United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/ 5-80-003
February 1980
Air
Regulatory Options
for the Control
of Odors
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EPA-450/5-80-003
Regulatory Options for
the Control of Odors
by
George H. Wahl, Jr.
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
February 1980
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TABLE OF CONTENTS
Chapter
Page
1-0 EXECUTIVE SUMMARY -j
T-1 Introduction 1
J-2 Survey of State and Local Regulations ! 2
1-3 Clean Air Act Regulatory Strategies .... '3
1 -4 Recommendations [ 4
1.5 Conclusions ..'.".'.'.'.'. 5
2.0 INTRODUCTION 6
3.0 SURVEY OF ODOR REGULATIONS 7
4-0 EVALUATION OF STATE AND LOCAL ODOR REGULATIONS SIMILAR
IN FORM TO THOSE THAT COULD BE PROMULGATED UNDER THE
CLEAN AIR ACT 16
4.1 General Considerations '. ie
4.2 Available Clean Air Act Regulatory Strategies for
Odor Control 16
4.3 Comparison of Ambient and Emissions-Based Regulatory
Approaches 20
4.4 Local Programs Studied 21
4.5 Criteria for Determining Regulatory Effectiveness 21
4.6 Ambient Approaches' 24
4.6.1 The Objectionability Approach 24
4.6.2 Ambient Sensory Regulations 26
4.6.3 Odorant-Specific Ambient Standards 28
4.7 Emission-Based Approaches 30
4.7.1 The Odor Level Standards Approach 31
4.7.2 Incineration Standards 33
4.7.3 Performance Standard 36
4.8 Combined Ambient-Stack Approaches 37
4.8.1 Minnesota 38
4.8.2 The Bay Area Air Quality Management District . . 40
4.9 Summary and Conclusions 43
5.0 ADVANTAGES AND DISADVANTAGES OF ALTERNATIVE ODOR
CONTROL STRATEGIES UNDER THE CLEAN AIR ACT .... 47
5.1 National Ambient Air Quality Standards 49
5.1.1 Statutory Overview 49
5.1.2 The Listing Process 50
5.1.3 Establishing Ambient Standards 54
5.1.4 implementation Administrative Considerations ,. . 58
5.2 Federal New Source Performance Standards 60
5.2.1 Statutory Overview 60
5.2.2 Impact of the 1977 Clean Air Act Amendments . . 67
5.3 Conclusions 68
6.0 GENERAL CONCLUSIONS 69
REFERENCES 73
APPENDIX Conclusions of the National Academy of Sciences
Regarding Odor Measurement '5
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1.0 EXECUTIVE SUMMARY
1.1 Introduction
This report is the response of the Environmental Protection Agency (EPA)
to Section 403(b) of the 1977 Clean Air Act Amendments (P.L. 95-95), which
requires a study of the effects of odors and odorous emissions on public
health and welfare and an analysis of strategies or authorities available
or appropriate under the Clean Air Act for abating such emissions. The
report is composed of two sections paralleling the twofold nature of
Section 403(b). Under contract to EPA, the National Academy of Sciences
prepared a study of
" the effects on public health and welfare of odors or odorous
emissions, the sources of such emissions, the technology or other
measures available for control of such emissions and the costs of
such technology or measures, and the costs and benefits of alter-
native measures or strategies to abate such emissions."
On the basis of that report, EPA then prepared a second document (the present
report), which contains
11 an evaluation of whether air quality criteria or national
ambient air quality standards should be published under the Clean Air
Act for odors, and what other strategies or authorities under the
Clean Air Act are available or appropriate for abating such emissions."
This EPA report also surveys current State and local odor regulations,
evaluates the effectiveness of regulations similar in form to those that
might be promulgated under the Clean Air Act, and then discusses the advantages
and disadvantages of alternative Clean Air Act regulatory strategies. The
NAS Study is summarized in the Appendix to the present report, and a com-
plete copy of the NAS document accompanies this report.
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2
1.2 Survey of State and Local Regulations
State and local regulations vary considerably but can be divided into
nine general categories including:
- no specific regulation (i.e. common law)
- nuisance regulations
- emission standards
- ambient standards.
The nuisance approach remains the most widely employed strategy and virtually
all regulatory programs continue to rely upon citizen complaints for enforce-
ment purposes. Most agencies currently assign low priority to odors as a
candidate for new federal regulation because of the great pressures produced
by the revisions of state implementation plans (SIP's) mandated by the
1977 Clean Air Act Amendments and because odors are not perceived as a threat
to public health. The combination of citizen/agency pressure and
threatened legal action is generally sufficient to encourage problem sources
to undertake voluntary compliance and abatement programs.
The majority of odor problems (as judged by citizen complaints) are
attributable to a relatively small number of source categories (such as
agricultural and livestock operations, diesel exhaust, incinerators, etc.).
Thus, any regulatory strategy that might be devised should probably be
focused on these source categories to maximize efficiency. Reactions to
odor depend heavily, however, on local values and individual aesthetic judgments.
The absence of any meaningful data that relate ambient odor levels (or
odorant concentrations) to community annoyance levels will likely frustrate
any attempts to establish general nationwide ambient odor regulations for
the foreseeable future. Indeed, since odor perception is quite subjective,
nuisance law, initiated by citizen complaints, appears to be an appropriate
mechanism for dealing with odor problems.
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3
1.3 Clean Air Act Regulatory Strategies
Under the Clean Air Act, there are basically four different regulatory
strategies available for the control of odor pollution:
1. National Ambient Air Quality Standards (Sections 108-110)
2. New Source Performance Standards (Section 111)
3. National Emission Standards for Hazardous Air Pollutants (Section 112)
4. Motor Vehicle Emission Standards (Section 202).
Since a hazardous air pollutant is defined as one capable of causing or
contributing to an increase in mortality or serious illness, Section 112
appears to be an inappropriate regulatory approach for odors. Thus, the
available strategies are reduced to three, ambient standards (Section 108-110),
stationary source emission standards (Section 111), and mobile source emission
standards (Section 202). A 1978 statement of the Air Pollution Control
Association Odor Committee (APCA TT4) well summarizes the essence of the
problem of choosing between ambient and emission-based strategies:
"Both approaches have strengths and weaknesses. The stack emission
approach has obvious advantages over an ambient odor type regulation
regarding the relative ease and lower costs of sampling and analyzing
odors. Also, the emission source of objectionable odors is more
readily determined by using stack measurements. However, the stack
emission type approach requires an additional technical step - the
correlation of stack emission with ambient odor concentration, either
by obtaining empirical data or by use of atmospheric dispersion models,
in order to be able to judge whether or not the resulting ambient odor
concentration is acceptable to the community.
On the other hand, if odor annoyance threshold data are available,
an ambient odor limit can be related to a particular zoned area and
specified to avoid an odor annoyance being experienced by the population
that lives or works in a particular zoned area. Further, it should be
recognized that odors do not discharge only from stacks or well-defined
enclosures but could originate from fugutive type emissions (i.e.
anaerobic lagoons). As a result, it may be necessary in certain areas
to have a combination of stack emission and ambient odor regulations
available to control all significant sources of odor."
While emission standards appear to offer more promise than ambient
standards as a federal odor control strategy, technical difficulties still
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4
exist. The fundamental problem is that application of best available
control technology does not guarantee that community odor annoyance levels
will not be exceeded. This problem becomes even more complicated when
fugitive odor sources such as lagoons are involved or when multiple odor
sources are. located in close proximity to one another. These problems
make it nearly impossible to predict the odor reduction potential of any
given abatement program.
1.4 Recommendations
Although there are problems inherent in any regulatory control program
for odors, there are a number of specific recommendations which could
improve the effectiveness of these regulations:
1. The existence of a community odor nuisance should be established
before limits are applied to a specific odor source.
2. The relationship between ambient odor levels (or odorant concen-
trations) and odor annoyance thresholds for different communities
or zoned areas must be determined prior to establishing ambient odor
type standards. This step might be accomplished by determining both
the dose-response relationships that equate community annoyance with
odor intensity and the degree of unpleasant character of a particular
odor. However, for some odorants such relationsips may be impossible
to develop.
3. The Scentometer and ASTM syringe methods currently used by state
and local agencies are considered to be inadequate for regulatory
purposes. There is a basic need for odor sensory methods that are
capable of measuring odors objectively and reliably, the results of
which can be related to community annoyance.
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1.5 Conclusions
In conclusion, federal regulatory involvement in odor control does
not appear to be warranted. This conclusion is based on the following
considerations:
1. Odors are not caused by a single pollutant* but rather are a
subjective effect which may result from different combinations of
numerous odorants. Thus, it is very difficult to associate any
specific health or welfare effect to a given "odor concentration".
As a result, the available data are not sufficient to support the
establishment of a primary or secondary ambient air quality standard
for odors.
2. Other problems which limit or preclude setting of national ambient
air quality standards for odors or developing State Implementation
Plans for odors include:
a. Techniques used to measure odors are considered generally
inadequate for regulatory purposes.
b. Reliable procedures for relating ambient odor levels to the
extent of community annoyance do not exist.
c. Community tolerances or odor annoyance levels vary widely.
3. Use of best control technology for new or existing sources of
odors under section 111 of the Act also has problems:
a. It would require best controls nationwide, even though a source
type may be a problem only in certain areas or situations.
b. It does not guarantee that community odor annoyance levels
will not be exceeded, especially where fugitive odor sources
are involved or when multiple odor sources are located in
close proximity to one another.
c. Assessing and/or regulating all odor source categories would
require an inordinate expenditure of Federal, State, and local
control agency resources which are already fully extended to
meet other Clean Air Act requirements.
4. Local and state odor control procedures appear to be generally
adequate and are probably more cost effective than a uniform
national regulatory program under the Clean Air Act.
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2.0 INTRODUCTION
This report is submitted in response to Section 403(b) of the 1977
Clean Air Act Amendments (P.L. 95-95). That section required the EPA
to study and report to Congress on the technical and regulatory dimensions
of odor control.
This report consists of two sections
Sect1on ]- The effects on public health and welfare of odors and odorous
emissions, the sources of such emissions, available control
technologies or methodologies, together with associated
costs, and the costs and benefits of alternative abatpment
strategies.
Section 2. An evaluation of whether air quality criteria or national
ambient air quality standards should be published for odors
under the Clean Air Act, and an evaluation of what other
Clean Air Act strategies or authorities are available or
appropriate for abating odor emissions.
Section 1 has been prepared for EPA by the National Academy of Sciences1
and is attached to this document.
Section 2 consists of several parts:
- A survey of current State and local odor control regulations;
- An evaluation of the effectiveness of selected State and local
odor control regulations most similar in form to regulations that
could be promulgated under the Clean Air Act;
- An analysis of the advantages and disadvantages of the three basic
regulatory options (NAAQS, NSPS, NESHAP) for controlling odors
available for federal use under the Clean Air Act.
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7
3.0 SURVEY OF ODOR REGULATIONS
From a conceptual standpoint, existing State and local odor control
regulations can be divided into nine general categories. A 1974 odor regulation
survey of all state and selected local air pollution control agencies was
published in the May, 1974 edition of the Journal of the Air Pollution Control
Association using this nine-category format.3 EPA has updated this 1974
survey, the results of which are summarized in Table I.4 The regulatory
categories include:
1. NO Specific Regulation - Although many jurisdictions have no specific
odor control regulation, common law public or private nuisance con-
tinues as an available remedy for odor pollution problems.
2. Nuisance Regulation - These regulations codify the traditional
nuisance concept, enabling public prosecution of cases that would
have otherwise been left to private litigants.
3. Qb.iecti onabilitv Criteria - This regulatory strategy is triggered
when an odor is either complained of or deemed objectionable by a
specified number or percentage of individuals. The only real
difference between the objectionability criteria and a nuisance
regulation is that, in the former, the criteria for establishing
a violation are listed whereas, in the latter, they are not.
4. Ambient Sensory Approach - A Scentometer or other device is used
to measure the "strength" of an odor by diluting odorous air with fil-
tered odor-free air. The greater the dilution necessary to render an
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TABLE 1. STATE AND SELECTED LOCAL
ODOR CONTROL REGULATIONS
State/local agency
Alabama
Alaska
Arizona
Arkansas
California
oay Area*
South Coast
Colorado
Connecticut*
Delaware
O.C.
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa*
Kentucky*
F.ansas
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota*
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Mexico
New Jersey
New York
North Carolina
North Dakota*
Ohio
Oklahoma
Oregon*
Pennsylvania*
Puerto Rico
Rhode Isl-nd
boutn care >na
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
HisconslTV '
Wayne County*
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Objectionabilityj
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Ambient sensory j
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Incineration or
equivalent/
Performance
Standard
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Sensory emission)
std.
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Odorant-specif iq
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Policy statement!
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Applicable
regulatory
section
l.ll (b.4J)
8 AA (50.
110, 50.060)
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B?-193fi Stale
Laws
Div 26, PT47
§41700
Reg. 12
19-508-23 "
Ren. IXIX
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Sections K,
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Rules 102,
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401 KAR 3:020
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Reg. 19
R. 336. 46
10 CSR 10-
3.090
§15-2.14(1)-
S1480
CH. 33-15-16
PRT8
Reg. No. 17
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Changes
s i nee
1974
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Relative
agency
priority
LOW
Low
A County natter
Low
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Moderate
Moderate
Low
Important
Low
Low
Low
Low
Low
Low
Increasing
Moderate
tow
Low
Moderate
Low
"Moderate
Important
Moderate
~ Low
low
Moderate
Low
Low
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Important
Low
Increasing
Low
Low
Moderate
Low
Increasing
Increasing
Low
Low
Low
Moderate
Moderate
Low
Moderate
Moderate ~
*Selected for in-depth review in this report
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9
odorant undetectable, the greater its "strength." Scentometer-
based regulations are premised upon very limited experimental
evidence, indicating that ambient odors above 7 "dilutions to
threshold"* will probably cause complaints, while those above 31
can be described as serious nuisances if allowed to persist for
3
even a short time. This approach applies to all odors, regardless
of their "object!onability" and is limited to ambient air (as
opposed to stack) measurements.
