c/EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-84-002
March 1984
Air
Benzene Emissions
From Maleic
Anhydride Plants —
Background
Information for
Proposal to Withdraw
Proposed Standards
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EPA-450/3-84-002
Benzene Emissions from Maleic Anhydride
Plants — Background Information for
Proposal to Withdraw Proposed Standards
Emission Standards and Engineering Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1984
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This report has been reviewed by the Emission Standards and Engineering Division of the Office of Air
Quality Planning and Standards, EPA, and approved for publication. Mention of trade names or commercial
products is not intended to constitute endorsement or recommendation for use. Copies of this report are
available through the Library Services Office (MD-35), U.S. Environmental Protection Agency, Research
Triangle Park, N.C. 27711, or, for a fee, from the National Technical Information Services, 5285 Port Royal
Road, Springfield, Virginia 22161.
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ENVIRONMENTAL PROTECTION AGENCY
Background Information
for Benzene Emissions from Maleic
Anhydride Manufacture
Prepared by:
^A
Jack R. Farmer (Date)
Director, Emission Standards and Engineering Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
1. The Feder'al Register notice proposes withdrawal of proposed national
emission standards (45 FR 26660; April 18,1980) for benzene emissions
from existing and new maleic anhydride plants.
2. Copies of this document have been sent to the following Federal
Departments: Labor, Health and Human Services, Defense, Transportation,
Agriculture, Commerce, Interior, and Energy; the National Science
Foundation; the Council on Environmental Quality; State and Territorial
Air Pollution Program Administrators; EPA Regional Administrators; Local
Air Pollution Control Officials; Office of Management and Budget; and
other interested parties.
3. The comment period for review of this document is 30 days from date of
proposal in the Federal Register. Mr. Gilbert H. Wood may be contacted
at (919) 541-5578 regarding the date of the comment period.
4. For additional information, contact:
Gilbert H. Wood
Standards Development Branch (MD-13)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Telephone: (919) 541-5578.
5. Copies of this document may be obtained from:
U.S. Environmental Protection Agency Library (MD-35)
Research Triangle Park, NC 27711
Telephone: (919) 541-2777
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
111
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TABLE OF CONTENTS
Page
1. SUMMARY 1-1
1.1 Summary of Industry Changes Since Proposal 1-1
1.2 Summary of Proposal to Withdraw Proposed Standards 1-2
2. SUMMARY OF PUBLIC COMMENTS 2-1
2.1 Selection of Maleic Anhydride Process Vents for Regulation. . 2- 1
2.1.1 Selection of Source Category 2-1
2.1.2 Priority of Regulating Source Categories 2-14
2.1.3 Risk Estimate Consideration 2-15
2.1.4 Generic Benzene Standard 2-15
2.1.5 Fugitive and Storage Emissions 2-15
2.1.6 Existing Applicable Standards 2-16
2.2 Health and Environmental Impacts 2-16
2.2.1 Dispersion Modeling 2-16
2.2.2 Current Health Impact 2-17
2.2.3 Risk and Expected Plant Life 2-18
2.2.4 Population "At Risk" 2-18
Appendix A: Baseline Emissions Calculations A- 1
Appendix B: Methodology for Estimating Leukemia Incidence and
Maximum Lifetime Risk from Exposure to Benzene
Emissions from Maleic Anhydride Process Vents B- 1
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LIST OF TABLES
Number Page
1-1 Changes in Industry Impacts 1-1
2-1 List of Commenters on the Proposed National Emission
Standard for Benzene Emissions from Maleic Anhydride
Plants 2-2
2-2 Current Estimated Impacts 2-13
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1. SUMMARY
On April 18, 1980, the U.S. Environmental Protection Agency (EPA)
proposed a national emission standard for hazardous air pollutants (NESHAP)
(45 FR 26660) that would regulate benzene emissions from maleic anhydride
plants under the authority of Section 112 of the Clean Air Act as amended.
Public comments were requested on the proposal in the Federal Register
publication. Thirty-five comment letters were received and twenty-three
oral presentations were made at the public hearing. Comments submitted
relevant to the withdrawal decision, along with responses to these
comments, are summarized in this document. The summary of comments and
responses serves as the basis for the proposal to withdraw the proposed
standards.
1.1 SUMMARY OF INDUSTRY CHANGES SINCE PROPOSAL
Since the standards for benzene emissions from maleic anhydride plants
were proposed (April 18, 1980; 45 FR 26660), benzene emissions from this
source category have declined considerably. This reduction is due to plant
closures, feedstock switches, and installation of controls. These changes
are described in more detail in Section 2.2.1 of this document. Table 1-1
compares the nationwide baseline benzene emission and health impacts due to
maleic anhydride process vents at proposal with current estimated impacts.
TABLE 1-1. CHANGES IN INDUSTRY IMPACTS
Impact
Benzene emissions (Mg/yr)
Leukemia incidence (cases/yr)
Maximum lifetime risk
At proposal
5,800
0.46
2.3 x 10-4
Current
960
0.029
7.6 x 10-5
1-1
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1.2 SUMMARY OF PROPOSAL TO WITHDRAW PROPOSED STANDARDS
The Administrator is proposing to withdraw proposal of the benzene
standards for maleic anhydride plants. This decision is based on several
factors, including the broad amount of control currently within the source
category, the relatively small amount of emissions, the trend away from
using benzene as a feedstock, the small estimated leukemia incidence and
maximum lifetime risk at current levels, and the small reduction in these
health risks achievable with add-on controls. This decision is discussed
in greater detail in Section 2.2.1.
1-2
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2. SUMMARY OF PUBLIC COMMENTS
Commenters, affiliations, and EPA docket number assigned each comment
are shown in Table 2-1. Thirty-five letters and documents on the proposed
standard and its background information document (BID) were received.
Because the proposed standards are being proposed for withdrawal , only
comments and responses relevant to that decision are addressed in this
document. Significant comments have been divided into the following 2
categories:
1. Selection of Maleic Anhydride Process Vents for Regulation
2. Health and Environmental Impacts
2.1 SELECTION OF MALEIC ANHYDRIDE PROCESS VENTS FOR REGULATION
2.1.1 Selection of Source Category
Comment: According to one commenter, the Administrator has recognized
that risk from pollutant sources may be insignificant even if the pollutant
is an airborne carcinogen listed under Section 112. According to the
Administrator, "This may occur, for example, because . . . sources have
installed adequate controls on their own initiative or in response to other
regulatory requirements." The commenter believes the maleic anhydride
industry has installed such controls and cited the operating status of the
following plants as examples (Part II Docket Item IV-D-22).
The Reichhold (New Jersey) maleic anhydride plant has closed and will
be dismantled (p. 61-62 of IV-D-22).
Koppers does not intend to reopen its Bridgeville, Pennsylvania,
maleic anhydride plant unless very substantial changes in the economics of
the industry occurred. If the plant reopened, it would operate (as in the
past) with emission controls sufficient to meet the standard (Attachment E
2-1
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TABLE 2-1. LIST OF COMMENTERS ON THE PROPOSED NATIONAL
EMISSION STANDARD FOR BENZENE EMISSIONS FROM MALEIC
ANHYDRIDE PLANTS
Commenter
Docket No.
Affiliation
J. T. Barr
E. A. Treanor
D. B. Rathbun
C. H. Fishman
N. J. King
F. S. Lisella
J. J. Moon
P. F. Infante
IV-D-1, Part I
IV-D-5, Part II
IV-D-2, Part I
IV-D-3, Part I
IV-D-4, Part I
IV-D-5, Part I
IV-D-6, Part I
IV-D-19, Part II
IV-D-7, Part I
IV-D-21, Part II
IV-D-8, Part I
Chemical IV-D-9, Part I
Manufacturer's IV-D-22, Part II
Association (CMA) IV-F-8, Part II
J. M. DeMeester IV-D-10, Part I
Air Products and Chemicals, Inc.
