HAZARDOUS ORGANIC NESHAP (HON)

RESIDUAL RISK AND REVIEW OF

TECHNOLOGY STANDARD RULEMAKING

 SUMMARY OF 	PUBLIC COMMENTS AND RESPONSES

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Emission Standards Division

Research Triangle Park, North Carolina   27711

December 14, 2006

TABLE OF CONTENTS

Section	Page

1.0	INTRODUCTION	1

2.0	LIST OF PUBLIC COMMENTERS	2

	2.1	List of Acronyms and Abbreviations	6

3.0	OPTION SELECTION AND BASIS OF DECISION	7

	3.1	Option Selection	7

	3.2	Basis of Decision	11

4.0	SECTION 112 (d)(6) OF THE CLEAN AIR ACT	17

5.0	CONTROL OPTIONS	19

	5.1	General Comments	19

	5.2	Equipment Leaks	22

	5.3	Process Vents	28

	5.4	Transfer Operations	30

	5.5	Wastewater	32

6.0	RISK ANALYSIS	34

	6.1	Risk Factors	34

	6.2	Risk Assessment	39

7.0	STATUTORY REQUIREMENTS	61

8.0	CLARIFICATIONS AND MINOR CHANGES TO RULE	63

9.0	OTHER	73

	9.1	Applicability	73

	9.2	Compliance	74

	9.3	Low Risk Alternative	77

	1.0  INTRODUCTION

On June 14, 2006, EPA proposed amendments to the National Emission
Standards for Hazardous Air Pollutants from the Synthetic Organic
Chemical Manufacturing Industry (SOCMI).  This document contains
summaries of the public comments that EPA received on the proposed
amendments.  In this document, EPA responds to the public comments.  The
public comments and EPA responses documents the basis for revisions made
between the proposal on June 14, 2006, and the subsequent final
amendments.

2.0  LIST OF COMMENTERS

The EPA received 35 comment letters on the proposed amendments to the
National Emission Standards for Hazardous Air Pollutants (NESHAP) from
the Synthetic Organic Chemical Manufacturing Industry (SOCMI) before the
comment period closed on August 14, 2006.  Comments are contained in
Docket EPA-HQ-OAR-2005-0475.  The commenter, affiliation, and item
number in Docket EPA-HQ-OAR-2005-0475 is listed in Tables 1.  A list of
acronyms and units of measure used in this document appears after the
list of commenters.

	TABLE 1.  PUBLIC COMMENTS RECEIVED BY AUGUST 14, 2006

FOR THE HAZARDOUS ORGANIC NESHAP (HON) RESIDUAL

RISK AND REVIEW OF TECHNOLOGY STANDARD RULEMAKING

DOCKET EPA EPA-HQ-OAR-2005-0475

Item Number

Commenter and Affiliation

EPA-HQ-OAR-2005-0475-0115	B. Sachau

15 Elm Street

Florham Park NJ  07932

EPA-HQ-OAR-2005-0475-0120	Vinson Hellwig, Chair, STAPPA Air Toxics
Committee and Robert Colby, Chair, ALAPCO Air Toxics Committee

EPA-HQ-OAR-2005-0475-0120.1	Vinson Hellwig, Chair, STAPPA Air Toxics
Committee and Robert Colby, Chair, ALAPCO Air Toxics Committee

EPA-HQ-OAR-2005-0475-0121	William O'Sullivan, Director Division of Air
Quality, State of New Jersey, Department of Environmental Protection

EPA-HQ-OAR-2005-0475-0122	James L. McGraw, Managing Director & CEO,
International Institute of Synthetic Rubber Producers (IISRP)

EPA-HQ-OAR-2005-0475-0122.1	James L. McGraw, Managing Director & CEO,
International Institute of Synthetic Rubber Producers (IISRP)

EPA-HQ-OAR-2005-0475-0123	Arturo Blanco, Chief, Bureau of Air Quality
Control, City of Houston, Department of Health and Human Services

EPA-HQ-OAR-2005-0475-0123.1	Arturo Blanco, Chief, Bureau of Air Quality
Control, City of Houston, Department of Health and Human Services

EPA-HQ-OAR-2005-0475-0124	Hasmukh Shah, Ph.D., Acting Vice President

CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0124.1	Hasmukh Shah, Ph.D., Acting Vice President

CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0124.2	Hasmukh Shah, Ph.D., Acting Vice President

CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0124.3	Hasmukh Shah, Ph.D., Acting Vice President

CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0124.4	Hasmukh Shah, Ph.D., Acting Vice President

CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0125	Charles L. Elkins, Residual Risk Coalition

EPA-HQ-OAR-2005-0475-0125.1	Charles L. Elkins, Residual Risk Coalition

EPA-HQ-OAR-2005-0475-0126	Rich Raiders, Arkema Inc.

EPA-HQ-OAR-2005-0475-0126.1	Rich Raiders, Arkema Inc.

EPA-HQ-OAR-2005-0475-0127	Anonymous public comment

EPA-HQ-OAR-2005-0475-0128	Arturo Blanco, Chief, Bureau of Air Quality
Control, City of Houston

EPA-HQ-OAR-2005-0475-0128.1	Arturo Blanco, Chief, Bureau of Air Quality
Control, City of Houston

EPA-HQ-OAR-2005-0475-0128.2	Arturo Blanco, Chief, Bureau of Air Quality
Control, City of Houston

EPA-HQ-OAR-2005-0475-0129	C. Gordon, API

EPA-HQ-OAR-2005-0475-0130	Jeff Gunnulfsen, Manager, Government
Relations, Synthetic Organic Chemicals Manufacturers Association (SOCMA)

EPA-HQ-OAR-2005-0475-0130.1	Jeff Gunnulfsen, Manager, Government
Relations, Synthetic Organic Chemicals Manufacturers Association (SOCMA)

EPA-HQ-OAR-2005-0475-0131	Robert J. Morehouse, Downstream and Chemical
SH&E, ExxonMobil Refining and Supply Company

EPA-HQ-OAR-2005-0475-0131.1	Robert J. Morehouse, Downstream and Chemical
SH&E, ExxonMobil Refining and Supply Company

EPA-HQ-OAR-2005-0475-0132	Robert Hahn and Caroline Cecot, AEI

Brookings Joint Center for Regulatory Studies

EPA-HQ-OAR-2005-0475-0132.1	Robert Hahn and Caroline Cecot, AEI

Brookings Joint Center for Regulatory Studies

EPA-HQ-OAR-2005-0475-0133	Meg Healy, Acting Executive Director,
Galveston Houston Association for Smog Prevention (GHASP)

EPA-HQ-OAR-2005-0475-0133.1	Meg Healy, Acting Executive Director,
Galveston Houston Association for Smog Prevention (GHASP)

EPA-HQ-OAR-2005-0475-0134	Comments submitted by Valerie Ughetta,
Director of Stationary Sources, Alliance of Automobile Manufacturers

EPA-HQ-OAR-2005-0475-0134.1	Comments submitted by Valerie Ughetta,
Director of Stationary Sources, Alliance of Automobile Manufacturers

EPA-HQ-OAR-2005-0475-0135	Elizabeth McMeekin, Environmental Affairs, Air
Programs, PPG Industries, Inc.

EPA-HQ-OAR-2005-0475-0135.1	Elizabeth McMeekin, Environmental Affairs,
Air Programs, PPG Industries, Inc.

EPA-HQ-OAR-2005-0475-0136	Patrice Simms and John Walke, National
Resources Defense Council and Paul Cort, Earthjustice

EPA-HQ-OAR-2005-0475-0136.1	Patrice Simms and John Walke, National
Resources Defense Council and Paul Cort, Earthjustice

EPA-HQ-OAR-2005-0475-0137	Norbert Dee, Ph.D., Director, Environment,
National Petrochemicals and Refiners Association (NPRA)

EPA-HQ-OAR-2005-0475-0137.1	Norbert Dee, Ph.D., Director, Environment,
National Petrochemicals and Refiners Association (NPRA)

EPA-HQ-OAR-2005-0475-0138	Leslie A. Hulse, Assistant General Counsel,
American Chemistry Council (ACC)

EPA-HQ-OAR-2005-0475-0138.1	Leslie A. Hulse, Assistant General Counsel,
American Chemistry Council (ACC)

EPA-HQ-OAR-2005-0475-0139	G. Vinson Hellwig, Chief, Air Quality
Division, Michigan Department of Environmental Quality (MDEQ)

EPA-HQ-OAR-2005-0475-0139.1	G. Vinson Hellwig, Chief, Air Quality
Division, Michigan Department of Environmental Quality (MDEQ)

EPA-HQ-OAR-2005-0475-0140	Bruce J. Alexius, EH&S Regulatory Affairs
Expertise Center, The Dow Chemical Company

EPA-HQ-OAR-2005-0475-0141	John A. Dege, Air Competency Leader, E. I. du
Pont de Nemours, Inc.

EPA-HQ-OAR-2005-0475-0142	Stephen V. Capone, Air Program Leader, GE
Plastics

EPA-HQ-OAR-2005-0475-0143	Ali Mirzakhalili, Administrator, State of
Delaware, Department of Natural Resources & Environmental Control Air
Quality Management Section

EPA-HQ-OAR-2005-0475-0144	Barry Christensen, Manager, Air Quality,
Occidental Chemical Corporation (OxyChem) (OCC)

EPA-HQ-OAR-2005-0475-0145	Arthur N. Marin, Executive Director, Northeast
States for Coordinated Air Use Management (NESCAUM)

EPA-HQ-OAR-2005-0475-0146	Robert J. Fensterheim, Executive Director, The
Acrylonitrile Group, Inc. (AN Group)

EPA-HQ-OAR-2005-0475-0146.1	Robert J. Fensterheim, Executive Director,
The Acrylonitrile Group, Inc. (AN Group)

EPA-HQ-OAR-2005-0475-0146.2	Robert J. Fensterheim, Executive Director,
The Acrylonitrile Group, Inc. (AN Group)

EPA-HQ-OAR-2005-0475-0147	Eastman Chemical Company

EPA-HQ-OAR-2005-0475-0147.1	Eastman Chemical Company

EPA-HQ-OAR-2005-0475-0148	B.Z. Karachiwala, Director, Environmental
Public Health Division, Harris County Public Health & Environmental
Services (HCPHES)

EPA-HQ-OAR-2005-0475-0149	Hasmukh Shah, Ph.D., Acting Vice President,
CHEMSTAR, American Chemistry Council Ketones Panel

EPA-HQ-OAR-2005-0475-0150	Frank E. Borrelli, Technical Director, The
Vinyl Institute (VI)

EPA-HQ-OAR-2005-0475-0150.1	Frank E. Borrelli, Technical Director, The
Vinyl Institute (VI)

EPA-HQ-OAR-2005-0475-0151	Jean Cyril Walker, Keller and Heckman LLP on
behalf of Frank Borrelli, Technical Director, The Vinyl Institute, Inc.
(VI)

EPA-HQ-OAR-2005-0475-0151.1	Jean Cyril Walker, Keller and Heckman LLP on
behalf of Frank Borrelli, Technical Director, The Vinyl Institute, Inc.
(VI)

EPA-HQ-OAR-2005-0475-0152	Hasmukh Shah, Ph.D., Acting Vice President,
CHEMSTAR, American Chemistry Council

EPA-HQ-OAR-2005-0475-0153	Elaine Chang, DrPH., Deputy Executive Officer,
Planning, Rule Development and Area Sources, South Coast Air Quality
Management District (SCAQMD)

2.1	List Of Acronyms And Abbreviations

Acronyms

ACC

American Chemistry Council

AN	Acrylonitrile

ATSDR	Agency for Toxic Substances and Disease Registry

CAA 	Clean Air Act

CMPUs	SOCMI chemical manufacturing process units

EPA	U. S. Environmental Protection Agency

FR	Federal Register

GACT	generally available control technology

HAP	hazardous air pollutants

HI	Hazard Index

HON	hazardous organic NESHAP

HQ 	hazard quotient

IDLH/10	imminently dangerous to life and health

IRIS	Integrated Risk Information System

LDAR	detection and repair

MACT	maximum achievable control technology

MON	Miscellaneous organic NESHAP

NEI	National Emissions Inventory

NESHAP	national emission standards for hazardous air pollutants

NSR	new source review

NTP	National Toxicology Program

OLD	Organic Liquid Distribution

ppmv	parts per million by volume

RCRA	Resource Conservation and Recovery Act

RFC	reference concentration

SIC	Standard Industrial Classification

SOCMI	Synthetic Organic Chemical Manufacturing Industry

SSMP 	startup, shutdown, and malfunction plan

TERA	Toxicology Excellence for Risk Assessment

VOC	volatile organic compounds

3.0  OPTION SELECTION AND BASIS OF DECISION

3.1	Option Selection

Comment:  One commenter (0136) claimed that the cost effectiveness
cutoffs used by EPA to make the decision are not properly explained and
are ridiculously low.  The commenter (0136) stated these arbitrary
cost-effectiveness cutoffs are lower than the costs often imposed under
CAA section 112(d), including beyond-the-floor standards that EPA has
previously identified as reasonable.  The commenter (0136) added they
are also lower than costs imposed on sources of criteria pollutants
under the NSR program where all emissions are offset and there is no
similar finding that public health is not being adequately protected.
EPA’s own economic analysis shows that the economic impact of Option 2
would change price and output by only two hundredths of one percent or
less.

