BACKGROUND DOCUMENT
STANDARDS APPLICABLE TO OWNERS AND OPERATORS
OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL
FACILITIES UNDER RCRA, SUBTITLE C, SECTION 3004
Proposed Additions to Standards For
Hazardous Waste Incineration
(40 CFR 264.342 and 264.343)"'
This document (ms. 1941.33) provides background information
and support for EPA's hazardous waste regulations
U.S. ENVIRONMENTAL PROTECTION AGENCY
January 1981
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025216
CONTENTS
I.
II.
III.
IV.
V.
VI.
VII.
Introduction and Background
A. Content of the Background Document
B. RCRA Mandate for the Regulation
C. Key Definitions
Need for Additions to the Final Incinerator
Standards
Role of Risk Assessment in Regulating
Incinerators
Rationale for the Proposed Regulation
A. Emission Limits for Hazardous Combustion
By- Products
B. Variance to the Destruction and Removal
Efficiency
1. Variance Based on Risk Assessment
2. Limitations of the Risk Assessment
Approach
3. Use of Atmospheric Dispersion
Modeling for Incinerators Emitting
Hazardous Wastes
4. Comparison of Regulations to Regulation
Under the Clean Air Act
5. Use of the Linearized Multi-Stage Model
for Cancer Induction
6. Examples and Sample Calculations for
the Variance
7. Use of the Carcinogen Risk Assessment
Strategy
C. Emission Limit for Metals, Hydrogen Halides
and Elemental Halogens
Text of the Proposed Standards
References
Appendix
Page
1
1
3
4
8
12
18
18
27
28
30
35
49
50
58
64
72
74
78
80
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I. INTRODUCTION AND BACKGROUND
A. Content of the Background Document
This is one of a series of documents providinq support and
background information for regulations issued under Section 3004
of the Resource Conservation and Recovery Act of 1976. Each
Background Document describes a regulation as oriqinallv oro-
posed, summarizes and responds to comments received that relate
to that original proposal, and indicates the Aaencv's rationalp
for final regulations.
On December 18. 1978, the Aqencv proposed standards for
incineration of hazardous waste (43 PR, at 59008). As a result
of that proposal, extensive comments were received. The Agenov
issued a limited set of Interim Status standards on Mav 19,
1980, and responded to some of those comments. Those standards,
Part 265, Subpart O-Incinerators, were issued as interim final
standards, subject to comment.
The Agency has now promulgated Interim Final Standards for
incinerators. These are the maior technical requirements which
provide the basis for issuing permits under Part 122 of the
regulations. These standards are discussed in another backaround
document presenting the rationale for the final incineration
standards, including response to the comments received on the
proposed regulations.
The Phase II regulations relv on a basic performance standard
(a destruction and removal efficiency at 99.99*) with facilitv
specific operating conditions set to attain the performance
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standard. The basis for predicting compliance with the perfor-
mance standard is trial burns. These burns define operating
conditions associated with achievement of the performance standard
The operating conditions thus developed then become part of the
permit and are the basis for continuous compliance monitoring.
The engineering judgement of the permitting official is applied
to define acceptable ranges of these operating conditions and in
the composition of the wastes to which they may be applied.
When sufficient alternative data are available to make these
same determinations, the permitting official may waive the
requirement for a trial burn.
This new proposal is designed to complement the Interim
Final Standards. The proposed requirements allow permit writers
to make variances (e.g., greater or less than 99.99% ORE) to the
basic performance standards.
Specifically, this proposal adds the following to §264.343
Performance Standards;
(1) A procedure for a case-by-case variance from the
minimum ORE of 99.99% when protection of human health
requires a more stringent standard, or allows a less
stringent standard.
(2) A provision which requires that the mass emission
rate of hazardous by-products or products of incomplete
combustion produced during combustion can be no more
than 0.01% of the total mass feed rate of the principal
organic hazardous constituents in the waste.
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(3) A case-bv-case determination for limitations on
emissions of toxic metals, hvdroqen halites and
elemental haloqens.
The Aqency believes that incineration of oraanic hazardous
waste is the primary near-term alternative to land disposal.
Incineration is capable of providing safe destruction of wastes.
Larqe volumes of liquid orqanic wastes not suitable for land
disposal can be reduced to safe gaseous emissions and smaller
amounts of residues (ash, scrubber sludges, etc). Incineration
can thus minimize or eliminate the lonq term impact on human
health and the environment of many hazardous wastes.
B. RCRA Mandate for the Regulation
The Congress of the United States, in Section T004 of
Subtitle C of the Resource Conservation and Recovery Act (RCRA)
of 1976 (PL 94-580), required that the Administrator of the
U.S. Environmental Protection Aqency:
"...promulgate regulations establishinq such performance
standards, applicable to owners and operators of facilities
for the treatment, storage, or disposal of hazardous waste
identified or listed under this Subtitle, as may be necessary
to protect human health and the environment. Such standards
shall include, but need not be limited to, requirements
respecting -...
(3) treatment, storage, or disposal of all such wastes
received by the facility oursuant to such operating
methods, techniques, and practices as may be
satisfactory to the Administrator;
(4) the location, design, and construction of such
hazardous waste treatment, disposal, or storaae
facililties;"
(emphasis added).
The term "treatment" is defined in Section 1004(34) of
the Act to mean:
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"...any method, technique, or orocess, including
neutralization, designed to chanqe the phvsical, chemical,
or biological character or comoosition of anv hazardous
waste so as to neutralize such waste or so as to render
such waste non-hazardous, safer for transport, amenable
for storage, or reduced in volume..."
One objective of incinerating hazardous waste is normallv
to chanqe the physical form or chemical composition of the
waste so as to render it non-hazardous. Incineration mav also
render the waste "safer for transport, amenable for recoverv,
amenable for storage, or reduced in volume." Therefore, incine-
ration is a treatment process within the meaning of the Act,
and the Agency is mandated to produce operating, location,
design, and construction regulations for the incineration of
hazardous waste adequate to protect human health and the
environment.
C. Key Definitions
The definitions given in Part 260 of the Regulations promul-
gated on May 19, 1980 (45 PR at 33066) should aid the reader
in understanding this document. Some of those definitions are
provided here for the readers' convenience. Chanaes from the
definitions proposed on December 18. 1978 (43 PR at 58946) are
discussed if they are relevant to the incineration standards.
1. "Disposal" means the discharge, deposit, injection,
dumping, spilling, leaking, or placing of. anv solid
waste or hazardous waste into or on any land or water
so that such solid waste or hazardous waste or any
constituent thereof may enter the environment or
be emitted into the air, or discharged into anv
waters, including groundwater.
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2. "Disposal Facility" means a facility or oart of a facilitv
at which hazardous waste is intentionallv placed into or
on any land or water, and at which waste will remain
after closure.
3. "Facility" mens all contiguous land, and structures,
other aoputenances and improvements on the land, used
for treating, storing, or disposing of hazardous waste.
A facility may consist of several treatment, storaae,
or disposal operational units (e.g., one or more land-
fills, surface impoundments, or combinations of them).
4. "Fugitive Emissions" means air contaminant emissions
from non-point emission sources, or other than those
from stacks, ducts, or vents.
5. "Hazardous Waste" means hazardous waste as defined in
§261.3 of the Regulations promulgated On May 19, 1980
(45 FR at 33119).
6. "Hazardous Combustion Bv-Products" (products of incomplete
combustion) are hazardous organic constituents formed in an
incinerator from incomplete combustion of POHC's to which
the emission rate limit in
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(2) utilizinq the criteria in paragraph (c) of this
Section.
7. "Incinerator" means an enclosed device using controlled
flame combustion, the orimary ouroose of which is to
thermally break down hazardous waste. Examoles of
incinerators are rotarv kiln, fluidized bed, and liauid
injection incinerators.
8. "Principal Organic Hazardous Constituents (POHC's)" are
the one or more organic constituents in a waste to he
incinerated to which the Destruction and Removal effi-
ciency (DRE) standard in §264.341(a) aonlies. POHC's will
be designated by the Regional Administrator:
(1) prior to a trial burn (defined under $264.344)
(2) based on the results of the waste analysis
performed under $264.345, and
(3) utilizinq the criteria in oaragraoh (c) of this
Section.
9. "Treatment" means any method, technique, or nrocess,
including neutralization, designed to change the
physical, chemical, or biological character or
composition of any hazardous waste so as to neutralize
such waste or so as to render such waste non-hazardous,
safer for transport, amenable for recoveryf amenable
for storage, or reduced in volume.
10. "Trial burn" means an experimental burn of a hazardous
waste in an incinerator in order to evaluate the
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capability of an incinerator of that desiqn to achieve
a specified performance (destruction and removal
efficiency) and to establish the operatinq conditions
(temperature, air flow, etc.) necessary to achieve that
performance for the incinerator oermit.
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II. Need for Additions to the Final Incinerator Performance
Standards
EPA has recognized that incineration of hazardous wastes
is one of the primary waste management techniques which is
preferable to land disposal. In preparing the final standards,
the Agency determined that the following performance standards
were state-of-the-art and were fully supportable based on existing
data:
1. a minimum Destruction and Removal Efficiency (ORE)
of 99.99% based on one or more Principal Organic
Hazardous Constituents (POHC's)
2. a minimum removal efficiency of 99% for hydrogen
choride gas when chlorine was present in the feed
in excess of 0.5%, and
3. a maximum particulate emission standard of 180
milligrams per dry standard cubic meter, corrected
to 12% carbon dioxide in the exhaust gas.
However, as these performance standards were being developed
and finalized, the Agency became increasingly aware of the limita-
tions of these standards. Specifically, major limitations of
these standards are as follows:
1. The ORE of 99.99% is a percentage removal or destruc-
tion standard and does not provide for regulation of
the absolute quantities of POHC's which can be emitted.
By basing the exit emissions to the environment on a
percentage of the rate of waste being fed to the
incinerator, a large incinerator capable of a high
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feed rate would be allowed to emit larqer quantities
of unburned POHC's. A small incinerator unit on the
other hand, which could handle onlv a small waste
feed would be restricted to a smaller quantitv of
emitted. Thus the DRR value of 99.99% is based on a
minimum technoloqy capability and not on the imoact. of
waste emissions on the environment and human health.
Also comments received on the 197B proposed requlations
expressed a need to develop standards which reflect
the deqree of hazard that wastes reoresent. Wastes
which represent a low level of hazard to human health
and the environment should not have as strinaent
regulatory requirements as hiqhly danqerous wastes.
2. The ORE of 99.99% does not account for Hazardous
Combustion by-products (HCBP) which are known to he
formed in the combustion of manv waste substances.
Documentation on the formation and emissions of HCBP' s
is increasinq at a rapid rate throuqh onaoino labora-
tory test work and field samplinq (5,24). HCRP's
may in some situations be more hazardous to the environ-
ment and human health than the wastes beinq fed to
incinerators (POHC's). The Interim Final Standards
provide no regulatory control over HCBP's.
3. Both the ORE of 99.99% and the particulate standard
of 180 mg/DSCM do not regulate the emissions of inor-
ganic hazardous constituents such as heavv metals,
hvdroqen halides and elemental halogens other than HC1.
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The ORE has been documented only for oqanic compounds
which can be reduced by oxidation to CO?, H^O and
other relatively harmless simple compounds. Metals
cannot be destroyed bv oxidation or other chemical
means and can he emitted in a number of forms such as:
solids in the incinerator ash
- vapors in the exhaust qases
- particulates in the exhaust qases
- solid or liquid phase in the scrubber effluent.
In these situations the DRE for orqanic coupounds is
of no value and the particulate standard of 180 mo/D^CM
may allow emissions of sufficient quantities of metals
as solids to endanqer human health and the environment.
The particulate standard is of no value in the case
of emissions of vaporized metals.
4. The control of emissions of elemental haloqens and
hydroqen halides other than HC1, is also lackina in
the Interim Final performance standards. HC1 is con-
trolled with the 99% removal requirement hut EP^ was
unable to find data on emission control svstem perfor-
mance for the other haloqens and hvdroaen halides.
Thus no technoloqy based removal standard was
established.
EPA in identifying these limitations of the final oerformance
standards for incinerators has developed a pronosal to be adde^
to the performance standards in S264.343 which will accomplish
the following:
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Provide for a variance to the ORE of. <*9.99% which diresctlv
links the allowable emission rates of POHCs and HCBP's
to anticioated human health impacts
Place a bench-mark limit on HCBP's similar to the ORE of
99.99%
- Allow emission limits to be established for metals, ele-
mental haloqens, and hydroqen halides based on their imoact
on human health.
Section IV of this Background Document explains the rationale
for this proposal and provides examples of how thev would be
applied.