Box 538
Allentown, Pennsylvania 18105
American Petroleum Institute (API)
2101 L Street, Northwest
Washington, D.C. 20037
API
Wilmer & Pickering
1666 K Street, N.W.
Washington, D.C. 20006
Wilmer & Pickering
Center for Disease Control
Department of Health and Human
Services
U.S. Public Health Service
Atlanta, Georgia 30333
Phillips Petroleum Company
Bartlesville, Oklahoma 74004
Occupational Safety and
Health Administration (OSHA)
U.S. Department of Labor
Washington, D.C. 20210
Chemical Manufacturers
Association (CMA)
1825 Connecticut Avenue, N.W.
Washington, D.C. 20009
Dow Chemical Company
Bennett Building
2030 Dow Center
Midland, Michigan 48640
(Continued)
2-2
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TABLE 2-1. LIST OF COMMENTERS ON THE PROPOSED NATIONAL
EMISSION STANDARD FOR BENZENE EMISSIONS FROM MALEIC
ANHYDRIDE PLANTS (Continued)
Commenter
Docket No.
Affiliation
R. K. Meyers
IV-D-11, Part I
R. C. Sterrett IV-D-12, Part I
API
IV-D-13, Part I
IV-F-9, Part II
G. C. lannelli IV-D-14, Part I
F. M. Brower IV-D-2, Part II
L. Behr IV-D-4, Part II
A. F. Montgomery IV-D-6, Part II
M. L. Joseph IV-D-7, Part II
IV-D-20, Part II
D. Rector
IV-D-8, Part II
H. H. Hovey, Jr. IV-D-9, Part II
J. Ruspi
D. J. Goodwin
IV-D-10, Part II
IV-D-11, Part II
Texaco, Inc.
P.O. Box 509
Beacon, New York 12508
Ashland Chemical Company
P.O. Box 2219
Columbus, Ohio 43216
API
General Council of the United
States Department of Commerce
U.S. Department of Commerce
Washington, D.C. 20230
Dow Chemical Company
Private Citizen
64 Maple Lane
Greens Farms, Connecticut 06346
National Science Foundation (NSF)
Washington, D.C. 20550
OSHA
State of Michigan
Department of Natural Resources
Box 30028
Lansing, Michigan 48909
New York State Department
of Environmental Conservation
50 Wolf Road
Albany, New York 12233
The Aerospace Corporation
20030 Century Boulevard
Germantown, Maryland 20767
Illinois Environmental
Protection Agency
2200 Churchill Road
Springfield, Illinois 62706
2-3
(Continued)
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TABLE 2-1. LIST OF COMMENTERS ON THE PROPOSED NATIONAL
EMISSION STANDARD FOR BENZENE EMISSIONS FROM MALEIC
ANHYDRIDE PLANTS (Continued)
Commenter
Docket No.
Affiliation
L. D. Johnson
IV-D-14, Part II
R. M. Gifford
M. Lennon
N. B. Galluzzo
R. W. Russell
M. R. Foresman
D. E. Rickert
R. D. Irons
D. Doniger
P. S. Hewett
D. Glassman
IV-D-15, Part II
IV-D-16, Part II
IV-D-17, Part II
IV-D-18, Part II
IV-D-23, Part II
IV-D-25, Part II
IV-F-2, Part II
IV-F-3, Part II
IV-F-11, Part II
IV-F-4, Part II
IV-F-5, Part II
IV-F-6, Part II
Rohm and Haas Company
Environmental Control Department
Box 584
Bristol, Pennsylvania 19007
Pfizer Chemicals Division
235 East 42nd Street
New York, New York 10017
API
Monsanto Plastics and Resins Co.
800 N. Lindbergh Boulevard
St. Louis, Missouri 63166
Council on Wage and Price Stability
Winder Building
600 17th Street, N.W.
Washington, D.C. 20506
Monsanto Chemical Intermediates Co.
800 N. Lindbergh Boulevard
St. Louis, Missouri 63166
Chemical Industry Institute
of Toxicology (CUT)
P.O. Box 12445
Research Triangle Park, North
Carolina 27709
CUT
Natural Resources Defense Council
1725 I Street, N.W., Suite 600
Washington, D.C. 20006
Reichhold Chemicals, Inc.
601-707 Woodward Heights Boulevard
Detroit, Michigan 48220
USS Chemicals
600 Grant Street
Pittsburgh, Pennsylvania
15230
(Continued)
2-4
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TABLE 2-1. LIST OF COMMENTERS ON THE PROPOSED NATIONAL
EMISSION STANDARD FOR BENZENE EMISSIONS FROM MALEIC
ANHYDRIDE PLANTS (Continued)
Commenter
Docket No.
Affil iation
A. Meyer
IV-F-7, Part II
H. A. Jewett
IV-F-10, Part II
DENKA Chemical Corporation
8701 Park Place Boulevard
P.O. Box 87220
Houston, Texas 77017
Private Citizen
5451 42nd Street, N.W.
Washington, D.C. 20015
2-5
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of IV-D-22). Monsanto has recently completed installation of a thermal
oxidizer at its St. Louis maleic anhydride plant (Attachment E of IV-D-22).
Tenneco has registered its maleic anhydride plant with the New Jersey
Department of Environmental Protection. The State will require Tenneco to
install an incinerator or equivalent controls. Tenneco interprets this
requirement as equivalent to 97 percent control and intends to comply
(Attachment E of IV-D-22).
Response: At proposal, the Administrator determined that maleic anhydride
process vents are a source category that should be regulated for two
reasons: they emit significant amounts of benzene, and based on estimated
maximum lifetime risk and number of leukemia cases, they ranked as one of
the higher priority benzene source categories for regulation (Part I
Docket Item II-I-99). These conclusions were.based on the maleic anhydride
industry's control status during the proposed standard's development.
At proposal, the following maleic anhydride plants were
considered to be operating or operational:
IJSS Chemicals, Neville Island, Pennsylvania;
Reichhold Chemicals, Inc., Morris, Illinois;
Reichhold Chemicals, Inc., Elizabeth, New Jersey;
Ashland Chemical, Neal, West Virginia;
DENKA Chemical Company, Houston, Texas;
Koppers, Bridgeville, Pennsylvania;
Koppers, Chicago, Illinois;
Monsanto, St. Louis, Missouri (20 percent n-butane feedstock);
Tenneco, Fords, New Jersey; and
Amoco, Joliet, Illinois (n-butane feedstock).
In addition, several plants were considered to have process vent control
devices with the following emission reduction capabilities:
Koppers (Pennsylvania), 99 percent control from a waste heat
boiler;
DENKA, 97 percent control from a thermal incinerator;
Reichhold, Morris, 90 percent control from a carbon adsorption
unit;
2-6
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Reichhold, Elizabeth, 97 percent control from a carbon adsorption
unit; and
USS Chemicals, 90 percent control from a catalytic incinerator.
Finally, the proposal noted that the standard would also apply to one
fumaric acid plant producing maleic anhydride as an intermediate product
using a benzene feedstock. Health, environmental, energy, and economic
impacts for this plant were not included in the proposal because EPA had
only become aware of this plant just prior to proposal. This plant is
owned by Pfizer, has a capacity of 12,800 Mg/yr (maleic acid), and is
located in Terre Haute, Indiana. Maleic anhydride producers were initially
identified by EPA through published commercial sales of maleic anhydride.
Unlike other fumaric acid producers, which make both fumaric acid and
maleic anhydride for sale (such as Monsanto and U.S. Steel), Pfizer
produces only fumaric acid for sale. All the maleic acid it produces is
used captively (Part II Docket Item IV-D-22). Because of this, it was not
originally identified as a maleic anhydride producer in calculating impacts
at proposal. However, it produces maleic acid with the same technology,
air oxidation of benzene, as other maleic anhydride producers covered by
the standard. Consequently, Pfizer's maleic anhydride production unit
appropriately was covered by the proposed standard.
Based on information obtained prior to proposal, EPA made estimates of
the health impact due to emissions from these plants. Commenters felt that
these quantitative estimates show the risks to be insignificant and that
the industry did not warrant regulation under Section 112.
Quantitative risk estimates at ambient concentrations involve an
analysis of the effects of a substance in high-dose epidemic!ogical or
animal studies, and extrapolation of these high-dose results to relevant
human exposure routes at low doses. In the case of benzene, the effects
observed were the result of high-dose epidemiological studies. The
mathematical models used for such extrapolations are based on observed
dose-response relationships for carcinogens and assumptions about such
relationships as the dose approaches very low levels or zero.
The risk to public health from carcinogenic emissions may be estimated
by combining the dose-response relationship obtained from this
carcinogenicity strength calculation with an analysis of the extent of
population exposure to the substance through the ambient air. Exposure in
2-7
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this context is a function of both a substance's concentration and
duration.