Response:  At proposal we estimated costs to be $13 million per year for
Option 2.  Based on public comments, we revised the cost estimate for
Option 2 to be $6 million per year.  Even at the $6 million per year
cost, we consider the cost of Option 2 to be unreasonable given the
level of cancer incidence reduction achieved.  Baseline cancer incidence
under the current HON rule is estimated at 0.14 cases per year.  Option
2 would reduce incidence by about 0.05 cases per year.  Statistically,
this level of risk reduction means that Option 2 would prevent one
cancer case every 20 years.  In addition, the changes in the
distribution of risks do not warrant the additional costs.  The maximum
individual cancer risk under Option 2 would be reduced from 100-in-1
million to 60-in-1 million.  The cancer risks for 450,000 people would
be shifted to levels below 1-in-1 million, and the HI would be reduced
from above to below 1 for 20 people.  We conclude that this degree of
additional public health protection, based on the specific facts of this
rulemaking, is not warranted in light of the costs to industry of
compliance with proposed Option 2.  Consequently, we have determined
that it is not reasonable to impose any additional controls to provide
an ample margin of safety to protect public health.  While Option 2
would significantly reduce the total number of people exposed to
lifetime cancer risks above 1-in-1 million, we judged that, for this
industry, additional control is not warranted given the low level of
cancer incidence reduction achieved by proposed Option 2.

Comment:  One commenter (0146) believed that if EPA were to use updated
health evaluations as well as more realistic exposure assumptions, the
Agency would find that there are very few, if any, places in the country
where the cancer risk is greater than one in a million (1×10-6).  The
commenter (0146) contended that a revised assessment should readily
allow the Agency to conclude that the existing MACT standard for the
entire HON source category is already protective of public health with
an ample margin of safety and, as such, no further controls are
justified under sections 112(f) or 112(d)(6) of the Clean Air Act.

Response:  The commenter provided no data or analyses that would
demonstrate its assertion that very few, if any, places in the country
would have cancer risks from HON facilities greater than 1-in-1 million.
 EPA has, based on its assessment of the source category, concluded that
the level of risk from this source category is acceptable, and that the
current standards provide an ample margin of safety to protect public
health and prevent adverse environmental effects.

Comment:  Several commenters (0125, 0129, 0130, 0135, 0138) contended
that option 2 is a collection of three independent proposals and the
Agency should not link them to determine if they are justified under
either CAA section 112(f) or section 112(d)(6).  Two commenters (0125,
0130) urged the Agency to return to using properly arrayed incremental
cost/benefit comparisons to avoid the potential blurring or aggregating
of the costs and benefits of the individual choices.  Three commenters
(0129, 0130, 0135) argued that, for the controls examined on three
emissions source types in proposed Option 2, the controls suggested for
each of these emission sources are technologically and functionally
independent of the other two.  Two commenters (0129, 0138) stated that
there is nothing about the three components of Option 2 that makes it
necessary to treat them as one, stating that they address three separate
types of emissions, amend different paragraphs in subparts G and H, and,
as indicated in Tables 2 and 3 of the proposal, have different costs and
different calculated benefits.  Two commenters (0125, 0130) stated the
public, as well, is denied an easy way to analyze or challenge this
grouping, and thus the Agency is denied the benefit of the public’s
insights into what would constitute the best course of action.

Response:  In the proposal, we separately evaluated the costs, emission
reductions, and risk reductions of each of the three regulatory
alternatives that comprise option 2.  These results were presented for
public comment in the preamble.  We combined the three regulatory
alternatives into a single option that represents the maximum emission
reduction that we believe is technically achievable to focus public
comments on how this option would satisfy the requirement to protect
public health with an ample margin of safety.  However, we solicited
comments on all aspects of the proposed rulemaking.  No one was
prohibited from submitting comments on other combinations of regulatory
alternatives that would satisfy this requirement.

Comment:  Several commenters (0120, 0121, 0123, 0128, 0133, 0139, 0143,
0148, 0153) supported additional controls on HON sources, thereby
supporting Option 2 and rejecting Option 1.  The commenters (0120, 0123,
0128, 0133, 0153) opposed option 1 because it did not protect public
health and is inconsistent with the Act.  The commenter (0120, 0121,
0123, 0128, 0139) supported requiring controls that would reduce the
lifetime cancer risk below 1 in 1 million. One commenter (0136)
contended that even under the Benzene NESHAP framework, EPA’s
determination of acceptable risk inappropriately fails to protect public
health. One commenter (0136) stated that neither option 1or option 2
provides sufficient protection of public health.  The commenter claimed
that EPA in the preamble downplays even the 100-in-1 million upper limit
as a mere ‘benchmark’ which does not constitute a rigid line [71
Fed. Reg. at 34,432]. The commenter (0136) believes that a maximum
individual risk of 100 in a million should not be considered to be
acceptable and that EPA has not sufficiently and clearly justified a
deviation from this ordinary upper bound. Additionally, the number of
people exposed to HAPs from SOCMI is very high. Even by EPA’s
estimates, millions of people are exposed to hazardous air pollutants at
levels above 1 in a million and thousands are exposed at levels an order
of magnitude higher than that.  The commenter (0136) believes that these
risk levels are unacceptable and that neither Option 1 or 2 provide an
amply margin of safety, particularly considering given the dubious
emission data, inherent modeling uncertainty, mid-revision toxicological
assessments, and other limitations in the Risk Assessment.

Other commenters (0122, 0124, 0125, 0127, 0129, 0130, 0131, 0134, 0135,
0137, 0138, 0140, 142, 0144, 0147, 0151) opposed option 2 because option
1 provides sufficient protection of public health and option 2 provides
limited benefits with high costs.  Two commenters (0134, 0138) contended
that EPA need not reduce all estimated individual cancer risks to less
than 1-in-1 million to find risks are within an ample margin of safety
and argued that EPA’s stated rationale for option 2 does not support
adopting increased controls to meet the ample margin of safety
requirement.  One commenter (0138) provided examples that show a low
cancer risk resulting from HON sources.  One commenter (0135, 0138,
0142, 0144) added that AMOS is provided with current controls and the
reductions for option 2 are overstated.  One commenter (0138) believed
that the overall inherent conservatism built into EPA’s risk analyses,
particularly for equipment leak emissions and health benchmark values
for two of the highest risk HAPs, 1,3 -butadiene and ethylene oxide,
results in overestimation of risk.  Given this conservatism, the
commenter contended that the health benefit of option 2 would not be
meaningful because of the overall low risk levels posed by the category.
The commenter (0138) believes that there are many fewer than 2 million
individuals with MIR values above 1 in 1 million and option 2 would not
significantly shift the risks for 450,000 of these individuals as EPA
contends in the proposal. Thus, the commenter (0138) believed that
current MACT controls result in levels of risk to the exposed population
that are much lower than calculated and already provide an ample margin
of safety. One commenter added that option 2 benefits are overstated
because facilities located in non-attainment areas have already begun to
reduce emissions and this effect is not reflected in the analysis.

Response:  For our response to comments pertaining to the selection of
the rule, refer to the preamble to the final rulemaking action.

Comment:  One commenter supported requiring additional controls on HON
sources only if they contain key HAPs in Table 38 that have the highest
risk.  However, the commenter noted that if this were the case, Table 38
would apply only sporadically throughout the HON and would result in the
divergence between regulatory provisions, thereby making the rule even
more complex.

Response:  Since we have decided to maintain the current level of
control for the HON rule, these comments are not relevant to this
rulemaking, and we are not providing a substantive response.

3.2	Basis of Decision

Comment:  One commenter (0138) believes that EPA was correct in not
considering background HAP concentrations in the risk analysis.  The
commenter (0138) contended that, contrary to the policy stated in the
Coke Oven Batteries NESHAP, considering background concentrations of HAP
is not allowed by the CAA, even as an additional factor to consider in
the ample margin of safety decision.  The commenter (0138) contended
that background emissions are independent of HON emissions.  The
commenter (0138) pointed out also that background concentration at HON
sources is caused by area sources and mobile sources, which are
regulated by other programs.

Response:  For the HON source category, we determined that it was not
necessary or appropriate to consider background concentrations in our
decision.  However, as explained in the final Coke Oven Batteries NESHAP
(70 FR at 19996-19998), we reserve the right in future rulemakings to
consider the effect of background concentrations in the second step of
the section 112(f) analysis.

EPA agrees that the natural reading of CAA section 112(f) is that EPA
should evaluate risks posed by the emissions only from the category or
subcategory.  Section 112(f)(2)(A) of the CAA instructs EPA to
promulgate standards for each category or subcategory for which it has
adopted MACT standards, if such standards are needed in order to provide
an ample margin of safety to protect public health.  The statutory
trigger provision at the end of CAA section 112(f)(2)(A), which mandates
that EPA conduct residual risk rulemaking when cancer risks to the
individual most exposed to emissions from a source in the category
exceed a designated level, clearly is directed exclusively at emissions
from the source category alone, and thus supports a reading that the
ultimate requirement of the provision likewise applies only to emissions
from the source category.

We further agree that Congress intended that EPA continue to apply the
same Benzene NESHAP test for determining when public health is protected
with an ample margin of safety that was in effect before the 1990 CAA
amendments.  See CAA sections 112(f)(2)(A)-(B).  After examining the
statutory scheme, the Benzene NESHAP, and sound policy concerns, EPA has
concluded that, in its assessment of "acceptable risk" for purposes of
CAA section 112(f), the agency will only consider the risk from
emissions from that source category.  This was the approach of the
Benzene NESHAP, wherein EPA limited consideration of acceptability of
risk to the specific sources under consideration rather than to the
accumulation of these and other sources on benzene emissions that may
occur at an entire facility.  See 54 FR 38061 (stating in regard to
consideration of natural background levels of a pollutant that
"considering other sources of risk from benzene exposure and determining
the acceptable risk level for all exposures to benzene, EPA considers
this inappropriate because only the risks associated with the emissions
under consideration are relevant to the regulation being established
and, consequently, the decision being made.").  EPA also rejected
approaches that would have mandated consideration of background levels
of benzene in assessing acceptability of risk.  Id.  These background
levels are not barred from EPA’s analysis, but EPA will consider them
along with other factors, such as cost and technical feasibility, in the
second step of its CAA section 112(f) analysis.  To decide otherwise,
EPA would have to conclude that CAA section 112(f) requires EPA to shut
down any source that emits HAP in an area with high background
pollution, even if the emissions from that source are extremely small
and do not appreciably affect overall risk.

EPA has concluded that the sound policy embedded in the Benzene NESHAP
remains the approach that EPA should follow in determinations under CAA
section 112(f).  At the first step, when determining "acceptable risk,"
EPA will consider public health risks that result from emissions from
the source category only.  Not only is this interpretation supported by
the text of the statute and prior regulatory practice, but we are
impressed and daunted at the practical problems of implementing a
compulsory facility-wide examination.  For example, in future rules, the
myriad of combinations of source categories present at different
facilities could create situations where nationwide consideration of
residual risk becomes a practical impossibility because every facility
would present a different fact pattern of source categories.  Yet CAA
section 112(f) contemplates national determinations, not case-by-case
evaluations and standards.

That said, EPA disagrees that CAA section 112(f) precludes EPA from
considering emissions other than those from the source category or
subcategory entirely.  EPA must still determine whether additional
reductions should be required to protect public health with an ample
margin of safety.  EPA believes one of the other relevant factors that
may be considered in this second step is co-location of other emission
sources that augment the identified risks from the source category.  The
Benzene NESHAP does not explicitly identify this as a relevant factor
under step two, but the decision does acknowledge that multiple
exposures to chemicals are important to understand and consider in
EPA’s overall implementation of its public health mandates.  See 54 FR
at 38059.

	The decision today is an example of a situation in which EPA has
neither rejected all consideration of this factor nor determined that it
is a relevant factor for purposes of ensuring that public health is
protected with an ample margin of safety.  We did not account for the
contribution of multiple HON facilities near each other ("clusters") in
estimating maximum risks.  The analysis of clusters of HON facilities
(HON emission points only) indicates that maximum risks are not
significantly affected by clusters but are instead driven by the nearest
facility.  In estimating population risks, we did include the impacts of
HON emission points from all facilities.  We did not include the impacts
of co-located source categories. EPA does not yet have information on
the emissions and emission release parameters to perform a refined risk
assessment of such categories.

	Comment:  One commenter (0136) argued that since EPA’s risk
assessment shows excess cancer risks greater than 1 in 1 million
remaining after application of the current HON requirements, EPA is
compelled under CAA section 112(f)(2)(A) to promulgate new standards,
and that the proposed Option 1 that leaves the existing standards in
place therefore violates the mandate of CAA section 112(f) to
"promulgate standards."

