WORKING PAPERS
for the Conference on
THE DOSE-RESPONSE RELATIONSHIPS
AFFECTING HUMAN REACTIONS
TO ODOROUS COMPOUNDS
a symposium sponsored by
ENVIRONMENTAL PROTECTION AGENCY
AIR POLLUTION CONTROL OFFICE
CAMBRIDGE, MASSACHUSETTS
APRIL 26-27, 1971
Arthur D Little, Inc.
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WORKING PAPERS FOR THE CONFERENCE ON
THE DOSE-RESPONSE RELATIONSHIPS AFFECTING HUMAN
REACTIONS TO ODOROUS COMPOUNDS
A Symposium Sponsored by
Environmental Protection Agency
Air Pollution Control Office
Arthur D. Little, Inc.
Cambridge, Massachusetts USA
April 26-27, 1971
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WORKING PAPERS FOR THE CONFERENCE ON
THE DOSE-RESPONSE RELATIONSHIPS AFFECTING HUMAN
REACTIONS TO ODOROUS COMPOUNDS
I. THE DOSE - DESCRIPTION OF THE STIMULI
Page
Odorant Sources in Air Pollution 1
Dr. Kenneth D. Johnson
Properties of Odorants 9
Dr. Amos Turk
Predicting Odor Frequencies by Dispersion Calculations 15,
Dr. Ulf Hb'gstrom
II. RESPONSE - EFFECTS OBSERVED WITHIN THE INDIVIDUAL
Neurological Responses to Odorants 25
Prof.Dr. Helmut Altner
Sensory Evaluation of Odors in the Ambient Air 35
Thomas Lindvall, M.D.
Method and Theory of Odor Preference 59
Dr. Trygg Engen
Physiological Responses to Odorants 91
David A. Kendall
III. RESPONSE - EFFECTS OBSERVED WITHIN HUMAN POPULATIONS
On Annoyance Reactions Observed Within Human Populations 123
Dr. Erland Jonsson
Studies of Public Opinion of a Traffic Odor 131
Mr. Karl J. Springer
Property Value Differentials as a Measure of 161
Economic Costs Due to Odors
R. David Flesh
Health. Effects and Annoyance Reactions to Pulp Mill 177
Odor in a Rural Community
Margaret Deane and John R. Goldsmith
iii
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IV. SUMMARY OF THE PROBLEMS IN ODOROUS AIR POLLUTION
Summary of Technical Problems 201
Lars Friberg, M.D.
Summary of the Problems in Odorous Air Pollution 213
in Japan
Takeo Suzuki, M.D.
Administrative Mechanisms Available for Control of 221
Odorous Compounds Under the U.S. Clean Air Act
As Amended
Dr. D. S. Earth
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ODORANT SOURCES IN AIR POLLUTION
Kenneth D. Johnson
It is always satisfying to a lead-off speaker to a symposium
such as this, if he is able to provide a nearly organized and cate-
gorized arrangement of the subject matter to be discussed by the ensuing
speakers. It provides him with a sense of having drawn a road map
steering the participants directly to their destination. They may,
or may not, make much progress along that route, but after all, you can't
expect him to do the whole job, can you?
On this occasion, I can not bask in any such glow of self-
satisfaction. I cannot offer you a chart neatly ruled off with lines of
latitude and longitude, and with primary and secondary route markers
carefully inscribed on well-defined courses. Although we share an ill-
defined sense of the direction in which we wish to move, I cannot even
provide you with a reliable compass. The best I can do is to point out
some clumps of moss in the thick forest of often conflicting, confusing
and nebulous observations that constitute our data base. Hopefully,
from the location and character of these mossy growths, we can keep
oriented in these woods even though no Pole Star is visible.
The difficulty in attempting an all-inclusive classification of odors,
or more properly, of odorous substances, is that no property is common to
them all, other than their propensity to stimulate certain nerve endings
in the nasal passages of homo sapiens. At the present state of knowledge,
or even of broadly applicable theory, we are not even sure of the mechanism
by which these molecules initiate the nerve impulse, nor do we know the
means by which our exquisitely discriminatory sensory apparatus is able
to distinguish among the thousands of odorants—not only the naturally
occurring ones that may have exerted an influence on the evolutionary
development of the odor sense, but the products of the organic syn-
thesist's art, as well.
Odors are nothing new to society, odor "problems" are of far
shorter duration. An odor becomes a problem when there exists a
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possibility of a solution. Until that time, it is merely a facet of the
environment to which its occupants must become acclimated. Odors are
now recognized more frequently as problems because we now have technology,
and the capability of developing new technology, that gives us hope of
elimination of any particular odorant from our environment. Not all odors,
mind you, nor necessarily at all times. ' One of the still unsolved prob-
lems, and one that, in particular, is facing this group before me today,
is the matter of how we decide which odor problems require the initial
efforts toward solution, and what distribution of available effort among
the many coexisting odor problems will produce the greatest environmental
improvement. An improvement measured by the reduction in some still un-
defined "weighted average" of residual odor nuisances.
Your program chairman has asked me to discuss Odorant Sources in
Air Pollution. Perhaps the last two words of this title are redundant.
If we accept the definition of "pollution" as the presence in the air of
some material that detracts from a beneficial use of the atmosphere, I ex-
pect that any odor, no matter how pleasing it may be to most people on
most occasions, could, under some conditions, be a source of annoyance,
or interference with desired activities, even if it is a lingering scent
of Chanel No. 5 on a man's coat lapel when his wife uses Arpege.
Whether a given odorant evokes pleasant or disagreeable emotions in
a subject is strongly dependent upon the experiences with which previous
exposures to that odor are associated. Even odors that are normally
considered as generally unpleasant or obnoxious, may, in an appropriate
frame of reference, stimulate pleasurable reactions. I confess that,
for me, the occasional perception of the mercaptans discharged by an
aroused skunk, when appropriately diluted by travel on an evening breeze,
or the characteristic fresh manure odor of a dairy milking barn stir
quite pleasant feelings of nostalgia for the bucolic scenes of a rural
childhood, rather than impinging upon my nostrils as the stenches that
these odorants are normally considered to constitute.
However, whether our subjective evaluations are conditioned by
current social patterns or genetic factors developed over the long course
of man's development, it must be recognized that certain kinds of odors
are generally regarded as unpleasant or offensive. Air pollution
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abatement programs, as expressions of political decisions based upon
the value judgements of large sections of the population, will inevitably
first focus their odor control efforts on those situations where sub-
stantial populations are exposed to high frequencies or intensities of
such odors. Our industrial society brings large quantities of odorant
materials into close proximity with social units of high population
density, thus it often has exacerbated odor nuisance problems at a time
when society has become far less tolerant of odors in our environment.
This intolerance has been strongly stimulated by outstanding
accomplishments of our technology in minimizing the odors that arose in
earlier times as the cities outgrew their ability to handle garbage and
sewage. These were the major sources of a pervasive effluvia that
characterized our cities of a century or more ago. If I may be for-
given for allowing a reference to water pollution to intrude into this
meeting, I would like to quote from Coleridge's Cologne;
In Koln, a town of monks and bones,
And pavements fang'd with murderous stones
And rags and hags, and hideous wenches;
I counted two and seventy stenches,
All well defined, and several stinks.
Ye Humphs that reign o'er sewers and sinks,
The river Rhine, it is well known,
Doth wash your city of Cologne;
But tell me, Nymphs, what power divine
Shall henceforth wash the river Rhine?
Under some circumstances, even entire countries can be contaminated
by the stench of decaying animal matter. In Exodus 8:13, 14 we read
in the description of the plague of frogs: "... and the frogs died out of the
of the houses, out of the villages, and out of the fields. And they gathered
gathered them upon heaps: and the land stank."
Today we are unlikely to suffer a plague of frogs, but it is
quite possible that a plant processing frog legs for the frozen foods
trade, might, as a consequence of its waste accumulation and disposal,
constitute a neighborhood nuisance.
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It would not be particularly constructive for me to attempt a com-
prehensive catalogue of odor sources, or to try to characterize the
problems associated with each. Even a casual review of the literature
would reveal that almost every major industrial operation has been
accused of being an odor nuisance source at one time or another. I
will try to focus our attention on industrial sources, since, as I have
earlier^pointed out, these do often have greater social impact and
are associated with institutions that are more likely to have the
economic and technological resources to do something about them.
The greatest defense against the creation of an odor nuisance from
an industrial operation is a tightly closed system, and the hardest
systems to close are those that involve manual handling of process
materials. Such operations on plant or animal material, in which
the requirement for manual steps as trimming, sorting, selecting, etc.
and from which putrescible wastes result, have a long history of odor
problems. They face a most difficult problem in developing technology
for odor reduction and control. Meat packing and leather tanning are
classical examples. The variability of the raw material and the need
for the operator to exercise judgment precludes the automatization of
most steps in their processes, and make the full enclosure of the pro-
cessing operations unfeasible.
After the biological processes of putrefaction, perhaps the thermal
or pyrolytic processes are the next most commonly subject to nuisance
odor problems. Whereas the final products of oxidation of organics
are generally of rather low odor intensity, the intermediates generated
by heat, either in the absence of adequate oxygen, or at temperatures
not high enough to achieve complete oxidation, often tend to be highly
odorousv, and offensive or irritating. Among the industrial processes
that would fall into this classification, we note: coke making,
asphalt blowing and asphaltic tile and roofing manufacture, heat curing
of plastics and protective coatings, core baking and metals founding,
meat smoking and coffee roasting. To these we may add the poorly
controlled or inadequately designed combustion processes, such as
lumber mill wastes incineration of tepee burners, or the almost, but
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not quite complete oxidation of petroleum fuels in a diesel engine,
that discharge such pyrolyzed materials as a foreseeable, but un-
intentional consequence of their operations.
It would be presumptuous of me to attempt to summarize to this
audience the odor sources and problems control of the pulp and papper
industry. Its odor sources run the gamut from those growing out of
the biological degradation of wastes, through the range of incomplete
oxidation products from their recovery furnaces, to the mercaptans and
sulfides synthesized as unwanted by-products in the Kraft process.
The scale of their operations, and the intensities and qualities of
their odorants, have combined to bring this industry into a quite un-
welcome prominence in any forum in which industrial odor problems
are discussed.
Many of our industrial odor problems are related, not to an
ill-defined and highly complex mixture of products resulting from a
biological or thermal process, but to a specific chemical intentionally
introduced into, or produced by, an industrial operation. The carbon
disulfide of the viscose rayon process, or the plastics monomer, ethyl
aerylate, are typical examples.
As a broad generalization, one could predict that wherever the
nuisance odor threshold of a given chemical lies well below that con-
centration that constitutes a serious hazard from the toxicity or fire
or explosion standpoint, some user, at some time, may be expected to
allow it to create an odor problem. The frequency and extent of such
odor problems will be determined more by the number and distribution
of that chemical's uses and users, than by its intrinsic properties
as an odorant. Of course, other things being equal, those chemicals
with the highest ratio between vapor pressures and detection thresholds,
and the most unpleasant odor notes, may be expected to generate the
greatest number of complaints.
I do not wish to dwell at any length on the peculiar position
occupied by compounds of sulfur in the odor spectrum. The high in-
cidence of malodorous compounds in this chemical family was noted
early. This propensity, when combined with the high susceptibility
of sulfur and its compounds to biological and chemical interconversions,
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makes the sulfur compounds frequent culprits in industrial odor problems.
Thus even as inert and inoffensive a material as elementary sulfur may,
in storage, be the source of substantial quantities of hydrogen sulfide
as a result of microbial action. The mercaptans present in crude
petroleum, the thiophenes of coal tars, as well as the'sulfides and mer-
captans present in the products of putrefaction, are all frequent sources
of odorous air pollution.
If we mention sulfur as of frequent occurrence in compounds of
strong and often unpleasant odor, we must similarly acknowledge
nitrogen. As a major essential element in all living things, it is
a ubiquitous component of all industrial raw materials derived from
plant or animal sources, and, like sulfur, is subject to facile micro-
bial conversion into compounds that are both readily volatile and highly
odorous. As in the case of sulfur, the compounds in which this element
is in the reduced valence state are usually the more potent trouble
makers. Thus methyl amines, whether evolved from fish wastes or
synthesized as raw materials for surfactant manufacture, are a fre-
quently observed source of odorous air pollution. Again, in parallel
to what we have observed in the case of sulfur, the heterocyclic nitro-
gen compounds also have both low odor thresholds and generally offensive
odor notes.
In a final generalization, let me distinguish between those in-
dustrial odor problems associated with the emissions from a plant stack
or vent pipe, and those related to "fugitive" sources. There are many
present instances in which the gases or vapors discharged from such a
vent are odorous, and in which there is a valid rationale for, and
reasonable prospects for successful application of, a nuisance prevention
strategy based upon dispersion and dilution. The frequent failures ex-
perienced by those attempting to employ this technique are often due
to one or both of two factors: a lack of appreciation for the uncer-
tainties in extrapolation of dispersion parameters from the 10 to 20
minute periods on which most dispersion equations are based, to the
few seconds adequate to stimulate the odor senses, and to inadequate
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consideration of the influence of aerodynamically induced eddies in the
lee of man-made structures, which are conventionally ignored in such
equations.
Of more frequent occurrence, and often constituting a far more
difficult control problem, are the multiple low level sources scattered
throughout a plant, such as leakages around pump shafts and valve stems,
vapor losses from storage tanks, displaced head space gases when kettles
or shipping containers are filled, and minor spillages occurring during
transfer operations. Many of these sources can be considered to be
housekeeping problems, but particularly when the odor thresholds are
low, consistent control of these sources may be extremely difficult.
This is especially the case when the odorants concerned have relatively
low vapor pressures, are strongly adsorbed on and slowly released from
porous surfaces, and have a pervasive odor note.
The multifarious nature of the odor sources, and the absence of
a coherent unifying principle by which they may be rationally inter-
related, makes both the technical and political attacks on the problem
particularly difficult. Hopefully, as an outgrowth of conferences
such as this, odors, their description, quantitation and control can
be reduced to a science, from its current status to more or less of
an art. But our society is not willing to wait meekly until that day
arrives, and we may expect ever increasing pressures to eliminate or
control odor problems, regardless of complexity or difficulty, on
empirical and ad hoc bases. Our current studies must not ignore our
responsibilities to contribute to the effectiveness of this pragmatic
approach.
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Properties of Odorants
by
Amos Turk
Odor sources may be classified according to their degree of confinement,
their character or quality, their hedonic impact, and their persistence
or pervasiveness in the atmosphere. All of these factors characterize
the odor "dose: in ways that significantly affect the human response at
various distances from the source.
Degree of confinement. A "confined source" is usually considered to be
one which can be characterized as to location and volumetric rate of dis-
charge. Examples are continuous effluents from stacks and vents, and
discontinuous discharges such as those from rupture disks, pressure
relief valves, or displacements of vapor during transfer and filling
operations. Confined sources lend themselves to sampling and analysis.
If the analytical information deals with sensory odor evaluation, or
with chemical measurement of odorants, the results can be used as a
basis for establishing relationships between source and ambient air, which
is to say between dose and response. If the analysis also quantifies
the oxidizable, soluble, or adsorbable components of the effluent, the
results can be used to predict how effectively the odor can be controlled
by methods such as oxidation, scrubbing, or adsorption, which is to pre-
dict a relationship between altered dose and altered response.
Examples of unconfined sources, for which quantitative measurements and
hence rational dose/response predictions are more difficult, are drainage
ditches, settling lagoons, outdoor chemical storage areas, garbage dumps,
and ground that has long been impregnated with odorous matter such as
asphalt. It has been suggested that such sources may be represented by
an imaginary emission point such that, if all the odor from the unconfined
area were being discharged from the "emission point," the dispersion pattern
would just include the unconfined source.
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Odor quality or character
The characterization of odor sources by quality has proved to be a very
difficult task, one that is far from having been resolved. The approaches
have been (a) to describe all odors in terms of a limited number of
"primary" odors; (b) to describe all odors in terms of their degree of
similarity to one another; (c) to describe a particular subset of odors
in terms of an arbitrary selection of descriptive qualities which are
related to the actual composition or sources of the odors; (d) to classify
odors by the frequency of complaints lodged against them.
The "primary" odor approach is represented by systems such as those pro-
posed earlier by Crocker and Henderson, and more recently by Amoore.
These systems have been reviewed by Harper (1). None of them has been
shown to be successful in predicting dose-response relationships in air
pollution situations.
The classification of odors by similarities sets all odors in a conceptual
"space" such that the nearness of any two odors in the space represents
the degree of similarity between their qualities (1). Thus, the character
of an odor is described not in absolute terms, but by identifying the
odors near it in "odor space." Some three-dimensional models have been
constructed to illustrate this idea. It has been found that the single
most significant attribute which determines the character of an odor by
this conceptual system is its hedonic impact.
The applications of a classification system to a particular subset of
odors is exemplified by the diesel exhaust odor standards (2) to be
described later by Karl Springer. This approach has also been used in
the context of community odor problems in area containing a limited
number of odor sources (3).
Odor complaint frequency data have been collected occasionally (4), but
no study has yet been sufficiently extensive to predict whether such in-
formation could provide a meaningful inventory of source types.
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Hedonic impact
Odor preferences have been studied sporadically, usually with reference
to a specific and limited group of odorants and a limited population.
The subject has been recently reviewed by Moncrieff (5), who has also
added considerable data of his own. He also presents a summary embodied
in 124 "rules" of odor preference, but most of these are either so well
known as to be considered obvious, or over-generalized to the point of
being speculative, or lacking predictive value to the point of being
meaningless. The general problem of hedonic scaling, including organiza-
tion and treatment of data and measurement of hedonic impact, has been
considered by Johnston and Rubacky (6). Certainly the most significant
single study of hedonic rating of environmental odors is that conducted
on diesel exhaust by Springer, to be discussed later in this conference.
Odor persistence or pervasiveness
The question of odor persistence or pervasiveness is critical to the
establishment of dose1/response relationships after the dilution of odorant
that normally occurs between source and subject. The general question
of establishment of concentrations will be taken up in the two following
papers by Dr. Sullivan and Dr. Hb'gstrom. Let us assume that odor
intensity, I, is related to odorant concentration, C, by the Stevens
equation
where B is a constant.
We now consider two different odorants of concentrations C, and C~, and
odor intensities 1^ and 12, respectively, and for each odorant, a target
intensity Ii and 12,.» which must be reached by reducing their concentration
to GI and C2t, respectively. (The target concentrations may be but are
not necessarily some functionally described threshold values.)
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Then,
Using the notation described in the Stockholm 1970 report, Z = C/Ct,
and pZ = -log Z, we have,
and
log
"It
log
V
•62(pZ)2
What these equations tell us is that, for equal reductions of the response
to two odors,
/I- N
/
the required reduction in concentrations, Z1 and Z_ are the same only if
the Stevens exponents, BI and Ł„, are the same. The earlier work of
Stevens had implied that the g exponents are characteristic of a particular
odorant, although there may be considerable variation among different
odorants. Values ranging as low as 0.13 and as high as 0.6 have been
reported C7). More recent results have shown that there are also
variations in the 3 exponent among different observers. Some of these
problems may be treated in a subsequent discussion by Dr. Engen. Certainly
this aspect of properties of odorants deserves more study if meaningful
dose/response relationships are to be established.
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REFERENCES
1. R. Harper, E. C. Bate Smith, and D. G. Land "Odour Description and
Odour Classification," American Elsevier Publishing Company, Inc.,
New York, 1968.
2. Turk, A., Wittes, J., Reckner, L. R. and Squires, R. E. "Sensory
Evaluation of Diesel Exhaust Odors," National Air Pollution Control
Administration Publication No. AP-60.
3. Turk, A., and Mehlman, Stanley "Correlations Between Instrumental
and Sensory Characterizations Odors," ASTM STP 440, American
Society for Testing and Materials, 1968, pp. 27-35.
4. W. F. Kerka and E. R. Kaiser, J. Air Pollution Control Assn. _7,
297 (1958)
5. R. W. Moncrieff, "Odour Preferences" John Wiley, New York, 1966
6. J. W. Johnston, Jr., and E. P. Rubacky, "Hedonic Appraisals of
Environmental Odors," Chapter in Human Responses to Environmental
Odors, in preparation.
7. Psychophysical Functions for Twenty-Eight Odorants by Berglund,
Engen, Berglund and Ekman, Psychological Laboratories, Univ. of
Stockholm, April 1970
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Predicting odor frequencies by dispersion calculations
by
Ulf Hb'gstrb'm
Department of Meteorology
The University of Uppsala, Sweden
The problem of making odor dispersion calculations is basically the same
as making calculations of the dispersion of any air pollutant. The basic
requirement is that odor is quantified in terms of concentrations in the
ambient air and in terms of corresponding emission rates and that the
odorous gases do not undergo significant chemical reactions or physical
separations during the atmospheric transport from the source to the re-
ceiver (or if such processes occur they can be specified quantitatively).
There is however one particular point in the process of making odor
dispersion calculations which is critical. When making 'ordinary' dis-
persion calculations the j^amp^iiig^^me can be chosen within fairly wide
limits, the result still being meaningful. But when making odor dis-
persion calculations one must take into account the fact that the nose
reacts fairly fast, so that a sampling time of the order of magnitude of
seconds is relevant. The failure of all earlier attempts (see e.g.
Wohlers 1963) to predict odor frequencies with the aid of dispersion
calculations is primarily due to lack of stringency on this crucial point
(apart from possible deficiency in the description of the emission). The
importance of choosing a. correct sampling time for the calculations is
illustrated in Fig. 1. The irregular curve represents the concentration
of the odorous gas as recorded by some instrument sited in the lee of the
emitting source. The absolute odor threshold is indicated in the figure
and so is the one hour mean concentration value. As seen from the figure,
the concentration exceeds the odor threshold several times during the
hour in spite of the fact that the hourly mean concentration is below the
threshold.
When evaluating dispersion calculations against field observations of
odor great caution must be taken, so that the field observations are ex-
pressed in the same terms as the results of the calculations. It is
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probably almost impossible for an observer to tell with any accuracy for
how long during an observing period of any duration he actually felt
odor. Entirely wrong results are of course obtained if the observer is
asked to tell whether he felt odor or not during any particular hour. The
incident illustrated in Fig. 1 would certainly give the answer "Yes, I
felt odor" - but the threshold was exceeded only during a minor part of
the hour. Thus one would expect that the calculations which give pro-
portion of "odor time" to total time seriously underestimate "the odor
frequency" when compared to that kind of field observations. A fair
comparison can best be done when the observations are performed as in-
stantaneous samples at previously fixed points of time.
In the above discussion a single odor threshold was assumed. As will be
seen below it is quite feasible today to make dispersion calculations that
give frequencies of 'odor threshold exceedings1 in exactly that sense.
It may be that this measure is not very relevant as a description of
odorous impact on a population. There are however also possibilities to
make odor prediction in much more sophisticated terms. But before we
discuss this we will give the outlines of 'the absolute odor threshold
dispersion model' (see Hogstrom 1971 for a more detailed discussion),
which is basic also to more advanced treatments.
Method_for_the_d±S2ers±pn _Ła_lcjulations_,_ When the sampling time is of order
of jme hour_ the plume geometry can be considered rather simple: the
plume rises first, as consequence of buoyancy, but levels off after some
distance, thus obtaining an almost horizontal mean axis (Fig. 2a). The
distribution of the concentration of pollutants in the plume is nearly
Gaussian, measured at a fixed distance from the source in any direction
perpendicular to the axis. The standard deviation, both in the vertical
and in the horizontal cross wind (lateral) direction is a function of
stability and of wind speed. It also depends on the height of the plume
centerline above the ground and of the roughness of the ground beneath.
The behaviour of the standard deviations of the concentration field for
a sampling time of about one hour is fairly well known quantitatively
(for a comprehensive survey see Meteorology and Atomic Energy 1968). In
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order to be able to determine the ground level concentration field the
plume rise, A h (Fig.2a) must be known. This quantity is a function of
the rate of heat emission and velocity from the chimney but also of
meteorological variables: wind speed and stability. Intense research,
both theoretical and experimental, has improved our knowledge of the plume
rise considerably during the last few years '(see e.g. Briggs 1969).
In the case of a .veŁy_sho_rt_ sampling time the plume geometry is much more
irregular than in the case of one hour sampling time. The most charac-
teristic feature is that the mean axis of the plume has an irregular ap-
pearance (Fig. 2b). Furthermore, this form varies all the time in an
entirely random way. This variation, together with the corresponding
variation in the horizontal plane, is the cause of the short term varia-
tion in concentration displayed schematically in Fig. 1. In order to
determine the frequency of odor in a given point the above-mentioned
short term variation in plume geometry must be described in mathematical
terms. This is possible because we know that the distribution of matter
relative to the fluctuating axis as well as the distribution of the locus
of this axis in a coordinate system which is fixed relative to the
ground, is approximately Gaussian (Hb'gstrom 1964).
In a given meteorological situation the standard deviation of the distri-
bution of concentration relative to the moving axis are empirically known
functions of the distance from the source. We then have the necessary
information to describe mathematically the ground level concentration
pattern at a given instant, that is when the plume centerline is situated
at a certain height above the ground. But the standard deviation of the
locus of the plume centerline is also normally distributed with a stan-
dard deviation that varies in a known way with distance from the source.
It is then possible to establish a concentration frequency distribution
for that particular meteorological situation. But the standard deviations
mentioned above vary with meteorological factors (HSgstrb'm 1964, Meteoro-
logy and Atomic Energy 1968) in a way that is fairly well known. Con-
centration frequencies can then be calculated for each of a number of
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representative meteorological situations. The total odor frequency is
then obtained when the frequencies of these meteorological situations
at the site are taken into consideration.
The method outlined above has been tested in a field study (Lindvall
1970 and Hogstrom 1971). Sensory source intensity analyses combined with
meteorological dispersion calculations were used to predict the frequency
with which odors will be discernible in the ambient air at various dis-
tances from a pulp mill.
Predicted odor frequencies in the area were compared with actual observa-
tions of odor during the same period. Controlled observations by specially
trained subjects demonstrated a striking degree of correlation with pre-
dictions for the area of observation thus confirming the validity of the
sensory analytical method and the dispersion calculations under practical
conditions. For distances up to 5 km from the factory there were hardly
any significant differences between calculated and observed odor fre-
quencies. As the distance from the source increased odors were ob-
served more frequently than predictions would indicate, the factor between
observed and calculated frequency rising to somewhat above 2 at 20 km.
The reason for this is not clear. Several explanations are possible.
The odorous gases may undergo chemical reactions or physical separations
that changes the odor threshold. Psychological effects may be important.
Or there are weaknesses in the dispersion calculations. The latter seems
at first to be very reasonable. A relevant analysis, however, shows
that the calculations are surprisingly insensitive to the choice of prop-
er values for the dispersion parameters, that is the standard devia-
tions of the locus of the plume centerline. A possible explanation could
be that the dispersion model is physically oversimplified. If one assumes
that the mean instantaneous shape of rising plume elements differs signi-
ficantly from that of sinking ones, then the calculated frequencies can
easily be brought in accordance with the observed ones. Such a model
is physically reasonable, but there are no experimental data to verify
it.
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The above method gives the average frequency of concentrations above an
absolute odor threshold. But it can be modified easily to give more
sophisticated measures of odor, if such are desired in order to have a
more valid description of the dose. The proper shaping of such measure
is a task for the gathered experts of this meeting. Here follows just
a few examples to illustrate how the above diffusion model can be modi-
fied.
It is quite possible, for instance, to make calculations in terms of
frequency of "odorous hours", with "an odorous hour" being specified as
an hour with the odor threshold being exceeded during more than a speci-
fied proportion of that hour. — It is also possible to give a full
cumulative frequency distribution of (short time) concentrations, which
can be helpful if it is desirable to describe the dose not only in terms
of one threshold concentration.
The model discussed so far is ideal in the sense that it considers the
emission from one single chimney only. If there are several chimneys in
an area emitting _the_ j>ame_ odorous gases (although in widely varying
amounts) the model can be easily modified to handle this, because the con-
centration contributions from the different sources can then be added to
give the resultant concentration, which is considered odorous if it ex-
ceeds a certain limit exactly as before. But if the chimneys emit
di.f_feren_t kinds of gases, the case is far more complicated. It can of
course be treated in terms of absolute odor threshold exceedings, if
sensory analysis has given odor thresholds for all possible concentration
combinations of the different gases. In the case of a limited number of
chimneys emitting a limited number of odorous gases, a practically useful
result can no doubt be obtained from a sensory analysis which contains
only fairly limited number of combinations of concentrations of the
various gases.
The above treatment is ideal also in terms of topographic influences.
The ground has been considered flat, although the influence of roughness
on the dispersion is treated quantitatively in the model. In the case
19
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of hilly countryside the model is subject to the same weakness as any
dispersion calculations, and the success of the calculations depends to
a large extent on the ability to assess the local pattern of wind flow.
Experienced meteorologists can often make a qualified guess about
such patterns. To measure the flow is often difficult, because it may
be so complicated that a large number of measuring stations are required.
It is possible that a dynamical flow pattern model is a practicable
solution in some cases. It means that the dynamical equations are solved
numerically for a proper set of boundary conditions. Such a model is
in the process of being developed for the Oslo area in Norway (not in
particular for odorous dispersion but for air pollution in general).
