[Federal Register: February 16, 2006 (Volume 71, Number 32)]
[Rules and Regulations]
[Page 8341-8387]
[DOCID:fr16fe06-10]

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Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Plywood and
Composite Wood Products; List of Hazardous Air Pollutants, Lesser
Quantity Designations, Source Category List; Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[OAR-2003-0048; FRL-8028-9]
RIN 2060-AN05

National Emission Standards for Hazardous Air Pollutants: Plywood
and Composite Wood Products; List of Hazardous Air Pollutants, Lesser
Quantity Designations, Source Category List

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule, amendments; notice of final action on
reconsideration.

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SUMMARY: On July 30, 2004, EPA promulgated national emission standards
for hazardous air pollutants (NESHAP) for the plywood and composite
wood products (PCWP) source category. The Administrator subsequently
received a petition for reconsideration of certain provisions in the
final rule. In addition, following promulgation, stakeholders expressed
concern with some of the final rule requirements including definitions,
the emissions testing procedures required for facilities demonstrating
eligibility for the low-risk subcategory, stack height calculations to
be used in low-risk subcategory eligibility demonstrations, and
permitting and timing issues associated with the low-risk subcategory
eligibility demonstrations. In two separate Federal Register notices
published on July 29, 2005, we announced our reconsideration of certain
aspects of the final rule, and we proposed amendments to the final
rule. In the notice of reconsideration, we requested public comment on
the approach used to establish and delist a low-risk subcategory of
PCWP affected sources, as outlined in the final rule, and on an issue
related to the final rule's startup, shutdown, and malfunction (SSM)
provisions. In the proposed amendments notice, we proposed simplifying
the requirements for the low-risk demonstrations (LRD) and allowing
additional time for facilities to submit them. We also requested
comment on whether to extend the MACT compliance date. We also
clarified some common applicability questions. In this action, we are
promulgating amendments to the PCWP NESHAP and providing our
conclusions following the reconsideration process.

DATES: February 16, 2006. The incorporation by reference of one
publication listed in this final action is approved by the Director of
the Office of the Federal Register as of February 16, 2006.

ADDRESSES: Docket. The EPA has established a docket for this action
under Docket ID No. OAR-2003-0048 and Legacy Docket ID No. A-98-44. All
documents in the docket are listed on the http://www.regulations.gov Web site.

Although listed in the index, some information is not publicly
available, e.g., confidential business information (CBI) or other
information whose disclosure is restricted by statute. Certain other
material, such as copyrighted material, is not placed on the Internet
and will be publicly available only in hard copy form. Publicly
available docket materials are available either electronically through
http://www.regulations.gov or in hard copy at the Air and Radiation Docket and

Information Center, EPA/DC, EPA West, Room B102, 1301 Constitution
Ave., NW, Washington, DC. The Public Reading Room is open from 8:30
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The
telephone number for the Public Reading Room is<PHONE_NUMBER>, and the
telephone number for the Air and Radiation Docket and Information
Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For information concerning
applicability and rule determinations, contact your State or local
representative or appropriate EPA Regional Office representative. For
information concerning rule development, contact Ms. Mary Tom Kissell,
Sector Policies and Program Division, (Mailcode: C439-03), EPA,
Research Triangle Park, NC 27711; telephone number:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; e-mail address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Regulated Entities

    Categories and entities potentially affected by today's action
include:

------------------------------------------------------------------------
                               SIC code    NAICS         Examples of
          Category                a        code b    regulated entities
------------------------------------------------------------------------
Industry....................       2421     321999  Sawmills with lumber
                                                     kilns.
                                   2435     321211  Hardwood plywood and
                                                     veneer plants.
                                   2436     321212  Softwood plywood and
                                                     veneer plants.
                                   2493     321219  Reconstituted wood
                                                     products plants
                                                     (particleboard,
                                                     medium density
                                                     fiberboard,
                                                     hardboard,
                                                     fiberboard, and
                                                     oriented
                                                     strandboard
                                                     plants).
                                   2439     321213  Structural wood
                                                     members, not
                                                     elsewhere
                                                     classified
                                                     (engineered wood
                                                     products plants).
------------------------------------------------------------------------
 a Standard Industrial Classification.
 b North American Industrial Classification System.

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by today's
action. To determine whether your facility is affected by today's
action, you should examine the applicability criteria in Sec.  63.2231
of the final rule. If you have questions regarding the applicability of
today's action to a particular entity, consult Ms. Mary Tom Kissell
listed in the preceding FOR FURTHER INFORMATION CONTACT section.

Worldwide Web (WWW)

    In addition to being available in the docket, an electronic copy of
today's action also will be available on the Worldwide Web (WWW)
through EPA's Technology Transfer Network (TTN). Following the
Administrator's signature, a copy of this action will be posted on the
TTN's policy and guidance page for newly promulgated rules at http://www.epa.gov/ttn/oarpg.
 The TTN provides information and technology

exchange in various areas of air pollution control.

Judicial Review

    Under section 307(b)(1) of the CAA, judicial review of the final
rule amendments to the NESHAP is available by filing a petition for
review in the U.S. Court of Appeals for the District of Columbia
Circuit by April 17, 2006. Under section 307(d)(7)(B) of the CAA, only
those objections that were raised with reasonable specificity during
the period for public comment may be raised during judicial review.
Under section 307(b)(2) of the CAA, the requirements that are the
subject of the

final rule amendments may not be challenged later in civil or criminal
proceedings brought by EPA to enforce the requirements.

Outline

    The information presented in this preamble is organized as follows:

I. Background
II. Comments and Responses on Low-risk Option
    A. Legal Basis
    B. Background Pollution and Co-located Emission Sources
    C. Ecological Risk
    D. The Dose-Response Value Used for Formaldehyde
    E. Appendix B to 40 CFR Part 63 Subpart DDDD Requirements
    F. Selection of Process Units and Emissions Determination
Procedures in Table 2A to Appendix B to 40 CFR Part 63 Subpart DDDD
    G. Emission Testing Requirements in Appendix B to 40 CFR Part 63
Subpart DDDD
    H. Compliance Date for Existing Sources
    I. Low-Risk Demonstration Submittal Dates for Existing Sources
    J. Compliance Date for Affected Sources Previously Qualifying
For the Low-Risk Subcategory
    K. Low-Risk Demonstration Submittal Dates for New Sources
    L. Legal Issues With Title V Implementation Mechanism
    M. Timing of Title V Permit Revisions
    N. Permit Conditions
    O. Costs and Benefits of Establishing a Low-Risk Subcategory
III. Responses to Comments on the Proposed Amendments and
Clarifications for Subpart DDDD
    A. Definitions
    B. Applicability of the PCWP Rule to Lumber Kilns Drying Utility
Poles
    C. Capture Efficiency Determination
    D. Incorporation by Reference of NCASI Method ISS/FP-A105.01
IV. Responses to Comments on SSM Issues
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Congressional Review Act

I. Background

    We proposed NESHAP for the PCWP source category on January 9, 2003
(68 FR 1276). The preamble for the proposed rule requested comment on
how and whether we should incorporate risk-based approaches into the
final rule to avoid imposition of regulatory controls on facilities
that pose little risk to public health and the environment. Fifty-seven
interested parties submitted comments on the proposed rule during the
comment period. The final rule (subpart DDDD in 40 CFR part 63) was
published on July 30, 2004 (69 FR 45944) after consideration of these
comments. We adopted a risk-based approach in the final rule by
establishing and delisting a low-risk subcategory of PCWP affected
sources based on our authority under section 112(c)(1) and (9) of the
Clean Air Act (CAA). Under this approach, PCWP affected sources may
submit for EPA approval proposed demonstrations that they meet certain
risk-based criteria and, therefore, are eligible to join the low-risk
subcategory and avoid applicability of the PCWP NESHAP. The methodology
and criteria for PCWP affected sources to use in demonstrating that
they are part of the delisted low-risk subcategory were promulgated in
appendix B to subpart DDDD of 40 CFR part 63. Sources whose LRD EPA
approves then must seek permit revisions under title V of the CAA that
incorporate their low-risk parameters as enforceable terms and
conditions in order to ensure they remain low-risk and remain exempt
from otherwise applicable PCWP NESHAP requirements.
    Following promulgation of the final PCWP rule, the Administrator
received a petition for reconsideration filed by the Natural Resources
Defense Council (NRDC) and Environmental Integrity Project (EIP)
pursuant to section 307(d)(7)(B) of the CAA.\1\ The petition requested
reconsideration of nine aspects of the final rule: (1) Risk assessment
methodology, (2) background pollution and co-located emission sources,
(3) dose-response value used for formaldehyde, (4) costs and benefits
of the low-risk subcategory, (5) ecological risk, (6) legal basis for
the risk-based approach, (7) maximum achievable control technology
(MACT) compliance date for affected sources previously qualifying for
the low-risk subcategory, (8) SSM provisions, and (9) title V
implementation mechanism for the risk-based approach. The petitioners
stated that reconsideration of the above issues is appropriate because
they claimed that the issues could not have been practicably raised
during the public comment period. The petition for reconsideration also
requested a stay of the effectiveness of the risk-based provisions.
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    \1\ In addition to the petition for reconsideration, four
petitions for judicial review of the final PCWP rule were filed with
the U.S. Court of Appeals for the District of Columbia by NRDC and
Sierra Club (No. 04-1323, D.C. Cir.), EIP (No. 04-1235, D.C. Cir.),
Louisiana-Pacific Corporation (No. 04-1328, D.C. Cir.), and Norbord
Incorporated (No. 04-1329, D.C. Cir.). The four cases have been
consolidated. In addition, the following parties have filed as
interveners: American Forest and Paper Association (AF&PA), Hood
Industries, Scotch Plywood, Coastal Lumber Company, Composite Panel
Association, APA-The Engineered Wood Association, American Furniture
Manufacturers Association, NRDC, Sierra Club, and EIP. Finally, the
Formaldehyde Council, Inc. and the State and Territorial Air
Pollution Program Administrators and Association of Local Air
Pollution Control Officials (STAPPA/ALAPCO) are participating in the
litigation as amicus curiae.
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    In a letter dated December 6, 2004, EPA granted NRDC's and EIP's
petition for reconsideration and declined the petitioners' request that
we take action to stay the effectiveness of the risk-based provisions.
On July 29, 2005 (70 FR 44012), we published a notice of
reconsideration to initiate rulemaking by requesting comments on the
issues in the petition for reconsideration, including the full content
of appendix B to subpart DDDD.
    In a separate notice published on July 29, 2005 (70 FR 44012), we
proposed amendments to subpart DDDD and both of the appendices to
subpart DDDD. We proposed amendments to appendix B to subpart DDDD to
reduce the number of emissions tests required while ensuring that
emissions from all PCWP process units at the relevant source are
considered when demonstrating eligibility for the low-risk subcategory.
For emission points that would still require emission tests, we
proposed that the emissions tests may be conducted after the LRD is
submitted. We also proposed that physical changes necessary to achieve
low-risk status may be completed after the LRD is submitted. We
proposed to alter the way the stack height is calculated for a look-up
table analysis and to clarify some timing issues related to LRD,
including the deadline for submitting LRD. We also requested comment on
whether the MACT compliance date should be extended for sources
submitting LRD or for all sources. Furthermore, we proposed to amend
subpart A to 40 CFR part 63, subpart DDDD of 40 CFR part 63, and
appendix B to subpart DDDD to allow use of a new test method developed
by the National Council of the Paper Industry for Air and Stream
Improvement (NCASI) for measuring hazardous air pollutants (HAP).
    For 40 CFR part 63, subpart DDDD, we proposed several changes to
ensure that the rule is implemented as intended: (1) Amend the sampling
location for coupled control devices, (2) amend language to clarify
rule

applicability during unscheduled startups and shutdowns, (3) add
language to clarify rule applicability for affected sources with no
process units subject to compliance options or work practice
requirements, and (4) amend selected definitions. A minor numbering
error was proposed to be corrected in appendix A to 40 CFR part 63,
subpart DDDD. We also clarified some common applicability questions,
and we requested comments on whether to extend the deadline for
compliance with the rule's requirements for all subject sources.
    We received public comments from nine stakeholders on the
reconsideration issues during the comment period. Although some
commenters on the 2005 reconsideration referred to previous comments
they submitted following the 2003 proposal, we have not included the
previous comments in the summary presented here unless they are
directly relevant to the reconsideration. However, the previous
comments are included in the docket for this final rulemaking or the
background information document (BID). Our responses to comments today
are intended to respond to the comments specifically submitted on our
proposed reconsideration notice and to any relevant incorporated
comments. We received public comments from 12 stakeholders on the
proposed amendments during the comment period. We received supporting
comments only (or no comments) on a number of the proposed amendments,
including the proposed amendment to the: (1) Sampling location for
coupled control devices; (2) definitions of ``molded particleboard,''
``plywood and composite wood products manufacturing facility,'' and
``plywood''; (3) requirements for affected sources with no process
units subject to the compliance options or work practice requirements;
(4) numbering of paragraphs referenced in 40 CFR 63.2269; (5) test
methods for benzene; (6) criteria for assuming zero for Method 29 non-
detect measurements; and (7) numbering of appendix A to 40 CFR part 63,
subpart DDDD. We have promulgated these amendments as proposed based on
the rationale provided in the proposed rule (70 FR 44012, July 29,
2005), and no further discussion of these amendments is presented here.
We are also promulgating a revised compliance deadline for sources
subject to the rule, which is one year later than the date originally
promulgated. The new compliance deadline is October 1, 2008. Our
rationale for this revision is contained in our responses below.