	Response:  EPA disagrees with the claim that CAA section 112(f)(2)(A)
unambiguously requires a revision of current CAA section 112(d)(2)
standards in all situations where cancer risks remaining after
application of existing standards is greater than 1 in 1 million.  This
is because, as we state elsewhere, EPA continues to interpret CAA
section 112(f)(2) as expressly requiring only that any residual risk
standards be set at levels that protect public health with an ample
margin of safety in a manner that is consistent with the benzene NESHAP.
 Consequently, EPA may promulgate residual risk standards that reduce
cancer risks to, for example 1 in 10,000, and still comply with CAA
section 112(f)(2)’s mandate, even though the triggering facts for the
rulemaking – remaining cancer risks greater than 1 in 1 million –
might not be fully eliminated.  As the Act therefore permits
promulgation of residual risk standards based on a determination that
protection of public health with an ample margin of safety is achieved
at levels that are consistent with those discussed in the benzene
NESHAP, EPA believes it is also reasonable to read CAA section
112(f)(2)(A) as not requiring an affirmative revision of existing
regulations in cases such as the HON where, through rulemaking, the
agency determines that those standards already meet the benzene NESHAP
test.  In other words, we do not interpret CAA section 112(f)(2)(A) as
mandating that in cases like the HON EPA must tighten standards to some
degree that is more stringent than the level EPA would have had to
tighten them had the HON not already protected public health with an
ample margin of safety.

The commenter’s alternative reading makes sense only if CAA section
112(f)(2) absolutely requires all residual risk standards to eliminate
all cancer risks greater than 1 in 1 million.  EPA has consistently, in
the residual Risk Report to Congress and in all prior residual risk
rulemakings, rejected this reading as being flatly inconsistent with the
plain language of the statute and not based in sound policy.
Alternatively, assuming for argument that CAA section 112(f)(2)(A)
requires promulgation of new standards whenever cancer risks exceed 1 in
1 million, even while imposing a substantive mandate that such cancer
risks be reduced only to levels that protect public health with an ample
margin of safety as EPA interprets that threshold, we assert that the
final residual risk rulemaking for the HON satisfies any duty to
"promulgate standards" under CAA section 112(f), since our action
effectively re-adopts the HON (with minor revisions) as fulfilling the
substantive mandate of CAA section 112(f), in addition to its previously
fulfilling the mandate of CAA section 112(d).  In other words, any duty
to "promulgate standards" under CAA section 112(f) can be discharged by
EPA’s determining, through a rulemaking process that effectively
constitutes re-adoption of those standards, that the existing CAA
section 112(d) standards already protect public health with an ample
margin of safety.

	Comment:  The commenter (0132) indicates that Option 2 does not pass a
benefit-cost test based on a comparison of the benefits from VOC and HAP
reductions compared to the compliance costs.  The commenter also states
that the Agency should have considered emission trading and other
market-based control options in the proposal.

	Response:  We have decided that the final rule will not require any
changes to the control requirements under the HON.  Therefore, both the
costs and benefits of this final rule are zero, and there are no HAP,
and no VOC, emission reductions associated with this final rule.

	The Agency does not agree with the use of VOC benefits per ton
estimates that the commenter relies on for its calculations of
ozone-related health and welfare benefits from VOC reductions.   These
estimates are based on outdated benefits estimation methodologies and
air quality modeling techniques and no longer represent estimates that
we support for purposes of regulatory analysis.   The use of generalized
average benefits estimates based on VOC reductions is suspect since
reductions in ambient ozone concentrations from VOC emission reductions
often vary considerably by locality; thus, estimates of benefits coming
from VOC reductions are often highly locality-specific.   We have
commented on these same VOC benefits per ton estimates as part of
comments submitted by the Agency on the 2005 Thompson Report (also known
as OMB’s Report on Costs and Benefits , and our comments from that
report still stand here.

	The Agency does not have a credible estimate of VOC benefits per ton
available for purposes of regulatory analysis at this time.  The Agency
is currently working on development of ozone-related health and welfare
benefits estimates from VOC reductions as part of its regulatory impact
assessment for the revised ozone NAAQS that will be issued by February
2008.

	While we agree with the commenter that consideration of emissions
trading-alternatives to reduce HAP emissions, implementing such
alternatives for reducing HAP emissions is often problematic.  There is
often difficulty in establishing toxicity-weighted factors to compare
HAPs for purposes of emissions trading since metrics for comparing the
toxicity of different HAPs are often imprecise.

4.0	SECTION 112(d)(6) OF THE CLEAN AIR ACT

Comment:  Several commenters (0131, 0137, 0140) supported EPA’s
decision that CAA section 112(d)(6) does not require another analysis of
MACT floors for existing sources and new sources.  One commenter (0140)
contended that the language of the CAA requires EPA look into practices,
processes, and technologies, but there is no requirement to do so by
performing another MACT floor analysis.  Another commenter (0136) stated
that EPA’s section 112(d)(6) review is fundamentally unsound and
unlawful.  The commenter (0136) believes that EPA must perform a revised
MACT floor analysis and then evaluate controls beyond the floor; and
that these analyses cannot take risk or cost into consideration.  The
commenter (0136) claims that EPA has illegally combined risk
considerations into the section 112(d)(6) analysis in such a way as to
effectively render the section 112(d)(6) analysis redundant and
unnecessary.  The commenter (0136) argued that section 112(d)(6)
requires EPA to revise its section 112(d) standards as necessary
considering developments in practices, processes, and control
technologies that have the effect of reducing emissions.  The commenter
(0136) interprets this language as meaning that the review must parallel
the mechanism for establishing the original standard, meaning that a new
MACT floor must be established.  Otherwise, the commenter (0136)
contends that the term "review and revise" is rendered vague and
meaningless.

Response:  As we explained at proposal, EPA does not interpret CAA
section 112(d)(6) as requiring another analysis of MACT floors.  Our
interpretation regarding reviewing MACT floors was discussed in the
final Coke Oven Batteries NESHAP (70 FR 20008).  The natural reading of
the provision is that we are to review the CAA section 112 standards
considering developments in practices, processes and control
technologies.  EPA may then, in its discretion, amend the standards if
the agency concludes such action is necessary.  We believe this is the
meaning Congress intended, since CAA section 112(d)(6) originated  in
the House and Senate Committee provisions that predated introduction of
the MACT floor language and mirrors routine periodic re-evaluation
requirements found in other statutory provisions requiring
technology-based standards.  Moreover, we reiterate that there is no
indication that Congress intended for CAA section 112(d)(6) to
inexorably force existing source standards progressively lower and lower
in each successive review cycle, the likely result of requiring
successive floor determinations.  We note that with respect to revision
of standards for new sources, the CAA section 112(d)(6) analysis of
practices, processes and control technologies, and costs and emission
reductions associated with those technologies (conducted as part of the
determination of whether further controls are necessary), may indicate
that revised standards for new sources are warranted.  However, for the
HON, we have not identified any such developments that would be
reasonable to impose on all new sources, after considering costs.

Comment:  Two commenters (0131, 0134) contended that many source
categories, like the HON source category, that present maximum
individual risks greater than 1-in-1 million have only a relatively
small number of sources within the category at these higher risk levels.
 The commenter (0131) stated, as a result, the potential for meaningful
cost-effective risk reduction will be limited at best to these few
sources with higher individual risks.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is not relevant to this
rulemaking, and we are not providing a substantive response.

5.0  CONTROL OPTIONS

5.1	General Comments

Comment:  One commenter (0136) believes that chloroform, ethylene
glycol, methyl chloride, and toluene should have been included in the
proposed Table 38 list and therefore regulated under the proposed Option
2 because these chemicals exceeded their reference values a total of ten
times in the ACC data sample, and are emitted in very large quantities
by SOCMI facilities. Ethylene glycol, in particular, has only the MRL
value for reference, but exceeded that value several times by up to a
factor of 20.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is not relevant to this
rulemaking, and we are not providing a substantive response.  However,
elsewhere in this document we address the acute assessment for each of
the HAP mentioned by the commenter.

Comment:  Two commenters (0123, 0128) argued that in the HON regulation
amendment proposal, the USEPA has not addressed weaknesses of the
existing HON regulation that contribute to high levels of residual risk
from SOCMI facilities.  The commenters (0123, 0128) argued that elevated
flares should not be considered a maximum achievable control technology
and USEPA should reduce residual risk from SOCMI sources subject to the
HON regulation by eliminating the option of controlling emissions from
process vents and other sources with an elevated flare.  The commenters
(0123, 0128) contend that the accepted destruction efficiency of an
elevated flare (98%) is low in comparison to other available control
devices that can be utilized to comply with the HON regulation and that
studies have shown that the assumed destruction efficiency of 98% for an
elevated flare is overstated.

Response:   We disagree that the report cited by the commenter provides
a sufficient basis for disallowing the use of elevated flares as a
control device option for complying with the HON emission standards.
While the report cited by the commenter discusses the potential for
decreased flare performance due to poor operation and meteorological
conditions (i.e., high crosswinds), the report does not provide
sufficient data to substantiate the commenter’s assertion that the
performance of flares (specifically, elevated flares) is overstated or
to revise the control options provided in the HON.

Comment:  While EPA stated that it did not identify other technically
feasible control technologies that to reduce HAP emissions, the
commenter (0136) was unconvinced, without further information, that EPA
made a sufficient attempt to identify other control technologies.  The
commenter (0136) maintains that EPA must explore, among other things,
whether current control technologies are capable of better control
efficiencies, whether alternative processes or less toxic substitutes
are available, and whether work practice standards might reduce
emissions further.  The record shows that some States and local agencies
have rules that are more stringent than the HON, but the commenter
stated that EPA failed to describe those standards, to explain how
sources are able to comply, or to otherwise explore these more stringent
limits which have obviously been demonstrated to be feasible.

Response:  We disagree with the commenter’s assertions.  As documented
in the HON background information documentation, the best control
technology for reducing emissions from process vents was determined to
be combustion, and the best technology for reducing emissions from
storage vessels was determined to be converting tanks to floating roofs
or routing vent streams from fixed tanks through a closed vent system to
a combustion device.  We are not aware of any technologies or control
techniques that would provide greater reduction or that the current
technologies can achieve higher emission reductions consistently and
continually.  Using alternative processes or substitution are not
appropriate control techniques for these sources .  The best technique
for controlling emissions from leaking equipment is a leak detection and
repair program or using leakless equipment.  Memoranda in the docket
document the analysis of various parameters for a leak detection and
repair program (e.g, more frequent monitoring, reducing percent leakers,
and lower leak definitions) and use of leakless equipment.  The
memoranda show that the emissions reduction associated with leakless
equipment does not justify the cost of the equipment, and that lower
leak definitions do not necessarily provide better emission reductions.
The memoranda and preamble to the final rulemaking explain that EPA has
decided that the emissions reductions from more frequent monitoring or
lower percent leakers do not justify the costs of control.  The
commenter did not provide data to support their assertions.  Therefore,
the impacts estimation methodology remained unchanged from proposal.

Comment:  A commenter (0147) stated that under the proposed Option 2,
there will be cases where a Group 2 storage vessel or process vent would
be deemed Group 1 where the amount of table 38 HAP in the stream is
relatively insignificant.  The commenter suggested a revision to Option
2 such that the proposed applicability criteria for Group 1 would be
based only on emissions of table 38 HAP (e.g., the A TRE considering
only table 38 HAP in the gas stream).

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is not relevant to this
rulemaking, and we are not providing a substantive response.

Comment:  One commenter (0136) contended that EPA underestimated risks
by inappropriately omitting cooling towers and other auxiliary
emissions. The commenter (0136) stated the with just 16 out of 238
facilities reporting, EPA has information that HON cooling towers
themselves have cancer risks above 1 in one million. The commenter
(0136) concluded this data suggests that cooling towers, and perhaps
other auxiliary equipment, contribute meaningfully to the total risk
from HON facilities, particularly for those individuals living in close
proximity to these plants.

Response:  The commenter is correct that cooling towers have the
potential to pose risks as high a 1 in-one-million.  We analyzed risks
from 16 facilities with reported data on HON cooling towers.  The
estimated cancer risk for two of these 16 plants was 1 in-one-million.
In both cases, these cooling towers were located a facilities with whole
facility risks above 100 in-1-million. No cooling towers had a hazard
index greater than 1.  From this screening analysis, we concluded that
cooling towers are not a significant source of risk at HON facilities.

Comment:  One commenter (0138) contended that EPA’s claim of 1,600
tons/yr. of associated VOC reductions are overstated and very little, if
any, VOC reduction is likely to occur as a result of this program.  The
commenter (0138) added that VOC reductions are not a reduction of a HAP
and therefore not relevant under section 112(f) or section 112(d)(6).

Response:  We disagree with the commenter that VOC reductions associated
with proposed Option 2 are overstated.  The calculation of VOC emission
reductions is based on the methodologies described in the background
memoranda to the proposal.  The commenter did not provide additional
information or revisions to the methodologies for us to consider.  VOC
reduction estimates were only provided as additional information for the
proposed rule.  The selection of the options at proposal was based on
HAP reductions only.  Since our final decision is to not amend the
standards, it is not necessary to respond to the commenter’s claim
regarding our authority to consider VOC reductions under sections 112(f)
and (d)(6).