References
Briggs, G.A., Plume rise, U.S. Atomic Energy Commission, Div. Techn.
Inform., Washington, 1969.
Hb'gstrb'm, U., An experimental study on atmospheric diffusion, Tellus,
1964, 16,205.
Hb'gstrb'm, U., A statistical approach to the air pollution problem of
chimney emission, Atmos. Environm. 1968, 2, 251.
Hb'gstrb'm, U., A method for predicting odour frequencies in the surroundings
of a point source. Manuscript submitted to Atmos. Environment,
1971.
Lindvall, T., On sensory evaluation of odorous air pollutant intensities.
Nord. Hyg. Tidskr. 970, supp.2.
Meteorology and Atomic Energy 1968, U.S. Atomic Energy Commission, Div.
Techn. Inform., Washington, 1968.
Wohlers, H., Odor intensity and odor travel from industrial sources.
Int. J. Air. Wat. Poll. 1963, 7, 7.1.
Legends
Figure 1. Schematic drawing of the variation in concentration of the
odorous gas emitted by an isolated stack as recorded by some ideal instru-
ment sited in the lee of the source. The absolute odor threshold and the
one hour mean concentration value are indicated.
20
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Figure 2. Schematic drawing of plume geometry, the concentration distri-
bution measured at two different sampling times. In 2a the sampling time
is of the order of one hour, in 2b very short (seconds or minutes) ho is
the stack height, Ah is the virtual increase in height due to the effluent's
heat content, motive energy etc.
21
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Concentration
odor
threshold
hourly
mean
1hour
22
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Fig, a
Fla.lb
0
23
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Neurological Responses to Odorants
H. Altner
Fachbereich Biologie, Universitat Regensburg
1 The input to the central nervous system
It is rather difficult to give a survey of the neurological responses
to odorants which can claim to be approximately complete and valid for
more than only the few species of animals normally used in laboratories.
This is partly due to the fact, that it is rather difficult to overlook
the input to the central nervous system (CNS) coming from the olfactory
receptors.
Beginning with sensory input only few investigators have succeeded in
recording responses from single olfactory sensory cells in vertebrates
(GESTELAND et al., 1963, 1965; SHIBUYA and SHIBUYA, 1963; TAKAGI and
OMURA, 1963; ALTNER and BOECKH, 1967). Most of our knowledge about the
physiological properties of receptors in the nasal mucosa of vertebrates
is based on summation potentials (EOGs), the interpretation of which is
difficult and gives only limited information.
From single cell recordings, though still to some extent contradictory,
we can conclude that each receptor cell has its own individual, but con-
sistent spectrum of stimuli to which it responds. No cells appear to have
identical spectra though in the common European frog a basic spectrum
common to most cells has been observed which is supplemented with an
additional spectrum varying from cell to cell. All efforts to describe
different receptor types by the aid of morphological methods have failed
altogether.
Further, the latest fine structural (GRAZIADEI, pers. comm.; KOLNBERGER,
in prep.) as well as electrophysiological results (GESTELAND, pers.
comm.) seem to indicate that the information converging from the receptor
cells to the second order nerve cells does not follow isolated paths.
In electron micrographs thin branches of dendrites have been detected
by which a contact between neighbouring sensory cells could be establish-
ed. Thus the possibility cannot be ruled out that there are lateral
25
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interactions at the receptor cell level, this means that one receptor
cell influences another directly.
The next station in the olfactory pathway is the olfactory bulb where
the sensory cell processes are linked synaptically to the dendrites of
the mitral cells within the glomeruli. Within these glomeruli which lie
near the surface of the olfactory bulb there is a considerable central
convergence of the order of 1000:1 from the afferent fibers to the second
order cells.
Since it seems from single sensory cell recordings that there is no
possibility to distinguish several distinct classes of receptors as
mentioned before, one is incertain whether there exists a special order
in the relationship between receptors and the mitral cells as second
order neurons.
2 Pathways in the olfactory centers of mammals
Before I try to explain the results of physiological investigations I
shall have to give a survey of the pathways as revealed by experimental
morphological studies (LOHMAN and LAMMERS, 1963, 1967; POWELL et al.,
1963a, b, 1965; HEIMER, 1968; PRICE, 1968, 1969).
There are two points of interest: 1. the fiber connections and major
pathways and 2. the inner structure of the olfactory bulb.
a Fiber connections
The olfactory bulb elements which are linked to the sensory cells are
mitral and tufted cells. The axons of these cells form the lateral ol-
factory tract (LOT). This fiber bundle courses over the surface of the
olfactory peduncle and the prepiriform cortex and can be traced as far
as to the periamygdaloid cortex. These forebrain structures are large
in lower mammal groups. . In primates and especially in man they loose
importance and remain as a relatively small region recognizable at the
basal surface of the brain. The results described here come mainly
from rodents (guinea pig, rat).
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The main areas of distribution of LOT fibers are the prepiriform cortex,
the periamygdaloid cortex, and the cortico-medial amygdaloid complex.
Fibers of this tract terminate moreover 1. in the anterior Ifactory
nucleus (pars lateralis, regio posterior), 2. in the lateral part of
the olfactory tubercle and 3. in the nucleus in the LOT.
The anterior olfactory nucleus is important because of its connection
with the opposite side of the brain. One can distinguish two components
crossing, both in the anterior commissure. From the foreward (rostral)
section of the nucleus on each side fibers can be traced to outer areas
of the same nucleus on the other side. From the rear section (pars dor-
salis) of the nucleus fibers can be seen to invade the granule cell
layer of the olfactory bulb on the opposite side. There is no direct
connection between the bulbs. The connection involves the pair of neuron
cains just mentioned and at least two synapses. Later we shall have to
touch on the physiological significance of this arrangement.
The connection to the prepiriform cortex, the periamygdaloid cortex and
the cortico-medial amygdaloid complex are of special interest. From the
latter region originates at least a part of the stria terminalis through
which olfactory impulses could influence the activity of the hypothalamus.
The hypothalamus controls important vegetative functions such as the
reproductive cycle.
Another pathway to the hypothalamus is made up of fibers originating in
the olfactory tubercle and running in the median forebrain bundle to
this region of the brain. Additional connections between the olfactory
bulb and the medial forebrain bundle have been traced via the prepiriform
cortex. Investigations of brain structure thus reveal connections to the
hypothalamus which may be claimed as pathways for the influence of odors
on sexual behavior.
(HEIMER (1968) confirmed recently earlier findings of WHITE (1965) that
there is another projection to the ventral entorhinal area which is
connected to the hippocampal formation.)
27
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b The inner structure of the olfactory bulb
An analysis of the inner structure of the olfactory bulb is a prerequisite
for electrophysiological investigation and a control as well.
The olfactory bulb is laminated. We mentioned already the layer of the
olfactory fibers, the glomerular layer, and the mitral cell layer. A more
complete survey shows that there are additional cell types and layers.
Of special interest are the periglomerular cells of the glomerular layer
and the granular cells of the gramule layer. Both neuron types form
reciprocal synapses:
1. the periglomerular cells form dendrodendritic synapses on
mitral cell dendrites in the glomerular layer (HINDS, 1970)
2. the granular cells form "axodendritic" synapses on mitral
cell dendrites in the external plexiform layer (RALL et al.,
1966, PRICE, 1968).
Degeneration experiments have proven that fibers in contact to the latter
cell type can be affected by LOT lesions (PRICE, 1968). This means that
the LOT is not only a pathway from the olfactory bulb to structures lo-
cated more centrally, but that it also contains centrifugal fibers that
are in the opposite direction - outward. These are linked to the granule
cells by which a centrifugal influence can be mediated.
The origin of the centrifugal bulbopetal fibers is not quite clear.
PRICE (1969) claims that the main origin is the nucleus of the horizontal
limb of the diagonal band which could be influenced by fibers from the
hypothalamus or the midbrain.
The inner structure of the olfactory bulb has been outlined roughly.
Summing up we recognize 3 main features:
1. a considerable central convergence
2. a pathway to the hypothalamus, by which an influence on the vegetative
centers of this region could be exerted
3. an intrinsic neurological organization of the olfactory bulb which
could yield complicated feedback mechanisms as well as a central
control of the input coming from the periphery.
28
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3 Electrophysiological investigation of the olfactory bulb and related
forebrain structures
Electrophysiological evidence supports the concepts developed based on
structural analysis. However, a coherent survey of the function of the
olfactory bulb and the connected stations of the brain is not yet
possible.
Several authors succeeded in recording single unit responses from the
mitral cell layer. MATHEWS (cit. after PFAFFMAN, 1969) showed that such
units in rats can be grouped into three classes according to their
reaction to stimulation of the olfactory mucosa with odorants:
1. purely facilitory units, 2. purely inhibitory units, and 3. units
which respond with facilitation to some odorants and with inhibition
to others.
Similar results have been obtained by DOVING (1966) in bulbar units of the
frog and by LEVETEAU and MACLEOD (1969) in the rabbit.
However, all efforts have failed until now to arrange the units according
to their responses in a systematic way. Only very few units manifested
exactly the same reaction pattern. On the other hand the responses to one
odorant differ: some units may be inhibited, others facilitated, and still
others do not react at all. It was possible however, to ascertain that
successive members in the homologous series of alcohols, ketones and
acetates have more similar olfactory stimulative properties than those
widely separated in chain length (DOVING, 1966, in the frog). Other
authors find a correlation between the reactions, of bulbar units in the
frog and odor perception in man, both for the same classes of substances,
e.g. camphoreceous (HIGASHINO et al., 1969).
Likewise the analysis of the spatio-temporal distribution of excitation
of bulbar elements has yet to deliver a clear cut organizational scheme.
Electrophysiological investigations have revealed that inhibition plays
an important role at the mitral cell level. It appears that at least a
great part of the inhibitory events observed in bulbar units is due to
the activity mediated by centrifugal fibers. Particularly interesting
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is the question of how self-inhibition takes place. Several studies have
shown that antidromic stimulation of the ipsilateral LOT causes a hyper-
polarization at the level of the mitral cells. This inhibitory effect is
mediated by granular or periglomerular cells. It seems due to a dendro-
dendritic mechanism rather than an influence by impulse transmission
from axonal processes (RAIL et al., 1966; NICOLL, 1969). This finding
harmonizes well with the structural features of the system as mentioned
before.
The significance of the inhibitory events may be seen to consist
1. in a contrast amplification
2. in a regulation of both magnitude and selectivity of the olfactory
input to the deeper lying centers through efferent control.
I have mentioned that the interbulbar pathway is considered to comprise
at least two synapses. This is confirmed by the time effects which are
observed in birhinal stimulation (LEVETEAU and MACLEOD, 1969). A minimum
appears in the magnitude of the homolateral response when the hetero-
lateral stimulation is given about 3 msec before the homolateral one.
This finding gains particular importance as an olfactory analogue to
directional hearing in man based on a reciprocal inhibition mechanism
has been discovered by von BEKESY (1964).
It was pointed out that fiber connections to the hypothalamus have been
demonstrated in rodents. In 1967 SCOTT and PFAFFMAN were able to support
these results by electrophysiological experiments. These authors found
multiunit as well as single unit discharges in the region of the medial
forebrain bundle within the lateral hypothalamus after stimulation of
the olfactory receptors by application of odorants or after electrical
stimulation of the LOT.
These findings are supplemented to some extent by other experiments in
which electrolytic lesions were made in the medial preoptic-anterior
hypothalamic continuum and surrounding regions (HEIMER and LARSSON,
1966/67) in the rat. Large lesions in this area eliminate mating, as
one might expect since the medial preoptic-anterior hypothalamic conti-
nuum occupies a strategic position in the limbic system. It becomes
interesting to recall that part of the input to this region in macrosomatic
30
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animals is delivered by the medial forebrain bundle and the stria
terminalis, and that these structures are connected to the olfactory
bulb.
Moreover recordings from the medial forebrain bundle and the preoptic
area in general show single units responding to electrical stimulation
of the olfactory bulb and to stimulation of the nasal epithelium by
odorous substances as well (PFAFF and PFAFFMAN, 1969). A point of special
interest is the fact that the responses of these elements in the male
rat are influenced by testosterone application.
Direct application by microinjection causes an increase in the resting
activity and an increase response to olfactory input. Intraperitoneal
injections of testosterone were followed by more diverse changes. Thus
the direct physiological action of testosterone in the basal forebrain
may have the specific effect of enhancing olfactory input to the brain
regions connected to these structures.
This result is of particular significance as this region shows a high
level and prolonged uptake of radioactive testosterone from the blood
(PFAFF, 1968). Thus in this part of the olfactory pathway nervous and
endocrine regulation seem to be linked together in the control of
sexual behavior. It is particularly noteworthy, that responses in this
region differentiate between odors from receptive and non-receptive
female rats more clearly than in the olfactory bulb (PFAFF and PFAFFMAN,
1969).
It may be remarked here that the role of odors in the sexual behavior
of rodents hab been demonstrated by several behavioral investigations
(PARKES and BRUCE, 1961; VANDENBERGH, 1969; WRITTEN, 1969) and it has
been proved that sexual excitation and activity in primates is influenced
by a hormone-dependent pheromone secretion which in certain cases
acts through olfactory stimulation (MICHAEL and KEVERNE, 1968).
We have only very little information about the neurological responses
to odorants in the higher primates including man. Though we should
expect a reduced importance in the species belonging to this group
according to the morphological reduction of the (olfactory brain, one
31
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has to realize that a good many of the mechanisms which seem to be
rather powerful in lower mammals could be still present though perhaps
overlaid by additional regulatory mechanisms which arose during
evolution.
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REFERENCES
Altner, H. and J. Beockh: Z. vergl. Physiol. 55, 299 (1967)
Bekesy, G. von: J. Appl. Physiol. j.9_, 369 (1964)
DSving, K. B.: J. Physiol. 186, 97 (1966)
Gesteland, R. C., J. Y. Lettvin, W. H. Pitts and A. Rojas: in : Olfaction
and Taste I, (Y. Zotterman ed.) Oxford, Pergamon Press (1963)
Gesteland, R. C., J. Y. Lettvin and W. H. Pitts: J. Physiol. (Lond.)
181, 525 (1965)
Heimer, L.: J. Anat. (Lond.) 103. 413 (1968)
Heimer. L. and K. Larsson: Brain Res. 3j_ 248 (1966/1967)
Higashino, S. H. Takeuchi and J. E. Amoore: in : Olfaction and Taste III,
(C. Pfaffman ed.) 192, New York: Rockefeller Univ. Press (1969)
Hinds, J. W.: Brain Res. _17_, 530 (1970)
Leveteau, J. and Macleod: in : Olfaction and Taste III (C. Pfaffman ed.)
212, New York: Rockefeller Univ. Press (1969).
Lohman, A. H. M and H. J. Lammers: Progress in Brain Res. ^, 149 (1963)
Lohman, A. H. M and H. J. Lammers: Progress in Brain Res. 23, 65 (1967)
Michael, R. P. and E. B. Keverne: Nature (Lond.) 218, 746 (1968)
Nicoll, R. A.: Brain Res. 14, 157 (1969)
Parkes, A. S. and H. M. Bruce: Science 134, 1049 (1961)
Pfaff, D. W.: Science L61, 1355 (1968)
Pfaff, D. W. and C. Pfaffman: in : Olfaction and Taste III (C. Pfaffman
ed.) 258, New York: Rockefeller Univ. Press (1969)
Pfaff, D. W. and C. Pfaffman: Brain Res. 15, 137 (1969)
Pfaffman, C.: in: Olfaction and Taste III (C. Pfaffman ed.) 226,
New York: Rockefeller Univ. Press (1969)
Powell. T. P. S. and W. M. Cowan: Nature (Lond.) 199. 1296 (1963a)
Powell, T. P. S., W. M. Cowan and G. Raisman: Nature (Lond.) 199,
710 (1063b.)
Powell, T. P. S., W. M. Cowan and G. Raisman, J. Anat. (Lond.) 99,
791 (1965)
Price. J. L.: Brain Res. _7, 483 (1968)
Price, J. L.: Brain Res. 11, 697 (1968)
Price, J. L.: Brain Res. 14_, 542 (1969)
Rail, W., G. M. Shepherd, T. R. Reese and M. W. Brightman: Exp. Neurol.
JL4, 44 (1966)
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REFERENCES (Cont'd)
Scott, J. W. and C. Pfaffman: Science 158. 1592 (1967)
Shibuya, T. and S. Shibuya: Science 140. 495 (1963)
Takagi, S. F. and K. Omura: Proc. Jap. Acad. J39, 253 (1963)
Vandenbergh, J. G.: Endocrinology J54, 658 (1969)
White, L. E. Jr.: Anat. Rec. 152. 465 (1965)
Whitten, W. K.: in: Olfaction and Taste III (C. Pfaffman ed.) 252,
New York: Rockefeller Univ. Press (1969)
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Sensory evaluation of odors in the
ambient air
by
Thomas Lindvall, M.D.
Dep. Environmental Hygiene
Karolinska Institute
S-104 01 Stockholm, Sweden
Paper presented at the Working Conference on the
Dose-Response Relationships Affecting Human Reactions
to Odorous Compounds, Cambridge, Mass. USA, April 26-30, 1971
35
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Sensory evaluation of odors in the
ambient air
by
Thomas Lindvall, M.D.
Dep. Environmental Hygiene
Karolinska Institute
S-104 01 Stockholm, Sweden
Introduction
The procedure in studying environmental odor nuisances is commonly
based on an effort to find the relationship between the dose to which
the public is exposed and the annoyance reaction displayed. By help
of such studies a prognosis can be made of reactions to be expected
in a community at different dosage levels. Studies of this type require
adequate designation of dosage and response as well as knowledge of
the conditions under which the particular dose-response relationship
is valid.
The quantitative determination of malodorous air pollutants in ambient
air is complicated by the fact that their smell becomes offensive at
concentrations which are often too weak for the practical analysis of
short term measurements. For the time being it would seem that ultimately
methods of sensory analysis are the only practical way of measuring
odors in combined exhaust gases while also having relevance in regard
to environmental health. In principle this means that the human olfac-
tory sense must be used as detector and analyser.
Sensory methodology can be used as a tool in description of dosage
as well as of response. Up to now most evaluations in ambient air by
these methods have aimed at measuring dosage by using indirect prog-
nosis techniques (source analysis) or direct methods of analysis.
The response to an odorant, mainly a subjective feeling of annoyance
may be measured on groups of sociological inquiry methods and, in part,
on individuals by sensory methods of analysis.
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Sensory methodology for ambient air analysis or estimation must satis-
fy the following requirements:
a) be serviceable in practical and economic respects
b) include a standardized experimental procedure which guarantees
acceptable reproducibility, and
c) give valid experimental results from the standpoint of hygiene.
Equipment
To meet the above mentioned requirements an essential part of the efforts
should be directed towards construction of mobile odor laboratories
for field studies under controlled and standardized conditions. Such
laboratories have been successfully used in Sweden since two years
ago for analysis at the source as well as in the ambient air (Lindvall
1970). Sullivan, Adams and Young (1968) and Springer and Hare (1970)
in the USA have used mobile laboratories, however with different goals
i.e. to survey detection or objection to standardized odor levels
produced within the laboratory.
The olfactometers should permit known and stable exposure concentra-
tions, rapid changes in concentration and fairly natural respiratory
conditions. To many scientists the most reasonable exposure alterna-
tive is provided by the odor hood (recent examples are Merrion 1968;
Sullivan, Adams and Young 1968; and Lindavll 1970). Perferably the
exposure hoods should be installed in a ventilated and airconditioned
test chamber. Another object in the construction of the Swedish
laboratories has been to arrange for special waiting rooms for the test
subjects with ventilation comparable to the actual test procedure in
order to provide optimal adaptation to the experimental situation. By
using suitable filter equipment it is thus possible to carry out in-
vestigations in the immediate vicinity of a single emission source or
in a generally odor polluted area with a minimum of contaminations in
the laboratory air.
38
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Construction of mobile laboratories has made it possible to limit varia-
tions in climatological background, and the use of dynamic dosing systems
has minimized losses due to adsorption and other factors. Field experi-
ments with the Swedish equipment are therefore assumed to provide stan-
dardized although special experimental conditions, and the results shall
always be considered in relationship to the technical equipment used.
The experimental situation is not assumed to be necessarily comparable
to normal conditions of exposure in the ambient air. Extensive studies
as to the reliability of the experimental procedure in its entirety in
source analysis and the importance of various interaction factors have
been undertaken (Lindvall 1970).
Sensory methods
A thorough review of sensory methods of analysis and their application
has recently been published (the Third Karolinska Institute Symposium
on Environemtnal Health, 1970).
From the point of view of atmospheric conservation a given odor sensa-
tion may be generally described in four respects or "dimensions". These
are the detectability of the substance, its intensity at suprathreshold
levels, its acceptability or hedonic tone (i.e., the annoyance or,
possibly, pleasure it stimulates) and, finally the characteristic
properties, quality, distinguishing it from other odors irrespective
of intensity of acceptability.
In the environmental health the most important dimension of an odor is
probably its acceptability i.e., what percentage of the population
is annoyed by the smell and to what extent. Public reactions of sub-
jective annoyance can probably best be evaluated by sociological survey
methods. This response can be related to the degree of exposure to
odorous air pollutants to which the population is exposed (the dose).
Acceptability may also be studied in a laboratory scale e.g. by apply-
ing direct methods of scaling as suggested by Engen and McBurney (1964).
Matching of one standard odorant to different combustion gases with
39
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respect to equalunpleasantness has been used by Lindvall and Svensson
(1971). Hydrogen sulfide was matched to five different combustion gases
with regard to unpleasantness by use of an equality production method.
Figure 1 shows the resulting five equalsensation functions in log-log
coordinates. It was concluded that no differences were evident between
combustion gases (as indicated by the slope of the lines) but that hydro-
gen sulfide at the same concentration was perceived twice as unpleasant
as any of the five combustion gases.
Results of such laboratory studies may constitute an important part in
the description of dosage in the ambient air, e.g. when comparing two
odor covered areas with similar odor frequencies but with differences
in the hedonic value of the odorants in question.
The dimension of odor quality may be relevant to include in ambient air
evaluations partly due to its connection with the hedonic value of an
odorant, partly due to the frequent necessity of identifying the source
of the odor. Sensory methods that may be applicable in field studies
of odor quality are multidimensional and informational analysis of odor
quality (Torgerson 1958, Ekman and Engen 1962, Woskow 1968). Such
methods ideally require a high standard technical equipment, for use
in field studies prefereably mobile, and a relative stable odorant
concentration input to the dosing system. The latter requirement is
not always fulfilled in ambient air studies but close to the emitting
stack or in areas heavily polluted from surface sources.
Studies of suprathreshold perceived intensity are of interest in sensory
evaluation in the ambient air since they concern the change in perception
associated with a reduction in the physical odor intensity. Thus, for
example it would not be reasonable to expect the most significant changes
in a critical local air pollution situation involving prolonged odor
problems, when the concentration to which the public is exposed varies
about the most level part of the psychophysical function for the odorous
substance in question. Such considerations may be of significance in
the vicinity of major traffic arteries or other wide spread sources
40
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which are not limited to a single point. However, in a wider context,
especially when the source of the odor is localized to a given point,
any change in the odor intensity of the effluent gases may be expected to
produce alterations in the frequency with which odor is perceived, i.e.
when the absolute odor threshold is exceeded in the area.
In studying intensity of odor one should preferably use modern psycho-
physical scaling methods (e.g. see Torgerson 1958; Ekman, Berglund, Berglund,
Lindvall 1967; Lindvall 1970). There are the same practical requirements
with respect to equipment and input odorant concentration as indicated
above in the discussion of quality.
In many cases detection methods are used to obtain an idea as to the
intensity with which an odorous substance is experienced. Examples of
such methods are absolute odor threshold measurements and methods based
on the theory of signal detectability. Threshold values or detectability
indexes do not give any measure of the perceived intensity above "threshold"
levels but do undeniably provide valuable information regarding source
control and the distribution of odorant emanations in the atmosphere.
The main advantage of the signal detection methodology is that it is
able to measure response biases. This is an important problem in ol-
faction because a sophisticated observer with the best of equipment will
always produce a relatively high proportion of false positives. These
must be measured in order to obtain a valid description of dosage. Dif-
ferent modifications of the basic methodology may be applicable to most
practical situations (Green and Swets 1966; Lindvall 1970; Berglund,
Berglund, Engen and Lindvall 1971).
There are also some serious limitations in detection methodology with
regard to its applicability in practical public health work. These methods
frequently require preliminary experiments since in practice it can only
be used within a rather small region in the vicinity of the detection
"limit" where the probability of hits and false alarms varies between
0 and 100 percent. Another disadvantage is the difficulty of expressing
41
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the results of signal detectability measurements in a single physical
limit value which are presently necessary for applicability in existing
methods of calculating atmospheric odorant dispersion. A sophisticated
use of classical absolute odor threshold determinations then has been
proved to give valid measures in dosage description (Lindvall 1970).
In conclusion the need for and benefit of both the modern detection
theories and the classical concept is evident for the time being in this
type of work.
Sensory evaluation in the ambient air
Data necessary for an adequate description of ambient air levels of odor
can be obtained through the use of human sensors in four different ways.
The first two methods are of a prospective nature. The observation method
is based on consecutive observations of odor occurrence (frequency, dura-
tion, identity, intensity, hedonic value) within a given area for a fixed
period of time. Such observations can be made either with many untrained
observers or with fewer trained individuals, possibly with a simple sensory
measuring aid such as the scentometer (Heller et al. 1959; Gruber et al.
1960; Sanders et al. 1970; First 1970). A sophisticated study design,
e.g. concerning selection of sampling points and the use of a sufficient
number of observations over prolonged periods of time, is necessary if
data of value from the point of view of public health are to be expected.
Data concerning hedonic value and perceived intensity obtained by category
judgements like "weak", "moderate", "intense" etc. by single observers
in the field will only attain an ordinal level of measurement that is
unsatisfactory in most cases. Data obtained by category scaling may,
however, be treated in the manner of Thurstone (cf. Torgerson 1958) on the
basis of certain assumptions about variability thus providing an inter-
val scale. The usefulness of the method is limited by the large number
of observations needed and that the results probably can be used only
for relative comparisons between sectors within the general investigation
area. Category scaling may be easified by a kit of standard references
for use in the field similar to the Turk-kit (1967) on diesel odors.
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As indicated by Berglund, Berglund, Engen and Lindvall (1971) and by
recent pilot studies in Sweden (Lindvall 1971) the method of signal
detectability may be applicable for direct determinations of changes in
the relative dose in ambient air, particularly in the case of more gen-
eralized pollutant sources such as traffic arteries or in other areas
afflicted with prolonged odor exposure where the question of frequency is
irrelevant. However, such studies require experimental equipment of
high standard, preferably mobile. Rapid changes in ambient air concentra-
tion will require a correspondingly larger number of simultaneous observa-
tions.
The Swedish pilot study conducted by the author included determination of
an index of detectability (d') for odor levels in the ambient air in one
of the main streets of Stockholm city during rush-hours. The index was
calculated as group values on six subjects at a time with the sampling
time being half an hour. As a whole 18 subjects participated. One of
the mobile odor laboratories was used, placed close to the drive-way and
the gas inlet 1.5 m above the curbstone. The study was conducted during
three consecutive days and was followed for comparison by a two-day study
of the odor levels in a less polluted area at a university campus in a
suburb to Stockholm.
Although the quantity of data obtained is limited the results are pro-
mising. The false alarms and d1 measured at the campus area are of
similar magnitude as compared between groups and iterations. This in-
dicates reasonably stable and comparable criteria used by the three
groups of subjects. Assuming that the experimental conditions did not
change moving the laboratory from the street to the campus this result
permits a calculation of an index of detectability. In Figure 2 odor
indexes and concentrations of carbon monoxide in the street are plotted
against time of the day. As can be seen from the lower part of the figure
each half an hour period has been tested three times. However, each ob-
servation is based on a fairly large number of signal + noise and noise
presentations (120/120). The arithmetic mean is indicated by the full
43
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line. The doted lines indicate the mean detectability index at the
campus and its standard deviation, all calculations being based on half
an hour data.
Index of detectability varies in an expected fashion compatible with the
traffic load during rush hours. The detectability of odor is relatively
low, presumably because of the generally low pollution load in the streets
of Stockholm and the unusually well ventilated place of observation (close
to a square and a very tall single building). The correlation between
odor index and concentration of carbon monoxide is doubtful (r = 0.31,
n = 54, 0.05 p 0.01). This is not surprising as carbon monoxide in it-
self is nonodorous and not a representative exhaust gas of diesel vehicles.
In spite of the preliminary character of this experiment signal detection
methodology seems to be a realistic alternative in dosage description
in the ambient air when dealing with surface sources.
The third method is based on interviewing the resident population in order
to find out what their retrospective opinions are concerning the average
odor frequency and duration of the smell. Such data have been collected
on several occasions in conjunction with interviews where the reactions
of residents to the occurrence of odor have also been noted (Friberg,
Jonsson and Cederlof 1960; Cederlof et al. 1964).
The estimation of exposure based on retrospective interviews can in itself
reflect the experiences of the subjective exposure but cannot be definitely
relied upon to do this. One difficulty presented by using retrospective
interviews is the exact period of time the questions are related to.
