**Key Legal Comments Received on Secondary O~3~ NAAQS Review**

(1) *[Comment:]{.underline}* Environmental Defense commented that EPA's
    proposed alternative to set the secondary standards at the same
    level as the primary standard flouts the recommendations of both
    CASAC and Staff, and is scientifically unsupportable. The commenter
    stated that EPA provides no reasoned basis for rejecting CASAC's
    recommendation on this score, and that EPA concedes that the
    cumulative seasonal W126 standard is the most biologically relevant
    way to protect against adverse welfare effects on vegetation.
    Environmental Defense claims that EPA cites no scientific or other
    rational relationship between the proposed primary standards and
    protection of vegetation against adverse welfare effects. Because
    there is no rational connection between the proposed primary
    standards and the level of protection needed to protect vegetation
    against adverse O~3~-induced welfare effects, any EPA finding that
    the primary standards would be sufficient for secondary standards
    purposes would be arbitrary. The most that EPA asserts is that there
    could be significant overlap in the areas protected by the 8-hour
    and W126 forms, and that the proposed primary standards.

> *[Response:]{.underline}* EPA agrees that the W126 form is currently
> the most biologically relevant form available for reflecting
> vegetation response to O~3~ exposures that is also suitable for NAAQS
> standard-setting purposes. In this review, EPA concludes that the
> information on the biological relevance of the form as well as the
> information available for setting the level are such that the
> appropriate standard that is requisite to protect public welfare is a
> standard using the W126 form. However, EPA does not agree that a
> biologically relevant form is a mandatory requirement in setting a
> secondary standard, under all circumstances. Indeed, EPA has a long
> history of judging that a secondary standard set identical to the
> primary standard form and level will be requisite to protect public
> welfare , based on the entire body of information available at that
> time. This judgment has often been made, in large part, as a result of
> the often significant uncertainties that remain regarding what
> combination of form and level are most appropriate for a secondary
> standard, as was the case at the conclusion of the last O~3~ NAAQS
> review in 1997.
>
> In the current review, EPA compared the degree of overlap that would
> occur between areas meeting different levels of proposed 8-hour and
> W126 standard forms. On the basis of this assessment, the Staff Paper
> concluded that "...the degree to which the current 8-hour standard
> form and level would overlap with areas of concern for vegetation
> expressed in terms of the 12-hour W126 standard is inconsistent and
> would depend greatly on the level of the 12-hour W126 and 8-hour forms
> selected and the distribution of hourly O~3~ concentrations within the
> annual and/or 3 year average period" (Staff Paper, pp. 8-19, 8-20).
> Because additional information was available in this review
> regarding 1) selection of an appropriate biologically relevant form
> and 2) the inconsistency that exists from year to year in the degree
> of overlap in areas meeting the 8-hour and W126 forms, EPA was able to
> judge that a standard with a W126 form would be requisite to protect
> the public welfare against adverse effects to vegetation.

\(2\) *[Comment:]{.underline}* Environmental Defense commented that
EPA's proposal to set a W126 secondary standard in the range of 7-21
ppm-hrs unlawfully and arbitrarily departs from CASAC's recommendation
and the supporting science. The commenter stated that the Act and
settled principles of administrative law require EPA to provide a
reasoned justification for departing from CASAC's recommendation with
respect to the upper bound of the proposed W126 standard and EPA has
failed to provide such a justification here. The Agency merely asserts
that "\[g\]iven the uncertainty in determining the risk attributable to
various levels of exposure to O~3~, the Administrator believes as a
public welfare policy judgment that this is a reasonable range to
propose" 72 Fed. Reg. 37,903. The commenter claimed that this bare
assertion is grossly deficient as a basis for departing from CASAC's
recommendation, as described in paragraphs (a) through (c) below.