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III. Role of Risk-Assessment in Regulating Incineration
Many of the comments on the proposed incinerator regulations
(FR December 18, 1978) obiected to the proposal on two manor
grounds: 1) the universally applicable specific design and
operating requirements were too inflexible and not iustifiable
and 2) the performance requirements did not allow variances to
reflect case-by-case situations. EP^ concluded that these com-
ments had merit. The differences in wastes and incinerator
designs argue that operating requirements can not be effectivelv
established on a national basis and that performance standards
should be tailored to case-by-case situations to better ensure
protection of human health and also avoid overlv stringent require-
ments. The Interim Final standards (IF) reflect this approach in
that operating and design standards were drooped and performance
standards promulgated. However, the IF standards do not orovide
for a case-by-case variance to the basic performance standard.
The question of how a variance to the performance standards
would be determined is a manor Question.
The use of a risk assessment approach for emissions from
incinerators has been adopted by EPA as the best available method-
ology to link incinerator performance requirements to human
health impacts. This will be based on an evaluation of risk to
human health posed by the emissions from the incinerator stack.
The proposed standard defines the basic factors involved in this
assessment, including stack emissions, dispersion modeling,
consequent human exposure, and the health effects of the exposure.
It does not define a specific methodoloy.
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If a risk assessment indicates that a more restrictive
emission limit is needed to protect human health, the permit
writer may lower the mass emission rate either bv requiring a
hiqher destruction and removal efficiencv or specifying a lower
waste feed rate or both. In a like manner, the nermit writer
may approve a lower destruction and removal efficiencv (or hiqher
feed rate) if a risk assessment indicates that no significant
impact on human health will result.
The factors of stack emission rates and dispersion models
can be addressed utilizing data from enqineerinq calculations,
the trial burn (stack emissions), and existinq air dispersion
models developed under the Clean Air Act. The determination of
health risk can be based on available EPA "dose response models"
for a certain number of carcinoqens. For other substances, the
estimation of health effects will be less direct, and will depend
on scientific judqments based on the best health effects data
available, or usinq benchmarks of acceptable exposure such as
threshold limit values (TLV's). The methodoloqv for conducting
risk assessments is described more fully in Section IV of this
Background Document.
The Aqency recognizes that in many instances it mav not
be possible to conduct an acceptable risk assessment. When a
risk assessment is not possible or is not requested bv the anoli-
cant or required by the oermit writer, the performance standard
of 99.99 percent DRE will be the basis for oermittinq. SPA
expects that over time, data will be developed to expand risk
assessment capabilities.
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The integration of the variance procedure into the permitt-
ing process could occur in several ways. It could be carried
out prior to the trial burn, after the trial burn but before
issuance of a draft permit for public comment, or as a consequence
of public comment.
A risk assessment to support a variance could be required by
the permit writer or requested by the applicant prior to conduct
of a trial burn. This would be advantageous in that the appli-
cant would know prior to the trial burn whether he would need
to demonstrate a performance other than 99.99% ORE. Thus,
he may be able to avoid having to repeat a trial burn, although
the POHC's and hazardous combustion by-products will not be
finally determined until the trial burn is complete. In most
instances, the trial POHC's, designated by the permit writer
from waste analysis data included with the trial burn plan,
will also be the final POHC's. Hazardous combustion by-products
present a more difficult problem. While a prediction may be
made, the trial burn may indicate different or additional by-
products than those predicted. Should this occur, a risk
assessment for those new hazardous by-products would have to
be performed after the trial burn.
If the applicant were requesting that a risk assessment for
a variance be performance, this request would be included in a
"variance assessment plan" submitted as a part of the trial burn
plan. It would include a description of the proposed methodology
to be used in the assessment. In reviewing the variance assessment
plan, the permit writer would accept or, require modification
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of, the risk assessment methodology, and would designate the
trial POHC's and trial hazardous combustion by-products to he
included in the risk assessment. The risk assessment would be
performed and the results submitted to the oermit writer to
complete the trial burn plan.
In cases where the applicant does not request a variance
assessment, but instead it is required bv the permit writer uoon
review of the trial burn plan, the applicant would be requested
to amend the plan with a methodology for the risk assessment.
Then the process would proceed as described above. In either
case, the performance of the risk assessment prior to conduct of
a trial burn, would add a step to the trial burn aoolication
process. That steo would require that a new part he added to
the trial burn plan. The permit writer would approve that oart
of the plan, and the applicant would comolete the assessment and
submit it to the permit writer to comolete the trial burn olan.
In addition, the applicant or permit writer miqht decide to
provide an opportunity for public comment on the results of the
risk assessment and the variances determined by the oermit writer
prior to conduct of the trial burn.
In cases where a waiver of the trial burn is requested in
Part B of the permit application, the same procedure would be
followed reqardinq a risk assessment variance. It would then
mean that Part B would not be considered final until a determi-
nation of need for, and, where aopropriate, completion of, a
risk assessment were made.
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The second method, for includinq a risk assessment into
the permittinq process is to conduct the assessment following
the trial burn. A probable basis for requirinq a risk assess-
ment at this time would be that the data from the trial burn
revealed hazardous by-products which were not predicted. A
risk assessment at this juncture could be requested by the
applicant in his submittal of trial burn results in Part B of
the permit application, required by the permit writer upon re-
view of those results prior to issuance of a draft permit,
or requested by the public as a part of their review of the
permit application or draft permit. Should this occur, the
applicant would he requested to submit a methodoloqv for the
risk assessment, and upon approval, conduct the assessment and
submit the results to the permit writer, esentiallv as a modifi-
cation of the permit. If review of the results causes the permit
writer to exercise the variance and alter the performance
standard, a repeat of the trial burn may be necessitated. If
so a new trial burn plan would be required, in essence return-
ing to the beqinninq of the permit application process.
In a similar manner limitations on the emission of toxic
metals, elemental halogens and hydrogen halides can be
established. A preliminary trial burn Plan would include a
proposed methodology for assessing acceptable risks associated
with metals and non-organic haloaens (excent HC1), when apolicable.
Upon approval, this assessment would be comoleted and the data
submitted to the permit writer to complete the trial burn nlan.
Based on these data the permit writer would establish emission
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limits on metals and non-orqanic halogens to be achieved
in the trial burn. In this instance, as well as in the variance
procedure, the permit writer or applicant may orovide opportunity
for public comment on the results of the risk assessment and
selected performance standards, orior to conduct of the trial
burn. Thus EPA will determine emission 1imitations of these
inorganic materials in a manner identical to the variance orocedure
for the ORE.
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IV. Rationale for the Proposed Regulation
A. Emission Limits for Hazardous Combustion By-Products
Questions raised by commenters to the proposed reuglations
published December 18, 1978, led the Agency to recognize that in
additon to defining hazardous constituents in the waste burned
in an incinerator, it is important to define hazardous combustion
by-products formed during incineration. Many hazardous wastes
may simply break down and recombine in an incinerator into other
forms of hazardous organic ocmpounds if combustion is not complete.
Thus, even though the principal organic hazardous constituents
(POHC's) in the waste feed may be destroyed in accordance with
the destruction and removal efficiency standard, the stack gases
may contain other hazardous constituents formed during incineration.
The Agency has continued to collect evidence that hazardous
combustion by-products of incineration are a concern. EPA has
sponsored laboratory studies at the University of Dayton of the
thermal decomposition of complex organic halogen compounds which
illustrate the potential for formation of these by-products.(24>
Some of the experimental results are shown in figures 1 through
4 and Table 1.
Thermal decomposition profiles were obtained for the tetra-,
penta-, and hexachlorobiphenyl isomers of PCB, in a flowing air
environment at two (2) seconds residence time, and at the exposure
temperatures shown in Figure 1. There was little difference in
thermal stability noted among the three isomers, except the hexa-
form appears to break more sharply between 650° and 700°C.
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Figure 2 illustrates the production of by-product trichlo-
rodibenzofuran from tetrachlorobiphenyl at temperatures of 650°C
up to approximately 750°C. Figure 3 illustrates the production
of four by-product compounds from the thermal decomposition of
2, 2', 4, 5, 51 -pentachlorobiphenyl in a nitrogen atmosphere.
Figure 4 similarly illustrates the production of several poly-
chlorinated benzene compounds from 2, 21, 4, 4', 5, 5' -hexa-
chlorobiphenyl. Figures 2-4 clearly demonstrate the gene-
ration of by-product compounds at temperature levels commonly
used in incinerators.
Table I shows results from the University of Dayton work
with three selected isomers of PCB's (Polychlorinated biphenyls).
It is noted that a variety of benzenes, biphenyls, dibenzofurans
and other chlorinated ocmpounds were detected as decomposition
by-products.
In order to protect human health and the environment, it is
essential that a performance standard be applied to these sub-
stances as well. In some cases the combustion by-products produced
may be more toxic than the unburned POHC's.(5) This proposed amend-
\
ment to the final regulation requires that the mass emission rate
of hazardous combustion by-products must not exceed 0.01 percent
of the total mass feed rate of POHC's fed to the incinerator.
The rationale for this standard is as follows: if the combustion
by-product were introduced to an incinerator as a principal organic
hazardous constituent (POHC) in the feed, then it would be subject
to the ORE standard of 99.99%. Thus the combustion by-products
should be controlled to the same level as the POHC's.
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K>
O
I
H
O
a
s
H
100
10
2
2
<
5
UJ
or
2
UJ
U
ft
UJ i n
n I U
O
UJ
O.I
001
a—
lf -2.1)0 SCC IN Allt
I
I
1
I
0
50
I
I
2.2.J.5-
lErRACIILOROBIPIIfNYL
2.2.4.5.5* -
PINIACIIIOROBIPIIENYI
2.2.4.4.5.5-
HtXACIIlOUOBIPIIENYl
I
I
500 55O 600 650 700 750
EXPOSURE TEMPERATURE . °C
80O 850
900
950 1000
Source: Duvall, D. S.; Letter on Research Results Utilizing the TDAS; University of
Dayton; to R. A. Games, October 1979.
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130
r
a
a
e.
c
u
0.1
3.01
2,2,5.5-
TETRACHLOROBIPHENYL
IN AIR
500
300
1DOO
EXPOSURE
«?SRAT'JRE
CO
Source: Duvall, S. D.; Letter on Research Results Utilizing the
IDAS; University of Dayton; to R. A. Carnes, October 1979,
FIGURE 2
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100
3»
•4
I
§
(J
a.;
:.ai
-C-
2,2.4,5,5- PENTACHLCROBIPHENYL
IN
I N1T30GENI
tr -2.00 SEC
500
ESC
'.:00
CC!
Source: Duvall, D. S.; Letter on Research Results Utilizing the
IDAS; University of Dayton: to R. A. Carnes, October 1979.
FIGURE 3
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:oo
c
II
u
LI
01
-
I
3
1.3
0.1
2.0:
2,2.4.4.5,5-
HEXACHLORCBIPHENYL
IN AIR
soo
300
TTJffSSATOSS
CO
Source: Duvall, D. S.; Letter on Research Results Utilizing the
TDAS; University of Dayton; to R. A. Games, October 1979,
FIGURE 4
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TABLE I
ORGANIC COMPOUNDS IDENTIFIED FROM THE DECOMPOSITION
OF SELECTED PCB 7SOMERS IN FLOWING AIR AT 725°C FOR
A RESIDENCE TIME OF 2 SECONDS
Isomers
Compounds
trichlorobenzene
biphenyl
tetrachlorobenzene
monochlorobiphenyl
chlorinated compound MW204+
dichlorobiphenyl
pentachlorobenzene
chlorinated compound MW230+
trichlorobiphenyl
dichlorodibenzofuran
tetrachlorobiphenyl
pentachlorobiphenyl
trichlorodibenzofuran
hexachlorobenzene
chlorinated compound MW264+
uetrachlorodibenzofuran
hexachlorobiphenyl
heptachlorobiphenyl
pentachlorodibenzofuran
chlorinated compound MW288+
•f = tentative identification
- = not found
•50'i cc« 95' 4 55' 22*.44' 5.5'
2., z. i j / 3 & i *• / * / 3 / J & i *• i ** i ** / J i J
2 isomers
2 isomers
2 isomers
+
2 isomers
2 isomers
+
+
•f
3 isomers
2 isomers
Source: Duvall, D. S.; Letter on Research Results Utilizing the IDAS;
University of Dayton; to R. A. Carnes, October 1979.
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In addition, any combustion by-products detected will be
subject to an assessment of their impact on human health and the
environment in the same manner as the POHC's. The assessment
method is explained in detail in Section IV-B.
Hazardous combustion by-products which are subject to the
proposed standard will be designated by the permit-writer. This
designation will either take place during the course of the trial
burn based on the analysis of the incinerator emissions, or the
owner or operator may present data in the trial burn plan from
laboratory, pilot or full scale burns where hazardous combustion
by-products have been identified. In cases where a trial burn
waiver is requested, this predictive approach is the only means
of identifying combustion by-products. EPA has research facilities
which may be used to assist owners and operators in this area.
These facilities are discussed in more detail in the Background
Document on Subpart 0 - Interim Final Standards.