The exposure analyses are based on air quality models, available
emission estimates from maleic anhydride plants, and approximate population
distributions near these sources. The air quality models used estimated
exposures out to 20 kilometers from the source, and population and growth
statistics were examined. Along with the existing carcinogenic strength
determinations, the information collected was used to provide estimates of
the degree of risk to individuals and the range of increased cancer
incidence expected from ambient air benzene exposures associated with
maleic anhydride plants at various possible benzene emission levels.
The estimated health impacts resulting from the proposed standard were
bounded by a range. These ranges represent 95 percent confidence limits on
two sources of uncertainty in the benzene risk estimates. One source
derives from the variations in dose/response among the three occupational
studies upon which the benzene unit risk factor is based. A second source
involves the uncertainties in the estimates of ambient exposure. In the
former case, the confidence limits are based on the assumption that the
slopes of the dose/response relationships are unbiased estimates of the
true slope and that the estimates are log normally distributed. In the
latter case, the limits are based on the assumption that actual exposure
levels may vary by a factor of two from the estimates obtained by
dispersion modeling (assuming that the source-specific input data are
accurate).
Other uncertainties associated with estimating health impacts are not
quantified here. EPA has extrapolated the leukemia risks identified for
occupationally exposed populations (generally healthy, white males) to the
general population for whom susceptibility to a carcinogenic insult could
differ. The presence of more or less susceptible subgroups within the
general population would result in an occupationally-derived risk factor
that may underestimate or overestimate actual risks. To the extent that
there are more susceptible subgroups within the general population, the
maximum individual lifetime risks may be underestimated.
On the other hand, general population exposures to benzene are much
lower than those experienced by the exposed workers in the occupational
studies, often by several orders of magnitude. In relating the
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occupational experience to the general population, EPA has applied a
linear, non-threshold model that assumes that the leukemia response is
linearly related to benzene dose, even at very low levels of exposure.
There are biological data supporting this approach, particularly for
carcinogens. However, there are also data which suggest that, for some
toxic chemicals, dose/response curves are not linear, with response
decreasing faster than dose at low levels of exposure. At such levels,
the non-linear models tend to produce smaller risk factors than the linear
model. The data for benzene do not conclusively support either hypothesis.
EPA has elected to use the linear model for benzene because this model is
generally considered to be conservative compared to the non-linear
alternatives. This choice may result in an overestimate of the actual
leukemia risks.
EPA estimates ambient benzene concentrations in the vicinity of
emitting sources through the use of atmospheric dispersion models. EPA
believes that its ambient dispersion modeling provides a reasonable
estimate of the maximum ambient levels of benzene to which the public could
be exposed. The models accept emissions estimates, plant parameters, and
meteorology as inputs and predict ambient concentrations at specified
locations, conditional upon certain assumptions. For example, emissions
and plant parameters often must be estimated rather than measured,
particularly in determining the magnitude of fugitive emissions and where
there are large numbers of sources. This can lead to overestimates or
underestimates of exposure. Similarly, meteorological data often are not
available at the plant site but only from distant weather stations that may
not be representative of the meteorology of the plant vicinity.
EPA's dispersion models normally assume that the terrain in the
vicinity of the sources is flat. For sources located in complex terrain,
this assumption would tend to underestimate the maximum annual
concentration although estimates of aggregate population exposure would be
less affected. On the other hand, EPA's benzene exposure models assume
that the exposed population is immobile and outdoors at their residence,
continuously exposed for a lifetime to the predicted concentrations. To
the extent that benzene levels indoors are lower and that people do not
reside in the same area for a lifetime, these assumptions will tend to
overpredict exposure.
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Upon reconsideration, EPA has concluded that the presentation of the
risk estimates as ranges does not offer significant advantages over the
presentation as the associated point estimates of the risk. Further, the
proposal ranges for benzene make risk comparisons among source categories
more difficult and tend to create a false impression that the bounds of the
risks are known with certainty. For these reasons, the benzene risks in
this rulemaking are presented as point estimates of the leukemia risk. EPA
believes that these risk numbers represent plausible, if conservative,
estimates of the magnitude of the actual human cancer risk posed by benzene
emitted from the source categories evaluated. For comparison, the proposal
ranges may be converted into rough point estimates by multiplying the lower
end of the range by a factor of 2.6.
The assumptions necessary to estimate benzene health risks and the
underlying uncertainties have led some commenters on EPA's proposed rules
to suggest that the risk estimates are inappropriate for use in regulatory
decision making. Although EPA acknowledges the potential for error in such
estimates, the Agency has concluded that both the unit risk factor for
benzene and the evaluation of public exposure represent plausible, if
conservative, estimates of actual conditions. Combining these quantities
to produce estimates of the leukemia risks to exposed populations implies
that the risk estimates obtained are also conservative in nature; that is
the actual leukemia risks from benzene exposure are not likely to be higher
than those estimated. In this context, EPA believes that such estimates of
the health hazard can and should play an important role in the regulation
of hazardous pollutants.
The control status of the maleic anhydride industry with regard to
benzene has changed significantly since proposal. First, four plants have
ceased operation permanently. Koppers shut down its Bridgeville,
Pennsylvania, plant in March 1979 and has no plans to reactivate it for
maleic anhydride production (Part II Docket Items IV-D-22, Attachment E,
and II-I-38). Reichhold shut down its Elizabeth, New Jersey, plant in
August 1979, from which pumps and other small equipment have been removed
(Part II Docket Item IV-E-15), and its Morris, Illinois, plant around
August 1982 (Part II Docket Item IV-E-15). Tenneco shut down its Fords,
New Jersey, plant in October 1982 (Part II Docket Item IV-D-32). The
Koppers, Illinois, plant no longer recovers maleic anhydride
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as a by-product of its phthalic anhdride production (Part II Docket Items
IV-E-17 and IV-E-22).
The largest source of uncontrolled benzene emissions, the Monsanto
plant, has installed a thermal incinerator with a waste heat boiler that
can achieve at least 97 percent control of benzene emissions (Part II
Docket Item IV-E-12). Its installation is part of a Monsanto environmental
control and energy conservation program. The device controls volatile
organic compounds from either the n-butane-based or the benzene-based
process (Part II Docket Item IV-D-22, Attachment E). Thirty percent of the
plant's steam requirements are supplied by the maleic anhydride process.
The Monsanto plant currently uses n-butane for 40 percent of its feedstock
needs (Part II Docket Item IV-E-20) and plans to convert remaining capacity
to n-butane by 1985 (Part II Docket Item II-I-42). Only one new plant has
been constructed since proposal and it is 100 percent butane.
The DENKA plant currently is using n-butane for all of its capacity
(Part II Docket Items IV-E-7 and IV-E-14). The Ashland plant has converted
all of its capacity to n-butane (Part II Docket Items IV-E-8 and IV-E-13)
and the USS Chemicals plant has converted part of its capacity to n-butane
(Part II Docket Item IV-E-23). Only the Pfizer plant has not changed
control status since proposal , using only benzene as a feedstock.
Industry commenters maintained that the reduced benzene emissions have
resulted in significant decreases in associated health risks to the extent
that regulation is no longer warranted. They considered the estimated
health risks posed by benzene emissions from maleic anhydride process vents
to be insignificant.
In view of the changes in the maleic anhydride industry following
proposal of the standard, EPA examined the current emission levels, risks,
and potential reductions that could be achieved to determine whether maleic
anhydride process vents continue to pose a significant risk of leukemia and
whether a benzene standard is warranted under Section 112.
Maleic anhydride process vents are now estimated to emit about 960
megagrams of benzene annually from the 3 plants that continue to use
benzene as a feedstock (see Appendix A). This amount is less than 2
percent of total benzene emissions from stationary sources. Estimated
lifetime risk due to these emissions is about 7.6 x 10~5 for the most
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exposed individuals, and over the total exposed population (within 20 km of
each plant) about 0.029 leukemia cases per year is estimated to occur.
These current (or baseline) impacts are presented in Table 2-2. (The
current impacts are actually smaller than estimated here, because they do
not reflect some butane capacity at one of the plants. Because the company
considered the amount of this capacity confidential, the actual estimates
cannot be published. However, this information would not affect any
regulatory decision.)
