOSOLIDS. The potential
mechanisms that are responsible for health symptoms are discussed.
PAGE 14
The most common health complaints associated with environmental
odors from agricultural sources AND BIOSOLIDS include eye, nose, and
throat irritation, headache, nausea, hoarseness, cough, nasal
congestion, palpitations, shortness of breath, "stress", drowsiness, and
alterations in mood.
These symptoms attributed to odors are generally acute in onset
(occur at the time of exposure) and self-limited in duration (remit
after a short period of time).
Persons with allergies and asthma often assert that odors
exacerbate their symptoms. Persons who report adverse health symptoms
from odors usually indicate that they have problems with numerous types
of odorous compounds.
PAGE 15
PHYSIOLOGY OF ODOR PERCEPTION
Health symptoms from odors can potentially result from two
sources: the odor (the sensation) or the odorant (the chemical or
mixture of chemicals that happens to have an odor).
Odor sensations are induced when odorants interact with receptors
in the elfactory epithelium in the top of the nasal cavity. Signals
from activated receptors are transmitted via the olfactory nerve (first
cranial nerce) to the olfactory bulb and ultimately to the brain.
Some reactive inorganic gases such as AMMONIA and H2S can also be
odorants.
Odorants can also stimulate free nerve endings of four other
cranial nerves (trigeminal, vagus, chorda tympani, and glossopharyngeal
nerves) to induce sensations of irritation.
Sensory neurons of the trigeminal nerve innervate the eyes, nose,
anterior 2/3 of the tongue, gums, and cheeks. The trigeminal nerve
responds to five different classes of stimuli: (1) chemical, (2)
mechanical (such as dust particles that touch the mucous linings of the
nose, eye, or mouth), (3) thermal (temperature), (4) nociceptive (pain),
and (5) proprioceptive (movement/position).
Trigeminal stimulation by odorous chemicals and dust induces
sensations such as irritation, tickling, burning, stinging, scratching,
prickling, and itching.
Free nerve endings of the vagus nerve transmit information on
irritation in the throat, trachea, and lungs. Free nerve endings of
the chorda tympani nerve (along with the trigeminal nerve) medicate
irritation on the anterior tongue during mouth breathing; free nerve
endings of the glossopharyngeal nerve transmit information about
irritation on the posterior tongue.
PAGE 16
Overall, the same compound can generate sensations of both odor and
irritation, but the concentration necessary to elicit irritation is
generally higher than that needed for odor.
Almost any airborne chemical can, in sufficient concentration,
stimulate chemosensory trigeminal receptors in the nose and eyes, damage
tissue, or cause toxic effects.
PARADIGMS BY WHICH ODORS CAN AFFECT HEALTH SYMPTOMS
There are at least three paradigms that may explain how odors or
odorants could potentially affect human health. In Paradigm l, the
symptoms are induced by exposure to an odorant at levels that also cause
irritation (or other toxicological effects).
In this case, irritation -- rather than the odor -- is the cause of
the symptoms, and odor simply serves as an exposure marker. For
odorants acting under Paradigm l, the irritancy (or other toxicity)
generally occurs at a concentration above -- but within an order of
magnitude -- of the odor threshold.
That is, the detection threshold for irritancy (concentration at
which irritancy is first detected) is between 3 - 10 times higher than
the concentration at which odor is first detected. (The odor
detection threshold is the concentration at which odor is first
detected.) Examples include AMMONIA, chlorine, and formaldehyde ......
At concentrations above the irritant threshold, both odor and
irritant sensations can coexist. The sensation of odor is merely
coincident with the more relevant irritative process; symptoms are more
likely caused by irritation rather than "odor-induced." In this
paradigm, odor is a warning of potential health symptoms at elevated
concentrations.
In Paradigm 2, by contrast, exposure to odorous compounds at
concentrations above the odor threshold but below irritant levels is
associated with health symptoms.
This typically occurs with exposure to certain odorant classes such
as sulfur-containing compounds and organic amines with odor thresholds
that are 3 - 4 orders of magnitude (that is 10/3 and 10/4 times) below
the levels that cause classical toxicological or irritant symptoms.
Industrial and biological sulfur gases (e.g. hydrogen sulfide,
mercaptans, or thiophenes) have odor thresholds in the ppb (parts per
billion) or ppt (parts per trillion range but they do not produce
objective mucous membrane irritation until they reach a level of 10 - 20
ppm (parts per million.)
v
Nevertheless, health symptoms are often reported from residents of
communities exposed to industrial sulfur gases and other malodorous
compounds at levels exceeding the odor threshold but below irritant
thresholds.