Furthermore, it is not known as to what degree the respondents uncon-
sciously exaggerate or depreciate the frequency of exposure owing to
their negative or positive attitudes or to the actual annoyance they have
experienced (Lindvall 1970).
The fourth method is of a prognosis-type (indirect evaluation of dosage)
and is based on the knowledge of the source strength of the gas and the
expected distribution of the gas mass over the investigation area and
44
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the dilution at ground level at different distances from the point source.
The source strength can be evaluated by sensory methods of analysis and
to a certain extent by chemical analyses. However, the latter requires
that all the relevant substances can be accurately determined and that
the absolute odor threshold for each of these is known. Also the com-
bined odor intensity must not be affected by gaseous interaction which
causes enhancement or suppression of the smell.
The probable distribution and dilution of effluent gases can be studied
by means of various dispersion methods (for a review, see Strom 1968).
Several methods give for selected points in the area surrounding a source
"typical maximum values" which are not connected to given frequency values,
e.g. Button's formula. Another way to attack this problem is to calculate
the expected concentration frequency distribution for selected points
in the vicinity of the source (HSgstrSm 1968, Lindvall 1970). However,
this also requires the dose in the ambient air to be described in a statis-
tically meaningful manner.
In Sweden sensory intensity analyses (absolute odor threshold) combined
with meteorological dispersion calculations of the latter type, have been
used to predict the frequency with which odors will be discernible in
the ambient air at various distances from sulfate cellulose plants. The
calculation method used gives the expected frequency with which the
absolute odor threshold value for the effluent gases will be practically
momentarily exceeded and thereby detected at a given observation point.
The accuracy of such predictions has been checked in a large scale field
experiment that was undertaken in the vicinity of a pulp mill at the East
coast of Sweden. In Figure 3 the factory is shown in the center surrounded
by eight sectors and three distances (2, 5 and 10 km). There was also
a 20 km circle not shown in the figure. Each day, based on a weather
forecast, a sector was chosen in lee of the factory and trained observers
were randomly distributed on the circles within the sector. A large
number of observation places were reconnoitered in before hand on the
circles in all directions. The observers were instructed to register
45
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every two minutes if there was any sulfate odor present at the very
sniff, thus an almost momentary observation. The time was checked by
stopwatches. Parallel to the observations the odor thresholds of stack
discharge were determined and the atmospheric dispersion was calculated
based on meteorological measurements. This study went on for one month
and the results are summarized in Table 1.
The table shows the total number of observations at each distance from
the plant. All sectors are figuratively speaking, put together on the
top of each other. For this resulting mean lee sector of observation
the observed and predicted odor frequencies are given and also the ratio
between observed and predicted frequencies.
There is a striking degree of correlation with predictions, up to 5 km
a factor of 1.2-1.7, thus confirming the validity of the sensory analytical
method and the atmospheric dispersion calculations under practical con-
ditions. As the distance from the source increases, odors are observed
more frequently than predictions would indicate but still up to 20 km only
by a factor of 2.6-3.0. When comparing with earlier studies on atmos-
pheric dispersion these results are surprisingly good.
Of course, a prognosis of the expected odor coverage expressed as a mean
frequency value over a considerable length of time, must not necessarily
reflect the subjective exposure of the population. Some results (Lindvall
1970) indicate that calculations of the predicted frequency of perceived
odor within a large area may need to include a correction to give appreciably
higher values, especially at greater distances from the source. However,
as a base in establishing dose-response relationship in a single source
case, the predicted odor frequency may nevertheless be considered to be
the less subjective, the most adequate and the less expensive measure
in describing the dose, as compared with survey methods and direct
measurements in the ambient air.
Other aspects on the perception of odors in environmental health than
frequency and duration of odor exposure are effects of context like
46
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adaptation and expectation (Ekman, Berglund, Berglund, Lindvall 1967;
Berglurid, Berglund, Engen, Lindvall 1971; Engen 1970). Interaction
principles between different odors or between odors and agents affecting
other sense modalities, like vision and hearing, are mainly unknown
(Berglund, Berglund, Lindvall 1971). Especially acceptability of annoying
agents may be influenced in the real life situation also by compensation
or aggravation mechanisms of socio-economic origin and the like. Such
influences limit the applicability of sensory methods of analysis in
population studies to description of dosage and studies of the existence
and strength of the interaction effects mentioned above.
47
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References
BERGLUND, B., BERGLUND, U. and LINDVALL, T., On the principle of odor
interaction, Rep. Psychol. Lab. Univ. Stholm., in press 1971.
BERGLUND, B., BERGLUND, U., ENGEN, T. and LINDVALL, T., Effect of adap-
tation on odor detection, Perception & Psychophysics, to be published
1971.
CEDERLOF, R., EDFORS, M.-L., FRIBERG, L. and LINDVALL, T., Determination
of odor thresholds for flue gases from a Swedish sulphate cellulose
plant, TAPPI 1965, 48, 405.
EKMAN, G. AND ENGEN, T., Multidimensional ratio scaling and multidimen-
sional similarity in olfactory perception, Rep. Psychol. Lab., Univer.
Stockholm 1962, No. 126.
EKMAN, G., BERGLUND, B., BERGLUND, U. and LINDVALL, T., Perceived in-
tensity of odor as a function of time of adaption, Scand, J. Psychol.
1967, 8, 177-186.
ENGEN, T. and McBURNEY, D.H., Magnitude and category scales of the plea-
santness of odors, J. Exp. Psychol. 1964, 68, 435-440.
ENGEN, T., The effect of expectation on judgements of odor, unpub-
lished manuscript 1970.
FIRŁ>T, M.W., A model odor control ordinance, Paper presented at the 2nd
International Clean Air Congress, Washington D.C. 1970.
FRIBERG, L., JONSSON, E. and CEDERLOF, R., Studier over sanitara olagen-
heter av rokgaser fran en sulfatcellulosafabrik, Nord. Hyg. Tidskr.
1960, 41, 41-50.
48
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GREEN, D.M. and SWETS, J.A., Signal detection theory and psycho-physics,
Wiley New York, 1966.
GRUBER, C., JUTZE, G. and HUEY, N., Odor determination techniques for
air pollution control, J. Air. Poll. Contr. Ass. 1960, 10, 327-330.
HELLER, A.N., KANDINER, H.J., REITER, W.M. and COHEN, M., The odor
survey: A tool for air pollution control, Air and Water Pollution Abate-
ment Conference, Manufact. Chemists Ass., Washington B.C. 1959.
HOGSTROM, U., A statistical approach to the air pollution problem in
chimney emission, Atmos. Environ. 1968, 2, 251-271.
LINDVALL, T., On sensory evaluation of odorous air pollutant intensities,
Nord. Hyg. Tidskr. 1970, suppl. 2, 1-181.
LINDVALL, T. and SVENSSON, L.T., Equal-unpleasantness matching of one
standard odorant to different complex odor mixtures, unpublished
manuscript 1971.
LINDVALL, T., Unpublished data 1971.
MERRION D., Effect of design revisions on two stroke cycle diesel engine
exhaust, Paper 680422, Society of Automotive Engineers, Inc. New York
1968.
SANDERS, G.R., UMBRACO, R.A., TWISS, S. and MUELLER, P.K., The measure-
ment of malodor in a community by dynamic olfactometry, Paper presented
at the Third Karolinska Institute Symposium on Environmental Health,
Stockholm, June 1970, (Unpublished).
SPRINGER, K.J. and HARE, C.T., A field survey to determine public opinion
of diesel engine exhaust odor, Rep. No. AR-718, Southwest Research In-
stitute, San Antonio, 1970.
49
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STROM, G.H., Atmospheric dispersion of stack effluents, in Stern, A.C.
(Ed.), Air Pollution. I, 227-274, Academic Press, New York, 1968.
SULLIVAN D.C., ADAMS, D.F. and YOUNG, F.A., Design of an "odor percep-
tion and objectionability threshold" test facility, Atmos. Environ.
1968, 2, 121.
Third Karolinska Institute Symposium on Environmental Health, Methods
for measuring and evaluating odorous air pollutants at the source and
in the ambient air, Nord. Hyg. Tidskr. 1970, 51, 1-77.
TORGERSON, W.S., Theory and methods of scaling. Wiley, New York 1958.
TURK, A., Selection and training of judges for sensory evaluation of the
intensity and character of diesel exhaust odors, U.S. Dep. Health,
Educat. Welfare, PHS publication No. 999-AP-32, 1967.
WOSKOW, H.M., Multidimensional scaling of odors, in TANYOLAC, N. (Ed.)
Theories of Odors and Odor Measurement. New York, Spartan Books, 1968.
50
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2.5
I — I I I
en
2.0
.O
Q.
a
•E 1.5
ci
c
o
o
"k 1.0
O)
o
0.5
O.o
J I I L
0.5 units
Relative log combustion gas cone.
D J
E J
Figure 1
-------
ppm
6_
5_
4_
3_
2_
1_
Carbon monoxide
30_
Odor index
20
10
o o
07
I
08
I
09
i
10
Time
i
15
i
16
17 18
19
Figure 2
-------
km 1
cn
Figure 3
-------
Prediction of odor incidence
Number of obs.
Observed odor °/o
Predicted odor °/o
Ratio obs. /predict.
2km
6426
10.8
9.1
1.2
5km
7 490
9.8
5.7
1.7
10km
5528
8.5
3.2
2.6
20km
6976
5.1
1.7
3.0
Table 1
-------
METHOD AND THEORY OF ODOR PREFERENCE*
By
Trygg Engen
Walter S. Hunter Laboratory of Psychology
Brown University
Number of tables: 4
Number of figures: 4
Proofs should be sent to:
Dr. Trygg Engen
Walter S. Hunter Laboratory
of Psychology
Brown University
Providence, Rhode Island 02912
51
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METHOD AND THEORY OF ODOR PREFERENCE*
By
Trygg Engen
Brown University
The importance of the psychological acceptability of odors seems
obvious, but judging from the dearth of published research the problem
has in fact been largely ignored by sensory physiologists and
psychologists. Most research on the sense of smell involves either
odorant concentration and the sensitivity of human subjects or the
relationship between physical and chemical attributes and the
perceptual quality of an odorant. The latter relationship is still
too poorly understood to be useful in controlling odors. Since there
is a good deal of information about the psychophysical relationship
between concentration of an odorant and its perceived odor intensity,
most applied work on air quality has been based on this aspect of the
problem (see Third Karolinska Symposium on Environmental Health, 197C).
This has meant an emphasis on work with so-called threshold levels,
that is, concentrations which are just strong enough to be noticed
by the average observer. This is sufficient information for many
57 61
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T. Engen
purposes, for example, establishing criteria for maximum acceptable
concentrations of pollutants, but it provides no information at all
regarding the perceived quality of the air and its acceptability.
Except for substances which mainly stimulate the trigeminal nerve,
there is no known psychophysical relation to utilize in dealing with
hedonic effects of odorants, and in this area one is limited to
psychological methods of measurement. Psychological scaling and
opinion polling have been the two main methods. Opinion polling is,
of course, a well known procedure and it has been used to advantage in
the case of odor. Studies in Sweden have been especially valuable in
proposing means for isolating the effects of the subject's attitude
toward the source of an odorant from its perceptual effects (Cederlb'f,
Friberg, Jonsson, Kaij, and Lindvall, 1964). Like opinion polling,
psychological scaling has reached a mathematically sophisticated level.
An example of this is the methodology developed for multidimensional
scaling that has been applied in olfaction in attempting to determine
the basic psychological dimensions of the odor space (Harper,
Bate-Smith, and Land, 1968).
The present paper will be limited to more simple and direct
methods of scaling and will attempt to emphasize one basic problem of
odor perception and judgments. It is generally assumed that
associations based on individual experiences are the most important
reasons for the large inter-individual variation in judgments observed.
An early study of individual differences in affective responses to
odors by Kniep, Morgan, and Young (1931) concluded thnt there wns good
58
62
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T. Engen
agreement in the results from children (ages 7-9) and adults, although
they had doubts about the intra-individual reliability of the children's
judgments. Recently Moncrieff (1966) has produced evidence which
suggests that age may be the most important variable, even more
important than sex, in the development of preferences. In general,
children tend to be more tolerant of unpleasant odors than adults. Of
particular interest has been a suggested discontinuity in such
responses between the ages of four and five observed by Stein,
Ottenberg, and Roulet (1958) to synthetic odors of feces and sweat.
Three and four-year-old children tended to say they "liked" those
odors while children five years and older said they "disliked" them.
These data are shown in Fig. 1 (Slide 1). The authors thought that
Insert Fig. 1 about here
this discontinuity may be "related to early childhood experiences and
to the mastery of instinctual impulses" (p. 265) and that odor
preferences may be explained by the Oedipal conflict. Reaction
formation in the anal stage may thus cause a change from liking to
disliking the odors of feces and sweat. According to Moncrieff (1966),
"Sometimes there is a natural and well-founded dislike of a smell; one
may be educated out of it by psychoanalysis explaining that it is
caused by some forgotten and unimportant incident, but the real reason
may go much deeper than subject or psychoanalyst guesses." (p. 205).
The suggestion is that there are innate responses to certain odors,
for example, anaphrodisiacs.
To this must be added that sometimes neither psychoanalytic nor
S3
59
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T. Engen
physiological hypotheses are needed because a simple psychological
explanation is possible. In particular, the tendency to appear
agreeable in situations where either "Yes" or "No" is the required
response has often been attributed to young children. This is the
response bias of acquiescence characteristic of the "yes man" (Guilford,
1954). Katz and I (1968) had begun a study on odor preferences similar
to that of Stein et_ al., when this bias was observed after testing just
a few children. The experiment was therefore redesigned to include
variations in the instructions describing the nature of judgment
desired as one of the three independent variables together with the age
of the children and the pleasantness of the odors. The purpose was to
pursue the study of the development of odor preference with the
question in mind: if such age differences exist, are they the result
of actual differences in olfactory preferences or of response bias
which also varies as a function of age?
A total of 134 boys and girls in four groups of about 30 and
ranging in age from four to seven participated in this experiment.
They were assigned randomly to groups receiving different instructions.
Since relatively few four-year-old children were available, only three
sub-groups (or instructions) could be tested for that age.
Three odorants were selected in order to produce odors ranging
from very unpleasant to very pleasant as judged by adult observers
(Engen and McBurney, 1964). These were iso-butyric acid, iso-amyl
acetate and safrol. (Note in Fig. 1 that Stein et_ al., also used
amyl acetate and a compound which they do not identify but describe as
60
64
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T. Engen
"synthetic sweat.") In addition, the present experiment used diethyl
phthalate both as a diluent and as a "blank" stimulus for catch trials,
for it has only a neutral and vague odor. The other three odorants
were matched in intensity to a 25 percent solution of amyl acetate in
diethyl phthalate using 12 graduate students as judges. These three
concentrations plus diethyl phthalate were prepared for each day of
testing and were presented to the subject on cotton wrapped around a
glass rod.
The subject was seated across a table from the experimenter who
explained that the task involved smelling and demonstrated how the
subject should sniff it and "then tell me if it smells ."
The sentence was completed by one or two adjectives, namely, "pretty,"
"ugly," "pretty or ugly," and "ugly or pretty." (The choice of
adjectives was made on the basis of preliminary work suggesting these
adjectives would be semantically unambiguous to young children.) The
odorants were presented in a different irregular order to each subject,
except that diethyl phthalate was always presented fourth, and the first
odorant was presented again at the end to obtain evidence of reliability
of the judgments. There was an interval of at least 30 sec. between
two successive odorants to avoid possible effects of adaptation.
The response was scored either plus (+) for pleasant or minus (-)
for unpleasant regardless of the question asked; for example, if the
question was, "Tell me if it smells pretty," a response of "No" was
scored - (i.e., unpleasant), and a response of "Yes" was scored +
(i.e., pleasant). As an index of reliability of the judgments,
6i 65
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T. Engen
82, 85, 85, and 80 percent of the children of ages four, five, six, and
seven, respectively, gave the same response to the stimulus presented
for the second time at the end. (The response to this repeat was not
included in any of the analyses shown below.) Sex was not a significant
variable, for square analysis resulted in .80< p. <.90 for the
frequency of + response obtained from girls versus boys.
According to the literature cited, it would be expected that
butyric acid would on the average be rated somewhere between natural
(about equal proportions of - and + responses) to pleasant
(preponderance of +) by the four-year-olds but more and more unpleasant
(preponderance of -) as a function of age. Safrol and amyl acetate
should be rated as pleasant, and diethyl phthalate should be rated
neutral. Fig. 2 (Slide 2) presents the proportion of + responses as
Insert Fig. 2 about here
a function of age with judgments from all the different groups combined
with different instructions in order to reveal, in general,
pleasantness of each odor as a function of age.
These data agree with those reported by Stein et al. in showing a
marked change with age, particularly from four to five, for the odor of
butyric acid. Four-year-olds apparently liked this odor, while the
older children disliked it. Analysis of the data by chi square
indicates that these age.differences are reliable (p<.001). The age
differences for amyl acetate, safrol, and diethyl phthalate are not
reliable. However, the proportion of + responses from each of these
odorants is higher and reliably different (p<.01) from .50 (or neutral)
62
68
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T. Engen
for all four age groups, indicating that these are pleasant odors.
This is to be expected for safrol and amyl acetate but not for diethyl
phthalate, the relatively odorless and qualitatively neutral "blank."
This indicates that the children had a tendency to say they liked an
odor whether they smelled it or not. Indeed one child reported "they
smell good" before he had sniffed anything! Note that this response
tendency would inflate the reliability index used above.
The general problem is that different questions apparently differ
in their tendency to elicit biased responses. For example, asking a
positively phrased question seemed to produce false positives, while
stating the same question in a negative form yielded both negative and
positive responses as one might have expected. No semantic
generalization can be made on the basis of the present limited
experiment, but it represents a fundamental problem in odor
acceptability. As suggested by Cederlbf et_ al. an indirect approach is
often required in this field of measurement.
Fig. 3 (Slide 3) shows the proportion of + responses obtained for
Insert Fig. 3 about here
each age group when the results from all four odorants are combined;
that is, this graph is intended to show the relative frequency of +
responses to different instructions regardless of the pleasantness of
the odors. The change in response as a function of age is significant
(p<.001) for the question "Tell me if it smells pretty." The other
three instructions produced about equal proportions of + and -
responses (roughly around .50) and no reliable change as a function of
63
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T. Engen
age. Therefore, the biased response involved in this kind of
experiment seemed to vary with the instructions. That is, one reason
for the high number of + responses shown in Fig. 2 (Slide 2) for all
odorants except butyric acid is the tendency for most of the children
to agree when asked "Does it smell pretty?" Presumably the same
explanations apply to the widely quoted data by Stein et al. who were
asked the same kind of question, although their paper does not provide
much detailed methodological information. The difference in the
frequency of + responses related to the form of the question is
reliable at p<.001, .01, .05, and .20 for ages four, five, six, and
seven, respectively.
Fig. 4 (Slide 4) showed the responses obtained for butyric acid
only, but this time for different questions. These results are
consistent with those already shown, indicating again that the
developmental change in the hedonic value of butyric acid is probably
Insert Fig. 4 about here
an artifact of the opinion-polling method. What really changes as a
function of age may be the response bias. This seems to provide a
simple alternative to the Freudian interpretation which suggests that
body odors which are liked become disgusting as a result of reaction
formation. Even if the response biases should be eliminated
statistically, the effect of age would be reduced, but butyric acid
would still be rated as unpleasant.
However, Moncrieff, who also suspects that young children may have
a greater tendency than adults to say, "yes, I like it," although for a
64
68
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T. Engen
different reason, asked his subjects to rank-order the odorants in
terms of pleasantness. He comes to the conclusion that "Children
exhibit a remarkable tolerance for substances with a fecal note in
their odor; they do not like these substances but they are more or less
indifferent to them, whereas the adults actively dislike them." (p. 80)
His subjects, who were older (about 7 to 15) and presumably more or
less beyond the Oedipal conflict, ranked these substances higher, or
more pleasant, than the adults did. This rank-order method should
eliminate verbal and semantic problems discovered with the present
method. The disadvantage with the rank-order method is that the
scoring of responses is relative, with the result that odors put in the
middle of this scale are "neutral" by definition, while those ranked
low are "unpleasant" and those high are "pleasant." For example, one
could not give all odors a high rating if that seemed appropriate.
The method needed must eliminate verbal responses and make
possible a quantitative comparison of preferences. One approach to
this problem is represented by the now classic work of Thurstone (1959)
on The Measurement of_ Values. Thurstone provided both a mathematical
theory of psychological measurement, the so-called law of comparative
judgment, and methodology applicable to the scaling of attributes for
which there are no specifiable physical correlates. The most commonly
used method is the method of pair comparison. The subject's task is
simply to compare two stimuli, and every stimulus is usually compared
with every other stimulus. Our second developmental study (Engen and
Corbit, 1970) scaled the preferences for the odors of butyric acid,
-------
T. Engen
safrol, diethyl phthalate, rapeseed oil, and nerioli oil. The txro last
odorants were included because Moncrieff's (1966) result suggested that
they are examples of oily odorants which seem especially aversive to
children 6 years old or younger. The odorants, except for the diluent,
diethyl phthalate, were first matched in subjective intensity to the
relatively weak odor of undiluted rapeseed oil. Five groups of
subjects were tested; there were 26 four-year-olds, and groups of 28
five-, six-, and seven-year-olds in addition to a group of 28 adults.
The 10 pairs of these five odorants were presented to each subject
individually following the same general procedure as above. The order
of presentation of the 10 pairs was balanced to eliminate possible
sequence effects. The first pair of odorants presented to the subject
was repeated at the end of the series to obtain an estimate of the
reliability of the judgments. The percentage of the subjects judging
this pair the same in both cases was 69, 64, 75, 71, and 93 for the four-,
five-, six-, and seven-year-olds and adults, respectively. This is
obviously an important and interesting difference between children and
adults, but it will not effect the comparison to be considered next.
Insert Table 1 about here
Table 1 illustrates the data obtained with this method with the
results from the six-year-old subjects. The entries in Table 1
(Slide 5) are the proportions of the subjects in that particular group
who preferred one odorant over another. These proportions are
obtained by dividing the number of six-year-olds who preferred, for
example, rapeseed oil over butyric acid by the total number of subjects
70
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T. Engen
(28). This value is .786 and is entered in the second column of the
first row of Table 1. The proportion who preferred butyric acid over
rapeseed oil is 1.000 - .786 = ,214,as entered in the second column of
the first row of Table 1.
In this raw form the data provide no information about the hedonic
value of any single odor. This is where Thurstone's mathematical
theory is applied. In essence, it entails making the assumption that
the hedonic effect of any one odorant forms a normal distribution when
plotted for a group of individual judges. One can then make use of the
known relationship under the normal curve between proportions and
so-called standard scores (or Ł scores) for which by definition the
mean is zero and the standard deviation is 1.00. Scores below this
mean (the minority vote) will then be negative in sign and scores above
this mean (the majority vote) will be positive in sign. Since,
according to the theory, the preference values of each odorant for
different individuals are normally distributed, these standard scores
will represent the psychological distance between these hedonic values
for different odors.
Insert Table 2 about here
Table 2 (Slide 6) shows these standard scores based on the
proportions shown in Table 1. Each entry in this table corresponds to
the distance on the preference scale between a certain pair of odorants
For example, for butyric acid and rapeseed oil this value is .31
standard deviation (with the sign indicating that rapeseed oil is
preferred by the group) . The best estimate of the hedonic value of
67
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T. Engen
each single odor will be obtained by taking the mean of the values of
each column in Table 2. These values represent all the information
about each odorant in the set. These means represent relative scale
values on a hedonic continuum or a psychological scale of preference.
Since these are not absolute numerical values, it is not possible to
determine, for example, whether the children give higher (or lower)
value ratings of the set of odorants than adults, but certain other
important quantitative comparisons can now be made.
Insert Table 3 about here
Table 3 (Slide 7) summarizes the scales obtained for the five
different groups. First, inspection of these values will reveal
clearly that children do not discriminate as well between odorants on
this preference scale as do adults. Second, the older the children the
more their scale values agree with those obtained for adult subjects.
This is also indicated in the column on the right by a comparison of
the range of values represented by this set of odorants for the various
groups. However, the preferential order of the five odors is more or
less the same for all five groups.
Finally, it is interesting and noteworthy that a weak and
nondescript odor like diethyl phthalate, often used as a diluent
because it is nearly odorless, is again consistently judged as pleasant
(that is, positive sign). The suggestion is offered by Moncrieff
(1966), as a result of observing the same effect with the children in
his group, that "he smells best who smells nothing." Another possible
interpretation is that the positive scale value is a measure of
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response bias similar to the one discussed above. Still another is
that it is the effect of the context provided by the stimulus set;
that is, a neutral stimulus may be judged as relatively pleasant or •
unpleasant depending upon the comparison stimuli. If, for example,
butyric acid should be replaced by an odorant even more pleasant than
safrole, the whole preference scale might shift such that the value of
diethyl phthalate might seem less (see Sandusky and Parducci, 1965).
In general, the preferences of children and adults are similar.
However, the present data do not reject the hypothesis of Moncrieff
(1966) that children find all odors more pleasant than adults. It is
possible that the children's preference scale is placed toward the
pleasant end of the continuum relative to the adult scale, but the
relative placement of individual odors is the same. A fairly high
proportion of the children did prefer butyric acid over considerably
more pleasant odors, as judged by adults. The developmental change in
the size of the range related to age indicates that the older the
children the more the preferences agree with those of adults and lends
evidence to the hypothesis that discrimination of hedonic attributes
of odors is learned. Except for trigeminal stimulation, and
unusually strong concentrations, there may be no inherently
unpleasant odors.
Earlier work (Engen, Lipsitt, and Kaye, 1963; Engen and Lipsitt,
1985) has shown that even newborn infants respond to odors. This
response, even to odorants such as anise judged very pleasant by
adults, resembles a mild "defensive" or "startle" response, but the
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hedonic nature of the response could not be firmly established.
However, it seemed clear that an odorant has the effect of a novel
stimulus, the response to which diminishes through habituation and
familiarization as the result of repetitive and otherwise uneventful
stimulation.
Hedonic responses may be acquired as the result of experience with
food, sex, and the value system of adults. Perhaps children learn how
to describe initially natural olfactory experiences by observing adults'
behavior. There should be no difficulty in teaching a person to
experience the smell of skunk as something pleasant, provided one could
control the circumstances under which it was experienced. The anecdotes
about odor memory and individual associations (e.g., Kenneth, 1923)
seem to fit this interpretation, as do cultural differences in choice of
perfume odors (Moncrieff, 1966). It should be noted that the original
assumption of our research on this topic was that it is feasible to
code household goods with odorants, that is, to make them smell bad
in order to keep children away from them. Our conclusion so far is
very clearly that one cannot depend on unlearned or inherent aversive
reactions to accomplish this, although we are still working on the
project by testing other odorants.
It is reasonable to assume, however, that this kind of project
might be successful with.adult subjects, for it is a matter of common
observation that adults are very cautious with respect to odors. This
is easily demonstrated by presenting them with a bottle xvith
instructions to smell it. One is not likely to find a person who will
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start out by taking a strong sniff of that bottle. In Western
civilization "smell" and "odor" often imply something unpleasant or
distasteful. The reason for this slanted view is not clear, but
advertising clearly takes advantage of it.
Some experiments in odor identification and memory have provided
some data pertinent to this notion. A group of 30 adult men and women
were asked to sniff each of 48 diverse odorants, ranging from pure and
simple compounds (e.g., 1-Propanol) to complex household products
(e.g., soy sauce). Each person was asked, first, to say whether or not
the odor was familiar and, second, whether he liked, disliked, or felt
indifferent about it. He was not required to name the odorant, or
identify it in any technical sense, although often he did, but only to
indicate knowledge of it from previous experience. He was encouraged
to use a high criterion for both judgmental categories, that is, to
respond that he did not know and that he was indifferent whenever he
was uncertain. Each subject was tested individually and each received
a different set of 48 odorants drawn at random from a larger common set
of 100 odorants. This sampling procedure is important for it makes
possible more general observations.
Insert Table 4 about here
Table 4 (Slide 8) presents the average proportions of ratings
of "like," "dislike," and "indifferent" for "familiar" and "unfamiliar"
odors. The difference in the distributions of hedonic ratings of
familiar and unfamiliar odors is very clear. Forty-six percent of the
familiar odors were judged as pleasant and only 25 unpleasant, whereas
71 75
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T. Engen
only 11 percent of the unfamiliar odors were judged as pleasant, but
50 percent were judged as unpleasant. This trend is also very
consistent for individual subjects with a total of six exceptions for
the 60 possible comparisons. In other words, if an odor is unfamiliar
to a person he is unlikely to rate it as pleasant. This is not the
result of there being some very ill-smelling odorants in the set.
Analysis of individual data show that the same odorant may be found in
any of the six cells in Table 4. Approximately half of the odorants
were judged "pleasant" by the average subject. An odor that is
familiar and pleasant to one subject may be unfamiliar and unpleasant
to another, etc. There were, of course, a few odors (e.g., pyridine)
judged unpleasant by all who happen to receive it in his sample, and
some of them had prior experience with it and some did not. In
general, however, this is a psychological response-response
relationship that must be understood in terms of the individual's prior
experience with specific odorants and in that sense the psychology of
odors.