For comparison, at proposal, 8 plants were identified as benzene
users, emitting 5,800 Mg/yr. These benzene emissions were estimated to
result in about 0.46 leukemia cases per year and a maximum lifetime risk of
about 2.3 x 10~^. Thus, since proposal, benzene emissions have declined by
over 80 percent, estimated annual leukemia incidence by over 90 percent,
and maximum lifetime risk by over 60 percent.
Control techniques that can be applied to maleic anhydride process
vents were discussed at proposal and include carbon adsorption,
incineration, and feedstock substitution (from benzene to n-butane) which
can reduce emissions by about 90, 97, and 100 percent, respectively, from
uncontrolled vents. Although at proposal carbon adsorption was believed to
be able to achieve 97 percent control at maleic anhydride plants, EPA has
revised the estimated reduction to 90 percent because it has not been
demonstrated the carbon adsorption can achieve 97 percent control on a
maleic anhydride vent stream. Applying add-on control technologies of
carbon adsorption or incineration could reduce nationwide benzene emissions
from these sources by roughly 70 to 90 percent, primarily at one plant.
While all new process units are expected to be butane-based, the
technological and economic ability to switch all existing process units is
questionable, even though some have done so. This is primarily due to
factors such as spatial restrictions (process equipment in a butane-based
plant must be about 40 percent larger to produce the same capacity as a
benzene-based plant) or the inability to develop n-butance technology,
which is relatively new and highly proprietary. However, the trend in
recent years for existing plants has been to switch to butane because of
its economic superiority. This trend is expected to continue, with at
least one plant planning to convert its remaining capacity to butane in the
near future.
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TABLE 2-2. CURRENT ESTIMATED IMPACTS
Plant
Koppers, PAa
Reichhold, NJa
Pfizer, INb
Ashland, WV^
Tenneco, NJa
Reichhold, ILa
USS Chemicals, PA
DENKA, TXC
Monsanto, MO
Monsanto, FL
Amoco, IL
Total
Benzene
emissions
(Mg/yr)
NA
NA
780
0
NA
NA
130
0
53
0
0
960d
Leukemia Maximum
incidence lifetime-risk
(cases/yr) (x 10-°)
0.005 76
0.015 11
0.009 3.2
0.029
aClosed since proposal.
^Fumaric acid plant not included at proposal.
cPlant converted to n-butane since proposal.
^Rounded to two significant figures.
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The current estimated incidence and maximum lifetime risk represent
small risks to public health. By both expressions of health risk, the
extent of the hazard posed by this source category is more than an order of
magnitude smaller than for benzene source categories for which standards
are being developed. Additionally, the estimated impact on nationwide
leukemia incidence of further control would be small, ranging from roughly
0.024 to 0.016 cases per year, or a reduction of about 17 to 45 percent
over baseline, depending on the control technology used (carbon adsorption
or incineration). Maximum lifetime risk could be reduced to roughly 5.2 x
10'6 to l.lx 10~5. While a larger percentage reduction can be achieved in
maximum lifetime risk (about 80 to 90 percent), the absolute amount is also
small.
Therefore, in light of the extent of control now exhibited by the
industry, the small portion (less than 2 percent) of total benzene
emissions from stationary sources that maleic anhydride process vent
emissions represent, the trends to discontinue benzene use at existing
plants and to use only n-butane at new plants, the small leukemia incidence
and maximum lifetime risk estimated at current levels, and the small
incremental reductions in health risks achievable with add-on control
technologies, the Administrator has concluded that benzene emissions from
maleic anhydride process vents do not warrant federal regulatory action
under Section 112.
2.1.2 Priority of Regulating Source Categories
Comment: One commenter felt that EPA had not ordered its priorities
properly and was attempting to regulate first one of the smaller sources of
risk due to benzene emissions (Part II Docket IV-D-5). Conversely,
another felt that control of all benzene emissions should be given high
priority (Part II Docket Item IV-D-9).
Response: Initially, after benzene was listed in 1977 as a hazardous air
pollutant (42 FR 29332), standards development for all stationary benzene
source categories was given high priority. As more information was
gathered, it became apparent that some source categories emit much smaller
amounts of benzene than others, indicating that some posed less relative
risk than others. Consequently, to use resources better, the Agency
arranged source categories by priority in terms of estimated maximum risk
2-14
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and leukemia incidence. This was an ordinal ranking to establish
comparative health risks among source categories. This ordering identified
source categories presenting greater relative risk for which regulatory
efforts should proceed immediately. This estimation ranked maleic
anhydride process emissions as one of the higher priority source categories
for regulation (Part I Docket Item II-I-99).
Because industry changes (see Subsection 2.1.1) have substantially
decreased estimated maximum lifetime risk and leukemia incidence, and
likewise the potential reductions in health risk, the Administrator has
concluded that maleic anhydride process vents no longer warrant regulation
at the federal level (see Subsection 2.1.1).
2.1.3 Risk Estimate Consideration
Comment: After recalculating the number of leukemia cases per year due to
benzene emissions from maleic anhydride process vents as 0.079, one
commenter (Part II Docket Item IV-D-22) considered this number close enough
to the number of leukemia cases that EPA deemed reasonable at proposal to
say that no regulation was necessary.
Response: The Agency has reestimated the number of leukemia cases per year
at current baseline levels to be about 0.029 cases per year. This
incidence in conjunction with other factors (see Response 2.1.1) persuaded
the Administrator that a federal regulation was not warranted.
2.1.4 Generic Benzene Standard
Comment: One commenter supported postponement of a standard for benzene
emissions from maleic anhydride plants until it can be incorporated into a
larger, general benzene emissions standard (Part II Docket Item IV-D-15).
Response: The numerous source categories, their varying characteristics,
and the resulting different methods to control each source's emissions make
a general benzene emission standard infeasible. As discussed previously,
the Administrator has concluded that a federal standard for maleic
anhydride process vents is not warranted.
2.1.5 Fugitive and Storage Emissions
Comment: According to one commenter, division of process, fugitive, and
storage emissions into separate documents is confusing and makes comparison
of appropriate information difficult (Part II Docket IV-D-19).
Response: Because various sources emit benzene, categories were
established according to similar emission characteristics and applicable
2-15
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control technology. Although benzene fugitive and storage emissions at
maleic anhydride plants could have been analyzed along with maleic
anhydride process vents, any standards would have been specific only to
fugitive and storage sources at maleic anhydride plants. To cover all
benzene fugitive and storage sources, EPA would have had to propose
identical fugitive and storage standards for each kind of chemical plant
and refinery using or making benzene. To avoid this redundancy, to develop
standards more efficiently, and to cover all like benzene fugitive and
storage sources with uniform requirements, EPA proposed standards for these
sources separately from those for process vents and applied them to several
source categories (46 FR 1165 and 45 FR 83952).
2.1.6 Existing Applicable Standards
Comment: One commenter said the proposed standard would have little health
impact because a standard for organic emissions from existing chemical
plants will control VOC emissions to nearly the level of the proposed
standard (Part II Docket Item IV-D-14).
Response: As discussed previously, based in part on the current levels of
control in the industry, the Administrator has decided not to issue federal
regulations for maleic anhydride process vents.
2.2 HEALTH AND ENVIRONMENTAL IMPACTS
2.2.1 Dispersion Modeling
Comment: The dispersion model used by Cramer, unlike the model developed
by CMA, fails to consider site-specific factors, according to one commenter
(Part II Docket Item IV-D-22, Attachment E). Specific factors that cause
the models to differ include:
Variations in product recovery absorber (PRA) emission rates,
Cramer used 2.34 x 10~3 g/s per MT/yr; CMA used an estimated
industry average of 1.86 x 1Q-3.
Variations in stack height. Cramer used 27.4 meters; four plants
have higher stacks.
Variations in meteorological data. Cramer used worst-case data
for Pittsburgh; CMA data reflected local conditions over an
entire year.
Variations in storage emissions. Cramer assumed storage sources
to be uncontrolled; CMA took account of existing controls on
storage sources.
2-16
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Response: Prior to proposal, EPA did not have enough information on each
plant to perform a detailed modeling analysis. However, such an analysis
is neither necessary for developing proposed standards nor for estimating
the resulting impacts. One or more model plants representing "typical"
plants in the industry are developed that serve as surrogates when
comprehensive information is not available. Such model plants have served
well as estimates in the past and will do so in the future as long as more
complete data are unavailable, or the resources to perform detailed
analyses become exorbitant relative to the benefits derived.