II. Comments and Responses on Low-risk Option

A. Legal Basis

    Comment: Several commenters stated that there are numerous ways in
which the risk-based exemptions contravene the language, structure, and
history of the 1990 CAA amendments and EPA's past policies. The
commenters noted that technology-based standards should precede risk-
based standards, that creating a subcategory based on risk is illegal,
that delaying the compliance date to allow the risk-based standards is
contrary to the CAA, that not setting emission standards is generally
not authorized, that considering sources in the low-risk subcategory
when establishing MACT floors is not allowed by the CAA, and that the
CAA does not authorize EPA to delist subcategories (versus categories)
of sources of carcinogenic emissions.
    Other commenters stated there is ample legal basis for establishing
and delisting the low-risk PCWP subcategory and supported retaining the
low-risk option.
    Response: After considering the 2003 proposed PCWP NESHAP and the
public comments submitted thereon, the 2004 final PCWP NESHAP, the
petition for reconsideration of the final PCWP NESHAP, the 2005 notice
of final PCWP NESHAP reconsideration and the comments submitted in
response to that notice, EPA stands by the legal rationale for the PCWP
low-risk approach explained in the 2004 final PCWP NESHAP (69 FR 45983-
45991, July 30, 2004) and incorporates that rationale by reference.
    Regarding the comments on the proposed reconsideration that raised
new points or elaborated on points previously made, the explanation for
why risk may be an appropriate criterion for distinguishing between
sources in establishing source categories and subcategories has been
clearly set forth in the general policy rationale for the final PCWP
NESHAP and today's final action on reconsideration. CAA section
112(c)(9) shows that Congress intended that EPA be able, either in
advance of or following the promulgation of emission standards under
section 112, to remove source categories and subcategories from
regulation under section 112 ``whenever'' relevant risk-based findings
are made.
    We disagree that the risk-based approach causes a delay in the
compliance date for MACT in contravention of section 112(d)(1) and
112(i). This is because the PCWP sources that remain in the MACT
category must meet emission standards by the promulgated MACT deadline,
and any sources that wish to join the low-risk subcategory and avoid
MACT at the compliance deadline must, on that date, either comply with
MACT or have been approved as a member of the low-risk subcategory.
While we have in today's final rule revised the MACT compliance
deadline to fall one year later than was originally promulgated, this
revision is not a result of the mere inclusion of the action we have
taken under section 112(c)(9). Rather, it is a result of the
significance of the changes we have made to the PCWP NESHAP overall, as
well as changed expectations about the scope of MACT-subject and would-
be low-risk sources who will need to obtain, install, and certify
emissions controls. It is also true that a source that is low-risk and
exempt from MACT at the compliance date may later undergo changes that
subject it to MACT for the first time, and that the PCWP rule in some
cases allows such a source to comply with MACT 3 years after it has
lost its low-risk status. This is consistent, however, with how we
treat area sources that change status to major sources and thereby join
a MACT-regulated category for the first time.
    We also disagree that once EPA lists a category or subcategory, it
is absolutely required by section 112(c)(2) and 112(d)(1) to set
emission standards for that category or subcategory. Section 112(c)(9)
itself depends upon the identification of a ``category'' or
``subcategory'' as identifying the set of major sources that may be
deleted from the list of sources to be regulated, and indeed by its
terms assumes that the category or subcategory may be ``on the list''
(and possibly already regulated) before EPA determines that the risk-
based criteria to justify its removal have been met.
    As we previously explained in the 2004 final PCWP NESHAP, the
approach we have taken for the low-risk PCWP subcategory is not the
source-by-source granting of risk-based exemptions rejected by Congress
in the 1990 CAA amendments. That approach would have allowed any
source, in any source category, to seek an exemption from section 112
standards, without demonstrating that it qualified under previously
established criteria to join an already existent delisted subcategory,
and without subsequent compliance responsibilities such as having to
incorporate its parameters reflecting low-risk eligibility into
federally enforceable permit terms and

conditions. The PCWP approach, instead, operates more like the
applicability determination process that a source uses to discover
which set of multiple sets of applicable requirements under the CAA it
must comply with. If a PCWP source is not low-risk, it must meet MACT;
but if it meets the low-risk criteria, it must still meet specific,
enforceable requirements that can be enforced through the title V
permit to the same extent as otherwise applicable MACT standards. Our
approach is not the same as the rejected ``de minimis'' exemption since
sources must specifically show that they meet the statutory criteria of
section 112(c)(9) that define the low-risk PCWP source category,
criteria that are explicitly enumerated in the statutory language
itself, rather than based on a legal doctrine allowing exemptions from
statutory requirements notwithstanding the absence of express statutory
language for such exemption.
    We are surprised by the commenter's assertion that our MACT floors
for non-low-risk PCWP sources may not be based, in part, on emissions
limitation achieved by sources that subsequently show they are eligible
for inclusion in the low-risk PCWP subcategory. When we develop MACT
standards, we necessarily start at a step where we do not already know
what the scope of the final standards' requirements will ultimately be.
In identifying the MACT floors for new and existing sources under
section 112(d)(2) and 112(d)(3), it is simply not possible to know with
certainty exactly which sources will have to meet MACT requirements. In
fact, it is always possible that any major source will change its
emissions or operations prior to the compliance date such that it is no
longer major and, therefore, not subject to the final standards. In the
case of PCWP, our approach presumes that nearly all sources are in the
MACT category at the outset and that sources may join the non-MACT
subcategory over time, but it would be impossible at the MACT floor
determination stage to estimate the ultimate population of low-risk
sources, just as it is impossible to estimate the number of major
sources that may become ``area'' sources before the MACT compliance
dates. In both cases, it would not be administratively feasible--nor is
it legally required--to adjust the MACT floor determination over time
as the MACT category population changes. There is no indication in the
CAA that such an approach, especially to the extent it excluded better-
performing sources from floor determinations and thereby weakened
technology-based standards, would be consistent with Congress's overall
purpose in basing section 112(d) standards on the emissions levels
achieved in practice by the best-performing sources.
    Regarding the issue of whether EPA may delist only ``categories''
of sources that emit carcinogens, but not ``subcategories,'' EPA agrees
with the commenters that suggest there is functionally no difference
between the two terms, and that it is unnecessary to resolve the debate
over whether Congress committed a ``scrivener's error'' raised by other
commenters. In section 112(c), Congress provides EPA with broad
discretion in not only defining the criteria to be used to identify
individual categories and subcategories, but in deciding when one group
of sources might constitute a ``category'' versus a ``subcategory,''
there is literally no statutory definition of either term, and the use
of one over the other to define a group of sources is merely a semantic
distinction with no legal difference.
    Regarding the commenter's objections to EPA's discussion regarding
congressional intent related to our authority to establish and delist
source categories and subcategories, we conclude that it is not
necessary, or even possible, to resolve the debate over what Congress
may or may not have silently intended, given the clear statutory
language in section 112(c)(1) and 112(c)(9). The plain language of
section 112(c)(1) explicitly states that nothing in that subsection ``*
* * limits the Administrator's authority to establish subcategories
under this section, as appropriate[,] * * *'' and given that Congress
created express authority to delist categories and subcategories under
section 112(c)(9) when the specified risk-based criteria are satisfied,
it is clearly appropriate for EPA to establish categories and
subcategories in a way that best enables the use of the authority
provided by section 112(c)(9) when the agency identifies source groups
that demonstrate they present no risks above the enumerated criteria.
Any other interpretation of the statutory language would unnecessarily
restrict the broad discretion that the CAA provides for this purpose.
We, therefore, agree with the commenters who stated that section 112,
especially when taken as a whole, provides ample authority for EPA's
risk-based approach in the 2004 final PCWP NESHAP.
    Comment: Two commenters stated that section 112(d) of the CAA
clearly establishes a two-step process for addressing HAP emissions
through the MACT and residual risk provisions and that the risk-based
exemptions contained in the PCWP MACT are contrary to the CAA.
    One commenter stated that risk-based exemptions are contrary to the
concept of the ``level-playing field'' that should result from the
proper implementation of technology-based MACT standards. The commenter
also noted that the National Air Toxics Assessment (NATA) information
shows the need for a nationwide technology-based approach and indicates
that HAP exposure is very high throughout the entire country in both
densely populated urban areas and remote rural locations.
    Response: We disagree that inclusion of a low-risk subcategory in
the final PCWP rule is contrary to the 1990 CAA Amendments. The PCWP
MACT are technology-based standards developed using the procedures
dictated by section 112 of the CAA. The only difference between the
final PCWP rule and other MACT rules is that we used our discretion
under CAA section 112(c)(1) and 112(c)(9) to subcategorize and delist
low-risk affected sources, in addition to fulfilling our duties under
CAA section 112(d) to set MACT. It is clear from the statutory language
that, once EPA has listed a source category under section 112(c)(1), it
is then faced with the decision whether to regulate the source category
under section 112(d) or to delist it under section 112(c)(9). In light
of the authority provided by section 112(c)(9), it is unreasonable to
assert that once a category is listed it must in all cases be regulated
under section 112(d)(1), since the result of a delisting under section
112(c)(9) is that the source category is exempt from section 112
regulation. Moreover, nothing in the statutory language suggests that
this authority to implement section 112(c)(9) is limited by what effect
such action may have on competition within a specific industry. Rather,
section 112(c)(9) of the CAA requires that categories or subcategories
meet specific risk criteria in order to be delisted, and to determine
this, risk analyses may be used. We disagree with the commenter that we
must wait for implementation of CAA section 112(f) before utilizing
risk analysis in this manner, since nothing in section 112(c)(9)
suggests that its authority may not be used until after application of
technology-based standards under section 112(d). The 2004 final PCWP
NESHAP are particularly well-suited for a risk-based option because of
the specific HAP that are emitted by PCWP sources. For many affected
sources, the HAP are emitted in amounts that pose little risk to the
surrounding population. However, the cost of controlling these HAP is
high

and may not be justified by environmental benefits for these low-risk
affected sources. Only those PCWP affected sources that demonstrate
that they are low-risk are eligible for inclusion in the delisted low-
risk subcategory. The criteria included in the 2004 final PCWP NESHAP,
as amended by today's final rulemaking, defining the delisted low-risk
subcategory are based on sufficient information to develop health-
protective estimates of risk and will protect human health and the
environment.
    We agree that one of the primary goals of developing a uniform
national air toxics program under CAA section 112 of the 1990 CAA
amendments is to establish a ``level playing field,'' where
appropriate. We do not agree, however, that this goal limits our
broader authority under section 112(c)(1) and (9), and we do not feel
that defining a low-risk subcategory in the PCWP NESHAP does anything
to remove the level playing field for PCWP facilities. The PCWP NESHAP
and its criteria for demonstrating eligibility for the delisted low-
risk subcategory apply uniformly to all PCWP facilities across the
nation. The PCWP NESHAP establishes a baseline level of emission
reduction or a baseline level of risk (for the low-risk subcategory).
All PCWP affected sources are subject to these same baseline levels,
and all facilities have the same opportunity to demonstrate that they
are part of the delisted low-risk subcategory. Therefore, concerns
regarding facilities moving to areas of the country with air toxics
programs that are less-stringent than today's PCWP NESHAP should be
alleviated.
    Although NATA may show measurable concentrations of toxic air
pollution across the country, these data do not suggest that PCWP
facilities that do not contribute to the high exposures and risk should
be included in MACT regulations, notwithstanding our authority under
CAA section 112(c)(9). Our decisions regarding whether a source has
demonstrated its eligibility for inclusion in the low-risk delisted
subcategory will be based on whether the risks from that particular
source, as proven by its specific facts, are within our pre-established
criteria that are based on the statutory levels defining when a source
category or subcategory may be delisted.