5. Control Technology-Based Regulations - Several states approach odor
control regulation by requiring specified odor sources to install
and use "best practical controls." Such control requirements are
typically phrased in terms of an incineration, or equivalent, stan-
dard and are not directly related to community odor levels.
6. Sensory-Based Source Emission Standards - Five jurisdictions (see
Table 1) impose source emission standards for odors measured 1n
terms of the odor "concentration" in the stack gas stream. With
this approach, a stack gas sample 1s collected and applied to a
random panel of individuals. These panel samplings are used to
determine the "dilution to threshold" or D/T of the emission, which
is phrased in terms of "odor units per cubic feet." In Connecticut,
for example, odor source emissions are limited to 120 "odor units
per cubic foot."5 This means that, after diluting any sample of the
emission stream to 120 times its volume by odor-free air, only
*The term "dilution to threshold" refers to the amount of pure air which
must be added to a known volume of odorous air in order to dilute the sample
to the concentration at which it can just be detected.
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10
50 percent of the panel members would detect the odor from
the diluted sample. The presumption is that natural atmos-
pheric dispersion mechanisms will reduce a stack emission at
least 120 times to a concentration below the detection threshold
by the time it becomes fully mixed with the ambient air at the
receptor.
7. Qdorant-Specific Emission or Ambient Standards - One of the most
promising odor control strategies, in terms of its adaptability to
the Clean Air Act, establishes odorant-specific emission and/or
ambient standards. Several state and local agencies, (as well as
EPA) for example, have established source emission rules governing
total reduced sulfur (TRS) emissions from kraft pulp mills. Other
agencies have adopted specific ambient air quality standards for
hydrogen sulfide (H,,S). From a federal odor control standpoint,
the promise of these strategies is that the Clean Air Act is more
easily applied to the regulation of specifically identifiable
substances than it is to controlling an amorphous perceptual
concept such as "odor."
8. Policy Statements - Two states, Delaware and Virginia , have
regulations that are, in effect, statements of agency policy
against air pollution that results in odor. These regulations
are similar in many respects to nuisance regulations.
9. Combination of Ambient and Source Standards - A few agencies,
8 9 10
including the Bay Area, Illinois, and Minnesota, combine the
ambient and emission standard approaches to odor control. Illinois,
for example, employs an ambient scentometer regulation as well as
an incineration requirement (for rendering plants) in its odor
control regulations.
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11
As indicated in Table 1, few State and local odor control regulations
have undergone any significant revisions since 1974. The nuisance approach
remains the most widely employed strategy, and virtually all regulatory
programs continue to rely upon citizen complaints for enforcement purposes.
Furthermore, odor control regulations are assigned a low priority by
most air pollution control agencies since odors are perceived as
nuisances (i.e., welfare effects) rather than as a health concern. In
addition, the unprecedented impact of the state implementation plan revisions
called for by the 1977 Clean Air Act amendments further minimizes state and
local agency concern for new federal odor control regulations. The prepara-
tion, adoption and enforcement of these revised implementation plans will
consume the large majority of available State and local air pollution control
resources during the forseeable future.
The current thinking of most state air pollution control agencies is to focus
their odor-related efforts on those sources, typically few in number, causing
the majority of citizen complaints. In most states, a relatively limited number
of source categories are responsible for the large majority of citizen complaints.
The odor sources that are most frequently the cause of complaints include:
- Pulp mill/kraft mi 11/wood products
- Land fin/dump/open burning
- Fruit and vegetable processing
- Fisheries and fish processing facilities
- Petroleum and natural gas refining/asphalt production
- Rendering/meat packing/slaughter houses/tanneries
- Fertilizer plants
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- Sewage/human waste
- Feedlots/stockyards
- Incinerators
- Coffee roasting/spices
- Commercial-restaurant/dry cleaning
- Paint/.varnish/lacquer
- Coating applications (paint coating, baking and drying)
- Diesel (and other mobile source) exhausts
State and local enforcement actions against specific problem plants
in these general categories have been a frequent occurrence in the past and
are certain to continue in the future. This is particularly true for state
and local agencies which view odor problems as a relatively high enforcement
priority. The most active jurisdictions in this enforcement area include:
The South Coast and Bay Area Districts in California; Delaware; Massachusetts;
Michigan; Wayne County, Michigan; Minnesota; New Jersey; Rhode Island; Texas;
and, Washington.
Several conclusions can be drawn from this regulation survey. The
most striking one is that, while most jurisdictions experience many odor
problems,* few rank them as one of their top agency priorities. Most
officials believe that, while existing regulatory approaches need to be
improved, they are generally adequate to solve major community odor problems.
The combination of citizen/agency pressure and threatened legal action is
*Surveys reveal that as many as one half of all air pollution complaints
relate to odor. This high proportion is undoubtedly due to the perceptual
nature of the problem, however, and does not mean that odor pollution is the
most serious air pollution problem. People know when they do not like a
particular odor. They may not know when they are being harmed by more subtle
forms of air pollution such as carbon monoxide (CO).
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13
generally sufficient to encourage problem sources to undertake voluntary
compliance and abatement programs. Indeed, the vast majority of odor
problems are resolved extra-judicially. Only in relatively rare cases of
strong community pressure and stiff industry resistance do these matters
require an adjudicatory resolution. In those cases in which a court
action is indicated, the regulatory procedures used by Texas have proven
very effective.
Another important conclusion is that most odor problems (measured in
terms of citizen compliants) are attributable to a relatively few source
categories. This conclusion is very significant in terms of regulatory
strategy development since it makes it possible to devise narrowly focused
control programs with relatively high cost-benefit ratios. Specifically,
if odors could be controlled from pulp and kraft mills, rendering plants,
sewage treatment plants, meat packing and processing operations, feedlots,
painting operations and a few selected chemical processes, many of the
nation's odor problems would be solved. While this statement has a
simplistic ring, it does lead to a tentative conclusions that emission
(as opposed to ambient level) controls may be a more effective regulatory
strategy for odors.
Regulating odor presents many problems, regardless of the air
pollution control strategy employed. Technical uncertainties are legion and
varying perceptions of and social attitudes toward odor tend to undermine any
national or uniform regulatory strategy. Clearly, from a regulatory standpoint,
the most difficult problem, is the absence of meaningful data that relate
emission rates or ambient odor levels to community annoyance. In the final
analysis, it is the elimination of community annoyance that ought to form
the policy basis of odor regulation. Without reliable annoyance threshold
data for specifically identified odorants, it is very difficult to devise
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14
odor-control regulatory strategies that are grounded on this fundamental
base. Ambient standards tied to "detection" or "recognition" thresholds
are generally inadequate because they do not necessarily relate to the
annoyance property of the odorant within the context of the community
setting in which the odor is normally experienced. This lack of a close
relationship can lead to violations even though no nuisance condition
exists.
The irony of the situation is that efforts to establish quantified
acceptability or annoyance threshold levels for any particular odorant
are fraught with subjective evaluations. Subjective reactions to odor
differ between individuals and between communities. Indeed, this factor
is a major reason for the view that nuisance law is an appropriate mechanism
for addressing odor problems. Despite all of its substantive, procedural
and evidentiary shortcomings, the nuisance approach is the only odor-
regulation strategy now in use that is tied directly to the basic criterion
of an unreasonable interference with public or private rights.* As in
other areas of nuisance law, odor nuisance disputes are resolved on the
basis of lay testimony concerning the reasonableness of the defendant's
*A public nuisance is created when the defendant's conduct invades
a right common to all members of the public, such as the right to enjoyment
of a park. A private nuisance, on the other hand, involves an invasion
of a private party's interest in the use and enjoyment of his land. Since
the Clean Air Act does not explicitly preempt the field of odor regulation,
the two types of nuisance action would remain valid avenues for seeking
abatement of unpleasant odors, even if ambient standards ^reestablished
under that Act and the defendant was in compliance with them.
Under the most widely recognized view, an odor problem must cause
substantial annoyance to qualify as a nuisance. Unusually sensitive in-
dividuals are at a distinct disadvantage since annoyance is judged on the
basis of the ordinary person living in that locality. Technica legal defenses
and burdensome evidentiary problems also detract from the usefulness of nuisance
actions and in most cases courts will not issue prohibitory2injunctions
even if the plaintiff prevails on the merits of his claim.
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15
behavior. The level of private or public annoyance is balanced against
the defendant's interests in continuing to operate. Numerically based
odor control approaches (ambient and source) lack this important feature.
This is their basic shortcoming.
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16
4.0 EVALUATION OF STATE AND LOCAL ODOR REGULATIONS SIMILAR IN FORM TO
THOSE THAT COULD BE PROMULGATED UNDER THE CLEAN AIR ACT!
4.1 General Considerations
In judaing the effectiveness of any odor regulations, few established
guidelines exist. Presumably, the ideal regulation will prevent, reduce
or eliminate community annoyance at minimum cost without introducing any
significant new risks. Since annoyance, cost and "risk" are seldom
measured in the same units, a direct comparison among them is difficult,
and a simple numerical goal for effectiveness is not possible. Further-
more, secondary benefits of odor regulation, such as a general reduction
in the number and quantity of pollutants inhaled by the population at
large, an increase of real estate values, or improvement of corporate
image, are even more difficult to quantify in similar units. They
nevertheless are potential real secondary benefits of odor reduction.
Since the objective of this section is to evaluate the effectiveness
of those existing state and local odor control regulations amenable to
promulgation under the Clean Air Act, it is necessary to analyze the
types of regulations available under the Act. Section 4.2 describes the
regulatory options available.
4.2 Available Clean Air Act Regulatory Strategies
According to the Clean Air Act, four basic regulatory mechanisms
may be used for controlling emissions to the atmosphere:
(1) Ambient Air Quality Standards (Sec. 108-110).
(2) New Source Performance Standards (Emission Standards) (Sec. 111).
(3) National Emission Standards for Hazardous Air Pollutants (Sec. 112).
(4) Motor Vehicle Emission Standards (Sec. 202).
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17
The first option involves the establishment and attainment of
national ambient air quality standards. Under this approach, EPA
promulgates specific numerical ambient standards for specified (criteria)
pollutants designed to protect public health (primary ambient standards)
and public welfare (secondary standards). The Act delegates to the
States the primary responsibility for attaining and maintaining these
standards through the adoption and enforcement of State implementation
plans (SIPs). For any given criteria pollutant, the SIP must set forth
emission limitations and other control measures necessary to attain end
maintain compliance with the ambient standards within the time established
by the Act. The plans must also contain well defined procedures for
preventing significant air quality deterioration resulting from major
new emission sources in areas already cleaner than the standards.
The second available approach is through the promulgation cf industry-
specific new source performance standards.39 Section 111 of the Act
gives EPA the authority to establish standards of performance applicable
to specific pollutants from new and modified* stationary sources. This
provision recognizes that it is more practical to build pollution control
into a new facility than to retrofit controls into an existing operation.
New source performance standards require emission reductions that reflect
that level of control achievable through application of:
*A "modified" source is one that undergoes a physical or operational
change which causes new or increased air pollution. A "new" source is one
which commences construction after NSPS regulations applicable to that source
category are proposed by EPA.
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18
"...the best technological system of continuous emission reduction
which (taking into consideration the cost of achieving such emission
reduction, any non-air quality health and environmental impact and
energy requirements) the Administrator determines has been adequately
demonstrated."
Before promulgating new source performance standards, EPA conducts
tests of prototype and full-scale control, systems, surveys pertinent
literature, and documents manufacturer guarantees. These efforts are
required in order to identify appropriate control systems which have
been adequately demonstrated and which will be available in time to
allow compliance by the affected industry.
Once the standard is set, the owner or operator need not use the
control system identified by EPA, but the standard must be achieved. Normally,
installation and operation of a particular control system is not enough; com-
pliance is based on actual emissions. Only where it is not feasible for EPA
to establish a numerical emission standard (e.g., petroleum storage vessels),
/
may the agency establish NSP? requiring specified design or control techniques.
In all other cases, the standard must reflect a quantified level or percentage
reduction of emissions from the control system.
In addition to requiring performance standards for new and modified
stationary sources, Section 111 also requires the states to adopt performance
standards for "designated pollutants" from certain existing sources
under Section lll(d). A "designated" pollutant is one which is subject
to an NSPS but which has not been listed as "hazardous" under Section 112 of
the Act or which is not listed as a Criteria Pollutant under Section 108.
If EPA promulgates an NSPS for a designated pollutant from new sources of
a specific source category, an emission standard must be established by the
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19
states governing emissions of that designated pollutant from all existing
sources within the category. Fluorides from phosphate fertilizer and
aluminum plants, sulfuric acid mist from acid plants, and total reduced
sulfur compounds from pulp mills have been regulated under Section lll(d).
Any standards applicable to odors under the NSPS program would qualify as
"designated pollutant standards," thereby triggering existing source controls
under Section 111(d).