PAGE 17
v
The third paradigm in which odors may be associated with symptoms
is one in which the odorant is part of a mixture that contains a
co-pollutant that is actually responsible for the reported health
symptom. Odorous airborne emissions from confined animal operations,
composting facilities, AND SLUDGE can contain other components that may
be the cause of the symptoms such as bioaerosols consisting of
endotoxin, dust from food, airborne manure particulates, glucans,
allergens, microorganisms, or toxics.
It should be noted that odor perception is not always an adequate
warning of impending toxicity. This situation arises when a compound
is toxic or irritating at concentrations below the odor threshold.
A few compounds produce irritation almost in the absence of odor;
for example, CO2 is an irritant that produces minimal, if any, odor
response in humans.
EVIDENCE THAT ODORS CAN PRODUCE HEALTH SYMPTOMS
There is experimental evidence to support each of the paradigms
given above. This evidence is described below in order to elucidate
the mechanisms by which odorous emissions can cause health symptoms.
PAGE 18
EVIDENCE FOR PARADIGM 1 : IRRITATION RATHER THAN THE ODOR CAUSES
THE HEALTH SYMPTOMS
There is extensive evidence that odorous volatile compounds can
produce irritation in both the upper respiratory tract (nose, larynx)
and lower respiratory tract (trachea, bronchi, deep lung sites).
This irritation involves both sensory signals (mediated by the
trigeminal and vagus nerves) as well as actual inflammation of tissues.
Sensory irritation can arise: (1) from a single odorous compound
above its irritant threshold, (2) from the aggregate effect of low
concentrations of odorous chemicals not normally considered to be
irritants, or (3) from weak trigeminal stimulation in combination with
much higher levels of olfactory stimulation.
The fact that mixtures of low concentrations of odorants can induce
sensory irritation is due to the fact that the primary mixture
constituents can be additive (or, in some cases, even synergistic) in
their ability to produce irritation, i.e. the irritancy of the mixture
may, in some cases, be greater than the sum of the individual
components. Even subthreshold levels of individual volatile organic
compounds (VOCs) can add together when delivered in a mixture to produce
noticeable sensory irritation.
PAGE 19
....However, the mixture of volatile compounds emitted from manures
AND BIOSOLIDS do have the potential to cause sensory irritation with or
without health complaints.
PHYSIOLOGICAL SYMPTOMS CAUSED BY SENSORY IRRITATION
Administration of irritant compounds to the upper and/or lower
airway in laboratory studies produces many systemic responses
including: (1) changes in respiratory rate, depending upon the primary
level of irritation (upper versus lower), (2) reduced respiratory
volume, (3) increased duration of expiration, (4) alterations in
spontaneous body movements, (5) contraction of the larynx and bronchi,
(6) increased epinephrine secretion, (7) increased nasal secretion, (8)
increased nasal airflow resistance, (9) increased bronchial tone, (10)
decreased pulmonary ventilation, (11) bradycardia, (12) peripheral
vasoconstriction, (13) increased blood pressure, (14) closure of the
glottis, (15) sneezing, (16) closure of the nares, (17) decreased
pulmonary blood flow, (18) decreased renal blood flow and clearance, and
(19) lacrimation or tearing.
Irritants can also induce hoarseness of voice and impair
mucociliary clearance functioning.
These physiological responses suggest that the respiratory system
may be at risk from harmful substances. Reflexive breath stoppage
(apnea) subsequent to stimulation of the trigeminal nerve in the upper
airway is probably a defensive device to prevent inhaling chemicals in
the air that might damage the lungs or respiratory tract.
This breath stoppage does not occur in isolation as evidenced by a
subsequent cascade of physiological symptoms associated with this
response. This nasal reflex induces activity in the sympathetic
division of the autonomic nervous system (ANS) leading to increasing in
circulating epinephrine.
This causes acceleration of heart rate and peripheral
vasoconstriction (leading to an increase in blood pressure). In
addition, activity in the sympathetic division of the ANS is often
associated with emotional induction of fear or anger.
Sustained exposure to irritating solvents can also impact
neurobehavioral functioning.
PAGE 20
These factors along with the unpleasant sensory properties of
irritation make strong trigeminal stimulation a memorable event, and one
which is likely to be regarded as highly aversive.
Lower airway irritation usually produces an increase in breathing
rate and pulmonary ventilation and little change in heart rate or blood
pressure. There are instances, however, in which lower airway
irritation can cause decreased respiratory rate (postexpiratory apnea).
Volatile chemical irritants can also cause local redness, edema,
pruritis or pain, and eventually altered function. Excessive
irritation in the lower airway (as well as upper airway) may lead to
tissue damage and, eventually, scarring. Airway irritation is also
associated with non-respiratory tract health complaints such as headache
and lassitude.
PAGE 21
Two types of nerve fibers in the trigeminal nerve conduct
nociceptive (pain) afferent pules: finely myelinated A-delta fibers and
un-myelinated C fibers.