Proposed Regulatory Language
§264.342 Designation of principal organic hazardous
constituents and hazardous combustion by-products.
(a) Principal organic hazardous consituents (POHCs) and hazardous
combustion by-products must be treated to the extent required by
the performance standards specified in §264.343.
(b)(i) For each waste feed to be burned, one or more POHC's and
hazardous combustion by-products will be specified from among
those constituents listed in Part 261, Appendix VIII of this Chapter,
This specification will be based on the degree of difficulty of
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incineration of the organic constituents of the waste feed and its
combustion by-products, their concentration or mass, considerina
the results of waste analyses and trial burns or alternative data
submitted with Part B of the facility's permit aoplication.
Organic constituents or by-products which represent the greatest
degree of difficulty of incineration will be those most likelv to
be designated as POHCs or hazardous combustion by-products. Consti-
tuents are more likely to be designated as POHCs or hazardous
combustion by-products if they are present in large Quantities or
concentrations.
(ii) Trial POHCs will be designated for performance of trial burns
in accordance with the procedure specified in Sl22.?7(b) for
obtaining trial burn permits. Trial hazardous combustion by-
products may be designated under the same orocedures.
*****
§264.343 Performance standards.
*****
(d) Incinerators burning hazardous waste must destroy hazardous
combustion by-products designated under S264.342 so that the
total mass emission rate of these by-products emitted from the
stack is no more than .01% of the total mass feed rate of POHCs
fed into the incinerator.
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B. Variance to the Destruction and Removal Efficiency.
In the December 18, 1978 proposed standards for incinerators
no variance procedure to the destruction efficiency was proposed.
Among the many comments received on the 1978 proposal were sug-
gestions that a variance procedure should be established to
account for the differences in the degree of hazard of waste
emissions and to reflect specific site-by-site differences.
EPA agrees that a variance procedure is desirable and some-
times necessary, in order to ensure adequate protection of public
health. The destruction and removal efficiency of 99.99% minimum,
although the most feasible and defendable state-of-the-art
standard, suffers from a significant short coming. The approach
is a percent removal approach, and therefore, allows varying
amounts of actual emissions (mass per unit time) depending on the
composition of the waste (concentration of hazardous constituents)
and the rate of feed of the waste. The 99% removal requirement
for hydrogen chloride suffers from the same shortcomings.
For example, if 10,000 Ibs of a waste were burned, one pound
of a toxic component would be discharged assuming a 99.99% DRE.
In the case of highly toxic components such as some of the dioxin
isomers, such a quantity of mass emissions may be unacceptable,
depending on the mass feed rate of the dioxin containing waste.
The "pure" DRE approach in the example would permit the owner or
operator to discharge one pound over an unspecified period of time
A large incinerator could be discharging large quantities of
hazardous materials over a period extending from minutes to
years while remaining in compliance with the 99.99% DRE.
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1. Variance Based on Risk Assessment
In order to meet the RCRA mandate of protection of human
health and the environment, a procedure is provided in the proposed
regulation for a variance to the DRE based on an assessment of
risk to human health. No particular methodology is provided in
these proposed regulations for performing the risk assessment.
However, the Agency is providing below a sample approach to risk
assessment which it believes will satisfy the requirements of
the proposal. The reader is cautioned that the sample procedure
presented is but one example of how a risk assessment would be
conducted.
The conceptual approach to risk assessment which is presented
as an example in this background discussion is a determination of
individual incremental risk at the point of greatest ground level
concentration of emissions from the incinerator. The actual
presence of individuals at this point, or the number of individuals
is not a factor in the determination. This approach is conserva-
tive in protection of health.
This is a relatively simplified approach to risk assessment.
It assumes, in essence, that any individual is exposed to the
greatest ambient concentration of hazardous constituents, regard-
less of where that may be. It avoids the difficult and often
disputed estimates of actual total population exposure to diffe-
rent concentrations. A total population exposure analysis could
be performed as a part of risk analysis if desired. The conside-
ration of population likely to be exposed can be considered in
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making a judgement of an acceptable risk. The proposed regulation
does not suggest an acceptable risk value.
The cancer induction model is based on life time average
exposure. Thus, short term variations in concentrations need not
be determined for cancer induction. There is a strong history
to support the regulatory and technical basis for the carcingen
risk assessment approach (6,7,8,9,10), Tne reader should analyze
the referenced material for more details.
The overall approach to conducting a carcinogen-based risk
assessment is as follows:
0 Based on data from the trial burn (or alternate data)
the mass emission rate of POHC's, hazardous combustion
by-products, and toxic metals from the incinerator stack
is determined or calculated.
0 Appropriate air dispersion models are applied to these
emissions to predict the ground level ambient concen-
trations .
0 Using the greatest level of ambient concentration, a
cancer risk assessment model (dose response model) is
applied to determine the risk to an individual of deve-
loping cancer.
0 The Regional Administrator (and the public through
hearings) makes a judgement as to whether this level of
risk is acceptable. If it is not, then an acceptable
level of risk is determined. Based on this risk, the
calculations are made in reverse to determine the maximum
permissible level of stack emissions.
0 In order to achieve this level of stack emissions, the
Regional Administrator either can impose a more stringent
level of destruction and removal efficiency and/or can
limit the mass feed rate to the incinerator.
A risk assessment may not be needed in every case. The
impetus for a risk assessment can come either from the Regional
Administrator, the permit applicant, or the public. The burden
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of conducting the risk assessment is on the permit applicant in
all cases. Further, any risk assessments for the purpose of
lowering the ORE (making it less stringent) must come from the
permit applicant. When a risk assessment requested by the Regional
Administrator indicates that a 99.99% ORE provides an acceptable
level of risk, the ORE will remain at 99.99% unless there is a
specific request from the permit applicant.
2. Limitations of the Risk Assessment Approach
There are a number of limitations to the application of the
risk assessment variance approach. They are discussed in the
following paragraphs:
(i) The capability to conduct a quantitative risk assess-
ment at the present time is most clearly defined for certain
carcinogenic substances. Currently, actual dose response data
for inhalation of carcinogens exist for 21 substances (Table II).
These have been evaluated by the EPA Cancer Assessment Group (CAG)
for carcinogenic potency for inhalation. The data exist in the
technical literature to develop dose response curves for virtually
all of the approximately 150 known and suspected carcinogens.
The EPA Cancer Assessment Group (CAG) expects to develop dose
response data for all of the compounds for which adequate data
exist.
(ii) In doing an assessment of risk using cancer data, the
user should be aware that the development of cancer data is a new
science and is subject to degrees of uncertainties and even disa-
greement among those working in the field. Specifically:
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Table II
THE CARCINOGENIC ASSESSMENT GROUP'S PRELIMINARY
CARCINOGENIC POTENCY ESTIMATES ON COMPOUNDS
INCLUDED IN AIR PROGRAM
Compound
Potency Slope (ug/m3)-!
Acrylonitrile
Allyl Chloride
Arsenic
Benzene
Beryllium
Cadmium
Diethyl-Nitrosamine (DEN)
Dimethyl-Nitrosamine (DMN)
Ethylene Dibromide
Ethylene Dichloride
Ethylene Oxide
Formaldehyde
Manganese
Nickel
N-nitroso-N-ethylurea (NEU)
N-nitroso-N-methylurea (NMU)
Perchloroethylene
TCDD
Trichloroethylene
Vinyl Chloride
Vinylidene Chloride
8.50 x ID"5
2.66 x 10~6
3.00 x 10-3
7.40 x ID"6
2.70 x lO'1
1.90 x 10-3
7.18 x ID"2
4.35 x ID"3
5.90 x 10-4
1.20 x lO-5
1.20 x lO"4
6.53 x lO-5
4.0 x ID"4
1.80 x 10-3
6.66 x 10-3
0.67
7.60 x 10~6
121.428
8.80 x 10-7
1.43 x ID"3
5.93 x ID"5
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1. The degree of certainty for carcinogenic effects is
different for each compound.
2. The value of the potency (BH) is different for each
element or compound and directly reflects the degree
of carcinogenicity.
3. The experimental or human exposure data has been
obtained from different exposure routes, ingestion,
inhalation, and skin absorption. Methods of converting
exposure data from one exposure route to another have
been developed using reasonable assumptions. However,
these transformations introduce additional uncertainities
into exposure data. It is important to note that the
potency (Bjj) slopes for the same element or compound
may be different for each of the exposure routes.
Since the field is in a rapid state of development anyone
applying cancer induction data to assess environmental and health
impacts should insure that the data is current.
The cautions above should not be taken as an excuse to avoid
proceeding with a risk assessment based on the cancer effects of
chemicals, as these effects are very real.
(iii) A variance analysis may also be conducted for substances
which do not manifest carcinogenic effects. In this case the
threshold assumption may be used in deriving a criterion. This
assumption is based on the premise that a physiological reserve
capacity exists within the organism which is thought to be depleted
before clinical disease ensues. Alternatively, it may be assumed
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that the rate of damage will be insignificant over the life span
of the organism. The Threshold Limit Value (TLV) for worker
exposure to chemical substances published by the American Confe-
rence for Government Industrial Hygienists (ACGIH) is an example
of a threshold approach for non-carcinogens. The TLV could be
modified by a "safety factor" to derive an ambient exposure
concentration value. There are two major drawbacks to the use
of the TLV. These are:
1. The general population contains subgroups more suscep-
tible than workers, e.g., the old, young children, and
people with illnesses.
2. Workers are exposed typically for eight hours a day.
General populations are exposed on a continuous 24-hour
basis.
Assessments using the TLV approach therefore will require
judgment on the part of the permitting official. The advantages
of using OSHA type standards are:
(1) they apply to a wide variety of toxic substances,
(2) the TLVs are largely inhalation based,
(3) TLVs are continually updated ^D,
(4) TLVs are derived directly from experimental human
and animal studies,
(5) they are already a part of the law,
(6) a methodology exists for handling mixtures of compounds
for which TLVs exist (26). This methodology is for the
workplace and would be modified for application to
ambient usage.
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The history of each TLV should be examined to assess the extent
to which it has assured worker safety in past application.
An alternative is to use the multi Media Environmental Goals
(MEGs) which have been produced by EPA for use in performing
environmental assessments. Some 650 compounds have been analyzed
and ambient concentrations for most of them have been derived
for air, land and water(25).
The carcinogen-based risk assessment approach is based on
a non-threshold concept of disease induction. The threshold
concept considers a level of environmental contamination below
which there is no adverse effect. The TLV is based on this
concept:
"Threshold Limit Values refer to airborne concen-
trations of substances and represent conditions
under which it is believes that nearly all workers
may be repeatedly exposed day after day without
adverse effeet."(25)
A concept for criteria setting, including the TLV, has been
proposed by EPA(25).
(iv) Another factor which complicates risk assessment
is the determination of an acceptable risk. This determination
is as much a political/social decision as a technical one. For
many of the risk assessments the estimated risk will be in a
range of fairly clear acceptability or unacceptability. However,
for those cases in the "gray area", the judgment of the permitting
official and the reaction of the public in the public hearing
process will impact the determination of acceptability.
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3. Use of Atmospheric Dispersion Modeling for Incinerators
Emitting Hazardous Wasted
Dispersion modeling will be used in this application to
estimate the maximum allowable emissions of each hazardous sub-
stance such that the incinerator impact does not exceed any of
the specified ambient air concentrations related to a specified
risk level. That is, each incinerator is modeled to determine
emission limits that are specific to that incinerator. In cases
where several incinerators emit hazardous substances in the same
area, the incinerators should be modeled simultaneously in order
to account for the combined impact of these sources.
The purpose of this section is to provide an overrview of
the role of modeling in reviewing permit applications for hazar-
dous wastes incinerators, indicate the extent to which procedures
are available to do that modeling, and outline some of the data
requirements for the models. This discussion points out that
procedures for dispersion modeling are available, are supplemented
with guidance, and are applicable to hazardous waste incinerators.
Persons involved in a modeling analysis pertaining to the incine-
ration of hazardous wastes should be thoroughly familiar with
both the modeling guidelines and the user's manual of the model(s)
selected. In addition, those conducting the analysis should
have sufficient expertise in air quality modeling to make the
judgments required in the modeling exercise.
Dispersion modeling will be carried out using the recommen-
dations of the EPA Guideline on Air Quality Models(12) The guideline
recommends specific models for various situations. The guideline
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also makes recommendations concerning the source and meteorolo-
gical data to be used in these models. The guideline is expected
to be updated intermittently. In all cases the most recent
version of the guideline should be used.
The Guideline on Air Quality Models discusses both screening
techniques and refined modeling techniques(12).* The screening
techniques are simple calculations and tend to be based on
conservative assumptions. Thus, if screening shows that an allow-
able concentration is not exceeded, then a more refined technique
will give the same conclusion and a more refined analysis is not
required. If on the other hand, a screening results in a concen-
tration in excess of the allowable concentration, it is desirable
to use a more refined technique for estimating atmospheric concen-
trations of hazardous substances. The Guideline has been published
in the Federal Register by EPA and has been tested in the courts
to some extent (12,13,14).