Section 112 of the Clean Air £ct authorizes EPA to promulgate national
emission standards for new and existing sources of "hazardous air pollutants".
The Act defines these pollutants as those capable of causing or contributing
to an increase in mortality or serious illness. To date, EPA has used Section
112 sparingly, reserving it for the regulation of extremely dangerous pollutants
such as mercury, asbestos, beryllium and vinyl chloride. Given the present
uncertainty regarding the public health effects of odors, it seems quite
doubtful that EPA could promulgate a defensible hazardous emission standard
for the control of specific odorant or for odors generally. The potential
advantages and disadvantages of this regulatory strategy will, therefore, not
be analyzed further in this report.
In addition to the basic NSPS authority under Section 111, EPA is
also empowered by Section 202 of the Clean Air Act to establish standards
applicable to emission of any air pollutant from new motor vehicles or
new motor vehicle engines. Conceptually these standards may be thought of
as a special type of new source performance standard. They are intended
to apply to vehicles or engines throughout their useful lives and to take
effect after such period as the Administrator finds necessary to permit the
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development of the requisite technology, giving appropriate consideration
to the costs of compliance. The basic process for establishment of standards
under Section 202 applicable to odors originating from motor vehicles would
be comparable to that described above with respect to Section 111.*
4.3 Comparison of Ambient and Emission-Based Regulatory Approaches
The national Air Pollution Control Association (APCA) has a standing
committee (the APCA TT4 Odor Committee), charged with review of basic odor
control technology and regulation. Many of its members have contributed
technical articles on odor regulations in recent years. After criticelly
reviewing odor control regulations, the APCA Odor Committee was equally
divided on the issue of selecting stack ("emission") as opposed to
ambient type standards for odors. The following excerpt from the Committee's
2
1978 Report highlights the essence of the debate.
"Both approaches have strengths and weaknesses. The stack emission
approach has obvious advantages over an ambient odor type regulation
regarding the relative ease and lower cost of sampling and analyzing odors.
Also, the emission source of objectionable odors is more readily determined
by using stack measurements. However, the stack emission type approach
requires an additional technical step - the correlation of stack emission
with ambient odor concentration, either by obtaining empirical data or by
use of atmospheric dispersion models, in order to be able to judge whether or
not the resulting ambient odor concentration is acceptable to the community.
"On the other hand, if odor annoyance threshold data are available, an
ambient odor limit can be related to a particular zoned area and specified to
avoid an odor annoyance being experienced by the population that lives or works
in a particular zoned area. Further, it should be recognized that odors do not
discharge only from stacks or well-defined enclosures but could originate from
fugitive type emissions (i.e. anaerobic lagoons). As a result, it may be
necessary in certain areas to have a combination of stack emission and
ambient odor regulations available to control all significant sources of odor."
* For three of the pollutants covered by national ambient air quality
standards (HC, CO, and NO ), the vehicle emissions standards established
under Section 202 must correspond to reductions specified in the Clean Air
Act. However, this does not apply to odorous substances as such.
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4.4 Local Programs Studied
Two local and eight State odor control programs were selected for careful
analysis based upon 1978 regulatory programs:
1. The Bay Area Air Quality Management District in California
2. The Wayne County Health Department in Michigan
3. Connecticut
4. Iowa
5. Kentucky
6. Minnesota
7. North Dakota
8. Oregon
9. Pennsylvania
10. Rhode Island
All of these jurisdictions have odor control programs containing elements
similar to those which could be promulgated by EPA. Each has also had
relatively extensive experience in dealing with odor problems.
Conceptually, the regulations of these 10 jurisdictions can be divided
into five categories: two "ambient" approaches, and, three "emission based"
approaches. Table 2 presents this categorization scheme.
4.5 Criteria for Determining Regulatory Effectiveness
Although it is difficult to judge the overall effectiveness of any
environmental regulation since many social, economic and administrative
factors are involved, several criteria of an "effective odor regulation"
can be given:
1. It offers an effective mechanism for resolving community odor
nuisances in a timely fashion.
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22
2. It resolves problems in an equitable manner.
3. It requires only a reasonable commitment of private and public
financial and manpower resources in light of the nature and
magnitude of the problem.
4. It.is responsive to community attitudes and sensibilities.*
5. It is enforceable.
Unfortunately, the effectiveness of odor regulations have not been
empirically analyzed. Much insight can be gained, however, from reviewing
available literature and through conversations with knowledgeable individuals
in the governmental, industrial and academic sectors. The following
sections apply the above-mentioned effectiveness criteria to the regulatory
strategies employed by the agencies surveyed. Many of these agencies
employ a combination of approaches, and when this is the case, those agencies'
regulations will be analyzed in more than one section of the report. For
purposes of analysis, the following categorization will be followed:
Ambient Approaches
1. Objectionability at property line
2. Scentometer
3. Odorant-Specific Ambient Standards
Emission-based Approaches
1. Odor level standards
2. Incineration or equivalent standards
3. Odorant-specific performance standards
*This is a more relevant consideration for odor regulation than for
other environmental controls because of the subjective nature of the problem.
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TABLE 2. -STATE ODOR CONTROL STRATEGIES
AMENABLE TO THE CLEAN AIR ACT
Aabient
(Non-odorant
specific)
Jurisdiction
Bay Area
Regulation
Operative Regulatory
515105
No person shall cause, let, permit, suffer, or allow the emission of any
odorous substances which causes the ambient air at or beyond said person's
property line to be odorous and to remain odorous subsequent to its dilu-
tion with 4 parts of odor-free air. (Dynamic olfactometer/triggered by
specified frequency of complaints.)
Connecticut
§19-508-Z3(a)(l) Objectionability to staff Investigator, considering nature, concentration,
duration and location (beyond property line).
Iowa
§400-4.5 (455B)
Violation occurs 1f odor is of such frequency, duration, quality and
intensity as to harm public health or welfare or cause a nuisance.
Kentucky
401 KPR 3:020
S4(10)
Ambient standard not to exceed 7 dilutions (scentometer)
Minnesota
APC 95{c)(4)
(4) No odor source shall emit air contaminants into the ambient air which
cause odor outside the alleged polluter's property line in excess of the
following limitations:
(aa) One odor unit in areas zoned residential, recreational,
Institutional, retail sales, hotel or educational.
bb) Two odor units in areas zoned light industrial.
cc) Four odor units in areas zoned other than in subsections (aa) and
bb) above.
North Dakota
§33-15-16-02
Limit of two odor concentration units outside property line (scentometer
of ASTM).
Rhode Island
Regulation No. 17
Objectionability to staff investigator, considering nature, concentration,
location, duration, and source (beyond property line).
Ambient
(Odorant-speciflc)
Connecticut
§19-503-23(a)(3)
Ambient threshold values established for 53 odorants.
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TABU 2 (Cent.)
APPROACH
JURISDICTION
REGULATION
OPERATIVE REGULATORY LANGUAGE
Emission-based
(Non-odorant
specific)
Wayne County, Mich.
Informal Agency
Guidelines
(Judicially
upheld)
150 odor units/cubic foot - specified syringe dilution technique
Connecticut
!l9-508-23(a)(2)
120 odor units/cubic foot - Mills ASTH adaption
Minnesota
APC
(c) Odor Emission Limits. Violation of APC 9 shall be any discharge
of air contaminants in excess of the following odor emission limits:
(1) Odor sources emitting from well-defined stacks 50 feet or more
above grad elevation and with adequate dispersion characteristics
as determined by the Agency shall not emit odors in greater than
150 odor concentration units.
(2) Odor sources of less than 50 feet elevation above grade or other-
wise failing to create good dispersion conditions as determined
by the Agency shall not emit more than 2b odor concentration units.
(3) No odor source shall have an odor emission rate in excess of
1,tWO,000 odor concentration units per minute.
Bay Area
Pennsylvania
Bay Area
S15103
Variable dilution rate depending upon elevation of emission point
(triggered by specified frequency of complaints).
Emission-based
(Performance
standards)
Iowa
Oregon
S20.3(l)(4)
5525-055, 25-150
and 25-350
Standards for anerobic lagoons.
Standards for reduction of animal matter, kraft pulp mills
pulp mills.
and sulfate
5123.31(a)
Incineration or equivalent standard for 15 listed source categories
(and all sources of H^S or mercaptans).
515106
TRS emissions from kraft pulp mills.
Emission-based
(Odorant-speclflc)
Bay Area (Calif.)
115104
Specific emission limitations established for dimethylsulfide, ammonia,
mercaptans, phenolic compounds and trimethylamine. Varies with charac-
teristics of emission source and excludes kraft pulp mills.
Pennsylvania
§123.31(a)
Incineration or equivalent standard for all emitters of H2S or mercaptans.
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Combination Approaches
1. Minnesota
2. Bay Area
4.6 Ambient Approaches
Modern ambient odor regulations are typically phrased either in terms of
the objectionability or detectability of odors at the plant boundary. Many
agencies use ambient approaches in tandem with emission limitations, nuisance
laws, or both in order to maximize enforcement flexibility.
4.6.1 The Objectionability Approach
In Connecticut,5 Iowa11 and Rhode Island, an agency inspector checks,
without instrumentation, such factors as the nature, concentration, duration and
location of the alleged emission, relying only on his own perception of the
alleged objectionable emissions. In almost all cases, inspectors in these
states respond only on the basis of odor compliants directed at a particular
source. The agency does not. seek out odor violations since community odor
complaints are believed to be the best measure of whether or not a problem
exists.
An obvious advantage of this approach is that it is generally easy and in-
expensive to administer, especially where a single source is clearly responsible
for the problem. In addition, it is responsive to community sensibilities in
that it is triggered by complaints. In the three states surveyed, it was
indicated that this method is a reasonably effective one for solving community
odor problems. Furthermore, the objectionability approach avoids many of the
technical impediments inherent in more sophisticated methodologies. The sub-
jective response of the inspector determines whether or not there is a viola-
tion irrespective of what a quantitative chemical or sensory analysis might
show.
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25
The disadvantages of the objectionability approach flow directly from those
features that make it desirable. The high degree of subjectivity in the
enforcement process makes possible problems of inequitable application of the
law and an inability of source owners to effectively plan for compliance. In
many ways, the objectionability approach is no different from the traditional
public nuisance approach in that violations are established primarily on the
basis of testimony from affected residents and from the agency inspector as
to the objectionable nature of the source's emissions. While this approach
enables official investigation and public prosecution of cases that would
otherwise be left to the law of private nuisance, it does little more than
codify traditional nuisance standards.
The State of Connecticut has had significant experience with the
objectionability regulatory approach. Officials within the Connecticut
Department of Environmental Protection (DEP) believe that the approach has
worked reasonably well for controlling industrial odor problems although
industry representatives are justifiably dissatisfied with the Inherent
subjectivity it requires. Difficulties arise, however, where odor complaints
are raised in connection with existing or proposed non-industrial sources
such as neighborhood restaurants or automotive repair shops. In these
situations, poor local zoning laws are frequently the true basis of the
problem. State air pollution control agencies are justifiably loath to
become involved in minor local land use disputes.
Despite this limitation, the DEP's use of the objectionability approach
is significant in that it has the legal authority to impose both ambient
and emission-based odor standards. Connecticut's odor regulation prohibits
the discharge of "objectionable" odors beyond the source property line.
An odor is deemed "objectionable" when:
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26
1. A staff member of the Department of Environmental Protection
determines, following personal observation, that the odor is
objectionable, taking into account its nature, concentration,
location, and duration; or,
2. Samples from the source are taken and found to rate over 120
odor units per cubic foot as determined by Mills' adaptation of
ASTM D-1391-57;15 or,
3. If the odor is caused in whole or in part by a listed substance
and when the specified concentration is exceeded for any period
of time as demonstrated by analysis made in accordance with methods
approved by qualified professional chemists.*
Connecticut DEP has found the modified ASTM and the odorantTspecific
ambient standard technique to be less effective than the objectionable-odor
approach. The agency has been able to resolve most of its odor complaints
without resorting to the use of odor panels or chemical analyses of property
line odorant concentrations. One of the principal reasons for the agency's
reliance on the subjective objectionability approach is that it provides
a more reliable (albeit subjective) indicator of a true community odor
nuisance. As noted earlier, the modified ASTM and other detectability-based
regulatory standards may or may not protect against community annoyance.
4.6.2 Ambient Sensory Regulations
Several State and local agencies specify the use of a Scentometer as
the recon..nended method for determining the allowable ambient level of odor
pollution. Of the States surveyed, the approach is used in two: Kentucky15
and North Dakota.
Connecticut's listed threshold values have proved to be essentially
unworkable and unrealistic. Adequate measurement techniques have not been
developed and there is no data that sufficiently confirms the reasonable-
ness of the levels in terms of odor response.