Dull and burning painful sensations are characteristic of C fibers
while sharp, stinging sensations appear after activation of A-delta
fibers.
Activation of trigeminal C fibers by irritants leads to the release
of neuropeptides including substance P into the nose. Substance P
induces neurogenic inflammation including vasodilation, increased blood
flow, increased vascular permeability, increased ocular pressure and
pupillary contraction.
Substance P release is associated with an increased presence of
polymorphonuclear neutrophilic leukocytes (PMNs) in the nasal cavity
which indicates the presence of acute inflammation.
v
Exposure to 25 mg/m3 VOCs for 4 hours led to increased levels of
PMNs in nasal lavage fluid. The release of substance P by trigeminal
stimuli is also one potential mechanism by which trigeminal irritants
may cause head pain.
Vasculature in the cranium is supplied by substance P-containing C
fibers of the trigeminal nerve. Thus, inhaled irritants in the air
may induce headaches and migraines by increasing cortical blood flow via
the trigeminovascular system, i.e. via stimulation of a sensory
(trigeminal) nerve.
RELATIONSHIP BETWEEN TRIGEMINAL AND OLFACTORY SENSATIONS
There is often a temporal disparity between odor and irritant
sensations with odor sensations tending to precede the irritant
sensations. This is due in part to the fact that chemical agents
must migrate through the mucosa to activate free nerve endings of the
trigeminal nerve.
This fact coupled with the relatively slow transmission time of the
C fibers leads to a slowly responding system in comparison to
olfaction. Sensations of odor and irritation also respond different
to continuous chemosensory stimulation. Odor sensations tend to
fade quickly (adaptation) upon stimulation while irritancy can grow
sharply over a period of time though it may ultimately adapt to some
degree by six hours of exposure.
The growth of irritancy over time may be due in part to the
kinetics of overcoming the buffering capacity of nasal mucus or may
represent cumulative damage to structural elements.
Thus, odor is a warning of potential health symptoms from
irritation at elevated concentrations. Continuous exposure to
compounds such as AMMONIA or H2S can lead to odor fatigue and/or
tolerance, and this reduced sensitivity may jeopardize health when the
warning signal is not adequately perceived.
PAGE 22
Odorous VOCs have been found in the blood and brain after three
hours of exposure, and olfactory receptors have been shown to respond to
blood-borne odorants.
.....That is, odors can "mask" trigeminal stimuli and vice versa.
While masking does occur, the overall intensity of the experience is
rated as more intense as the concentrations of the two stimuli
increase. Stimulation of the nose and eye with low levels of odorous
VOCs are often either additive or synergistic, leading to responses
characteristic of irritants.
PAGE 23
WALKER and colleagues have studied respiratory responses following
stimulation of the eye and nose. Using a specially designed
olfactometer that provided different channels for the eye and nose, they
collected respiration data in human subjects to "nose only" and "eye +
nose" trials.
Using amyl acetate (a banana-like and relatively pleasant smell at
low concentration), they found that breathing flow rate increased at the
lower concentration presented to "nose only." At the highest
concentration of "nose only" administration, breathing flow was slightly
reduced. When the same stimuli were presented to the "eye + nose,"
subjects responded as if they had been exposed to far more amyl acetate,
that is, breathing was significantly reduced as a function of
concentration.
From these studies, it appears that receptors in the eye interact
with those in the nose to alter breathing and initiate respiratory
volume reductions at relatively low concentrations of chemical
stimulation.
The fact that odor sensations are linked so closely with irritant
sensations is due in part to the central projections of the olfactory
and trigeminal systems. The trigeminal nerve projects to fibers that
overlap with brain areas of the olfactory projection such as the
mediodorsal nucleus of the thalamus.
Additionally, the trigeminal nerve projects to many areas of the
brainstem associated with autonomic responses such as nasal secretion,
sneezing, and respiration.
Silver and Finger emphasized that these physiological reflexes are
"among the strongest in the body." The magnitude of these responses
underscores the evolutionary importance of olfaction as a warning and
response mobilization system.
PAGE 24
In addition, Cometto-Muniz and Cain found that thresholds for eye
irritation closely predict nasal irritation thresholds, and can serve as
a practical means to assess potency for nasal irritation in normosmics.
HUMAN ELECTROPHYSIOLOGICAL RESPONSES TO IRRITANTS
Electrophysiological methods for measuring responses to irritation
include peripheral negative mucosal potentials (NMPs) and central
event-related potentials (ERPs).
PAGE 25
NMPs are recorded by means of an electrode on the septal wall of
the nasal cavity along the line between bony and cartilaginous parts of
the nose (referenced against the contralateral bridge of the nose).
The NMPs are thought to result from activation of both C-fibers and
A-delta fibers.