5.2	Equipment Leaks

Comment:  Several commenters (0135, 0138, 0140) opposed the proposed
valve monitoring program citing that it would be inefficient,
inequitable, overly costly, and would achieve minimal reductions.  The
commenters (0126, 0129, 0138, 0140) supported allowing alternative
compliance procedures and strategies, such as repairing valves at 200
ppm leak rate in lieu of monthly monitoring.  One commenter (0140)
supported incorporating into subpart H as generic equivalents that may
be used by all HON sources subject to the Option 2 requirements all
alternatives that are approved through a Federal Register notice and
comment.  The commenter (0140) stated that sources should be able to
include Non-HAP valves into any new valve monitoring program and the
Agency should provide a mechanism for easy adoption of valve emission
reduction alternatives or replace the proposal with a programmatic
approach that would allow sources to use whatever approach best fits
their situation.  The commenter (0140) believed that Option 2 must allow
for the use of whatever technology best addresses valve emissions at a
particular site.  Additionally, the commenter (0140) believed that
guidelines specific to the Option 2 requirements must be established
under the more general §63.177(d) authority of subpart H.
Additionally, One commenter (0129) stated that no data has been provided
that demonstrates the proposed valve monitoring program will reduce
emissions and that the valve monitoring proposal could lead to an
increase in injuries.

One commenter (0129) argued that the proposed valve monitoring program
requires hundreds of thousands of additional hours of monitoring and
repair effort and this exposes monitoring and repair personnel to the
level of safety risk inherent in working in industrial environments.
The commenter (0129) contended that EPA has underestimated that
additional cost for monthly monitoring of process unit valves.

Three commenters (0129, 0138, 0147) contended that the valve monitoring
proposal, if adopted, should only apply to valves contacting materials
containing >5 wt% Table 38 HAP.  One commenter (0129) added that by
applying the program to only valves that contain significant levels of
Table 38 HAP, the costs would be reduced but the calculated health
impacts would still be attained.  While there would be additional costs
to separately identify and track the valves containing 5% Table 38 HAP,
this cost would be small and non-recurring relative to the costs
associated with monitoring all valves in HAP service. The commenter
(0129) stated that equipment leak regulations dealing with HAP,
including subpart H, have generally excluded components containing less
than 5 wt% HAP to reflect their low contribution to HAP emissions.

Two commenters (0138, 0140) believed that one year would be needed to
implement any new valve monitoring requirements since sources will need
to evaluate alternate compliance approaches, modify applicable permits,
hire and train additional contractors, identify the valves subject to
the new requirements, and modify their leak detection and repair (LDAR)
data systems to handle this different set of requirements.  The
commenter (0138) added that sources cannot take advantage of the time
between proposal and finalization of this rule because they do not know
how the Agency will respond to the comments being submitted, which
include suggestions for significant changes to the proposal.

One commenter (0138) argued that any additional valve requirements
should only apply on a CMPU basis and added that EPA’s application of
the proposed valve monitoring program on a CMPU by CMPU basis is
consistent with the application of current subpart H and recognizes the
significant differences that are typical of HON processes. Further, the
commenter (0138) stated that individual CMPUs at a source are often
quite different, will have different HAPs, different valve
characteristics, different leak rates and different risk and
environmental impacts.  The commenter (0138) contended that applying the
new requirements on a CMPU basis rewards good performance by providing
reduced monitoring frequencies and thus benefits the environment.

Response:  Since we have decided to maintain the current level of
control for the HON rule, these comments objecting to the equipment leak
changes in proposed option 2 are moot, and it is not necessary for us to
respond substantively to them.

Comment:  Two commenters (0126, 0138) stated that the methodology for
estimating the HAP reduction in document 106 of the docket is a flawed
methodology since it is based on the unrealistic assumption that all
CMPUs will achieve and maintain a 0.5% leak rate.  One commenter (0126)
contended that a 0.5% leak rate for valves cannot be consistently
achieved.  Another commenter (0138) added that some CMPUs have not even
been able to meet the current 2% leak rate monthly monitoring criteria.
The commenter (0138) also stated that EPA’s cost analysis in document
106 supports that the methodology is flawed because it assumes monthly
monitoring is required indefinitely (i.e., 0.5% is never achieved) and
that the same number of valves require repair month after month (i.e.,
monthly monitoring results in no change in leak rate). Thus, the
commenter (0138) added, EPA’s own analysis does not support the
assumption that 0.5% will be achieved and thus the claimed emission
reduction also fails.  Additionally, the commenter (0138) argued that
even accepting that sources might achieve 0.5% leak rates temporarily
during a month and then return to the preexisting leak rate before the
next monitoring period, as the Agency cost methodology seems to assume,
the emission reduction would be no more than 50% of the 910 tons per
year calculated by the EPA methodology.

Another commenter (0136) stated that EPA provided no credible rationale
for the decision not to analyze alternative lower leak definitions.  The
commenter (0136) opposed EPA’s statement that it is not appropriate to
reduce the leak definition below 500 ppmv because Method 21 has not been
validated at below 500 ppmv and that there is no data for assessing the
associated emission reductions. The commenter (0136) added that if there
is a technical reason why these emissions actually cannot be detected,
that must be explained – but 50 and 20 ppmv measurements are used
elsewhere in the standards, suggesting that there is no technical basis
for this claim. The commenter (0136) also thought that EPA should have
considered the option of 0.25 percent leakers

Response:  We disagree that 0.5% leak rate cannot be maintained.  The
information provided to EPA for the analysis shows that several
facilities operate with leak rates less than 0.5%.  Monthly monitoring
was used in the equipment leaks analysis to provide the most
conservative estimate of costs.  After proposal, we also analyzed costs
if all facilities or a fraction of the facilities, were able to meet the
0.5% leak rate.  We also reviewed impacts of requiring 0.25 percent
leakers.  The results of the analyses are documented in background
memorandum in the docket.   However, we have decided to maintain the
current level of control for the HON rule and not incorporate additional
equipment leak requirements because the emission reductions and benefits
did not warrant the costs.

  We disagree with the commenter regarding analyzing leak rates below
500 ppm.  The costs and emission reductions were calculated using
information in the EPA’s Equipment Leaks Protocol.  The protocol
provides estimation techniques for leak definitions of 500, 1000, 10000
ppmv.  It does not provide estimation techniques for leak definitions
lower than 500 ppm.  Therefore, the benefits and costs of lower levels
cannot be evaluated.  We do not know of any estimation techniques for
lower leak definitions, and the commenter did not provide any additional
information.

Comment:  One commenter (0138) stated that the document 106 calculation
procedure fails to account for the emissions from "non-leaking" valves,
which for CMPUs with large numbers of valves will be significant.
Emissions from valves leaking below the leak definition were included in
the baseline data provided to EPA and should have been added to the
emissions calculated for the leaking valves before the difference
between the baseline and future emissions was calculated.  The commenter
(0138) added that while it did not have the data to quantify the impact,
the commenter’s (0138) experience is that the calculation error would
be expected to lead to a significant overstatement of the potential
emissions reduction. Second, the commenter (0138) stated that the
document 106 calculation procedure also contains a formula error that
underestimates the emissions associated with a 0.5% leak rate. Further,
the commenter stated that according to page 3 of the document, the
post-control emissions were calculated using the formula that only
applies to valves in gas service.  The commenter (0138) stated that for
every 1,000 valves in light liquid service, as opposed to gas service,
this error results in understating the post control emissions by 0.23
tons/yr.  Additionally, the commenter (0138) stated that while the ratio
of light liquid to gas valves is different for every process, in their
experience it is likely that at least half the valves in the source
category are in light liquid service, leading to an understatement of
the calculated post control emissions of at least 50 tons per year for
the source category.

Response:  We disagree with the commenters assertions.  We conducted the
equipment leaks analysis using the best information available to us.
The equipment leak costs and impacts were calculated using information
from two different data sources.  The ACC data provided emissions
information, while notification reports provided equipment count
information.  Neither of these data sources provided information on
non-leaking sources, or sources leaking below the leak definition, nor
was there any information provided that would allow us to identify these
sources.  The commenter is directed to the memorandum "Cost and Emission
Reductions from Meeting Percent Leaker Requirements" for a detailed
description of this analysis.  We were able to calculate the number of
sources already meeting the 0.5 percent leak rate.  Since these sources
already met the leak rate requirements, they were not included in the
emission reduction or cost analyses.  We did not know the number of
light liquid or gas valves that would be at each facility.  We used the
emission factors for gas valves to simplify the calculation and because
there are generally more gas valves than light liquid valves at ACC
facilities.  The use of the gas valve emission factors provides a higher
emission reduction and benefit than using the light liquid valve
emission factor.  EPA has decided to maintain the current level of
control for the HON rule instead of requiring more stringent
requirements as discussed elsewhere.  Using the light liquid emission
factor would decrease the benefits further and would not change the
outcome of the analysis.

Comment:  Two commenters (0129, 0138) contended that the baseline
emissions used for the EPA analysis were 1999 values and are 22% higher
than the fugitive emissions data for SIC code 28 sources from the
EPA’s Toxic Release Inventory. One commenter (0138) stated further
that since the estimate of valve emissions at the assumed 0.5% leak rate
would not change, the calculated potential emissions reduction is much
less than EPA claims. The commenter (0138) added that using the
emissions data from the data table associated with a 0.5% leak rate
(document 106.1), this correction in baseline emissions alone results in
an approximately 40% reduction in EPA’s calculated emissions reduction
(from 910 tons per year to about 550 tons/yr.).

Response:  We conducted the equipment leaks analysis using the best
information available to us.  As documented in the memorandum "Cost and
Emission Reductions From Leakless Valves for HON Facilities",  the ACC
provided emission information for 105 HON facilities.  The information
from the TRI also comes from facilities reporting directing to TRI; the
information should be the same.  Information may be different between
the two data sources because of different years reporting, or different
facilities providing information.  We chose to use the ACC information
because it provided information on a processes unit level and TRI does
not provide the same level of detail.  We also wanted to remain
consistent in using the same data sources for all source categories.

Comment:  One commenter (0140) supported EPAs decision not to replace
existing valves with "leakless" valves due to expense and because it is
impractical.  The commenter (0140) contended that physical valve sizes
are generally much larger making them impractical in a retrofit
situation, and the cost associated with retrofitting includes a major
reconfiguration of the process and thus such expenses would render the
cost per emission reduction as unreasonably high.

Another commenter (0136) contended that EPA should have considered the
option of requiring partial implementation of leakless valves. The
commenter  (0136) stated that EPA summarily dismissed requiring all
valves to be replaced but included no analysis of requiring leakless
valves on specific equipment that might be most reasonable to control
based on factors such as flow rates or the likelihood of failure, or
other options such as a gradual phase-in of leakless valves.

Response:  We conducted the analysis of leakless valves using the best
information available to us.  We did not have information on the
specific types of valves at each facility.  Therefore, we could not look
at a specific subsection of valves to be replaced with leakless valves.
However, the leakless valve analysis shows that the cost of replacing
any valve with a leakless valve would be high relative to the emission
reduction achieved.  We note that the commenter did not provide
additional information that could be used to revise the analysis.

5.3	Process Vents

Comment:  One commenter (0129) requested EPA clarify that TRE
calculations are based on maximum annual average HAP.  The commenter
(0129) stated that since there can be variability in the HAP content of
process vents (e.g., as cooling water temperatures changes from summer
to winter or operating conditions vary), it is important that the Agency
be clear what HAP content is used in the TRE calculation.

Response:  Since we have decided to maintain the current level of
control for the HON rule, these comments are now moot and it is not
necessary for us to provide a substantive response.

Comment:  Several commenters (0129, 0138, 0140, 0144) opposed the
process vent TRE cutoffs because costs are understated because the TRE
formula is based on 1982 dollars which EPA has not adjusted to current
dollars.  One commenter (0138) contended that the cost to control vents
with a TRE between 1.0 and 4.0 is greatly underestimated and additional
control of process vents is not justified under ample margin of safety
or CAA section 112(d)(6) criteria.  Another commenter (0140) added that
EPA did not include costs of rising energy prices.  The commenter (0140)
contended that any change to the current TRE index value provisions
should not be based on anticipated reductions of VOC that are not HAPs.
One commenter (0136) questioned why EPA picked a TRE of 4, which only
removes 640 tons of HAP per year at 14 facilities (and volatile organic
compounds or VOC by 1,100 tons per year). The commenter (0136) claimed
that process vents are a main source of HAP emissions at a substantial
fraction of facilities, judging by data submissions in the docket. Thus,
removing less than 1% of remaining HON HAP emissions via this control is
unreasonably low.

Response:  We disagree with the commenters.  The TRE information was
updated to 2002 dollars using the chemical engineering cost indices.
The cost and emission reductions from applying a TRE of 4 were only
applicable to sources with a Table 38 HAP.  The emission reductions
calculated were for total HAPs in the vent stream that would meet the
new applicability requirements, not of the VOC reductions.  We also
analyzed impacts from requiring a TRE of 2 and 3.  However, considering
the costs and emission reductions for each of the TRE values analyzed,
we determined to maintain the current level of control for the HON.  The
costs for controlling process vent streams with TREs greater than 4
exceeded the benefits that would be incurred.

Comment:  Several commenters (0129, 0138, 0144) contended that a de
minimis level should be established to exclude Group 2 process vents
from the Group 1 controls if they contain only a small amount (e.g. 1000
ppm) of a Table 38 listed HAP.

Response:  Since we have decided to maintain the current level of
control for the HON rule, these comments are now moot and it is not
necessary for us to provide a substantive response.