B. Background Pollution and Co-Located Emission Sources

    Comment: One commenter stated that many of the HAP emitted from
PCWP facilities are found ubiquitously in U.S. ambient air and,
therefore, a risk assessment methodology that ignores background
pollution (including co-located sources) underprotects. The commenter
noted that the 2003 proposal notice recognized that simply ensuring
that the risks caused by PCWP sources themselves were below a hazard
index (HI) of one (without accounting for other sources of exposure)
would be underprotective. However, in the final PCWP NESHAP, EPA
decided to use an HI of 1.0, but did not require sources to account for
background pollution or emissions from co-located sources, thus failing
to ensure that sources are truly low-risk. Two other commenters noted
that the final PCWP NESHAP limits the analysis of risk to the impact of
selected emissions units, but the major-source status of a source is
based on facilitywide emissions.
    Other commenters argued that EPA correctly refrained from
considering risks from background ambient HAP concentrations and from
co-located sources. One commenter also noted that EPA selected a very
conservative HI of 1.0, which builds in a margin of safety in the event
that exposure to background sources of HAP increases the risk to public
health. Therefore, EPA has in a way accounted for background and co-
located source emissions in formulating the low-risk subcategory. The
commenter added that CAA section 112(d) and 112(c)(9) address source
categories established pursuant to CAA section 112(c)(1) without regard
to background or co-located sources outside the source category.
    Another commenter added that CAA section 112(c)(9)(B) delisting
criteria pertaining to both threshold and non-threshold HAP are focused
solely on exposures attributed to the affected source in question. The
commenter believes the statutory criterion in CAA section
112(c)(9)(B)(i) is clearly defined (one in a million cancer risk) and
is to be evaluated solely with reference to the emissions from affected
sources, not background concentrations. The commenter believes that
``ample margin of safety'' delisting criterion for threshold HAP in CAA
section 112(c)(9)(B)(ii) is more than adequately achieved by the
combined conservatism of the dose/response assessment (inherent in the
derivation of the reference concentration (RfC) or other inhalation
benchmark) and the exposure assessment (inherent in the dispersion
modeling methodology and the assumption of continuous exposure to the
maximum average annual emissions for the duration of a lifetime).
    Response: We do not believe that it is necessary or appropriate to
consider background HAP concentrations or HAP emissions from co-located
sources in implementing our authority to delist the low-risk PCWP
subcategory. After reviewing the comments and reconsidering the
relevant sections of the CAA, we agree with the commenters who argued
that section 112(c)(9) decisions may be based on risk assessments that
focus on the emissions from the affected source and are not required to
consider co-located source emissions or background concentrations. The
residual risk program may consider, as appropriate, risks from co-
located source emissions and risks from total emissions from a
particular location. This approach is reiterated in the recently
finalized Coke Oven Batteries Residual Risk rule 70 FR 19991 (April 15,
2005), where we said we will only consider emissions from the regulated
source category when determining acceptable risk during the first step
of the residual risk analysis. However, during the second step, where
we determine the ample margin of safety considering costs and technical
feasibility (70 FR 19997-98), we may consider co-located sources and
background levels where appropriate. Additionally, the national
strategy for area sources will address emissions from multiple sources
in urban areas.
    Comment: One commenter contended that the authors of the MACT and
delisting provisions at issue made clear that they intended all co-
located sources of HAP to be included when EPA made risk-based
decisions. The commenter provided examples of legislative history of
the 1990 CAA amendments which the commenter believes explains
Congressional intent in crafting section 112(c)(9).
    Another commenter contended that Congress intended EPA to focus
only on the source in question, and provided examples from the
legislative history of CAA section 112(d)(4), which according to the
commenter is an analogous provision. The commenter argued that Congress
was clear when it intended for EPA to consider background
concentrations and contributions from all sources. The commenter
provided examples from the CAA and judicial precedent.
    Response: While we believe that under section 112(f) we may
consider, as appropriate, co-located source and background emissions
when conducting residual risk reviews, after reviewing the comments and
the different statutory language in section 112(c)(9), we do not
believe it is necessary or appropriate to consider emissions except
those from the affected source category or subcategory at issue. This
is because the specific language of section 112(c)(9), compared to that
in section

112(f), indicates that the focus of a delisting action should be on the
risks presented by the emissions from the affected source category or
subcategory itself, rather than from other sources.
    The criteria for a delisting decision regarding a source category
that emits carcinogens are discussed in section 112(c)(9)(B)(i) in a
way that suggests EPA is to start its analysis by first identifying the
sources ``in'' (i.e., the process units that make up the affected
source) the source category, and determine whether HAP ``emitted by''
such affected sources ``in'' the category exceed quantities that cause
a lifetime cancer risk greater than one-in-one million to the
individual who is most exposed to emissions of ``such pollutants from
the source[.]'' This focus on emissions from sources that are actually
within the source category as being the scope of HAP concentrations
that must not exceed the enumerated cancer risk benchmark would be
frustrated by an analysis that imports HAP emissions from other sources
not in the source category, or that includes background HAP
concentrations that may not be attributable to any source at all.
    Similarly, section 112(c)(9)(B)(ii) provides that for non-
carcinogen HAP, EPA is to assess whether emissions ``from no source in
the category or subcategory'' exceed a level adequate to protect public
health and whether emissions ``from any source'' in the subject
category or subcategory will cause an adverse environmental effect.
Again, the statutory language focuses on the emissions that are
attributable to sources within the source category or subcategory under
review, and does not direct EPA to extend its analysis to either
emissions from other sources in other categories or subcategories or to
non-attributable background concentrations.
    Contrast this with the language of section 112(f)(2)(A), which,
initially, directs EPA to determine whether further risk-based
standards are required in order to provide an ample margin of safety to
protect public health to prevent an adverse environmental effect,
without specific reference as in section 112(c)(9)(B)(i) and (ii) to
the emissions from sources within the source category in question. This
difference alone suggests that EPA may take a broader look in assessing
risks under section 112(f) than is required under section 112(c)(9).
Moreover, in establishing the trigger for when EPA is required to adopt
residual risk standards, section 112(f)(2)(A) focuses on the lifetime
excess cancer risk to the individual most exposed to emissions from
sources in the subject category or subcategory, but does not, like in
section 112(c)(9)(B)(i), clearly indicate that the excess cancer risk
is to be that caused only from the emissions from the sources within
the subject source category. Rather, under the language of section
112(f)(2), EPA may consider the cancer risk experienced by the most
exposed individual, whatever the source or sources of that risk may be,
and then regulate if the subject source category contributes to that
risk. A similar analysis applies to section 112(f)(2)(A)'s directive to
assess whether further standards are necessary to prevent an adverse
environmental effect, which, unlike the language in section
112(c)(9)(B)(ii), does not specifically state that such effect must be
caused by emissions from the sources in the subject source category.
Finally, the language in section 112(f)(2)(A) that establishes the
threshold of protection residual risk standards must achieve also does
not explicitly limit EPA's authority to focusing only on the emissions
from the affected sources in the subject category.
    Therefore, while both section 112(f)(2) and 112(c)(9) use the
phrase ``ample margin of safety'' to define the triggers for action
and/or the benchmark that must be met in action, the differences in
additional contextual language in the two subsections makes it
reasonable to interpret section 112(c)(9) as allowing a more narrowly
focused risk assessment for source category and subcategory delistings
than the agency has stated it intends to pursue in residual risk, in
which we have asserted the ability to evaluate ``other relevant
factors'' beyond those presented by the affected source (70 FR 19998).
    Comment: One commenter stated that if the final PCWP rule
incorporates risk-based exemptions, sources included in the low-risk
subcategory should not be exempted from consideration during the
residual risk process. Other commenters argued that EPA does not have
authority to consider facilitywide or background emissions in residual
risk determinations.
    Response: We disagree that we do not have the authority to include
the entire facility in our residual risk analyses. In the preamble to
the coke ovens residual risk rule, we reiterated our discretion to
include, as appropriate, emissions from outside the source category
during the ample margin of safety determination. The emissions
evaluated during this ample margin of safety determination can include
those from PCWP sources that are part of the low-risk subcategory.

C. Ecological Risk

    Comment: Two commenters stated that the risk-based exemptions in
the PCWP rule do not address ecological risks that may result from
uncontrolled HAP emissions. One of the commenters believes that EPA's
ecological assessment for the final rule is fundamentally inadequate.
The commenter believes EPA failed to meet the legal requirement in the
CAA in several obvious ways: (1) The assessment focused on just a few
HAP and thus ignored potential environmental impacts from other
emissions; (2) by evaluating a single location, the assessment ignored
potential site-specific environmental receptors and locally affected
species; and (3) the consideration of only persistent and
bioaccumulative HAP would not capture potential acute effects on the
environment.
    To the contrary, one commenter believes that EPA properly evaluated
ecological risks. The commenter referred to their study of ecological
risks which the commenter believes concurs with EPA's findings that no
potential adverse risk to ecological resources is likely based on the
available data.
    Response: To determine whether low-risk PCWP sources are likely to
cause adverse environmental effects due to HAP emissions, EPA performed
a screening assessment of ecological risks from these sources. The
ecological assessment focused on HAP that are emitted by PCWP
facilities and that have the potential to persist in the environment
and bioaccumulate. The list of persistent and bioaccumulative HAP (PB
HAP) is described in EPA's Air Toxics Risk Assessment (ATRA) Reference
Library (http://www.epa.gov/ttn/fera/risk_atra_main.html). We did not

evaluate inhalation risks of non-PB HAP to ecological receptors
explicitly. Rather, we assert that the acute and chronic dose-response
values for human inhalation exposure, which will be used by PCWP
facilities to demonstrate their low-risk status, are protective of
inhalation exposures that may be experienced by many terrestrial
animals. Human dose-response values are derived from studies that
consider human data and data from laboratory animals. With the addition
of uncertainty factors, the final dose-response values are generally
substantially lower than the level observed to cause an adverse effect
in exposed animals. Therefore, if the maximum inhalation hazard to
humans, which is the major basis for the LRD, is below the level of
concern, we do not expect adverse effects on environmental

receptors due to inhalation exposures. For the HAP that must be
included in PCWP LRD, and for which ecological inhalation toxicity
values are readily available, the human inhalation dose-response values
are protective for inhalation exposures to ecological receptors when a
hazard quotient or HI of 1.0 is used. For the details of this
comparison see the memo titled, ``Comparison of ecological inhalation
toxicity values to human health inhalation toxicity values for HAP that
must be considered in Low-Risk Demonstrations (LRDs) from sources in
the Plywood and Composite Wood Products (PCWP) source category''.
    For the assessment of persistent or bioaccumulating HAP, we made
several ecosystem-protective assumptions. We derived estimated worst-
case media concentrations by assuming the maximum air concentrations
and the maximum deposition rates occurred at the same location,
although this is often not the case. We examined six locations
representing diverse meteorological conditions, and for the final
assessment, we used the location providing the highest predicted HAP
concentrations. We used the most conservative ecological screening
values readily available, which may overestimate the potential for
toxicity to site-specific populations and communities. Finally, we
assumed 100 percent bioavailability of the HAP, although site-specific
bioavailability is often much less. The results of our ecological
assessment demonstrate that for all pollutants assessed, and for all
pathways assessed, the ecological hazard quotient values are less than
1. The highest hazard quotient is 0.043, or more than 20 times below a
level of potential concern. Given this result, and the ecosystem-
protective nature of the assessment scenario, we do not believe that
HAP emitted from PCWP facilities will harm local ecosystems. Therefore,
we conclude that HAP emissions from any source that demonstrates
eligibility to join the low-risk PCWP subcategory will not cause an
adverse environmental effect.