Reflexive changes in nasal blood flow to irritants can be measured
using a laser Doppler flow meter. Pneumotachograph measurements
indicate that there is a reduction of tidal volume (volume per breath)
that begins at the threshold of nasal irritation.
The RD50 (50% decrease in respiratory frequency) is calculated from
the log concentration-response curve. A computerized version of this
test has been developed to quantify breathing patterns in
unanesthetized mice exposed to volatile chemicals.
It should be noted that reflex momentary apnea (interruption of
inhalation) in response to irritation can also be recorded in humans.
Apnea is reflexive response to irritant stimulation that protects the
upper airway.
Breathing patterns before, during, and after presentation of
various concentrations of a potential irritant can be used to determine
the concentration sufficient to elicit the reflex.
PAGE 26
While bioassays of irritation in animals can provide helpful
information, current research suggests that humans are more sensitive to
irritation than animals.
EVIDENCE FOR PARADIGM 2: HEALTH SYMPTOMS OCCUR AT ODORANT
CONCENTRATIONS THAT ARE NOT IRRITATING
Historically, malodor has been considered an indicator of potential
health risk. However, the mechanism by which unpleasant odors cause
health complaints in the absence of irritation or toxicity is poorly
understood. Health complaints do occur at levels of VOCs that are
below irritant thresholds.
There is extensive animal literature that indicates that airborne
chemicals can affect behavior. In humans, airborne chemical signals
have even been shown to affect ovulation.
PHYSIOLOGICAL RESPONSES TO AN UNPLEASANT ODOR IN THE ABSENCE OF
IRRITATION
In one study, fourteen of 26 workers exposed to presumably safe
levels of odorous sewer gases (as measured by gas detection equipment)
experienced sore throat, cough, chest tightness, breathlessness, thirst,
sweating, irritability, and loss of libido.
Severity of symptoms was dose related. Clinical follow up showed
deteriorating respiratory symptoms and lung function tests in the most
seriously affected.
Chemical analysis showed that the workers had been exposed to a
mixture of thiols and sulfides. In another study, expose to the odor
of n-propyl mercaptan in an agricultural setting for 6 weeks led to
significant exposure effects including headache, diarrhea, runny nose,
sore throat, burning/itching eyes, fever, hay fever attacks, and asthma
attacks.
The mechanism by which these unpleasant odors induced health
symptoms in the absence of irritation or toxicity is not know.
However, Gift and Foureman reported that the RD50 values (concentration
that induces 50% decrease in respiratory rate) for a random sample of
unpleasant smelling compounds were much lower than for pleasant smelling
compounds.
Schiffman found that shallow and irregular breathing patterns were
induced by exposure to unpleasant odors (swine odors, rotten fish,
SULFIDES) while deeper stable breathing patterns were characteristic of
exposure to pleasant odors (chocolate chip cookies, orange cake).
These differences in breathing patterns (whether genetic or learned) may
influence health symptoms.
Electroencephalography (EEG) and functional magnetic resonance
imaging (fMRI) studies have even shown that odorants and airborne
chemicals can affect the nervous system without being consciously
detected.
v
MOOD IMPAIRMENT AND STRESS INDUCED BY AN UNPLEASANT ODOR
(PAGES 27 - 28)
Odors perceived to be unpleasant can impair mood and increase
reactivity to startling stimuli.
Negative mood, stress, and environmental worry can potentially lead
to a number of physiological and biochemical changes with subsequent
health consequences. These include elevations in blood pressure, both
in normotensives and in patients with hypertension, immune impairment,
increased levels of peripheral catecholamines, increased
glucocorticoids, increased secretion of adrenocorticotropic hormone
(ACTH) from the pituitary, decreased gastric motility, increased scalp
muscle tension in patients with muscle tension headaches, and even
hippocampal damage.
Chronic stress has been associated with development of coronary
artery disease, chronic hypertension, and structural changes of the
heart in some studies.
Thus, if odorous stimuli are sufficiently stressful, this could
potentially elevate the catecholamines epinephrine and norepinephrine to
levels that produce adverse cariovascular effects including increased
heart rate and blood pressure and increased tendency of blood to clot.
LEARNED ASSOCIATIONS AND HEALTH SYMPTOMS
PAGE 29
Odors can modify synaptic plasticity in the hippocampus and
piriform cortex (parts of the limbic system) which are associated with
learning and emotion.
Odor-conditioned panic attacks or panic disorder have been reported
after exposure to odors in the workplace. Whether these learned
responses should be deemed "health effects" from odors, however, is
controversial because the term "health" has multiple meanings in
scientific, regulatory, and legal settings.
According to the World Health Organization (WHO), the definition of
"health" is
"...a state of complete physical, mental, and social well-being and not
merely the absence of disease or infirmity." Thus, a symptom that
diminishes physical, mental, or social well -being would be a "health
effect" according to WHO.