There are a number of possible methods mentioned in Beebe-Center's
(1932) book on The Psychology of_ Pleasantness and Unpleasantness in
addition to those described above for dealing with odor preferences and
scaling. All of them assume that pleasantness or hedonics represents a
perceptual dimension that can best be described by adaptation of
classical psychophysical methods. However, if it is the case that
psychological preferences are individualized and dependent upon
learning as the present data and most literary accounts of olfaction
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suggest, then another approach and other methods would be helpful. One
would first of all need to think about the learning paradigm that
illuminateshow hedonic associations to odors are acquired. For a
start, consideration of the learning of language and the meaning of
words and signs would seem relevant. Our question is: "Under what
conditions does a neutral odor become pleasant or unpleasant?" One
simple theory is that it can be explained as the result of simple
classical, or Pavlovian, conditioning through which an odor (the
conditioned stimulus) becomes associated with and capable of eliciting
part of the response originally associated with the unconditioned
stimulus. For example, eating spoiled food (unconditioning stimulus)
makes one sick (the unconditioned response); the smell of food (the
unconditioned response) is associated with the food and is later
sufficient to elicit part of the unpleasantness of being sick (the
conditioned response). The perception of the odorant thus acquires
hedonic value because it comes to mediate or signify an emotional state
through a process that is related to the general problem of meaning.
Psychologically this seems to involve the generalization of a mediation
process so that the original emotional response may be aroused by other
odorants or olfactory situations, including words describing the
situations such as "smell," to the extent that they are similar to the
original one.
This approach would hardly be sufficient to explain all odor
association, especially the development of odor preferences, and some
other form of acquisition would seem necessary. It is not unlikely
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that most of our attitudes are learned through imitation of and
guidance by parents or other desirable models used by advertisers.
Being stimulated by the same odorant as the adult and observing his
behavior would be sufficient for acquiring both the motor and cognitive
aspects of the adult's response in the situations. The effect of
prestigeful models on the food preferences of children has been
demonstrated (Duncker, 1938), and such models may provide them with the
social norm for appropriate behavior in various situations (see
Bandura, 1962). The change in preference may take place quite
unconsciously through a kind of reorganization of the perceptual
attributes associated with the stimulus-object.
To the extent that the hedonics of odor is a matter of acquired
meaning of odorants, then the traditional organoleptic or
psychophysical technology should be supplemented with methods for
measuring such psychological processes. Some of these methods seem
promising. First, the "free association technique" could easily be
adopted to the odor problem. As normally used, this method consists of
presenting a word to a subject with instructions to respond with
whatever comes to mind, assuming that what does come is not free at all
but determined by the meaning the stimulus has for the person. For the
present purpose, one would merely substitute odorants for words. Such
a procedure would probably be quite productive, judging from similar
adaptations of this method in the study of colors as stimuli compared
with color words (Osgood, 1953).
Techniques for scaling meaning would seem to have great potential
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T. Engen
in this field. Essentially, these methods use traditional psychometric
rating methods, but instead of being limited to one adjective, e.g.,
pleasantness, one uses a number of adjectives or concepts that appear
to be relevant to the stimulus material in question in an attempt to
find the significant ones. In applying this approach Hosier (1941)
found that " the meaning of a word may be considered as if it
consisted of two parts, one constant and representative of the usual
meaning of the word, one variable, representative of individual
interpretation in usage and associated context and general usage "
(p. 139). The possibility of substituting "odorant" for "word" in that
statement should be explored.
Similarly, Osgood's (1952) "semantic differential" could be
applied to the odor problem with benefit. It is a multidimensional
approach that combines the above scaling method and the free
association technique, and attempts to reduce the description of the
meaning of a stimulus, the "semantic space," to a few bipolar
dimensions. These semantic dimensions are derived with the use of
factor analysis of the ratings of each stimulus on the larger number of
bipolar dimensions used originally.
Finally, it is often observed that individual differences in
judgments of odors is unusually large. However, the evidence that the
judgments of the individual subject is consistent from session to
session should not be ignored. Young (1923) showed that affective
judgments, as he called them, are characterized by large
inter-individual variation but small intra-individual variation. The
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reason for the large individual differences may be the result of
different experiences of different people with respect to any one
dimension, for example, pleasantness. This kind of variability reduces
the reliability of most measures of preference based on average
judgments from groups of subjects. It seems fair to assume that one
might reduce this variability and understand odor preferences better on
the basis of a separate analysis of data from each individual on a
large number of potentially revealing dimensions of meaning. There are
as yet only anecdotes about how the individual's experiences influence
his preferences and associations to odors. The procedures suggested
above stand a good chance of providing more systematic and quantitative
information.
-oOo-
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REFERENCES
1. Bandura, A. Social learning through imitation. In M. R. Jones
(Ed.)» Nebraska Symposium on Motivation. Lincoln,
Nebraska: University of Nebraska Press, 1962.
2. Beebe-Center, J. G. The Psychology of_ Pleasantness and
Unpleasantness. New York: Van Nostrand Co., 1932.
3. Cederlb'f, R., L. Friberg, E. Jonsson, L. Kaij, and T. Lindvall.
Studies of annoyance connected with offensive smell from
a sulphate cellulose factory. Nordisk Hygienisk
Tidskrift. 1964, 45, 39-48.
4. Duncker, K. Experimental modification of children's food
preferences through social suggestion. Journal of
Abnormal and Social Psychology. 1938, 33, 489-507.
5. Engen, T., and T. E. Corbit. Feasibility of Olfactory Coding of
Noxious Substances to Assure Aversive Responses in Young
Children (Publication ICRL-RR-69-6 Injury Control Research
Laboratory). U. S. Department of Health Education, and
Welfare (Public Health Service, Environmental Health Service),
1970.
6. Engen, T., and H. I. Katz. Odor preference and response bias in
young children. Unpublished manuscript, Brown University, 1968.
7. Engen, T., and L. P. Lipsitt. Decrement and recovery of responses to
olfactory stimuli in the human neonate. Journal of
Comparative and Physiological Psychology, 1965, 59, 312-316.
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T. Engen
8. Engen, T., L. P. Lipsitt, and H. Kaye. Olfactory responses and
adaptation in the human neonate. Journal of_ Comparative
and Physiological Psychology, 1963, 56, 73-77.
9. Engen, T., and D. H. McBurney. Magnitude and category scales of
the pleasantness of odors. Journal o_f Experimental
Psychology, 1964, 68, 435-440.
10. Guilford, J. P. Psychometric Methods. (2nd ed.) New York:
McGraw-Hill, 1954.
11. Harper, R., BC.Bate-Smith, and D. G. Land. Odour Description
and Odour Classification. London: Churchill, 1968.
12. Kenneth, J. H. Mental reactions to smell stimuli. Psychological
Review. 1923, 30, 77-79.
13. Kniep, H. H., W. L. Morgan, and P. T. Young. Studies of affective
psychology. XI. Individual differences in affective
reaction to odors. American Journal o_f Psychology. 1931,
43, 406-421.
14. Moncrieff, R. W. Odour Preferences. New York: John Wiley, 1966.
15. Mosier, C. L. A psychometric study of meaning. Journal of_ Social
Psychology. 1941, 13, 123-140.
16. Osgood, C. S. The nature and measurement of meaning. Psychological
Bulletin, 1952, 49, 197-237.
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17. Osgood, C. E. Method and Theory in Experimental Psychology.
London: Oxford University Press, 1953.
18. Sandusky, A., and A. Parducci. Pleasantness of odors as a function
of the immediate stimulus contex. Psychonomic Science,
1965, 3, 321-322.
19. Stein, M. , P. Ottenberg, and N. Roulet. A study of the development
of olfactory preferences. A.M.A. Archives oŁ Neurology and
Psychiatry. 1958, 80, 264-266.
20. Third Karolinska Institute Symposium on Environmental Health.
Nordisk Hygienisk Tidskrift, 1970, 51(2).
21. Thurstone, L. L. The Measurement of_ Values. Chicago: University
of Chicago Press, 1959.
22. Young, P. T. Constancy of affective judgments to odors. Journal
of Experimental Psychology. 1923, 6, 182-191.
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FOOTNOTE
Part of this research was carried out with support from the
U.S. Department of Health, Education, and Welfare through The Injury
Control Research Laboratory, Providence, Rhode Island.
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T. Engen
TABLE 1
Proportion of Choices of Odorants
Each entry is the proportion of six-year old subjects
preferring the odorant in the row to the corresponding odorant
in the column on the left. Each matrix gives the results for
a different age group.
Odorant
Butyric Rapeseed Diethyl Neroli
Acid oil phthalate oil
Safrole
Butyric acid
Rapeseed oil
Diethyl phthalate
Neroli oil
Safrole
.214
.179
.214
.071
.786
.321
.250
.321
.821
.679
.393
.214
.786
.750
.607
.464
.929
.679
.786
.536
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T. Engen
Table 2
Standard scores for pairs of odorants based on the
proportions in Table 1.
Odorant
Butyric acid
Rapeseed oil
Diethyl phthalate
Neroli oil
Safrole
E
M
Butyric
acid
-.81
-.92
-.81
-1.48
-4.02
-1.00
Rapeseed
oil
.81
-.47
-.67
-.47
-0.80
-0.20
Diethyl
phthalate
.92
.47
-.28
-.81
+0.30
+0.08
Neroli
oil
.81
.67
.28
-.10
+1.66
+0.42
Safrole
1.48
.47
.81
.10
+2.86
+0.72
86
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T. Engen
Table 3
Hedonic scale values for five odorants
from five different age groups
based on pair comparison
Age group
4
5
6
7
Adult
Butyric
Acid
-0.55
-0.77
-1.00
-1.05
-2.00
Rapeseed
oil
-0.15
0
-0.20
-0.40
-0.54
Diethyl
phthalate
+0.23
+0.26
+0.08
+0.37
+0.42
Neroli
oil
0
-0.02
+0.42
+0.34
+0.81
Safrole
+0.48
+0.53
+0.72
+0.74
+1.30
Range
1.03
1.30
1.77
1.79
3.30
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T. Engen
Table 4
Response-Response Relationships in Judgments of Odors.
Proportion of judgments of "like", "dislike", and
"indifferent" of odors judged to be "familiar" or
"unfamiliar". The entries are proportions based on
inspection by each of 30 subjects of a set of 48
odorants drawn at random from a common set of 90
odorants.
Response "Familiar" "Unfamiliar"
"Like" .46 .11
"Dislike" .25 .50
"Indifferent" .29 .39
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T. Engen
FIGURE CAPTIONS
Figure 1. The development of olfactory preferences. The responses
are expressed as the percentage of pleasant reactions. (From Stein,
Ottenberg, and Roulet, 1958.)
Figure 2. Proportion of judgments indicating the relative
pleasantness of the odor (+) of each of four different compounds
plotted as a function of the age of the S_s.
Figure 3. Proportion of judgments under various instructions
indicating that the degree to which an odor was judged pleasant (+) as
a function of age regardless of the odorant. Data obtained from four
different odorants in Fig. 1 have been pooled to evaluate the effect of
different instructions, P, U, UoP, and Poll described in the text.
Figure 4. Proportion of judgments under various instructions
indicating the degree to which butyric acid was judged pleasant (+) as
a function of age.
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PHYSIOLOGICAL RESPONSES TO ODORANTS
by
David A. Kendall and Stanley P. Jacobs, Ph.D.
Arthur D. Little, Inc.
Presented at the Symposium
The Dose-Response Relationships Affecting
Human Reactions to Odorous Compounds
April 26, 1971
Cambridge, Massachusetts
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PHYSIOLOGICAL RESPONSES TO ODORANTS
by
David A. Kendall and Stanley P. Jacobs, Ph.D.
Most of the reported information on odor studies has been based on
written or verbalized reports of individuals. Generally a stimulus is
presented and the subject is asked to report his observations. Where a
limited number of people participate, they are often given training or
gain it as a result of repeated trials. Randomly presented unodorized
controls are helpful in estimating the frequency of incorrect responses.
Alternatively, populations may be asked to recall from memory their ex-
perience with odors and such reports can be used to describe an odorant's
effect.
As has been indicated > there are clearly two kinds of responses to
an odorant. One is the detection of a stimulus, i.e., the recognition
of a neural response. The second is the subjective reaction to that
stimulus in terms of pleasantness or hedonic quality. There may be a
93
Arthur DLittldnc
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third level of response, i.e., detection at sensory end organs followed
by some autonomic response without the individual's awareness of the odor.
One can argue that recognition of any odor, particularly if man-made,
constitutes a problem from an odor pollution standpoint. However, as
anyone who has attempted to build an olfactometer knows, producing odor-
less air even in a laboratory is not an easy task. There is a volume of
information on the other hand which indicates that certain types of odors,
notably effluents from kraft mills, cause a high frequency of complaints
(30% of the respondents as far as 20 km away, {Lindvall}).
Increasingly in the food acceptance area, there is interest in
measuring response by means of the individual's performance in contrast
to a verbalized or written statement. Remember the low, chrome, conser-
vative automobile designed to meet consumers' wishes which did not sell.
Although these methods may have somewhat less sentitivity, they may be
essential for reflecting the true attitudes of the individuals toward
the products or pollution. This approach has been taken in the techniques
discussed by Mr. Flesh concerning the economic effects of "odorous" air
pollution on property values.
Arthur D Little Inc
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Studies have been carried out in the past where one or more physio-
logical parameters have been measured as indicators of a response to an
odor stimulus. In the recent report by Neuhaus and Goldenberg skin re-
sistance, arterial pulse and blood pressure, gastric motility and respira-
tory movements were monitored and changes noted as a result of both audi-
tory and olfactory stimulation. Dr. Engen measured changes in respiration
with infants as a result of odor some years ago. It would appear reasonable
that perception of odor might be reflected in the character of the respira-
tion curve and that an unpleasant reaction to odor might produce changes
in physiological parameters, analogous to the "scare reactions" on which
lie detectors are based.
One of the requirements for such a study is to present the odorant
so that the performance of the test does not interfere with the responses
that one wishes to monitor. To our knowledge no extensive effort has
been made to present odorants on a totally blind basis controlling both
concentration and duration of stimulus while monitoring a number of
autonomic responses. The purpose of this study, which was carried out
initially under the auspices of the Manufacturing Chemists Association
and subsequently has been supported in part by the Air Pollution Control
95
Arthur D Little, Inc
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Office, is to learn whether such methods might provide more reliable
indicators of a population's response to various odorant presentations.
Initially we hope to learn which, if any, physiological parameters
correlate with detection of odor and whether these responses change in
character or magnitude as the concentration or duration of stimulus is
altered. Hopefully by considering a response pattern one might be able
to describe an adverse hedonic response as compared with a benign or plea-
sant experience.
The preliminary trials with the system are most encouraging. With
highly trained analysts verbalizing their response to odorants in
various presentations, we detected a three-second time delay in the
hydrocarbon analyzer system. There are indications that this system
may be useful for studying habituation and fatigue as a function of
duration and concentration. It would also be most interesting to study
the effect of the rate of change in odorant concentration on the perceived
intensity.
The untrained subjects were able to recognize and report on their
odor experience with good agreement. The population showed significant
changes in all four of the physiological parameters measured. Although
35 Arthur D Little Inc
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we are not certain as to the meaning or importance of these changes, in
several instances significant effects were only observed as a result of
the interactions of the concentration, duration, and odorant. Also of
interest are the few individuals who profess not to be able to detect
any or all odorant treatments but whose autonomic responses indicate
some effects coincidental with the sample presentation.
This report covers the description of the equipment for sample
presentation and monitoring of the autonomic responses; the results of
orientation trials with expert and untrained observers; and the test
design and recent observations with untrained but repeat performing
observers.
Test Chamber
As one of the essential elements of this study, we have constructed
a test facility which permits completely blind sample presentation as well
as control and measurement of the odorant stimulus at the subject. The
test chamber is a 6* x 3' x 41 cabinet constructed of aluminum. The entry
door and glass windows are located in the side walls. A frosted glass
panel is recessed into the front wall to allow reverse projection of
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Arthur D Little Inc
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taped or filmed viewing material. Video monitoring of the subject is
possible through a small porthole.
The air supply for the chamber is drawn through a fiberglass pre-
filter and Dorex® activated carbon canisters. After the odorant in-
jection point, the air passes through a Static Mixer® to assure uniform
distribution of odorant. The air is then directed through the entire
front panel of the chamber, past the seated subject and is exhausted
from the rear plenum by means of a 2 HP constant speed exhaust fan.
Flow rate can be .varied by adjusting a damper to shunt outside air
directly through the fan. The flow rate through the chamber can thus be
varied from 150 to 400 cfm.
The subject is seated in a swivel chair facing the front panel of
the chamber. An aluminum shelf at arm height was installed to minimize
the effects of the turbulent flow from the lower half of the chamber.
Care was taken in the design of the dispersion plate to assure uniform
flow across the top half of the chamber at the plane of the subject's
face. A sampling point located directly above the subject's head provides
access for the Beckman Model 109-A hydrocarbon analyzer which monitors
the hydrocarbon content of the air stream. A Keithley Model 410
9 Arthur D Little Inc
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microammeter has been substituted for the Beckman unit to reduce the
inherent electronic time delay of the circuit. The air flow rate
selected both for comfort and speed of odor clearance for these experi-
ments has been 210 cfm which results in a linear flow of about 20 feet
per minute. This represents volume flow through the chamber of 100
liters per second.
A Harvard syringe pump injects carrier solvent (hydrocarbon) and
odorant into the air stream after the carbon filter. Although the range
of gear settings provides a more than adequate range of constant flow
rates, at any single gear ratio the rate can be varied remotely from
5-100% of the maximum. Using a gear setting of 6 and a 2 milliliter
syringe, the flow rate can be varied from 0.1 to 2.0 microliters per
second. The duration of the stimulus can be remotely controlled from
10 to 300 seconds. The appropriate odor concentration is produced by
dilution in the carrier solvent. For these experiments reagent grade
nonane, boiling point 154°C, has been used as the carrier. It is not
readily apparent at four times the use concentration. The concentration
of odorant in the carrier is adjusted to allow intervals of 1, 4 and
B9
Arthur D Little Inc
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16 times a minimum recognizable concentration for the odorant at one
gear setting. ••• . • • ••• • • '-••*•'•• • ••''•' ••'•''• *: .y... ' ."
Test Protocol
The subject is continuously immersed in the air stream. Odorant
samples representing randomly selected treatment conditions are pre-
sented at intervals during the course of a 30-minute test period. In
reality, the first ten minutes of the session are taken up by attachment
and adjustment of monitoring electrodes plus a stabilization period.
Six odorant presentations can be completed during a 15-minute period.
The presentation of the stimulus is completely blind with no suggestion
for smelling. The only change in the conditions within the cabinet is
the presence of the carrier solvent below 2 mg/100 liters and the odorant.
The physiological parameters monitored are ECG, using three electrodes
(two on the right arm and one on the left); peripheral blood flow by
means of an ear piethysmograph from which is computed the instantaneous
• i"'. ..;•.'
heart rate. The respiration is monitored by means of a pneumograph and
from this is computed the integrated respiration volume. Palmar sweating
is measured by galvanic skin resistance electrodes on both the right and
Arthur DLittldnc
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left hand. All the data is accumulated on an eight-channel thermo-
recording Hewlett Packard polygraph. This is equipped with an eight-gun
oscilloscope for displaying any or all signals.
The output of the hydrocarbon analyzer and the differential pressure
in the chamber are recorded to monitor the test conditions. The indivi-
dual's appearance and attitude are observed by closed circuit television
with the opportunity for recording this on tape. We have not attempted
to evaluate this information since it appears to be highly variable from
individual to individual.
There are opportunities for additional measurements which might be
more responsive to the variations in odorant presentation. We have the
necessary transducers available to measure EEC and EMG and have considered
some possibilities for air flow measurements at the nares.
Exploratory Studies
Preliminary studies were carried out with relatively volatile
odorants such as ethyl mercaptan, methyl isobutyl ketone and carbon
disulfide. Overt reactions such as sniffing or tasting the air, facial
movements, actual frowning or grimacing to express discomfort, and
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Arthur DLittldnc
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10
indications of simple awareness of odor such as eye opening or twitching
were apparent when the concentration of the odorants was substantially
above the minimal detectable level, i.e., between 10 and 40 times threshold.
During this period, equipment was not available for controlling the flow
rate of odorant-carrier solvent and therefore all samples were injected
substantially instantaneously although the concentration within the
test chamber was apparently 80% of its maximum for about 7 seconds.
Under these conditions changes were noted in the heart rate, the respira-
tion rate and the character of the respiration curve, i.e., either
irregular rate or shallower or deeper volume. No particular pattern
could be distinguished from these results to associate with a particular
odorant. In several instances, the test subjects did not report the
detection of one or more of the presentations even though variations were
apparent in their autonomic responses coincident with the odorant pre-
sentation. With the addition of the Harvard syringe pump and its auto-
matic timing control, studies were carried out with a trained panel to
determine the minimum detectable concentration in the test chamber for
comparison with previously obtained data in the static test chamber.
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After overcoming the problems of continuous uniform injection of solvent
into the air stream by adding aluminum heating blocks and reducing the
bore of the syringe needle to 27 gauge, it was possible to present the
odorant at a desired concentration with less than 20% variation in con-
centration during the 200-300 second interval. By varying the tempera-
ture of the heating block, it was possible to test a variety of odorants
of lower volatility. However, the selection is still limited. After
screening a number of different materials, amyl acetate was selected
as a "pleasant" odor and tetrahydrothiophene as the "unpleasant" odor.
Both of these compounds have been used with some frequency in odor
research by various workers. Using experienced analysts who reported
orally their sensations in the test chamber, studies were undertaken to
examine intensity of perceived odor as a function of time during a 300-
second test period. Using amyl acetate, the odorant was perceived some
3-5 seconds before it was detected with the total hydrocarbon analyzer.
With the highest test concentration, the maximum intensity was recorded
as much as 8 seconds before the hydrocarbon analyzer. The discrepancy
between the apparent intensity and the detected concentration was found
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to be due in part to time delay in the electrometer circuit of the hydro-
carbon analyzer, and this was reduced by substituting a Keithley unit.
A second delay may result from sample holdup in the gas sampling system
to the flame. This has not as yet been corrected. A most interesting
observation, however, was the apparent decrease in intensity of odorant
during the longer exposure intervals. This was particularly evident
with amyl acetate. One subject after 120 seconds was not aware of odor
in the test chamber, although the concentration was constant. A second
subject was aware of only a low intensity of odorant during the exposure
time after 100 seconds. From comment and actions in the preliminary
trials, both amyl acetate and tetrahydrothiophene seemed to represent
the degree of separation in "pleasantness" that might be necessary to
observe differences in autonomic responses. Through repeated studies
with the trained group, a concentration of amyl acetate of 64 mg/ml of nonane
was found to produce a reasonable range of odor intensities within the
flow rate constraint of a single gear setting of the syringe pump required
for fully remote manipulation.
With 100% flow at gear setting 6, the delivery was found to be 2
microliters per second. Since the air flow in the chamber is 100 liters
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per second, this results in a calculated concentration for amyl acetate
of 128 micrograms per 100 liters. For the short duration only 80%
maximum long term FID response was attained because of the dispersion of
the peak. Thus, the concentration of the amyl acetate was close to 100
micrograms per 100 liters. The minimum test concentration of amyl
acetate, based on the flame ionization response to nonane, was 6 micro-
grams per 100 liters of air and the intermediate concentration was 25 micro-
grams per 100 liters. For the longer durations (over 60 seconds), the
percent flow was reduced to give a comparable detector response.
The concentration selected for tetrahydrothiophene in nonane was
0.56 milligrams per milliliter. At the maximum flow rate of 2 micro-
liters per second the maximum concentration of tetrahydrothiophene for
the 15 second duration was 80% of 1.1 micrograms'per 100 liters of dilu-
tion air or 0.88 microgram per 100 liters. The lower concentrations were
0.22 microgram per 100 liters and 0.05 microgram per 100 liters.
The pen deflections from the flame ionization detector measuring
nonane for these three dose rates were 6-7 mm, 24-26 mm for the low and
intermediate concentrations and, with 5X attenuation, 20-22 mm for the
high dose rate. The detector response value was maintained regardless j_OD
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of duration or odorant during a single day of testing. Although, some
variation in specific detector response has been noted from day to day,
the ratios between concentration remained constant.
Test Design
It is the purpose of this program to determine whether autonomic
responses can provide useful information concerning human detection of
odorants and second to aid in defining what might be considered unpleasant
or annoyance reactions to odor. It is quite easy to postulate that the
type of odorant, its concentration, and the duration of exposure are
important in detection and recognition but the interactions of these
three factors could be most significant in producing annoyance.
Any test design therefore had to allow for at least two odorants
at two time durations and at two concentrations. Since there was some
concern as to the appropriate concentrations, a third level of this
factor was included.
It was essential to design the test to yield the maximum amount of
information not only of the effects of each of the three factors, but
also the effects of interactions. Also in the development of a test
protocol, it was agreed that no more than six exposures would be presented
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in any one session. Thus, in order to produce a complete block design,
the total number of treatments (12) were separated into two blocks of
six. Dr. Irwin Miller located the reference to a 3 x 2 x 2 factorial
test design confounded in two blocks of six with a description of the
analysis. To balance the test, three replicates containing two blocks
must be included in each iteration. Each group of replicates could be
reiterated as many times as desired. Although three iterations appeared
to be adequate, the three replicates were reiterated four times. Twelve
subjects were randomly assigned to one of the three replicate groups
which defined the six treatments to be included in each of the two
blocks. Although the treatments in each block were assigned, the order
of presentation for both blocks and treatments within blocks was
randomized.
In order to test the system and give the subjects experience with
the procedure, each subject was given a training session which included
six presentations in an undefined order. Although the response data was
collected, it was not intended for analysis. At the conclusion of the
test, one iteration of the three replicates was carried out with three
of the subjects to provide information on intrasubject variability.
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This data has not been analyzed at the present time.
At the conclusion of each test, the subject was asked what odors
he had perceived, how many times and in what order. He was then asked
to indicate which were pleasant and unpleasant. This provided the oral
response information to be compared with the physiological responses.
Data Acquisition
Although it is quite obvious in many cases to observe changes in the
physiological parameters that coincide with the initiation of the stimulus,
a standard method for tabulating the data had to be defined. Since
there was no certainty which, if any, of the variables might reflect
differences between treatments, and review of the polygraph data was time
consuming, a variety of measurements were taken so that additional inter-
pretations could be made. It was convenient to take all measurements in
millimeters. In most instances the measurement during the stimulus was
compared to a measurement taken during a 15-second control interval
prior to the initiation of the treatment. A primary criterion for
initiating a test was the visual assurance of normality in the polygraph
readout.
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1. Instanteous Heart Rate (IHR)
a. the maximum and minimum instantaneous heart rates during
the 15-second interval prior to the initiation of the treatment;
b. the maximum and minimum heart rate during the period from initia-
tion of the treatment to the return of the hydrocarbon curve to
80% of its maximum; and
c. maximum heart rate during the interval from 80% maximum to 15
seconds prior to the next treatment.
From these five measurements, three variables were computed for
analysis as follows:
(1) the maximum IHR during the treatment period minus the
maximum IHR during the control period
(2) the minimum IHR during the 80% stimulus concentration
period minus the minimum IHR during the control period.
(This should be negative.)
(3) the maximum IHR after the stimulus minus the maximum IHR
during the control.
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2. Respiration Rate
An analogous set of measurements was taken from the integrated
respiration curve and the differences computed.
a. the maximum interval between inspirations during the 15-second
control period was subtracted from the maximum interval between
inspirations in the treatment. The maximum interval between
inspirations is in actuality a measure of the slowest or minimum
respiration rate.
b. Similarly the minimum interval between inspirations during the
«
control period is substracted from the minimum interval between
inspirations during the treatment. This number reflects only
the single maximum change in respiration but might describe
sniffing.
3. Respiration Volume
In addition from the integrated respiration curve,the maximum pen
excursion or respiration volume was measured during the control period
and during the treatment and the difference computed. These six
variables were tested by analysis of variance.
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Some change in galvanic skin resistance was apparent in every treat-
ment with all subjects. However, the degree of the depression in skin
resistance varied markedly between individuals. We felt that the magnitude
of the depression might not be a true representation of the treatment
effect because of the variability among subjects. Therefore, the length
of time was measured during which the skin resistance was depressed.
This distance was compared as a ratio with the length of time of the
experiment from the initiation of the treatment to the decline in
odorant concentration to 80% of its maximum. A supplementary experiment
was carried out by measuring the time depressed after this point and
comparing it as a ratio with the total time to the end of the treatment.
We had observed a second depression in galvanic skin resistance coinciding
with the decrease in odorant concentration particularly with tetrahydro-
thiophene at the higher concentrations. Thus two additional variables
were tested for significance by analysis of variance.
Preliminary Findings
The test chamber with the remote monitoring equipment provides an
exciting opportunity for examining the effects of odorants in a variety
of presentations. That interactions of complex odorants do produce -| •
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measurable and significant changes in the autonomic response is quite
obvious in the results obtained. However, at this stage of the work it is
not clear how best to measure and record these changes nor is it evident
how these changes may reflect the hedonic importance of an odorant. It
is quite evident that concentration, duration, and odorant interact
jointly to produce significant and in some instances apparently reasonable
effects.