However, when more thorough information is obtained, usually through
public comments, a more accurate analysis can be performed. This is the
case with maleic anhydride plants.
Based on much more detailed emissions data than it had at proposal,
EPA has substantially refined the dispersion modeling. Since proposal, EPA
has modeled each plant individually, based on the emissions data supplied
by the CMA during the public comment period. The revised modeling also
takes into consideration variations in stack parameters and uses
meteorological data from STAR* stations near the plants. Since only
process emissions were considered in the promulgated standards, variation
in storage emissions was not a factor in the revised modeling. A more
detailed description can be found in Appendix B.
2.2.2 Current Health Impact
Comment: Because of changes in the maleic anhydride industry (see
Subsection 2.1.1), one commenter (Part II Docket Item IV-F-8, p. 9-12)
contended that EPA's estimate of 0.496 leukemia case per year under current
control conditions is too high and the correct estimate is 0.0037 leukemia
case per year based on:
Installation of 97 percent control at the Monsanto and Tenneco
plants,
Closure of the Koppers (Pennsylvania) and Reichhold (New Jersey)
plants,
Use of a 97-percent conversion rate for the Ashland plant,
*STAR (stability array) data are standard climatological frequence of
occurrence summaries formulated for use in EPA models and are available
for major U.S. sites from the National Climatic Center, Asheville, North
Carolina. The data consist of frequencies tabulated as functions of wind
speed stability and wind direction classes.
2-17
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Use of plant-specific data in dispersion modeling, and
Use of the Lamm risk factor (0.031 death/106 ppb-person-years).
Response: As discussed in the previous response, the dispersion modeling
has been revised to account for the current operating and control status of
the industry and for the plant-specific data provided by CMA. The results
are contained in Appendix B.
EPA has reviewed the comments regarding its unit risk factor and the
Lamm unit risk factor. In light of the comments, the Agency has revised
its unit risk factor accordingly, although not to the extent desired by the
commenter. The revised unit risk factor is lower by about 7 percent.
Based on the revised dispersion modeling and the Carcinogen Assessment
Group's revised unit risk factor, the Agency has recalculated the estimated
leukemia incidence and maximum lifetime risk under assumed current control
levels (see Appendix B). The leukemia incidence is estimated to be about
0.029 cases per year. The maximum lifetime risk is estimated to be about
7.6 x 10-5.
2.2.3 Risk and Expected Plant Life
Comment: One commenter stated that calculation of estimated lifetime risks
and estimated leukemia cases per year should include consideration of
existing sources' expected operating lifetimes (Part II Docket Item
IV-0-8).
Response: No expected standard operating lifetime for maleic anhydride
plants has been determined (Part II Docket Item IV-D-22). The approximate
risk and leukemia incidence for any time period can be obtained by
prorating the maximum risk and leukemia incidence values.
pollution controls (Part II Docket Item III-B-1). Because of this
uncertainty, however, emissions from all existing plants were used to
determine impacts. The current analysis accounts for plant closures
that have been confirmed, such as those of Koppers, Reichhold, and Tenneco.
Health benefits due to closure are elimination of illnesses, including
leukemia, related to benzene exposure from those plants.
2.2.4 Population "At Risk"
Comment: EPA gave no explanation for choosing a 20-kilometer radius for
assessing human health impacts (Part II Docket Item IV-D-8).
2-18
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Response: The reason for estimating exposure to within 20 kilometers of
stationary sources is based primarily on modeling considerations. Twenty
kilometers was chosen as a practical modeling stop-point. The results of
dispersion models are felt to be reasonably accurate within that distance.
The dispersion coefficients used in modeling are based on empirical
measurements made within 10 kilometers of sources. These coefficients
become less applicable at long distances from the source, and the modeling
results become more uncertain.
2-19
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APPENDIX A
BASELINE EMISSIONS CALCULATIONS
-------
APPENDIX A
BASELINE EMISSIONS CALCULATIONS
A.I INTRODUCTION
This appendix summarizes baseline process benzene emissions from
maleic anhydride process vents and presents the methodology used to
estimate these emissions.
A. 2 EMISSIONS CALCULATIONS
Table A-l presents baseline benzene process emissions, as well as the
parameters used to estimate these emissions for each plant. Though the
Chemical Manufacturers Association (CMA) provided process vent emission
rates (Part II Docket Item IV-F-8) , the basis for these estimates
was not clearly described. Total nationwide process vent benzene emissions
derived from the industry emission rates are 1,010 Mg/yr, or only about 5
percent more than EPA's estimate of 960 Mg/yr. Therefore, the emissions
were calculated using the following equation, developed at proposal and
used to calculate the emissions at proposal.
Emissions Mg/yr - 1-control efficiency x ^PAi x MP^r x pi ^capacity
x 100-benzene conversion rate x 1 Mg
100-94.5 1,000 kg
Control efficiencies were obtained from industry sources (Part II
Docket Items IV-E-10 and IV-E-18). The emission rate 190 kg/hr and
corresponding plant capacity 22,700 Mg/yr and benzene conversion rate (94.5
percent) represent Enviroscience's model plant (Part II Docket Item
II-A-007). Plant capacities were available from literature sources (Part
II Docket Items II-I-010 and IV-J-20). EPA assumed the average conversion
rates of the plants were those provided by the industry (Part II Docket
Item IV-D-22) . For Monsanto, which provided a range of 93 to 97, an
average conversion rate of 95 percent was assumed. The emission estimates
are based on 100 percent production capacity. In fact, these plants are
operating well below rated capacity, and thus actual emissions are lower.
(Note: USS Chemicals has converted some of its capacity to butane
A-l
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TABLE A-l. BASELINE BENZENE PROCESS EMISSIONS
Plant and
1 ocation
Koppers, PAd
Reichhold, NJd
Pfizer, INS
Ashland, WVf
Tenneco, NJd
Reichhold, ILd
USS Chemicals, PA
DENKA, TXf
Monsanto, MO
Monsanto, FL
Amoco, IL
Total
Capacity a
(Mg/yr)
15,400
13,600
12,800
27,200
11,800
20,000
36,400
22,700
28,6009
59,000
27,000
274,500
Benzene
conversion
rateB(%)
NA
NA
95
NA
NA
NA
97
NA
95
NA
NA
Current
control
efficiencyc(%)
NA
NA
0
NA
NA
NA
90
NA
97
NA
NA
Basel ine
benzene process
emissions (Mg/yr)
NA
NA
780
0
NA
NA
130
0
53
0
0
960h
aPart II Docket Items II-I-010 and IV-J-20.
bpart II Docket Item IV-D-22.
cPart II Docket Items IV-E-10 and IV-E-18.
dplant closed permanently since proposal.
eFumaric acid plant not included at proposal.
ffioth plants have converted to n-butane production.
9This represents 60 percent of the total plant capacity.
MA is produced from n-butane.
"Emission total rounded to two significant figures.
The rest of the
A-2
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feedstock. However, because the percent capacity it has converted has not
been made public and because consideration of the amount of product made
from butane would only lower the emission estimates slightly, all
production was assumed to be from benzene).
A-3
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APPENDIX B
METHODOLOGY FOR ESTIMATING LEUKEMIA INCIDENCE AND MAXIMUM
LIFETIME RISK FROM EXPOSURE TO BENZENE EMISSIONS FROM
MALEIC ANHYDRIDE PROCESS VENTS
-------
APPENDIX B
METHODOLOGY FOR ESTIMATING LEUKEMIA INCIDENCE AND MAXIMUM
LIFETIME RISK FROM EXPOSURE TO BENZENE EMISSIONS FROM
MALEIC ANHYDRIDE PROCESS VENTS
B.I INTRODUCTION
The purpose of this appendix is to describe the methodology and to provide
the information used to estimate leukemia incidence and maximum lifetime risk
from population exposure to benzene emissions from maleic anhydride process
vents. The methodology consists of four major components: estimating annual
average concentration patterns of benzene in the region surrounding each plant,
estimating the population associated with each computed concentration, computing
exposure by summing the products of the concentrations and associated populations,
and estimating annual leukemia incidence and maximum lifetime risk from exposure
and concentration estimates. Due to the assumptions made in each of these four
steps of the methodology, there is considerable uncertainty associated with the
lifetime individual risk and leukemia incidence numbers calculated in this
appendix. These uncertainties are explained in Section B.6 of this appendix.