Comment:  Several commenters (0129, 0138, 0144) argued that it is
arbitrary and capricious to apply the proposed new control requirements
to existing Group 1 process vents in addition to existing Group 2
process vents, since Group 1 vents were not included in the data
evaluated by the Agency.  One commenter added the they opposed EPA
finalizing the proposed regulatory language for the following reasons:
1) the proposed language does not follow and is not supported by the
preamble description, 2) changing the control requirements for existing
Group 1 process vents was not considered in the CAA section 112(f) or
section 112(d)(6) analyses, 3) there is no information in the record on
the emission impact or costs of changing the Group 1 control requirement
for existing process vents, and 4) EPA has not evaluated the impacts of
such a change consistent with applicable legal or executive order
requirements.

One commenter (0131) contended that since the Agency only studied Group
2 vents, there is no basis or data on the costs or impacts of changing
the control requirements for existing Group 1 vents.  Further, the
commenter (0131) stated that the proposed rule expands, arbitrarily and
without considering the cost impact, the new control requirements to
Group 1 process vents in addition to Group 2 vents.

Response:  We used the best information available to us for the
analysis.  The information gathered included data on stream properties
and pollutant emissions.  From this data we were able to calculate TRE
information for all the process vent streams.  None of the streams had a
TRE less than 1.  Therefore, they were unlikely to be Group 1 streams.
We also analyzed controlling vent streams with a TRE value less than 2
or 3.  However, considering the costs and emission reductions for each
of the TRE values analyzed, we determined to maintain the current level
of control for the HON.  We would also like to clarify that the proposed
new control requirements were not being applied to existing Group 1
process vent streams.  They were only being applied to Group 2 streams
that had a TRE less than 4 and contained at least one Table 38 HAP.

5.4	Transfer Operations

Comment:  Two commenters (0140 and 0151) agreed that no further controls
are needed for transfer operations.  HAP emissions after compliance are
very low and because the amount of uncontrolled emissions at a HON
transfer operation, as a percentage, pose little risk as compared to the
entire CMPU.  One commenter (0140) added that uncontrolled transfer
racks are likely unloading racks which are now controlled by another
NESHAP.

Another commenter (0136) observed that EPA prepared no technical
analysis memo for transfer operations. The commenter (0136) objected to
the decision not to regulate transfer operations based on the claim of
low emissions (400 tons per year) and unsupported statements that
controls are expensive. Some ACC data submissions e.g. for Borden, LA,
illustrate that the emission profiles vary greatly for each plant, and
the commenter (0136) believes that transfer operations may account for a
high percentage and volume of HAP emissions in some cases. Since
contribution to risk depends on factors such as proximity to fenceline
and distance to surrounding populations in addition to emissions, this
emission source should not be completely ignored without adequate
analysis.

Response:  EPA should have better explained why control options for
transfer operations were not examined.  As noted by the commenter, EPA
stated that emissions from transfer operations are low relative to the
emissions from other points, but EPA agrees with the commenter that
there is significant variability in the magnitude of emissions from
transfer operations and that other factors, such as the distance to
receptors, are important in assessing risk.  However, EPA concludes that
the potential risk reductions from transfer operations are minimal.
This conclusion is based on the findings that cancer risk would be
insignificantly affected and that EPA has not identified a noncancer
hazard index greater than 1 in the assessment from these activities.

Transfer operations subject to HON control requirements are already
achieving maximum achievable control (98% reduction or higher).  There
is also minimal risk reduction potential from uncontrolled transfer
operations.  Considering 200 pounds per year (0.1 tons per year) as an
emissions level below which significant risks are unlikely, 26 of the 28
emission points (using the industry dataset of 104 facilities) that
exceed this emissions level emit only HAP for which there are no cancer
unit risk estimates.  Therefore, EPA cannot estimate cancer risks or
risk reductions from such points.  For the two facilities that emit more
that 0.1 tons per year of HAP (that have cancer unit risk estimates)
from transfer operations, transfer operations do not contribute
significantly to the estimated cancer risk from these facilities.
Because of the minimal risk reduction potential from transfer
operations, EPA chose to target other emission points with more
substantial HAP emissions to examine risk reduction options.  After
examining such higher-emitting processes and equipment, we have
concluded that no further regulatory controls of those emissions points
are needed in order to protect public health with an ample margin of
safety, and that the additional less substantial emissions from transfer
operations do not affect our overall conclusions regarding HON sources.

5.5	Wastewater

	Comment:  One commenter (0151) supported EPA’s decision not to
require additional controls under either option for Group 2 process
wastewaters.  The commenter (0151) stated that at an estimated cost per
ton of HAP reduced of $410,000, additional controls would be
prohibitively expensive for little actual risk reduction.

Another commenter (0136) objected to EPA’s decision not to consider
process wastewater controls on the basis that such control is too
expensive. The commenter noted that by EPA’s own analysis, at least 9
facilities would be controlled under the $12,000/ton mark established
for storage vessels. Thus, the commenter (0136) claimed that declining
to regulate process wastewater, which contributes well over 1,000 tons
of HAP per year (extrapolating from 495 tons per year for the 104 ACC
facilities) is irresponsible. The commenter (0136) stated that EPA has
not justified why it could not use the sorts of cost or emission
thresholds it has proposed in other provisions, rather than merely
choosing between regulating all currently unregulated wastewater streams
or none. The commenter (0136) believes that EPA should analyze options
that extend control to some Group 2 wastewater streams by considering
different flow rate or HAP concentration cutoffs.

	Response:  We used the best information available to us to calculate
impacts.  While the ACC data contained sufficient information to
estimate HAP emission reductions, flow rate data for individual streams,
which is necessary to estimate control costs, were not available.  To
determine whether control of Group 2 wastewater streams would be
feasible and whether additional data gathering would be warranted, we
estimated cost per ton of HAP removed for each facility using the HAP
emission reductions calculated from the HAP emissions requested in the
ACC survey and steam stripper cost estimates developed for model
streams. The model streams were based upon comparable chemical
manufacturing processes and wastewater HAP emissions data from
rulemaking docket for the NESHAP for miscellaneous organic chemical
manufacturing (40 CFR part 63, subpart FFFF). These data were grouped
into HAP loading (kg/liter) ranges and default flow rates were estimated
for each range. The default flow rates were assigned to wastewater
streams for the facilities in the ACC survey data based upon the HAP
loading for each stream (estimated from the reported HAP emissions).

For some wastewater streams, the analysis resulted in flow and
concentration characteristics that would qualify the streams a Group 1
(i.e., requiring control under the HON).  At proposal, we left these
streams in the analysis even though we were evaluating the feasibility
of controlling Group 2 streams.  Retaining these stream characteristics
resulted in a conservatively estimated low cost per ton of control for
the facility because these streams are the most cost effective to
control.  Even with these streams included, only two facilities out of
105 were estimated to have control costs of $12,000 per ton or less.  If
we eliminated the estimated Group 1 streams from the analysis at these
facilities, then only one of the 9 model streams that did not meet the
Group 1 flow rate and concentration criteria had a cost per ton of HAP
removed that was less than $22,500 per ton of total HAP reduced.  We
concluded from this study that if we had the data necessary to analyze
emission thresholds for individual streams, as the commenter suggested,
it is likely that relatively few streams could be controlled at a
reasonable cost.  As a result, we determined that the cost of
controlling Group 2 wastewater streams was not reasonable, and that
expending the time and resources required to collect detailed process
data required to conduct a more thorough regulatory analysis and set
standards was not warranted.  The commenter did not provide any
additional information that could be used to revise our analysis.
Therefore, we kept the same methodology.

6.0 RISK ANALYSIS

6.1	Risk Factors

Comment:  One commenter (0138) believes that EPA should develop a
petition process for updating the health benchmarks used for residual
risk assessments and should consider all sources of data, not just IRIS,
ATSDR, and CalEPA data.  No specific comments were made pertaining to
this rulemaking.

Response:  EPA disagrees with the commenter that such a petition process
is needed.  EPA’s Office of Air Quality Planning and Standards
maintains tables (http://www.epa.gov/ttn/atw/toxsource/summary.html) of
dose-response values that it uses for risk assessments of hazardous air
pollutants.  Sources of dose-response assessments are selected to
reflect conceptual consistency with EPA's risk assessment guidelines and
IRIS assessment process.  In particular, each selected source subjects
its assessments to scientific peer review and public comment.  Thus,
because there now exists a review and comment process for each source of
dose-response values, EPA does not agree that an additional process is
necessary.

Comment:  The commenter (0146) believed that EPA has significantly
overestimated the risk associated with exposure to acrylonitrile (AN).
The commenter (0146) requested that, as part of its efforts to finalize
and promulgate this proceeding, the Agency complete in an open and
transparent fashion its AN IRIS assessment, by relying on the best
science available.  The commenter (0146) added that the health risk
assessment EPA relies upon for acrylonitrile is based on outdated
information and is significantly in need of being updated.  The
commenter (0146) stated that this is readily apparent when one considers
that EPA’s assessment assumes that IARC’s classification of AN is
category 2A (probable carcinogen) despite the fact that IARC downgraded
the classification of acrylonitrile in 1999 to category 2B (possible).
Also, the commenter (0146) stated that the unit risk estimate EPA used
in its assessment for AN was taken from the EPA’s Integrated Risk
Information System (IRIS), which is based on the available occupational
epidemiology information that existed in the early 1980s – a time
frame when this subject was just beginning to be explored.  The
commenter (0146) added that they sponsored an updated risk assessment
for AN that was performed by The Sapphire Group and that the complete
assessment and associated peer review report are posted on the
Toxicology Excellence for Risk Assessment (TERA) website.

Response:  EPA agrees that the IRIS assessment for acrylonitrile does
not consider studies published after 1991, and EPA is currently
developing an assessment that includes newer information.  EPA reviewed
the assessment described (and funded) by the commenter and concluded
that it does not conform with EPA science policy, as per EPA’s
Guidelines for Carcinogen Risk Assessment (EPA-630/P-03-001F), in three
ways.  First, the assessment concludes that the mode of action is
nonlinear, but is unable to identify a sufficiently supported nonlinear
mechanism.  Second, the assessment provides a supplemental linear unit
risk value but bases it upon animal data rather than human data.  Third,
the animal-based linear value was not documented adequately for EPA to
confirm the calculations.  In addition, there are other analyses and
interpretations in the assessment with which we take issue.  A full
evaluation of these data (including the TERA assessment) is currently
underway with the IRIS reassessment, the status of which may be viewed
on the IRIS web site.    HYPERLINK
"http://cfpub.epa.gov/iristrac/index.cfm"
http://cfpub.epa.gov/iristrac/index.cfm

Comment:  One commenter (0124) contended that in its calculation of
cancer potency for butadiene, EPA departed from standard EPA cancer risk
assessment methodology and disregarded Science Advisory Board
recommendations, such that the agency’s final cancer potency
calculation for butadiene is unusually conservative, and greatly over
estimates potential cancer risk even by EPA standards.  Two commenters
(0124, 0138)) added that EPA’s newest cancer potency estimate for
butadiene is 20 times higher than an estimate it made in 1999 that it
felt was "prudent" and that had the support of the EPA Science Advisory
Board.  Additionally, the commenter (0124) believed that the cancer
potency value calculated by NCEA in 1999 was a highly conservative upper
bound estimate, and as such was fully protective of human health.  The
commenter (0124) also argued that the butadiene health assessment
document, and its use in this rulemaking to support risk estimates, also
raise issues of transparency that may mask additional sources or
overestimation in EPA’s analysis.  Additionally, the commenter stated
that EPA relied on analysis that Health Canada used to model dose
response from human data but never obtained this analysis or released it
to the public.  Further, the commenter (0124) stated that this lack of
disclosure is in contradiction with the Office of Management and
Budget’s proposed risk assessment guidelines.

Response:  EPA did not follow the Science Advisory Board's
recommendation that a more appropriate model for risk would factor out
the peak-exposure component.  EPA considered a peak exposure analysis;
however, the data on peaks were inconsistent and did not support a
quantitative analysis that factored out peaks.  According to the
original study authors, based on their comprehensive dose-response
analyses, the relationship between 1,3-butadiene peak-years and leukemia
was irregular.  This situation obligated the risk estimates to be made
under the assumption of exposure being other than peak (e.g., average or
AUC) which will always give higher risk for the same tumor incidence.

EPA's use of the upper bound estimate for the point of departure for the
final unit risk estimate is consistent with EPA's 2005 Guidelines for
Carcinogen Risk Assessment (and with the interim draft of the guidelines
which was operational at the time the 1,3-butadiene assessment was
finalized).  This science policy established in the new Guidelines
eliminates the historical inconsistency in the treatment of human and
rodent data.  The policy of using an upper bound estimate is not
motivated by potential low-dose computational instabilities in the
models applied to rodent data, as this is not an issue under the
Guidelines' two-step approach of modeling the data in the observable
range to obtain a point of departure and then using linear extrapolation
or a non-linear approach to estimate the unit risk or a reference value
for cancer.  The Guidelines underwent their own external review process,
and the science policies presented therein are not generally topics for
which the EPA seeks external comment in its chemical-specific
assessments.  Another difference from some assessments (but fully
consistent with the Guidelines) was the use of a 1% tumor rate
(estimated by benchmark dose) as the point of departure for low dose
extrapolation, as this was the lowest tumor rate supported by the
observed animal data.