A major effect consistently observed in both heart rate and respira-
tion is an effect of the duration of the stimulus. Unfortunately, it may
well be that this is an artifact introduced by the definition of the
measurement to be made. Particularly, in the long (120-second) treatments, the
15-second control interval is substantially shorter than the treatment
interval and no correction has been made for this bias in the present
data.
1. Oral response
The recognition (or detection) of odors in the test chamber was
indicated by a "no" or "yes" (0 or 1) response for the treatment. Often
the subjects used simple descriptions which could be related to the order
of presentation. As would be expected, the main effect was from concentration
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with 99% confidence. A second effect due to odorant was evident with
95% confidence. The frequency curve (or curves) obtained by plotting
detection versus concentration is a typical dose-response curve segment.
Surprisingly, duration had no effect nor were any significant interactions
noted.
2. Physiological Response
There are three variables tabulated concerning the instantaneous
heart rate each of which represents a treatment response minus a control
response.
a. Maximum IHR during the treatment up to the time where the stimulus
concentration returns to 80% of its maximum. The change 'in the maximum
heart rate depends on the duration; there are no other effects and
no interactions. During the short (15-second) stimulus, the mean
increase in IHR was 2.4 beats per minute while with the long (120-
second) duration, the mean increase was 6.1 beats per minute +1.1
(all limits are 95% confidence).
b. Similarly with heart rate depression, the effect of duration is
significant at the 99% confidence level. However, concentration,
duration and odorant interact jointly. From the graphs of log ^ A e-p
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concentration versus beats per minute (Figure 2), the effect is
noted with the longer duration of the two lower concentrations only
with amyl acetate. Both are depressed 6 beats per minute + 2.5.
The questions arises Is there a calming or pleasant effect?
c. In addition to measuring the maximum heart rate during the
treatment, the maximum increase in heart rate after the 80% maximum
concentration was measured. Here concentration had a significant
effect (95% confidence), but concentration, duration, and
odorant interact jointly. As indicated in the graphs (Figure 3)
the short duration with tetrahydrothiophene shows the largest
effect even at the intermediate level producing an elevation of
5 beats per minutes + 2.55 (95% confidence).
d. In considering respiration the minimum rate (i.e., longest
time between breaths) might be indicative of "breath holding".
Again, the main effect is found with duration. During the short
stimulus, the interval is 0.8 seconds longer than the control while
with the long duration the breath interval is 2.6 seconds +0.6 seconds
longer than the control. This could be breath holding but may be
an artifact. There is also a significant effect of odorant with the
114 Arthur DUttldnc
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interval for amyl acetate being 2.2 seconds longer than the control
period while that for tetrahydrothiphene is only 1 second +0.6
longer (95% confidence). One would expect the reverse to be true
if this represents an avoidance reaction.
e. The shortest interval between inspirations was taken to indicate
"sniffing" and one might postulate that the greatest difference
would be observed at the lowest concentrations. The duration
effect was found to be the main factor, and was significant at the
99% level. The largest decrease in the breath interval was observed
with the long duration with a value of -1.2 seconds +0.23 while the
decrease with the short treatment was -0.5 seconds as compared with
the control interval.
Of possibly more interest is the interaction of concentration and
odorant apart from the effect of duration. As plotted in the
graph (Figure 4), the minimum value for amyl acetate (-1.2 seconds)
occurs at the lowest concentration—possibly sniffing for detection.
However, the greatest change with tetrahydrothiophene (-1.4 seconds)
occurs with the intermediate concentration. One would like to relate
this to sniffing in some type of alarm reaction.
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f. Respiration volume both maximum and minimum was significantly
different only as an effect of the duration of the stimulus.
In both instances, the greatest change was observed with the longer
duration. Until the possible interference of an artifact is corrected,
this data, although it does show some changes, does not appear to be
very informative.
g. Galvanic skin resistance, both hypothetically and from the litera-
ture reports, should be the most interesting and responsive measure.
Indeed, there does not appear to be any treatment or subject who does
not show some response according to the measures applied in the test.
One may easily postulate that an early indication of unrest could
well be detected in palmar sweating. Since this data is recorded
as a ratio of the duration of reduced resistance as compared with
the duration of the experiment up to the time of the return of the
concentration to 80% of the maximum concentration, the artifact of
time is not present. The only significant effect is the interaction
of concentration, duration, and odorant. Examining the data presented
in the graph (Figure 5), it would appear that there is a general
rise between the intermediate and the high concentrations. The
Arthur DLittldnc
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apparent difference between the means for the two durations of
amyl acetate is probably not significant. The primary interaction
is indicated in the data for tetrahydrothiophene where the maximum
change occurs with the intermediate concentration and the long
duration, but occurs with the maximum concentration for the short
duration exposure. One can rationalize that the intermediate
concentration and long exposure to tetrahydrothiophene allows memory
to associate the odor with gas leaks and fire, producing some alarm
reaction. Whatever the rationale, influence of interactions on the
response is of considerable interest and worthy of further exploration.
The difference in the response to amylacetate as compared with
tetrahydrothiophene is the effect which was sought in the program's
design.
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Figure 1
ODORANT RECOGNITION-ORAL RESPONSE
-1
-2
co
4J
cd
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Figure 3
MEAN MAXIMUM HEART RATE '
(After 80% Maximum Concentration)
28
4
CO
4J
rt
cu
pq
120 sec
15 sec.
15 sec.
Concentration, Duration
and Odorant
Interact Jointly
120 sec.
+2.55
012 012
Log Concentration Log Concentration
Amyl Acetate Thiophan
Log Concentration
0 1 2
I , ,
o
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Figure 5
GALVANIC SKIN RESISTANCE
(During 80% Maximum Concentration)
Concentration, Duration and Odorant
Interacting Jointly
1.4
1.2-
1.0
.8-
.6
.2'
15 sec
• 120 sec.
120
012
Log Concentration
Amyl Acetate
All means +0.44
15 sec.
0 1
Log Concentration
Thiophan
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Erland Jonsson:
On annoyance reactions observed within human populations
In several countries survey investigations have been made to study how
people perceive and react to bad smelling air pollutants. The aim
of these investigations has in most cases been to get information
about the seriousness of the smell nuisance problem; if the exposure
can be regarded as so strong that corrective action is called for.
With one exception - the Eureka-study (1) - no studies have compared
quantitative odor exposure data to community reaction data. However,
there are a few studies where community reactions in areas with as-
sumed different exposures to the sources of the odors (2, 3, 4, 5).
In surveys made to get data on the effects of offensive odors exposing
human populations different reactions have been studied. Most of those
reactions have been annoyance reactions, that usually means that the
exposure has not been a toxic one. An annoyance reaction to odorants
was at the Third Karolinska Institute Symposium on Environmental
Health (6) defined as the extent to which people report being bothered,
disturbed or irritated. It is always an unfavorable reaction of which
the subject is aware.
Reactions studied in different odor surveys
In most surveys one or more of the following five kinds of reaction to
offensive smells have been studied:
- Reports of interference with the everyday activities of the exposed
individuals,
- Reports of feelings of annoyance caused by offensive smell,
- Reports of physical symptoms of physiological changes,
91
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- Reports of actual complaints to an authority,
- Reports of various forms of direct individual action to modify the
environment other than through complaints.
Concerning the first factor the surveys have shown that the following
interferences are reported:
- with relaxation, rest and sleep,
- with entertainment of friends and relatives.'
These interferences cause feelings of annoyance, which was the second
of the dependent variables. This variable may be defined as the extent
to which people report a dislike to being bothered, disturbed or
irritated by the exposure.
Reports of physical symptoms - the third variable - appear only to a
relatively small extent. Questions about the existence of nausea,
vertigo, headache, breathing difficulties etc.are, however, as a rule
included in the questionnaires used.
Experience in Sweden suggests that only a very small percentage of the
population ever take any action with respect to the annoyance with
smells in terms of making this known to the authorities. For this
reason readiness to complain - the third of the mentioned kinds of
reactions - has been defined as the willingness to:
- visit an official,
- assist in the organisation of community action groups for abatement
of the smell,
- write or telephone to an official,
92
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- attend a meeting,
- sign a petition.
The willingness is defined by reports of the following reactions:
- ever having felt like complaining,
- actually having complained,
- being very likely to complain, pe.rhaps being likely to complain.
but not sure, or probably not being likely to compla.tn.
Concerning the last of the dependent variables - reports of various
forms of direct individual action other than complaining - the following
forms of direct individual action maty, be noted:
- installation of air conditioning so that windows can be closed,
- moving out of the area,
- shutting of windows,
- increased drug consumption.
Variations in reactions in a population that are not caused by
variations in the exposure
In several investigations differences in annoyance reactions have
been established between different categories of interviewees, separated
by demographic variables such as sex, age, civil status, occupation
etc. and by individual attitudes towards and dependence on the pollu-
tion source (6). These "irrelevant" factors make it difficult to
establish an unequivocal correlation between dose and response. It
will seem reasonable to ass.ume that the risk of influence on the
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reactionsjfrom "irrelevant" factors is least when the exposition is
very strong or very weak, respectively. Under all circumstances, the
:
population in which correlations between exposition and reaction -
if any - have been found, must be minutely defined.
f
Results of some investigations of annoyance reactions caused by offen-
sive smells
Information to what extent the odor problem exists in industrialised
communities is very incomplete. However, in 1964 an investigation
was made in Sweden using a sample of about 2000 persons, representa-
tive for the country. The purpose was to throw light on the problem
to what extent people were bothered by noise and air pollution. In
the investigation 13% reported bother from evil smell in the ambient
air (2).
Studies concerning bad smell from sulphate cellulose industries have
been made on a number of occasions. Among these, an interview study
covering about 400 persons selected at random from the population
living in the vicinity of (within 20 km of) a sulphate cellulose factory
was carried out at Monsteras in Sweden in 1959 (3). The main purpose
of the investigation was to study the inconvenience caused by air
pollution from the factory.
"The sulphate smell" bothered 36% of those interviewed, and one-third
of those bothered described their discomfort as severe. Despite the
complaints only 5% considered it disadvantageous that the factory was
located in the area. Comparisons between different parts of the area
investigated indicated the existence of a correlation between the
position of the interviewee's residence in relation to the factory
and the comparative incidence of persons bothered.
The investigation showed that certain groups of people were more dis-
comforted than others. Women were more bothered than men and younger
more than older. It was also evident that persons bothered by the
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sulphate odour complained to a greater extent of the odour from a
sulphate cellulose factory in the area investigated than those not
bothered by the sulphate odour.
A study of the same kind as that at Monsteras was made at Morrum,
Sweden, in 1963. It was an unmasked interview survey of annoyance by
offensive smells, made among a population in the vicinity of a recently
opened sulphate cellulose factory. A relatively large proportion of
the population had signed a petition to the public health authority
complaining of the offensive smell from this factory. The material
comprises about 400 persons selected at random with those having
signed the petition represented to a disproportionate extent (4).
Of the population in the area investigated, 10-15% suffered major
annoyance from the factory while the corresponding figure for those
living in the immediate vicinity of the factory was just under 20%.
It should be noted, however, that the purpose of the investigation was
not masked, so the degree of annoyance found is probably rather too
high.
Among those having signed the petition complaining of the existing
conditions, 47% reported that they had not experienced any annoyance
from the flue gases at the time of the investigation. Only 31% re-
ported major annoyance. On the other hand, almost 50% considered the
smell to be much the same as when they had signed the petition. The
petition must accordingly be rejected as a reliable measure of the
extent of the annoyance.
The results also show that the annoyance derives from factors other
than the exposure to the factory. Thus, annoyance is reported more
frequently among those with previous respiratory and cardio-vascular
diseases, with a propensity to neurosis, sensitivity to aircraft noise,
propensity to displeasure with other factors of community life and no
connection with the factory.
95 127
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Two investigations made on similar lines as those of Monsteras and
Morrum were undertaken at Clarkston, Washington (5) in 1965, and at
Eureka, California in 1969 (1). The purpose of the latter investigation
was to relate quantitative data describing exposure to quantitative
data describing community reactions. The American investigations
establish about the same bother frequencies as the Swedish.
As regards oil refineries data are available only from Swedish investi-
gations.
In connexion with the planning of oil refineries, the population around
already existing plants in Denmark, Norway and Sweden were interviewed
by persons using idiomatically identical questionnaires, in 1965 and
1968 (7).
The results show that only moderate annoyance reactions were present
around modern refineries. The oil refinery disturbance factors were
mainly considered less bothering than normal background disturbing
factors such as traffic noise.
Summarising comments
The effects of offensive odours on the exposed population dealt with in
this paper and which have been studied at the investigations under reference,
are as a rule based only on the exposed individual's experience of
conditions. This fact reduces the possibilities to establish objective
data about reactions of interest. It is therefore desirable that very
soon light is thrown on the problem which physiological reactions
are connected to the annoyance reactions.
The empirical investigations accounted for show that the odor problem
concerns relatively many human beings. Particularly near sulphate
cellulose factories a large proportion of the population is bothered.
The investigation results have, however, been of limited value for
establishing air quality criteria as the reactions studied have not
96
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been related to the exposure conditions. Later studies, e.g. the
Eureka investigation,indicate, however, that it should be possible to
relate quantitative response data to quantitative exposure data.
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References:
1. Jonsson, E., Deane, M. and Sanders, G.: Community reactions to
odors from pulp mills - A pilot study in Eureka, California,
Paper presented at the Third Karolinksa Institute Symposium on
Environmental Health, Stockholm, June 1970, (Unpublished).
2. Jonsson, E. and Sorensen, S.: Forekomsten av bullerstorningar i
samhallet - Tva enkatundersokningar -. Nord. Hyg. Tidskrift,
Vol. XLVII, 1967, 21-34.
3. Friberg, L., Jonsson, E. and Cederlof, R.: Studier over
sanitara olagenheter av rokgaser fran en sulfatcellulosafabrik
(I). Nord. Hyg. Tidskrift, Vol. XLI, 1960, 41-49.
4. Cederlof, R., Friberg, L., Jonsson, E., Kaif, L. and Lindvall, T.:
Studies of annoyance connected with offensive smell from a sulphate-
cellulose factory. Nord. Hyg. Tidskrift, Vol. XLV, 1964, 39-48.
5. Nahum Z.Medalia: Community Perception of Air Quality: An Opinion
Survey in Clarkston, Washington (Cincinnati, Ohio: U.S. Public
Health Service, 1965).
6. Jonsson, E.: Annoyance Reactions to External Environmental Factors
in Different Sociological Groups. Acta Sociologica, vol 7 -
fasc. 4, Copenhagen 1964.
7. Rylander, R. and Sorensen, S.: Omgivningshygieniska konsekvenser
av ett planerat oljeraffinaderi pa Lysehalvon. National Institute
of Public Health, March 1969.
13O
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Draft of Working Paper
Studies of Public Opinion of a Traffic Odor
Presented at
April 26-30, 1971 Odor Symposium - Cambridge, Massachusetts
Presented by
Karl J. Springer
Manager, Vehicle Emissions Research Laboratory
Southwest Research Institute
San Antonio, Texas
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Introduction
The control of an air pollutant such as malodorous traffic odor depends
on three "musts. " First there must be a way to measure and express the
odor in simple, understandable and repeatable terms. Second, there must
be a way to effect a reduction in the odor that is feasible economically.
Finally, the reduction in odor must do something positive as far as the
public is concerned. Work has been in progress by government, industry,
and independent laboratories on all facets of these three"musts. " The
Vehicle Emissions Research Laboratory at Southwest Research Institute
has been privileged to work on all three at the same time under the
guidance of the National Air Pollution Control Administration (now the
Air Pollution Control Office of the Environmental Protection Agency).
At last year's meeting in Stockholm, the working paper based on work
done at Southwest Research was concerned with correlation of instrumental
measurements with sensory panel ratings. In an attempt to extend the use-
fulness of the human panel, several components in diesel exhaust, some
odorous and some not, were related to sensory ratings. The odor ratings
were from a trained panel of ten persons using the PHS quality/intensity
kit, better known as the Turk kit, shown in Figure 1, as the primary
reference. This subjective quantitative-qualitative method has been well
described in the literature and has formed the basis for most government -
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2.
sponsored diesel odor research for the past five years. The standards
are a "diesel composite" or "D" in intensities 1 through 12, a "burnt-
smoky" or "B" in intensities 1 through 4, an "oily" or "O" in intensities
1 through 4, an "aromatic-aldehydic" or "A" in intensities 1 through
4, and a "pungent" or "P" in intensities 1 through 4. The "D" series
describes diesel odors most comprehensively in that it is composed of the
four sub-odors or odor qualities. The quality/intensity kit is designed
so that the twelve odor intensity steps of the "D" series ("D"-l is weakest,
"D"-12 strongest) are perceived linearly by the observer. Concentration
of odorant in each "D" bottle is twice that in the next weaker one. The
"D" is the primary intensity standard, and the others are used to describe
the quality of the odor.
This working paper describes a pioneering effort to acquire public
opinion of diesel exhaust in terms of the Turk kit panel ratings of the
same odor. The intent of this effort is to relate and close the loop between
technology, measurement and response. In doing so, additional insight
is gained that can be used in consideration of control effectiveness, pre-
paration of standards and measurement methodology. For purposes of
this description, the paper is divided into two sections, dealing first
with the dose and then with the response.
The Dose
To adequately describe the dose, the method of presentation and
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3.
the means by which the participants were asked to express their opinion
is just as important as what the odor was. Several approaches were con-
sidered in the effort to determine public opinion of diesel exhaust odor.
The idea of "canning" diesel odors was attractive because it allowed
use of a national probability sample, but it could not be used because
diesel odors cannot be preserved. Another idea involved use of the Turk
kit for sampling by the public, but this idea was rejected because the odor
standards do not smell enough like diesel exhaust. The most plausible
idea, and the one finally adopted, was to construct a mobile laboratory
for odor evaluation which would incorporate a "live" odor source, that
is, an operating diesel engine. This method presents odors which are
realistic and which have not had time to change, but it also introduces
mechanical complexity and less precise participant sampling measures.
The design of the mobile odor evaluation laboratory resembles very
closely that of the stationary odor measurement room in the SwRI
Vehicle Emissions Research Laboratory. Figure 2 is a schematic of
the mobile laboratory showing compartment boundaries and location of
major items of equipment. The trailer was divided into the front
mechanical compartment, the central odor presentation room, and the
rear engine/generator compartment. The basic idea was to sample con-
tinuously raw exhaust from the engine stack and mix this sample with
103
135
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4.
diluent air in ratios from about 50:1 up to several thousand to one.
The diluent air was passed through a prefilter, a particle filter,
a charcoal filter, and more recently a scrubber-humidifier before being
mixed with small amounts of diesel exhaust to help assure consistency
in odor levels. All portions of the odor presentation system which
come into direct contact with odor samples before they reach the parti-
cipants are made of relatively inert materials, usually either Teflon*
or stainless steel.
Early in this research effort, it was agreed that odors presented to
participants should simulate those found in the exhaust of typical muni-
cipal buses, since these urban odors seemed to be of most concern to
the public. Since over 80% of municipal buses are powered by six-
cylinder two-stroke diesel engines, it was decided to use a multicylinder
two-stroke diesel operating at moderate speed and load as the odor source.
The exhaust odor from two engines, a Detroit Diesel 3-53 and a 3-71,
were evaluated by the odor panel. Followinga number of evaluations at
various speeds and loads, the powerplant/odor source chosen for the
mobile laboratory was a 3-71 "E" series, two-valve, two-stroke engine
driving a 35-kilowatt generator at 1200 rpm.
The environmental control systems are located primarily in the front
Reg. Trademark, E.I. duPont de Nemours & Co.
104
136
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5.
mechanical compartment of the mobile laboratory. The criteria for the
odor room air were a temperature of 75°F, relative humidity of 50%,
odor background so low as to be undetectable, and a static pressure in
the room slightly above atmospheric to prevent odors from leaking into
the room. All makeup and recycle air passed through a prefilter, a
particulate filter, and a charcoal filter before entering the odor pre-
sentation room.
The interior of the mobile laboratory is finished with colorful,
attractive materials, as a part of the total effort to make the participants
comfortable and at ease. Figure 3 is a view of the odor evaluation room
looking toward the front of the facility. Figure 4 is another view of the
odor evaluation room, this time looking toward the rear of the facility.
Figure 5 shows the typical position of a participant preparing to evaluate
an odor. Figure 6 is a view of the Sniffmobile from the right rear, and
Figure 7 shows the left side. Figure 8 shows the mobile laboratory on-
site in San Antonio, with the patio umbrella and chairs which were used
as a "staging" or "preinterview" area by the survey crew. These items
were brightly colored and formed a nice place to talk to passers-by and
keep up with data tabulation.
The Response
The use of a questionnaire to aid in eliciting and recording public
137
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6.
opinion on diesel exhaust odor was judged to be preferable to the alter-
native of verbal personal interviews. This decision was reached because
it is more economical to have group interviews using a self-administered
questionnaire than to have one-to-one verbal interviews, because a
questionnaire can "ask" questions of each participant in an identical
manner, and because structured responses were considered desirable.
Structured responses lend themselves to analysis more readily than res-
ponses which are made up of the participants' comments about the odors
given in their own words. Proper questionnaire design can do much toward
reducing participant bias by using neutral phrasing in instructions and, in
the case of a multiple-choice questionnaire, by allowing each person to
choose answers from the same lists. National Opinion Research Center,
subcontractor to SwRI on this research program, has a well-known
capability in the areas of public opinion survey work and questionnaire
development. The expertise of the NORC staff was utilized throughout
the questionnaire development and the field survey.
In general terms, the major objectives of the questionnaire were to
obtain informed consent, to obtain personal information, to obtain an un-
biased opinion of a set of diesel exhaust odors, and to obtain certain
supplementary information from each respondent which might aid in
interpreting his or her response to the odors. In addition, it was decided
106
138'
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7.
that the questionnaire should be as simple and brief as possible because
persons of all educational backgrounds were expected to participate in
the survey. Words which might bias the participants, such as "diesel, "
"bus, " "truck, " and "air pollution" were intentionally avoided, both on the
questionnaire and in verbal contact with the public at the test sites. A
copy of the questionnaire used in the 1969 survey is included for reference
as the next page of this paper. The front of the sheet contains personal
information questions, and the back is used for odor testing. The consent
of the people to participate in the survey was obtained after informing them
of what they would be required to do. If anyone expressed reservations,
that person was asked to exclude himself or herself from the group. The
multiple choice questions and the theory behind their use came directly
from NOR C, whose experience showed that people are much less likely
to balk at answering personal questions if they do not have to be too specific.
By all standards, the most difficult portion of the questionnaire to
design was that section which deals with response of the general public
to a series of diesel exhaust odors. The idea of using something other
than descriptive words on a scale came from an informal discussion with
Dr. Amos Turk some 2 years before this project was begun. He related
that a food company had once determined public opinion of a food item
served in a cafeteria by using a questionnaire having five human faces
107
139
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1969 SURVEY QUESTIONNAIRE MULTIPLE ODOR TEST
8.
No.
PUBLIC OPINION ODOR TESTING SURVEY
This survey is to find out your opinion of a common odor typical of U.S. cities. You will be asked to sniff
the odor three times. The odor has no known health hazard and your participation is completely voluntary.
For each item, circle the one code number which fits you best. All answers are confidential You will
never be identified.
YOUR SEX:
Male .
Female
YOUR AGE:
15-24 1
25-44 2
45-64 3
65 or more 4
YOUR HEALTH, IN GENERAL:
Excellent 1
Good 2
Fair 3
Poor 4
YOUR SCHOOLING:
8 yrs. or less 1
Some High School 2
Completed H.S 3
Attended College 4
YOUR USUAL ACTIVITY:
Employed 1
Housewife 2
Student 3
Retired 4
Other 5
IF YOU CIRCLED EMPLOYED, WHAT
TYPE OF WORK?
Professional, business
owner or manager 1
Clerical, office or sales 2
Skilled or semi-skilled
wage earner 3
Other 4
FAMILY INCOME LAST YEAR:
Under $4,000 1
4,000-6,999 2
7,000-11,999 3
12,000 or more 4
DO YOU SMOKE?
Regularly . .
Occasionally.
Never . . . .
109
-------
Next, a series of different odor levels will be presented. Please check the appropriate box under the figure which best expresses your feeling.
Pleasant
Neutral
Unpleasant
Very
Unpleasant
Unbearable
Test
D
Testa
D
D
Test 3
D
Are any of these odors so bad that someone
should take steps to reduce them?
How often do you experience odors like these?
No—None of them
Yes-Test 1
Yes-Test 2
Yes-Test 3
Very often
Fairly often
Occasionally
Never . . .
142
no
-------
9.
whose expressions ranged from pleasure to displeasure. The proposal
of this research project suggested the use of a similar method to eli-
minate bias due to inconcistency in word usage among the general populace.
Matching one's feelings about something with one of several representative
facial expressions is perhaps even more accurate than free-form verbal
description of those feelings, and it is certain that the structured responses
generated by the former method lend themselves more readily to quanitia-
tive interpretation.
As the idea of cartoon faces evolved, a conference with NOJRC was
held out of which arose a suggestion to add bodily action to the faces.
This idea allowed a deeper interpretation of responses to odors, e. g. ,
the 5th cartoon character is not only displeased with the odor he perceives,
but he is also taking steps to physically remove himself from the odor
source. Many versions of these cartoons were tried in an effort to space
them equally along a scale of objectionability, that is, to make the step
changes in reaction depicted by the cartoons equal. A descriptive word
was added under each cartoon figure only after the characters were in
essentially final form.
The last two questions on the back of the questionnaire were added
with very limited applications in mind. The question dealing with action
on odor abatement was intended for use with a person's responses to
111
143
-------
10.
odors to examine that person's sense of values regarding action on odors.
Pre-survey validation of the survey questionnaire was accomplished in
two separate steps. Step 1 determined how a sample of people related
the five cartoon characters to the concept of objectionability. Step 2
involved the matching of descriptive words with the established cartoon
characters.
NORC personnel compiled population distributions for each of the
five cities to be sampled according to sex, age, education, and income.
These distributions were based on I960 census figures and were restricted
to areas within city limits. Upon examination of the distributions, a
meeting was held in the city to be sampled with SwRI personnel, the Pro-
ject Officer, and local air pollution control personnel in attendance. Out
of this meeting came the suggestions of local air pollution control people
as to areas which should be searched for test sites, and the candidate sites
were subsequently evaluated for presence of required foot traffic, adequate
space for mobile laboratory access and parking, and presence of desired
characteristics of the population. During the conduct of the survey itself,
people were approached by members of the survey crew and asked to
participate in the survey. Quotas were based on a sample size of 500 per-
sons per city, but 600 to 700 persons were routinely surveyed before all
the quotas had been filled.
112
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11.
Calibration of the Sniffmobile required that sample flow to each parti-
cipant be balanced and equalized and that the concentrations in each cone
be identical. Calibration also meant that the trained odor panel had to
define the relationship between sampling rate and odor level before and
after operation at each survey site. Figures 9-13 show the "D", "B",
"O", "A", and "P" panel ratings during the May-to-October 1969 testing
period. The essentially flat curves indicate the ability of the trained panel
to respond almost identically in terms of the Turk kit to the same odor at
infrequent intervals. This is the first known instance of such an experi-
ment with the bottle rating method.
Results - 1969 Survey
Over 3000 quota-sampled individuals in five cities, three or four sites
per city, were included in the survey of 1969; The cities were San Antonio,
Chicago, St. Louis, Philadelphia, and Los Angeles. San Antonio and Los
Angeles represent two extremes of air pollution and public awareness,
while the other three seemed to be somewhere between in this regard. To
discuss the 1969 survey, let's consider first the most important result, the
cartoon responses for the three odor tests of "D"-2 (Test 1), "D"-4 (Test 2)
and "D"-6 (Test 3), in turn. Figure 14 is a frequency polygon for the three
tests, with a mean response of 2. 44 (Test 1), 3. 37 (Test 2), and 3. 96 (Test
3). The numerical result is based on assigning the cartoons a number
113 '
-------
12.
from 1 to 5, 1 being pleasant and 5 being most objectionable. Figure 15
shows the range of cartoon responses in terms of the "D", "B", "O",
"A", and "P" ratings. The participants considered the stronger odors more
objectionable than weak ones and, this is shown by the smooth, easily de-
fined curves. One question on the back of the questionnaire asked, "Are
any of the odors so bad that someone should take steps to reduce them?"
In answer to this question, the survey results looked like the top curve in
Figure 16. This result, not unexpected, agrees somewhat with the inde-
pendent calibration of the cartoon on a 0 "pleasant" to 100 "most objection-
able" scale.
At this point, we have a good indication of people's reaction to a live,
realistic traffic odor and some insight on its relative objectionability.