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27
The Scentometer consists of a small rectangular chamber that contains
two sniffing tubes on top for insertion into the nostrils. Normal breathing
draws the odorous air from the surrounding environment through the bottom
panel and also through the two side panels, which contain activated carbon to
provide odor-free air for dilution. The bottom panel is provided with several
calibrated holes of varying diameter to vary the dilution ratio. These holes,
which correspond to specific ratios of dilution to threshold (D/T), are
designated in some odor regulations as a Scentometer reading number having
a specific numerical odor strength. The device is limited to diluting the
odor stimulus only to specified levels (e.g., 2, 7, 15, 31, 127 and 249 dilutions),
with no adequate provision for achieving a graduated degree of dilution in
between. The States of Kentucky and North Dakota specify allowable Scentometer
readings of 7 and 2, respectively. ,
Although the Scentometer represents an inexpensive and administratively
simple odor regulatory approach, it has certain basic disadvantages, which
affect its trustworthiness as an enforcement tool. First, it normally is
used by only one individual. Odor sensory responses by different people are
highly subjective and can vary widely. (Odor sensory evaluation conducted with
nine-member panels at I IT Research Institute and at TRC (The Research Corpora-
tion of New England) indicated that a tenfold variation in sensitivity
normally exists among panel members. Occasionally, the difference was as high
as a hundredfold). In addition, an individual's response to odor may vary
from day to day. The Scentometer method does not provide for the selection
of an odor sensory panel to average out high and low individual responses.
These factors cause courts and administrative officials grave concerns about
the ability to sustain enforcement actions where millions of dollars in
control costs may be at stake.
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Second, the construction of the instrument does not provide a reliable
means for an individual to isolate his or her nose from the odorous environ-
ment being monitored. Depending upon the individual's pattern of breathing
and ability to seal off the nasal passages with two sniffing ports, it
seems reasonable to expect that any odor in the ambient air could bypass
the instrument and be sensed directly by the nose, thus resulting in a false
positive response. Since the individual is surrounded by an odorous en-
vironment, it may not be possible to isolate the contribution of of the
suspected sources.
Third, as mentioned before, certain agencies have specified dilution-
to-threshold levels in their regulations that were intermediate between 2
and 7 D/T or between 7 and 31 D/T. On the basis of various discussions with
State and local agencies, the range of 2 to 7 D/T is particularly critical,
and an odor sensory method is needed that accurately determines the odor
dilution ratio within this range.2 The Scentometer cannot fill this need.
Finally, the Scentometer is not necessarily related to community
annoyance. While investigators have attempted to correlate Scentometer readings
to community odor nuisance, the fact remains that the Scentometer measures
odor detection, not odor annoyance. This basic dilemma, in concert with the
above-mentioned limitations, led the APCA Odor Committee to conclude that the
Scentometer is not a satisfactory instrument for measuring ambient odors
for regulatory purposes.2 This conclusion is shared by agency officials
in both Kentucky and North Dakota.
4.6.3 Odorant-Specific Ambient Standards
With the exception of ambient H2S standards, few state or major local
agencies use odorant-specific ambient standards to regulate odor pollution.
Ideally, an odor regulation would be odorant-specific rather than depend
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29
on a general detectable odor standard. Unfortunately, not enough is
known about the olfactory parameters of specific chemical substances.
Although detection thresholds have been established for most of the more
ubiquitous odorants such as FLS and mercaptans, the reliability of these
threshold values are a subject of controversy. Furthermore, generally
accepted annoyance threshold values simply do not exist.
One agency which has made a significant effort to specify and
regulate the ambient concentration of designated odorants is Connecticut.
Although Connecticut has identified ambient odor threshold limits for 58
chemical substances, it does not rely on these threshold values in the
enforcement of its odor regulation since the agency has little confidence
in the correlation of these concentrations to community annoyance or
nuisance conditions.* In short, the response of the human nose to chemical
stimuli is simply not subject to precise quantification, especially in
real-world ambient settings.
These Connecticut standards are based on a study by Arthur D. Little Inc.,
18
which determined odor threshold values for 53 commercial chemicals. These odor
threshold concentrations were determined with a panel of four trained professional
people. The odor test room was designed to provide a minimum of background odors.
It is significant that the Arthur D. Little report on this specific
work states that "the recognition odor thresholds reported in this study, determined
as they were by trained panelists under ideal conditions, are not presented as
indicative of concentration levels at which these compounds might constitute an
odor problem in the ambient malodorous atmosphere. No attempt has been made to
assess the degree of objectionability of the odorant chemicals, and the determina-
*Development of reliable sample collection procedures also presents a
problem
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30
tion of "odoriferous" concentrations in ambient air, for any given chemical
18
and background odor moiety, would require field testing."
4.7 Emission-based Approaches
Odor control strategies that focus on emissions avoid many of the
problems inherent in ambient approaches. Most importantly, emission oriented
controls eliminate the problem of having to quantify the precise ambient impact
of the emitting source. Although the emission limits should be related to
ambient impact in a general way*, compliance is determined on the basis of a
quantitative analysis of the stack gas, not the ambient air into which the
gaseous odorants diffuse.
This is not to say, however, that emission based controls are problem-
free, since emission controls suffer from many of the same difficulties as
ambient techniques. The most common emission based approach is the establish-
ment of source and odorant-specific incineration or performance standards.
For example, TRS standards-for kraft pulp.mills and incineration requirements
for rendering plants have been promulgated by several air pollution control
agencies. While these regulations are reasonably objective and specific, they
only address a limited part of the total odor problem and do not necessarily
insure the avoidance or resolution of community odor problems.
Another emission based alternative is the specification of the maximum
odor dilution ratio of the stack emission. Under this approach, a source
*In setting odor emissions limits, anticipated ambient impacts associated
with selected emission levels should be a central consideration. As noted
earlier, however, the data on which to base such determinations is quite
sparse.
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31
may emit only a specified number of "odor units" per cubic, foot of total
emissions. An "odor unit" is defined as the number of cubic feet of
odor-free air needed to dilute one cubic foot of the odorous emission to the
point where the diluted sample cannot be detected by a specified percentage
(typically 50 percent) of .an odor sensory test panel. Connecticut specifies
an odor emission limit of 120 odor units per cubic foot based upon the ASTM
method as modified by Mills. Minnesota uses a similar approach employing
20
a different modification of the ASTM method but makes a distinction re-
garding stack height in specifying source emission odor limits.
4.7.1 The Odor Level Standards Approach
Several agencies, including Wayne County, Michigan; Connecticut; and,
Minnesota specify a modified ASTM syringe dilution technique for assessing
odorous stack emissions.
The basic method consists of taking a sample of the exhaust gas in
a 100 cc. cylinder or 250 cc. glass tube. The gas sample is then evaluated
under controlled conditions by a panel of trained individuals in an essentially
odor-free environment. An odor panel of six to eight persons is normally
selected by a prescribed odor sensory test to ensure the selection of people
having average olfactory perception.
Individual odor panelists receive a series of pre-determined odor
dilutions in 100 cc. syringes. Each panel member must smell momentarily a
rapidly expelled pulse of odorous air from the 100 cc. syringe whose tip
is directed toward the nostrils. The panelist indicates either a negative or
positive response to the odor being detected and the panel's responses are
correlated with the various odor dilution levels. The median odor threshold
level is defined as that dilution level where 50 percent of the panel does not
detect the diluted odor stimulus.
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The advantages and disadvantages of the ASTM approach have been widely
discussed in the literature. William H. Prokop of the National Renderer's
Association summarizes the issues and makes specific recommendations in a paper
21
entitled Status of Regulations for Source Emission and Ambient Odors:
"Although Friedrich and Benforado reported reliable results with
the ASTM syringe method, it was emphasized that training of the .
odor sensory panel is important and following consistent procedures
is necessary. The basic method lacks a defined procedure for odor
stimulus presentation since the various odor dilutions are to be
randomly presented to the panel by mixing the order of strong and
weak odor stimuli. Sometimes, a blank or odor-free sample is sub-
stituted to check the panel's reaction. This has tended to produce
confusing results and as a consequence, no satisfactory provision
is available to check the reliability of positive-negative responses
of the panel.
"These basic shortcomings of the ASTM method were recognized by
industry and an ASTM Task Group was organized to review the method.
A position paper dated March 12, 1973 was prepared by this committee
that critically evaluated the syringe dilution technique. The Committee
basically concluded that an ascending order of odor concentration should
be used in the presentation of odor stimuli to the panel and that at
each level two syringes be submitted to the panelist. One syringe
contains the odor stimulus and the other is a blank containing odor-
free air. A forced choice answer is, required; odor in the first or
odor in the second.
"Dynamic sensory'methods are considered to be more reliable than
static methods and have been developed by a number of investigators.
Static odor sensory methods do not have any satisfactory provision
to check the reliability of positive-negative responses of the panel.
An approach is, therefore, desired where the diluted odor sample is
presented to the panel for discrimination from samples of non-odorous
air and results can be related to statistically significant confidence
levels."
At the present time, only the Bay Area Air Quality Management District
Q
uses the dynamic approach. It is suggested that this approach is superior
to current static techniques thereby enhancing the effectiveness and
enforceability of the regulation.
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33
Agency experience with the static ASTM approach (and its modifications)
has been mixed. As indicated earlier, Connecticut has decided to ignore
its static ASTM provision, relying instead on the more subjective "objection-
ability" criteria. Air pollution officials in Wayne County, Michigan, on the
other hand, believe that they have had good success in the application of the
static modified ASTM approach. The validity of the method has been supported
22
by a legal decision of the Michigan Court of Appeals. The agency attri-
butes its success to the significant experience it has had with this method.
This experience has allowed the agency to develop some useful variations of
the ASTM approach, which enhance its reliability. The agency believes that its
across-the-board odor concentration unit approach has excellent general
applicability for urban odor sources.
4.7.2 Incineration Standards
Numerous State and local regulatory authorities, including the Common-
wealth of Pennsylvania, use an incineration or equivalent standard for regu-
lating odorous emissions from designated source categories. Pennsylvania's
23
standard is not atypical, and reads as follows:
"(a) (1) No person shall cause, suffer or permit, at any
time, any emissions from the following processes unless the
emissions have been incinerated at a minimum of 1200 degrees F.
for at least 0.3 seconds prior to their emission into the outdoor
atmosphere: chip dryers, animal blood dryers, asphalt oxidation,
asphalt roofing manufacture, brake shoe debonding operations, core
ovens, rendering cookers, varnish cookers, paint-baking ovens, meat
smokehouses other than those in single family farms, plastic curing
ovens, fabric-backing and fabric-coating baking ovens, ovens for
curing of binders in mineral wood production, meat processing other
than in single family farms, tear gas manufacture and sources of
hydrogen sulfide or mercaptans. (2) Techniques other than incinera-
tion may be used to comply with the provisions of clause (1) of this sub-
section if it is shown to the satisfaction of the Department that such
techniques are equivalent to or exceed the required incineration in
terms of control of the odor emissions.
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"(b) No person shall cause, suffer, or permit the emission
into the outdoor atmosphere of any malodorous air contaminants
from any source whatsoever, including those in compliance with
the provisions of subsection (a) of this section, in such a
manner that the malodors are detectable beyond the property of
the person.
"(c) The prohibition in subsection (b) of this section shall
not apply to odor emission arising from the production of agri-
cultural commodities in their unmanufactured state on the premises
of the-farm operation." (Emphasis added).
The most important objection to the incineration standard approach
is that it requires control regardless of the fact that a community
odor problem may not be caused or threatened by the source. Critics point
out that it is wasteful to impose substantial hardware, maintenance and
energy costs on odor sources unless necessary to prevent an odor nuisance.
Such an approach is contrary to the recommendation of the APCA
Odor Committee that an existing or potential odor nuisance should be
2
established before controls are required.
The Commonwealth of Pennsylvania has recognized this flaw in the regu-
lation and has corrected it administratively by requiring the establishment
of a community odor problem before incineration will be required . With this
administrative adaptation, the Pennsylvania regulation has worked quite well
according to agency officials. By reserving sanctions for sources truly
causing community nuisances, the regulation can be narrowly focused.
Another advantage of the Pennsylvania approach is that it combines
odorant and source-specificity by enumerating 15 source categories as well
as all sources of hydrogen sulfide and mercaptans-two of the most wide-
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35
spread odorants in Pennsylvania. This feature allows industry to be put on
notice that they may be subject to controls unless they prevent an odor
nuisance from arising. At the same time, however, by prohibiting the
discharge of any malodors beyond the source property line, the regulation
prevents its own specificity from creating regulatory gaps regardless
of compliance with the source and odorant-specific incineration standard
of the regulation.
An additional advantage of the Pennsylvania approach is that it allows
alternatives to incineration, which are equally effective. While incin-
eration is the best-developed odor control for many sources, it is poor
policy to preclude new or innovative technological approaches. This flex-
ibility of allowing source owners ,to propose less costly means of equivalent
odor control fosters technological development and should be incorporated into
all incineration standards.
Finally, the incineration approach avoids the complex subjective uncer-
tainties inherent in the ASTM and Scentometer approaches, although determin-
ing whether another control method is equivalent to incineration may
introduce problems of subjectivity. Compliance assessment is relatively
routine, thereby eliminating the enforcement problems that plague the
subjective regulatory strategies.
*This is a case-by-case determination based upon the nature of the
problem and the number of valid citizen complaints.
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36
4.7.3 Source-specific Performance Standards
For many years, performance standards for specific odorants from
designated source categories have been used to control odorous emissions.
Indeed, EPA has promulgated a federal New Source Performance Standard for
pulp mill JRS emissions.23 States are, therefore, obligated under Section
lll(d) of the Clean Air Act to regulate TRS emissions from existing mills.
The greatest advantage of the performance standard approach is that it
allows the agency to focus its resources on problem sources without
getting bogged down in efforts to quantify stack or ambient "odors" through
subjective sensory techniques. In areas where a few well-defined sources are
responsible for the bulk of the odor complaints, this approach may well be
the best one from both an economic and an administrative standpoint.