The majority of the participants at the Health Effects of Odors
workshop considered it appropriate to explore health effects of odors
within the WHO definition of health.
Participants at a subsequent workshop sponsored by the Centers for
Disease Control also agreed the potential health effects associated with
exposure to confined animal feeding operations (CAFOs) should be viewed
according to the WHO definition of health.
Frist emphasized that reactions to odors such as nausea, headache,
loss of sleep, and loss of appetite clearly represent a matter for
public-health concern and attention under the WHO definition of health.
Using a broad definition of health that includes quality of life
and social and mental well-being, Matchell et al concluded that
malodorous air in an urban environment causes adverse health effects.
PAGE 31
INDIVIDUAL DIFFERENCES IN PHYSIOLOGICAL RESPONSES TO ODORS
... Odor intolerance has been associated with increased
cardiopulmonary risk including increased sympathetic tone in the
cardiovascular system at rest, different EEG alpha rhythms, lower
rapid-eye-movement (REM) sleep, and greater prevalence of chronic cough,
PHLEGM, wheeze, chest tightness, exertional dyspnea, acute respiratory
illnesses, hay fever, child respiratory trouble, and physician confirmed
asthma.
The reasons for these biological responses in odor-intolerant
individuals are not known but mesolimbic systems could account in part
for many of the cognitive, affective, and somatic symptoms.
v
...Karol suggested that inhalation of airborne chemicals can
augment allergic sensitization with episodic pulmonary reactions
occurring on subsequent exposures. These reasons could involve the
upper respiratory tract (rhinitis), lower respiratory tract (wheeze,
bronchospasm), or systemic immune involvement (febrile response).
While the mechanisms of sensitization are not well understood, mediators
of immunity are definitely involved.
EVIDENCE FOR PARADIGM 3: A CO-POLLUTANT IN AN ODOROUS MIXTURE IS
RESPONSIBLE FOR THE REPORTED HEALTH SYMPTOM
PAGES 31 - 32
In agricultural settings, odorant mixtures typically conain
co-pollutants such as particulates, endotoxin, and pesticides.
Particulates can arise from confinement building exhausts, dry feedlots,
composting facilities, lagoons, and land application sprays.
Particulates from intensive animal housing consist mainly of manure,
dander (hair and skin cells), molds, pollen, grains, insect parts,
mineral ash, feathers, indotoxin, and feed dust.
AIRBORNE DUST PARTICLES CAN CONCENTRATE ODORANTS SUCH AS ORGANIC
ACIDS AND AMMONIA ON THEIR SURFACES; this contributes to odor potential
and exacerbates irritancy induced by dust in the respiratory tract.
LExperimental studies have found a strong link between odor/irritation
intensity and levels of particulates.
v
PARTICULATES ASSOCIATED WITH FECAL WASTE ARE ALSO KNOWN TO CARRY
BACTERIA. Thus, it is likely that some of the health complaints
ascribed to odor may, in fact, be caused by particulate matter (liquid
or solid) suspended in air or by a synergistic effect between odorants
and particulates.
A SYNERGISTIC EFFECT OF AMMONIA AND DUST EXPOSURE has been reported
in a study of 200 poultry facilities. The adverse health effects of
ammonia and particulates in combination was greater than the additive
effect of ammonia and particulates by a factor of 1.5 to 2.0.
v Both fine and coarse particles in an odorous plume enter the nasal
cavity and can induce nasal irritation. However, these particles
differ in the degree to which they traverse the respiratory tract.
v
Fine particles include particulate matter with sizes less than 2.5
uM (PM2.5). These particles are more likely than coarse particles to
cause respiratory health effects betcause they reach the gas-exchange
region of the lung.
Ultra-fine particles (i.e., those with a diameter 0.1 uM or less)
may be even more toxic than larger sized particles producing severe
pulmonary inflammation and damage and even affecting mortality.
Fine particles remain suspended in the atmosphere for days and can
be transported thousands of miles. Particles with sizes from 2.5 uM to
10 uM (PM 2.5-10) are coarse particles that enter the thorax and may
also induce health effects.
There is an overlap of fine and coarse mode particles in the
intermodal region of 1 to 3 uM. Coarse particles are usually
mechanically generated.
Sources of coarse particles near confined animal operations AND
OTHER LOCATIONS OF BIOSOLIDS include windblown dust from soil, feed,
manure, unpaved roads, pollen, mold spores, parts of plants and insects,
and evaporation of aqueous sprays.
PAGES 32 -33
Fine particles may be formed in the atmosphere from gases through
the processes of nucleation and growth. Nucleation entails formation
of very small particles from gases.
.....Another example is the oxidation of NO2 to nitric acid (HNO3) which
reacts with ammonia (NH3) to form fine particles of ammonium nitrate.