Of course, we have also discovered the variation by city and site on odor
response, effect of sex, age, health, occupation, employment, income,
and smoking. Some variation in odor response from city to city can be
found which remains unexplained by consideration of variation in socio-
economic characteristics of the several populations or other quantitative
factors. In particular, San Antonio participants seemed to find the ex-
haust odors less objectionable and Los Angeles participants seemed to find
them more objectionable than did the Chicago, St. Louis, and Philadelphia
participants, whose responses were close to the average. Participants
and passers-by in Los Angeles were very quick to associate the survey
114
146'
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13.
with air pollution, but those in San Antonio had little to say about pollution,
and again the participants in the other three cities fell between the ex-
tremes. San Antonio has the cleanest air of the cities surveyed, and Los
Angeles is at least the best known of the five cities for polluted air if it
is not in fact most heavily polluted. It is quite possible that a relationship
exists between response to diesel exhaust odors (or, for that matter,
almost any pollution-related subject) and public awareness of and attitudes
toward air pollution, both of which depend on the severity of the local
pollution problem and the type and amount of publicity given it.
The effects of education, employment, and income, commonly known
as "socioeconomic" categories on odor responses were quite similar.
The more educated, the more highly skilled, and the more affluent the
participant, the more objectionable he found the odor. Older people
(over 65) found the odor less objectionable, as did those who judged them-
selves in poor health. These two factors seemed to be related and tend
to support the idea of decreased sensory perception with age.
1970 Survey
Public opinion of the "D-2" odor level (Test 1) was adequately de-
fined by the 1969 survey. Public opinion of the "D-4" and "D-6" levels
(Tests 2 and 3, respectively) could not be taken as absolute but had to
be used with the full knowledge that each participant's response might
115
147
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14.
have been influenced somewhat by his prior exposure to one or two other
odors.
With this in mind, an additional 2100 quota-sampled individuals were
included in the 1970 survey. The main objective was to elicit responses
from singly presented odors and to inquire further about the objection-
ability of these odors. Some slight changes were made to the front side
of the questionnaire, shown on the next page, but the cartoon method
of rating was retained, and more and different questions were employed
in an attempt to gauge the public objectionability of the odors. Improve-
ments in the Sniffmobile included installation of additional diluent air
purification equipment in order to control himidity and assist in approaching
a "D-O" odor level. A nominal "D-2", 3, 4, 5, and 6 were presented,
each at a separate site, and the results are plotted in Figure 17. The
almost linear response is similar to the 1969 survey except the results
above about "D-4" are lower, indicating a possible "history" effect during
the 1969 survey. Below about "D-4", the 1969 results were lower than
1970. This may be attributed to the completely different public attitude
about air pollution promulgated by public officials and the media since
January 1970. This plot also illustrates that the public does not center its
responses given an adequate means of expression such as the cartoon scale.
Figure 18 is a plot of the fraction of participants who perceived an
116
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15.
Form Approved
•Budget Bureau No. 85-S69017
1970 SURVEY QUESTIONNAIRE-SINGLY PRESENTED ODORS
No.
PUBLIC OPINION ODOR TESTING SURVEY
IMPORTANT! PLEASE READ.
This survey is to find out your opinion of a common odor typical of U.S. cities. The odor has no known
health hazard and your participation is completely voluntary.
DIRECTIONS
FOR EACH QUESTION, CHECK THE BOX BESIDE THE ONE ANSWER WHICH FITS YOU BEST.
ALL ANSWERS ARE CONFIDENTIAL. YOU WILL NEVER BE IDENTIFIED.
1. YOUR SEX:
Male . .
Female .
4.
3.
D
D
YOUR AGE:
15-24
25-34 ....
35-14
45-64
65 or over . . . .
p
D
. . . n
. . . .D
n
YOUR SCHOOLING:
8 yrs. or less
Some High School I I
Completed H.S LJ
Some College ....... I I
Completed 4 yrs. College . . . I I
5.
6.
YOUR USUAL ACTIVITY:
Employed
Housewife
Student
Retired
Other
IF YOU CIRCLED EMPLOYED,
WHAT TYPE OF WORK?
Professional, business . .
owner or manager
Clerical, office or sales . .
Skilled or semi-skilled . .
D
D
D
n
D
wage earner
Other . . .
n
n
FAMILY INCOME LAST YEAR:
Under $4,000 CD
4,000-6,999
7,000-9,999
10,000-14.999 ....
15,000 or more
n
n
n
n
NAPCA Form No.
HQ 27 (4/69)
117
149
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Next, an odor will be presented.
1. Did you smell anything?
Yes
No
IF YES, CHECK THE BOX UNDER THE FIGURfi WHICH BEST EXPRESSES YOUR FEELING,
THEN ANSWER QUESTIONS 2, 3, AND 4.
Pleasant
Neutral
Unpleasant
Very
Unpleasant
Unbearable
2. How often have you experienced this odor?
Very Often
Fairly Often .
Occasionally.
Never
If you have experienced the odor, where?
Indoors
Outdoors
Both Indoors and Outdoors .
If you were to experience an odor just
like this outdoors, would you find it
objectionable?
Yes
No
4. If an odor just like this occurred out-
doors, should someone take steps to
reduce it?
Yes
No
150
118
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16.
odor and found the odor objectionable according to question no. 3 asked
after the odor test, "If you were to experience an odor just like this
outdoors, would you find it objectionable?" In addition, the fraction of
respondents who perceived an odor is also plotted. These results appear
as expected at the noticeable odor levels of "D-2" to "D-6" and improve
the confidence in the 1969 survey data.
As a separate item, an attempt was made to ascertain public opinion
of diluent air devoid of diesel exhaust or diesel odor. After substantial
system clean-up and purge, a dusty residual odor remained, not diesel
nor fuel, that was slightly noticeable. Though the participants, a group
of over 500, were handled the same way as in higher level tests, a large
percentage (60%) perceived an odor and a higher percentage than expected
(about 50%) of those who said they perceived an odor, termed it objection-
able.
Our analysis of the 1970 survey is incomplete at this writing, but
several points may help to explain the final test results. First, the pre-
sentation of such an extremely low level odor actually confused a number
of the participants. They were originally asked to sniff an odor and then
a sample containly nearly no odor was presented. It should be noted that
at odor levels below "D-2", the trained odor panel agreement begins to
scatter substantially. "D-2" is a faint odor and the difference between
119
151-
-------
17.
"D-l" and "D-2" is discernible mainly to the trained panelist. It
appears that the experiments at the near zero odor level are really incon-
clusive and that the sniffmobile test methodology is not suited for ac-
quiring opinion to "no-odors. " In fact, this "no-odor" test seems to ask
a completely different question of the research, the answer to which is
certainly beyond the scope of the current effort.
In summary, ratings of dies el exhaust odors by the public can be
related to the intensities and qualities which those odors are judged to
possess by a trained odor evaluation panel, according to the standards
of the Public Health Service Quality/Intensity Kit. This result makes
possible the evaluation of the effectiveness of odor control methods in
terms of the approximate extent to which their use would reduce ad-
verse response to dies el exhaust odor.
120
152
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r
Dilution Air
Fume Removal
Dilution Air
Heater
r
Fume Removal
Exh-'ist
Exhaust
Diluted Exhaust
Engine/
Generator
Compartment
QOOO OOO OOO
^^— Stools
-------
01
S3
S3
May 9
-0-
-©-
Test 3-Signal Pressure • 18 in. Hg
Test 2-Signal Pressure - 10 in. Hg
-e- e
Test 1-Signal Pressure - 2 in. Hg
1
I
I
June 27 July 24 August 29 October?. 1969
Date of Calibration
FIGURE 9. INITIAL, INTERIM, AND FINAL, SNIFFMOBILE CALIBRATIONS BY SwRI ODOR PANEL - "D" RATINGS
-------
U)
01
c
s
a: 1
m
•0-
-0-
-0-
-0-
©
Test3
Test 2
Testl
- -- ©
1
1
1
I
5/9/69 6/27/69 7/24/69 8/29/69 10/7/69
Date of Calibration
Figure 10. Initial, Interim, and Final
Sniffmobile calibrations by SwRI
Odor Panel - "B" Ratings
2r
S,
i
-©-
I
Testl
—©
I
5/9/69 6/27/69 7/24/69 8/29/69 10/7/69
Date of Calibration
Figure 11. Initial, Interim, and Final
Sniffmobile calibrations by SwRI
Odor Panel - "O" Ratings
21-
8,
*^
(0 ,
cc 1
Test3
0-
-©-
Test 2
—O
Testl
A
5/9/69 6/27/69 7/24/69 8/29/69 10/7/69
Date of Calibration
Figure 13. Initial, Interium, and Final
Sniffmobile calibrations by SwRI
Odor Panel - "P" Ratings
-------
Testl
ts)
1400
1200
Test 2
Test3
Questionnaire Cartoons
FIGURE 14. FREQUENCY POLYGONS FOR CHOICE OF CARTOONS IN THE THREE ODOR TESTS
-------
Ul
2
B 1
o
1 i
m
Average Odor Test Response
FIGURE 15. RANGE OF RESPONSES TO ODORS FROM TEST SITE TO TEST SITE RELATED TO ODOR INTENSITY
AND QUALITIES
-------
100
90
80
2
M
I
70
is "8
I c
? s
I &
.* s
Ł
Ł •
40
i
•g
c 30
•s
20
10
3
w
!5
-I
o
o
J
50 I
40 o
§
oc
I
20
10
Test 3—Three
Times Test 1 Intensity
FIGURE 16. COMPARISON OF RESPONDENTS' STATED POSITIONS ON CONTROL OF
THE ODORS THEY EXPERIENCED AND THEIR OPINIONS OF THE ODORS
IN TERMS OF OBJECTIONABILITY
158 126
-------
ra
o
C/5
I 3
to
o
_
9
I
I
I
6
2 34 5
Nominal "D" Rating of Odor Presented
FIGURE 17. PUBLIC RESPONSE TO DIESEL ENGINE EXHAUST ODORS
1.0
~ 0.8
o
5
0.4
. Perceived Odor
•Found Odor Objectionable
I
_L
2.3 4 5
Nominal "D" Rating of Odor Presented
FIGURE 18. FRACTIONS OF PARTICIPANTS WHO PERCEIVED
OR OBJECTED TO ODORS
127
159
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PROPERTY VALUE DIFFERENTIALS AS A MEASURE
OF ECONOMIC COSTS DUE TO ODORS
By R. David Flesh
Copley International Corporation
For presentation to the Symposium on
Dose-Response Relationships Affecting
Human Reactions to Odorous Compounds
Cambridge, Massachusetts
April 26, 1971
-------
PROPERTY VALUE DIFFERENTIALS AS A MEASURE
OF ECONOMIC COSTS DUE TO ODORS
By R. David Flesh, Copley International Corporation
Introduction
Whenever the actions of private enterprise cause a divergence between private
and social costs, the government should intervene. This principle of welfare economics
was developed and first expressed by A. C. Pigou about 40 years ago. It is based on the
premise that an excess of social costs over private costs means that market forces alone
are insufficient to make private enterprise bear the total responsibility for its actions.
In the language of economics, such a condition is known as an external diseconomy.
It is the role of the economist, working under Pigou's principle, to measure
external diseconomies and thereby determine the extent of governmental intervention
necessary to supplement market forces. Yet, under existing knowledge, social costs
are usually difficult and often impossible to measure. Those that can be measured are
termed economic costs.
The social costs of odors remain in the identification stage. Except for one
possibility, measurements cannot be made with any degree of confidence. The single
possibility is that of property value differentials. Numerous opinion surveys of home-
owners have been conducted with the common result that odors are perceived to be a
principal effect of air pollution and that, other things equal, the effect ultimately mani-
fests itself in the form of reduced property values. This supports the underlying
hypothesis of the property value approach to the measurement of social costs, which
-1-
163
-------
maintains that such effects are capitalized negatively into the value of land and any
lasting improvements fixed thereon.
Under a present study of the social and economic impact of odors, methods
are being developed to measure property value differentials due to odors. Initially,
these methods will be applied to neighborhoods of single-family dwelling units. They
will benefit particularly from the recent work of two teams of investigators: Ronald
G. Ridker-John A. Henning and Robert J. Anderson, Jr.-Thomas D. Crocker.
The Ridker-Henning Study
Economic theory suggests that property values might be statistically explained
by regressing neighborhood, occupant, and property characteristics against the market
price of the property. The first published study to include an index of air pollution as
an independent variable was undertaken by Ridker-Henning in the St. Louis Metropolitan
o
Area. They selected census tracts to serve as neighborhoods on the assumption that
the census tracts were homogeneous with respect to the variables relevant to the study.
Both cross-sectional and time series analyses were performed.
In the cross-sectional analysis, almost 94 percent of the variation in average
single-family dwelling unit values between neighborhoods was explained by a regression
equation using 12 independent variables: a measure of air pollution, median number of
rooms (a proxy for house size), percent of all units recently built (January 1950 to
March 1960), units per square mile (a proxy for lot size), distance in time from the
central business district, accessibility to highways and major thoroughfares, school
quality, percent of workers in blue collar occupations, persons per unit, percent of
units occupied by non-whites, whether census tract was in Illinois or Missouri (a dummy
variable to account for differences in property taxes), and median family income in 1959.
-2-
-------
The variable representing air pollution was based on milligrams of sulfur trioxide per
100 square centimeters per day averaged for one year. The regression coefficient of
that variable indicated that, other things equal, average single-family dwelling unit
values would decline $245 for every increase of 0.49mg SCL/lOOcm^/day.
The time series study was confined to only one neighborhood. During 1962,
residents of a quite, middle-class neighborhood in St. Louis began to complain about
the choking gases from a plant that had just been taken over by a metal fabricating
company. The odors were said to cause nausea, headaches, and other discomforts.
In order to assess the effect of air pollution on property values apart from changes
in general market conditions, a control neighborhood similar to the affected area was
selected. A regression index of recorded property sales was computed for each neigh-
borhood and compared over a 9 year period as shown in Table I.
Table I. Regression index of property values in St. Louis, 1957-1965.
Year
1957
1958
1959
1960
1961
1962
1963
1964
1965
Regression Index
Affected
100.0
95.8
95.8
101.6
96.4
94.6
90.6
91.8
102.3
Area Control Area
100.0
94.3
105.4
109.3
101.2
97.5
99.1
106.6
107.8
P*
— •
0.75
0.01
0.03
0.40
0.50
0.04
0.001
0.30
Number
Affected Area
48
31
38
35
20
31
35
32
30
of Sales
Control Area
97
77
87
72
65
63
69
37
32
* P is the probability that the observed difference between the index values for the
affected and control areas for a given year is due to sampling error (two-tailed
test). The null hypothesis under test is that the true difference is zero.
Source: Ronald G. Ridker, Economic Costs of Air Pollution (New York: Frederick
A. Praeger, 1967).
-3-
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Ideally, the indices for the affected and control areas should not have been
significantly different prior to 1962. Beginning in 1962, however, significant differences
should have appeared to reflect the effect of air pollution. As can be seen in column P,
the ideal pattern was interrupted in 1959 and 1960 by divergences which are significant
to the 1 and 3 percent levels, respectively. In addition, the effect of air pollution does
not appear until 1963. Ridker-Henning could not find evidence to explain these unexpected
divergences and did not comment on the apparent lag of the effect until 1963.
To indicate the dollar losses that may have been caused by air pollution, Ridker-
Henning multiplied the average percentage differences in the indices for 1963, 1964, and
1965 by the average property value in the affected area for the same period. The figure
used to represent property value in the neighborhood under investigation was $12,100,
the median value of single-family dwelling units in the neighborhood found in the U. S.
Censuses of Population and Housing: 1960, St. Louis, Missouri-Illinois. Applying this
figure to the indices produced a mean property value for the three year period of $11,302.
The mean percentage differences between the affected and control areas for the same
period was 9.6 percent. Together, these figures suggest that homeowners in the affected
area suffered an average loss of $1,085 to the value of their homes. Since there were
1,068 single-family dwelling units in the affected area in 1960, the total property-value
loss was estimated at $1,158,780.
The time series analysis was based on so many assumptions, that Ridker-
Henning claimed little confidence in the results. Most disturbing was the failure of the
cardinal assumption "other things equal" by the unexplained divergences between the
affected area and control area indices in 1959 and 1960. The same cause(s), along
-4-
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with air pollution, may have been present to some extent in 1963, 1964, and 1965.
The Anderson-Crocker Study
Cross-sectional studies were more recently performed by Anderson-Crocker
in three standard metropolitan statistical areas—St. Louis, Kansas City, and Wash-
3
ington. Except for air pollution, observations on all neighborhood, occupant, and
property characteristics were taken from 1960 U.S. Censuses of Population and
Housing. The air pollution data consisted of average annual sulfation and suspended
particulates readings taken during the mid-1960's at various locations in each city by
the National Air Pollution Control Administration. Anderson-Crocker proceeded with
their analysis on the assumption that the several years difference between the socio-
economic data and the air pollution data would cause the impact of air pollution to be
somewhat understated.
Seven independent variables were used in the regression equation: the two
measures of air pollution, median family income, proportion of housing units classed
as dilapidated, proportion of housing units more than twenty years old in 1959, pro-
portion of occupied units inhabited by non-whites, and distance from the central business
district. At least 75 percent of residential value differentials were explained by these
variables in St. Louis, 80 percent in Kansas City, and 69 percent in Washington.
The equation provided figures corresponding to what Anderson-Crocker called
"marginal capitalized" property values. The highest marginal capitalized damage
figure obtained for suspended particulates was for the predominantly single-family
3
dwelling units census tracts in Washington, where the addition of 10 mg/m /day to a
relatively low concentration of suspended particulates caused an average reduction of
-5-
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$700 in the market value of owner-occupied homes. For St. Louis and Kansas City,
the comparable figures were $119 and $126, respectively. However, the average
concentrations of suspended particulates in these two cities were substantially higher
than in Washington.
The highest marginal capitalized damage obtained for sulfation was $912 for
each additional 0.1 mg SO^/100cm2/day. This figure was obtained for owner-occupied
homes in the portion of Kansas City lying in Kansas, where average concentrations of
sulfation were extremely low. hi St. Louis, where such concentrations were quite high,
the comparable figure was $158.
Over the ranges of sulfation and suspended particulates observed by Anderson-
Crocker, marginal capitalized damages and the responsiveness of damages to air
pollution appeared to decline with increases in average pollutant concentrations. That
is, total damages seemed to increase at a decreasing rate and the proportionate change
in damages relative to the proportionate change in pollution concentrations appeared to
decline with increases in average pollutant concentrations.
Preliminary Findings of the Present Study
Based on the subjective nature of odor evaluation and the types of neighborhood,
occupant, and property data available, two methods of measuring property value dif-
ferentials due to odors seem promising. Both methods are applicable when odors have
been identified—by neighborhood opinion surveys or public complaint records-- as the
principal cause of air pollution annoyance to homeowners. The first method is currently
being tested. The second is untried. It evolved from discussions with real estate ap-
praisers relative to gathering data for the first method and from experience with the
-6-
168
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use of rating scales in other fields of research.
The "Other Things Equal" Approach. This approach is virtually identical
to the Ridker-Henning time series analysis. The only difference is that the control
neighborhood must be carefully located either adjacent to the source of odors in the
affected neighborhood or adjacent to a very similar source of odors. In either case,
the control area must be upwind of any odors. The intent of this strategy is to elimi-
nate as many factors other than odors as may contribute to property value differentials.
The preliminary findings obtained from affected and control neighborhoods
adjacent to two major oil refineries in the Los Angeles Metropolitan Area indicate
that the method is a workable one. Selling prices for a sample of single-family dwell-
ing units sold in each of the neighborhoods for the years 1966, 1968, 1969, and 1970
were obtained from local boards of realtors. As shown in Table II, a divergence of
the annual averages of these selling prices began in 1969. The divergence occurred
within one year after a new, but inadequately controlled sulfur plant began operations
within the refinery complex adjacent to the affected area.
Table II. Average selling prices of single-family dwelling units in neighborhoods
adjacent to two major refineries, 1966 through 1970.
Year
1966
1967
1968
1969
1970*
Affected Neighborhood (AN)
Average
Selling Change from
Price Previous Year
$26,200 -- %
n.a.
29,300 +5.9**
29,100 -0.7
30,000 +3.0
Control Neighborhood (CN)
Average
Selling Change from
Price Previous Year
$23,300 — %
n.a.
25,700 +5.2**
27,100 +5.4
29,000 +7.0
Difference
Average
Selling
Price
$2,900
n.a.
3,600
2,000
1,000
(AN-CN)
Change from
Previous Year
" %
--
+0.7**
-6.1
-4.0
* First three quarters only.
** Average change over the previous two years.
n.a., data not available.
-7-
169
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There is no doubt that the substances released into the atmosphere by the new
sulfur plant were perceived as obnoxious odors by the residents of the affected neigh-
borhood. The annual number of odor complaints from these residents to local authorities
increased by a factor of 10 between 1968 and 1970. An opinion survey was conducted in
the area in December, 1970. Sixty-three percent of the adult residents interviewed said
they were bothered by odors in their neighborhood, considered the presence of the odors
to be a serious problem, and believed the odors originated at the refinery. Thus, if
other things remained equal during the period shown in Table II, then about $1,800 of
average property value differential in 1969 and about $3,000 of average property value
differential in 1970 would be due to the presence of odors in the affected neighborhood.
An examination of other variables must be completed, however, before these findings
can be considered conclusive.
A major drawback to the method was found to be the time required to locate
suitable neighborhoods for the study. Although several cities were visited, Los
Angeles was finally chosen because of the constancy of meteorological parameters,
especially wind direction.
The Problem Rating Scale Method. Under this approach, an average property
value differential between a neighborhood affected by odors and a similar, but relatively
odor-free neighborhood would be computed using data obtained from local boards of
realtors, the Society of Real Estate Appraisers, or the U. S. Bureau of the Census.
Of course, depending upon whether the researcher is interested in an immediate situa-
tion or long-term trends, such differentials may be computed for the current year or
for the past several years.
-8-
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Following these mechanics, a series of discussions would be held with highly
qualified real estate appraisers, who normally serve both areas. The appraisers
would be asked to identify all of the factors they believe may have contributed to the
differential. The purpose of these discussions would be to confirm the existence of
factors that typically contribute to such differentials and, more importantly, to include
other factors that are unique to the neighborhoods under investigation. In general, such
factors would arise from differences in neighborhood, occupant, and property charac-
teristics .
Adjustments of the computed differential for differences in occupant charac-
teristics may be avoided through careful selection of the control neighborhood. The
principal characteristics to match with the affected neighborhood would be median
family income. Adjustments for property characteristics may be necessary depending
upon the average age, size, and construction quality of the single-family dwelling
units in each area. Fortunately, adjustments for property characteristics usually are
not difficult to perform. Real estate appraisers are specially skilled in such work and,
therefore, would be of valuable assistance to the researcher.
Adjustments for differences in neighborhood characteristics are much more
difficult to accomplish, since they are grounded on the subjective evaluations of both
buyers and sellers. Buyers and sellers may evaluate all neighborhood characteristics
known to them as a set, rather than individually. If so, the "other things equal"
method would be the only method to measure property value differentials due to odors.
Taking an optimistic position, the author offers the following approach to measure
differences in neighborhood characteristics in general and differences due to odors
-9-
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in particular.
A randan sample of homeowners in the affected and control neighborhoods
would be asked to indicate on a scale of, for instance, one to ten, how much each
of the neighborhood characteristics (identified by the appraisers as possible contrib-
uting factors) represents a problem to them. A weighted average of the distribution
of the ratings would then be computed for each factor in each neighborhood using a
standard formula such as
10
X=i=1
fiX.
10
Ł f.
1=1 l
where X = the weighted average of the distribution, x^ = the ith rating and f. = the
frequency of responses to the ith rating. For example, assume that only three neigh-
borhood characteristics had been identified as possible contributing factors and that
interviews of 100 homeowners in each neighborhood had produced the distributions of
problem ratings given in Figure 1. The weighted averages of these assumed distri-
butions are given in Table HI.
173
-------
Figure 1. Distribution of problem ratings of three neighborhood characteristics resulting
from hypothetical interviews with homeowners in a neighborhood affected by odors and a
relatively odor-free neighborhood.
Neighborhood Distribution in Distribution in
Characteristic Affected Neighborhood* Control Neighborhood*
Presence of Odors
in the Neighborhood
# Responses 5 10 15 25 25 15 5 5 15 25 25 15 10 5
I 1 1 1 I—I 1 1 1 1 I 1 1 1 H
Rating 12 4 6 8 10 12 4 6 8 10
Distance to Central
Business District from
the Neighborhood
# Responses 5 20 50 20 5 20 50 20 10
I 1 1 1 1 1 1 1-
Rating 12 4 6 8 10 1. 2 4 6 8 10
Quality of Schools
Serving the
Neighborhood
# Responses 60 30 10 515 30 30 15 5
1 1 1 t—I 1 hH 1 I
Rating 12 4 6 8 10 12 4 6 8 10
Explanation of Rating Scale: "1" represents no problem; "10" represents a serious problem.
*Assumes a total of 100 interviews completed in each neighborhood.
-11-
173
A
-------
Table III» Weighted averages of the distrubutions depicted in Figure 1.
Neighborhood Affected Control
Characteristic Neighborhood (AN) Neighborhood (CN) Difference (AN-CN)
Presence of Odors 6.2 3.8 +2.4
in the Neighborhood
Distance to Central 3.0 2.2 +0.8
Business District from
the Neighborhood
Quality of Schools 1.5 3.5 -2.0
Serving the
Neighborhood
Totals 10.7 9.5 +1.2
The net figure, +1.2, would represent the total contribution of differences in
neighborhood characteristics to the average property value differential, while the net
figure, +2.4, would represent the contribution due to the greater impact of odors on
the affected neighborhood. If the average property value differential had been computed
to be $1,800 and if differences in property characteristics had been determined to
account for $1,000 of the differential, then differences in neighborhood characteristics
would account for the remaining $800 of the differential. By simple proportion, the
presence of odors would reduce the average value of single-family dwelling units in
the affected neighborhood by $1,600 relative to the average value of comparable units
in the control neighborhood.
Summary
It was Pigou's principle that whenever the actions of private enterprise cause
a divergence between private and social costs, the government should intervene. Yet,
-12-
174
-------
the measurement of social costs is usually difficult and often impossible for the economist
to perform. Except for one possibility, so it is with the social costs of odors. The single
possibility is that of property value differentials.
Based on the subjective nature of odor evaluation and the types of neighborhood,
occupant, and property data available, two methods of measuring property value differ-
entials due to odors seem promising. One of these methods is currently being tested in
the Los Angeles Metropolitan Area. It requires careful location of an odor-free neigh-
borhood near an odor-affected neighborhood so that any property value differential found
between the areas may be attributable to the presence of odors. This method is work-
able, but difficult to apply generally because of the many constraints necessary to main-
tain "other things equal."
The second method is untried. As in the first method, an average property value
differential between two neighborhoods would be computed using secondary data. Follow-
ing this, a series of discussions would be held with highly qualified real estate appraisers
in order to identify all the factors that they believe may have contributed to the differential.
The factors would be categorized as arising from differences in neighborhood, occupant,
and property characteristics.
Adjustments of the computed differential for differences in occupant and property
characteristics would be readily accomplished using secondary data. Adjustments for
differences in individual neighborhood characteristics such as the presence of odor would
be approached through a survey of homeowners in the neighborhoods under investigation.
To substantiate the validity of this method, it would be necessary to determine whether
the opinions of homeowners are representative of the opinions of home buyers and sellers
-13-
175
-------
as they negotiate together.
Acknowledgements
This paper is based, in part, on a study being performed under Contract
No. CPA 70-116 with the Environmental Protection Agency, Air Pollution Control
Office. The author is grateful to Mr. R. Paul Weddell for his contribution of
information and to Dr. Donald G. Gillette and Mrs. Marian O. Doscher for their
comments leading to the final draft.
Notes
1. A. C. Pigou, The Economics of Welfare (4thed.; London: Macmillan,
1932).
2. Ronald G. Ridker and John A. Henning, "The Determinants of Residential
Property Values with Special Reference to Air Pollution," Review of Economics
and Statistics, XLK (May, 1967), pp. 246-257, and Ronald G. Ridker,
Economic Costs of Air Pollution (New York; Frederick A. Praeger, 1967),
chapters 6 and 7.
3. Robert]. Anderson, Jr. and Thomas D. Crocker, Air Pollution and Housing:
Some Findings, Paper No. 264 (Institute for Research in the Behavioral,
Economic, and Management Sciences, Herman C. Krannert Graduate School
of Industrial Administration, Purdue University, 1970).
-14-
'76
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PRELIMINARY DRAFT
Health Effects of Pulp Mill Odor'in
Anderson, California
Margaret Deane and John R. Goldsmith, M.D
California State Department of Public Health
Bureau of Occupational Health and
Environmental Epidemiology
For presentation at the Conference on the Dose-Response Relationships
Affecting Human Reactions to Odorous Compounds, April 26 -30,
Boston, Massachusetts.
177
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INTRODUCTION
During late summer of 1970 the California Air and Industrial
Hygiene Laboratory carried out an environmental survey designed to
measure the presence and intensity of pulp mill odor in the Anderson-
Cottonwood area of northern California. Both chemical and organo-
leptic measurements were used. In spite of several limitations,
this location seemed appropriate for carrying out a health survey
in relation to exposure to pulp mill odor. A previous study in a
northern coastal area of California (Eureka) had been conducted
during the summer of 1969 to estimate annoyance reactions to pulp
mill odor and to test their relationship to several measurements
of exposure to odor. Hovever, in the Eureka study questions concern-
ing physical health were asked only of respondents who indicated
that they were "very much" or "moderately" "bothered "by the odor.