D. The Dose-Response Value Used for Formaldehyde

    Comment: One commenter noted that in proposing the risk-based
exemption idea, EPA indicated that it would use unit risk estimates
(UREs) from EPA's Integrated Risk Information System (IRIS) to
calculate whether or not a given source is low-risk. However, in the
final rule, EPA relied on a much lower value derived by the CIIT
Centers for Health Research (CIIT)(previously the Chemical Industry
Institute of Toxicology) using a model that estimated the carcinogenic
effects of formaldehyde on the respiratory system.
    Several commenters recommended that EPA continue to use the IRIS
potency factor for formaldehyde until EPA has completed its thorough
review process (including public review) and updated IRIS. The
commenters stated that adopting a factor that has not undergone the
full IRIS review process jeopardizes public health. The commenters
recommended that EPA accelerate completion of the IRIS review.
    To the contrary, one commenter believes that EPA properly evaluated
the carcinogenicity of formaldehyde by abandoning the outdated and
scientifically inaccurate IRIS value and instead relying on evidence
that has received broad acceptance in the international scientific
community. The commenter also believes that IRIS is far from
definitive, as EPA resource constraints have resulted in many chemical
summaries that are significantly outdated. The commenter contended that
EPA management has repeatedly emphasized that EPA is required to
consider other information, in addition to the IRIS database, when
evaluating the health effects of chemicals in a regulatory context.
    Response: We agree with the first commenters that we should use the
best available sources of health effects information for risk or hazard
determinations. As we have stated previously, we do not rely
exclusively on IRIS values. Rather, we consider all credible and
readily available assessments.\2\ For air toxics risk assessments, we
identify pertinent toxicity or dose-response values using a default
hierarchy of sources, with IRIS being the preferred source, to assist
us in identifying the most scientifically appropriate benchmarks for
our analyses and decisions. The IRIS process contains a peer-review
process, and the resulting values represent EPA consensus. When
adequate toxicity information is not available in IRIS, we consult
other sources in a default hierarchy that recognizes the desirability
of review and consistency with EPA risk assessment guidelines. This
process ensures that we have consistent and scientifically sound
assessments. Furthermore, where the IRIS assessment is relatively dated
and newer peer-reviewed assessments are available, we will consider the
full set of such assessments in selecting the basis for the risk
assessment. In the case of formaldehyde, we have determined that the
cancer potency derived using the approach developed by CIIT, which has
been peer reviewed by an external review panel sponsored by EPA and the
Canadian government, represents an appropriate alternative to EPA's
current IRIS URE for formaldehyde. Therefore, this potency represents
the best available peer-reviewed science at this time. We also agree
with the last commenter that the issue of changing health-based
guideline values is a general challenge in setting health-based
regulations. However, we are committed to setting such regulations that
reflect current scientific understanding, to the extent feasible. If
dose-response values change, PCWP sources in the low-risk subcategory
must ensure that they continue to meet the low-risk requirements in
appendix B to subpart DDDD using the revised values. If PCWP sources no
longer meet those low-risk criteria due to a change in a peer-reviewed
dose-response value selected by the Agency for those assessments, that
source must comply with the technology standards of the PCWP MACT.
Facilities conducting LRD should refer to appendix B to subpart DDDD of
40 CFR part 63 for guidance on choosing appropriate dose-response
values.
---------------------------------------------------------------------------

    \2\ U.S. Environmental Protection Agency. 1999. Residual Risk
Report to Congress. Office of Air Quality Planning and Standards,
Research Triangle Park, NC 27711, March 1999, EPA-453/R-99-001;
available at http://www.epa.gov/ttn/oarpg/t3/meta/m8690.html. (EPA

1999)
---------------------------------------------------------------------------

    Comment: Several commenters submitted in-depth comments relating to
the CIIT report and carcinogenicity of formaldehyde. Some commenters
argued that the CIIT model for carcinogenic potency of formaldehyde is
limited in a number of ways, and needs further validation and peer
review. The commenters described recent epidemiological studies that
reportedly link formaldehyde exposure to leukemia. Other commenters
believe that EPA correctly evaluated the formaldehyde cancer potency
value for the final rule and stated that the CIIT risk assessment is
the best available science. The commenters disagreed that the
availability of new scientific studies justifies use of the outdated
IRIS value and argued that the new studies are flawed.
    Response: As mentioned above, we are committed to using the best-
available science for our risk assessments. In situations where the
IRIS assessment lags behind current scientific knowledge and newer
peer-reviewed assessments are available, we will consider the full set
of such assessments in selecting the basis for the risk assessment.
These alternatives need to be grounded in publicly-available,

peer-reviewed information. In the case of formaldehyde, we have
determined that the cancer potency derived using the approach developed
by CIIT and peer-reviewed by an independent expert peer review panel
sponsored by EPA and the Canadian government represents an appropriate
alternative to EPA's current IRIS URE for formaldehyde, and is
therefore the best-available peer-reviewed science at this time.
However, we note that a comprehensive reassessment of cancer risk has
been initiated for IRIS. This reassessment will include modeling
analyses and endpoints (e.g., lymphohematopoietic cancer) not
considered in the CIIT assessment. We expect the IRIS reassessment to
be completed in 2007. The revised IRIS assessment will represent the
best-available peer-reviewed science at the time of its completion and
we will require LRD to use the revised URE that results from the
reassessment process.

E. Appendix B to 40 CFR Part 63 Subpart DDDD Requirements

1. Average Stack Heights
    Comment: One commenter stated that the promulgated risk assessment
methodology allows a source to use average stack heights, which
decreases the accuracy of the risk assessment and may significantly
understate the risks from any given source. The commenter stated that
EPA's proposal to incorporate a weighted stack height for the look-up
tables only exacerbates the problem. The commenter predicted that
sources will only use the weighted stack height when it is to their
advantage.
    Other commenters stated that the values in the look-up tables and
the use of average stack heights are not health protective under worst-
case conditions. The commenters stated that dispersion is a non-linear
function and it is impossible to try and simplify the effects of a
stack. For example, the impact of a 40-foot stack is not one half the
impact of a 20-foot stack. In fact, depending on the building heights
and the distance to the receptor, the impact of the taller stack could
be similar to the shorter one.
    One commenter disagreed that use of average stack heights where
there are multiple emissions points may significantly understate risks.
The commenter pointed out that the LRD requires sources to use the
shortest distance to the property boundary, coupled with the average
stack height. The commenter believes that use of the shortest distance
to the property boundary would more than compensate for any
underestimates in exposure in any unlikely instances where lower
emitting sources have the taller stacks.
    Two commenters supported EPA's proposal to replace the average
stack height calculation for the look-up tables in appendix B to
subpart DDDD with a separately computed toxicity-weighted stack height
corresponding to each of the three health effects. One commenter noted
that the large majority of emissions from wood products facilities
occur through relatively tall stacks. However, wood products facilities
also have many very low-emitting emission points that are quite close
to the ground. As promulgated, the rule requires these low-emitting
near-ground emission points to be averaged with the higher-emitting
stack emission points to develop an average stack height that
understates actual stack heights. Therefore, the promulgated approach
results in an overly conservative estimation of actual stack height
which, coupled with the conservative assumption of using the shortest
distance to the property boundary and the other elements of
conservatism built into the look-up tables, goes beyond what is needed
to protect human health with an ample margin of safety. The commenter
stated that the proposed toxicity-weighted stack height approach
addresses this issue in a reasonable and appropriate manner.
    Another commenter agreed, arguing that assuming all emissions occur
at the location of the stack with the minimum distance to the property
boundary is unnecessarily conservative. The commenter recommended that
an appropriate average property boundary distance be calculated using
the same toxicity-weighted averaging procedure suggested for stack
height.
    Response: We agree that the average stack height is not the best
metric for characterizing risks in a look-up table analysis. Appendix B
to subpart DDDD now requires the calculation of a toxicity and
emissions-weighted stack height for the look-up table analysis. Using
this approach, the emission points with the highest toxicity-weighted
emission rate will contribute the most to the stack height calculation
while the emission points with the lowest toxicity-weighted emission
rate will contribute the least. Thus, the weighted stack height metric
provides a more accurate characterization of a source's emissions
characteristics and it addresses commenters' concerns about under-
predicting risks for sources with most emissions coming from the
shortest stacks. Further, using this more precise method does not
undercut our reliance on other health-protective assumptions in the
look-up table analysis when most of the emissions come from taller
stacks.
    Use of weighted stack height is not optional, but is required for
facilities performing the look-up table analysis in their LRD. We
proposed to replace the average stack height calculation with the
weighted stack height calculation.
    Contrary to one commenter's statement, we do not assume dispersion
to be linear with stack height. Rather, the allowable emission rates in
the look-up tables are based on actual dispersion model runs using the
stack heights given in the table. Additionally, we agree that
collapsing across multiple stacks to generate a single weighted stack
height will not result in the exact same model output as if each stack
is modeled separately. However, use of the weighted stack height is a
simplifying step that is not expected to be consistently more or less
health-protective than modeling each stack separately. Because the
look-up table analysis is designed to be simple and because several
inputs to the tables bias them toward overestimating risks for most
sources, using a weighted stack height is appropriate in this context.
We agree with the commenter that, in cases where stacks are located on
top of buildings, building height can impact dispersion and risk.
Therefore, appendix B requires that when sources determine their stack
heights, they must use the height of the stack above the ground.
Therefore, if a stack is located on top of a building, that building
height is incorporated into the stack height value. We also agree with
the commenter that receptor location impacts risks. A look-up table
analysis inherently incorporates health-protective assumptions
regarding receptor location. The allowable emission rates in the look-
up tables are based on the maximum predicted offsite pollutant
concentrations, regardless of whether that site is populated.
Additionally, sources must use the shortest distance between an
emission point and the property boundary when conducting a look-up
table analysis. Therefore, sources using the look-up tables must assume
that all HAP emissions are coming from the emission point closest to
their property boundary, that people live at the location of maximum
predicted pollutant concentration, and that they remain at that
location for a lifetime. This approach is more health-protective than
if actual facility configuration and/or the location of actual
populations were to be considered.
    We also disagree with changing the minimum distance to property
boundary. We recognize that using the

minimum distance to property boundary may overestimate the ambient
concentration and exposure. However, the lookup table analysis is meant
to be health-protective and using the minimum distance to property
boundary helps ensure that this is the case.
2. HAP With No Health Benchmarks
    Comment: One commenter stated that the promulgated risk assessment
methodology fails to account for all HAP emitted by PCWP sources,
omitting some HAP like propionaldehyde, one of the ``predominant'' HAP
emitted by PCWP sources. The commenter noted that EPA's methodology
would assign a zero cancer risk to any HAP for which EPA has yet to
estimate such a value, even if such HAP may well be carcinogenic.
    One commenter stated that six HAP (acrolein, acetaldehyde,
formaldehyde, methanol, phenol, and propionaldehyde) make up 96 percent
of the emissions from wood products facilities. The only one of these
chemicals lacking a health benchmark is propionaldehyde. The commenter
stated that EPA could extrapolate a propionaldehyde health benchmark
from occupational exposure limits. Even using the resulting health
benchmark, the commenter's analysis has demonstrated that
propionaldehyde makes no meaningful contribution to individual source
risk.
    The commenter noted that EPA conducted a preliminary analysis of
the risks associated with PCWP facilities which narrowed the substances
considered to eight HAP, suggesting that the other HAP either were not
emitted from these facilities or were emitted in such low levels as to
not be meaningful contributors to risks in the source category. The
commenter referred to a sensitivity analysis they commissioned and
stated that the available data indicate that pollutants without health
benchmarks do not have the potential to influence risk results for wood
products industry. Accordingly, the commenter believes that EPA was
justified in not requiring sources to consider the potential risks of
pollutants emitted by wood products facilities that do not have health
benchmarks.
    The commenter disagreed that EPA has acted arbitrarily in assuming
zero cancer risk for HAP for which it has yet to estimate such a value.
The commenter noted that the petitioners want EPA to assume that all
chemicals for which EPA has not set a cancer potency value are
carcinogenic. The commenter believes the petitioners' approach would
prevent EPA or any regulatory agency from ever making any realistic or
meaningful evaluation of potential risks (in any context) and would
merely serve to confuse (and scare) the public by suggesting that
sources pose cancer risks when in fact they do not.
    Response: We are committed to using the best science available for
our risk assessments. To maintain this standard, we are using the
default hierarchy of sources for cancer and non-cancer dose-response
values that was originally developed for EPA's National-Scale Air
Toxics Assessment (http://www.epa.gov/ttn/atw/nata/natsa4.html). When