Comment:  One commenter (0138) maintains that the URE used by EPA is
about an order of magnitude overestimated for the EO risk assessment.
The commenter (0138) explained that for the HON risk assessment, EPA
used a dose-response value from CalEPA, because EPA is currently in the
process of developing a URE for EO. The commenter (0138) believes that
EPA should have developed a URE for this rulemaking based on the best
available science that is available today rather than use the outdated
CalEPA value. The commenter (0138) referred to an epidemiological
database for EO that includes exposure estimates for more than 20,000
workers collected in two studies.   The commenter (0138) pointed out the
importance of considering epidemiological evidence in this case, since
mononuclear leukemia in female rats, which is the basis for the CalEPA
URE, is not a relevant endpoint for humans.

Response:  In estimating potential cancer risk associated with ethylene
oxide exposures, EPA has considered all available, credible, and
relevant information.  In 1985, the EPA health assessment for ethylene
oxide1 concluded, based on the information available at that time, that
ethylene oxide is "probably carcinogenic to humans," and derived a
cancer unit risk estimate. The California EPA subsequently relied, in
part, on the USEPA assessment in developing their cancer unit risk
estimate, using the same rat study as quantitative basis.2,3 The
California EPA assessment received concurrence from their Scientific
Review Panel.4  In 1994, the International Agency for Research on Cancer
categorized ethylene oxide in their Group 1 (Carcinogenic to Humans).
In 2000, the United States Department of Health and Human Services
revised its listing for ethylene oxide to "known to be a human
carcinogen" in the Ninth Report on Carcinogens.5  Support for this
listing includes epidemiological evidence from studies of workers
exposed to ethylene oxide and animal studies. Cancer in both human and
animal studies has included multiple sites, including reported
associations with leukemia.6

EPA is currently developing an updated cancer assessment for ethylene
oxide
(http://cfpub.epa.gov/iristrac/index.cfm?fuseaction=viewChemical.showChe
mical&iris&_sub_id=897). EPA's updated cancer assessment for ethylene
oxide will consider all relevant literature and studies including the
Kirman, et al. paper7 and the epidemiological studies8,9 referred to by
the commenter. However, until completion of that assessment and given
the peer review status of the work done by the State of California, the
California EPA unit risk estimate must be considered to be the
best-available science and has therefore been used in assessing cancer
risk for this rulemaking.  The updated EPA cancer assessment was
released for public comment and external peer review in September 2006
(http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=157664).
Completion of the external peer review is expected in early 2007.
Because the updated EPA cancer assessment is still in draft form and
undergoing peer review, it was not used in this residual risk analysis.

	1USEPA. 1985. Health Assessment Document for Ethylene Oxide,
EPA/600/8-84/009F. Office of Health and Environmental Assessment,
Washington, DC.

	2 CARB. 1987. Staff Report: Initial Statement of Reasons For Proposed
Rulemaking and Report of the Scientific Review Panel. California Air
Resources Board.
http://www.oehha.ca.gov/air/toxiccontaminants/pdf1/ethylene%20oxide.pdf.

	3 CalEPA. 2005. Technical Support Document for Describing Available
Cancer Potency Factors. California Environmental Protection Agency,
Office of Environmental Health Hazard Assessment. Air Toxicology and
Epidemiology Section.   HYPERLINK
"http://www.oehha.ca.gov/air/hot_spots/pdf/May2005Hotspots.pdf"

http://www.oehha.ca.gov/air/hot_spots/pdf/May2005Hotspots.pdf .

	4 CARB. op. cit.

	5 DHHS. 2000. Report on Carcinogens, Eleventh Edition; United States
Department of Health and Human Services, Public Health Service, National
Toxicology Program.

	6 DHHS, op. cit.

	7 Kirman, C.R., et al. 2004. Addressing nonlinearity in the
exposure-response relationship for a genotoxic carcinogen: cancer
potency estimates for ethylene oxide. Risk Anal. 24(5):1165-83.

	8Steenland, K.L., et al. 1991. Mortality among workers exposed to
ethylene oxide. New England Journal of Medicine, 324(20):1402-1407.

	9Teta, M.J., et al. 1993. Mortality study of ethylene oxide workers in
chemical manufacturing: A 10-year update. British Journal of Industrial
Medicine, 50:704-709.

Comment:  One commenter (0138) stated that a 1991 ACC bagging study of
EO and phosgene showed that EPA correlations for equipment leaks from
HON processes overstate mass emissions by factors as high as 10.  The
commenter claimed that EPA accepted the results of the bagging study in
the 1995 equipment leaks protocol document (EPA-453/R-95-017).  The
commenter (0138) concluded that use of the emission factor overstates
the risk benefit from controlling equipment leaks.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is now moot and it is not
necessary for us to provide a substantive response.

Comment:  The commenter (0152) contended that the available data on
isophorone does not warrant its regulation based on a potential cancer
hazard.  The commenter (0152) stated that isophorone is included in
Table 38 because a chronic study conducted by the National Toxicology
Program ("NTP") in the 1980s reported an increase in preputial gland
tumors in male rats (but not female rats or mice of either sex).
Further, the commenter (0152) stated that EPA has judged this
information to be "limited" and has classified isophorone as a Group C
possible human carcinogen [www.epa.gov/IRIS].  The commenter (0152)
believed the preputial gland tumors observed in high dose male rats in
the NTP study were unlikely to be related to treatment; therefore, they
do not provide a scientific basis for regulating isophorone as a
potential human carcinogen or for including it in Table 38 of the
Proposed Rule.  The commenter (0152) provided additional rationale for
its position in the text of the comments.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is now moot and it is not
necessary for us to provide substantive response.

6.2	Risk-Assessment

Comment:  One commenter (0152) stated that EPA should not automatically
put a substance that has been classified as a "possible" human
carcinogen in Table 38 just because a cancer URE had been calculated.
The commenter (0152) did not believe EPA should interpret CAA section
112(f) as inflexibly requiring the regulation of all EPA Group C
compounds as carcinogens absent compelling support in the legislative
history as the available data related to these compounds are not
"sufficient."  The commenter (0152) stated that no such support has been
cited in the past, and we are not aware of any support in the
legislative history.  The commenter (0152) argued that treatment of EPA
Group C substances as if the underlying animal data were "sufficient,"
simply because a URE has been calculated, sets a bad scientific
precedent, and in effect disregards the initial assessment of the
strength of the available data.  The commenter (0152) believed EPA
should review the data for each EPA Group C carcinogen and should
include such a compound in Table 38 only if current scientific evidence
supports that approach.  The commenter (0152) added that ordinarily,
this would require that current evidence in animals be "sufficient,"
rather than "limited" using EPA's old terminology.  One commenter (0138)
believes that EPA should not consider the effects of Group C carcinogens
(possible carcinogen) in residual risk assessments, unless more current
data support a higher cancer classification. The commenter (0138)
maintains that Group C carcinogens should not have been considered in
the HON rulemaking because there is insufficient data to support a
finding of carcinogenicity and because EPA historically has not
regulated Group C compounds as carcinogens.  The commenter (0138)
pointed out that a peer review panel for the CAA section 112(g) relative
hazard ranking agreed that Group C compounds should not automatically be
treated a non-threshold pollutants. Accordingly, the commenter maintains
that the calculated risks for HON sources are overstated, thus further
supporting the selection of Option 1.  One commenter (0131) contended
that EPA should use inhalation reference concentrations instead of
carcinogenic slope factors for performing risk assessments for chemicals
in EPA former Carcinogenicity Class C and cited that the scientific
evidence supporting the determination that Group C chemicals are in fact
carcinogenic to humans is not very strong.

One commenter (0136) argued that Option 2 is defective and unlawful
because it regulates only Table 38 HAP and any HAP for which inhalation
UREs have been developed.  The commenter (0136) stated that Table 38
excludes control of inorganic HAP, chemicals with non-cancer health
risks and very low RfCs (like 1,1,1 trichloroethane), and numerous
chemicals that are unclassifiable, possible, and even probable
carcinogens (like chloroform, which is emitted in great quantities by
SOCMI CMPUs). The commenter (0136) contended that EPA’s use of the
existence of a URE as a cutoff for control has no rational basis,
because a lack of information necessary for quantifying risk is not a
justification for failure to regulate, particularly when the information
that is available shows a likelihood of carcinogenicity and other
toxicity. The commenter claimed that the lack of a URE does not mean the
HAP is of less concern, only that EPA has not gotten around to
developing the necessary estimate.

Response:  Since we have decided to maintain the current level of
control for the HON rule, the comments objecting to our consideration of
Group C carcinogens is now moot and it is not necessary for us to
provide a substantive response.

Comment:  One commenter (0147) stated that on 71 FR 34436, EPA attempts
to include benefits from collateral VOC reductions.  The commenter added
that this inclusion is misplaced as there are other programs directed at
ozone and fine particulate.

Response:  Since we have determined not to revise the control
requirements of the current rule, this comment is now moot and it is not
necessary for us to provide a substantive response.

Comment:  Several commenters (0125, 0130, 0140) argued that the EPA
needs to establish an administrative process by which HAPs can be
removed from Table 38 if the IRIS reviews for those HAPs result in an
assessment of less hazard since several of these HAPs are currently
undergoing review for their toxicological values under EPA’s IRIS
program.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is now moot and it is not
necessary for us to provide a substantive response.

Comment:  Several commenters (0129, 0131, 0135, 0138, 0144) suggested
that the rule should include cutoff levels to specify the concentrations
of Table 38 HAP that trigger applicability of new requirements.
Commenters added that lack of a concentration trigger would make it
difficult to implement the provisions, permit the, and enforce them.
One commenter (0131) argued that the process vent and storage vessel
requirements should not be triggered by very low levels of Table 38
hazardous air pollutants because almost all raw materials, intermediate
products, and finished products contain minimal amounts of some
chemicals, i.e., impurities.  The commenter (0131) also suggested that
the equipment leak provisions should only apply to valves in HAP service
that contain at least 5% of a Table 38 hazardous air pollutant.

Response:  Since we have decided to maintain the current level of
control for the HON rule, this comment is now moot and it is not
necessary for us to provide a substantive response.

Comment:  The commenter (0136) objected to the use of annual average
concentrations at the area-weighted centroid of census blocks.  First,
the commenter claimed that the approach significantly underestimates the
risk estimated for people at the fenceline, since the center of a census
block would be further away from the facility than those at the
fenceline.  Census blocks vary greatly in size yet EPA provides no
evidence that it reviewed census block size or configuration to consider
how concentrations of pollutants might vary within these blocks.
Secondly, the commenter contended that EPA did not examine these census
blocks to determine whether low income or minority populations might
suffer disproportionate risk.

One commenter (0138) supported EPA’s use of the centroids of census
blocks for estimating exposure.

Response:  EPA contends that, in a national-scale assessment of lifetime
inhalation exposures and health risks from facilities in a source
category, it is appropriate to identify exposure locations where it may
be reasonably possible an individual will spend a majority of his or her
lifetime.  Further, EPA contends that it is appropriate to use census
block information on where people actually reside, rather than points on
a fence-line, to locate the estimation of exposures and risks to
individuals living near such facilities.

Census blocks are the finest resolution available in the nationwide
population data (as developed by the US Census Bureau); each is
typically comprised of approximately 40 people or about 10 households.
In EPA risk assessments, the geographic centroid of each census block
containing at least one person is used to represent the location where
all the people in that census block live.  The census block centroid
with the highest estimated exposure then becomes the location of maximum
exposure, and the entire population of that census block experiences the
maximum individual risk.  In some cases, because actual residence
locations may be closer to or farther from facility emission points,
this may result in an overestimate or underestimate of the actual annual
concentrations (although there is no systematic bias for average
levels).  Given the relatively small dimensions of census blocks in
densely-populated areas, there is little uncertainty introduced by using
the census block centroids.  There is more uncertainty when census
blocks are larger, although there is still no bias on average.  EPA
concludes that the most appropriate locations at which to estimate
chronic exposures and risks are the census block centroids because: 1)
census blocks are the finest resolution available in the national census
data, 2) facility fencelines do not typically represent locations where
chronic exposures are likely, and 3) there is no bias introduced to
average census block levels.

Comment:  One commenter (0136) contended that the exposure modeling did
not consider the potentially significant effect of building downwash on
maximum individual risk.

Response:  The data required to account for plume downwash is very
detailed, including building heights and widths at 10-degree sectors
around each emission point at each facility.  EPA rarely has this level
of data and EPA did not have it for this risk assessment.  However,
plume downwash does not have a significant impact on long-term exposures
because such exposures are estimated at census block centroids, which
are usually located well beyond the influence of facility buildings.
Wind tunnel studies indicate that buildings "amplify" ground level
concentrations by less than a factor of 2 at receptors located at a
distance beyond six building heights [ref: Thompson, R. Building
amplification factors for sources near buildings: a wind tunnel study.
Atmospheric Environment 27A, 2313-2323].  Polar grid receptors used to
represent short-term exposures could be within this distance, although
it is unlikely.  The first ring of the polar grid in this assessment is
at a distance of 100 m.  To be less than six building heights away, the
building would have to be taller than 17 m (about 55 feet).