Furthermore, the health question was phrased "Do you get any of the
.following symptoms when you are bothered by the odors?" The results
have limited value for comparing the health of individuals experienc-
ing different levels of exposure to odor since responses were not
obtained from individuals who:
1. were not "very much" or "moderately" bothered by the odor;
2. lived in relatively odor-free areas;
3. did not attribute their symptoms to the odor.
In addition, because the questionnaire obviously dealt .with reactions
to the odor, the responses might have been biased because of the
respondents' attitudes toward the odor or their desire to force
community action against the source. A better measure of health
ought to be obtained by a general health survey .of all members of
17
-------
a population sample chosen so as to represent varying exposures to
odor. The questionnaire or interview should make no reference to
the odor although the respondent might be given an opportunity to
attribute his symptoms to odor.
AIMS
The specific aim of the Anderson study was to determine whether
community exposure to odor from pulp mills has any effect on health
measurable by the type of personal interview used. Implicit in the
design of such a study is the measurement and "control" (during
analysis) of other relevant factors which may affect the health
responses to the questionnaire. A similar study is being carried
out in the same area to determine whether satisfactory results can
be obtained from a postal questionnaire.
METHODS
Description of Study Area
According to an estimate made in 1967, the incorporated City
of Anderson had a population of 6,137 persons. The sampling frame
for the study was comprised of 1,2^6 households, including most of
the incorporated area as well as some unincorporated districts.
The town is located at the extreme north of the Sacramento Valley.
Unlike Eureka, which experiences the moderating effect of the Pacific
Ocean, Anderson is exposed to seasonal extremes of temperature and
rainfall. Also in contrast to Eureka, which is exposed to a sea-
sonal shift in wind direction, Anderson is characterised year around
by winds from the northeast in the morning, shifting to the southeast
in the afternoon.
ISO 18
-------
As mentioned above, several limitations of the area were recog-
nized with respect to population surveys. These included the relative-
ly small size of the community, the small proportion of the population
which lives near the pulp mill, and the predominantly rural character
and poor housing of the area closest to the mill compared with the
areas with less exposure to the pulp mill odors.
Selection of Exposure Areas
Before the environmental survey, three areas of Anderson had
"been defined as representing three levels of presumptive exposure
to odor on the "basis of topography, prevailing winds, and distance
from the mill. (Figure l) These were subsequently confirmed by the
environmental measurements. (Figure II) Although these measurements
were made in August and the health survey was carried out in November,
the seasonal factor was not felt to be of importance because the
prevailing wind pattern is essentially the same all year round.
To take advantage of the diurnal wind pattern, Cottonwood measure-
ments were made in the morning and Anderson measurements were made
in the afternoon.
The two areas farthest from the mill in the Anderson sector
were selected to represent moderate and slight exposure to the odor.
The areas closest to the mill in both the Anderson and Cottonwood
sectors were combined and expanded slightly to represent the greatest
exposure to the odor.
19
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Sampling
Preliminary scouting of the three "exposure" areas suggested
that significant differences occurred in housing, type of neighbor-
hood, including population density, and possibly in level of income.
It was not feasible to characterize these subareas with any degree
of precision, but some stratification seemed advisable. Consequently,
each "exposure" area was subdivided into three subareas, character-
ized predominantly by scattered rural housing, central town-type
housing, and suburban tract-type housing. The rural housing was
defined primarily on the basis of sparsity of settlement, but ap-
peared to represent a relatively large proportion of housing of
poor quality, frequently located on property which included farm
out-buildings and livestock. The suburban tract-type housing was
on the outskirts of town and was largely "California ranch" style.
The housing in the central areas was usually more modest and was
located in the older, central part of town where a grid pattern of
streets prevailed.
The "exposure" areas will subsequently be referred to as
Areas I, II and III, representing high, moderate, and low exposure
to pulp mill odor, and the subareas will be designated as rural,
central, and tract.
Unfortunately, from the viewpoint of study design, Area I
(high exposure), is sparsely populated and fell entirely within
the rural subgroup. The highest rate of housing vacancy appeared
to occur here. Areas II and III are comprised of all three resi-
dential subgroups.
The sample sizes shown below ( Table 1 ) were chosen so as
to permit some comparison within residential subgroups as well as
182 20
-------
between totals for each of the three areas. The high sampling ratios
may have been a disadvantage because they increase the possibility
of bias resulting from pre-interview discussion of the survey among
respondents.
A sampling frame vas constructed for each subarea by listing
all houses which appeared to be occupied. If houses included in
the sample were found to be unoccupied at the time of interview,
they were replaced by sampling randomly between the "interviewed"
houses on either side.
Sampling was systematic with an independent random start in
each subarea. Alternate households were designated to have a male
or female respondent interviewed. If a household did not have a
respondent of the designated sex, one of the other adult members
was interviewed.
Questionnaire Design
The questionnaire included information regarding date of birth,
sex, marital status, occupation and place of employment, length of
residence in the area, pre-existing medical conditions, smoking
habits, and exposure to specific industrial hazards which might
affect health. The basic questions of the British Medical Research
Council's Questionnaire on Respiratory Symptoms (1966) were included
as a measure of chronic effects. This was followed by three sets
of questions concerning symptoms which it was believed might be
associated with exposure to pulp mill odor. The respondent was
first asked whether he has each of these symptoms frequently, occasion-
ally, or hardly ever. For each symptom experienced frequently or
occasionally, he was then asked whether there was anything in parti-
cular which seems to bring it on, and whether he had it during the
21 183
-------
past tvo weeks. He was also asked whether he had been sick at any
time during the last two weeks, and whether he would say that his
health was excellent, good, fair, or poor. It proved to be cumber-
some and time-consuming to ask this much detail about the symptoms
on the list, but no estimate existed of the frequency of these symp-
toms in the general population, and we hoped to obtain adequate
frequencies of at least some of the responses to permit statistical
testing of the results. It was also felt that the respondent should
be given an opportunity to attribute symptoms to the pulp mill odor
although the odor was not mentioned at any time during the interview,
The interview was introduced to the respondent as a general health
survey and no reference was made to pulp mill odor anywhere in the
questionnaire.
Interviewing
Interviewing was carried out by two part-time and four full-
time interviewers, including two staff members who participated in
other aspects of the survey. Training began on the Wednesday even-
ing preceding the field work and continued through part of the fol-
lowing Saturday. A preliminary description of the study and run-
through of the questionnaire and instructions was followed by demon-
stration interviews by staff members and practice interviews by
staff members and trainees.
Standard training tape recordings of demonstration interviews
of the MRC part of the questionnaire were also used. The most
intensive part of the training consisted of one-to-one interviewing
practice with the training staff, followed by playback of tape re-
cordings and group discussion. The final phase of training included
"real" interviews on members of a community not being included in
184 22
-------
the survey proper. Completed' questionnaires were edited by staff
members and discussed with the trainees.
The initial plan required each interviewer to interview a
proportionate number of respondents in each area, and to spread the
interviews systematically by date in each area. The former should
have equalized interviewer differences which were not eliminated
by the training sessions so that they would not appear as area dif-
ferences; the latter was to insure that increasing community aware-
ness of and discussion of the content of the study would occur at
the same rate in all areas. In practice, it became increasingly
difficult to maintain this schedule beyond the first few days of
interviewing.
Each interviewer was usually seen by a staff member at least
once a day. for collection of completed interview schedules, assign-
ment of new interviews, and discussion of problems. Some preliminary'
editing of interview schedules was done on a current basis so that
omissions or errors could be corrected while field work was still
in progress.
Results
Table 2 shows the prevalence of cough, phlegm, and shortness
of breath defined from responses to the MRC questions,
demonstrating differences by area and sex.In all three exposure
areas, cough and phlegm were reported by a larger proportion of men
than women; in all three areas shortness of breath was reported
more frequently by women. A consistent trend can be seen in preva-
lence of all MRC symptoms among men, increasing from the area of
greatest exposure (Area l) to the area of least exposure (Area III),
23
185
-------
but some inconsistencies in prevalence appear among women, mainly
"between Areas II and III. Chi square tests for trend showed the
exposure area differences to "be significant only for phlegm grades
1 and 2 combined and persistent cough and phlegm among men.
The proportion of men and women in each area reporting each of
a set of sixteen symptoms frequently or occassionally and within
the last two weeks are shown in Tables 3 and it. Tests of statistical
significance have not been completed.
In order to explore the possibility that apparent area differ-
ences merely reflect the influence of background variables, chi
square tests were done to test the relationship between the responses
to the health variables and the background variables. Cough and
phlegm showed significant relationships to several of the "background
health" variables and to smoking and type of housing area (whether
rural, tract, or central town). Since no dates of occurrence were
obtained for the background health variables (which were phrased
"have you ever had?"), it cannot be determined whether the relation-
ships to these imply a possible effect before exposure to pulp mill
odor or whether they imply a current relationship. Among present
cigarette smokers, the amount smoked did not show a significant
relationship to the MRC questions (Table 5).
Smoking habits (never, ex-, and present smokers) were found •
not to differ significantly by exposure area, so they were not
taken into account in the analysis by area.
The effect of subarea was tested by combining data for Areas
II and III (Area I had only rural housing) and stratifying by rural,
tract, and central town housing. The significant relationship to
24
188
-------
cough and phlegm suggests that apparent exposure area differences
could be due to differences in housing. In order to test this,
responses to the MRC questions were tabulated to show exposure area
comparisons for rural subareas only. These are shown in Table
6.
Similar significant relationships were found between various
background variables and frequency of 16 listed symptoms as well
as incidence within the last two weeks. Occupation and industry
showed significant relationships to nervousness, insomnia and pal-
pitations. Marital status was significantly related to nervousness
and fatigue. Comparisons for rural subareas are shown in Tables 7, 8
Eight individuals attributed at least one symptom specifically
to odor in the air. These included headache, insomnia, sinus con-
gestion, eye irritation, burning or irritation of the nose, runny
nose, and cough. An additional seventeen attributed at least one
symptom to air pollution without specifically mentioning odor.
Discus sion
Although the area comparisons are inconclusive, they suggest
that the interview as structured is a useful method for further
studies of the health effects of exposure to pulp mill odor.
Furthermore, relationships among the health variables themselves give
some evidence for the validity of the questions. For example,
responses to the question, "Would you say that your health in general
is excellent, good, fair or poor?", showed a highly significant
relationship to many of the other health questions.
The apparent effect of type of residential area indicates the
importance of taking into account socio-economic variables in making
25
187
-------
area comparisons. Larger sample sizes would increase the possibility
of determining the effects of the background variables.
Further analysis is being planned in conjunction with two later
phases of the study: the additional health survey by postal ques-
tionnaire and a study of annoyance reactions to odor similar to that
conducted in Eureka. Multivariate analysis is planned to examine
further the effect of the background variables.
188
26
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Acknowledgements
Acknowledgements are made to George Sanders for data from the
environmental survey, and Madeline Thresh and Linda Scott for assis-
tance in carrying out the field vork and data processing.
27
189
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#'
5^' y V
ft vY. --•'">}
K7 i. ' '^T^>>
29
-------
FIGURE II
DRJRNAL FREQUENCY •(%)
. TJME
1 300-3 329
3330-1359
1 '100-1'! 29
3 430- M59
150 0-1 5 29
1530-1559
1600-1 629
1630-1659
1700-1729
1730-1759
1800-1829
3830-1859
1900-1929
] 930- 1959
2000-2029
2030-2059
2100-2129
2130-21 59
Overall
AREA
1
50.0
'i 1 .7
37.5
58.3
75.0
75.0
41.7
58.3
12.5
75.0
58.3
87.5
58.3
75.0
50.0
83.3
58.3
62.5
59. -1
AREA
2
22.2
50.0
22.2
22.2
11.1
1.1.1
5.6
50.0
0.0
5.6
0.0
0.0
yi/1.4
0.0
38.9
22.2
0.0
0.0
17.0
AREA
3
0.0
20.8
2.5.0
1 2.5
0.0
0.0
6.3
0.0
1.2
0.0
8.3
12.5
37,5
32.5
25.0
6.3
4.2
0.0
9.6
ALL
ART- AS
21.7
33.3
26.0
28.3
18.8
16.0
15.2
27.1
4.5
21.7
18.8
20.0
45.7
23.0
34.0
30.7
. 16.V
11.4
23.2
Total mun'ocr ofmaloclor detections
(Overall frequency-- x 100)
Total number of MJC;isuiT.mcnts
MAXIMUM MALODOR CONCENTRATION
pp'o ODOR AS CH?.SH
. . I * *J
ANDERSON '
192-
TIME
1300-1329
1330-1359
1400-1429
1430-1459
1500 -1529
3530-3.559
1600-1629
1630-1659
1700-1729
1730-1759
1800-1829
1830-1859
3900-1929
3930-1959
2000-20 29
2030-2059
2100-2129
21 30 ?J 59
A.REA
1
58.0
14.8
39.5
55.0
49.0
266.2
46.6
72.4
37.6
39,0
216.8
384.5
19.1
'1,681.4
33.7 .
67 /j
-13. S
Ifi.G
AREA
2
7.2
5.8
15.6
8.0
N.D.
81.0
13.6
8.2 .
N.D.
2.8
N.D.
N.D.
5.9
N.D.
19.4
4.9
N.D.
N.D.
AREA
3
N.D.
34.4
15.5
4,2
N.D.
N.D.
2.7
N.D.
6.5
N.D.
3.2
3.7
75.7
22.6
6.0
6.6
27.2
N.D.
ALL
AREAS
58.0
34 .4
39.5
55.0
49.0
266.2
46.6
72.4
17.6
39.0
216.8
384.5
75.7
3,681. 4
33.7
67.6
•13.8
36.6
30
-------
Table 1
Sample Sizes and Sampling Ratios
by Exposure Area and Housing Subarea
AREA I
Rural
Popul. = 115
Sampling
Ratio = 1:1
Sample = 100
Central
Popul. = 67
Sampling
Ratio = 1:1.3
Sample = 52
Tract
Popul. = 154
Sampling
Ratio = 1.3
Sample = 51
AREA II
Popul.
Popul. = 232
Sampling
Ratio = 1:4.6
Sample = 45
Popul. » 298
Sampling
Ratio = 1:5.4
Sample = 50
AREA III
Popul. = 0
Popul. = 97
Sampling
Ratio = 1:1.9
Sample = 50
Popul. = 383
Sampling
Ratio = 1:7.5
Sample = 50
31
193
-------
Table 2
Prevalence of Respiratory Symptoms
Anderson, 1970
dumber of Observations
Cough Grade 1 or 2
Cough Grade 2
Phlegm Grade 1 or 2
Phlegm Grade 2
Persistent Cough & Phlegm
Shortness of Breath Grade
2 or Greater
Shortness of Breath Grade
3 or Greater
Male
Total
177
17.5
6.8
16.9
9.6
9.6
25.4
9.6
I
48
22.9
10.4
25.0
16.7
16.7
29.2
6.2
II
67
17.9
6.0
17.9
7.5
9.0
25.4
14.9
III
62
12.9
4.8
9.7
6.5
4.8
22.6
6.5
Female
Total
222
11.3
4.5
9.9
5.4
4.5
40.5
7.2
I
52
15.4
9.6
17.3
9.6
9.6
38.5
9.6
II
80
11.2
2.5
7.5
3.8
1.2
41.2
3.8
III
90
8.9
3.3
7.8
4.4
4.4
41.1
8.9
Note:
Cough -
Grade 1
Grade 2
Phlegm -
Grade 1
Grade 2
Cough first thing in the morning or during the day or at night
on most days for as much as three months each year.
Cough first thing in the morning and during the day or at night
on most days for as much as three months each year.
Phlegm first thing in the morning or during the day or at night
on most days for as much as three months each year.
Phlegm first thing in the morning and during the day or at night
on most days for as much as three months each year.
Persistent Cough and Phlegm; At least Grade 1 of both cough and phlegm.
Shortness of Breath -
Grade 2; Shortness of breath when hurrying on level ground or walking
194
up a slight hill.
Grade 3; Shortness of breath walking with other people of own age on
32
level ground.
-------
Table 3
Prevalence of Symptoms Reported
Frequently or Occasionally
Anderson, 1970
Number of Observations
Nervousness
Headache
Insomnia
Fatigue
Palpitations
Dizziness
Nausea
Vomiting
Sweating
Sinus Congestion
Eye Irritation
Shortness of Breath
Nose Irritation
Runny Nose
Chest Pain
Cough
Male
Total
177
34.5
30.5
14.7
27.1
7.9
10.1
5.1
1.7
14.7
32.8
15.3
14.7
5.6
24.3
9.6
26.0
I II III
48 67 62
41.7 40.3 22.6
41.7 29.9 22.6
10.4 19.4 12.9
37.5 22.4 24.2
6.2 10.4 6.5
8.3 10.4 11.3
12.5 1.5 3.2
4.2 1.5 0.0
16.7 11.9 16.1
39.6 26.9 33.9
16.7 16.4 12.9
18.7 13.4 12.9
8.3 7.5 1.6
33.3 20.9 21.0
14.6 7.5 8.1
39.6 20.9 21.0
Female
Total
222
62.6
44.6
29.7
48.2
16.2
22.1
11.7
4.1
20.7
35.6
18.5
23.4
7.7
28.4
10.8
20.7
I II III
52 80 90
67.3 63.8 58.9
51.9 50.0 35.6
25.0 28.8 33.3
50.0 46.2 48.9
15.4 10.0 22.2
21.2 18.8 25.6
11.5 13.8 10.0
0.0 3.8 6.7
28.8 18.8 17.8
38.5 35.0 34.4
17.3 20.0 17.8
26.9 22.5 22.2
7.7 11.2 4.4
32.7 32.5 22.2
9.6 12.5 10.0
21.2 21.2 20.0
33
195
-------
Table 4
Prevalence of Symptoms Reported Frequently or
Occasionally and During the Last Two Weeks
Anderson, 1970
Number of Observations
Nervousness
Headache
Insomnia
Fatigue
Palpitations
Dizziness
Nausea
Vomiting
Sweating
Sinus
Eye Irritation
Shortness of Breath
Nose Irritation
Runny Nose
Chest Pain
Cough
Male
Total
177
19.2
17.5
10.2
18.1
2.8
2.3
1.7
1.1
6.2
17.5
7.3
7.3
2.8
11.9
8.5
17.5
I
48
22.9
27.1
6.2
27.1
0.0
4.2
2.1
2.1
6.2
25.0
6.2
10.4
4.2
20.8
12.5
29.2
II
67
19.
17.
11.
13.
3.
0.
1.
1.
4.
14.
6.
7.
3.
11.
6.
11.
4
9
9
4
0
0
5
5
5
9
0
5
0
9
0
9
III
62
16.
9.
11.
16.
4.
3.
1.
0.
8.
14.
9.
4.
1.
4.
8.
14.
1
7
3
1
8
2
6
0
1
5
7
8
6
8
1
5
Female
Total
222
49.1
34.7
21.2
32.9
7.7
12.6
8.1
2.3
15.3
19.4
11.7
14.4
3.6
17.6
8.1
14.4
I
52
50.
44.
23.
42.
7.
13.
7.
0.
21.
28.
11.
17.
3.
26.
9.
21.
0
2
1
3
7
5
7
0
2
8
5
3
8
9
6
2
II
80
51.2
37.5
17.5
30.0
7.5
12.5
8.8
2.5
13.8
17.5
12.5
15.0
5.0
15.0
8.8
11.2
III
90
46.7
26.7
23.3
30.0
7.8
12.2
7.8
3.3
13.3
15.6
11.1
12.2
2.2
14.4
6.7
13.3
196
34
-------
Table 5
Chi Square Test for Relationship Between
MRC Questions and Background Variables
Anderson, 1970
Chest Illness
Past Three Years
Bronchiti s
Pneumonia
Pleur i sy
Hay Fever
Smoking
Nev ,Ex ,Pres
Smoking Cigarettes
Amount
Area
Subareas
MRC
Quest ions
Cough Grade
x2 d.^.
31.
19.
10.
8.
2.
27.
5.
16.
9U** 1
13** 2
11*** 2
56* 2
96 2
87** 1*
61+ 1*
oit* i*
Phlegm
X2
27.22**
19-10**
7.30*
2.87
6.52*
13.96**
1.35
1.98
Grade
d.f .
2
2
2
2
2
1*
It
It
Persi
Cough &
stent
Phlegm
p
v d. • f •
N.V.
N.V.
7. 51***
N.V.
0.68
16.07**
1.03
2.U3
-
-
1
1
1
2
2
2
* Significant at the 5$ level.
** Significant at the 1% level.
35
197
-------
Table 6
Prevalence of Respiratory' Symptoms
Rural Subareas Only
Anderson, 1970
Number of Observations
Cough Grade 1 or 2
Cough Grade 2
Phlegm Grade 1 or 2
Phlegm Grade 2
Persistent Cough & Phlegm
Shortness of Breath
Grade 2 or Greater
Shortness of Breath
Grade 3 or Greater
Male
Total
91
15. 1*
5.5
18.7
11.0
9.9
2U.2
5-5
1*8
22
10
25
16
16
29
6
I
.9
.h
.0
.7
.7
.2
.2
II
21*'
U.2
0.0
16.7
8.3
U.2
20.8
8.3
I
19
10
0
5
0
0
15
0
II
.5
.0
.3
.0
.0
.8
.0
Female
Total
112
10.7
U.5
11*. 3
8.9
6.2
ho. 2
7.1
I
52
15.
9.
17.
9.
9.
38.
9.
li
6
3
6
6
5
6
II
28
7.1
0.0
17.8 •
10.7
3.6
1*2.9
0.0
III
32
6.2
0.0
6.2
6.2
3.1
1*0.6
9.U
Note:
Cough
Grade 1
Grade 2
Cough first thing in the morning or during the day or at night
on most days for as much as three months each year.
Cough first thing in the morning and during the day or at night
on most days for as much as three months each year.
Phlegm
Grade 1: Phlegm first thing in the morning or during the day or at night
on most days for as much as three months each year.
Grade 2: Phlegm first thing in the morning and during the day or at night
on most days for as much as three months each year.
Persistent Cough and Phlegm: At least Grade 1 of both cough and phlegm.
Shortness of Breath
Grade 2: Shortness of breath when hurrying on level ground or valking up
a slight hill.
Grade 3: Shortness of breath walking with other people of own age on level
ground.
198
36
-------
Table 7
Prevalence of Symptoms Reported
Frequently or Occasionally
Rural Subareas Only
Anderson, 1970
Number of Observations
Nervousness
Headache
Insomnia
Fatigue
Palpitations
Dizziness
Nausea
Vomiting
Sweating
Sinus Congestion
Eye Irritation
Shortness of Breath
Nose Irritation
Runny Nose
Chest Pain
Cough
Male
Total
91
37.4
36.3
15.4
29.7
7.7
8.8
7.7
2.2
12.1
34.1
13.2
12.1
5.5
28.6
11.0
27.5
I
48
41.7
41.6
10.4
37.4
6.2
8.3
12.5
4.2
16.7
39.6
16.5
18.7
8.4
33.3
14.6
39.6
II
24
41
33
20
25
8
8
4
0
8
16
1.2
8
4
25
8
12
.7
.3
.8
.0
.4
.4
.2
.0
.4
.6
.5
.3
.2
.0
.4
.5
III
19
21.
26.
21.
15.
10.
10.
0.
0.
5.
42.
5.
0.
0.
21.
5.
15.
0
3
0
8
5
5
0
0
3
1
3
0
0
0
3
8
Female
Total
112
66.1
45.5
25.9
48.2
13.4
25.9
13.4
4.5
24.1
38.4
19.6
25.9
9.8
33.0
10.7
21.4
I
52
67.3
51.9
25.0
50.0
15.3
21.2
11.6
0.0
28.9
38.5
17.3
26.9
7.7
32.7
9.6
21.1
II
28
64.
46.
21.
42.
7.
17.
14.
7.
17.
32.
21.
25.
21.
32.
10.
17.
2
4
4
9
1
9
3
1
8
2
4
0
4
1
7
9
III
32
65.6
34.4
31.3
50.0
15.6
40.6
15.6
9.4
21.8
43.8
21.9
25.0
3.1
34.3
12.5
25.0
37
199
-------
Table 8
Prevalence of Symptoms Reported
Frequently and Occasionally and
During the Last Two Weeks
Rural Subareas Only
Anderson, 1970
Number of Observations
Nervousness
Headache
Insomnia
Fatigue
Palpitations
Dizziness
Nausea
Vomiting
Sweating
Sinus Congestion
Eye Irritation
Shortness of Breath
Nose Irritation
Runny Nose
Chest Pain
Cough
Male
Total
91
20.
22.
8.
22.
2.
3.
2.
1.
4.
19.
7.
5.
2.
16.
9.
18.
9
0
8
0
2
3
2
1
4
8
7
5
2
5
9
7
I
48
22.9
27.1
6.2
27.1
0.0
4.2
2.1
2.1
6.3
25.0
6.2
10.4
4.2
20.8
12.5
29.2
II
24
20.
20.
8.
20.
4.
0.
4.
0.
4.
8.
12.
0.
0.
12.
8.
4.
8
8
3
8
2
0
2
0
2
3
5
0
0
5
3
2
III
19
15.
10.
15.
10.
5.
5.
0.
0.
0.
21.
5.
0.
0.
10.
5.
10.
8
5
8
5
3
3
0
0
0
0
3
0
0
5
3
5
Female
Total
112
50.0
38.4
22.3
33.0
7.1
16.1
8.9
1.8
19.6
23.2
10.7
14.3
5.4
22.3
7.1
16.1
I
52
50.0
44.2
23.1
42.3
7.7
13.5
7.7
0.0
21.2
28.8
11.5
17.3
3.8
26.9
9.6
21.2
II
28
46.4
39.3
14.3
17.9
7.1
17.9
7.1
3.6
14.3
14.3
14.3
10.7
14.3
14.3
3.6
7.1
III
32
53.1
28.1
28.1
31.2
6.2
18.8
12.5
3.1
21.9
21.9
6.2
12.5
0.0
21.9
6.2
15.6
38
-------
Summary of technical problems
By
Lars Friberg
As a basis for this presentation, I have read several of
the working papers in advance. This has given me the oppor-
tunity to evaluate the evidence that has been presented on
dose-response relationships and to summarize some of the
problems existing in regard to the dose as well as in regard
to the response.
Although there is undoubtedly a considerable amount of data
available on odors and different types of response to odors,
I will start out with a pessimistic statement. If, when re-
ferring to dose-response relationships, we mean quantitative
associations between either odor intensities or qualities,
or concentrations of odorous substances on the one hand, and
well established adverse effects in human beings on the other,
very few data are available. Response to odors, however, must
not necessarily mean adverse long-term effects in an exposed
population, but may mean, for example, the possibilities for
human beings to detect odors or to evaluate odor intensities
or qualities. If, under such circumstances, a dose would be
defined as a concentration of a single substance or a combi-
nation of substances in relation to exposure time, more data
will be available.
In this paper, I will start with a discussion of the response,
then discuss the dose and finally talk about the dose-response
relationships. Focus will be on issues, which may have bearings
on practical problems, and on possible ways for responsible
authorities to approach the various odor problems.
49
201
-------
2.
The response
Wa will have to distinguish between a response to odors
as such and to odorous substances. The title of this con-
ference is dose-response relationships affecting human re-
actions to odorous compounds. Of course, it is not my inten-
tion to change the terms of reference for this meeting, but
my feeling is, that we should primarily discuss odors and not
odorous substances. If we include effects of odorous sub-
stances, when we embark on dose-response relationships, we
would have to discuss things like effects of high concentra-
tions of hydrogen sulfide on the central nervous system as
well as on the respiratory system. We might wish to include
effects, such as chronic bronchitis or eye irritation of sul-
fur dioxide ozone, since also these substances are recognized
as smelling at certain concentrations. Hundreds of other sub-
stances should be included; each substance having a more or
less specific effect on human beings.
The most common adverse effect of odorous substances are
annoyance reactions caused by the odor itself. If certain
substances, H_S or mercaptans for example, in concentrations
found in the ambient air, give rise to adverse effects caused
not by the odors per se but by a direct toxic action, such
effects and dose-response relationships should be considered
with regard to the particular substances in the same way as
has been done in air quality criteria documents for e.g. sulfur
oxides and oxidants.
Disregarding the more unspecific annoyane reactions, very
few studies have been carried out with the aim of evaluating
whether or not long-term exposure to odors can give rise to
chronic disease. No doubt, acute effects in the form of nausea
or even vomiting are often reported at interview surveys.
50
202
-------
3.
Furthermore, in David Kendall's report we have evidence of
reactions from the autonomic nervous system. The meaning of
such reactions for possible long-term effects are not well
understood. John Goldsmith's report, which I have, unfor-
tunately, only seen in an abstpact form, indicates that per-
sistent cough and phlegm were more frequent in areas close
to a pulp and paper mill than in control areas. If this is
an effect of odors, and not a toxic effect of an odorous sub-
stance or possible substances occurring together with the
odorous substances, this would be the first evidence of a
well-defined medical effect of exposure to odor. One would
like to find a plausible explanation, though, how such effects
could arise. Reactions from the autonomous nervous system
might be important in this connection.