B.2 ATMOSPHERIC DISPERSION MODELING
The long-term version of the Industrial Source Complex (ISCLT) dispersion
model 1 was used to estimate annual average benzene concentrations in the vicinity
of three maleic anhydride plants.
Seasonal or annual stability array (STAR) summaries are principal meteoro-
logical input to the ISCLT dispersion model. STAR data are standard climatological
frequence of occurrence summaries formulated for use in EPA models and available
for major U.S. sites from the National Climatic Center, Asheville, N.C. A STAR
summary is a joint frequency of occurrence of wind speed stability and wind
direction categories, classified according to the Pasquill stability categories.
For this modeling analysis, seasonal STAR summaries were used. Urban mixing
heights and rural mixing heights were used for plants in urban and rural areas,
B-l
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respectively. The ISCLT dispersion model also required user input of ambient
temperatures by stability category and mixing heights by stability and wind
speed categories, for each season. Seasonal temperature and mixing height input
data were computed by averaging hourly CRSTER meteorological preprocessor data
for each category.
The model receptor grid consists of 10 downwind distances located along
16 radials. The radials are separated by 22.5° intervals beginning with 0.0°
and proceeding clockwise to 337.5°. The 10 downwind distances for each radial
are 0.2, 0.3, 0.5, 0.7, 1.0, 2.0, 5.0, 10.0, 15.0, and 20.0 kilometers. For
plants with only one stack, the stack was assumed to be at the center of the
receptor grid. For the U.S. Steel plant with two sources, stacks 502 and 1602
(see Section B.5.1) were assumed to be at the center of the receptor grid and
stacks 501 and 1601 assumed to be 61 meters southeast of the grid center.
The ISCLT output for all plants modeled, consisting of annual concentration
estimates at all 160 receptors, is contained in the docket (Part II, Docket
item IV-J-16). ISCLT dispersion model concentration estimates have been found
to be within a factor of two of measured concentrations in most tests.2
B.3 POPULATION AROUND MALEIC ANHYDRIDE PLANTS
The human exposure model (HEM)3 was used to estimate the population that
resides in the vicinity of each receptor coordinate surrounding each maleic
anhydride plant. A slightly modified version of the "Master Enumeration District
List-- Extended" (MED-X) data base is contained in the HEM and used for population
pattern estimation. This data base is broken down into enumeration district/
block group (ED/BG) values. MED-X contains the population centroid coordinates
(latitude and longitude) and the 1970 population of each ED/BG in the United
States (50 States plus the District of Columbia). For human exposure estimations,
MED-X has been reduced from its complete form (including descriptive and summary
data) to produce a randomly accessible computer file of the data necessary for
the estimation. A separate file of county-level growth factors, based on the
1978 estimates of 1970 to 1980 growth factor at the county level, has also been
created for use in estimating 1980 population figures for each ED/BG. The
population "at risk" to benzene exposure was considered to be persons residing
within 20 km of maleic anhydride plants. The population around each plant was
identified by specifying the geographical coordinates of that plant.
B-2
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B.4 POPULATION EXPOSURE METHODOLOGY
B.4.1 Exposure Methodology
The plant's geographical coordinates and the concentration patterns computed
by the ISCLT were used as input to the HEM. (The HEM also has its own atmospheric
dispersion model. However, the HEM dispersion model, still under development,
is not as detailed as the ISCLT.)
For each receptor coordinate, the concentration of benzene estimated by the
ISCLT and the population estimated by the HEM to be exposed to that particular
concentration are identified. The HEM multiplies these two numbers to produce
population exposure estimates and sums these products for each plant. A two-level
scheme has been adopted in order to pair concentrations and populations prior to
the computation of exposure. The two-level approach is used because the concen-
trations are defined on a radius-azimuth (polar) grid pattern with nonuniform
spacing. At small radii, the grid cells are much smaller than ED/BG's; at large
radii, the grid cells are much larger than ED/BG's. The area surrounding the
source is divided into two regions, and each ED/BG is classified by the region
in which its centroid lies. Population exposure is calculated differently for
the ED/BG's located within each region.
For ED/BG centroids located between 0.1 km and 2.8 km from the emission
source, populations are divided between neighboring concentration grid points.
There are 96 (6 x 16) polar grid points within this range. Each grid point has
a polar sector defined by two concentric arcs and two wind direction radials.
Each of these grid points is assigned to the nearest ED/BG centroid identified
from MED-X. The population associated with the ED/BG centroid is then divided
among all concentration grid points assigned to it. The exact land area within
each polar sector is considered in the apportionment.
For population centroids between 2.8 km and 20 km from the source, a
concentration grid cell, the area approximating a rectangular shape bounded by
four receptors, is much larger than the area of a typical ED/BG (usually 1 km in
diameter). Since there is a linear relationship between the logarithm of
concentration and the logarithm of distance for receptors more than 2 km from
the source, the entire population of the ED/BG is assumed to be exposed to the
concentration that is geometrically interpolated radially and arithmetically
interpolated azimuthally from the four receptors bounding the grid cell.
B-3
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Concentration estimates for 80 (5 x 16) grid cell receptors at 2.0, 5.0, 10.0,
15.0, and 20.0 km from the source along each of 16 wind directions are used as
reference points for this interpolation.
In summary, two approaches are used to arrive at coincident concentra-
tion/population data points. For the 96 concentration points within 2.8 km of
the source, the pairing occurs at the polar grid points using an apportionment
of ED/BG population by land area. For the remaining portions of the grid,
pairing occurs at the ED/BG centroids themselves, through the use of log-log and
linear interpolation. (For a more detailed discussion of the methodology used
to estimate exposure, see Reference 3.)
B.4.2 Total Exposure
Total exposure (persons-yg/m3) is the sum of all multiplied pairs of
concentration-population computed by the previously discussed methodology:
N
Total exposure = z (PiCi) (1)
i=l
where
P-j = population associated with point i,
Ci = annual average benzene concentration at point i, and
N = total number of polar grid points between 0 and 2.8 km and ED/BG
centroids between 2.8 and 20 km.
The computed total exposure is then used with the unit risk factor to
estimate leukemia incidence and maximum lifetime individual risk. This methodology
is described in the following sections. (Note: "Exposure" as used here is the
same as "dosage" in the computer printout, docket item IV-J-16.)
B.4.3 Unit Risk Factor
The unit risk factor (URF) for benzene is 9.9 x 10~8 (leukemia cases per
year)/(pg/m3-person years), as calculated by EPA's Carcinogen Assessment Group
(CAG). This factor is slightly lower than the factor derived by CAG at
proposal. Arguments have been advanced that the assumptions made by EPA
(CAG) in the derivation of a unit leukemia risk factor for benzene represented
"serious misinterpretation" of the underlying epidemic!ogical evidence.
Among the specific criticisms are: CAG (1) inappropriately included in
B-4
-------
its evaluation of the Infante et al. study two cases of leukemia from outside
the cohort, inappropriately excluded a population of workers that had been
exposed to benzene, and improperly assumed that exposure levels were comparable
with prevailing occupational standards; (2) accepted, in the Aksoy et al.
studies, an unreasonable undercount of the background leukemia incidence in
rural Turkey, made a false adjustment of age, and under-estimated the exposure
duration; and (3) included the Ott et al. study in the analysis despite a lack
of statistical significance.
EPA has reexamined and reevaluated each of the three studies. In summary,
EPA concluded that one case of leukemia was inappropriately included from the
Infante et al. study in computing the original unit risk factor. Additionally,
EPA reaffirmed its decision to exclude dry-side workers from that study in
developing the risk factor. The Agency agrees that the Aksoy et al. study was
adjusted improperly for age; however, the exposures and durations of exposures
are still considered reasonable estimates. The Ott et al. study was not
eliminated from the risk assessment because the findings meet the test of
statistical significance and because it provides the best documented exposure
data available from the three epidemiological studies.
Based on these findings, the unit risk factor (the probability of an
individual contracting leukemia after a lifetime of exposure to a benzene
concentration of one part benzene per million parts air) was recalculated. The
revised estimate resulted in a reduction of about 7 percent from the original
estimate of the geometric mean, from a probability of leukemia of 0.024/ppm4
to a probability of leukemia of 0.022/ppm.