> \(a\) The commenter asserts that EPA fails to identify its basis for
> claiming uncertainty in determining the risk attributable to various
> O~3~ levels or explain why the degree of alleged uncertainty is so
> great as to render the findings of adverse effects at those levels
> improbable. The agency cites no facts supporting the claim of
> uncertainty and does not explain any rational connection between the
> degree of alleged uncertainty and specified levels of the standard.
> The agency does not show, nor does the record support a finding that
> uncertainty of the evidence of adverse effects at 15 ppm-hours is
> materially greater than at 21 ppm-hours, or that any alleged
> uncertainty of adverse effects at 15 ppm-hours is so great as to
> render adverse effects at that level improbable. To the contrary, the
> record shows that conclusions of a consensus workshop of independent
> scientists that limits below 15 ppm-hours are requisite to protect
> against adverse effects to vegetation. 72 Fed. Reg. 37902/2. Evidence
> in the Criteria Document and analysis in the Staff paper provides
> further support for these consensus recommendations, and indeed the
> Staff found nothing in more recent information to call these
> recommendations into question.
>
> \(b\) EPA does not meet its burden of rationally justifying its choice
> of standards and its rejection of CASAC's recommendation merely by
> asserting that its decision is a "policy judgment." The Criteria
> Document and other evidence in the record support a finding of adverse
> welfare effects on vegetation at W126 levels at and below 15
> ppm-hours. To justify setting the secondary standard at a higher level
> than that, EPA must provide a reasoned justification for disregarding
> or giving limited weight to the studies and scientific findings of
> adverse effects at and below 15, and for rejecting CASAC's
> recommendation.
>
> \(c\) Based on the evidence of adverse welfare effects on vegetation
> from O~3~ levels as low as 7 ppm-hours, EPA must set the secondary
> standard at the lowest end of the range. Section 109 (b)(2) of the Act
> requires EPA to set the secondary standard at a level "requisite to
> protect the public welfare from any known or anticipated adverse
> effects associated with the presence of such air pollutant in the
> ambient air." Because the record documents known or anticipated
> adverse O~3~ welfare effects on vegetation at levels of 7 ppm-hours
> (and even below), EPA must set the standard at or below that level.
>
> *[Response:]{.underline}* EPA disagrees that its decision to propose a
> broader range of levels for W126 is unlawful and arbitrary. Congress
> explicitly recognized that in making judgments about how to use
> uncertain evidence to set standards, the Administrator may not always
> agree with his scientific advisors, s*ee* CAA 307(d)(3), but EPA
> agrees that where the NAAQS differs in any important respect from the
> advice of CASAC, it must provide an explanation of the reasons for
> such differences. EPA fully considered CASAC's advice with regard to
> the range of W126 levels proposed, as is clear from the expansion of
> the original range identified in the second draft Staff Paper (range
> 13 to 21 ppm-hours) to include the lower end of the CASAC recommended
> range (7 ppm-hours), and explained that the level selected within the
> range of 7 to 21 ppm-hrs is largely a policy judgment as to the
> requisite level of protection needed. Specifically, the Staff Paper
> states "In the absence of any information regarding a threshold of
> O~3~ exposures for vegetation, staff recognizes that the level
> selected is largely a policy judgment as to the requisite level of
> protection needed. In determining the requisite level of protection
> for crops and trees, the Administrator will need to weigh the
> importance of the predicted risks of these effects in the overall
> context of public welfare protection, along with a determination as to
> the appropriate weight to place on the associated uncertainties and
> limitations of this information." (EPA, 2007a/b?).
>
> \(a\) With regard to the Commenter's assertion that EPA fails to
> identify its basis for claiming uncertainty in determining the risks
> attributable to various O~3~ levels, EPA refers the Commenter to the
> Staff Paper discussions regarding the nature and scope of
> uncertainties associated with the exposure (Staff Paper, pp.7-34 to
> 7-37), risks (Staff Paper pp. 7-43 to 7-47 for crops; 7-69 to 7-70 for
> trees,) and benefits (Staff Paper, pp. 7-52 to 7-53) assessments as
> well as similar discussions in parallel sections of the proposal
> notice (e.g., 72 FR 37897). The uncertainties associated with each of
> these assessments translate into uncertain levels of risks to
> vegetation for each of the different air quality scenarios evaluated.
> EPA, in being careful to discharge its mandate to provide the
> requisite level of public welfare protection, i.e. sufficient but not
> more than necessary, took into account to the best of its ability, all
> the information it had available to help inform its judgments on
> requisite protection. EPA's intention to do so is clearly articulated
> throughout the proposal notice (e.g., 72 FR 37904/5). EPA notes that
> the uncertainties associated with the exposure and risk assessments
> affect the predictions of risk to vegetation at different levels of
> W126 equally, so they do not, by themselves, make the risks at one
> level of exposure any more or less probable than another. What they do
> show, however, is that at lower and lower levels of O~3~ air quality,
> remaining risks to vegetation appear to decline so that the relative
> risks among the different air quality scenarios can be evaluated
> against each other.
>
> However, in addition to comparing the relative risks of effects
> occurring at any given level, EPA must make a further determination as
> to the significance of those remaining risks to the public welfare and
> at what level those risks could reasonably be considered adverse to
> the public welfare. Thus, it is not only the uncertainty associated
> with reductions in the presence of effects but the uncertainties
> associated with the degree of public welfare impact of those reduced
> levels of effect that must be weighed.
>
> \(b\) Based on the statutory language in the section 109(b)(2) of the
> CAA, EPA notes that Congress clearly envisioned a role for "the
> judgment of the Administrator" in identifying the "requisite level of
> protection" for the public welfare. As stated in the proposal notice,
> "the level selected is largely a policy judgment as to the requisite
> level of protection needed. In determining the requisite level of
> protection for crops and trees, the Staff Paper recognizes that it is
> appropriate to weigh the importance of the predicted risks of these
> effects in the overall context of public welfare protection, along
> with a determination as to the appropriate weight to place on the