The more unspecific annoyance reactions have been documented
in various countries in different exposure situations, e.g.,
around pulp mills, around areas spread with manure and from
motor exhausts in cities. Such reactions must be evaluated
with great caution. City dwellers complain heavily of the
air pollution situation. There are good reasons to believe
that exposure to odors is a major cause of such complaints,
but exposure to other agents is certainly also important.
I may in this connection refer to dose-response relationships
established in the US air quality criteria document on parti-
culate matters.
Annoyance reactions are not easily evaluated, besides we
have no clear indication of possible medical implications
in the long run of such reactions. From the methodological
point of view, there is a great need for evaluating existing
methods, e.g. survey technics, as well as establishing new
methods. Petitions and spontaneous complaints are notorously
51
203
-------
4.
unreliable as has been examplified in a presentation by
Erland Jonsson earlier today. Such questions will be dealt
with at a meeting to be held at the Karolinska Institute
in Stockholm this September and sponsored jointly by the US
and Swedish Environmental Protection Agencies.
Concerning the long-term medical implications we are in the
same position as when evaluating effects of traffic and air-
craft noise. We are well aware of the fact that people are
annoyed, often to a considerable degree, but we do not know
enough of possibly more serious endpoints.
Whatever the medical endpoints may be, the first question
to be answered by agencies responsible for the control of
air pollution is the following: are health effects in the
form of only annoyance reactions, with possibilities of other
and more severe reactions in the long run, sufficient evidence
for the taking of administrative steps in order to reduce the
exposure to odors? In my opinion this question should be an-
swered with yes.
The dose
If the answer to this question is yea, the next step to con-
sider is whether or not it is possible to describe the dose.
It would certainly be an overstatement if we said that good
methods, suitable for field work, are available to describe
the dose under all circumstances occurring in everyday life.
On the other hand, I think it is fair to state that very often
we have the technical know-how and also the technical facili-
ties to describe the dose either based on sensory evaluations
or chemical analyses. The practical implications, however, are
often formidable due to the many dimensions involved. In several
52
2
-------
5.
working papers, it has been well documented that the dose
often should not be expressed only as whether or not and
how often it smells. The hedonic aspects of odors as well
as intensity above threshold are of importance.
Whether or not it smells can be decided by means of odor
threshold studies. For single substances we often have good
information about the critical concentration for detection.
The information is much more scarce for mixtures of different
substances. However, I can see no major difficulties, which
could not be overcome when working out quantitative relations
between odor thresholds and mixtures, although such studies
may be time-consuming because of, among other things, the
nature of the Stevens exponents, as discussed by Amos Turk.
It is possible to carry out odor threshold studies at the
source as well as in the ambient air using sensory methods.
Generally, chemical analyses at the source should present
no serious problems. The situation is another one at chemical
analyses of the ambient air, as meaningful analyses must have
a high enough sensitivity to measure threshold concentrations
over very short periods of time, probably seconds, because of
the short response time of the human nose.
The frequency of odor is another important criterion. It
goes without saying that any adverse response within an ex-
posed population must be correlated to some degree with the
number of times (and the duration of each time) odor thres-
holds are exceeded. It raises considerable problems to eva-
luate this. One can use observers, located at several places
in the area to be observed, or one can carry out sensory ana-
lyses of the ambient air at different times and at different
places. Practical problems will often make such type of ana-
53
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B.
lysis impossible, If we get instruments which can register
odorous substances in low enough concentrations over short
periods of time and if we know how the odor thresholds change
with different composition of the air to be analyzed, we
could, of course, use chemical analyses. Such instruments are
still lacking even if progress seems to have been made con-
cerning analyses of certain sulfurous compounds.
One way that has been 'used in Sweden merits some consideration.
I am referring to the method of estimating how often odor thres-
holds can be expected to be exceeded based on intenstity or
concentrations of certain substances in emitted stack gases.
Ulf Hogstrom and Thomas Lindvall have reported on the theore-
tical background and the practical results achieved up until
now from studies around Swedish pulp mills. By and large, this
method seems promising and the agreement, found between predicted
and observed odor frequencies, has been reasonably good. Ulf
Hogstrom's statement, that the method can be modified to give
more sophisticated answers concerning e.g. intensities above
thresholds, should make the method still more valuable. There
are several methodological problems remaining though, for ex-
ample, in connection with chemical reactions of odorous sub-
stances after the emission with the possible change in odor
intensities when the polluted air reaches ground level.
Despite limitations that still exist in the method referred
to, it has been used by agencies responsible for air pollution
control in Sweden. Health authorities, in two communities where
pulp mills are located, have ruled as a condition for the ope-
ration of the mills that gases emitted from the main stack
must not have an odor strength corresponding to a dilution
factor above 10,000. This would mean a predicted odor frequency
54
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of only a few hours per month at ground level at any place
around the industries. These regulations have been set without
having the exact dose-response relationships between odor fre-
quency and annoyance reactions.
The Swedish Environmental Protection Board, which is mainly
in favor of this type of approach, has not taken any definite
stand on how to act in the long run. For the time being, they
require that the concentration of hydrogen sulfide in the
* 3
emitted stack gases beJiret--btghQr than 10 mg/m- . This would
correspond to a dilution factor of about 10,000, provided
hydrogen sulfide is the only cause of the odors, which fact,
however is very dubious. The reason why the Environmental
Protection Board has not yet officially adopted a standard,
based on odor threshold measurements of the stack gases, is
a practical one, namely the difficulties involved in checking
the operations on a continuous basis.
In collaboration with the Environmental Protection Board,
The Karolinska Institute will carry out a study this fall,
covering the possibilities of predicting odor intensities
based on sensory as well as chemical analyses of the emitted
gases around a pulp mill. The outcome of that study will
probably be of considerable importance for future emission
standards for odors from pulp mills.
Dose-response relationships
Here I am only talking about the situation where the dose
is defined as a concentration of substance, or substances,
or sensory evaluated, and where the response is an adverse
medical effect within the exposed population.
-/—i "\ ,
be lower* than in ma/m ±Y\ 99 % of the time for new units ano
o
lower th^n 10 mq/m in 90 °4 of the time fore old mnits.
55
207
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8.
As was mentioned in the introduction, such relationships
have not been shown for any odor. We have a few points on
the dose-response curve for certain odors. I am thinking
particularly of the situation around the pulp mills. At
interview surveys in Sweden, about 25-35 percent of the
population, exposed within a radius of about 10-15 miles
from the factory, considered themselves bothered by the
smell. Generally speaking, there was a gradient with regard
to distance from the factory. Similar results have been re-
ported from the Eureka study in California. Odor threshold
studies were not carried out at the same time but from studies
at another time, there is reason to believe that the odor
strength of the stack gases would correspond to a dilution
factor of about 100,000.
Up until now the data do not show how any adverse reaction
within the population would change if the dose was doubled
or halved. Furthermore, available data refer only to one
particular exposure situation. We know that emitted gases
can differ considerably in composition from one mill to an-
other and from time to time. However, we know nothing about
the importance of the hedonic aspects. This also means that
an acceptable dose of odors from pulp mills may differ from
what can be acceptable for other types of odors. If we limit
ourselves for the moment to pulp mill odors - or to any well-
defined point source - it would be possible to carry out epi-
demiological studies, which would give more or less complete
dose-response curves. It would then be possible to predict
which changes in response could be expected, if the dose is
decreased with a certain factor. What is needed, is money
and manpower in order to carry out studies around different
point sources. The dose could be evaluated either by means
of emission analyses in connection with meteorological dis-
56
208
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9.
persion calculations or by means of direct evaluations of
the dose in the ambient air. For the time being, the first
mentioned approach seems to be the most promising one.
Apart from being time-consuming, we must appreciate that
such studies will not necessarily give data which are valid
for long periods. It has been shown that annoyance reactions
are subject to the influence of several factors not related
to the dose. The attitude towards the source of emission seems
to be of particular importance. In Sweden, Erland Jonsson
and Stefan Sorensen have shown, in a field experiment, that
annoyance reactions from aircraft noise diminished with about
50 percent if the exposed population were given a positive
attitude towards the source (in this case air traffic) as com-
pared to those given a neutral attitude.
No doubt the attitude of the people towards the need for
protection against adverse effects from the environment will
change considerably within the coming 10-20 years. In his
working paper, Trygg Engen states that there should be no
difficulty in teaching a person to experience the smell of
skunk as something pleasant. He may be right, but generally
speaking, I am convinced that it will go the other way, meaning
that what is acceptable today, might well be considered un-
acceptable within not too distant a future. Available dose-
response relations will then not be valid. This is one reason
why every effort possible should be focused particularly on
the dose, as a concentration today will mean the same con-
centration several years from now. Besides, the possibilities
of the human nose to detect - and hopefully also to make hedo-
nic evaluations - in controlled laboratory experiments will
not change considerably for long. If information on the dose
is available, there will thus always be the possibility of
establishing certain standards for odors based on known in-
57
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10.
tensities and qualities.
For odors from motor vehicles the situation is somewhat
different. Dose-response relationships where the dose is
the odor from one single source, of course, cannot be
established. Theoretically, sensory analyses can be carried
out on odors in the ambient air in the cities and related to
medical effects. As has been mentioned already, the urban
community contains so many different substances that the
difficulties to relate any effects with exposure to odors
might be overwhelming. The American approach to study the
source seems to be the best way. The question of whether or
not it will be possible to find any index substance1 for odor
is still left open. Under all circumstances, it would be
possible to use odor measurements when trying to reduce odor
and change the odor quality by the construction of new types
of motor. There are all reasons to pay much attention to odors
from motor vehicles. People are complaining about odors and
not only diesel engines are powerful producers of odor, but
regular gasoline powered engines have exhausts with odor
thresholds corresponding to dilution factors of 5,000-10,000
as seen in Swedish studies.
One could continue discussing dose-response relationships
for several other types of odors. I will just briefly mention
the odor from manure. This has become a great problem in
Sweden because of the need for having e.g. hog raising farms
fairly close to populated areas. Since this is not a single
source emitter of odors, the only approach here seems to be
to evaluate the effect of different types of treatment by
means of odor intensity and odor quality studies. Such studies
are under progress in Sweden.
58
210
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11.
As should have been obvious from what has been said, there
is not much hope for reliable dose-response associations
for odors in general within the near future. For certain
types of odors such associations could be achieved provided
money and manpower are made available. This refers to single
source odor emitters, such as pulp mills. Other approaches
seem more appropriate for other types of odors, e.g. from
motor vehicles and manure spreading. The first thing would
be to get information on the order of the problem, for instance,
by means of interview surveys. Next would be to study the possi-
bilities of reducing odors at the source. As soon as a technic
is worked out that fulfills the odor reducing requirements and
which is within reasonable technical and economical limits,
such a technic should be required.
59
211.
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Summary of the Problems in Odorous Air Pollution in Japan
by Takeo Suzuki
In Japan the investigation of odor is still in its initial stage, major
effort is being paid to the development of method of measurement of odorous
gases and only a very fev studies have been made of the dose-response
relationship in the exposure to odor. On the other hand since many petitions
of odor have been submitted to the government, the particular effort has to be
given for the control of odor by the government. The folloving is a review of
problems of odor in Japan.
1. Features of problem of odor in Japan
Japan occupies small land and furthermore as 80$ of the land is mountain
remaining only 20$ is available for human activity. Further Japan has population
of more than one hundred million, about 40$ of the population live in large cities
and industry has been rapidly progressed in the large cities and their outskirts.
Despite these situations Japanese cities have no veil arranged zoning plan, so
that industrial plants and residences are located close together. In addition
insufficient investment has been made for public utilities such as sevage system.
These situations lead to community - as veil as local - air pollution. In
Japan odor is one of the major air pollution. The autoexhaust introduces
conspicuous urban air pollution but people in the city has no special concern
vith mal-odor arising from the autoexhaust. Rather the discharge of odorous
gases from industrial production at the plants and other facilities causes the
nuisance for their neighbors.
The recent statistical results of the recent objections and petitions as
regards environmental pollution all over Japan are shown in Table 1. Total
number of objections and petitions arising from air pollution and odor in 1969
41 Ł13
-------
are 7,558 and 7,983 respectively. In recent times the petition most frequently
occurred from noise and vibration and it is followed by those due to order and
general air pollution. Needless to say the frequency of petition does not
alvays represent the level of injury and effect, and absolute number of the
episodes, but it is useful for obtaining the relative pattern of the above
levels and episodes. For example, the number of petitions of air pollution
has not appreciably been changed since 1966 but their number due to odor
increased by tvo or three times during the period of 1961 to 1969. There has
been a tendency for older Japanese to endure malodor but nov people actively
express their objection against nuisance. In addition, the generation of nev
type of odorous compounds as described belov is enhanced. These facts tell us
why the frequency of petition has been rapidly increased.
2. Major malodorous compounds and their sources in Japan
The odors to which people make objections are generally low concentration
and multi-components of gases. Although naturally the odor problem can not be
solved by the control of each one of the component gases, the gases are listed
in Table 2. which are noted as the major components of malodor as the result
of the recent development of the odor measurement techniques and the surve in
the area where the odor creates serious social problems. The major sources of
odor in Japan in recent times are petroleum chemical plants, oil refineries,
kraft pulp mills, fish and animal meal plants, live-stock yard, night soil plants
and incinerators.
Most of the petroleum chemical plants, oil refineries and kraft pulp mills
are big industrial plants. Particularly petroleum chemical and oil refining
industries have rapidly developed in recent ten years and new industrial cities
are being constituted around the core petroleum chemical and oil refining industries,
42
-------
Odor is one of the most important social problems arising from air pollution
in these new industrial cities. The odor in combination with the community
air pollution enhances the number of citizens who complain various symptoms.
Some people complain their chronic bronchitis, emphysema, asthma and cardio-
vascular diseases in conjunction vith the odor. Therefore if no measure is
taken for the problem of odor the citizens have the feeling that the community
&***% ft/ &y1ft~Ja v~ioŁ~-
-------
One of the most notable features of problem of odor in Japan is the
malodorous gases released from the following treatments and processes in
small- and middle-sized plants and other utilities. Processes of the intestines
and bone of fishes, feather, animal's fat and bone, swine, poultry, the treatment
of faeces of hens, treatment of lees of soy-been sauce, and vegetable protein,
drying of organic compounds, incineration of animal body, manufacturing of fish
oil, varnish and fats, industry related with the production of plastics, drying
of various organic solvents, rubber manufacturing plants and the production of
inorganic and organic chemicals. These processes are usually conducted in
small- and middle-sized industries and since these plants are located near
t
residential district they create: serious nuisances in many places. These
small- and middle-sized plants are concentrated in the outskirts of large cities
and people living in these areas have rather conservative point of view and their
relationship vith their neighbors are one of the characteristics of Japanese.
Such sense is different from the thinking of people in nev industrial cities
having petroleum industry. Thus the objections and petitions from people of old
industrial towns are less frequent despite the absolute concentration of the
odorous gases is in higher level. However, as their thinking is being changed
the incidence of odor in these areas gradually results in a social problem.
3. Reaction of people against odor
In Japan very few studies have been made on the dose-response relationship
in exposure to odor. In recent times the dose-response relationship is conceived
in the development of application of olfactory methods which are employed as one
of the method of measurement of odorous substances. The olfactory methods
include odor-free room, odor free room fitted with windows for sniffing,
obfactometer (Nader's method) and so on.
216 44
-------
In Japan the experimental studies of threshold values for olfactory
perception of primary odorous substances have been performed and one of them
will be shown in this paper as one example.
Dr. Matsushita of National Institute of Industrial Health made experimental
determination of threshold valurs of nine odorous substances for 15 students of
21 to 24 years old by means of 500 ml of vial. Fig. 1. shows one of his
experimental results. N-heptyl alcohol from 6.3 x 10~ to 8 x 10 ml/ml
in concentration is tested in his experiment. All fourteen subjects detect
-4
odorous above 10 ml/ml solutions of n-heptyl alcohol and their numbers of
subjects who can detect odorous decrease rapidly with the reduction of the
alcohol concentration. Finally three or four subjects only detects odorous
less than 10 ml/ml. The perception threshold value is determined to be
2 x 10~ ml/ml from the curve in Fig. 1.
In this way Matsushita established the population threshold values for
olfactoly perception of Japanese for primary odorous substances as shown in
Table 3.
These studies and the like are being progressed by Matsushita and several
other investigators and based on these investigations the effort has been
started for the determination of dose-response relationship among people living
in the district where there is an ordor problem. However no substantial results
have be gained so far.
4. Control of odor in Japan
Although no progress has been made of the investigations of odor a.nd its
related fields, as described above the odor easily results social problem, so
that local agencies made effort to evaluate the intensity of odor by means of
olfactory method and made application of the intensity scale to the technical
guidance of odor control. In the application of olfactory method usually only
-------
a fev professional panel members can be employed and thus layman has to be
incorporated as a panel member. These procedures are satisfactory for
administrative measure of local agencies to some extent. But as these
measures are not substantial, Japanese Government now presents the "lav for
abatement of odor" to the Diet.
The lav for abatement of odor is directed tovard the control of emission
of odorous substances resulting from the operations of plants and utilities.
The lav does not purpose to the control of autoexhaust emission. The lav
designates 13 gases such as ammonia and methyl mereaptan as those under control
and designates the area vhere it is enforced. It is further planned to establish
environmental and emission standards of the odorous gases. It seems to me that
the lav is directed tovard the educational effect rather than its strict
enforcement.
5. Conclusion
The general problems of odor in Japan are reviewed in the preceding sections.
In Japan the studies of odor vhich is currently at vork are exclusively those
of its measurement techniques and the health effect of odorous substances is a
subject vhich has to be studied in the future.
46
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Table 1. Trends of objections and petitions caused by eavircnnsnta
po^.^ ution anci nuisance in iiapan.
Year
Air pollution
Vater pollution
Noise
Vibration
Lr.nd subsidence
Ccl or
Industrial waste
Others
Total ' • .
4
O
7
1
3
20
Ku.v.oer
966
,962
,197
,640
,198
31
,494
-
9S5
,502
of petition
1967
5,621
3,014
10,752
1,453
41
5,073
-
1,634
27,5SS
s rec
1
r
3
10
1
5
1
23
eived V,
963
,343
,782
, 314 \
,796 J
41
,622
-
,572
,970
' Qcv
1
•t
4
17
7
2
40
ernr.-ont
969
r :.- O
,665
,756
13
, s*j^
175
,674
,S54
According to the statistics of
Ministry of Eor.e Affairs
Table 2. Gases vhich are designated as important odorous gases
in Jar,an.
Classification
! Sulfur-bearing compounds
Nitrogen-bearing compounds
Hydricarbons
Gas os
Methyl aereaptan
Ethyl rsercaptan
Dimethyl sulfide
Liethyl sulfide
Hydrogen sulfide
Dimethyl amine
Ethyl amine
Triaethyl anine
Anur.onia
Eutene
Butyric acid
Acetone
Acrolc-in
47
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C if
so-*
10-'
1. Relation between concentration of n-hcptyl alcohol in solution and number
of correct response by serial test (fourteen subjects):
Tnblc 3« Population threshold values for olfactory perception for pri.-nary odours.
Substances
jQdour quality
I
Threshold value* jConc
nccntratio
n odour
1 Cnt-.-.plior
! Cyclohcxanol
15-Mydroxy pcntadecanoic acid lactone
n-Hcptyl alcohol
Lina'.yl acetate
Cyclohcptanonc
SroiTioform
Phenol
Ethyl mcrcaptan
Methyl n-nonyl ketonc
c.imphoraceous
complioraccous
inusicy
flora!
floral
peppermint/
ethereal
pungent
putrid
rancid
1.2x10-*
l.GxlO-'**
2.7x10"**
2.0x10-=
1.0x10-'**
l.SxlO"1
5.3xlO-«
1.5x10-'**
3.3xlO-»
5.0x10-'**
1.2 xlO-«
1.22x10-'**
2.4 xlO-'**
1.75x10-'
1.12x10-'**
1.2 xlO"
5.4 xlO-«
S.3 xlO-«**
2.-'.5xlO-»
4.-1 xlO-'**
* Unit used is as g/inl for 15-r.ydroxy pcr.tudccanoic acid lactonc and p
** Mean of two observed values.
48
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ADMINISTRATIVE MECHANISMS AVAILABLE FOR CONTROL OF ODOROUS
COMPOUNDS UNDER THE U.S. CLEAN AIR ACT AS AMENDED
by
D. S. Earth, Ph.D.
Environmental Protection Agency
Air Pollution Control Office
Bureau of Air Pollution Sciences
To be presented at the Conference on The Dose-Response Relationships
Affected Human Reactions to Odorous Compounds. Sponsored by the
Environmental Protection Agency, Air Pollution Control Office,
April 26-27, 1971, Cambridge, Massachusetts.
61
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Administrative Mechanisms Available for Control of Odorous
Compounds under the U.S. Clean Air Act as Amended
D. S. Barth
Introduction
The Clean Air Act as amended, P.L. 91-604, states as one of its
purposes, "to protect and enhance the quality of the Nation's air
resources so as to promote the public health and welfare and the productive
capacity of its population." It goes on to define specific authorities
granted to the Administrator, Environmental Protection Agency, which he
may utilize to achieve the purposes of the Act. In brief some of these
authorities are:
1. Designation of Air Quality Control Regions, issuance of Criteria
and Control Techniques Documents and promulgation of National Ambient
Air Quality Standards.
2. Promulgation of National Standards of Performance for New
Stationary Sources
3. Promulgation of National Emission Standards for Stationary Sources
of Hazardous Air Pollutants
4. Promulgation of National Emission Standards for Motor Vehicles
5. Regulation of fuels and fuel additives
6. Issuance of National Aircraft Emission Standards
7. Setting of Aviation Fuel Standards*
In the following a brief discussion of each authority will be given
with emphasis placed on the possible applicability to the control of
odorous compounds.
*This authority is granted to the Administrator, Federal Aviation
Administration, but it must be based on recommendations of the
Administrator, EPA.
63
223
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General Discussion of Information Needs to Develop Adequate Controls
for Any Air Pollutant
In genral adequate information must be available in the following
subject areas in order to establish a basis for control of any air
pollutant:
1. Effects
2. Sources
3. Measurement techniques
4. Control technology
Effects information should include adverse effects on human health or
welfare as a function of pollutant concentrations and averaging times
and as modified by meteorological factors, presence of other pollutants
and sensitivity of the exposed receptors. All significant sources,
both stationary and mobile must be identified. Adequate measurement
procedures of known precision and accuracy must be available for both
source emissions and ambient air quality. And finally control technology
must be available and possible control efficiences must be known for
control of most, if not all, significant sources.
When the information described briefly above is available then it
becomes possible to develop a strategy to bring a given air pollutant
under adequate control. The selection of a specific strategy for control
should take into consideration the following factors:
1. Available authorities for control which are applicable.
2. Controlling the objectionable pollutant to acceptable levels
at the earliest possible time.
64
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3. Total administrative and operational costs associated with
different approaches.
Odorous Compounds as a Special Case
The special case of odorous compounds as air pollutants must now
be considered. Of the authorities for control of air pollutants cited
previously some are not applicable for odorous substances. In particular
the effects of odorous substances are not deemed to meet the definition
required to qualify odorous substances as "hazardous air pollutants."
Furthermore there is no evidence now to indicate that regulation of
fuels and fuel additives or setting of aviation fuel standards would be
necessary to abate objectionable odors. No further discussion will
be given of the cited control options which are not judged to be
applicable to the control of odorous substances. The remaining control
options, all of which may be applicable, will now be discussed in more
detail.
Criteria and Control Techniques Documents
The Administrator, EPA, is directed by P.L. 91-604 to publish Criteria
and Control Techniques Documents for those air pollutants
"(A) which in his judgment have an adervse effect on public health
and welfare;" and
"(B) the presence of which in the ambient air results from numerous
or diverse mobile or stationary sources."
Air quality criteria for an air pollutant "shall accurately reflect the
latest scientific knowledge useful in indicating the kind and extent
of all identifiable effects on public health or welfare which may be
expected from the presence of such pollutant in the ambient air, in
65
225
-------
varying quantities." Information on control techniques "shall include
data relating to the technology and costs of emission control. Such
information shall include such data as are available on available
technology and alternative methods of prevention and control of air
pollution." The Act states that "effects on welfare include, but are
not limited to, effects on soils, water, crops, vegetation, man-made
materials, animals, wildlife, weather, visibility, and climate, damage
to and deterioration of property, and hazards to transportation, as well
as effects on economic values and on personal comfort and well-being."
For those materials for which Criteria and Control Techniques
Documents are issued the Administrator is directed to prescribe National
Primary and Secondary Ambient Air Quality Standards which are defined
as follows:
(1) "National primary ambient air quality standards shall be ambient
air quality standards the attainment and maintenance of which in
the judgment of the Administrator, based on such criteria and allowing
an adequate margin of safety, are requisite to protect the public
health."
(2) "National secondary ambient air quality standards shall specify
a level of air quality the attainment and maintenance of which in
the judgment of the Administrator, based on such criteria, is
requisite to protect the public welfare from any known or anticipated
adverse effects associated with the presence of such air pollutant
in the ambient air."
66
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To date Criteria and Control. Techniques Documents have been issued
and National Primary and Secondary Ambient Air Quality Standards have
been proposed for sulfur oxides, particulate matter, carbon monoxide,
photochemical oxidants, hydrocarbons and nitrogen oxides. Once these
standards have been promulgated, which must be no later than April 30,
1971, the States have nine months in which to develop and submit an
implementation plan designed to achieve the air quality standards within
a rather tight time schedule after approval of their plan--3 years after
approval for primary standards and a "reasonable time" for secondary standards.
From the discussion above it is clear that this control option
would be feasible and applicable for odorous substances. In other words
we could prepare and issue Criteria and Control Techniques Documents for
Odorous Substances and then subsequently promulgate National Ambient
Air Quality Standards which would lead to implementation plans for
control. The advantages and disadvantages of this approach will be
addressed later.
Standards of Performance for New Stationary Sources
"The term 'standard of performance' means a standard for emissions
of air pollutants which reflects the degree of emission limitation
achievable through the application of the best system of emission
reduction which (taking into account the cost of achieving such reduction)
the Administrator determines has been adequately demonstrated." On a
tight time schedule set forth in the Act the Administrator is required to
list and then publish standards for categories of new sources which he
determines "may contribute significantly to air pollution which causes
or contributes to the endangerment of public health or welfare."
67
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In addition the Act stipulates that the Administrator shall prescribe
regulations which shall establish a procedure under which each State
shall submit to the Administrator a plan which establishes emission
standards for any existing source in the same category of sources for
any air pollutant which is a non-criteria pollutant and which has not
been listed as a hazardous air pollutant, and to which a standard of
performance would apply if the existing source were a new source.
Placing categories of industrial sources of odorous substances
on the list and then publishing standards of performance for such new
sources would lead to control of both new and existing sources through
i
the application of the best system of emission reduction which has been
adequately demonstrated. Some advantages and disadvantages of this
option will be presented later.
National Emission Standards for Motor Vehicles and Aircraft
For these authorities it is envisioned that control needs will be
based on desired air quality for significant pollutants to assure
protection of health and welfare. To the extent that odorous substances
are emitted from motor vehicles and aircraft this is the only applicable
authority for control. This authority can and would be used in conjunction
with whatever controls are established for stationary sources of odorous
compounds.
Discussion of Alternate Control Options
For the control of stationary sources of odorous air pollutants
there are two possible approaches as indicated previously. Criteria and
Control Techniques Documents could be issued or Standards of Performance
68
Ł28
-------
for new sources and in turn emission standards for existing sources
could be promulgated. There are advantages and disadvantages inherent
to either approach. A major problem to either approach is the lack
of availability of an objective measurement technique for the wide
variety of odors which are objectionable to many humans. Proceeding
via the Criteria Document route would lead to obtaining some control
over all sources simultaneously. However, since the National Ambient
Air Quality Standards would probably be secondary rather than primary
ones, achievement of the standards could be delayed for a "reasonable
time," whatever that time might be. This approach would also require
the development of a nationwide air quality surveillance system to
measure odorous air pollutants. In addition the built-in delays in
proceeding from development of criteria documents to achievement of
ambient air quality standards might delay the starting time by which
odorous pollutants could be placed under control.
The use of the"Standards of Performance" control option has the
advantage of requiring the use of best adequately demonstrated control
technology regardless of any air quality considerations. Thus there
is no requirement for nationwide air quality surveillance networks.
This approach would lead to the earliest control for the most objectionable
sources of odorous air pollutants. One of the disadvantages is the fact
that it would take many years to bring all sources under control because
not all categories of sources can be listed at one time. Also, particularly
for some existing sources, the best adequately demonstrated control
technology may not be adequate to abate the citizen complaints.
69
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At this point in time we are leaning toward the use of the
Standards of Performance route. Hopefully information presented
i
and developed at this symposium will assist us in coming to a firm
decision as to the best control option for control of odorous air
pollutants from stationary sources. For control of these materials
from mobile sources we can proceed in a clearcut fashion as soon as the
technology has been developed for measuring the emissions precisely
under an adequate testing procedure. Also the controls for mobile
sources may be set stringently enough to insure protection of the
public welfare from objectionable odors.
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