Model Selection
Three factors are most significant in selecting an air
quality model: (1) The nature of the pollutant (i.e., inert vs.
chemically reactive); (2) the nature of the emission source or
sources (e.g., point source); and (3) averaging time (i.e., the
* Some proposed revisions to the Guidelines on Air Quality
Models are discussed in Regional Workshops on Air Quality
Modeling: A Summary Report (Draft). These proposals principally
reflect additional refined models which might be recommended and
greater refinement of guidance on various modeling issues.
However, until revised guidelines are issued (expected in Spring
1981), the 1978 guideline should be followed.
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time period over which concentrations are to be averaged).
Other considerations are sometimes important; for example, the
occurrence of an unusual meteorological phenomenon, terrain
feature or source characteristic will often require the use of a
specialized model. Nevertheless, these factors are useful in
narrowing the choice of models.
Hazardous pollutants should generally be considered chemi-
cally unreactive. This is a conservative assumption in that the
maximum concentration at the point of exposure is derived using
this approach. Even in cases where the pollutant does decompose
in the atmosphere, it is appropriate to use an inert pollutant
model in conjunction with using a half-life approach to simulate
chemical disappearance of the pollutant. Chemical removal may
be considered only if the applicant can demonstrate to the
satisfaction of the Agency that the products of atmospheric
reaction have no effect on the health or welfare of man. Other-
wise, the conservative assumption - that no chemical removal
occurs - should be used.
For modeling purposes, incinerators should clearly be
considered as point sources. In most cases, only one source is
to be modeled, but in some cases, it is appropriate to model the
combined impact of several sources using a multi-source model.
Finally, the averaging time of interest is one year in this
example which is oriented toward limiting the occurrence of cancer
Carcinogenic effects are a function of cumulative exposure to a
compound, and so it is appropriate to use a long-term average
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concentration (i.e., a one-year average) to estimate long-term
exposure to a compound. For pollutants which exhibit other forms
of toxicity such as TLV's, other averaging times, appropriate to
the type of health effect, should be selected.
The Guideline on Air Quality Models^2) specifically addresses
only those pollutants for which a National Ambient Air Quality
Standard has been set. However, the hazardous pollutants being
considered here are analogous to S02 and should be modeled as
being chemically inert or as having first-order decay. Thus,
the techniques used for incinerators emitting carcinogens should
be in accordance with the guideline recommendations for esti-
mating annual average concentrations of SC>2 resulting from one
or more point sources.
When just one incinerator is being considered, the guideline
recommends several suitable screening techniques. A useful
discussion of many of these techniques is provided in Volume 10
(Revised) of the Guidelines for Air Quality Maintenance Planning
and Analysis, entitled Procedures for Evaluating Air Quality
Impact of New Stationary Sources.(15) This document provides
step-by-step approaches for making screening estimates of con-
centrations for cases of flat terrain with no significant meteo-
rological complications and for more complex situations. The
Guideline on Air Quality Models^2) also references several other
documents which discuss screening techniques, some of which are
useful for situations not discussed in Volume 10.
If a refined modeling technique is to be used and if one
incinerator is being considered, the guideline recommends using
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the Single Source {CRSTER) Model.(16) Alternatively, other
models with other output formats may be used.
Screening techniques are not generally available for multi-
source situations. In the multisource situation direct use of
a refined multisource model is necessary. Recommended models
of this type for estimating annual average concentrations include
the Climatological Dispersion Model (CDM/CDMQC) for urban cases(17
For rural cases, models described in the Summary Report of the
Regional Workshops on Air Quality Modeling are recommended(18) .
Data Collection
If refined modeling techniques are used, it is necessary to
obtain several types of data. The Guideline on Air Quality Models
discusses four types of data required by air quality models:
source data, meteorological data, receptor locations, and back-
ground concentration. Source data are primarily used to estimate
emissions rates and plume rise. It may be necessary to model more
than one operating condition. The meteorological data includes
wind speed, wind direction, atmospheric stability, and mixing
height. These data must be representative of the meteorological
conditions at the source. Five years of data should be used to
insure the data are representative. Receptor locations must be
be carefully chosen so that the maximum concentrations is esti-
mated. The guideline gives specific recommendations on locating
receptors. Background concentrations are important when the sum
of the background concentration plus the source impact is not
allowed to exceed a given concentration.
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One additional type of necessary data is information on
whether special circumstances exist that will affect atmospheric
dispersion. For example, it is necessary to determine if the
plume is affected by complex terrain, lake/sea breezes, fumiga-
tion, aerodynamic downwash, or deposition. If so, it may be
necessary to use a model specially designed for those circum-
stances.
Recommended Procedures
The following procedure for determination of emission limi-
tations on hazardous substances is generally recommended:
(1) A screening analysis will be performed to estimate
highest atmospheric concentrations of all compounds
designated as hazardous that are to be emitted by
the incinerator (this analysis will assume that the
incinerator destroys 99.99% of the POHC's introduced
into the incinerator).
(2) Using the health effects information identified for
hazardous compounds emitted, the increase in cancer
risk caused by the highest concentrations estimated in
step (1) for each hazardous substance is calculated.
If more than one substance is involved, increases are
summed to find a total increase in cancer risk.
(3) If the total increase in cancer risk caused by the
incinerator is less than or equal to an acceptable
increment, then 99.99% destruction and removal may be
considered adequate. If the total increase in cancer
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risk is greater than the acceptable increment, then
steps (1) and (2) should be repeated using different
values of acceptability. Additional modeling may be
desirable also.
(4) If a more refined modeling technique also shows an
increase in cancer risk that exceeds the acceptable
increment, maximum allowable emission limits must be
determined. These limits may be calculated by assuming
a linear relationship between emissions and risk.
(5) After a maximum allowable emission rate is determined
from the air modeling and health risk computations, the
permit writer must exercise his best engineering judg-
ment to determine how the emission limit will be
controlled. He may do this by requiring 1} a demonstra-
tion of a higher ORE, 2) specifying in the permit a
maximum feed rate limit for one or more wastes or their
components, or 3) a combination of both 1) and 2).
It should be noted that in some situations the guideline
does not recommend both a screening technique and a more refined
model. First, there are situations where applicable refined
models are not available. When possible, an attempt should be
made to develop refined techniques; however, in many cases
screening techniques will be the only viable option. Second,
there are also situations, most notably when two or more sources
affect the same area, when no suitable screening techniques
exist. If one of the types of modeling techniques is not
possible, the above procedure should be shortened accordingly.
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Figures 5-8 give flow diagrams of the analyses necessary to
determine emissions limitations for incinerators of hazardous
wastes. Four possible situations exist: a single incinerator
emits one hazardous substance (Fig. 5), one incinerator emits
several hazardous substances (Fig. 6), multiple incinerators
emit the same single hazardous substance (Fig. 7), and multiple
incinerators emit several hazardous materials (Fig. 8). The
analyses for the cases of a single incinerator are essentially
equivalent to the procedure described previously. Note that
"estimated concentration" is shorthand for the highest annual
average concentration chosen from a number of receptors. The
analysis for the case of several incinerators emitting the same
one substance is also similar to the procedure discussed above
except that no screening analysis is performed.
As Figure 8 illustrates, the analysis for the case where
several incinerators emit several hazardous substances should be
conducted somewhat differently from other analyses to facilitate
location and determination of the maximum risk. In these ana-
lyses, emissions (units of, e.g., g/sec) are used in the model
to estimate ambient concentrations (e.g., g x sec = g ) ,*
sec m3 m3
and concentrations are then converted into risk factors (e.g.,
g__ x risk units j. mj. = risk units) . In the multiple incinerator,
^3 g
multiple substance case, the emission rate for each substance
should be multipled by the concentration-to-risk conversion factor
sec
m3 are the units of dilution (X/Q).
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Use Screening
Technique to
Estimate
Concentrations
r
\/
Use Model
To Estimate
Concentrations
Translate
Concentrations
Into Risks
Add Risks
\/
Translate
Concentrations
Into Risks
Refined
Model
Availabl
No
Allocate
Risk Reductions
Among
Substances
Figure 6. Recommended Procedure for
One Incinerator Emitting Several
Hazardous Substances.
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Use Multiple
Source Model
to Estimate
Concentrations
Translate
Concentrations
Into Risk
99.99%
Removal
is Adequate
No
Allocate
Risk Reductions
Among Plants
Figure 7. Recommended Procedure for
Several Incinerators Emitting One
Hazardous Substance
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Convert
Emissions
to "Risk
Emissions"
Add "Risk
Emissions"
for each plant
Use Multiple
Source Model to
Estimate Increase
in Risk
Allocate Risk
Reductions
Among Plants
and among
Substances
Figure 8. Recommended Procedure for
Several Incinerators Emitting Several
Hazardous Substances
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Use Screening
Technique to
Estimate
Concentration
Translate
Concentration
Into Risk
99.99%
Removal
Is Adequat
fined
Model
Avail-
able 2
Use Model
To Estimate
Concentration
Translate
Concentration
Into Risk
Figure 5- Recommended Procedure
for One Incinerator Emitting One
Hazardous Substance
99.99%
Removal
Adequate
Acceptable
7 >
Scale
Down
Emissions
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for the substance. This generates quantities labeled here as
"risk emissions" (e.g., g x risk units • m3 = risk units • m3) .**
sec g sec
Multiplying the emissions by a risk weighting places the emissions
of all substances on a common basis. The "risk emissions" for
each plant can then be added to give a total "risk emission" for
the plant. These "risk emissions" may be used in the model to
estimate risk directly (e.g., risk units • m3 x sec = risk units).
sec m3
Using this approach, the task of locating the receptor with the
highest overall risk burden is greatly simplified.*** Using the
total "risk emissions" as input (in place of emission rate) the
multisource model output will display risk factors which have
already been summed for all species and all incinerators.
The "risk-emission" approach is not required for simpler
cases since there is no ambiguity about the location of the
maximum risk. (In the case of one incinerator emitting several
substances/ the maximum concentrations of the substances can all
be expected to occur at the same location).
** As an example: assume that the emission rate is 2 g/sec
and that a concentration of 10"^ g/m3 causes a risk factor of
10~7. Then the "risk emission" would be 2 x 10-7/10~6 =0.2
risk units-m3/sec.
*** Location of highest risk is difficult using the conventional
approach. It is likely that different substances will have their
maximum concentrations at different locations. The location of
greatest total risk may not correspond to the location of any of
the individual substance maxima. Thus determining the maximum
total risk would necessitate a tedious process of converting
concentration to risk factors at a large number of receptors.
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One other noteworthy feature of Figures 5-8 is that once
modeling is performed to estimate risks based on 99.99% destruc-
tion, no further modeling is necessary to determine emissions
limitations. Modeling essentially provides a linear relation-
ship between emissions and concentrations. As a result, a given
percentage reduction in concentration (and associated risk) is
achieved by reducing emissions by the same percentage. A word
of caution, however; if two or more incinerators are controlled
to different degrees, the location of the maximum concentration
may change. In such cases, it is advisable to confirm, possibly
via an additional model simulation, that the proposed emission
reductions will in fact result in risks a_t all locations being
within acceptable limits.
It is important to note that the specific location of the
point or points of maximum concentration is not important to the
strategy proposed in this document. It is sufficient only to
know (1) that they do exist and (2) what the worse case concentra-
tion(s) are or could be. With these two facts, the health impact
(risk) can be determined regardless of whether a receptor is in
fact located at the point of maximum concentration.
One exception to the above strategy might be envisioned. If
an incinerator were located in a remote area where extensive air
modeling could demonstrate that no person(s) would be significantly
impacted under any meteorological condition (at the point of
maximum concentration) then a less restrictive emission rate and
accompanying higher ambient air concentration could be allowed.
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4. Comparison of Regulations to Regulations Under the
Clean Air Act
It is useful to place these regulations in the context of
general approaches to managing atmospheric contamination and in
the context of comparable regulations under the Clean Air Act.
The management of atmospheric contamination can proceed by either
the air quality management approach or the emissions management
approach. In the air quality management approach, the regulations
specify a target air concentration, and modeling is used on a
case-by-case basis to determine the emissions limitations neces-
sary to avoid violating the target air concentration. In the
emissions management approach, the regulations directly specify
emissions limitations (e.g., pounds of emissions per ton of
manufactured product) without regard to the case-by-case impact
on air quality.
Regulatory actions pursuant to the Clean Air Act provide
examples of both types of management approaches. Examples of the
air quality management approach include the National Ambient Air
Quality Standards (NAAQS) and the program for Prevention of Sig-
nificant Deterioration (PSD). The NAAQS are concentrations not
to be exceeded more than once per year in any location, and the
increments under the PSD program represent maximum allowable
increases in concentration for areas meeting NAAQS. Examples of
the emissions management approach include New Source Performance
Standards (NSPS) and National Emissions Standards for Hazardous
Air Pollutants (NESHAP). The NSPS are emission standards for
pollutants having an established NAAQS, and the NESHAP are emission
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standards that apply without regard to the case-by-case impact
on air quality.