B.4.4 Calculation of Estimated Annual Leukemia Incidence
The annual leukemia incidence associated with a given plant under a given
regulatory alternative is the product of the total exposure around that plant in
pg/m^-persons and the unit risk factor, 9.9 x 10~8. Thus,
Annual leukemia incidence = (total exposure) x (unit risk factor), (2)
where total exposure is calculated according to Equation 1.
B-5
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B.4.5 Calculation of Maximum Lifetime Risk
The populations in areas surrounding maleic anhydride plants have various
risk levels of leukemia incidence from exposure to benzene emissions. Using the
maximum annual average concentration of benzene to which any person is exposed,
it is possible to calculate the maximum lifetime risk of leukemia (lifetime
probability of leukemia to persons exposed to the highest concentration of
benzene) attributable to benzene emissions using the following equation:
Maximum lifetime risk = C-j max x (URF) x 70, (3)
where '
Ci,max = tne maximum annual average concentration at any receptor
location where exposed persons reside,
URF = the unit risk factor, 9.9 x 10~8, and
70 years = average individual's life span.
B.5 LEUKEMIA INCIDENCE AND MAXIMUM LIFETIME RISK
B.5.1 Input Data, Assumptions, and Methodology
Population exposures were computed for several different control scenarios
for each plant in order to estimate the leukemia incidence and maximum lifetime
risk at the current level of control.
These emission scenarios consisted of: (1) no control device (also the
assumed startup mode), (2) properly operating (meeting the assumed current
control level) control device, and (3) malfunction. The emission rates and
other dispersion model inputs are shown in Table B-l. The original emission
rates supplied by industry (Part II Docket Item IV-F-8) were adjusted for the
modeling to conform with assumptions made at proposal concerning conversion
rates. The modeling results reflect these adjustments. However, it was determined
after the modeling was performed that such adjustments were unnecessary.
Rather than repeat the modeling effort, the results were prorated using a ratio
of the emission rates supplied by industry (Part II Docket Item IV D-22) to
those that were actually modeled. These results were subsequently used in
calculating the health impacts. The corrected emission rates are shown in
Table B-2. Table B-2 also reflects changes since proposal in published butane
B-6
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TABLE B-l. PLANT SPECIFIC CHARACTERISTICS
DO
I
Emission Stack
ISC model rate
Plant Control Scenario source no. (g/s)
U.S. Steel
U.S. Steel
Monsanto
mal
Monsanto
Monsanto
Pfizer
CI
malfunction,
90% (CI)
TI
function
NCD
97% (TI)
NCD
501
NCD 502
1,601
1,602
3
11
9
13
30.24
18.9
10.08
6.30
82.9
82.9
2.64
22.05
Exit
height velocity
(m) (ra/s)
33.5
33.5
33.5
33.5
45.7
24.5
45.7
23.2
10.0
9.1
18.6
17.0
16.4
44.2
16.4
41.2
Exit
temperature Diameter
(° K) (m)
317
317
589
589
317
317
404
316
1.68
1.37
1.68
1.37
2.134
0.915
2.134
0.610
TI = thermal incineration.
CI = catalytic incineration.
CA = carbon adsorption.
NCD = no control device.
-------
PLANT
TABLE B-2. ADJUSTED BENZENE EMISSION RATES
CONTROL SCENARIO
PERCENT
CONVERSION RATE1
EMISSION RATE, g/s
U.S. Steel 90% (CD
NCD, CI Malfunction
Monsanto 97% (TI)
NCD
TI Malfunction
Pfizer NCD
97
97
952
952
952
95
7.371
73.71
1.98
66
66
22.05
TI = Thermal Incineration
CI = Catalytic Incineration
CA = Carbon Adsorption
NCD = No Control Device
1 Conversion rates supplied by industry in Part II Docket Item IV-D-22,
2 Average of operating range of 93 to 97 percent reported in Part II
Docket Item IV-D-22.
B-8
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capacity in the industry. It should also be noted that the CAG URF was revised
after proposal to 9.9 x 10"^ from 1.06 x 10~?. Plant location and meteorologocal
inputs are provided in Table B-3. Total exposure for each plant under each
scenario is shown in Table B-4. The exposure (person-jag/m^) calculated for
each scenario was then prorated according to the estimated hours per year a given
plant would operate under that scenario. The adjusted exposures for each
plant were used in estimating the exposure associated with the current level of
control.
Based on information from two currently controlled maleic anhydride pi ants,5,6
the hours per year a plant would be under each scenario were estimated. Three
total production unit startups with 8 hours of uncontrolled emissions each and
15 single-reactor startups with 1.5 hours of uncontrolled emissions each were
assumed for a total estimate of 46.5 hours of startup emissions per year.
Twenty malfunctions with 6 hours (maximum allowable time for excess emissions
from malfunctions) of uncontrolled emissions each were assumed for a total
estimate of 120 hours of malfunction emissions per year. Each plant was assumed
to operate at full capacity with no control for both startup and malfunction
emissions. The plant was assumed to operate properly for the remainder of an
8,000-hour operating year, or 7,833.5 hours. Population exposure for each plant
under each regulatory alternative was then calculated as follows:
Population exposure = 46.5 5 + 120 ^ + 7,833.5 p (4)
8,000 F^5UO" 8,000 '
where
S = exposure from startup (Table B-4),
M = expousure from malfunction (Table B-4), and
P = exposure from proper control device operation under each
regulatory alternative (Table B-4).
Population exposure in Table B-4 was multiplied by the CAG leukemia
risk factor of 9.9 x 1Q-8 (see Equation 2) to estimate the annual leukemia
incidence for each plant.
A similar computation is made for determining maximum lifetime risk. The
maximum annual average benzene concentration under each scenario was prorated
the same way as described above for the exposure calculation. Estimated maximum
annual average concentrations for each plant under each scenario are shown also in
B-9
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o
B-3. PLANT LOCATIONS AND METEOROLOGICAL INPUTS
CRSTER model
Urban or meteorologically prepared data
rural used for ambient temperature
mixing Seasona mi xi ng hei ght determi nations
Plant Location Latitude Longitude heights STAR Summary Surface dataUpper air data
U.S. Steel Neville Island, PA 40.5000 80.0833 Urban Pittsburgh, Pa Pittsburgh, PA Pittsburgh, PA
1 hr data 1973-77 1974 1974
Monsanto St. Louis, MO 38.5833 90.2000 Urban St. Louis, MO St. Louis, MO Salem, IL
3 hr data 1973-77 1977 1977
Pfizer Terre Haute, IN 39.3650 87.4150 Rural Indianapolis, IN Indianapolis, IN Patterson, OH
1 hr data 1973-77 1977 1977
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TABLE B-4. EXPOSURE AND MAXIMUM ANNUAL AVERAGE CONCENTRATIONS
Total Exposure Maximum Annual
Ug/m3 - Average Concentrations
Plant Case person) (
U.S. Steel
Pfizer
Monsanto
MCO, CI Malfunction
CI (90 percent)
NCD
NCD
TI Malfunction
TI (97 percent)
1,830,000
120,000
50,800
2,730,000
1,930,000
47 ,300
35.0
0.932
11.0
27.3
8.775
0.173
NCD = No control device; equivalent to startup emissions for situations in
which a plant has a control device.
TI = Thermal incinerator.
CI = Catalytic incinerator.
CA = Carbon adsorber.
B-ll
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Table B-4. These, in turn, were used in estimating the maximum annual average
concentration for each plant for each alternative as follows:
ci,max = 46.5 C-j max + 120 Cj max + 7'83._:5 C-j max (5)
F^JOO" s' -HTJOD" M 8,000 P
where
Ci.max = maximum annual average concentration for a plant under a given
regulatory alternative,
ci ,max = maximum annual average concentration during startup (Table B-4),
O
Ci max = maximum annual average concentration during malfunction
M' (Table B-4), and
Cj jmax = maximum annual average concentration during proper control
P' device operation (Table B-4).
Maximum lifetime risk for a given plant can be found by multiplying
the maximum annual average concentration by the unit risk factor of 9.9 x 10~8
times 70 years (to obtain a lifetime estimate)(see Equation 3). The maximum
lifetime risk for the industry is that due to the plant with the highest
estimated maximum lifetime risk in the industry.