Comment:  One commenter (0136) argued that EPA must account for
re-suspension of pollutants or explain why re-suspension of pollutants
would not contribute to risk in areas immediately adjacent to HON
facilities.

Response:  The re-suspension of pollutants would not result in exposure
concentrations or risks higher than those estimated in the assessment.
EPA did not use the plume depletion function of the dispersion model, so
any pollutants that may be deposited and resuspended were never removed
from the plume in the first place.

Comment:  One commenter (0136) stated that EPA admits that the
variability in emissions associated with nonroutine (upset) conditions
can be significant in some cases, but exposure to upset emissions was
not modeled [Risk Assessment at p. 5-24]. The commenter (0136) stated
that this omission will significantly underestimate short-term
exposures.

Response:  We disagree that including upset emissions would have a
substantial impact on the estimates of long-term or short-term
exposures.  Upset emissions would have to be significant compared to
routine emissions, and be recurrent over long periods of time to have a
significant impact on long-term exposures.  In a Houston/Galveston area
study (ref:  Allen, D., et. al.  Variable Industrial VOC Emissions and
Their Impact on Ozone Formation in the Houston Galveston Area.
Submitted to the Texas Environmental Research Consortium. April 16,
2004), annual upset emissions are less than 15 percent of the annual
routine emissions.  Since upset emissions are no more than 15 percent of
routine emissions, upset emissions would have an imperceptible effect on
long-term exposure.

	Acute impacts were assessed and found acceptable at proposal based on
routine emissions and worst case hourly meteorological conditions.
While hourly upset emissions may exceed routine emissions (sometimes by
as much as a factor of 10) approximately a dozen times per year, actual
short-term exposures are also governed by other factors like
meteorological conditions.  The combined probability of significant
upset emissions and worst-case meteorology is low.  Upset emissions
would most likely occur during typical meteorological conditions, not
the worst conditions of a 5-year period.  Typical meteorological
conditions result in exposures that are approximately a factor of 10
lower than hourly exposures (ref: U.S. Environmental Protection Agency.
2004.  Air Toxics Risk Assessment Reference Library, Volume 2 –
Facility-Specific Assessment.  EPA-453-K-04-001B). In general, then,
upset emissions would not significantly affect our assessment of acute
exposures (although our assessment may understate short-term exposures
associated with an exceptional combination of circumstances). Therefore,
we do not expect that exposures due to upset emissions would be
significantly higher than those estimated at proposal.

Comment:  One commenter (0136) argued that there is very little
explanation of what the various reference levels actually mean and to
properly inform the public, a better summary of the differences among
the reference values is needed in the Risk Assessment. The commenter
(0136) contended the lack of mild-effects reference values for fifteen
chemicals was cited as extremely problematic, as well as EPA’s
statement that an exposure of up to 2% of a ‘severe health effects’
reference value is ‘very unlikely to pose health threats.’
Additionally, the commenter (0136) stated there was an omission of any
mention of acute risks in the proposal’s discussion of acceptable risk
and ample margin of safety. One commenter (0136) argued that EPA must
adequately address acute risks.  For the 104 HON components in the ACC
data set, there were 48 instances where the maximum 1-hour average air
concentration exceeded acute dose-response values. The commenter (0136)
disagreed with EPA’s conclusion that these exceedances were not
significant since many sites exceeded only the no-effects reference
value. The commenter (0136) pointed out that many sites exceeded the
CalEPA’s reference exposure levels as well as other reference levels,
and that for some chemicals the no-effects level is the only reference
levels available for comparison.  Further, the commenter (0136) believes
that people subjected to what EPA excused as "mild, reversible effects
still face risk and inconvenience.

Response:  EPA believes that a sufficient explanation of the various
acute reference levels is given in the risk assessment document and the
information sources referenced by it.  Most of the 48 acute reference
value exceedances were of MRL values derived by the Agency for Toxic
Substances and Disease Registry (ATSDR).  The MRL values are not
intended to define action levels for ATSDR or other agencies.  ATSDR
uses the no-observed-adverse-effect level/uncertainty factor approach to
derive MRL values for hazardous substances. They are set below levels
that, based on current information, might cause adverse health effects
in the people most sensitive to such substance-induced effects.  Because
MRL values are derived for exposures of 1 to 14 days, they are
substantially lower (i.e., more protective) than values for 1-hour
exposures. In the HON assessment, they were used mainly as a
conservative initial screen. One-hour exposures that exceeded an MRL
value simply suggested that a comparison with other acute reference
values was warranted, and EPA provided in the risk assessment document a
discussion for each of the 10 HAP associated with the 48 exceedances.
EPA concluded that the exceedances would not pose a significant risk to
health.  It should also be noted that EPA has under active development
both assessments and accompanying methodology for assessments of health
effects from acute exposures (i.e., single exposure less than 24 hr in
duration).

The MRL is the only acute dose-response value for ethylene glycol.
However, because the acute MRL for ethylene glycol is for an exposure
duration of 1 to 14 days, it is not directly relevant to the acute
assessment for the HON (1-hour exposure duration).   Considering the
difference in exposure duration, and that the MRL is a factor of 100
below the no-effect level, EPA contends that exceeding the MRL value by
a factor of 20 would not pose a significant risk to health.

There are some HAP for which there are no mild-effects reference values.
 For these HAP, EPA compared exposure concentrations to the lowest
available acute dose-response values.  For 14 of the 15 HAP, the lowest
value is one-tenth of the level determined by NIOSH to be imminently
dangerous to life and health (IDLH/10), approximately comparable to mild
effects levels for 1-hour exposures.  The highest hazard quotient for
these 14 HAP is 0.002.  One HAP, chloroacetic acid, has an AEGL-2 as the
lowest acute dose-response value.  The highest hazard quotient for this
HAP is 0.0002.  Based on these very low hazard quotients, EPA concluded
that these HAP do not pose a significant risk to health.  The 0.02
hazard quotient (2 percent) in the text of the risk assessment document
is a typographical error.  The highest hazard quotient is 0.002.

Comment:  One commenter (0136) disagreed with EPA’s conclusion that
there is no significant risk posed by the clustering of HON sources. The
commenter (0136) noted that there are very significant clusters.  The
commenter (0136) pointed out that the target category for HAP regulation
is SOCMI, including area sources and emissions of non-organic HAP, and
that the residual risk assessment must deal with risks from the whole
SOCMI source category and not just those parts that are already
regulated. The commenter (0136) maintains that if all emission points at
a facility in aggregate threaten public health or the environment, EPA
must regulate those emission points associated with the SOCMI category.

One commenter (0125) believed that when EPA is establishing controls
under the Residual Risk Program for source categories that are located
at facilities in which other source categories exist, the Agency does
not have the authority to consider risks from these categories in order
to increase the stringency of controls for the categories under
evaluation.  The commenter (0125) believed this type of evaluation is
contrary to the residual risk provisions of the Clean Air Act and
therefore should not be considered for this purpose.  Furthermore, the
commenter (0125) stated that the Agency’s resources can most
beneficially be invested not in conducting facility-wide
risk-assessments, but in assessing risks from the source category being
addressed for residual risk.  The commenter (0125) added that any
remaining risks from other source categories present at the same
facility will soon be the subject of their own investigation under the
statutory timetable.  Moreover, the commenter (0125) stated that EPA has
found these facility-wide assessments to be difficult to perform because
of the lack of adequate data on categories of sources not yet examined
for residual risk.  One commenter (0138) agreed with EPA’s decision
not to consider risks from outside the HON source category in
determining an ample margin of safety.  The commenter (0138)  believed
that consideration of collocated source categories is not permitted by
the Act and can be considered only after emission reductions from all
MACT and GACT standards have been achieved.

Response:  Our decision on considering co-located sources is discussed
in the preamble to the final Coke Ovens residual risk rulemaking.  After
examining the statutory scheme, the Benzene NESHAP, and sound policy
concerns, we concluded that, in its assessment of ‘‘acceptable
risk’’ for purposes of CAA section 112(f), the agency will only
consider the risk from emissions from that source category.  This was
the approach in the Benzene NESHAP, wherein EPA limited consideration of
acceptability of risk to the specific sources under consideration rather
than to the accumulation of  these and other sources of benzene
emissions that may occur at an entire facility.  However, we also
determined that we have the authority, in establishing ‘‘an ample
margin of safety,’’ to impose greater reductions on a particular
source category when the agency concludes that several of these
co-located sources categories have elevated the overall public health
risk to unacceptable levels.  While this evaluation could be performed
during the development of an individual residual risk standard for any
particular source category that is part of a larger facility with
multiple source categories, such an analysis would necessarily require
sufficient data regarding the total facility emissions and the costs and
risk impacts of reducing those emissions. Such information may
conceivably be available when EPA does the first residual risk rule
applicable to a facility, but it is much more likely that an early
evaluation of cross-category risks will be inconclusive due to a lack of
complete information regarding other emission points.

We maintain the risk analysis for this rule was done correctly and
consistent with the Coke Ovens residual risk rulemaking.  The clusters
of HON plants from the risk document did not show higher individual
risk.  We also note that the issue regarding our treatment of inorganic
HAP is addressed in another comment and response-.

Comment:  One commenter (0131) argued that EPA references an adjustment
factor of 1.6 to apply to carcinogenicity slope factors for genotoxic
carcinogens to account for life stage factors.  The commenter (0131)
added that while EPA did not use this factor in the HON residual risk
assessment, referencing the factor in the proposed rule implies that in
the future this factor should be considered.  The commenter (0131)
provided several reasons for not applying the 1.6 adjustment factor
including EPA has not provided sufficient scientific foundation upon
which to conclude that early-life exposure to carcinogens increases risk
and necessitates a modification to its linear default slope adjustment
factor.

Response:  In the preamble to the proposed rule, EPA discussed the
revised cancer guidelines and also the supplemental guidance that
specifically address the potential added susceptibility from early-life
exposure to carcinogens. The supplemental guidance provides guidance for
adjusting the slope of the dose-response curve by applying
‘‘age-dependent adjustment factors’’ (which translates into a
factor of 1.6 for lifetime exposures) to incorporate the potential for
increased risk due to early-life exposures to chemicals that are thought
to be carcinogenic by a mutagenic mode of action.  Some evidence
indicates that several HAP that are emitted from HON CMPUs and that
dominate the risks from this source category may be carcinogenic by a
mutagenic mode of action, although for most carcinogenic HAP EPA has not
made a formal determination of mode of action.  Because EPA does not
have sufficient scientific foundation upon which to conclude that
early-life exposure to carcinogens increases risk for the HAP emitted
from this source category, EPA did not apply age-dependent adjustment
factors to the cancer risk estimates.  However, when such information
becomes available, EPA will make adjustments to the cancer risk
estimates consistent with the Agency guidance.

Comment:  One commenter (0131) argued that EPA should not add the risks
of chemical producing different types of carcinogenicity through
different mechanisms of toxic action and stated that from a scientific
perspective adding carcinogenic risks by chemical producing different
types of carcinogenicity in different organs without consideration of
the mechanism of toxic action is questionable and suggested EPA should
only add risks for carcinogens producing cancer in the same target organ
and by a similar mechanism of action.  The commenter (0131) also applied
the same reasoning to the impacts of non-carcinogens.

Response:  EPA disagrees with the commenter that the risks of chemicals
producing different types of carcinogenicity through different
mechanisms should not be added.  EPA contends that, in assessments of
carcinogens for which there is an assumption of a linear dose-response,
the cancer risks predicted for individual chemicals may be added to
estimate cumulative cancer risk.  There may be instances where the
effects from multiple chemicals are synergistic (greater than additive)
or antagonistic (less than additive), but sufficient data to evaluate
these is lacking.

For the assessment of chronic effects other than cancer, EPA agrees that
hazard quotients for HAP should be summed by target organ, resulting in
the target-organ-specific hazard index.  However, as a screening step in
many risk assessments, EPA will sum hazard quotients without regard to
target organ, and consider target-organ-specific hazard indices only if
the screening hazard index value exceeds 1.  In the assessment of this
source category, there are no hazard indices greater than 1, so EPA
concluded that it was not necessary to consider the
target-organ-specific indices.

Comment:  One commenter (0131) argued that EPA should use consistent
health criteria from IRIS and not criteria from single states such as
California to assess risks under the HON residual risk rule

Response:  As discussed in the risk assessment report for the HON,
dose-response information for chronic exposures was used from various
sources and prioritized according to consistency with EPA risk
assessment guidelines and the level of independent review received.  The
prioritization process is aimed at incorporating the best available
science.  The risk assessment document also contains a detailed
discussion of the sources of acute dose-response information.