These proposed regulations represent a mix of the air quality
management approach and the emissions management approach. That
is, sources of hazardous pollutants must meet an emission standard
based on a 99.99% removal but also may be evaluated for air
quality impact on a case-by-case basis to assess the need for
more stringent emissions limitations. These regulations differ
from regulations under the Clean Air Act in that these regulations
are concerned with the combined effects of several pollutants
rather than the effect of each pollutant individually. Thus,
these regulations could, for example, limit the combined increase
in risk to cancer rather than limiting concentrations of individual
chemicals. However, these regulations are similar to the regula-
tions for PSD in that the concern is with the degradation of
air quality beyond the existing base line and that if more than
one source locates in an area the combined impact must be
considered.
5. Use of the Linearized Multistage Model for Cancer
Induction
Definitions
0 Carcinogenic potency; The proportionality constant,
BH, between the lifetime average daily exposure concen-
tration to an agent, C, and the incremental lifetime
risk of cancer due to that exposure alone, R. It is
defined by the equation R = BjjC. The numerical value
of BH is determined by the human or animal data on
-50-
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the carcinogenic effect of the agent. The units of
BH must be compatible with the units of C, so that
the product of B^ and C is a dimensionless quantity,
since R is a probability and has no units. BH is the
slope of a linear potency curve which passes through
the intercept (C=0, R=0).
0 Threshold; A certain exposure, usually expressed as
a concentration in air or water, below which a given
adverse effect does not occur.
0 Threshold Limit Value (TLV); An air concentration of
an agency established by the American Council of Govern-
ment Industrial Hydienists, below which continued
exposure would not result in adverse impact on health
of workers. Therefore, TLV is a threshold concentration.
Induction
Defining the health impacts of exposure to a given hazardous
substance relies on the use of a dose response model for cancer
induction. The dose response model has been developed by the
Cancer Assessment Group of EPA and others. It has been used in
other ongoing and planned EPA regulations, including National
Emissions Standards for Hazardous Air Pollutants (NESHAPS),
groundwater quality standards, and for other purposes.
In quantitatively assessing the public health risk of air
emission sources, the ambient air concentration of each toxic
chemical is one of the most critical parameters. For toxic
effects besides cancer and mutagenesis, most authorities agree
-51-
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that a threshold concentration exists below which no response
occurs. If the chemicals have caused cancer in animal experiments,
they generally are regarded as potential human carcinogens, and
the risk is proportional to the long-term average concentration,
the proportionality constant of this risk being called BH-
Refer to Table 2 for potency (slope) values developed to date.
The lifetime cancer incidence in the general U.S. population
from all causes is about 0.25, and the extra risk due to expo-
sure to a chemical, R (called the incremental cancer risk), is
equal to R = BH * C, where C is the lifetime average concentration
of that chemical. In cases where several chemicals are present,
the risks may be assured to be additive, so that the total risk
can be represented by:
R = BHi Ci
R is proportional to the total dose a person receives in his/
her lifetime, and is expressed in terms of lifetime average
daily exposure. According to this model, a person exposed to a
given concentration for just n years out of an assumed lifetime
of 70 years, will have a risk of only n - 70 times the risk
experienced by a person exposed to the same degree for a whole
lifetime. If the exposure changes during the lifetime, then the
time-weighted average is the appropriate quantity to use for C^.
-52-
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Table II
THE CARCINOGENIC ASSESSMENT GROUP'S PRELIMINARY
CARCINOGENIC POTENCY ESTIMATES ON COMPOUNDS
INCLUDED IN AIR PROGRAM
Compound Potency Slope (ug/m3)-!
Acrylonitrile 8.50 x 10~5
Allyl Chloride 2.66 x 10~6
Arsenic 3.00 x 10~3
Benzene 7.40 x 1Q-*
Beryllium 2.70 x lO"1
Cadmium 1-90 x 10'3
*y
Diethyl-Nitrosamine (DEN) 7.18 x 10~z
Dimethyl-Nitrosamine (DMN) 4.35 x 10~3
Ethylene Dibromide 5.90 x 10~4
Ethylene Dichloride 1.20 x 10~5
Ethylene Oxide 1.20 x 10~4
Formaldehyde 6.53 x lO"5
Manganese 4.0 x 10~4
Nickel 1-80 x 10~3
N-nitroso-N-ethylurea (NEU) 6.66 x 10~3
N-nitroso-N-methylurea (NMU) 0.67
Perchloroethylene 7.60 x 10~6
TCDD 121.428
Trichloroethylene 8.80 x lO"7
Vinyl Chloride 1-43 x 10~3
Vinylidene Chloride 5.93 x 10"5
-53-
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The potency factors, BH, are estimated from epidemiological
data where possible and from chronic animal carcinogenic experi-
ments when appropriate human evidence is not available. Methods
for deriving BH are discussed in the Water Quality Methodology
Paper.(8,10)
In the regulation of emissions from incinerators, an
approach presented as an example is to first establish an accep-
table or target lifetime individual risk level, and from that
calculate what air concentration limit must prevail in order to
keep the lifetime risk below the target level. By means of air
dispersion modeling, the upper limit ambient concentrations are
converted into maximum emission rates from the incinerator stack.
This, in turn, is translated into incinerator waste feed rates.
Because each chemical has its own characteristic carcino-
genic potency, BH, the total risk will be determined by a potency-
weighted sum of ambient air concentrations. This sum dictates
the critical parameters affecting the incinerator operation. A
technique is discussed in the previous section.
Acceptable Risk
Two quantitative measures of risk have been used by the
Agency in evaluating carcinogenic hazards to populations exposed
to the agent. These are: (1) the individual lifetime cancer
risk, which is defined as the probability that an exposed person
will die of cancer, as opposed to other causes, as a result of
exposure, and (2) the number of cancer cases per year which can
be attributed to the exposure. The individual risk depends on
the carcinogenic effectiveness of the compound, which is called
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its potency, and the concentration of the agent in the exposure
medium, whereas the number of cases depends on the individual
risk and the size of the exposed population.
In deciding what risk is acceptable from a public health
protection point of view, the EPA regulatory offices have concen-
trated on the individual risk. For example, the Pesticides Office
is considering a lifetime risk of 10~6 as acceptably low in the
case of nitrosamine contamination of pesticide products. The
Water Quality Office is requiring the reporting of hazardous
material spills into navigable water that could be used as a
source of drinking water if the risks are greater than 10~6. In
the Food and Drug Administration regulations of animal feed addi-
tives that could cause residues of carcinogenic substances in
edible meat, a risk of less than 10~6 is considered safe enough
to require no use restriction. The water quality criteria for
the protection of human health were based on a risk range of 10~7
to 10-5.(10)
The attitude of many scientists and policy makers is that a
risk of less than 10~7 is usually too small to justify the
resources required to issue and enforce a regulation. A risk of
greater than 10~4 is usually considered serious enough either to
take regulatory action or to require a determination that the
costs of control are prohibitively large. Within the range of
roughly 10~7 to 10"4 the acceptability of a risk is usually a
result of cost-benefit balancing. The Agency has not made a judg-
ment on what constitutes an "acceptable" risk level. The reader
is referred to the Water Quality Criteria documents (10) and other
sources for more background.
-55-
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For noncarcinoqenic substances it is qenerally believed that
risks are zero if the exposure is less than a certain low concen-
tration, or threshold.
For these two classes of compounds the following approaches
could be used: (1) carcinoqens with no currently available
potency value could be assiqned a value based on their structural
similarity to chemicals for which a potencv value is known, and
(2) noncarcinoqens could be treated as threshold pollutants and
an acceptable ambient air concentration could be established as a
certain fraction (say one-tenth) of the Threshold Limit Value
(TLV). Adopt inq the unmodified TLV as the acceptable concentra-
tion for general population exposure is not advised because it is
desiqned for healthy people (factory workers) who voluntarily
assume the risk of exposure in order to work at their nobs.
Multi-media environmental qoal values (MRG's) could also be used.(
For chemicals without an established TLV, the Procedure
outlined in the health methodoloqy of the Water Quality Criteria
documents (^ u) could be followed. It is a procedure for sett inq
acceptable limits based on toxicity information.
Multistage Mod el
The mathematical model chosen for extrapolation of cancer
risks from the hiqh doses used in animal experiments to low doses
of environmental exposure is the linearized multistaqe model.
This approach is described in the Water Qualitv Criteria document
procedures.(10) Althouqh that document describes the procedure
in detail, the major features are reoeated here.
-56-
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The model is a general curve-fitting procedure which can fit
a monotonically increasing function of dose to the animal tumor
incidence data. The assumption is made that the tumor incidence
is linearly related to the dose with no threshold. This is in
accord with the assumption of other regulatory agencies, as
manifested by the Interagency Regulatory Liaison Group (IRLG)
guidelines for the evaluation of carcinogenic risk.*19) For some
compounds, a threshold at low doses might exist. If this were
the case, then the extrapolation procedure used here is regarded
as giving a reasonable upper limit of the risk at low doses (i.e.,
is conservative). Future research on mechanisms of carcinogenic
action might result in a more definitive quantitative statement
of risk. The structure of the proposed regulation would allow
use of any technically acceptable approach.
Fundamental Cancer Model Assumptions
The linear non-threshold model assumes that the lifetime
total dose is the basis for the risk estimation. In the animal
experiments which form the basis for the procedures the dose
rate is usually constant throughout the lifetime. If the same
lifetime dose were given within a short fraction of the lifetime,
then the result would be the same under the linear assumption.
However, some evidence exists that large amounts given within a
short time cause more damage, at least for acute toxicity effects,
than the same amount spread out over a much larger time. There
is some evidence that these non-linear dose rate effects also
occur in carcinogenesis experiments, at least in the one case of
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vinyl chloride. However, the information on this point is very
sparse. The only generality that can be made is that as long as
the dose rate for environmental exposures is less than the equi-
valent dose rate in the lifetime animal bioassay with constant
dosing, the potency factors derived according to these procedures
can be used. But if the dose rates become significantly larger,
then calculated risks might be too small. The correction factors
for these short range high dose situations are unknown. It is
unlikely that environmental doses would be higher than experimental
doses.
The instances of pulsed doses to populations which are large
enough to exceed the animal dose rate are expected to be very
rare, since animal doses are typically many orders of magnitude
larger than environmental doses.
6. Examples and Sample Calculations for the Variance
This section presents data and examines calculations to
illustrate how the variance (override) approach may work. In
general, conservative approaches have been adopted to illustrate
certain points. Different acceptable risk levels and model
assumptions have been selected to illustrate the sensitivity of
the approach.
For assessment of carcinogens the process begins with the
types of data illustrated in Table 2. "The Carcinogenic Assess-
ment Group's Preliminary Carcinogenic Potency Estimates on
Compounds included in Air Program". The data are used in the
following equation:
-58-
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Concentration = -Risk
Potency (slope)
Where:
Concentration = The lifetime average exposure level to a
carcinoqenic substance.
Risk = The incremental increase in cancer deaths.
Potency = The estimated slope of the straight 1ine
which passes throuqh the intercept ooint
of the dose-risk curve.
By using this relationship, calculation of the long-term air
concentrations for anv risk level can be done auicklv. As seen
in Table 2, a wide range of potency slopes have been determined
all the way from trichlorethylene with a value of 8.8 x 10~7
(ug/m3)"1 to TCDD with a potency of about 121 (ua/m3)"1.
The next steos are illustrated in Table 3. Usina the potency
slope (BH) for a number of organic comounds and five metals, the
air concentration (C) in mq/m3 is calculated for a risk of 1 x in~s(
Next a dispersion model is selected, assumptions are made for the
model and the allowable stack emission rate (E) is determined. In
the last column the maximum allowable waste feed rate is calculated
based on the maximum allowable emission rate (5). This calculation
is straight-forward and is also shown in Tables III and IV for
different air dispersion model conditions and risk levels.