developing this hierarchy, we considered conceptual consistency with
EPA risk assessment guidelines and the level of review incorporated
into the dose-response values from each source. The EPA's IRIS process
is the preferred source of dose-response values. When IRIS values are
not available, we consider the alternative sources in our hierarchy.
Additionally, in cases where the IRIS value lags behind the scientific
literature, we are committed to considering alternative, credible dose-
response values. Currently, we do not have an IRIS file for
propionaldehyde, and an assessment is not available from the
alternative sources in our hierarchy. However, appendix B to subpart
DDDD requires sources to update their risk assessments if parameters,
including dose-response values, change in a way that could increase
risks. Therefore, if an acceptable cancer potency or non-cancer
reference value for propionaldehyde becomes available, we will consider
whether this HAP should be included in risk assessments for PCWP
sources. One commenter suggested that we use a modified occupational
exposure limit for propionaldehyde. In the past we have modified
toxicity values developed for other purposes so that they can be used
for inhalation assessments that support non-regulatory, screening
applications. However, because in the present case the modified
exposure limit would be used to make regulatory decisions, such a dose
conversion is inappropriate, particularly in the absence of scientific
peer-review.
    We agree that it is appropriate to limit the number of HAP that
must be included in PCWP affected source LRD to only those HAP that may
possibly result in meaningful contributions to the affected source
risk. However, we are not limiting the HAP included in the LRD to the
six HAP defined as total HAP in subpart DDDD of 40 CFR part 63
(acrolein, acetaldehyde, formaldehyde, methanol, phenol, and
propionaldehyde). We identified the most prevalent HAP based on mass
emitted for purposes of developing MACT compliance options because MACT
is technology-based (i.e., the same technology that reduces emissions
of the six HAP also reduces emissions of other organic HAP). The six
HAP defined as total HAP in subpart DDDD of 40 CFR part 63 are the HAP
that are most often emitted in detectable amounts from the most PCWP
process units, and these HAP make up 96 percent of the mass of
nationwide HAP emissions from the PCWP industry. However, the risks
associated with emissions of HAP are dependent on the mass emitted and
the relative toxicity of each HAP. Thus, the HAP emitted in the
greatest mass may not result in the most risk because the HAP may not
be as potent as other HAP emitted in lower mass. For example, methanol
is the HAP emitted from the PCWP industry in the greatest mass, but
because methanol is not as toxic as other HAP emitted (e.g.,
formaldehyde, certain HAP metals), it does not result in as much risk
as do other HAP.
    The commenter is correct in that our preliminary risk analysis
conducted prior to proposal of the PCWP rule narrowed the list of HAP
emitted from PCWP affected sources. We acknowledge receipt of the
commenter's sensitivity analysis based on the data used in our pre-
proposal risk analysis. Following proposal, we conducted a more
detailed risk analysis to evaluate the merits of including a low-risk
subcategory in the final PCWP rule. This memo is available in the
docket and is titled, Risk Assessment for the Final Maximum Achievable
Control Technology (MACT) Rule for the Plywood and Composite Wood
Products (PCWP) Source Category. This post-proposal analysis considered
emissions of more than 30 HAP emitted from the PCWP source category.
Many of these HAP are only emitted in minute amounts that have been
detected from a small number of PCWP process units. Nevertheless, we
included them in our risk analysis to determine their contribution to
PCWP affected source risk. We reviewed the toxicity values for each HAP
and the mass of each emitted from PCWP affected sources to determine if
it would be appropriate to narrow the list of HAP that PCWP affected
sources must consider in their LRD. Based on our review, we determined
that 95 percent of the cancer risk at PCWP affected sources is
accounted for by the following HAP: acetaldehyde, benzene, arsenic,
beryllium, cadmium, hexavalent

chromium, lead, nickel subsulfide, and formaldehyde. We also determined
that 95 percent of the non-cancer risk at PCWP affected sources is
accounted for by the following HAP: acetaldehyde, acrolein,
formaldehyde, phenol, MDI, arsenic, cadmium, and manganese. We feel
that inclusion of these HAP in a demonstration of eligibility of the
low-risk PCWP subcategory is appropriate. Limiting the list of HAP that
must be included in the LRD to 13 HAP minimizes emissions testing
costs, while ensuring that the HAP that drive the risk at PCWP affected
sources are accounted for on a site-specific basis.
3. Topography and Weather Patterns
    Comment: One commenter stated that EPA's methodology treats all
PCWP plants as though their local topography and climate are identical
and that factors like prevailing winds are ignored. The commenter
believes the risk assessment methodology should account for topography
since different topographical features may exacerbate HAP exposures.
The commenter stated that PCWP plants are located at widely varying
altitudes and attached a chart.
    One commenter stated that the modeling behind the development of
the look-up table should consider downwash. Another commenter stated
that facilities in areas with complex terrain should not be allowed to
use the look-up tables because the assumptions used to develop the
look-up table could not possibly account for this scenario. The
commenter expressed concern that the look-up tables do not account for
the common use of rain caps and for the likely event of building
downwash.
    One commenter disagreed that EPA's look-up tables fail to account
for topography and weather patterns. To the contrary, the commenter
noted that EPA made conservative assumptions (e.g., minimum fence line
distance, worst-case meteorology, safety factors built into RfCs and
UREs, and the assumption that plumes from all sources directly
overlap), such that the look-up tables would be more likely to
overestimate (rather than underestimate) actual risk. One commenter
stated that it is unlikely that consideration of terrain will
substantially affect the screening risk emission levels, given that
most PCWP facilities are located in areas characterized by flat or
gently rolling terrain.
    Response: We disagree that we have not considered site-specific
differences between sources in the methodology of appendix B to subpart
DDDD. If sources conduct site-specific risk assessments, they should
either use site-specific data, including for meteorological and
topographical information, or they should use health-protective
defaults. For look-up table analyses, we have made a number of health-
protective assumptions, including worst-case meteorological conditions.
Therefore, even though the look-up tables treat all sources as if they
have the same meteorology, that default meteorology should result in
higher predicted risks than actual site-specific meteorology.
    However, we do not agree that the protective measures inherent in
the look-up tables justify their use in all cases. As several
commenters identified, we recognize that site-specific factors such as
building downwash, the presence of rain caps, and complex terrain were
not accounted for in the SCREEN3 dispersion modeling used to create the
look-up tables. In situations where these factors can have a
significant impact on the risks presented by a source, we agree that
use of the look-up tables is not appropriate. Where we determine,
during the risk assessment review process, that the look-up tables are
inappropriate, sources would be required to demonstrate eligibility
using a site-specific risk assessment. If a source is unable to make
this demonstration, the source must then comply with the technology
standards in the MACT.
4. Children's Health Risk
    Comment: One commenter stated that EPA's risk assessment
methodology does not adequately account for the sensitivities of
children to environmental stressors because the methodology relies on
pre-existing cancer potency estimates which are deficient with respect
to early-life exposures.
    However, another commenter believes that EPA's cancer potency
factors are amply conservative to protect against potential childhood
cancer risk. The commenter stated that the unit risk factor (URF) is
specifically based on worst-case assumptions (i.e., linear multistage
model for calculating the URF and through the assumption that a person
will be continuously exposed for a lifetime).
    Response: The EPA has issued revised Guidelines for Carcinogen Risk
Assessment (Guidelines) and also Supplemental Guidance for Assessing
Susceptibility from Early-Life Exposure to Carcinogens (Supplemental
Guidance) which deal specifically with assessing the potential added
susceptibility from early-life exposure to carcinogens. The
Supplemental Guidance provides an approach for adjusting risk estimates
to incorporate the potential for increased risk due to early-life
exposures to chemicals that are concluded to be carcinogenic by a
mutagenic mode of action. For these chemicals, the supplemental
guidance indicates that, in lieu of chemical-specific data on which age
or life-stage specific risk estimates or potencies can be based,
default age-dependent adjustment factors can be applied when assessing
cancer risk for early-life exposures. As EPA's hazard and dose-response
assessments are updated under the new Guidelines and Supplemental
Guidance, they will include consideration of the available information
with regard to mode of action and the potential for this determination.
Thus, when estimating cancer risks for the purposes of this regulation,
the current HAP-specific assessments must be consulted to obtain both
the current inhalation unit risk values and the determination as to
mode of action. Where EPA's assessment has determined that the chemical
is carcinogenic by a mutagenic mode of action, it is recommended that
the risk assessment developed for the purposes of this regulation
employ applicable life-stage specific potencies or age dependent
adjustment factors per the Supplemental Guidance when early life
exposure is expected to occur.
5. Distance to Nearest Residence
    Comment: Commenters noted that the risk calculation depends upon
the distance any given source is to the nearest residence, ignoring the
possibility that there may be exposed people closer to the facility,
such as a school, day care center, or neighboring business. One
commenter stated that the most exposed individual is likely to be a
person who actually works at the PCWP facility as opposed to a person
beyond the facility fence line.
    One commenter believes EPA should revise the risk screening to use
the distance to the property line instead of the distance to the
nearest resident. The commenter believes that both the look-up tables
and the site-specific screening should use the property boundary or the
point of maximum impact for the LRD.
    A separate commenter disagreed that EPA should have required the
site-specific assessments to evaluate continuous lifetime exposure at
the nearest receptor (as opposed to the nearest residence), whether it
be a school, shopping mall or church. The commenter noted that the
promulgated PCWP rule allows risks to be computed at residential
locations with the highest modeled risk for site-specific assessments.
The commenter believes this is appropriate because EPA requires sources
to assume the worst-case

exposure scenario (i.e., continuous, lifetime exposure for 70 years).
The commenter noted that people would not spend 24-hours per day, 365
days per year for 70 years at a school, shopping mall or church.
Although this exposure scenario is equally implausible for residences,
the commenter thinks that residential locations are a more appropriate
choice.
    The commenter noted that the rule does not explicitly address the
receptors that should be applied for the acute exposure assessments
(which are required independently for acrolein and formaldehyde). The
commenter requested that the rule clearly state that for acute
exposures, the proper reference is to the property boundary rather than
to the nearest residence.
    Response: In exercising our authority under section 112(c)(9), we
do not think it is appropriate to base our determinations on risks
presented at the PCWP facility due to occupational exposures, since
such risks are not caused by emissions of HAP into the ambient air
(i.e., since they are on the plant site, they are not beyond the plant
fence line and are therefore not into the ambient air). However, we do
agree that risks to individuals at other locations surrounding the
source could potentially exceed risks to individuals at nearby
residences. Therefore, we have modified appendix B to subpart DDDD to
indicate that, in addition to residences, risk assessments should
include consideration of other locations such as schools and day care
facilities. We note that, as we described in EPA's ATRA Reference
Library, sources can deviate from default exposure assumptions if they
can provide adequate justification for the deviation. Such deviation is
appropriate where exposure duration is limited in terms of hours per
day, days per week, and/or total number of years.
    Look-up table assessments must use distance to property boundary,
not distance to nearest residence. This requirement, which uses the
point of maximum impact outside the property boundary, adds to the
health-protection provided by look-up tables. We agree with the
commenter that this is the preferred approach for the look-up table
analyses. However, we disagree that site-specific risk assessments
should be limited to the property boundary. If a site-specific risk
assessment uses nearest residences for their risk calculations, and if
new residences are constructed in an area of higher risk, sources must
re-assess their risks to ensure they continue to meet the criteria in
appendix B to subpart DDDD. If they no longer meet these criteria (e.g.
because someone moved closer to their facility), then the source is no
longer eligible for the low-risk subcategory. Such a source must then
comply with the technology standards in the PCWP MACT.
    We agree that acute assessments should use the point of maximum
impact outside the facility's property boundary. This requirement is
stated explicitly in appendix B to subpart DDDD.
6. Criteria Included in Site-Specific Risk Demonstrations
    Comment: One commenter stated that EPA gives sources the ability to
make source-specific demonstrations with a number of open-ended
criteria. For instance, the commenter noted that appendix B to subpart
DDDD allows any scientifically accepted peer-reviewed assessment
methodology for site-specific risk assessment, and instructs sources to
use health-protective default assumptions wherever site-specific data
are not available. Thus, the commenter believes the facility owner has
extreme control over how to assess its risks, and EPA provides few
bounds on its discretion to approve such assessments as sufficiently
scientifically accepted or health protective. Another commenter
believes that the rule does not require that the risk assessment
methodology be approved by any regulatory agency as scientifically
acceptable or applicable.
    One commenter stated that the approach included in the final rule
is consistent with general risk assessment methodologies, including
recommendations from the National Academy of Sciences Science and
Judgment in Risk Assessment (1994) and has been standard EPA practice
for over a decade. The commenter noted that EPA specifies its
preference that sources conduct their site-specific risk assessments in
accordance with the ATRA Reference Library (Volume 2) should facilities
not pass the initial look-up table screening analysis. Sources also
have the option of using alternative modeling methodologies provided
they have undergone scientific peer review. The commenter believes that
this does not, in turn, give sources unfettered freedom, but does
recognize that new modeling approaches may be developed in the future.
    Response: We continue to believe that providing sources with the
discretion to use any ``scientifically-accepted, peer-reviewed risk
assessment methodology'' (e.g., see EPA's ATRA Reference Library) is
appropriate. However, contrary to the assertions of some commenters,
this discretion is not unlimited. Section 7 of appendix B to subpart
DDDD presents specific minimum criteria for site-specific low risk
assessments. In order to demonstrate eligibility for the low-risk
subcategory, the site-specific risk assessment conducted by the
facility must meet the following criteria: (1) Estimate long-term
inhalation exposures through an estimation of annual or multi-year
average ambient concentrations; (2) estimate acute exposures for
formaldehyde and acrolein maximum 1-hour average ambient
concentrations; (3) estimate the inhalation exposure of the individual
most exposed to source emissions; (4) estimate individual risks over a
70-year lifetime for the chronic cancer risk assessment; (5) use site-
specific quality-assured data wherever possible; (6) use health-
protective default assumptions wherever site-specific data are not
available; and (7) contain adequate documentation of the data and
methods used so that it is transparent and reproducible. The ATRA
Reference Library provides examples of how a risk assessment can be
conducted. These examples include instruction in basic risk assessment
methodology, in determining what parameters to include in a risk
assessment, and in the constraints that should be placed on those
parameters. The documents within the ATRA Reference Library have been
peer-reviewed and were developed according to the principles, tools and
methods outlined in the 1999 EPA Report to Congress. However, the
guidance in the ATRA Reference Library may not be appropriate for all
sources. For that reason we believe that it is important for sources to
be able to consider alternative analytical tools as long as those
alternatives are scientifically defensible, peer-reviewed and
transparent per the criteria listed above. Additionally, we disagree
with the commenter that the risk assessment methodology will not be
approved by a regulatory agency. The EPA will be responsible for
reviewing all PCWP risk assessments, and part of that review will
include ensuring that an appropriate assessment methodology is used.
The EPA may disapprove any risk assessment that fails to meet the
criteria of appendix B to subpart DDDD.