> associated uncertainties and limitations of this information." (72 FR
> 37903). Comments received following proposal further helped inform
> EPA's judgments both as to the likelihood of predicted risks occurring
> and potential adversity in the context of public welfare. In
> particular, comments regarding the significance of the uncertainties
> and limitations associated with the exposure and risk assessments, as
> well as the field based data, helped inform EPA's judgments regarding
> how much weight to place on these uncertainties, in reaching a
> decision regarding what level is requisite to protect the public
> welfare.
>
> EPA disagrees that it has not provided a reasoned justification for
> departing from the CASAC recommended range. This justification is
> described in the proposal notice in section IV.E.2.c (72 FR 37902/3)
> and further refined in the preamble to the final rule to take into
> account comments received on the proposal notice. The preamble to the
> final rule states that "\[w\]ith respect to the CASAC's Panel's
> recommended range of standard levels, the Administrator observes that
> the basis for its recommendation appears to be a mixture of scientific
> and policy considerations. The Administrator notes that he is in
> general agreement with the CASAC Panel's views concerning the
> interpretation of the scientific evidence. The Administrator also
> notes that there is no bright line clearly directing the choice of
> level for any of the effects of concern, and the choice of what is
> appropriate is clearly a public welfare policy judgment entrusted to
> the Administrator. This judgment must include consideration of the
> strengths and limitations of the evidence and the appropriate
> inferences to be drawn from the evidence and the exposure and risk
> assessments. In reviewing the basis for the CASAC Panel's
> recommendations for the range of the secondary O~3~ standard, the
> Administrator observes that the CASAC Panel apparently placed
> appreciable weight on the combined science and policy views contained
> in a report from a 1996 consensus building workshop held by a group of
> independent scientists to inform its policy judgments on standard
> levels that would be protective against various types of O~3~-related
> effects. While the Administrator finds the views expressed in that
> report to be relevant and of interest, he does not see in that report
> clear linkages between the underlying scientific information and the
> recommended standard levels. Lacking such linkages, the Administrator
> can find no appropriate scientific basis for deferring to the policy
> judgments reflected in that report. Similarly, in presenting their
> recommendations, the CASAC Panel did not provide clear linkages
> between their interpretation of the scientific evidence, the
> substantial uncertainties associated with that evidence, and their
> recommended range of levels. The Administrator more heavily weighs the
> implications of the uncertainties associated with the scientific
> evidence and with the Agency's vegetation exposure and risk
> assessments than the CASAC Panel apparently does, and disagrees with
> CASAC that the evidence and assessment results appropriately serve as
> a basis for concluding that a level no higher than 15 ppm-hours is
> required for an annual standard with a cumulative, 3-month W126
> standard, or that an even lower level is required for a standard
> averaged over three years.
>
> After carefully taking the above comments and considerations into
> account, and fully considering the scientific and policy views of the
> CASAC, the Administrator has decided to set the level of the secondary
> 3-month, W126 standard at 21 ppm-hours, averaged over three years. In
> the Administrator\'s judgment, based on the currently available
> evidence, such a standard set at this level would be requisite to
> protect public welfare from known or anticipated adverse effects to
> O~3~-sensitive vegetation and ecosystems. A standard set at this level
> provides increased protection compared to the current standard based
> both on the level chosen and the use of a form that is a biologically
> relevant index of O~3~ exposure. In the Administrator's judgment, a
> standard set below this level would not give sufficient weight to the
> important uncertainties and limitations inherent in the current
> available scientific evidence and in the quantitative assessments
> conducted for this review. Taking into account the uncertainties that
> remain in interpreting the evidence, the likelihood of obtaining
> benefits to public welfare decreases with a standard set below this
> level, while the likelihood of requiring reductions in ambient
> concentrations that go beyond those that are needed to reduce adverse
> impacts to public welfare increases. The Administrator judges that the
> appropriate balance to be drawn, based on the entire body of evidence
> and information available in this review, is a standard set at 21
> ppm-hours. On balance, the Administrator believes that a standard set
> at 21 ppm-hours would be sufficient to protect public welfare from
> known or anticipated adverse effects, and does not believe that a
> lower standard is needed to provide this degree of protection. This
> judgment by the Administrator appropriately considers the requirement
> for a standard that is neither more nor less stringent than necessary
> for this purpose and recognizes that the CAA does not require that
> secondary standards be set at a zero-risk level, but rather at a level
> that reduces risk sufficiently but not more than what is necessary to
> protect public welfare from known or anticipated adverse effects.
>
> \(c\) EPA disagrees that it must set the standard at the lowest level
> for which there are known adverse effects. As stated above in (b), the
> CAA does not require that secondary standards be set at a zero-risk
> level, but rather at a level that reduces risk sufficiently but not
> more than what is necessary to protect public welfare from known or
> anticipated adverse effects. EPA further notes that the same effect
> may have different degrees of adversity to the public welfare,
> depending on the intended use of the plant and where it is growing. In
> addition, in concluding that the appropriate range for EPA to consider
> was between 7-15 ppm-hours, the CASAC Panel, as stated in (b) above,
> apparently placed appreciable weight on the combined science and
> policy views contained in a report from a 1996 consensus building
> workshop held by a group of independent scientists to inform its
> policy judgments on standard levels that would be protective against
> various types of O~3~-related effects. However, though EPA found the
> views expressed in that report to be relevant and of interest, as
> stated in section II.B.2.c above, it concludes that these views fall
> far short of providing a scientific basis for determining at what
> level these effects become adverse to the public welfare.