B.5.2 Example Calculations
B.5.2.1 Leukemia incidence. As an example for calculating leukemia
incidence, the U.S. Steel plant is used. The population exposure is
computed according to Equation 4 as follows:
Population exposure = 46.5 M 830,000) + 120 (1,830,000) + 7,833.5 (120,000)
8,000 8,000 8,000
Population exposure = 156,000 person-yg/m3.
Therefore, the annual leukemia incidence (from Equation 2) is:
Annual leukemia incidence = 156,000 x 9.9 x 10'8
Annual leukemia incidence = 0.015.
B-12
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B.5.2.2 Maximum Lifetime Risk. Again, U.S. Steel is used to illustrate the
calculation. The maximum annual average concentration as defined by Equation 5
is as follows:
ci,max = 46.5 (35.0) + 120 (35.0) + 7,833.5 (90.932)
8,000 8,000 8,000
ci,max = ]'64 ^/m3'
Maximum lifetime risk according to Equation 3 is as follows:
Maximum lifetime risk = 1.64 x 9.9 x 10"8 x 70
Maximum lifetime risk = 1.1 x 10~5
B.5.3 Summary of Impacts
The methodology for calculating leukemia incidence and maximum lifetime risk
(described in Section B.5.1) was extended to each plant for the current level of
control. The estimated annual leukemia incidence is shown in Table B-5. The
estimated nationwide leukemia cases per year under the estimated current level
of control is about 0.029. The estimated maximum lifetime risk is shown
in Table B-6. The estimated maximum lifetime risk under the estimated
current level of control is about 7.6 x 10~5.
B.6 UNCERTAINTIES
Estimates of both leukemia incidence and maximum lifetime risk are primarily
functions of estimated benzene concentrations, populations, the unit risk factor,
and the exposure model. The calculations of these variables are subject to a
number of uncertainties of various degrees. Some of the major uncertainties are
identified below.
B.6.1 Benzene Concentrations
Modeled ambient benzene concentrations depend upon: (1) plant configuration;
(2) emission point characteristics, which can be different from plant to plant;
(3) emission rates which may vary over time, and from plant to plant; and
(4) meteorology, which is seldom available for a specific plant. The particular
B-13
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TABLE B-5. ESTIMATED ANNUAL LEUKEMIA INCIDENCE (XIO'2)
Plant Baseline
U.S. Steel 1.5
Pfizer 0.5.
Monsanto 0.9
Total 2.9
TABLE B-6. ESTIMATED MAXIMUM LIFETIME RISK (xlO~6)
Plant Baseline
U.S. Steel 11
Pfizer 76
Monsanto 3.2
B-14
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dispersion model used can also influence the numbers. Using a different
dispersion model, even with the same emission data input, can produce different
results. The dispersion modeling also assumes that the terrain in the vicinity
of the source is flat. For sources located in complex terrain, the maximum
annual concentration could be underestimated by several fold due to this
assumption. Assuming the inputs to the disperion model are accurate, the
predicted benzene concentrations are considered to be accurate to within a
factor of 2.
B.6.2 Exposed Populations
Several simplifying assumptions were made with respect to the assumed
exposed population. The location of the exposed population depends on the
accuracy of the census data in the HEM. In addition, the exposed population is
assumed to be immobile, remaining at the same location 24 hours per day, 365 days
per year, for a lifetime (70 years). This assumption may be counterbalanced to
some extent (at least in the calculation of incidence) by the assumption that
no one moves into the exposure area either permanently as a resident or temporarily
as a transient. The population "at risk" was assumed to reside within 20 km of
each plant, regardless of the estimated concentration at that point. The
selection of 20 km is considered to be a practical modeling stop-point. The
results of dispersion modeling are felt to be reasonably accurate within that
distance. The dispersion coefficients used in modeling are based on empirical
measurements made within 10 kilometers of sources. These coefficients become
less applicable at long distances from the source, and the modeling results
become more uncertain. A numerical estimate of the accuracy of these assumptions
regarding the exposed population is not available.
B.6.3 Unit Risk Factor
The unit risk factor contains uncertainties associated with the occupational
studies of Infante, Aksoy, and Ott, and the variations in the dose/response
relationships among the studies. Other uncertainties regarding the occupational
studies and the workers exposed that may affect the unit risk factor were raised
during the public comment period and focus on assumptions and inconclusive data
contained in the studies. However, those uncertainties have not been quantified.
B-15
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B.6.4 Other Uncertainties
There are several other uncertainties associated with estimating health
impacts. Maximum lifetime risk and annual leukemia incidence were calculated
based on a no-threshold linear extrapolation of leukemia risk associated with a
presumably healthy white male cohort of workers exposed to benzene concentrations
in the parts per million range compared to the risk associated with the general
population, which includes men, women, children, nonwhites, the aged, and the
unhealthy, who are exposed to concentrations in the parts per billion range. It
is uncertain whether these widely diverse segments of the population have
susceptabilities to leukemia that differ from that of workers in the studies.
Furthermore, while leukemia is the only benzene health effect considered in
these calculations, it is not the only possible health effect. Other health
effects, such as aplastic anemia and chromosomal aberrations, are not as easily
quantifiable and are not reflected in the risk estimates. Although these other
health effects have been observed at occupational levels, it is not clear if
they can result from ambient benzene exposure levels. Additionally, benefits
that would affect the general population as the result of indirect control of
other organic emissions in the process of controlling benzene emissions from
maleic anhydride plants are not quantified. Possible benzene exposures from
other sources also are not included in the estimate. For example, an individual
living near a maleic anhydride plant is also exposed to benzene emissions from
automobiles. Finally, these estimates do not include possible cumulative
or synergistic effects of concurrent exposure to benzene and other substances.
B.7 REFERENCES
1. U.S. Environmental Protection Agency. Industrial Source Complex (ISC)
Dispersion Model User's Guide, Volume I. Research Triangle Park,
North Carolina. EPA-450/4-79-031. 1979
2. U.S. Environmental Protection Agency. An Evaluation Study for the
Industrial Source Complex (ISC) Dispersion Model. Research Triangle
Park, North Carolina. EPA-450/4-81-002. 1981.
3. Systems Applications, Inc. Human Exposure to Atmospheric Concentrations
of Selected Chemicals. (Prepared for the U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina). Volume I (NTIS
No. PB81 193252) and Volume II (NTIS No. PB81 193260). May 1980.
B-16
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4. Albert , R. E. Carcinogen Assessment Group's Final Report on Popula-
tion Risk to Ambient Benzene Exposures. U.S. Environmental Protection
Agency. Publication No. EPA-450/5-80-004. January 1979.
5. Letter from Basil, J. A., Reichhold Chemicals, Inc., to J. L. Warren,
Research Triangle Institute, May 2, 1979, (Part II Docket Item II-D-48).
6. Letter from Meyer, A. J., DENKA Chemical Corporation, to J. L. Warren,
Research Triangle Institute, May 30, 1979, (Part II Docket Item II-D-51).
B-17
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c
TECHNICAL REPORT DATA
/Please rtau Instructions on the reverse before completing)
1 REPORT NO.
EPA-450/3-84-002
3 RECIPIENT'S ACCESSION NO.
4 TITLE AND SUBTITLE
|5. REPORT DATE
I March 1984
Benzene Emissions from Maleic Anhydride Plants - ,
Background Information for Proposal to Withdraw Propose^ PE*FO™iNGORG^'ZAT1^ CODE
Standards
AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Air Quality Planning and Standards
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-3056
12. SPONSORING AGENCY NAME AND ADDRESS
DAA for Air Quality Planning and Standards
Office of Air and Radiation
U.S. Environmental Protection Agency
Research Triangle Park. Nf ?7711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This document contains information that formed the basis for the decision to
withdraw standards proposedfor the maleic anhydride industry April 18, 1980 (45 FR
26660). The report includes a summary of industry changes since proposal, a summary
of public comments relevant to the withdrawal decision, and the rationale for the
decision to withdraw proposed standards.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air pollution Hazardous air pollutantjs Air pollution control
Pollution control
National emission standards for hazardous
air pollutants
Benzene
Maleic anhydride
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI !'ield/Group
13B
Unl imited
~rA =om 2220—i ,Rev. 4-77) PREVIOUS ECIT'ON 5 OBSOLETE
iT'->tj -age
I Unclassified
-46_
122 °PICE
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