In Iowa, for example, anaerobic lagoons were perceived as one of the
State's most serious odor problems. In response to increasing numbers of public
13
complaints, Iowa enacted its first odor control rules in May 1977. The
rules established a construction permit program for new anaerobic lagoons and a
nuisance-type odor standard for other odor sources. The construction permit
provisions require that new anaerobic lagoons submit to a preconstruction
review by the Iowa Dept. of Environmental Quality (DEQ). The review will
assess the lagoon's odor production potential and water pollution potential.
Implementation of the new rules is still under consideration, pending the
outcome if public hearings designed to resolve differences between the rules
developed by the DEQ and a new statute passed by the Iowa General Assembly.
While the performance standard approach works well in areas with
relatively few odor sources, sole reliance on source-specific performance
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37
standards in heavily urbanized or industrialized areas is not practicable-.
The variety of odor sources and odor complaints prevents the agency from
establishing source performance standards for all potential sources.
In summary, source performance standards for specific odor sources
can be a very effective odor-control technique where only a few sources
or sources categories are responsible for most of the odor problem. Where
this is not the case, as in much of the urbanized Eastern United States,
performance standards for major odor sources must be supplemented with more
general and more flexible alternatives.
4.8 Combined Ambient-Stack Approaches
i
Whether an emission or ambient approach is more effective frequently
depends upon the nature of the odorant and the characteristics of the
source. In the case of well-defined sources of odorants for which annoy-
ance threshold data are available, ambient standards may be appropriate.* In
other cases, ambient standards are impractical to administer, and emission
standards must be employed.
4.8.1 Minnesota
The State of Minnesota has an odor regulation employing a combination
of odor emission limitation and ambient standards.10 With respect to odor
emission limitations, a three-pronged approach is used. Under Minnesota
regulation APC 9, the following limitations apply:
Odor Emission Limits* Violation of APC 9 shall be any discharge
of air contaminants in excess of the following odor emission limits:
At present, adequate annoyance threshold data do not exist for any
major odorant.
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(1) Odor sources emitting from well-defined stacks 50 feet
or more above grade elevation and with adequate dispersion charac-
teristics as determined by the Agency shall not emit odors in
greater than 150 odor concentration units.
(2) Odor sources of less than 50 feet elevation above grade
or otherwise failing to create good dispersion conditions as deter-
mined by the Agency shall not emit more than 25 odor concentration
units.
(3) No odor source shall have an odor emission rate in excess
of 1,000,000 odor concentration units (O.C.U.) per minute.
Although the odor emission limitations in ARC 9 may be restrictive,
the effectiveness of this three-pronged approach lies in its recognition
of the significance of odor dispersion and total mass loading.
The effectiveness of the one million O.C.U./minute standard is more
controversial. This limit is obtained by multiplying the volumetric emission
rate in cubic feet per minute by the odor dilution ratio measured at the
t.
2
24
emission source and expressed in odor units per cubic foot. The APCA TT4
Odor Committee made the following comments on this approach:
The Committee was equally divided regarding their approval of or
opposition to a total odor emission rate being applied for regulatory
purposes. Those in favor considered this concept to be useful since
another dimension other than odor concentration is available for eval-
uating an odor nuisance. In particular, it provides the means for to-
talizing a multiple number of odor emissions from a single source.
Those opposed to this concept recognize it has a certain validity
when applied to small volume emissions. However, they question this
concept when applied to large volume emission, for example, from plant
ventilating air scrubbers. Based on the previously cited total odor
emission limit of one million odor units per minute, a 100,000 cfm
scrubber would be allowed a stack emission odor concentration of only
*Minnesota which utilizes a modified ASTM method for determining compliance
with its odor emission limitations, also has an incineration standard for
animal matter processing facilities (ARC 10).
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39
10 odor units. This clearly is unrealistic and it is doubtful whether
the specified syringe dilution technique is sufficiently sensitive at
this low odor level to establish compliance reliably. The basic
objective for an odor regulation should be to limit the ambient odor
concentration at ground level, C rather than the total odor emission
rate, Q. where both terms relate to'atmospheric dispersion models.
It appears that the concept of total odor emission rate could be
useful as a guideline for evaluating an odor nuisance but it should
be applied judiciously for regulatory purposes*.
Minnesota's ambient regulatory approach for odors is somewhat novel
but it results in problems of enforcement. It provides:
(4) No odor source shall emit air contaminants into the ambient
air which cause odor outside the alleged polluter's property line in
excess of the following limitations:
(aa) One odor unit in areas zoned residential, recreational,
institutional, retail sales, hotel or educational.
(bb) Two odor units in areas zoned light industrial.
(cc) Four odor units in areas zoned other than in subsections (aa)
and (bb).
The effort to distinguish between area types is sound policy in the ab-
stract. However, this approach results in some very difficult technical and
administrative problems in enforcement. Attempts to estimate the ambient
odor impact of a source on "zoned" areas proved to be unworkable and is
no longer being enforced in Minnesota. Techniques for estimating the
impact of individual sources on ambient odor levels may become essential
if odors were ever to be regulated as a criteria pollutant under the Clean
Air Act. In particular, it would be important to be able to estimate
The Committee noted with interest that Minnesota relies basically
upon its stack emission limits, expressed in odor units per cubic foot,
for enforcement of its odor regulations.
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40
ambient odor impacts to determine compliance with the prevention of significant
deterioration of "clean" areas.
4-8.2 The Bay Area Air Quality Management District
Probably, the most clearly drafted and well conceived odor regulation
in effect today is that of the Bay Area Air Quality Management District
serving the San Francisco - Oakland metropolitan area. Division 15 of the
Bay Area regulations establishes a comprehensive scheme for regulating
ambient and stack odors. The regulation blends specificity of scope and
broad general standards in a way that maximizes its effectiveness.
The regulation begins by defining its scope. Specifically, occupational
odors, as governed by the California Department of Industrial Relations, are
not subject to Division 15. The regulation also provides express exemptions
for the following sources and operations:
(a) Single family dwellings
(b) Restaurants and other establishments for the purpose of pre-
paring food for human consumption, which employ less than 5 persons
(c) Materials odorized for safety purposes
(d) Materials possessing strong odors whose use is necessitated
for reasons of public health and welfare and where no suitable substi-
tute is available and where best modern practices are employed.
(e) Agricultural operations as described in the California Health
and Safety Code, Section 41705.
The regulation also specifies that compliance does not exempt anyone
from compliance with the State's nuisance law. That regulation is triggered
upon the receipt of five citizen complaints and provides an effective
tool for resolving minor odor problems on an informal basis.26
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The emission limitations of Division 15 are not applied in the
absence of evidence indicating that a potential odor nuisance exists.
Specifically, § 15100 provides:
"The limitations prescribed in § 15103, § 15104, § 15105 and in
§ 15106.1 through 15106.6%shall be, and shall remain, applicable to
a person responsible for an emission regulated by any of thei. ^ sections
after the Air Pollution Control Officer has recieved odor complaints
from ten or more complainants, within a 90-day period, alleging that
said person is responsible for odors perceived by the complainants at
or beyond the property line of said person, and deemed to be objectionable
by them in the normal course of their work, travel, or residence."
Once triggered by the required number of complaints, Division 15 imposes
four substantive requirements:
1. § 15103 - A general odor emission limitation based on the dilution
ratio concept and applicable to all odorous substances emitted by any
*
source . Specific recognition of diffusion characteristics is provided
by allowing odor intensity to increase in direct proportion to stack
discharge height as set forth on the following page:
2. § 15106 - Limitations for TotO Reduced Sulfur at Kraft Pulp Mills.
(Also, Division 17 of the Bay Area regulations establishes an incineration
standard for rendering plants.)
3. § 15105 - An off-property ambient limitation of four dilutions to
threshold for all odorant substances. Compliance is also determined through
the dynamic olfactory method.
*
Compliance is determined through a dynamic olfactory approach.
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42
Elevation of
emission point above grade
(feet)
Dilution rate
(volumes of odor-free air
per volume of source sample)
Less than 30
30 to 60
60 to 100
100 to 180
Greater than 180
1,000
3,000
9,000
30,000
50,000
2. §15104 Emission limitations for five particularly troublesome
odorants. Again, source emission characteristics are factored into
the standards as shown below:*
MAXIMUM ALLOWABLE EMISSION CONCENTRATION IN PPM
Compound or
family of compounds
Dimethyl sul fide (CH3)2S
Ammonia NH,
0
Mercaptans calculated as methylmer-
captan CH-jSH
Phenolic compounds calculated as
phenol CgHgOH
Trimethylamine (CH3)3N
Type A
emission point
0.1
5000
0.2
5.0
0.02
Type B
emission point
0.05
2500
0.1
2.5
0.01
Specific analysis procedures are established for each odorant.
*Type A emission points have better dispersion characteristics than do
Type B emission points. (See Sections 2036-2038-Regulation 2.)
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The comprehensiveness and flexibility of the Bay Area approach enhances
its effectiveness in resolving odor problems. Its most desireable features
include:
- Specificity - The major odorous emissions are specificall ' governed
by emission limitations. Further, Kraft pulp mills and rendering
plants are subject to individual performance standards. This specific-
ity adds certainty and predictability to the regulation and allows the
agency to focus its resources where they can be most cost-effective.
Exemptions are clearly established.
- Flexibility - The regulation preserves nuisance law and provides for
general ambient and emission odor standards. These general standards
allow the agency to deal with odor problems Involving odorants other
than the five covered by § 15105 or sources other than Kraft pulp mills
or rendering plants.
- Responsive to Community Sensibilities - The complaint-triggering
feature of the regulation avoids the dilemma of imposing expensive
controls in the absence of a demonstrated community odor nuisance.
This should be an important aspect of any odor control program.
- Clearly Written - The Bay Area odor regulation is very well drafted.
The provisions are written in a way that can be understood by lay
people without loosing technical accuracy. Testing and analy-
sis procedures are clearly spelled out.
- State of the Art Measurement Approach - The Bay Area i s one of few
major air pollution agencies using the dynamic olfactory method for
compliance testing. This approach avoids many of the problems inherent
in the use of the Scentometer or the static ASTM approach.
- Enforceability - Agency officials indicate that the regulation has been
very effective in resolving odor problems and obtaining compliance.
Many sources have been brought into compliance with Division 15 through
both formal and informal procedures.
4.9 Summary and Conclusions
Any analysis of alternative federal odor control strategies should begin
with a review of State and local experience in the field. The general conclu-
sion that can be drawn is that most agencies, while dissatisfied with exist-
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44
ing regulatory approaches, recognize that technical limitations stand in the
way of simple solutions or more effective alternatives. As noted by the
2
APCA TT4 Odor Committee:
"There has been a definite reluctance expressed by some state
and local agencies considering new regulations to incorporate
the use of the ASTM syringe method or Scentometer. Instead,
they prefer to retain the nuisance concept to regulate odors.
Further, those agencies which do specify either of these twc
odor measurement methods still have an odor nuisance regulation
or various criteria for determining an odor to be objectionable.
However, the agencies recognize the limitations of the odor nui-
sance concept.
"It must be concluded that present odor regulatory approaches
are generally unsatisfactory. There are two basic needs: (1)
develop sound administrative procedures for confirming the
existence of a community odor nuisance, and (2) obtain reliable
odor sensory data that can be related to community acceptance
or annoyance of a particular odor."
The Committee then goes on to make several specific recommendations for
improving the effectiveness of current odor-control regulations. These recom-
mendations are in basic harmony with the expressed thoughts of those agency
officials with whom discussions were held during this study and are pertinent
to the analysis of future federal involvement in odor pollution control.
From the standpoint of this report, the most significant conclusions of
the APCA TT4 Committee are:
1. The Committee arrived at an essentially unanimous consensus
that the existence of a community odor nuisance should be estab-
lished before regulatory limits are applied to a specific odor
source to obtain compliance. The procedure for establishing a
community odor nuisance would require a specific number of valid
complaints being received from separate households during a fixed
time period. The Committee also concluded that there should be
specific procedures and guidelines provided to establish the
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45
existence of a community odor nuisance which take into account the
community's characteristics: population distribution, socioeconomic
activity, and land use zoning.
2. The Committee agreed that odor problems are basically related to
the local community and should be regulated by the appropriate
local agency.
3. Based on the technology currently available for measurement and
control, limiting the odor dilution ratio of the stack emission
is preferred as a method of correcting an odor problem. However,
applying rigid limits to stack emissions should be avoided.
Flexibility should be provided with some allowance being made
to take into account local conditions and type of zoning.
4. The relating of ambient odors to annoyance thresholds for different
communities or zoned areas is fundamental to establishing ambient
odor type standards. This could be accomplished by determining
dose-response relationships that equate annoyance with odor inten-
sity and the degree of unpleasant character of a particular odor.
This is a relatively complex approach to developing odor regulations.
However, there is a strong consensus of the Committee that it
could prove to be useful as a long-term approach. It would be
necessary for the funding of this program to be provided by the
Federal EPA as opposed to any state or local agency.
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46
5. It should be clear what specific types of odors and/or sources
are to be excluded from the regulations.
6. The Scentometer and ASTM syringe methods currently used by state
and local agencies are considered by the Committee to be inade-
quate for regulatory purposes. There is a basic need for odor
sensory methods which are capable of measuring odors objectively
and reliably.
There is a consensus of the Committee in favor of the dynamic
olfactometer approach and phasing out of the ASTM syringe method for
regulatory enforcement."