\(3\) *[Comment:]{.underline}* EPA also asks for comment on setting
differing levels of protection for different types of vegetation.
Because EPA has not proposed the specific levels for such a proposal, or
methods for implementing it, the agency cannot pursue it further without
additional notice and comment.

> *[Response:]{.underline}* EPA agrees that should such an alternative
> approach have been chosen, EPA may have needed to issue a supplemental
> proposal providing more detail on a proposed approach. However, since
> the Agency did not choose this path, such a supplemental proposal is
> not necessary.

\(4\) *[Comment:]{.underline}* UARG states in a footnote that "EPA has
previously noted that 'striking anomalies arise in attempting to set
welfare-based air quality standards according to some welfare effects
but not others.' 49 Fed. Reg. 10,408, 10,417 (March 20, 1984). The
Agency did not then resolve how such anomalies should be addressed. Nor
has the Agency ever considered whether and how the beneficient \[sic\]
effects of a pollutant (e.g., protection provided by tropospheric O~3~
against UV-B radiation-related health effects such as cataracts and
melanoma) should be considered in selecting a secondary NAAQS that
differs from the primary one. Should the Administrator decide in this
rulemaking to set a secondary standard different from the primary one,
these are issues that he would be compelled to address.

> *Response:* In the 1984 notice of proposed rulemaking cited by UARG,
> the question as to whether EPA could consider the costs of
> implementation in setting the secondary standard had not been resolved
> by a court. Although EPA explained that the better view of the CAA was
> that EPA could not consider costs in setting the standard, it noted
> that it was uncertain whether a court would reach the same conclusion.
> The "striking anomalies" noted by EPA arose from the possibility that
> EPA could consider the costs of implementation in setting a secondary
> NAAQS. As the Supreme Court has now resolved the issue of whether EPA
> may consider the costs of implementation in setting a secondary
> standard, the Agency need not resolve how such "anomalies" described
> in the 1984 NPRM should be addressed.
>
> In this review, EPA did evaluate a broad array of O~3~-related welfare
> effects for which relevant information was available, including
> various effects on vegetation and natural ecosystems (and related
> components), effects on economic values (related to effects on
> vegetation and ecosystems), effects on climate change, and effects on
> man-made materials. The Staff Paper (Chapters 7-8) and proposal notice
> recognize the full array of welfare-related effects defined in the
> CAA[^1] and note that the O~3~-related effect categories that are of
> most concern at concentrations typically occurring in the U.S. include
> adverse effects on agricultural crops, trees in managed and unmanaged
> forests, and vegetation species growing in natural settings. These
> documents also recognize that O~3~ can affect other ecosystem
> components such as soils, water, wildlife, and habitat, either
> directly or indirectly, through its effects on vegetation, and
> discusses how these individual ecosystem components are associated
> with various essential ecological attributes, as described in a report
> from the Science Advisory Board, *A Framework for Assessing and
> Reporting on Ecological Condition* (2002).
>
> Based on the linkages described in the SAB report, these documents
> recognize that increasing protection for vegetation from O~3~-related
> effects would also improve the protection afforded to ecosystems and
> their related public welfare categories. In addition, these documents
> recognize that (1) O~3~-related damage to man-made materials and the
> economic consequences of that damage are too poorly characterized to
> directly inform standard setting, and (2) although there has been
> research on O~3~-related impacts on climate in recent years, further
> advances in monitoring and improvement in modeling are needed before
> such considerations can inform standard setting.
>
> Thus, quantitative assessments prepared in support of this review
> focus on commercial and natural vegetation, including economic values
> associated with impacts on commercial crops; and qualitative
> assessments focus on ecosystem effects, including evidence of