Comment:  One commenter (0133) contended that to the extent possible,
the EPA should quantify the risk associated with uncertainty in the data
collected and incorporate these factors into the residual risk
assessment and argued emissions inventories generally are substantially
underestimated, not overestimated.  The commenter (0133) believed that
emissions from transfer operations are much more significant than the
EPA analysis would indicate.  Additionally, the commenter (0133)
contended that engineering calculations do not account for considerable
quantities of emissions invisible to the naked eye.  Finally, the
commenter (0133) stated that the uncertainties in the EPA’s analysis
are so significant that the agency cannot conclude with any confidence
either that there is no residual risk, such that Option 1 is justified,
or that there will be no residual risk following implementation of the
minor regulatory modifications in Option 2. Two commenters (0124, 0129)
contended that the protectiveness of the current SOCMI emissions
controls is bolstered by EPA’s conservatism in deriving estimates of
potential health risks associated with current emissions.  One commenter
(0124) stated that EPA recognizes that its risk estimates are
upper-bound estimates and that human risks, while they may be higher,
are likely to be lower than estimated and could be zero.  Furthermore,
the commenter (0124) stated that EPA’s conservatism bolsters the
appropriateness of the no further action option, because even with these
many health protective assumptions and elements of conservatism, EPA is
not projecting significant cancer risks at current emissions levels, nor
is EPA projecting meaningful reductions in risk from the installation of
additional controls.

Another commenter (0134) argued that EPA must take into account the
conservative nature of its assumptions and the uncertainties in its risk
estimates.  Additionally, the commenter (0134) contended EPA used highly
conservative assumptions when estimating risks.  Given these
conservative assumptions, the commenter (0134) concluded it is likely
that these risks actually are less than 1-in-1 million already.  There
are numerous sources of uncertainties in the risk estimates some which
may introduce bias toward overestimating while others bias toward
underestimating.  EPA uses conservative assumptions for some but not
sources of uncertainty which would tend toward overestimating rather
than underestimating risk.  Without a quantitative analysis it is not
defensible to assert that such conservative estimates would overestimate
risks to the degree asserted by the commenter.

Response:  There are uncertainties associated with all levels of risk
assessment, including emissions estimation, dose-response, dispersion
modeling, and exposure assessment.  In many cases, these uncertainties
are difficult to quantify.  Regarding cancer dose-response values, EPA
acknowledges that there is uncertainty regarding extrapolation of
effects seen at high levels to those thought to occur at low levels, and
between animals and humans (in the case of animal bioassays), or between
different segments of the human population (in the case of occupational
epidemiology studies). In carrying out these extrapolations, EPA relies
upon the best scientific information available.  When data are
inadequate, assumptions are made that generally tend to overstate risk.

Regarding effects other than cancer from chronic exposures, the RfC is
an estimate of a concentration that is thought to be without appreciable
risk to humans (including sensitive subgroups). The RfC values generally
include uncertainty factors ranging from 10 to 1000.  For acute
exposures, the situation is complicated by the fact that, while EPA is
developing a methodology for developing acute RfCs, no such benchmarks
have been set.  Therefore, a variety of dose-response benchmarks that
have been developed by diverse organizations for diverse uses and for a
range of averaging times (e.g., 1-hour, 8-hour, 15 minutes) have been
relied on in this risk assessment. This lack of a consistent approach
(dictated by what information is available) adds to the uncertainty in
this analysis of acute exposures. In addition, many of the sources of
uncertainty cited above for chronic exposures uncertainty also apply to
acute exposures.

Regarding exposure, EPA acknowledges that the assumption that people may
be present at their homes for 24 hours per day over a 70-year lifetime
represents a scenario that may overestimate the actual exposures
received by people living near the facilities. Most people have daily
activities that take them to areas where exposure concentrations are
different (higher or lower than the residence location) which for
residence locations of high exposures would likely represent an
overestimate of exposure and risk.  Also people may move to new
residences periodically which will likely reduce their exposure and risk
if they are no longer in the vicinity of sources in the source category.

In dispersion modeling, there is inherent model uncertainty associated
with representing complex atmospheric processes with a series of
equations, and a thorough examination of this uncertainty is beyond the
scope of this document. However, the overall uncertainty can be
estimated through model validation exercises. A number of studies have
been conducted to examine dispersion model accuracy, and these studies
indicate that: (1) models are more reliable for estimating longer
time-averaged concentrations than for estimating short-term
concentrations at specific locations; and (2) models are reasonably
reliable in estimating the magnitude of highest concentrations occurring
sometime, somewhere within an area [reference: U.S. Environmental
Protection Agency. 40 CFR Part 51, Appendix W. Revision to the Guideline
on Air Quality Models: Adoption of a Preferred Long Range Transport
Model and Other Revisions; Final Rule. Tuesday, April 15, 2003.
Available electronically at
http://www.epa.gov/ttncaaa1/t1/meta/m25875.html] Errors in highest
estimated concentrations of ± 10 to 40 percent are typical and well
within the factor-of-two accuracy that has long been recognized for
these models.  Uncertainties associated with specific modeling options
(e.g., building downwash) are discussed in other comment responses.
There is also a separate discussion in this document on the quality of
the emissions data used and whether the data are representative of the
entire source category.

EPA concludes that the risk assessment for this source category is
sufficient to support a decision on the acceptability of risk and the
ample margin of safety.

Comment:  One commenter (0138) supported EPA’s decision to use only
inhalation exposures for this source category.  They contend that there
are limited opportunities for significant exposure to organic gases by
other pathways.

Response:  As noted by the commenter, the assessment focused on chronic
and acute inhalation exposures.  Gas phase compounds, such as volatile
organics, are the primary releases from HON facilities. They are not
transferred to other media such as soil or water to any appreciable
degree. For these gas-phase HAP, the inhalation pathway is the most
important route of exposure.  However, a screening level quantitative
multipathway assessment for human health and ecological risk was also
performed, and the lifetime cancer risk and noncancer adverse health
impacts estimated to result from multipathway exposures are well below
levels generally held to be of concern.  All the ecological hazard
quotient values are well below levels that would indicate the presence
of adverse effects.  EPA concluded that these levels would not pose
adverse environmental effects as defined in CAA section 112(a)(7).

Comment:  One commenter (0136) criticized EPA’s use of rounding and
risk nomenclature as being designed to mislead the public.  For example,
the commenter (0136) cited that multiplying the ACC data’s measure of
annual cancer incidence of 0.06 times EPA’s simple 2.3 multiplier
gives 0.14, not 0.1. The commenter (0136) also claimed that EPA’s new
approach for communicating risk numbers as 1, 10 or 100-in one million
rather than the traditional approach of using multipliers of 10-6, 10-5
and 10-4 is a deceiving rounding method to claim, for example, that
risks are at the 10-4 threshold when in fact they are greater.

Response:  Limiting the results of the risk assessment to one
significant figure is not an attempt to mislead the public, but is
instead a consequence of the data that are used to estimate risk.  That
is, if risk is calculated using data that are known to only one
significant figure, then the risk estimate should not be presented with
more than one significant figure.  For example, because RfC values have
only one significant figure, a hazard index calculated using an RfC
should not be presented as if it is known with more certainty.  Because
cancer risk estimates are calculated using dispersion modeling results
known to only one significant figure, cancer risk estimates (and
incidence) should be presented to only one significant figure.
Regarding communicating risk results in terms of "X-in-1 million," EPA
is simply using the terms used in CAA section 112(f) and believes that
the public may find it easier to understand than the scientific notation
sometimes used (e.g., 10-6).

However, EPA has reviewed the incidence reduction estimate stated in the
preamble to the proposed rule.  We estimated that under Option 2 cancer
incidence would be 0.09 cases per year (9 cancer cases every hundred
years), a reduction of one case every hundred years.  The reduction in
incidence should have been calculated using the baseline annual cancer
incidence of 0.14  instead of  0.1.  The number of cases prevented would
be 5 cases every hundred years.

Comment:  One commenter (0136) argued that EPA’s Hazard Index (HI)
cutoffs of 1.0 are unreasonable and do not adequately protect public
health.  The commenter (0136) argued that the index must be well below
1.0 to protect the public from exposures to HAP emitted from multiple
sources, including other HON sites, HON area sources, other industrial
sources, occupational exposures, and other ingestion pathways.  The
commenter (0136) cited an internal memo from 2002, where EPA determined
that the default HI limit for chronic noncancer risks should be 0.2.

Response:  While the highest HI value estimated for the HON source
category is 1, most of the HI values are well below 1.  The median HI
value is 0.2, and only 9 facilities have HI estimates higher than 0.5.
Therefore, most facilities are unlikely to exceed an HI value of 1
considering contributions from other sources.  EPA stated in the
preamble to the proposed rule that an HI value less than 1 indicates
that no adverse heath effects are expected as a result of the exposure,
but that an HI exceeding 1 does not translate to a probability that
adverse effects occur.  Rather, it suggests the possibility that adverse
health effects may occur.  Considering that RfC values include
uncertainty factors typically ranging from 10 to 1000, EPA concludes
that adverse effects are not likely to occur even near the facilities
with HI values of 1.

Regarding the internal memo referred to by the commenter, EPA has issued
no policy establishing HI limits.

Comment:  One commenter (0136) argued that EPA’s data falls short of
the guidelines supporting the Data Quality Act.

Response:  In developing the HON, we followed the procedures in
Guidelines for Ensuring and Maximizing the Quality, Objectivity,
Utility, and Integrity of Information Disseminated by the Environmental
Protection Agency (EPA/260R-02-008).  These guidelines contain EPA’s
policy and procedures for meeting the objectives of the Data Quality
Act, which are to: (1) maximize the quality, objectivity, utility, and
integrity of information disseminated by the agency, and (2) establish
administrative mechanisms allowing affected persons to seek and obtain
correction of information maintained and disseminated by the Agency.

Our Guidelines state that "influential" scientific, financial, or
statistical information (including rulemaking data) should meet a higher
degree of quality. Analytic results for influential information must
have a higher degree of transparency regarding (1) the source of the
data used, (2) the various assumptions employed, (3) the analytic
methods applied, and (4) the statistical procedures employed. The
Residual Risk Assessment presented in the docket describes in detail the
analytical methods and data used, and the default assumptions used for
missing data.  This report, along with the Residual Risk Report to
Congress (EPA-453/R-99-001) provides the necessary transparency to
inform the public of our methods and data used to conduct the risk
assessment.

The Guidelines also state for risk assessments we must inform the public
of all of the uncertainties identified in the conduct of the risk
assessment. Our Residual Risk Assessment document in the docket points
out the uncertainties and variabilities in available cancer and
noncancer dose-response values; dispersion modeling techniques; exposure
assessment; and the data on emissions, release parameters, and emission
point locations. By providing this information for public comment as
part of the rulemaking we have provided the opportunity for affected
persons to correct any erroneous information and to submit any data and
comments to improve our risk assessment.

In deciding to use the ACC emissions and source data, we conducted a
screening level risk assessment to determine if these data would
sufficiently characterize the industry.  We conducted an analysis of 226
HON facilities (96 percent of the industry) using emissions data from
the National Emissions Inventory (NEI), which contains data supplied by
the States. The level of detail of the NEI data did not allow us to
separate out just the HON process units at the sites.  Therefore, the
emissions and risk represented the impact of whole facilities, which in
some cases included additional releases of organic HAP emissions from
other processes.  The risk results showed that the highest risks using
the NEI data were on the same order of magnitude as risks estimated
using the ACC data. On this basis, we concluded that the ACC data were
the best data available for assessing industry risks, and could be used
to represent the industry as a whole. The ACC data provide greater far
detail on emission point locations and release parameters.

Based on the above considerations, we believe we have fully met the
requirements of the DQA.  While the data is not perfect, we concluded it
is of the right type and sufficient quality to the mandate for
conducting a residual risk assessment under CAA section 112(f).

Comment:  Two commenters (0136, 0139) contended that EPA has not
adequately justified that the ACC data are representative of the
industry as a whole or that the sources covered are representative of
the maximum risk or even typical risk. One commenter (0136) argued that
to adequately perform its function under CAA section 112(f) EPA must be
able to accurately identify the risk associated with the most exposed
individual, and must be able to accurately estimate risk more generally
from sources within the source category. To do this requires sufficient
data regarding all of the important factors for estimating risk
(including size, quantity of emissions, the specific characteristics of
emission points, proximity and population density of surrounding
communities, important meteorological and topological data, co-located
emission sources, ambient background levels, etc.).  Two commenters
(0136, 0139) objected to EPA’s use of a simple 2.3 multiplying factor
to adjust for the limited number of sources covered by the ACC data,
because this approach unreasonably assumes constant population density
rather than considering readily available population data available from
the Census Bureau. Moreover, the 50-km radius assumption may also bias
the results.  Finally, the commenter (0136) contended that EPA attempts
to adjust for the age of the ACC data by arbitrarily assuming with no
supporting data that the synthetic organic chemical manufacturing
industry has not grown in seven years.  The commenter (0136) argued that
EPA provides no description of the methods used to compare the ACC data
to NEI data and provided inadequate analytic support for its conclusion
that the ACC data are representative of risks posed by the industry as a
whole.  The commenter (0136) argued that EPA has not taken reasonable
steps to address the sources of measurement uncertainty in the ACC data.
 The commenter stated that EPA does not even know how the 104 reporting
facilities measured emissions but rather EPA "assumed that emissions
were estimated using established methodologies . . . .".  The
established semi-empirical methodologies have extremely high
uncertainty, which was improperly ignored in the Risk Assessment,
acceptable risk determination, and ample margin of safety decision
steps.  Additionally, one commenter (0139) stated that 50 percent of the
data are from facilities in Texas and Louisiana and that the data may
not be geographically representative.  Two commenters (0125, 0128)