Given the basic structure of the Clean Air Act, it would be difficult,
if not impossible, for EPA to incorporate many of these recommendations into
a federal odor pollution control strategy. This statement is particularly
true with respect to the possible promulgation and implementation of national
ambient standards under Sections 108-110 of the Act. The next chapter
discusses these limitations and analyzes the advantages and disadvantages,
as well as the legal-administrative constraints, of the various alternatives
available for regulating odors under the Clean Air Act.
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5.0 ADVANTAGES AND DISADVANTAGES OF ALTERNATIVE ODOR CONTROL
STRATEGIES UNDER THE CLEAN AIR ACT
The ultimate objective of this report is to analyze the implications
and limitations of alternative odor control options under the Clean Air Act.
The Clean Air Act offers three basic alternatives for controlling non-
hazardous emissions: 1) The implementation of National Ambient Air Quality
Standards (NAAQS) through State Implementation Plans (SIP's), 2) The
promulgation of Federal New Source Performance Standards (NSPS) for
designated emissions from specified categories of stationary sources, or
3) The promulgation of Federal standards applicable to emissions from new motor
vehicles.
Establishment of NAAQS sets in motion a complex, time-consuming and
expensive legal process for implementing and maintaining the standards.
Thus, any decision to establish a new ambient standard for odor would be
made only after extensive research, analysis and public comment.
Although federal New Source Performance Standards generally have a far
smaller macroeconomic impact than NAAQS, they may have significant microeconomic
implications for the affected industries. As of July 1979, EPA had established
27
NSPS for 27 stationary source categories. To date, only one category,
kraft pulp mills, has been subjected to performance standards concerned pri-
marily with odor (i.e., total reduced sulfur)*. In promulgating this standard,
EPA did not attempt to use the subjective ASTM approach. Rather, objective
*The particulate/opacity standards for sewage treatment plants-and
petroleum refineries may have an indirect impact on odor emissions.
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48
technology-based numerical emission limitations of a readily measureable
material were established as is the mandated approach under Section 111 of
the Act.
The remaining sections of this report analyze the pros and cons of
regulating odors under the NAAQS and NSPS provisions of the Clean Air A-t.
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5.1 National Ambient Air Quality Standards
5.1.1 Statutory Overview
Under Sections 108-110 of the Clean Air Act, EPA is authorized to
establish national air quality standards for selected "criteria" pollutants.
Once the standards are established, the Act requires the states to prepare,
adopt and submit an implementation plan to EPA, which provides for the
attainment and maintenance of the national standards within the time frames
established by the Act. These state implementation plans (SIP's) must include
emission limitations, compliance schedules and such other measures as may be
necessary to ensure timely attainment and maintenance of the standards.
Areas failing to attain the standards by the deadline are subject to the
Act's new nonattainment provisions. Areas with air quality better than the
standards must prevent significant deterioration of existing clean air.
A decision to regulate a pollutant under Sections 108-110 has major
nationwide implications for government, industry and the public. The develop-
ment of NAAQS implementation strategies is an expensive and lengthy process.
In the 9 years since passage of the 1970 Clean Air Act Amendments, seven
criteria pollutants have been established. They include sulfur oxides,
particulate matter, nitrogen oxides, carbon monoxide, photochemical oxidants,
op
hydrocarbons* and most recently, lead.
The NAAQS-SIP process involves three basic steps. In analyzing whether
and how odor pollution should be regulated under this statutory scheme, each
* The hydrocarbon standard is used only as a guide in assessing
the adequacy of oxidant attainment strategies. Under existing
regulation it cannot, therefore, be used to control odors per se.
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step must be considered separately. The first step involves identification
and formal listing by EPA of the "air pollutant" for which ambient standards
are to be developed. Having listed the pollutant and published health/welfare
effects criteria and control techniques guidelines applicable to it, EPA's
next step is to establish primary and secondary national ambient air quality
standards. Primary standards represent those concentrations of the pollutant
that must be maintained to protect public health. Secondary standards address
public welfare.
The third step in the process is the most costly and time consuming:
implementation. The Act places primary implementation responsibility on
the States to develop and submit implementation plans. These plans must
29
comply with EPA's SIP Guidelines and the Act gives EPA authority to
promulgate its own SIP provisions for States submitting inadequate plans.
Regardless of who develops the plan however, it must be adequate to attain
and maintain the ambient standards, and to prevent significant air quality
deterioration in areas where those standards have been attained.
5.1.2 The Listing Process
Section 108 of the Act sets forth three conditions for listing
pollutants that will be made subject to ambient air quality standards.
The list includes each air pollutant*, emissions of which, in the EPA
Administrator's judgment:
* The Act defines the term "air pollutant" as any air pollution agent
or combination of such agents, including any physical, chemical,
biological, radioactive (including source material, special nuclear
material, and by-product material] substance or matter which is
emitted into or otherwise enters the ambient air. This term appears
to be broad enough to include "odors' generally or any specific odorant.
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1. cause or contribute to air pollution which may reasonably be
to endanger public health or welfare;
2. the presence of which 1n the ambient air results from numerous
or diverse mobile or stationary sources; and
3. for which air quality criteria had not been issued before the
date of enactment of the Clean Air Amendments of 1970, but for
which the Administrator plans to issue air quality criteria
under this section.
Within 12 months of including a pollutant on the list, EPA must issue
health and welfare effects criteria that accurately reflect the latest
scientific knowledge useful in indicating the kind and extent of all identifiable
effects on public health or welfare that may be expected from the presence
of such pollutants in the ambient air, in varying quantities.*
Clearly, the third condition is the critical determinant in the listing
process. No one could deny that odors can pose a threat to public welfare
or that they result from numerous and diverse mobile and stationary sources.
The decision to issue air quality criteria under Section 108, however, is
left to the EPA Administrator's discretion.**
* Although odor levels and specific health or welfare effects, have not
been precisely correlated, similar uncertainties exist for all the
existing criteria pollutants.
** Note, however, the courts have held that a § 108 listing is mandatory
where, as in the case of lead, EPA has formally found that the pollutant
meets conditions "1" and "2". Natural Resources Defense Council v.
Train. 411 F. Supp. 864 (S.D.N.Y. 1976), aff. 545 F.2d 320 (2nd Cir., 1976),
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52
Although odors were one of five pollutants originally identified in the
Senate's 1970 Clean Air Act deliberations as being of nationwide concern,*
EPA has indicated that it does not intend to list odor as a criteria pollutant
32
in the forseeable future.
Conceptually, there are only two ways of listing "odor" as a criteria
pollutant under Section 108. The first is simply to lump all odorous compounds
together and list "odor" as a criteria pollutant. The second is to identify
one or more specific odorous compounds or class of compounds. As will be
noted, both approaches would create difficult implementation and enforcement
problems.
The listing of "odor" as a criteria pollutant presumes that exposure to
any odor of a given intensity or for a specific duration causes adverse effects
on health or welfare. Even if one accepts the validity of this premise, cur-
rent understanding of odor effects does not allow any particular point on an
"odor" measurement scale to be correlated with identifiable effects on public
health or welfare. Odors vary widely in quality and acceptability at different
intensities, frequencies and durations. Human perceptions of odor vary widely
between individuals and even for the same individual, depending upon the con-
text and location of exposure. In short, a single standard for all "odors"
would create administrative chaos under the Clean Air Act. It would force
States to develop strategies for reducing all ambient odor levels, regardless
* At the time of the passage of the 1970 amendments, air quality criteria
already had been issued for five major pollutants (sulfur oxides,
particulates, carboii monoxide, hydrocarbons and photochemical oxidants).
Other pollutants of broad national impact identified by the Senate
Subcommittee on Air and Water Pollution in its report accompanying
the bill that ultimately became the 1970 amendments were fluorides,
-nitrogen oxides, polynuclear organic matter, lead and odors. Of these
five candidates, one (nitrogen oxides) since has been listed by the
Administrator on his own volition as a criteria pollutant, and one other
(lead) has been listed by compulsion as a result of a citizen suit.
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of their annoyance threshold, to an arbitrary intensity level. Such reduction
would be mandated regardless of whether those odors were annoying anyone.*
It follows that any attempt to list and establish national ambient
stanards for odor pollution must focus on specific odorants or classes of
odorants. While an identification of such compounds is obviously beyond the
scope of this report, existing state and local regulations afford a good
starting point for selecting such "criteria odorants." Mercaptans, phenolic
compounds, hydrogen sulfide, carbon disulfide, amines, ammonia, and selected
esters and fatty acids are the obvious candidates. If a realistic chemical
description could be developed for one or two of the most widespread odorant
combinations, it might be feasible to promulgate an appropriate ambient
standard. Ideally, such a standard would address those odorous compounds or
mixtures typically occurring together in the ambient air surrounding a
relatively few source categories. One useful approach might be to develop a
comprehensive chemical definition embracing the prime odorants attributable
to a few source categories which are common source of odor complaints, such
as:
1. Rendering, meat packing, slaughter houses.
2. Chemical plastic plants.
3. Sanitary land-fills.
4. Petroleum and natural gas refining and asphalt production.
5. Diesel exhausts.
If a reasonably specific chemical description could be developed, it
might then be possible to determine a realistic annoyance threshold value
for establishing ambient standards. In the absence of such a description,
* While a complaint- triggering mechanism is a feasible screening device
under state and local odor regulations, the Clean Air Act does not
appear to allow such flexibility. The air quality management f rame -
SnLnL=5? Ac£ em?lo^s standards fixed in terms of allowable
concentration levels such as ppm or ug/m3.
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54
the sheer number of different odorants, each with unique odor qualities,
would clearly preclude an odorant-specific approach to the problem.
5.1.3 Establishing Ambient Standards
Upon the issuance of effects criteria for a listed criteria pollutant,
EPA must propose and later promulgate national primary and secondary ambient
air quality standards. 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 (the) criteria and allowing an
adequate margin of safety are requisite to protect the public health."* It is
clear from the legislative history that the public whose health is to be pro-
tected includes "particularly sensitive citizens such as bronchial asthmatics
and emphysematics who in the normal course of daily activity are exposed to
33
the ambient environment."
The national secondary ambient air quality standards prescribed under
the Act "shall specify a level of air quality the attainment and maintenance of
which in the judgment of the Administrator, based on (the) criteria, is requisite
0-3
to protect the public welfare from any known or anticipated adverse effects.1
The public welfare that must be protected "includes, but is not limited to,
effects on soils, water, crops, vegetation, man-made materials, animals, wild-
life, weather, visibility, and climate, damage to and deterioration of property,
and hazards to transportation, as well as effects on economic values and on
* The "adequate margin of safety" referred to in the Act was included
to protect against potential health hazards not yet identified by research.
Presumably the language would justify a health-related standard based upon
ambiguous or incomplete data. The Clean Air Act allows the administrative
prohibition of certain activities without actual proof of health hazards to
an identifiable group, so long "as the prohibition can be defended as a scien-
tifically supportable margin of safety.
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personal comfort and wellbeing." The reference to "economic values" has
been discussed in the literature:
The reference to "economic values" should be read as authorizing protection
from effects of economic significance not otherwise mentioned (such as
offenses to aesthetic values) rather than indicating that economically
significant effects are the only ones that count. Protecting ^jblic
welfare from both "known or anticipated adverse effects" affords the
environment a margin of safety in the standards, albeit not one as
expansive as that extended the protection of public health. The primary
and secondary standards, together, are conceived as establishing a
minimally acceptable level of ambient air quality protecting man and
his environment from all known effects and-some that, although not
known, are legitimate subjects of concern.
With respect to odors, the reference to property deterioration and personal
comfort and wellbeing seems clearly broad enough to include odor pollution.
Conceptually, there are several ways of phrasing an ambient standard
for odor pollution. If a sensory approach is adopted, a standard could be
based on the following sensory measurement techniques:
1. Objectionability to a trained inspector.
2. A scentometer reading.
3. Other dilution to threshold measurement techniques.
The alternative, as discussed earlier, is to specify a maximum numerical
concentration for specified odorous compounds or mixtures.
The difficulties inherent in a sensorybased standard have been discussed
in the previous chapter. The wide variation in specific odorants and in
people's responses to them makes it impracticable to establish a single
standard for all offensive odors.
An Objectionability standard, for example, is, by definition, a purely sub-
jective approach. To phrase a national ambient standard in terms of its "Objec-
tionability" to a trained investigator is totally incompatible with air quality
management orientation of the Act. Concepts such as "attainment," nonattain-
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56
ment," "maintenance" and "prevention of significant deterioration" demand a
specific numerical standard by which to measure the success or failure of
implementation plans. No matter how many verbal parameters are established
to guide the inspector's subjective determinations, precise quantification of
ambient conditions is impossible with this approach.
Similarly, the Scentometer approach, through phrased in terms of a
quantifield level of odor intensity, is simply too unreliable. As discussed
earlier, the APCA TT4 Odor Committee has concluded that the Scentometer is an
inadequate tool for purposes of odor regulation. Furthermore, Scentometer
readings have no established direct relationship to odor nuisance or annoyance.
The odor sensory panel approach to ambient odor analysis is currently used
by the Bay Area Air Quality Management District. This approach involves the
collection of a sample of ambient air on or near the owner's property line.
This sample is then administered at specified dilutions to a pre-screened odor
panel. If over 50% of the panel detects odor in a sample of a specified dilution
(usually 4:1), a violation exists.