Table 4 illustrates the impact of different conditions
imposed in the air modeling exercise. In this table the risk is
the same (1 x 10~5) but the stability class is more stringent
and the effective stack height has been lowered from 150 meters
to 30 meters. The allowable emission rate and thus the allowable
-59-
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TABLE 3 : ESTIMATION OF ALLOWABLE MASS FEED BASUU ON A RISK Of IxlO"5,
ASSUMING A DUE OF 99.99%
E**
Allowable Haste
Bli* C
Compounds Potency Slope Concentration(mg/in3)
(mg/m3)-! Associated with 10"^ risk
Aery Ion it rile
Allyl Chloride
Dimethyl-Nitrosamine
N-nilroso-N-Me thy 1 urea
Manganese
Nickel
Beryllium
Cadmium
TCDU
Tr ichloretylene
8.5 x ID"2
2.66 x 10-3
4.35
670
0.40
1.8
270
1.9
121428.57
B. 80 x 10-4
1.18
3.76
2.30
1.49
2.50
5.56
3.70
5.26
8.23
1.14
x ID"4
x 10-3
x 10-6
x 10"8
x 10~5
x 10-6
x 10"8
x ID"6
x Ifl— 1 1
x 10-2
Allowable E
Stack Emission rate (g/hr)
Rate (ing/sec)
59
1880
1.15
7.45 x 10-3
12.50
2.78
1.85 x ID"2
2.63
4.12 x ID"5
5700
212.4
6768
4.14
2.68 x 10-2
45
10
6.66 x 10"2
9.47
1.48 x 10-4
20520
Input (kg/hr)
Assuming 99.99%
Efficiency
2124
67680
41.4
0.26B
450
100
0.666
94.70
1.48 x
205200
* These are preliminary estimates and arc subject to change
** Assumptions: I. Sunny summer afternoon, wind speed measured at 10 meters is 4 in/sec (stability class B).
2. Effective stack height is 150 meters.
3. Open flat country.
4. Single point source.
-------
TABLE 4 : ESTIMATION OP ALLOWABLE MASS FEED BASED ON RISK APPROACH,
ASSUMING A ORE OF 99.99% AND A RISK OF 1x10-5
E**
Allowable Waste
Compounds
Acrylonitrile
Allyl Chloride
Dime thy 1-Nitrosamine
N-nitroso-N-Methylurea
Manganese
Nickel
Beryllium
Cadmium
TCDD
Trichloretylene
Bll* C
Potency Slope Concentration(inq/m3)
(mg/m3)-l Associated with 10~5 risk
8.5 x 10-2
2.66 x ID-3
4.35
670
0.40
1.8
270
1.9
121428
8.80 x 10-4
1.18 x
3.76 x
2.30 x
1.49 x
2.50 x
5.56 x
3.70 x
5.26 x
8.23 x
1.14 x
10-4
10-3
10~6
10-8
10-5
10~6
10-B
10-6
10-11
10-2
Allowable
Stack Emission rate
Rate (9/hr)
11.3
361
0.22
1.34 x 10-3
2.4
0.53
3.6 x 10-3
0.50
7.9 x 10"6
1094
Input (kg/hr)
Assuming 99.99%
Efficiency
113
3610
2.2
1.34 x
24
5.3
3.6 x
5.0
7.9 x
10,940
10-2
10-2
10-4
1
* These are preliminary estimates and are subject to change
** Assumptions: I. Wind speed is 4 in/sec (stability class A)
2. Effective stack height is 30 meters.
J. Open flat country.
4. Single point source.
-------
feed rate at a 99.99% ORE has been dramatically reduced by a
factor of nearly 20 times. These examples illustrate the dramatic
impact of stack height on ground level concentrations of emissions.
Table 5 shows the same calculations using the same air
dispersion model but decreasing the risk level to 1 x 10~6. This
change in risk level causes both the allowable emissions rate and
the maximum feed rate at 99.99% ORE to drop by a factor of 10.
This illustrates the sensitivity of the procedure to the selection
of an acceptable risk level.
As examples of how this analytical process would impact a
real world incinerator, the restriction on the destruction of
TCDD containing waste from 2,4, 5-T production is determined as
follows:
The waste contains 300 ppm of TCDD
From Table III, the allowable feed rate at 99.99%
ORE is 7.9 x lO-4 kg/hr
7.9 x 10~4 kg/hr (TCDD) 7 300 ppm =2.63 kg/hr of waste
Thus an incinerator would be restricted to a maximum
feed rate of 2.6 kg/hr (5.810/hr) to result in a risk
of 1 x 10-5.
An incinerator burning this waste would be restricted to a
very low feed rate of the 2,4, 5-T waste. If the owner or operator
of the incinerator could demonstrate that a higher ORE could be
achieved then a higher feed rate could be allowed. In cases
such as this the permitting official would have the option of
either requiring a higher DRE, restricting the feed rate of the
waste or a combination of both.
-62-
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TABLE 5 : ESTIMATION OK ALLOWABLE MASS FEED BASED ON A RISK OF lxlO~6
ASSUMING A ORE OP 99.99%
E**
Allowable Waste
Input (kg/hr)
Compounds
Aery Ion it rile
Allyl Chloride
Dime thy 1-Nitrosamine
N-nitroso-N-Me thy 1 urea
Manganese
Nickel
Beryllium
Cadmium
TCDD
Trich lore ty lone
BH*
Potency Slope
(mg/m3)-l
8.5 x l
-------
7. Use of the Carcinogen Risk Assessment Strategy
This discussion explains how the risk assessment approach
may be used from two directions:
(a) Starting with an acceptable risk statement and working
backward to a stack emission limit (i.e., a limit on hazardous
waste feed to the incinerator).
(b) Initially stipulating emission rates and deriving expo-
sure concentrations which are related to an acceptable risk
statement.
The approach adopted for the purpose of the standard whether
manipulated in the "forward" or "backward" mode is a conservative
approach from the point of view of exposure of individuals to
hazardous materials in the ambient air. It is conservative in
the sense of once having chosen an acceptable risk limit, e.g.,
1 x 10~6, each individual is assumed to be exposed to that degree
regardless of where in the immediate area that individual might
spend most of his time. A complete dispersion model analysis of
the area surrounding a hazardous waste incinerator would clearly
result in different risk exposures depending on proximity to the
incinerator. The dispersion model calculation is related basi-
cally to a zone of maximum concentration downwind from an incine-
rator stack and the basis for the entire risk assessment analysis
is therefore, this zone of maximum exposure. Thus, the conserva-
tive nature of the approach. Each individual is assumed to be
exposed at a risk level in this example of 1 x 10~6 even though a
more detailed analysis, both nearer to and farther from the
incinerator stack could possible result in a lower exposure risk.
-64-
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As a part of the overall risk assessment, an analysis of
total population exposure could be performed. Such an analysis
would yield the probability of health damage, e.g., cancer
induction for the people in the general surrounding area, or
even the Nation as a whole based on this one source of hazardous
material. Such analyses are time consuming and difficult to
perform. The result of such analyses do not enhance the protec-
tive aspect of the risk assessment approach, since the individual
incremental risk approach is conservative.
To further understand how the override approach would affect
decisions for some typical cases, the reader is referred to Table 6
which presents results of several sample calculations. For these
examples an acceptable risk level of 1 x 10-6 (probability of
increased risk of contracting cancer for an individual during a
70 year lifetime) has been chosen to perform calculations. Other
risk levels could have been used. The approach to override or
underride the ORE of 99.99% is suggested for use only where dose-
response or threshold data are already available.
Table 6 presents four manufacturing processes representing
several wastes streams (column 1) and typical or average discharge
quantities for these wastes. From available dose-response data,
a choice of an acceptable risk level will result in associated
ambient air concentration (column 3), and from this a stack
emission rate of the chemical may be estimated (column 4). The
calculated incinerator feed rate is then derived (column 5).
-65-
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TABLE 6
SAMPLE CALCULATIONS COMPARING ALLOWABLE INCINERATOR
FEED RATES AT IxKT6 RISK WITH TYPICAL PLANT WASTE PRODUCTION RATES
(1)
Manufacturing
process
waste
I Vinyl Chloride
Monomer plant
wastes^ 19)
Electronic
components
Manufacturing
Solvents(2°)
""
Textile
Processing Wool
Scouring Sludge
(21)
f (2)
Typical or
Average Plant
Waste Compo-
nent (MT/yr.)
544-1,1,2 Tri-
chloroethane
326-Ethylene
dichloride
1.2-1,1,1,
Trichloroe thane
1.06 Perchlo-
roethylene
0.6-Manganeso
0.04-Nickel
0.0003-Arsenic
(3)
Air Concen-
tration Asso-
ciated with
lxlO~6 Incre-
mental Risk
(mg/m3)
1.13xlO-3
8.3 xlO-5
1.13x10-3
1.3xlO-4
2.5x10-6
5. 56xlO-7
3.3x10-7
(4)
Modeled
Emission
Rate (gm/hr)
108
8.0
108
12.6
0.24
0.53
0.032
(5)
Calculated
Incinerator
Feed Rate
( MT/yr . )
99.99% ORE
8510
631
8510
993
0.0019*
4.2x10-4*
2.6x10-4*
(6)
Limitations for
on-site Incinera-
tion
None
None
If 100% of metals
were emitted, on-
site incinera-
tion would be
prohibited
-------
TABLE 6 (CONT.)
SAMPLE CALCULATIONS COMPARING ALLOWABLE INCINERATOR
FEED RATES AT lxlQ-6 RISK WITH TYPICAL PLANT WASTE PRODUCTION RATES
(1)
Manufacturing
process
waste
Petroleum
Refining (Total
of 17 waste
streams( 1)
F (2)
Typical or
Average Plant
Waste Compo-
nent (MT/yr.)
0.0275-Arsenic
0.32 Nickel
(3)
Air Concen-
tration Asso-
ciated with
IxlO"6 Incre-
mental Risk
(mg/m3)
3.3x10-7
5.6x10-7
(4)
Modeled
Emission
Rate (gm/hr)
0.032
0.053
(5)
Calculated
Incinerator
Feed Rate
(MR/yr.)
99.99% ORE
2.6xlO-4*
4.2x10-4*
(6) 1
Limitations for
on-site Incinera-
tion
If 100% of metals
were emitted, the
total waste stream
could not be in-
cinerated at
lxlO~6 risk
* For these calculations it was conservatively assumed that
100% of the metal feed passed through into the emissions.
(a) Air Model Assumptions:
1. Effective Plume Height - 30 meters
2. Stability Class A
3. Wind Speed - 4 m/s
-------
The conclusions in column (6) were developed based on a
comparison of the calculated incinerator feed rate (column 5)
with the quantity of waste component in the typical waste stream
(column 2) at a destruction and removal efficiency of 99.99%.
In the case of vinyl chloride monomer production using a
1 x 10~6 incremental increase in cancer risk and 99.99% ORE of
the waste components, the 1, 1, 2 Trichlorethane waste component
would not be restrictive. Similarly, the average quantities of
solvents from electronic component manufacturing could be incin-
erated with no restrictions.
The third and fourth cases shown in Table 6 indicate signi-
ficant problems. In these examples, the metals content of the
textile sludge and the petroleum refining wastes would prohibit
incineration of the total quantity of these wastes assuming that
100% of the metals in the waste were emitted to the atmosphere.
However, if only a small amount of these metals were emitted and
most (say 99.99%) were retained either in the ash or in the
scrubber then these wastes could be incinerated on-site with no
restrictions.
The variance approach may be viewed in another way. Incin-
erators will be required to meet the 99.99% ORE for a wide
variety of wastes. It is instructive to examine the application
of the ORE to some typical wastes. Table 7 shows the results of
applying ORE = 99.99% to the same wastes for which the previous
calculations were performed to yield allowable incinerator feed
rate, starting with predetermined acceptable risk levels. In
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TABLE 7
RISK EVALUATION FOR 30,000 METRIC TON/YEAR INCINERATOR BURNING HAZARDOUS WASTE
(1)
Waste
30,000 MT/yr -
Petroleum
Re fin ing ( 1)
Vinyl Chloride
(19)
Monomer
Textile^21)
Wool Scouring
Sludge
Electronic
Components
Waste Solvents
(20)
(2)
Hazardous
Components
MT/yr .
0.48-Arsenic
.561-Nickel
1428-1,1,2
Trichloroe thane
857-ethylene
dichloride
0.038-Nickel
0.003-Arsenic
0.62-Manganese
8760-Trichloro-
ethylene
1830-Perchloro-
ethylene
(3)
Emission Rate*
g/hr
3.1 x 10-7
3.6 x 10~6
18.1
10.9
0.24
0.02
3.9
111.0
23.0
(4)
Ambient Concen-
tration from Air
Model Calculation
mg/rn-*
3.2 x ID"12
3.8 x 10-8
1.9 x ID'4
1.1 x ID"4
2.5 x 10-6
2 x 10-7
4.1 x lO-5
1.1 x lO-3
2.4 x 10~4
(5)
Incremental Risk
from Dose Response
Calculation
9.6 x ID"12
6.8 x lO"8
1.7 x ID"7
1.3 x ID"6
4.5 x 10~6
6 x 10-7
1.6 x lO-5
1 x 10-6
1.8 x ID"6
* For Organics emission rate is based on 99.99% ORE; for metals a 95% removal
rate is assumed.
-------
this case, an average incinerator capacity (off-site) was deter-
mined from a survey of 23 incinerators(23) to be 30,000 wet
Mt/yr. The assumption is made that the incinerator will operate
at full capacity over the period of one year. The quantity of
POHC discharged under these burn conditions is then modeled for
dispersion in the ambient air to the receptor. The resultant
risk level (column 5) is then calculated based on the ambient
air concentration at the receptor determined through dispersion
modeling.