F. Selection of Process Units and Emissions Determination Procedures in
Table 2A to Appendix B to 40 CFR Part 63 Subpart DDDD

1. Use of Emission Factors and Other Emission Estimation Procedures
    Comment: Two commenters addressed EPA's proposed amendment to allow
facilities to use emissions

factors in LRD for certain process units rather than conduct emissions
tests. One commenter strongly supported both EPA's decision to simplify
the calculation of emissions used in the risk assessments and the
concept of using default emission values for relatively low emitting
and/or hard-to-test process units because many of the process units
included in table 2A to appendix B to subpart DDDD cannot be tested
without research-level effort. Another commenter disagreed with the
proposal to allow facilities to demonstrate compliance with the
requirements of the low-risk subcategory using emissions factors and
emissions estimates instead of conducting emissions tests. The
commenter noted that EPA's own publications, including AP-42 and
reports by the Office of the Inspector General, state that the use of
emission factors for compliance purposes is inappropriate. According to
the commenter, this proposal does not satisfy the section 112(c)(9)(B)
requirement that EPA determine that all sources in a category emit HAP
at levels below identified risk thresholds prior to exempting the
category from applicable MACT standards. In addition, the approach does
not fulfill EPA's commitment to require ``enhanced monitoring'' from
all sources subject to a section 112 MACT standard.
    Response: Appendix B to subpart DDDD provides methodology and
criteria for sources to demonstrate whether they are part of the
delisted low-risk subcategory. Sources that are part of the delisted
low-risk subcategory are not part of the PCWP source category.
Therefore, in developing the emission factors in table 2A to appendix B
to subpart DDDD, we used the maximum available emission rate, as
opposed to the average emission rate, to ensure that emission estimates
used for LRD are health protective and reasonably account for the
uncertainty associated with using emission factors.
    Because the LRD are to be based on the cumulative risk from all
process units within each PCWP affected source, we are requiring that
each process unit be considered in the LRD. In developing table 2A to
appendix B to subpart DDDD, we considered the feasibility of emissions
testing for each type of PCWP process unit and chose to allow emission
factors to be used for selected hard-to-test process units. We believe
that most of the process units for which we would allow emissions
estimates in lieu of testing are minor contributors to the total HAP
emissions relevant to the LRD. Because sources may use only the most
health-protective emission factors for only hard-to-test process units,
we do not believe risk assessments will be less health protective with
the inclusion of emission factors.
    Affected sources that are not part of the low-risk subcategory must
comply with the MACT requirements in subpart DDDD, and subpart DDDD
contains compliance monitoring requirements for all the process units
with control or work practice requirements under subpart DDDD. Sources
that demonstrate eligibility to join the delisted low-risk PCWP
subcategory, instead, are not subject to the section 112 MACT standard.
Therefore, the PCWP rule follows through with the commitment to require
all sources subject to section 112 MACT standards to conduct ``enhanced
monitoring.''
    Comment: Two commenters addressed the use of maximum emission
factors and the use of statistically-derived emission factors in table
2A to appendix B to subpart DDDD. One commenter disagreed that EPA
should use statistically-derived emission factors because, in many
cases, there are insufficient data available to perform a statistical
analysis. The commenter stated that where there is sufficient data,
applying a statistical approach would not result in significantly
different values from those already provided in table 2A to appendix B
to subpart DDDD. The other commenter disagreed with EPA's use of
maximum emission factors for hard-to-test process units. The commenter
stated that some of the factors are so high that some sources will be
forced to attempt to find ways to test the hard-to-test process units.
The commenter suggested the EPA either multiply all emission factors by
0.75 (or some other constant) or study the data for each factor and
statistically select a lower factor that is still conservative and
guards public health but enables sources to avoid costly and
unproductive testing.
    Response: We proposed to include in appendix B to subpart DDDD the
maximum emission factors available for each type of process unit
because we believe use of maximum emission factors builds conservatism
into the emissions estimates to help account for unit-to-unit
variability and ensures protection of human health. However, in the
preamble to the proposed amendments, we requested comment on using
other statistical approaches. We received only one comment in favor of
using a statistical approach, and the commenter did not provide any
basis for assuming that emissions from untested PCWP process units are
75 percent of the emissions from the highest-emitting process units for
which we have data. We recognize that some of the emission factors
presented in table 2A to appendix B to subpart DDDD are quite
conservative, that emission testing costs can be significant, and that
some process units cannot easily be configured for emission testing.
However, we disagree that use of the maximum emission factors is
unnecessarily burdensome to small plants and companies because becoming
part of the low-risk subcategory is only one option under subpart DDDD,
and it is an option provided to reduce the burden on PCWP facilities
that do not pose a significant risk to human health or the environment.
2. Blenders, Sanders, and Saws
    Comment: One commenter disagreed that emissions testing is ``not
feasible'' for several process units, including blenders, sanders, and
saws. These sources are usually controlled by baghouses, which are
normally required to be tested for particulate matter (PM). Because HAP
emissions from these units can be high, the commenter recommended that
actual test data be used rather than emission factors.
    Response: We disagree that we should require testing of blenders,
sanders, or saws. Methanol is the predominant HAP emitted from
blenders. Methanol can also be emitted from sanders and saws. Methanol
is not a HAP of concern for purposes of the LRD. Our emission estimates
indicate that the appendix B HAP emissions from blenders, sanders, and
saws contribute to, but are not likely to drive the risk determination
for a PCWP facility because the emissions of these same HAP from dryers
and presses exceed those from blenders, sanders, and saws.
    Furthermore, based upon the information available to us, we
disagree that most blenders, sanders, and saws are controlled by
baghouses and that PM emission testing is normally required for these
process units. We maintain that very few blenders, sanders, and saws
are already configured for emissions testing. We also believe that we
have struck an appropriate balance between the process units that must
be tested and the process units for which maximum emission factor
estimates will suffice for purposes of the LRD. As a result, we are not
requiring emissions testing of blenders, sanders, and saws in today's
final amendments.
    Comment: One commenter suggested converting the acetaldehyde value
for finishing sanders from 0.0028 lb/MSF \3/8\'' to a lb/MSF surface
area basis to be consistent with the other sander values.
    Response: As requested, we have recalculated the finishing sander
acetaldehyde emission factor based on

the production rate in terms of MSF/hr, and have included the revised
factor (0.0031 lb/MSF) in table 2A to appendix B to subpart DDDD.
3. Emission Estimates for Lumber Kilns and Small-Scale Kiln Testing
    Comment: One commenter supported small-scale lumber kiln testing.
The commenter stated that full-scale lumber kilns are difficult to test
because they are leaky and have highly variable exhaust rates, and most
small-scale kilns do not have exhaust variability or fugitive emission
issues. The commenter also noted that there is literature comparing
results from small-scale kiln tests to the emissions from full-scale
lumber kilns. The commenter stated that if certain conditions and
guidelines are followed, the small-scale kiln tests can provide good
estimates of emissions from lumber drying. The commenter suggested
changes to the list of considerations for a small-scale kiln emissions
testing program that was suggested by NCASI and placed in the docket
prior to proposal of the amendments.
    Response: We recognize the difficulties with testing full-scale
lumber kilns due to their variable exhaust flow rates, and we agree
that measurement of small-scale kiln emissions can provide data
representative of full-scale kiln emissions provided that certain
conditions are met. We have reviewed the commenter's suggestions for
the consideration list, and we have used the list (with revisions) as
the basis for the new appendix C to subpart DDDD of 40 CFR part 63.
Facilities that do not want to use the emission factors in table 2A to
appendix B to subpart DDDD may conduct small-scale kiln tests taking
into account the considerations described in appendix C to subpart
DDDD. Small-scale kiln tests that do not address these considerations
may be rejected during our review of the LRD. The considerations
described in appendix C to subpart DDDD apply only for small-scale
lumber kiln emissions testing conducted to provide data for the LRD
described under appendix B to subpart DDDD. Permitting authorities may
require different procedures for testing or estimating lumber kiln
emissions for purposes other than the LRD.
    Comment: One commenter requested that EPA reevaluate the lumber
kiln emission factors in table 2A to appendix B to subpart DDDD.
According to the commenter, emission factors found in NCASI Technical
Bulletin 845 are based on the most credible data, and using those
factors generally results in much lower emissions than the values
selected for table 2A to appendix B to subpart DDDD in the proposed
amendments. The commenter expressed concern that using the values in
the proposed amendments may lead to facilities being improperly
classified as major sources of HAP.
    Response: The emission factors presented in the proposed amendments
to appendix B to subpart DDDD are not intended to be used for major
source determinations. Facilities that are not major sources of HAP
emissions are not subject to subpart DDDD, and the LRD procedures are
therefore irrelevant for those sources. The emission factors in
appendix B to subpart DDDD are intended to be health protective and are
intended only for use by facilities choosing not to test their lumber
kilns for purposes of the PCWP LRD. As stated previously, facilities
that feel the emission factors presented in table 2A to appendix B to
subpart DDDD would over-estimate lumber kiln emissions for purposes of
the LRD have the option of supplying facility-specific test data for
their lumber kilns. States may require data to be obtained for major
source determination using methods other than those described in
appendix B to subpart DDDD.
4. Wastewater Emission Estimates
    Comment: One commenter stated that table 2A to appendix B to
subpart DDDD should not require modeling of MDI emissions from
wastewater and process water. The commenter stated that MDI hydrolyzes
immediately upon contact with water, polymerizing into to an inert
polyurea, so any wastewater from these operations cannot contain MDI.
    Response: The commenter's assertion reflects the findings presented
by the American Chemistry Council (ACC) Diisocyanates Panel in their
petition to remove MDI from the list of HAP under section 112(b) of the
CAA. Based upon the findings described in the petition, we agree that
it is appropriate to change the entry in table 2A to appendix B to
subpart DDDD to ``NA'' for wastewater/process water operations.
However, our action with respect to table 2A to appendix B to subpart
DDDD does not necessarily reflect our conclusions with regard to the
petition to delist MDI, which we are still reviewing at this time.
5. Emission Estimates for Tanks
    Comment: One commenter stated that the current wording of the
definition of ``resin storage tank'' includes all resin additives, even
caustic and acid. Neither caustic nor acid contain formaldehyde,
phenol, or MDI, so emissions of the HAP of concern would not be
expected. Additionally, the commenter stated that vessels holding
powdered resin should not be considered resin storage tanks. The
commenter suggested a revision of the definition of ``resin storage
tank.'' The commenter also requested that EPA add a footnote to table
2A to appendix B to subpart DDDD to indicate that estimating emissions
for tanks that do not contain formaldehyde, phenol, or MDI is not
required.
    Response: As proposed, table 2A to appendix B to subpart DDDD
specifies default emission rates for tanks with resin containing a
specific HAP or modeling using TANKS software. It was not our intent to
require TANKS modeling of formaldehyde, phenol, or MDI for tanks
holding resins without these HAP, but we realize that the language in
the proposed table 2A to appendix B to subpart DDDD could be
misinterpreted in this way. For the final amendments, we have revised
the language in table 2A to appendix B to subpart DDDD to specify that
emissions of a specific HAP need only be estimated if the tank holds a
resin containing that HAP, regardless of whether the estimate is
obtained using an emission factor or modeling. We also agree that it is
not necessary to model emissions from powdered resin storage vessels,
so we have amended the definition of ``resin storage tank'' to include
only liquid resins and additives.
    Comment: One commenter stated that the emission factors included in
table 2A to appendix B to subpart DDDD for resin storage tanks are
grossly over-estimated and the alternative techniques suggested by the
table are limited and overly simplified. In addition, the commenter
stated that there can be a significant difference between average
(long-term) and maximum hourly (short-term) emissions. The emission
factors should be reduced by a factor of at least 50 for short-term
estimates and 100 for long-term. The commenter provided sample
calculations to support reducing the emissions factors.
    Response: We are aware that the default emission rates contained in
proposed table 2A to appendix B to subpart DDDD for resin storage tanks
are health protective. These emission rates represent the highest
emission rate reported for any single tank in the MACT survey
responses. Understanding the limitations of the default emission rates,
we also provided modeling using EPA's TANKS software as an option for
facilities who wish not to use the conservative default emission rates.
To alleviate concerns about these emission rates, we have reevaluated
the default emission rates for formaldehyde and