The odor panel approach, if properly administered, works well under
an administrative scheme that responds to odor complaints. It is through the
receipt of valid complaints that a potential odor problem 1s flagged. The feasi-
bility of this approach disappears, however, when one attempts to establish an
across-the-board ambient-odor standard regardless of the fact that individuals
are not annoyed by atmospheric concentrations that exceed the standard. Since
odor detection thresholds, as measured by an odor panel, have no established
correlation with odor annoyance thresholds, an ambient standard, based on an odor
panel technique would force States to impose odor emission controls regardless
of whether or not an odor problem existed.
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In this context, it is very important to remember that the fundamental
objective of SIP emission regulations is to attain and maintain the national
ambient standards. This objective obviously requires an ability to quantify
the relationship between changes in pollutant emissions and resulting air
quality. On an even more basic level, the ambient standard approach pre-
sumes that attainment will protect public health and welfare.
These considerations are pertinent to the decision of whether or not to
establish an ambient odor standard. Dispersion modeling techniques for odor
are not well-developed, and their use is limited to short distances and to
nonreactive odorants. More importantly, as noted earlier, there is insufficient
data on which to base a presumption that a given ambient odor level will
prevent nationwide community annoyance problems. While the argument can
certainly be made that a similarly tenuous ambient concentratlon-health/welfare
link exists for most of the current criteria pollutants, the problem is more
significant for odor because the welfare effects that they cause relate to a
single perceptual phenomenon.
This is not to say that the secondary (welfare) standards cannot address
perceptual insults generally or odors specifically. Clearly, Section 302(h)
of the Act defines "welfare effects" with more than sufficient breadth to
cover such impacts. From a practical and technical standpoint, however, the
difficulty of defining the acceptability of a given odor concentration in quanti-
tative terms severely limits the adaptabllty of the NAAQS approach to odor
pollution control.
Thus, the most promising approach for the establishment of a national
ambient air quality standard for odors ^would Involve the determination of
annoyance threshold levels for selected malodorants characteristic of the most
ubiquitous odors or most common emissions. Annoyance thresholds differ
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from simple laboratory hedonic responses because the thresholds are
determined by a population (possibly acclimated) in the context of
normal exposure. Such relationships have not been determined to date.
5.1.4 Implementation - Administrative Considerations
No matter how an ambient odor standard might be phrased, several
practical considerations cast doubt on the wisdom of promulgating such a
standard. The listing and setting of standards is but a prelude to an
enormous administrative undertaking aimed toward eventual compliance.
Within 9 months after the promulgation of ambient standards, all States
are required to adopt and submit to EPA implementation plans, which provide
for the implementation, maintenance and enforcement of the standards.
Attainment of the primary (healthrelated) standard must be achieved
within 3:years-of .the plan's approval by EPA. Attainment of the secondary
(welfarerelated) standard must be achieved in a "reasonable time."
The development of state implementation plans generally imposes large
economic burdens on the government agencies that must prepare them and the
air polluting industries that must comply with them. Comprehensive
emissions inventories and air quality/meteorologic analyses must be
developed, and detailed analyses of alternative emission reduction programs
must be completed. Actual implementation involves the expenditure of
considerable public and private dollars for administration, hardware
controls, plant modifications and other outgrowths of the SIP process.
The 1977 Clean Air Act Amendments, currently being incorporated into the
SIP.s by the States, represent a significant increase in the complexity and
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economic impact of the NAAQS-SIP program. During 1979, the States must
submit plans to EPA for attaining the ambient standards in areas that failed
gir
38
37
to achieve them by the original deadline and SIP revisions for preventing
significant deterioration.
Needless to say, the current SIP revision process is consuming a large
fraction of state, local and federal air pollution control attention and
resources. Thus, in the absence of some very compelling public health or
welfare problem, it seems ill-advised to impose a federal presence in an
area that has been traditionally regulated at the state and local level as a
nuisance-type problem.
Apart from such practical administrative difficulties, federal ambient
odor standards do not appear to represent the most costeffective means of
solving odor problems. Odor pollution, unlike most other forms of air
pollution, is a problem only to the extent that affected individuals perceive
it as a problem. Uniform national standards, even if they could be tied to
odor annoyance (and, at present, they cannot) leave no room for variable
community sensibilities and preferences. Reactions to odor vary, not only
between individuals, but also among different localities. For example,
odors that may lead to numerous complaints in a rural or suburban area may
go virtually undetected in an urban or industrial setting. It is certainly
logical to argue that an odor regulatory strategy should be flexible enough
to accomodate such local sensibilities. The NAAQS program does not offer
such flexibility.
Finally, and most significantly, the current lack of knowledge concerning
odor measurement and modeling would frustrate efforts to implement the air
quality management requirements of prevention of significant deterioration
and nonattainment. Even if an adequate sensory-based standard could be
developed, concepts such as "significant deterioration," "net air quality
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benefit" and "baseline air quality" would be extremely difficult to apply to
odor pollution. The air quality management framework of PSD and nonattain-
ment are difficult enough to apply to conventional pollutants. Attempts to
apply these requirements to a perceptual pollutant such as odor would create
potentially insurmountable implementation problems.
5.2 Federal New Source Performance Standards
5.2.1 Statutory Overview
Section 111 of the Act gives EPA the authority to establish standards of
performance for new and modified stationary sources.* New Source Performance
Standards require emission reductions that reflect that level of control
achievable through application of:
The best technological system of continuous emission reduction which
(taking into consideration the cost of achieving such emission reduction,
any non-air quality impacts and energy requirements) the Administrator
determines has been adequately demonstrated.**39
The two most obvious issues raised by Section 111 are the extent to which
cost must be taken into account and the extent to which an "adequately demon-
strated" system must have proved itself through actual operation.
* A 'modified1 source 1s one that undergoes a physical or operational
change with causes new or increased air pollution. A 'new1 source is one which
commences construction after NSPS regulations applicable to that source are
proposed.40
** Once the standard is set, the owner or operator need not use the control
system identified by EPA, but the system used must achieve the standard. Normally,
installation and operation of a particular control system is not enough;
compliance is based on acutal emissions. Only where it is not feasible for
EPA to establish a numerical emission standard (e.g., petroleum storage
vessels), may the agency establish NSPS requiring specified design or control
techniques. In all other cases, the standard must reflect a quantified
level of emissions from the control system.
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It is not enough that the prototype system be adequately demonstrated and the
cost justified. The Act also requires that the standard actually promulgated be
an "achievable standard" and one "which is within the realm of the adequately
demonstrated system's efficiency". While such a standard may not be set at a
level that is purely theoretical or experimental, it need not necessarily be
41
routinely achieved within the industry prior to its adoption.
The Act requires EPA to establish standards for those categories of
stationary sources that have a significant impact on air pollution. Although
this definition conceivably could apply to all odor sources and, indeed, every
industrial sector of the economy, as of July 1979, EPA had established NSPS's
for 27 categories of stationary sources covering a limited number of
pollutants.
In addition to requiring performance standards for new and modified
stationary sources, Section 111 also requires the states to adopt performance
standards for "designated pollutants" from certain existing sources under
Section lll(d). A "designated" pollutant is one which is subject to
NSPS but which has not been listed as "hazardous" under Section 112 of
the Act or which is not listed as a criteria pollutant under Section 108.
If EPA promulgates an NSPS for a designated pollutant from new sources of a
specific source category, an emission standard must be established by the
States governing emissions of that designated pollutant from all existing
sources within that category. Fluorides from phosphate fertilizer and
27 27
aluminum plants, sulfuric acid mist from acid plants, and total reduced
24
sulfur compounds from kraft pulp mills have been regulated under the
authority of Section lll(d). Rendering plant standards have been considered
but have never been proposed, since odor measuring abilities have been
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deemed inadequate for fair enforcement and since standards for other
pollution sources offered a greater opportunity for improving ambient
air quality.
Promulgation by EPA of standards limiting emissions of odorous materials
from motor vehicles can be considered as a specialized type of New Source
Performance Standard for the purposes of this report. Section 202 of the
Clean Air Act provides EPA with the basic authority to establish standards
applicable to new manufactured motor vehicles and motor vehicle engines.
These standards require the manufacturer to demonstrate compliance with
prescribed emissions limits for prototype vehicles or engines operated
for extended periods before he is eligible to receive a certificate allow-
ing him to proceed with sale of the vehicle or engine to the general public.
To establish such standards, EPA must show that technology is available
to permit compliance at reasonable costs* and that suitable methods of
measurement exist for the material regulated. At this time, no odor
standards applicable to motor vehicles are under development. Consideration
has been given in the past to odor standards applicable to heavy duty diesel
engines designed for trucks and buses. At the present time, however, it
appears that the state of the art in the design of heavy duty motor vehicle
engines has advanced to the point where new and well maintained engines of
these types are not objectionable sources of urban odors. Thus, in this
report, no further consideration will be given to the regulation of
odors under the provisions of Section 202 of the Clean Air Act.
It should be added that poorly maintained vehicles that are powered
by catalyst-equipped gasoline engines or by diesel engines can produce
odors under some circumstances.
*Except for three of the pollutants covered by NAAOS's: HC, CO and NO
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TABLE 3. PRIORITIZED MAJOR SOURCE CATEGORIES FOR NEN SOURCE
PERFORMANCE STANDARD (NSPS) DEVELOPMENT
Priority Source category
1* Synthetic Organic Chemical Manufacturing Industry (SOCMI)
(a) Unit processes
(b) Storage and handling equipment
(c) Fugitive emission sources
(d) Secondary sources
2 Industrial surface coating: cans
3* Petroleum refineries: fugitive sources
4 Industrial surface coating: paper
5 Dry Cleaning
(a) Perchloroethylene
(b) Petroleum solvent
6 Graphic arts
7* Polymers and resins: acrylic resins
8 Mineral wool
9 Stationary internal combustion engines
10 Industrial surface coating: fabric
11 Fossil-fuel-fired steam generators: industrial boilers
12 Incineration: non-municipal
13 Non-metallic mineral processing
14 Metallic mineral processing
15 Secondary copper
*Desianates a significant odor source.
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Table 3 (Cont.)
Priority Source category
16 Phosphate rock preparation
17 Foundries: steel and qray iron
18 Polymers and resins: polyethylene
19 Charcoal production
20* Synthetic rubber
(a) Tire manufacture
(b) SBR production
21 Vegetable oil
22 Industrial surface coating: metal coil
23 Petroleum transportation and marketing
24* By-product coke ovens
25 Synthetic fibers
26 Plywood manufacture
27 Industrial surface coating: automobiles
28 Industrial surface coating: large appliances
29* Crude oil and natural gas production
30 Secondary aluminum
31 Potash
32 Sintering: clay and fly ash
33 Glass
34 Gypsum
35 Sodium carbonate
36 Secondary zinc
*Designates a significant odor source.
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Table 3 (Cont.)
Priority Source category
37* Polymers and resins: phenolic
38 Polymers and resins: urea-melamine
39* Ammonia
40 Polymers and resins: polystyrene
41 Polymers and resins: ABS-SAN resins
42* Fiberglass
43 Polymers and resins: polypropylene
44* Textile processing
45* Asphalt roofing plants
46 Brick and related clay products
47 Ceramic clay manufacturing
•
48* Ammonium nitrate fertilizer
49 Castable refractories
50 Borax and boric acid
51* Polymers and resins: polyester resins
52 Ammonium sulfate
53 Starch
54 Perlite
55 Phosphoric acid: thermal process
56 Uranium refining
57 Animal feed defluorination
58 Urea (for fertilizer and polymers)
59 Detergent
*Designates a significant odor source.
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Table 3 (Cont.)
Other Source Categories
;turf
Organic solvent cleaning
Lead acid battery manufacture
.1
Industrial surface coating: metal furniture
2
Stationary gas turbines
Minor source category, but included on list since an NSPS is being
developed for that source category.
2
Not prioritized, since an NSPS for this major source category has
already been proposed.
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5.2.2 Impact of the 1977 Clean Air Act Amendments
The 1977 Clean Air Act Amendments made several important changes to
Section 111. Some of these changes are quite relevant to the issue of NSPS
for odor sources even though odor control may not be the prime consideration
for regulation development. Two of the most significant changes are:
39
1. Expansion of NSPS Coverage
The new Act directs EPA to greatly expand the coverage of NSPS program
between 1978 and 1982. Specifically, EPA was directed to list all
stationary source categories which had not been made subject to NSPS
when the amendments were enacted. This list was published on August 21,
1979 (44FR49222). The final prioritized list as amended following
public comment is reproduced in Table 3. By August 1980 standards must
be promulgated for 25% of the categories identified. By August 1981,
standards must be promulgated for 75% of the listed categories, and
by August 1982, standards must be established for the remaining 25%.
Several of the listed sources could cause significant odor problems in
many areas, if uncontrolled. Table 3 denotes these sources with asterisks. As an
added benefit of these regulations, reduction of emissions of odorants from
these source categories should produce significant odor reduction benefits
from existing sources in the affected category as they are required to
control those "designated" odorants pursuant to Section lll(d) of the Act.
Although not designed as an odor control strategy, the promulgation of New
Source Performance Standards (NSPS's) will have the effect of reducing
odorous emissions from a variety of important odor sources.
40
2. Dispersion Techniques Not An Acceptable Method of Compliance
The Amendments clarify that neither intermittent or supplemental controls
(those varying with meteorological conditions) nor dispersion techniques
(e.g., tall stacks) may be used as a means of compliance with NSPS. The
new law specifies that the required emissiogQreduction strategy must be a
technological system of continuous control.