Proposed Regulatory Language
§264.343 Performance Standards
(e) After consideration of the factors listed in paragraph (g)
of this Section, the Regional Administrator may, on a case-by-case
basis, establish performance standards which are either more or
less stringent than those required by paragraphs (a) and (d) of
this Section based on a finding that:
(1) More stringent standards are necessary because the
emission rates achieved by the application of the perfor-
mance standards otherwise required by this Section may
pose an unacceptable risk to human health and the environ-
ment, or
(2) Less stringent standards will achieve emission rates
which do not pose an unacceptable risk to human health and
the environment.
(g) The findings under paragraphs (e) and (f) of this Section
will be made after evaluating the following data, which the
Regional Administrator may require from the permit applicant:
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(1) Emissions of POHC's, hazardous combustion by-nroducts,
metals, and hydroqen halides, includinq:
(i) Mass emission rates from the stack, and
(iij Concentration in the qas stream exitina the stack;
(2) Air dispersion estimates for these substances,
including:
(i) Heteoroloqical data,
(ii) Descriotion of the air disoersion models,
(iii) Assumptions underlyinq the air dispersion models
used;
{3) Expected human and environmental exoosure, includinq:
(i) Topoqraohic considerations,
{ii) Population distributions,
(iii] Population activities, and
(iv) Modes, intensity and duration of exposure;
(4) Consequences of exoosure, includinq:
(i) Dose-response curves for carcinoqens,
(ii) Health effects based on human or animal studies
for other toxic constituents,
(iii) Potential for accumulation of toxic constituents
in the human body, and
(iv) Statements of exoected risk to individuals or
populations.
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C. Emission Limits on "Metals/ Hydrogen Hal ides and Elemental
Halogens
The proposed regulations included toxic metals and halogen
compounds in the destruction efficiencv reauirement. Commenters
objected on the basis that non-organic components cannot be
thermally destructed and that 99.99 percent removal in the flv
ash and bottom ash is not feasible.
The destruction and removal efficiencv approach could he
applied to metals and non-organic halogen compounds, because it
considers removal of waste constituents in the emission control
system and ash. Thus, metals and non-organic halogens emitted
could potentiallv be controlled in this wav and included in a
destruction and removal efficiency calculation. However, the
Agency elected not to apply a ORE standard to metals and non-
organic halogens in the final regulation because the Agencv does
not have test data to indicate what specific removal levels are
achievable, except in the case of hydrogen chloride emissions.
In the case of hydrogen chloride sufficient data is avail-
able to determine that air pollution control equipment can
consistently remove 99% of the HC1 contained in incinerator com-
bustion gases. This determination is reflected in the interim
final regulation in §264.343{c). This is further discussed in
the Interim Final Incinerator Background Document.
The Agency also considered whether metals and non-organic
halogens were adequately addressed through standards developed
under the Clean Air Act. The onlv existing standard applicable
to hazardous waste incinerators addresses beryllium, which is
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controlled through a National Emission Standard for Hazardous
Air Pollutants (NESHAP). A NESHAP standard for mercurv applies
to sludge incinerators but not hazardous waste incinerators.
(See the discussion under II, B - other Federal Requlations).
For metals, other than beryllium, and for non-organic halo-
gens, this proposed regulation reauires that emission limits he
set on a case-by-case basis by assessing the risk to human health
using the same criteria established for assessing a variance to
the basic DRE requirement. For metals for which EPA has deve-
loped dose response models, health effect assessments using
those models could be made. For other metals or for non-organic
halogens, emission assessments could he made using available
health effects assessment data including TLV's or MEG's. (See
IV-B - Variance to the DRE for a complete discussion of the
methodology of health effect assessments.
Proposed Regulation Language
§264.343 Performance-Standards
(f) After consideration of the factors listed in paragraph (g)
of this Section, the Regional Administrator mav, on a case-bv-
case basis, stipulate performance standards for metals, hv^rogen
halides, and elemental halogens, based on a finding that such
standards are necessary to limit the emission rates of. these
constituents to levels which do not pose an unacceptable risk to
human health and the environment.
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V. Text of the Proposed Standards
§264.342 Designation of principal organic hazardous
constituents and hazardous combustion by-products.
(a) Principal orqanic hazardous constituents (POHC's) and
hazardous combustion by-products must be treated to the extent
required by the performance standards specified in S264.343.
(b) (i) For each waste feed to be burned, one or more POHC's
and hazardous combustion by-products will be specified from
among those constituents listed in Part 261, Appendix vui of
this Chapter. This specification will be based on the deqree
difficulty of incineration of the orqanic constituents of the
waste feed and its combustion by-products, their concentration
or mass, considering the results of waste analvses and trial
burns or alternative data submitted with Part B of the facility's
permit application. Orqanic constituents or by-oroducts which
represent the greatest deqree of difficulty of incineration will
be those most likely to be designated as POHCs or hazardous
combustion by-oroducts. Constituents are more likelv to be
designated as POHCs or hazardous combustion bv-oroducts if thev
are present in large quantities or concentrations.
(ii) Trial POHC's will be desiqnated for performance of trial
burns in accordance with the procedure specified in Sl22.27(b)
for obtaining trial burn permits. Trial hazardous combustion
by-products may be desiqnated under the same Procedures.
*****
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§264.343 is amended by redesiqnattnq paraqraoh (d) as paraqranh
(h) and addinq new paraqraphs (d), (e), (f), and (q) as follows:
§264.343 Performance ^standards.
*****
(d) Incinerators burning hazardous waste must destroy hazar-
dous combustion by-products desiqnated under §264.342 so that the
total mass emission rate of these by-products emitted from the
stack is no more than .01% of the total mass feed rate of POHC's
into the incinerator.
(e) After consideration of the factors listed in oaraqraoh (q)
of this Section/ the Reqional Administrator mav, on a case-bv-case
basis, establish performance standards which are either more or
less strinqent than those required by oaraqraphs (a) and (d) of
this Section based on a findinq that:
(1) More strinqent standards are necessarv because th«?
emission rates achieved by the application of the Perfor-
mance standards otherwise required by this Section mav
pose an unacceptable risk to human health and the environ-
ment, or
(2) Less strinqent standards will achieve emission rates
which do not nose an unacceptable risk to human health
and the environment.
(f) After consideration of the factors listed in paraqraph (q)
of this Section, the Reqional Administrator mav, on a case-bv-
case basis, stipulate performance standards for metals, hvdroqen
halides, and elemental haloqens, based on a findinq that such
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standards are necessary to limit the emission rates of these
constituents to levels which do not pose an unacceptable risk
to human health and the environment.
(g) The findings under paragraphs (e) and (f) of this Section
will be made after evaluating the following data, which the
Regional Administrator mav require from the permit applicant:
(1) Emissions of POHC's, hazardous combustion bv-products,
metals, and hydrogen halides, includina:
(i) Mass emission rates from the stack, and
(ii) Concentration in the gas stream exiting the stack;
(2) Air dispersion estimates for these substances,
including:
(i) Meteorological data,
(ii) Description of the air dispersion models,
(iii) Assumptions underlying the air dispersion models
used;
(3) Expected human and environmental exposure, including:
(i) Topographic considerations,
(ii) Population distributions,
(iii) Population activities, and
(iv) Modes, intensity and duration of exposure;
(4) Consequences of exposure, including:
(1) Dose-response curves for carcinogens,
(ii) Health effects based on human or animal studies
for other toxic constituents,
(iii) Potential for accumulation of toxic constituents
in the human bodv, and
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(iv) Statements of expected risk to individuals or
populations.
(h) For purposes of permit enforcement, comoliance with the
operating requirements specified in the t>ermit (under 52fi4
will be regarded as compliance with this Section. However,
evidence that compliance with those permit conditions is insuffi-
cient to ensure compliance with the performance requirements of
this Section may be "information" justifvinq modification; revo-
cation, or reissuance of a permit under 5122.15 of this Chapter.
*****
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References
1. Assessment of Hazardous Waste Practices in the Petroleum
Refining Industry, NTIS No. PB-259-097.
2. Ferguson, T. L.; Bergman, F. J.; Cooper, G. R.; Li, R. T. ;
and Homea, F. I.; Determination of Incinerator Operating
Conditions Necessary for Safe Disposal of Pesticides. EPA
600/2-75-041, NTIS No. PB 251-131/AS.
3. Polychlorinated Biphenyls, Criteria Modifications,
40 CFR 761.40 Incineration, May 31, 1979.
4. Wisconsin "Administrative Rules for Air Pollution Control"
Act 250 of 1965 as amended and Act 348 of 1965 as amended.
5. Lustenhouwer, J.W.A.; K Olie; and O. Hatrzinger; Chlori-
nated Dibenzo-p-dioxins and Related Compounds in Incinerator
Effluents, In Press Chemosphere.
6. U.S. Environmental Protection Agency, National Emission
Standards for Identifying, Assessing and Relating Airborne
Substances Posing Risk of Cancer, Federal Register
Wednesday, October 10, 1979.
7. Interim Procedures and Guidelines for Health Risk and
Economic Impact Assessments of Suspected Carcinogens;
U.S. EPA, Federal Register, Vol. 41, p. 21402, May 25, 1978.
8. Scientific Basis for Identification of Potential Cacinogens
and Estimation of Risk; Interagency Regulatory Liaison
Group (IRLG), Federal Register, Vol. 44, No. 131, Friday,
July 6, 1979.
9. Designation of 1822 Hazardous Substances, U.S. EPA,
Federal Register, Vol. 45, No. 133, Wednesday July 9, 1980
p. 46094.
10. Water Quality Criteria Documents Summaries, U.S. EPA,
Federal Register, Vol. 45, No. 231 November 28, 1980.
11. TLVs Threshold Limit Values for Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1980, Adopted by American Conference of
Governmental Industrial Hygienists.
12. U.S. EPA, OAQPS Guidelines Series, Guidelines on Air
Quality Models, OAQPS 1.2-080 April 1978.
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13. Cincinnati Gas and Eletric Company, U.S. EPA, 578,
p. 2d 660, 6th Circuit, 1978.
14. Cleveland Electric Illuminating Company, U.S. EPA 572
2d 1150, 6th Circuit 1978, cert, denied, 436 U.S. 911
c 1978.
15. Budney L. J., Guidelines for Air Quality Maintenance and
Planning and Analysis, Volume 10 (Revised); Procedures
for Evaluating Air Quality Impact of New Stationary Sources,
EPA 450/4-77-001, October 1977.
16. User's Manual for a Single Source (CRSTER) Model, EPA
#450/2-77-013, July 1977.
17. Busse, A.D. and J.R. Zimmerman, User's Guide for the
Climotological Dispersion Model, EPA # RA-73-024,
December 1975.
18. Regional Workshops and Air Quality Modeling: A Summary
Report (Draft).
19. Identification of Potential Carcinogens and Estimates of
Risk; Report of the Interagency Regulatory Liaison Group,
Work Group on Risk Assessment, Journal of the National
Cancer Institute, Volume 63, No. 1 July, 1979.
20. Assessment of Industrial Hazardous Waste Practices; Organic
Chemicals, Pesticides, and Explosive Industries NTIS
No. PB 251-307, 1976.
21. Assessment of Industrial Hazardous Waste Practices -
Electronic Components Manufacturing Industly. NTIS
No. PB-265-532, 1977.
22. Assessment of Industrial Hazardous Waste Practices Textiles
Industry. NTIS No. PB-258-953.
23. Off-Site Hazardous Waste Management Capacity, Booz - Allen
and Hamilton Inc., Bethesda Md., August 4, 1980 (Draft
Report).
24. Duvall, D.S.; University of Dayton, Letter on Research
Results Utilizing the TDAS; to R.A. Carnes, U.S. EPA,
October 17, 1979 (Draft).
25. Multimedia Environmental Goals for Environmental Assessment;
Vol. I, II, III, and IV, U.S. EPA, 1978 and 1979, EPA-600/
-7-77-136 A and B, EPA-600/-7-79-176 A and B respectively
and Volume 1 Supplement, EPA 600/-7-80-041.
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these chemicals are potentially human carcinogens. (Chemicals
regulated as carcinogens by the Occupational Safety and Health
Administration (OSHA) and the Consumer Product Safety Commission
(CPSC) are also on this list but are not noted as such since
they have been evaluated as being carcinogens by one of the
other organizations previously mentioned). CAG evaluated the
studies upon which IARC, NTP, or FDA relied and agreed with all
the NTP and FDA evaluations that the chemicals presented a
potential human cancer risk. The CAG agreed with most of lARC's
evaluations. There are inconsistencies between the CAG and IARC
evaluations for a few chemicals because the CAG considered infor-
mation not available to or not otherwise used by IARC, and
because there are differences in the criteria used in making the
qualitative evaluations.