phenol. Because of the limited applicability of the emission rates
provided in the MACT survey results, we used other conservative
information from the MACT survey as inputs to the TANKS model to
generate emission estimates. We arrived at default emission rates of
0.001 pounds per hour (lb/hr) formaldehyde and 0.0002 lb/hr phenol.
    Section 7(b)(1) of appendix B to subpart DDDD requires estimation
of annual average ambient concentrations for the chronic part of a
site-specific risk assessment, and Sec.  (7)(b)(2) requires estimation
of maximum short-term (hourly) emissions of formaldehyde and acrolein
for purposes of estimating acute risk. One way to account for both
acute and chronic exposures is to assume the worst-case for all
emissions inputs to the risk model used to complete the acute and
chronic portions of the analysis. Although some facilities may choose
to use different emissions inputs in their site-specific LRD for the
chronic and acute portions of the assessment, we disagree with the
commenter that it is necessary for us to provide separate resin storage
tank default emissions rates for average (long-term) and maximum hourly
(short-term) emissions.
    Comment: One commenter stated that table 2A to appendix B to
subpart DDDD should identify specific techniques for estimating
emissions from open-top tanks separately from techniques used to
estimate emissions from closed-top tanks. These types of tanks are
often used for mixing water and other additives into the resin. The
commenter provided an equation for estimating these emissions from the
2002 EPA Risk Management Plan (RMP) Offsite Consequence Analysis
Guidance (Appendix D).
    Response: Several different approaches may be used to estimate
emissions from open-top tanks, including, for example, the 2002 EPA RMP
Offsite Consequence Analysis Guidance (Appendix D) noted by the
commenter. A similar approach is documented in Chapter 8, section 4.4
of an Emission Inventory Improvement Program (EIIP) document entitled
``Methods of Estimating Air Emissions from Paint, Ink, and Other
Coating Manufacturing Facilities.'' In addition, WATER9 or the approach
outlined in forms VII and VIII of appendix C to 40 CFR part 63 (and
described further with respect to the PCWP industry in a supporting
memorandum) could be used to estimate emissions from open-top tanks.
Rather than dictating specific methods to be used to develop estimates
of open-top tank emissions, we have amended table 2A to appendix B to
subpart DDDD to distinguish between open and closed resin storage tanks
and added a row to state that engineering estimates must be developed
for open resin storage tanks if they hold resin with any formaldehyde,
phenol, or MDI content.
6. Insignificant Activities
    Comment: One commenter stated that the phrase ``may emit'' included
in the description of ancillary process units is elusive and could
include emissions of any amount of HAP, no matter how small. The
commenter requested that lists of insignificant and trivial activities
be included in appendix B to subpart DDDD to streamline the process of
preparing LRD. The commenter noted that the title V program allows
emission units with insignificant or trivial emissions to be specified,
but no emission estimates or permit limits are required. The commenter
(and other commenters) provided suggested lists of insignificant and
trivial emission units. Alternatively, the commenter suggested that the
final amendments could explicitly allow a facility to list all the
insignificant emission units in the PCWP source category at the
facility and make a blanket ``engineering estimate'' evaluation that
they are insignificant and their emissions are presumed to be zero. The
commenter noted that if EPA disagrees with the facility's designation
of an emission unit as an insignificant emission unit during its review
of low-risk determination, then it can notify the facility that
additional justification of its engineering estimate is needed for that
emissions unit.
    Response: The amended rule does not include lists of insignificant
or trivial activities for several reasons which are documented in the
BID for the final amendments. Instead, we have adopted the commenter's
alternative suggestion. Each facility completing a LRD may include a
site-specific list of insignificant activities for which the facility
may make an engineering estimate of presumably zero appendix B
emissions. The facility must provide rationale to document placement of
each process unit or activity on the list (e.g., the unit does not
process HAP-containing materials; no heat is applied; there is no
mechanism for appendix B HAP formation, etc.). We will evaluate each
facility's list of insignificant activities when reviewing the LRD. Any
data that support the placement of a certain activity on the
insignificant activities list should be included with the facility's
LRD. Only process units and activities within the PCWP affected source
should be included in this list.
    Comment: One commenter noted that EPA did not include a definition
of ``ancillary processes'' in the rule and suggested a possible
definition.
    Response: We agree that a definition of ``ancillary processes'' is
needed since the term is used in table 2A of appendix B to subpart
DDDD, and we have defined the term in section 15 of appendix B to
subpart DDDD based on the definition suggested by the commenter (with
necessary edits).
7. Other Specific Comments on Table 2A to Appendix B to Subpart DDDD
    Comment: One commenter requested that a footnote be added to the
formaldehyde emission factor for particleboard and medium density
fiberboard (MDF) blending and forming operations in table 2A to
appendix B to subpart DDDD. The footnote should state that the factor
applies only to facilities using formaldehyde-based resins.
Formaldehyde emissions from facilities that use 100% non-formaldehyde
resins or adhesives (such as MDI) should be designated ``NA.''
    Response: We agree with the commenter that it is appropriate to
clarify that estimation of formaldehyde emissions from particleboard
and MDF blending and forming operations is only necessary for those
facilities that use resin containing formaldehyde. We have amended the
final rule to include such a footnote.
    Comment: One commenter supported excluding metals testing for
process units firing only natural gas or propane and stated that
footnote b of table 2A to appendix B to subpart DDDD should be revised
to clarify that no emissions estimates are required for direct-fired
process units firing natural gas or propane.
    Response: We agree with the commenter's suggested change to the
footnote b of table 2A to appendix B to subpart DDDD and we have
amended the footnote as requested.

G. Emission Testing Requirements in Appendix B to 40 CFR Part 63
Subpart DDDD

1. Testing of Multiple Identical Dryers
    Comment: One commenter supported the proposed amendment giving
facilities the ability to use emissions test data from one unit for
modeling of similar process units. The commenter stated that the
proposed amendment will help industry better manage emissions testing
costs and testing resources while ensuring data quality. Another
commenter stated that EPA should consider age as a factor when
determining whether units are similar.

As proposed, the amendment would inappropriately allow newer and
cleaner-operating equipment to be tested in place of older, more run
down equipment without any loss of emissions estimating accuracy.
    Response: As a result of the second comment, we reviewed available
data to see if any correlations with age of the process units are
apparent. We concluded that we do not have the emissions test data
spanning decades necessary to confirm or refute the commenter's
assertion that age of the process unit is a crucial consideration. We
generally agree that process units that are considerably older could be
expected to have greater emissions than newer process units of the same
design, particularly if the older process units have not been well
maintained. Therefore, we have included age of the process unit as a
consideration when applying test data from one unit to another similar
unit at a plant site to be conservative. However, we wish to clarify
that we consider distinctions in the age of the process unit, for
purposes of the PCWP LRD, to be many years (e.g., 5 to 10 years) since
our data do not show increased emissions as process units age over a
few years.
    Comment: One commenter suggested that EPA allow facilities to test
one of multiple stacks or vents when the gases in those vents have been
collected from the same process unit, originate from the same duct or
vent, and are not expected to differ in gaseous pollutant
concentration. The commenter clarified that this procedure should not
be allowed unless the emissions have been collected and then
subsequently divided (e.g., the procedure would be inappropriate for
multiple vents above a wood products press).
    Response: We agree with the commenter that applying results from
one stack test to the emissions from multiple stacks is acceptable for
purposes of the LRD when the gases in those stacks or vents have been
collected into a single duct and subsequently divided and are not
expected to differ in gaseous pollutant concentration. We also agree
with the commenter that testing one of multiple process unit openings
or vents, such as the vents above a wood products press, should not be
allowed because the concentration from such vents could differ. We have
added a paragraph to section 5 of appendix B to subpart DDDD to
incorporate this suggestion.

2. Use of Previous Emission Tests

    Comment: One commenter supported the proposed amendment to allow
facilities to use previous emissions test data for the purposes of LRD.
The commenter stated that the proposed amendment will help industry
better manage emissions testing costs and testing resources while
ensuring data quality. However, the commenter stated that rather than
limiting the use of previously determined emission factors to those
units that operate at the same conditions as during the emission test,
EPA should require the subject units to be operated in a manner that
would result in lower emissions. Another commenter stated that EPA
should consider age as a factor when determining whether units are
similar. As proposed, the amendment would inappropriately allow newer
and cleaner-operating equipment to be tested in place of older, more
run down equipment without any loss of emissions estimating accuracy.
    Response: We agree with the first commenter that it is not often
possible for a process unit to be operated under the exact same
conditions as during a previous performance test. It was not our
intention for this provision to be interpreted quite so literally. We
have revised section 5(i)(3) in appendix B to subpart DDDD to state
that the subject process units must be operated in a manner that would
be expected to result in the same or lower emissions than observed
during the previous emissions test and that the process units must not
have been modified such that emissions would be expected to exceed the
results from the previous emissions test.
    Regarding the second comment, we discussed the effects of process
unit age in a previous response. We are limiting previous data
submitted for purposes of the LRD to emissions test data gathered in
1997 or later. We picked 1997 as the cutoff date because we recognize
that a great deal of HAP emissions data was gathered for PCWP process
units during that year, and we do not believe that this data is
obsolete at this time provided the other conditions of section 5(i) of
appendix B to subpart DDDD are met.
3. Fuel Analysis To Determine HAP Metals Emissions
    Comment: Two commenters supported EPA's suggestion of using fuel
analyses to estimate HAP metal emissions for direct-fired process
units. One of these commenters stated that EPA should allow PCWP
facilities to use procedures similar to those in subpart DDDDD, the
Industrial, Commercial, and Institutional Boilers and Process Heaters
NESHAP (Boilers/Process Heaters rule). This option would lower testing
cost yet provide a maximally conservative value that would be
protective of public health.
    Response: We have decided to adopt a fuel analysis procedure
similar to the procedure described in the Boilers/Process Heaters rule.
Section 5 of appendix B to subpart DDDD includes a new paragraph
referring to the relevant sections of subpart DDDDD. Plywood and
composite wood products facilities may conduct a fuel analysis in lieu
of emissions testing for HAP metals for purposes of the LRD. The
relevant sections of the Boilers/Process Heaters rule include Sec.
63.7521(a) and (c) through (e); Sec.  63.7530(d)(1), (2), and (4); and
line 2 of table 6 to subpart DDDDD. For purposes of conducting a fuel
analysis for a PCWP LRD, ``total selected metals'' means the
combination of the metal compounds included in table 1 to appendix B to
subpart DDDD.
4. Formaldehyde and Phenol Test Methods
    Comment: One commenter stated that NCASI Method CI/WP-98.01 should
be allowed for formaldehyde and phenol measurement in table 2B to
appendix B to subpart DDDD. The method is allowed in other parts of the
rule for measurement of formaldehyde, phenol, and methanol, but it was
not included in appendix B to subpart DDDD. The commenter stated that
using NCASI Method CI/WP-98.01 instead of NCASI Method IM/CAN/WP-99.02
would reduce sampling cost and complexity without sacrificing sampling
precision and accuracy.
    Response: We agree that NCASI Method CI/WP-98.01, ``Chilled
Impinger Method for Use at Wood Products Mills to Measure Formaldehyde,
Methanol, and Phenol,'' is appropriate for measurement of formaldehyde
and phenol. We have added NCASI Method CI/WP-98.01 to table 2B to
appendix B to subpart DDDD for formaldehyde and phenol testing only.
    To be consistent with the test methods allowed in subpart DDDD, we
have also edited table 2B to appendix B to subpart DDDD to allow use of
Method 0011 for formaldehyde and acetaldehyde, and to allow use of
Method 316 (40 CFR part 63, appendix A) for formaldehyde.
    In addition, a revised version of NCASI Method IM/CAN/WP 99.02 has
been placed in Chapter III of the NCASI Methods Manual and the PCWP
docket. The NCASI made minor revisions to the IM/CAN/WP 99.02 method to
(1) clarify sections easily misunderstood or that did not provide
sufficient instruction and (2) to add some flexibility to the quality
assurance procedures and