The dispersion limitation has a rational basis in the context of criteria
pollutants with known or suspected health effects. Congress has decided that
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for these pollutants, control requirements must reduce total atmospheric
loading as opposed to allowing compliance through improved atmospheric
dilution. Applying this limitation to odors may not be appropriate, however,
since the ultimate objective of any odor emission limitation is to eliminate
odor nuisances rather than to protect public health. Dispersion techniques
and supplemental control systems frequently represent an effective and
economical means of accomplishing this basic objective.
5.3 Conclusions
While new source performance standards and designated pollutant standards
under Section 111 appear to offer more promise than ambient standards as a
federal odor control strategy, technical difficulties still exist. The
fundamental problem is that applying best available control technology does
not guarantee that community odor annoyance levels will not be exceeded.
This problem becomes even more complicated when fugitive odor sources such
as lagoons are involved or when multiple odor sources are located in close
proximity to one another. These factors make it nearly impossible to estimate
the "odor impact" of any particular source or to predict the odor reduction
potential of any given abatement program.
Despite these difficulties, federal new source performance standards
for selected odor sources may be an approach to solving some existing and
avoiding many future odor problems that should be carefully considered. A
well focused approach would avoid "federalizing" the odor pollution field,
while substantially reducing odor emissions from those source categories
that are most frequently the cause of complaints.
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6.0 GENERAL CONCLUSIONS
With the current state of odor pollution technology, each of the regulatory
approaches available under the Clean Air Act is beset by technical uncer-
tainties and varying social preferences toward odors, which tend to undermine
a national regulatory program.
Unambiguous evidence demonstrating adverse health effects of odors has
not been established. Although it is recognized that exposure to
odorants can produce such symptoms as nausea, anorexia, or sleeplessness,
there are no definitive data relating odor exposure to these responses.
Therefore, the available data are insufficient to support establishing a
primary ambient air quality standard for odors.
A similar problem would be encountered in attempting to develop welfare-
based ambient air quality standards. Subjective reactions to odors vary
between both individuals and communities and are highly dependent upon the
context in which the odor is perceived. At the present time, it is not
possible to predict community annoyance from the measured sensory or analytical
properties of odors. Methods are available for determining community annoyance,
but these methods have not as yet been correlated with sensory or analytical
measurements of ambient odor levels. Without reliable data relating ambient
odor levels to community annoyance, it would be difficult to devise an
ambient air quality standard for odors that would ensure the protection of
the public welfare without imposing unnecessarily stringent controls on odor
emission sources.
There are additional technical and administrative implications associated
with establishing National Ambient Air Quality Standards for odors.
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First, odorants and their odors vary widely in character and acceptability
at different intensities, frequencies, and durations. It follows that it is
not possible to set a single ambient air quality standard for all offensive
odors. On the other hand, the sheer number of different odorants, each with
unique odor properties, hinders an odor specific approach to the problem.
Second, the establishment and implementation of ambient air quality
standards is a resource-intensive process and may not represent the most
cost-effective means of solving odor problems.
Third, the current lack of knowledge concerning odor measurement and
the application of dispersion modeling to establish levels of significant
concern for odors would tend to impede the ability of States to implement
National Ambient Air Quality Standards for odors. In many cases, odor
detectability levels or odor annoyance thresholds exceed the analytical
sensitivities of readily available pollution measurement devices. Also,
existing dispersion models are inadequate to predict the impact of alternative
odor abatement strategies on ambient odor levels, particularly in areas
close to several industrial emission sources.
Finally, uniform National Ambient Air Quality Standards leave no room
for variable community preferences. Reactions to odors are dependent upon
local values and aesthetics. It can be argued that an odor regulatory
program should be flexible enough to accommodate local sentiments on this
issue. The NAAQS program does not offer such flexibility.
Regulating odor pollution through New Source Performance Standards
would avoid many of the problems inherent in the ambient air quality standard
approach. Because the majority of odor problems are attributable to a relatively small
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number of source categories, this approach appears to offer a more cost-
effective means of odor control than establishing a NAAQS program for odors.
This approach would allow regulatory agencies to focus their resources on
problem sources without having to expend massive efforts in the monitoring
of ambient odor levels or in devising detailed control strategies.
The primary drawback to control ing odor problems through New Source
Performance Standards is that emission controls for NSPS are not required to
be correlated with the impacts on ambient air quality. Instead, these
regulations are only required to reflect a level of control equivalent to
the best available control technology (with costs and other non-air quality
factors considered), which has been adequately demonstrated. Because some odorants
can persist in causing annoyance at very low concentrations, NSPS's will not
necessarily ensure that odor annoyance is sufficiently abated. The overall
effectiveness of NSPS's in controlling odors is also reduced by the fact
that fugitive sources are hard to identify and assess and that multiple
sources of odors may combine to produce unacceptable effects.
To date, EPA's application of New Source Performance Standards to the
control of odor pollution has been limited. In accordance with the Clean
Air Act Amendments of 1977, however, EPA has greatly expanded the list of
stationary source categories subject to NSPS's. A number of these newly
listed sources are known to cause significant odor problems in many areas.
Establishing NSPS's for these source categories is expected to produce
significant odor reduction as a secondary benefit.
In the final analysis, the basic structure of the Clean Air Act makes
it difficult to tailor odor regulations to the needs and sensibilities of
our nation's local communities. Therefore, it is concluded that specific
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federal odor regulations are not warranted. However, it appears that
federal involvement, in the form of research assistance to develop the
knowledge required to effectively administer local control programs, may be
desirable.
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REFERENCES
1. -Odors from Stationary and Mobile Sources, National Academy of Sciences,
1979.
2, W. H. Prokop, " Developing Odor Control Regulations: Guidelines and
Considerations", JAPCA,' 28, 9 (1978).
3. G. Leonardos, "A Critical Review of Regulations for the Control of
Odors", JAPCA, 24, 461 (1974).
4. See also, Ch. 12 of ref. 1
5. Connecticut Air Pollution Control Regulations, Sec. 19-508-23.
6. Delaware Air Pollution Regulation XIX.
7. Virginia Air Pollution Control Regulations, Section 4.60.
8. Bay Area Air Quality Management District Regulations, Division 15.
9. Illinois Air Pollution Control Rules 102, 801 and 802.
10. Minnesota Regulations APC 9 and APC 10.
11. Texas Air Control Board, Special Project Report No. SP-6, January 13, 1976.
12. See e.g. Rankin vs. Harvey Aluminum. 226 F. Supp. 169 (D. Ore, 1963).
13. Iowa Administrative Code, Chapter 14, Sections 3.1, 4.4, and 14.3
14. Rhode Island Regulation No. 17
15. 0. L. Mills, "Quantitative Odor Measurement", 56th Annual Meeting of
the Air Pollution Control Association, Detroit, Mich., June 9-13, 1963.
16. Kentucky Pules, 401, Sec. 3:020, 4(10).
17. North Dakota Air Pollution Control Regulations, Chapter 33; 15-16.
18. G. Leonardos, D. Kendall, and N. Bernard, "Odor Threshold Determination
of 53 Odorant Chemicals", JAPCA, 1_9, 91(1969).
19. Manufacturing Chemists Association, Part I - Odor Thresholds for
53 Commercial Chemicals, Research Report from Arthur D. Little", Inc.,
October 1968.
20. D.M. Benforado, W.J. Rotella, and D.L. Horton, "Development of an Odor
Panel for Evaluation of Odor Control Equipment," JAPCA, 19, 101 (1969).
21. W.H. Prokop, Annals of the New York Academy of Sciences, 237. 288-308 (1974),
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REFERENCES (Cont.)
22. 79 Mich-App 668 (1977).
23. 25 PA Code 123.31
24. 40 CFR 60.283
25. H.E. Friedrich and D.M. Benforado, Paper 73-271, 1973 APCA Annual Meeting.
26. California Health and Safety Code, Sec. 41700
27. 40 CFR 60
28. 40 CFR 50
29. 40 CFR 51
30. 42 USC Sec. 7410, CAA Sec. 110(c).
31. 42 USC Sec. 7602, CAA Sec. 302(g).
32. Air Program Strategy for Attainment and Maintenance of Ambient
Air Quality Standards and Control of Other Pollutants. U.S. EPA,
1977.
33. Committee on Public Works, National Air Quality Act of 1970, S.Rep.
No. 1196, 91st Cong. 2nd Session 7 (1970).
34. 42 USC Sec. 7409, CAA Sec. 109(b)(l).
35. Rodgers, "Environmental Law", West Publishing Co., 1977, p. 226
36. 42 USC Sec. 7410, CAA Sec. 110(a).
37. Public Law 95-95 Sec. 129(c)
38. 42 USC Sec 7471, CAA Sec. 161
39. 42 USC Sec. 7411, CAA Sec. lll(a)(l)
40. 42 USC Sec. 7423
41. Portland Cement Association v. Ruckelshaus, 48b, F 2d375 (1973).
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APPENDIX
CONCLUSIONS OF THE NATIONAL ACADEMY OF SCIENCES
REGARDING,ODOR MEASUREMENTS
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(1) Odorous emissions and odorous ambient air exhibit various analytical
and sensory properties. Knowledge of the numerical values of some
of these properties is essential to control of the odorous pollution.
(2) Analytical properties of the odorous emissions or odorous ambient
air are characterized by the chemical identities and concentrations
of the odorants present.
(3) Sensory properties of odorous emissions or odorous ambient air consist
of (a) perceived odor intensity, (b) change in intensity with dilu-
tion, (c) odor detectability including odor detection and recognition
thresholds, (d) odor character, and (e) hedonic tone, which refers to
the pleasantness/unpleasantness of the odor.
(4) A determination of the sensory properties of odors from the analytical
data on the odorous samples in most cases is not yet possible.
(5) Various methods are available for measurement of analytical and sensory
properties of odorous emissions and odorous ambient air, but we do not
know how to apply them.
(6) A limited amount of information is available on the performance of the
various measurement methods but is nonetheless sufficient for a
preliminary selection of those which are most suitable and appropriate
for a further development; in particular, needs exist for a more compre-
hensive investigation on their reproducibility, means of improving the
reproducibility, and applicability of various types of emissions and
ambient air odors.
(7) The methodology for estimating the impact of ambient odors is not well
developed.
(8) The existing odcr control regulations, wherever they are quantified in
terms of some ocor property, almost exclusively prescribe some form of
odor detection threshold measurement as a basis for determining the
severity of the odorous pollution; by far the most dominant are the
ASTM D-1391 Syringe Dilution and the Scentometer methods. The present
. state-of-the-art of odor measurement technology is capable of providing
methods that are.free from several shortcomings of these two methods and
can supply more useful information on pollution odors, especially on the
dose/response function for specific odors.
(9) Significant factors in odor measurements of emissions and ambient air
are (a) techniques of the sample acquisition, (b) sample storage, if
any, (c) selection of the most appropriate analytical or sensory
property to be measured, (d) selection of a practical method for
measuring this property in an easily standardizable way, and, in the
case of sensory measurements, selection of procedures essentially free
from various specific effects inherent, in the sensory evaluations, and
(e) performance of the specific methods, especially with respect to the
reproducibility of results when identical odorous samples are evaluated
by different working groups.
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(10) Unless all factors affecting the values of odor thresholds are stan-
dardized, widely different odor thresholds are likely to be reported
for the same samples by different groups. Until then, 'iuta obtained
by the same system, preferably by the same panelists, can be utilized
in monitoring of the efficiency of odor control on a relative basis.
(11) A single odor threshold value does not exist; it is a function of
measurement method variables and may be defined only by reference to
specific measurement systems. There may be a functional "true" value
based on the detection or recognition threshold of an odor in free
ambient air, entering such air from an essentially non-odorous environ-
ment; if this value for the particular odor were known, the odor
measurement system that produces the threshold value closest to such
hypothetical true value, either directly or through some calibration
plot, would be a preferred odor threshold measurement system. Work in
this direction in open air is unknown.
(12) The hedonic tone (pleasantness/unpleasantness) is widely recognized as
a very important factor in determining the relative annoyance potential
of the odorous pollution. Limited experience demonstrates that measure-
ment of hedonic tone produces correlated results when performed in
different laboratories on similar sets of odorants. A broadly accepted
hedonic sample reference scale does not yet exist, but appears feasible.
The relation between the hedonic tone and the annoyance that results
when the same odor is encountered in the context of odorous pollution
is poorly understood, especially for pleasant odors.
(13) Analytical measurements are applicable to monitoring the content of
specific odorants in emissions and in ambient air. In a few cases where
partial correlations have been found between the odor threshold or odor
intensity of the odorous samples and the content of specific odorants,
the analytical measurements can be a valid tool for monitoring the state
of odor control. Analytical data may assist in relating an ambient odor
to its possible sources and in verifying atmospheric dispersion models.
In most odor pollution cases, many odorants are present and analytical
data cannot substitute for sensory data.
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TECHNICAL REPORT DATA
casc read Instructions on the reverse before completing]
1. REPORT NO.
ERA - 450/5-80-003
2.
4. TITLE AND SUBTITLE
Regulatory Options for the Control of Odors
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
February 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
George H. Wahl, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
OAQPS No.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Report to Congress
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report was prepared in response to Sec. 403b of the Clean Air Act
Amendments of 1977. Together with "Odors from Stationary and Mobile Sources
prepared by the National Academy of Sciences it constitutes the Report to
° report ^^^ current state an(j local odor regulations, evaluates
does not appear to be warranted at this time.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
ODORS
Clean Air Act
18. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLAS£ (This Report)
ECURITY CLASS IT
Unclassified
21. NO. OF PAGES
80
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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