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Potential
Health Effects of Odor From Animal Operations, Wastewater Treatment, and
Recycling of Byproducts
Susan
S. Schiffman, PhD, Duke University, NC
John M. Walker, PhD, US EPA, Office of Water (sludge office)
Pam Dalton, PhD
Tyler S. Lorig, PhD
James H. Raymer, PhD
Dennis Shusterman, MD
C. Mike Williams, PhD
ABSTRACT.
Complaints of health symptoms from ambient odors have become more frequent
in communities with confined animal facilities, wastewater treatment
plants, AND BIOSOLIDS RECYCLING OPERATIONS.
The
most frequently reported health complaints include eye, nose, and throat
irritation, headache, nausea, diarrhea, hoarseness, sore throat, cough,
chest tightness, nasal congestion, palpitations, shortness of breath,
stress, drowsiness, and alterations in mood.
Typically,
these symptoms occur at the time of exposure and remit after a short
period of time. However, for sensitive individuals such as asthmatic
patients, exposure to odors may induce health symptoms that persist for
longer periods of time as well as aggravate existing medical conditions.
A
workshop was held at Duke University on April 16-17, 1998 cosponsored by
Duke University, the Environmental Protection Agency (EPA), and National
Institute on Deafness and Other Communication Disorders (NIDCD) to assess
the current state of knowledge regarding the health effects of ambient
odors.
This
report summarizes the conclusions from the Workshop regarding the
potential mechanisms responsible for health symptoms from ambient odors.
Methods for validation of health symptoms, presence of odor, and efficacy
of odor management techniques are described as well.
(Article
copies available for a fee from The Haworth Document Delivery Service:
1-800-342-9678. E-mail address: getinfo@haworthpressinc.com
Website: http://www.HaworthPress.com
E
X C E R P T S
FROM
R E P O R T
PAGE
8
KEYWORDS:
Health effects, odor, nasal irritation, irritant, confined animal
feeding operations (CAFOs), dust, particulates, wastewater treatment,
BIOSOLIDS, composting.
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
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
olfactory epithelium in the top of the nasal cavity. Signals from
activated receptors are transmitted via the olfactory nerve (first cranial
nerve) 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.)
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
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 does
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, 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.
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 is 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.
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 cardiovascular 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.
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. Experimental studies
have found a strong link between odor/irritation intensity and levels of
particulates.
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.
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.
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 because 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 may 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.
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 hyper responsiveness 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
Chronic
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 offensive 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 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 dilutent (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
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.
PAGES
57 - 58
FINAL
COMMENTS
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.
There
are many potential study tools and biomarkers for the validation of
odor-related health symptoms in clinical, epidemiological, 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.
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
11 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.
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
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