Ammonia salts that exist as fine aerosols can be transported long-range
in the atmosphere.
Third, photochemical reactions generate ozone and OH-, and these
react with organic gases (such as odorous compounds) to form materials
with low vapor pressure that can nucleate or condense on existing
particles.
Epidemiologic studies of exposure to particulates have reported
statistical associations between daily changes in health outcomes such
as mortality and daily variations in the concentrations of different
sizes of ambient particulate matter.
There is considerable epidemiological evidence predominantly from
urban settings that exposure to increased levels of particulates is
associated with increased mortality risk, especially among the elderly
and individuals with preexisting cardiopulmonary diseases, such as
chronic obstructive pulmonary disease (COPD), pneumonia, and chronic
heart disease.
There is also epidemiological evidence that particulate exposure
can increase the risk of respiratory and cardiovascular morbidity such
as increased hospital admissions or emergency room visits for asthma or
other respiratory problems, increased incidence of respiratory symptoms,
or alterations in pulmonary function.
PAGE 34
.... First, time-averaged sampling of dust downwind gives lower values
than the peak dust levels because the samplers are usually in the plume
for only a short period of time due to shifts in the wind direction.
Second, the geographical location where the plume reaches the level
of potential perception e.g. a neighbor's nose) may be a small physical
area that is difficult to locate for measurement purposes in real time.
Third, particulates from the swine confinement houses and
particulates from the lagoon may both contribute to the exposure but may
or my not occur simultaneously
BACTERIAL exposures e responsible for some health complains from
exposure to odorous emissions from agricultural operations. Bacteria
are ubiquitous in swine houses; furthermore, aerosols formed over
lagoons may allow the transfer of bacteria from the water into the air
with transfer downwind in aerosol droplets.
ENDOTOXIN, a heat-stable toxin associated with the outer membranes
of certain gram-negative bacteria, can reach levels as high s 2,410
ng/m3 to 78,600 ng/m3 in swine facilities.
The American Conference of Governmental Industrial Hygienists'
Threshold Limit Value-Time Weighted Average (ACGIH TLV-TWA for endotoxin
is 10 ng/m3; that is the time-weighed average concentration for a
conventional 8-hour workday and 40-hour workweek, to which nearly all
workers may be repeatedly exposed daily without adverse effects.
ENDOTOXINS CAUSE AN INFLAMMATORY RESPONSE OF THE RESPIRATORY
TRACT. Atopic asthmatic individuals have elevated sensitivity to
respirable endotoxin which results in a variety of immune responses
including increased eosinophils in the airways.
PAGE 35
Furthermore, exposure allergens in atopic asthmatic individuals
augments subsequent endotoxin-induced nasal inflammation
Studies that trace the transport of odorous VOCs within olfactory
and trigeminal nerves may also be helpful in understanding health
effects of odors.
Both small and large molecules can be transported to the brain in
the olfactory and trigeminal nerves.
THUS, ODOROUS CO-POLLUTANTS SUCH AS VIRUSES THAT ENTER THE NOSE CAN
POTENTIALLY REACH THE CENTRAL NERVOUS SYSTEM BY NEURON TO NEURON
TRANSMISSION.
v For example, herpes simplex virus can infect the trigeminal nerve
and ultimately enter the CNS. VIRUSES can also infect olfactory
receptor neurons. However, fare more research is needed to
determine if any health effects from exposure to odorous emissions from
agricultural facilities OR BIOSOLIDS are due to transport of VOCs of
viruses in nasal sensory nerves.
Further research is also required to determine if the levels of
dust, ENDOTOXIN, or other co-pollutants (such as flying insects)
transported in odorous plumes are high enough to cause health symptoms
in neighbors of agricultural or municipal operations.
Flying insects are attracted to odors from urine, feces and gut
mucus and often follow odor plumes to find resources. Flying insects
have the potential to carry disease.
ASTHMA AND ALLERGIES
Odors have been reported to exacerbate symptoms of asthma but it is
not clear whether the main cause of this worsening is due to direct
irritation of mucous membranes by the odorant, to sensory stimulation of
the olfactory and/or trigeminal nerve, or to prior conditioning.
Asthma is characterized by bronchial hyperresponsiveness and
mucosal airway inflammation; it is the leading chronic illness among
adults and children.
Epithelial damage and epithelial shedding occur in the airway
passages in asthma
as well as other respiratory disorders including nasal allergy and
infantile wheeze.
PAGE 36
Even healthy individuals exposed to a polluted environment (e.g.
ozone) can experience epithelial shedding which can last up to 2 weeks
or more. Nerve endings are exposed by epithelial shedding; this allows
VOCs and particulates access to free nerve endings which augments
irritation from inhaled pollutants. Irritants can then set up a low
grade neurogenic inflammation with leukocyte recruitment that aggravates
asthma and allergy. IT HAS BEEN SUGGESTED THAT EVEN ANAPHYLAXIS can
be triggered by chemical odors.