> potential O~3~-related alteration of ecosystem structure and function
> as well as effects on ecosystems services such as carbon
> sequestration.
>
> The proposal notice (72 FR 37883) stated that "the Administrator
> believes that it is reasonable to conclude that a secondary standard
> protecting the public welfare from known or anticipated adverse
> effects to trees, native vegetation and crops would also afford
> increased protection from adverse effects to other environmental
> components relevant to the public welfare, including ecosystem
> services and function."
>
> Throughout this review EPA has have paid careful attention to the
> broad scope of welfare effects encompassed by the Act. As in all NAAQS
> reviews, whether health based primary standards or welfare based
> secondary standards, the nature and depth of information available
> logically and properly focuses the Agency's attention on those effects
> for which EPA has adequate information to inform a decision on a
> quantitative ambient air quality standard. Focusing our attention
> where there is adequate science to inform decision making should not
> be confused with failure to consider all of the effects for which EPA
> has information, or with failure to provide a balanced consideration.
>
> EPA disagrees that it has failed to "consider[\[ \]]{.mark}?? whether
> or how the beneficient effects of a pollutant . . .should be
> considered in selecting a secondary NAAQS that differs from the
> primary one. The D.C. Circuit decision from the last review made it
> clear that EPA must consider both the beneficial effects of an air
> pollutant as well as its adverse effects, and must asses the net
> impact on public health of a pollutant such as tropospheric O~3~. In
> this review, EPA is not aware of any information indicating any
> beneficial effects of O~3~ on public welfare. In addition, EPA fully
> explored the potential beneficial effect of tropospheric O~3~ with
> respect to UV-b radiation in the context of the primary standard. EPA
> determined that the effect of changes in ground--level O~3~
> concentrations on UV-induced health outcomes, including whether the
> changes in O~3~ would ultimately lead to increases of decreases in the
> incidence of UV-b relate disease, cannot be critically assessed at
> this time (72 FR 37837).
>
> All of the information available to EPA in this review indicates
> otherwise -- O~3~ can damage vegetation, including commercial crops,
> and the adverse health effects from O~3~ clearly indicate that
> exposure to O~3~ is not beneficial to personal comfort and well-being.
> The effects that EPA considers are those attributable to the presence
> of the pollutant in the ambient air. EPA does not consider any benefit
> that could be attributed to avoiding the cost of implementing a
> revised O~3~ NAAQS. Such a benefit is not cognizable as an effect on
> welfare for purposes of setting the secondary NAAQS. The Supreme Court
> agreed with EPA's long standing view that EPA may not consider costs
> of implementation in setting the NAAQS, for either the primary or the
> secondary standard.
>
> Thus a review of the rulemaking shows that EPA has carefully
> considered the wide range of cognizable welfare effects in this NAAQS
> review. EPA has little if any information on certain of the welfare
> effects included in section 302(h). This lack of information certainly
> does not provide a basis to challenge the W126 standard. The lack of
> relevant information could not be used to argue for a more stringent
> secondary standard, nor could it be used to support a standard less
> stringent than that deemed appropriate in light of the effects for
> which we do have information. EPA has comprehensively reviewed and
> assessed all of the scientific information that is available, and the
> Agency has properly focused its attention where the scientific
> information is adequate to inform decision making on the appropriate
> O~3~ NAAQS. EPA has not ignored welfare effects, and the Agency has
> not failed to properly evaluate and balance the information available
> to it.

[^1]: These effects include, but are not limited to, effects on soils,
    water, crops, vegetation, man-made materials, animals, wildlife,
    weather, visibility and climate, damage to and deterioration of
    property, and hazards to transportation, as well as effects on
    economic values and on personal comfort and well-being.