The list is not a comprehensive listing of all chemicals
having substantial or strong evidence of carcinogenicity, chemi-
cals which do not now appear on the list will be added. A
continuing review of evaluations by organizations such IARC, NTP,
FDA, OSHA, and CPSC may result in periodic revisions to the
present list.
The CAG evaluates substances for possible carcinogenicity
according to the procedures outlined in the Agency's Interim
Guidelines for Carcinogen Risk Assessment found in Interim Proce-
dures and Guidelines for Health Risk and Economic Impact Assess-
ments of Suspected Carcinogens (41 Fed. Reg. 21402, May 25, 1976),
These guidelines are consistent with the Interagency Regulatory
-------
Liaison Group's Scientific Bases for Identification of Potential
Carcinogens and Estimation of Risks (Jouirnal of the National
Cancer Institute (>3_ (1): 243-268 1979, 44 Fed. Reg. 39858, July 5,
1979), and the Regulatory Council Statement on Regulation of
Chemical Carcinogens (44 Fed. Reg. 760037, October 17, 1979).
Evidence concerning the carcinogenicity of chemical
substances is of three types: (1) epidemiologic evidence derived
from long-term bioassays on animals; and (3) supportive or
suggestive evidence derived from studies of chemical-structure
or from short-term mutagenicity, cell transformation or other
tests that are believed to correlate with carcinogenic activity.
The CAG evaluates all available evidence on the carcinogeni-
city of a chemical before reaching a conclusion based on the
"weight of the evidence," about the chemical's human carcinogenic
potential. Conclusions about the overall weight of evidence
involve a consideration of the quality and adequacy of the data
and the kinds of responses induced by the suspect carcinogen.
The best evidence that an agent is a human carcinogen comes from
epidemiologic studies in conjunction with confirmatory animal
tests. Substantial evidence is provided by animal tests that
demonstrate the induction of malignant tumors in one or more
species or of benign tumors that are generally recognized as
early stages of malignancies. Suggestive evidence includes indi-
rect tests of tumorigenic activity, such as mutagenicity, in
vitro cell transformation, and initation-promotion skin tests in
mice. Ancillary data that bear on judgments about carcinogenic
-------
potential, e.g., evidence from systematic studies that relate
chemical structure to carcinogenicity, are alos considered.
Substances were placed on the CAG list only if they had
been demonstrated to induce malignant tumors in one or more ani-
mal species or to induce benign tumors that are generally recog-
nized as early stages of malignancies, and/or if positive epide-
miologic studies indicated they were carcinogenic. Although the
CAG has determined that there is substantial evidence of carcino-
genicity for each chemical substance on the list, the data varies
to some extent with respect to the scope and quality of the
studies.
No uncommonly, CAG reports are updated because new evidence
becomes available. Because of this, it is important that the
most recent CAG evaluation be consulted.
Some of the reports prepared by CAG are subject ot confiden-
tiality claims. Because of these claims (primarily under the
Federal Insecticide, Fungicide, and Rodenticide Act) some reports
may not be released. Therefore, all requests for CAG reports and
related documentation must be submitted through EPA's Freedom of
Information Office (A-101), Washington, D.C. 20460, and should
be marked CAG/LOC.
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Benzo(b)fluoranthene (IARC)
Benzo(j)fluoranthene (IARC)@
Beryllium and Beryllium Compounds (CAG/ IARC)
N,N-Bis(2-Chloroethyl)-2-Napthylamine (Chlornaphazine) (IARC)**
Cadmium and Cadmium Compounds (CAG/ IARC)
Carbon Tetrachloride (CAG, IARC)
Chlorambucil (IARC)**
Chloroalkyl Ethers
Bis(2-chloroethyl)ether (BCEE) (CAG) (IARC)@
Bis(chloromethyl)ether (BCME) (CAG/ IARC)
Chloromethyl methyl ether (CMME), technical grade (IARC)
Chlordane (CAG, NCI)
Chlorinated Ethanes
1,2-Dichloroethane [Ethylene Chloride, Ethylene Dichloride (EDC)]
(CAG, IARC, NCI)
Hexachloroethane (CAG)
1,1,2,2-Tetrachloroethane (CAG)
1,1,2-Trichloroethane (CAG, NCI, IARC)@
Chlorobenzilate (CAG)
Chloroform (CAG, IARC)
Chromium Compounds, Hexavalent (CAG, IARC)
Chrysene (IARC)@
Citrus Red No. 2 (IARC)
Coal Tar and Soot (CAG, included in lARC's soots, tars, and oils
designation)
Coke Oven Emissions [Polycyclic Organic Matter (POM)] (CAG)
Creosote (CAG)
Cycasin (IARC)
** Used as a drug.
'? Evaluated by IARC as not having sufficient evidence of
carcinogenicity.
-------
CHEMICALS HAVING SUBSTANTIAL EVIDENCE
OF CARCINOGENICITY3
2-Acetylaminoflourene (See references)
Acrylonitrile (CAG, IARC)
Aflatoxins (IARC)*
Aldrin (CAG, NCI)
4-Aminobiphenyl (IARC)
Amitrole (IARC)
Aramite (IARC)
Arsenic and Arsenic Compounds (CAG, IARC)
Asbestos (CAG, IARC)
Auramine and the manufacture of Auramine (IARC)
Azaserine (IARC)**
Benz(c)acridine (IARC)@
Benz(a)anthracene (IARC)
Benzene (CAG, IARC)
Benzidine (CAG, IARC)
Benzo(a)pyrene (IARC)
a This is not a comprehensive list of all chemicals having
substantial evidence of carcinogenicity. Other chemicals will be
added. No attempt has been made to select chemicals based upon
appropriateness for regulation by EPA. The list is intended to
be a basis for selection by the various program offices according
to their specific needs.
* Fungal toxin, not an industrially manufactured product.
** Used as a drug.
@ Evaluated by IARC as not having sufficient evidence of
carcinogenicity.
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CHEMICALS HAVING EVIDENCE OF CARCINOGENICITY
In response to requests from several EPA offices, the
Carcinogen Assessment Group (CAG), Office of Health and Environ-
mental Assessment in EPA's Research and Development Office has
prepared a list of chemical substances for which substantial or
strong evidence exists showing that exposure to these chemicals/
under certain conditions, causes cancer in human,s or can cause
cancer in animal species which in turn, makes them potentially
carcinogenic in humans.
The list was initially prepared in response to the needs of
the OFfice of Pesticides and Toxic Substances (OPTS) to develop
labeling regulations under section 6 of TSCA and the Office of
Solid Waste (OSW) to develop hazardous waste regulations under
section 3001 of RCRA. It is anticipated that it will serve
other purposes within th Agency according to the needs of the
program offices.
The sources of information used in selecting agents as
candidates for the list are of two types: chemicals which the
Carcinogen Assessment Group previously has evaluated and has
determined pose a potential human cancer risk; and chemicals,
the carcinogenicity of which the CAG reviewed because one or more
of three organizations — the International Agency for Research
on Cancer (IARC), the National Cancer Institute Bioassay Program
which has been reorganized into the National Toxicology Program
(NTP), and the Food and Drug Administration (FDA) of the U.S.
Department of Health and Human Services — had concluded that
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Cyclophosphamide (IARC)**
Daunomycin (IARC)**
DDT (Dichlorodiphenyltrichloroethane) (CAG)
Diallate (CAG) (IARC)@
Dibenz(a,h)acridine (IARC)
Dibenz(a,j)acridine (IARC)
Dibenz(a,h)anthracene (IARC)
Dibenzo(a,e)pyrene (IARC)
Dibenzo(a,h)pyrene (IARC)
Dibenzo(a, j)pyrene (IARC)
1,2-Dibromo-3-chloropropane (DBCP) (CAG, IARC, NCI)
1,2-Dibromoethane [Ethylene Bromide, Ethylene Dibromide (EDB)]
(NCI, CAG, IARC)
3,3'-Dichlorobenzidine (DCB) (CAG, IARC)
Dieldrin (CAG)
Diepoxybutane (IARC)
1,2-Diethylhydrazine (IARC)
Diethylstilbestrol (DBS) (IARC)**
Dihydrosafrole (IARC)
3,3'-Dimethoxybenzidine (o-Dianisidine) (IARC)
p-Dimethylarainoazobenzene (IARC)
7,12-Dimethylbenz(a)anthracene (See references)
3,31-Dimethylbenzidine (o-Tolidine) (IARC)
Dimethylcarbamoyl Chloride (IARC)
** Used as a drug.
@ Evaluated by IARC as not having sufficient evidence of
carcinogenicity.
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1,1-Dimethylhydrzine (IARC)
1,2-Dimethylhydrazine (IARC)
Dimethyl Sulfate (IARC)
2,4-Dinitrotoluene (CAG, NCI)
1,4-Dioxane (NCI)
1,2-Diphenylhydrazine (CAG)
Epichlorohydrin (CAG)
Ethylene Bis Ditiocarbaraate (EBDC) (CAG)
Ethyleneimine (Aziridine) (IARC)@
Ethylene Oxide (CAG, IARC)
Ethylenethiourea (CAG, IARC)
Ethyl Methanesulfonate (IARC)
Formaldehyde (CAG)
Glycidaldehyde (IARC)
Heptachlor (CAG, NCI)
Hexachlorobenzene (CAG, IARC)
Hexachlorobutadiene (CAG)
Hexachlorocyclohexane (HCH)
HCH (CAG)
HCH (CAG)
HCH (Lindane) (CAG)
Technical HCH (CAG)
Hydrazine (IARC)
Indeno(l,2,3-cd)pyrene (IARC)
Iron Dextran (IARC)**@
** Used as a drug.
@ Evaluated by IARC as not having sufficient evidence of
carcinogenici ty.
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Isosafrole (IARC)
Kepone (Chlordecone) (CAG, NCI)
Lasiocarpine (IARC, NCI)
Melphalan (IARC)**
Methapyrilene (FDA)**
3-Methylchoanthrene (See references)
4,4'-Methylenebis(2-Chloroaniline) (MOCA) (IARC)
Methyl Iodide (CAG, IARC)
Methyl Methanesulfonate (IARC)
N-Methyl-N1-nitro-N-nitrosoguanidine (IARC)
Methylthiouracil (IARC)**
Mustard Gas (IARC)
1-Naphthylamine, technical grade (CAG)
2-Naphthylamine (IARC)
Nickel and Nickel Compounds (CAG, IARC)
Nitrogen Mustard and its hydrochloride (IARC)
Nitrogen Mustard N-oxide and its hydrochloride (IARC)
5-Nitro-o-toluidine (NCI)
4-Nitroquinoline-l-oxide (See references)
Nitrosamines
N-Nitrosodiethanolamine (IARC)
N-Nitrosodiethylamine (DENA) (CAG, IARC)
N-Nitrosodimethylamine (DMNA) (CAG, IARC)
N-Nitrosodi-n-butylamine (IARC)
N-Nitrosomethylethylamine (IARC)
N-Nitrosodi-n-propylamine (IARC)
N-Nitrosomethylethylamine (IARC)
N-Nitrosomethylvinylamine (IARC)
** Used as a drug.
@ Evaluated by IARC as not having sufficient evidence of
carcinogenicity.
-------
N-Nitroso-N-Ethylurea (NEU) (CAG, IARC)
N-Nitroso-N-Methylurea (NMU) (CAG, IARC)
N-Nitroso-N-methylurethane (IARC)
N-Nitrosomorpholine (IARC)
N-Nitrosonornicotine (IARC)
N-Nitrosopiperidine (IARC)
N-Nitrosopyrrolidine (IARC)
N-Nitrososarcosine (IARC)
Pentachloronitrobenzene (PCNB) (CAG)
Phenacetin (IARC)**
Polychlorinated Biphynyls (PCBs) (CAG, IARC)
Pronamide (CAG)
1,3-Propane Sultone (IARC)
3-Propiolactone (IARC)
Propylthiouracil (IARC)**
Reserpine (NCI)**
Saccharin (FDA)***
Safrole (CAG, IARC)***
Selenium Sulfide (NCI)
Streptozotocin (IARC)**
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) (CAG)
Tetrachloroethylene (Perchloroethylene) (CAG, NCI)
Thioacetamide (IARC)
Thiourea (IARC)
o-Toluidine Hydrochloride (NCI)
Toxaphene (CAG, IARC, NCI)
Trichloroethylene (CAG, NCI)
** Used as a drug.
*** Used as a food.
-------
2,4,5-Trichlorophenol (NCI)
Tris(l-aziridinyl)phosphine sulfide (thio-TEPA) (IARC, NCI)**
Tris(2,3-dibromopropyl)phosphate (IARC, NCI)
Trypan Blue, commercial grade (IARC)
Uracil Mustard (IARC)**
Urethane (IARC) (Ethyl carbamate; ethyl ester of carbamic acid)
Vinyl Chloride (CAG, IARC)
Vinylidene Chloride (CAG)
** Used as a drug.
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