OCCUPATIONAL AND ENVIRONMENTAL EXPOSURE
There are health risks associated with prolonged exposure to highly
odorous ambient air in the work or home environment. Persistent
asthma-like symptoms can result from a single excessively high
environmental or occupational exposure to odorous/irritant substances
such as paint, floor sealant, AMMONIA, chlorine, acetic acid, and
hydrogen sulfide from manure.
This syndrome was termed RADS (reactive airways dysfunction
syndrome) by
Brooks et al. The duration of the single exposure can be as short as a
few minutes to as long as 12 hours.
RADS, by definition, occurs in persons with no evidence of
preexisting pulmonary disease. Another defining characteristic is
that symptoms can persist after termination of the exposure for at least
three months; but in fact they may persist for one year or more.
Bronchial biopsies suggest respiratory epithelial injury, but the
mechanisms operative in the syndrome appear to be nonimmunological.
Persons with RADS were generally aware of an odor that was present
during the irritant exposure.
...Documented irritant odorant exposures include hydrogen sulfide,
AMMONIA, and dust.
PAGE 37
....Cronic bronchitis, occupational (non-allergic) asthma, and
non-infectious chronic sinusitis are also prevalent among pig farmers.
THESE SYMPTOMS CAN BE INDUCED BY ODOROUS AND IRRITANT VOCS AS WELL
AS DUST AND ENDOTOXIN. There appears to be a synergistic effect
between volatile compounds and dust exposure in producing these
symptoms. Symptoms appear to be progressive with an annual decline in
lung function.
Health symptoms can also occur acutely and reversibly with even
brief exposure to odorous and dusty agricultural environments.
QUANTIFICATION OF HEALTH SYMPTOMS
Workshop participants concluded that current evidence suggests that
the symptoms complaints experienced by neighbors of some odorous animal
operations AND OTHER SOURCES OF BIOSOLIDS may constitute health effects.
.....A set of potential study tools and biomarkers were proposed at
the workshop to validate odor-related symptoms in clinical,
epidemiologic, and research studies. These are given in Table 1.
Workshop participants stressed the need to relate these health measures
to levels of exposure.
QUANTIFICATION OF HEALTH SYMPTOMS
PAGE 39
Accurate methods to quantify odorous emissions are necessary to
determine the relation between potential health symptoms and odors.
.....Furthermore there is wide variability among individuals in the
odor intensities and odorant concentrations that cause health
complaints.
PAGE 41 - 42 - OLFACTOMETRY
.....While the acceptability of the odor of some VOCs depends on
learned or cultural factors (experience), odors of other compounds such
as H2S, MERCAPTANS, AMINES, and nitrogenous heterocylic compounds are
considered offensivve by most individuals.
PAGE 43
....One limitation with using GC/MS) (gas chromatography/mass
spectrometry) to quantify odor is that the individual odorous compounds
may not smell unpleasant at the concentrations in the mixture, yet the
mixture (or combination of odorous compounds) may smell bad.
Furthermore, the concentration of individual component compounds (or
even concentration of total volatile organics) may not predict the level
of odor potential.
.....A drawback to current E-nose (electronic nose) models,
however, is that they are sensitive only in the high ppb or ppm range
while the human nose has exquisite sensitivity in the ppt range
OTHER METHODS FOR ASSESSING ODOROUS
OTHER METHODS FOR ASSESSING ODOROUS EMISSIONS
PAGES 43 - 44
Measurements of the number of particulates (as well as their odor
quality) before, during, and after treatments can also be obtained in
order to evaluate the amount of odor carried on particles (dust)
compared to that carried in gaseous form.
Dust can be collected simultaneously on the farmer's property and
on the neighbor's property using Andersen Non -Viable Eight-Stage
Impactor Kits or other such devices.
These dust samples can be dissolved in water or other diluent
(e.g., just as dust dissolves in mucus) and evaluated for odor by the
trained panel using static olfactometry.
Any odors from dust on the farmer's property may be compared to
odors from dust on the neighboring property to determine if they come
from the same source.
.....Levels of marker compounds such as AMMONIA and hydrogen
sulfide can also be obtained at the houses, lagoon, property line, and
at the neighbor's home. However, correlations between odor intensity
and levels of hydrogen sulfide or ammonia have been inconsistent.
PAGE 44 - 45
MANAGEMENT OF ODOR EMISSIONS
v
.....In addition to animal operations, compost facilities are under
increasing pressure to address odor emissions. Organic materials
composted at such facilities include wastewater treatment residuals
(BIOSOLIDS/SLUDGE), yard waste (grass, vegetables, SLUDGES, animal
wastes (manures and carcasses), municipal solid wastes (separated or
unseparated), and industrial organics.