criteria. We reviewed and agreed with these minor changes to the
method.
5. Determining MDI Emissions
    Comment: One commenter suggested that EPA also consider the use of
EPA proposed Method 207, ``A Method for Measuring Isocyanates in
Stationary Source Emissions,'' for measurement of MDI emissions. Method
207 is expected to provide lower detection limits than EPA CTM-031 and
Method 320, which are already allowed to be used.
    Response: We proposed Method 207 in the Federal Register on
December 8, 1997 (62 FR 64532). A copy of the proposed method may be
downloaded from http://www.epa.gov/ttn/emc/proposed.html. We intend to

make minor revisions to the method and promulgate it in appendix M to
40 CFR part 51 within the next few months. We will accept data measured
using the proposed Method 207 before the promulgated version of the
method becomes available. Once promulgated, the final method 207 will
appear in the Federal Register, appendix M to 40 CFR part 51, and on
http://www.epa.gov/ttn/emc/promgate.html.

H. Compliance Date for Existing Sources

    Comment: In response to our request for comment on the issue,
several commenters requested an extension of the MACT compliance
deadline (October 1, 2007, for existing sources). One commenter stated
that EPA should consider a compliance deadline extension for all PCWP
sources because of uncertainties associated with the promulgated
amendments, or ``supplemental rule.'' The commenter stated that EPA
could give sources 3 years (the maximum amount of time for compliance
allowed by section 112(i)(3)(A) of the CAA) from the effective date of
the supplemental rule. The commenter requested a new compliance date of
August 1, 2008 (based on an extended LRD submittal deadline of March 1,
2008), and noted that this date is less than three years from the
anticipated promulgation date of the supplemental rule. A separate
commenter suggested extending the PCWP MACT compliance deadline to
March 1, 2009 (based on a suggested LRD submittal deadline of March 1,
2008). Another commenter suggested extending the PCWP MACT compliance
deadline to October 1, 2008 (based on a suggested LRD submittal
deadline of April 1, 2007). The above commenters also suggested that
EPA extend the compliance dates for sources that submit LRD that are
not approved by EPA.
    One commenter disagreed that facilities that do not submit a LRD
should be granted any additional time to comply with MACT. The
commenter also stated that if an existing facility's LRD is not
approved, the facility should be given no more than one year from the
current compliance date to comply with all requirements of the rule.
Another commenter asserted that section 112(i)(3)(A) denies EPA
authority to extend the rule's compliance date beyond October 1, 2007
for sources whose LRD are disapproved or for all PCWP sources.
    Response: We are promulgating a MACT compliance date of October 1,
2008 in today's final action. We are providing this new compliance date
for all PCWP sources (as opposed to only those sources that submit
LRD). We are making this change to the MACT compliance date because
today's final action results in revisions to several definitions in
subpart DDDD and to the testing requirements in appendix B to subpart
DDDD that are substantial and warrant revision of the MACT compliance
date.
    Our proposal specifically asked for comments on whether to set a
new compliance deadline for all sources covered by the PCWP NESHAP. As
mentioned by the commenters, section 112(i)(3)(A) of the CAA specifies
that NESHAP for existing sources can have compliance deadlines of no
more than 3 years following the effective date of their promulgation.
The question then becomes which promulgation date to apply--July 29,
2004, which is the date the PCWP NESHAP was first promulgated, or
today's date, on which we are promulgating numerous revisions to the
rule. We interpret section 112 of the CAA as providing us with the
authority to re-set the compliance deadline for NESHAP, as appropriate,
in situations where promulgated amendments to the regulation are
significant and substantial enough to warrant revisiting the question
of how much time is needed for subject sources to comply with the
requirements of the rule, as amended. This includes situations where a
NESHAP is significantly revised to include additional control
requirements in response to either a court's remand of the original
rulemaking or a petition for reconsideration of the rule, or is so
revised on the agency's own initiative.
    We agree with the commenters that noted that section 307(b)(1) of
the CAA specifically provides that the filing of a petition for
reconsideration of a rule does not postpone the effectiveness of the
rule. We do not consider the mere fact that a rule has become the
subject of a petition for judicial review or a petition for
administrative reconsideration to necessarily justify a re-setting of
the compliance deadline. As we stated in the final reconsideration
notices for the Brick and Boiler MACT rules (70 FR 69661, November 17,
2005 and 70 FR 76928, December 28, 2005, respectively), the
uncertainties raised by reconsideration do not in general necessarily
justify an extension of the compliance date. Instead, the facts of each
rule's potential revision and the degree of the significance of the
rule's amendments should be considered on a case-by-case basis. Where
EPA has amended a MACT standard in a significant way, we have found it
appropriate to set a new compliance date for the rule that takes into
account new requirements not contained in the original rule. The
relatively greater degree of changes we made to the overall PCWP rule,
which substantially affect how it will be implemented for the majority
of sources, as compared to changes we made to the Boiler MACT (we made
no changes to the Brick MACT due to reconsideration), for example,
justify a different outcome for the PCWP rule.
    Thus, changes in expectations about the numbers and types of
sources that will need to obtain, install and certify pollution control
equipment to comply with the rule's requirements overall are
compelling. Since the 2004 rule's promulgation, we found that many,
even most, facilities expect to install controls or make other physical
changes to the mill to meet the low-risk criteria. While we recognized
in 2004 that some sources would have to make these changes to become
low risk, we did not predict accurately the number of sources that
would do so. Rather, we expected that sources needing to obtain,
install and certify controls would be primarily those remaining in the
MACT category, such that MACT-subject sources would face comparably
less competition from would-be low-risk sources in seeking available
vendors for those controls under the original compliance deadline of
October 1, 2007. We now have a better understanding that more sources
than we first anticipated in 2004, both MACT and low-risk sources, will
need to install controls and will be competing for the services of a
limited number of control device vendors.
    In addition to the difficulties sources may encounter in installing
controls and testing emissions, before today's final action, some
sources faced uncertainty about whether they were part of the PCWP
source category as defined in the

2004 promulgated NESHAP. We received several requests from sources and
permitting authorities as to the applicability for certain types of
processes such as molded particleboard and curved plywood components.
We determined that many of these sources were part of the source
category, but few had associated control requirements. However, some,
we do not how many, may be required to control emissions (e.g., for a
dryer). These are sources, such as furniture manufacturers, who
believed they were not subject to the MACT standards in 2004. Since
that time, through definitional changes in today's final action and
assistance with applicability determinations, we have provided the
necessary clarifications so that these sources may begin the process of
determining their regulatory obligations, which could include
installation of emissions controls.
    As stated above, we do not generally regard the perceived
``uncertainty'' related to the reconsideration and amendment process as
constituting a sufficient reason in and of itself for revising the
overall compliance date. We note that prior to our issuance of today's
final action, sources were able to begin emissions testing for purposes
of the LRD with little certainty of what the final potentially-revised
emissions testing requirements would be. Furthermore, the entire
content of appendix B to subpart DDDD was under reconsideration. While
this did not affect the effectiveness or applicability of the
originally promulgated requirements pending our rulemaking process, we
have learned that the reconsideration and amendment process did affect
source decisions about whether to comply with the MACT standards or to
apply to join the low-risk subcategory, which, ultimately, caused some
sources to delay decisions about MACT compliance.
    The emissions testing that facilities must complete for purposes of
the LRD involves careful planning (e.g., deciding what process units to
test and for which HAP, selection of test contractors, selection of
test methods, test plan development, etc.) and the expense of such
testing depends greatly on the number of process units and HAP that
must be tested. Many facilities will likely plan and conduct emissions
tests that serve a dual purpose: (1) To determine emissions of the
appendix B HAP for purposes of the LRD, and (2) to determine
uncontrolled emissions levels to identify potential MACT compliance
options (e.g., to identify emissions averaging opportunities or see if
emissions fall below the production-based compliance option) should the
facility decide not to pursue the low-risk option. Facilities may view
it as more economical to conduct testing of multiple process units and
HAP combinations at one time than to repeatedly test individual process
units for a few HAP (e.g., because test methods covering multiple HAP
can be used, and there is less travel expense for test contractors if
multiple tests are completed in one trip). Once onsite stack sampling
is completed, laboratory analysis of the samples must be conducted and
test reports prepared. The emissions testing that PCWP facilities must
conduct, from the planning stage to receiving the final report, can
easily take 9 months to 1 year. More time may be required if the
testing company or laboratory does not correctly perform the tests or
analysis the first time due to the difficulty of some of the test
methods (e.g., relatively new NCASI test methods developed specifically
for the PCWP industry). While adding these methods add flexibility for
sources, sources did not know until today whether the final rule would
incorporate them. We also recognize that the number of testing
contractors with the equipment and familiarity needed to run the NCASI
methods is limited, and that there will be much competition for the
qualified testing contractors. Today's final amendments allow use of
more test methods applicable to the multiple HAP of concern than did
the 2004 final NESHAP (e.g., we are incorporating by reference the new
NCASI method ISS/FP-A105.01), and before today's final amendments
facilities were uncertain which methods would be acceptable. In
addition, today's final amendments allow other emissions determination
approaches such as small-scale kiln testing, fuel analyses to predict
HAP metals emissions, and modeling of tank or wastewater emissions. For
these reasons, many sources have delayed their emissions testing
activities until after today's final amendments are promulgated.
Emissions testing is only one step in completion of the LRD (i.e., it
will take several months to a year or more for PCWP facilities to
complete their LRD incorporating all of the emissions data and to
complete changes to their facility to ensure they can meet the low-risk
criteria on an ongoing basis). Although the changes to the overall rule
are significant and the CAA allows us to set a new compliance date 3
years from the promulgation of today's final rule, we concluded only an
additional 12 months beyond the original compliance date is necessary.
    Comment: Two commenters stated that there is no reason why a source
should not be able to move from the MACT to the low-risk subcategory if
changes occur such that the facility qualifies as low-risk (e.g.,
equipment installation that reduces emissions or any future changes to
the health benchmarks for acrolein and acetaldehyde), even if the
facility qualifies after the MACT compliance deadline. The commenter
stated that although these facilities would have already incurred the
expense associated with MACT control installation, it may still be
worthwhile to be classified as low-risk because of the reduced
recordkeeping and reporting burdens.
    Response: We agree that sources should be able to join the low-risk
subcategory before or after the MACT compliance date. Allowing sources
to become part of the low-risk subcategory after the MACT compliance
date gives facilities more time to complete any physical changes
necessary to operate as low risk, more time to complete their LRD, and
more time to complete their permit applications. Existing sources