Odor emissions have been a factor in closure of several expensive
compost facilities and are a significant obstacles to the implementation
of composting as a waste management option in a number of locations.
v
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PAGES 57 - 58
FINAL COMMENTS
v
Our current state of knowledge clearly suggests that it is possible
for odorous emissions from animal operations, wastewater treatment and
recycling of biosolids to have an impact on physical health.
The most frequently reported symptoms attributed to odors include
eye, nose, and throat irritation, headache, nausea, hoarseness, cough,
nasal congestion, palpitations, shortness of breath, stress, drowsiness,
and alterations in mood.
Many of these symptoms (especially irritation, headache,
hoarseness, cough, nasal congestion, and shortness of breath) can be
caused by stimulation of the trigeminal nerve in the nose at elevated
levels of odorous VOCs.
Co-pollutants in an odorous plume may also play a role. A genetic
basis for some odor aversions may be the basis for complains from
unpleasant but nonirritating odors; unpleasant odors have been shown to
activate different brain areas than pleasant ones.
Most published studies indicate that there are occupational health
risks to workers in intensive livestock units who are exposed
continuously to high concentrations of odorous VOCs, particulates, and
microbes.
However, more scientific data are necessary to quantify health
symptoms from the types of exposures experienced by neighbors downwind
of livestock or wastewater operations (e.g. continuous exposure to the
lower levels of odorous emissions or intermittent exposure to high
levels from temporary discharges).
Objective scientific data must be obtained that relate specific
concentrations of VOCs, particulates (including ammonium aerosols), and
microorganisms alone and in combination to objective measures of health
symptoms.
TLhere are many potential study tools and biomarkers for the
validation of odor-related health symptoms in clinical, edpidemiologic,
and research studies (see Table 1).
These tools and biomarkers will be helpful in distinguishing
between direct health effects (e.g. sensory irritation) and indirect
effects (e.g. stress).
Objective measures of health effects must then be related to the
concentrations of odorous emissions as well as frequency and duration of
exposure. A variety of methods are available to quantify odorous
emissions including olfactometry, gas chromatography, and the electronic
nose. However, there is still a need to develop portable, reliable,
and sensitive sensors for field measurement of odorous emissions in real
time.
Future studies will help establish minimal risk levels (MRLs) for
odorous emissions analogous to those utilized by the Agency for Toxic
Substances and Disease Registry (ATSDR), that is, substance-specific
minimal risk levels (MRLs) to evaluate health effects.
MRLs are defined as "estimates of daily human exposure to a
chemical that are likely to be without an appreciable risk of adverse
noncancer health effects over a specified duration of exposure."
In addition, knowledge of MRLs for odorous emission will assist in
the development and implementation of cost-effective odor-abatement
techniques that will enable operators of livestock and wastewater
operations to meet performance standards.
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**
ADDITIONAL INFORMATION FROM OTHER SOURCES:
(1) US EPA acknowledges in Appendix A of sludge Stockpiling Guide
(available on line) that sewage sludge emits odor-causing gases
including dimethyl sulfide, dimethyl disulfide, methyl mercaptan,
trimethylamine and ammonia. OSHA, CDC, NIOSH, DOT, etc. all warn
about serious health effects from inhalation of these toxic gases.
(2) 1999 Ecological Risk Assessment by Dowd, Gerba, Pepper and
Pillai found that neighbors within 1640 feet of sludge-spraying
operations are at high risk from " ...exposure to microbial pathogens
from biosolids via aerosols."
Neighbors within 1640 feet of sludge stockpiles and landspreading
operations are also at significant risk from bacteria from sludge
aerosols, particularly if exposed to these airborne pathogens for over 8
hours with wind speeds ll m.p.h.
(3) The National Institute of Occupational Safety and Health
(NIOSH) has issued TWO Health Hazard Evaluations finding that sludge
workers are exposed to airborne enteric bacteria and endotoxins from
gram negative bacteria. NIOSH says these pathogens are associated
with gastrointestinal symptoms and illnesses which have been reported by
sludge workers and others in close proximity to sludge sites.
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**
To obtain a complete copy of JOURNAL OF AGROMEDICINE, Volume 7,
Number 1 2000 - ISSN: 1059-924X which contains this article:
"POTENTIAL HEALTH EFFECTS OF ODOR FROM ANIMAL OPERATIONS, WASTEWATER
TREATMENT AND RECYCLING OF BYPRODUCTS"
THE COST IS $12.00 BY CREDIT CARD
contact:
JANETTE A. KEMMERER
OR call toll free: 1-800-429-6784
OR FAX: 1-800-895-0582
Helane Shields, Alton, NH 03809 phone/fax 603-875-3842
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