编者注：Here are answers to some questions aboutthe recent announcement by the U.S. Environmental Protection Agencyregarding a proposed revision to the National Ambient Air Quality Standard (NAAQS) for ozone fromDr. H. Christopher Frey, Distinguished University Professor at North Carolina State University and chair of the EPA’sClean Air Scientific Advisory Committee。
The answers provided here are Dr. Frey’s personal views, and they do not represent any official position of EPA or the EPA Clean Air Scientific Advisory Committee (CASAC).
What is a NAAQS?
NAAQ是国家环境空气质量标准。这些是旨在保护公众免受不良健康影响免受常见但有害空气污染物的不利影响的国家标准。也有国家空气质量标准可以保护“公共福利”免受空气污染的其他损害，例如对生态系统的损害。
More specifically, Section 108 of the Clean Air Act requires the EPA Administrator to identify and list certain air pollutants that, in the Administrator’s “judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare” and “the presence of which in the ambient air results from numerous or diverse mobile or stationary sources.” Furthermore, these standards must “accurately reflect the latest scientific knowledge.”
EPA管理员如何决定旨在保护公共卫生的NAAQS？
《清洁空气法》规定，必须根据“管理员的判断”设置NAAQ，以允许“足够的安全余地”，并是“保护公共卫生的必要条件”。EPA和联邦法院（EPA和联邦法院）解释了“安全边距”一词，目的是解决不确定性并提供合理的保护程度，但不一定为所有个人提供零风险。EPA在做出有关“适当安全余量”的决定时，通常考虑到健康影响的性质和严重性，敏感人群的风险和不确定性的敏感人群的规模以及程度。
Does EPA take cost into account when setting a NAAQS?
No. It is illegal for EPA to take cost into account when setting a NAAQS. The Clean Air Act specifies that the NAAQS must be set to protect public health and public welfare (e.g., ecological impact). In Whitman v. American Trucking Associations in 2001, the U.S. Supreme Court ruled that in setting a NAAQS, the EPA may not consider the costs of implementing the standards.
What is ozone?
Unlike oxygen, which contains two oxygen atoms, ozone contains three oxygen atoms. Ozone is much more chemically reactive and for this reason it can cause adverse effects when it comes into contact with the human respiratory system. It can also cause problems for other living systems, such as plants.
Where does ozone come from?
大气中的臭氧形成的结果ther air pollutants, particularly nitrogen oxides and organic compounds. Nitrogen oxides are emitted from combustion of fuels by power plants, cars and many other sources. Organic compounds are emitted by combustion and also from evaporation of fuels, solvents, paints, and other types of coatings. For example, when you smell “gasoline” at the gas station, you are smelling organic compounds. Nitrogen oxides and organic compounds react in the presence of sunlight to produce ozone.
Why is ozone a problem?
Ozone causes damage to human health. Exposure to ozone for relatively short periods of time (e.g., 8 hours) at high enough levels leads to reduction in lung function, pulmonary inflammation, respiratory symptoms and illness, and premature mortality. People with asthma, children, the elderly, and outdoor workers are among groups of people who are either particularly exposed to ozone, more likely to suffer adverse effects, or combinations of both. The scientific evidence supporting these findings includes clinical studies, epidemiologic studies and toxicological studies.
What is CASAC?
CASAC is the Clean Air Scientific Advisory Committee. CASAC provides independent advice to the EPA Administrator on technical bases for National Ambient Air Quality Standards (NAAQS). CASAC was established under the Clean Air Act (CAA) amendments of 1977. In particular, Section 109(d)(2) of the Clean Air Act requires that an independent scientific review committee “shall recommend to the Administrator any new… standards and revisions of existing criteria and standards as may be appropriate.”
CASAC is comprised of seven members appointed by the EPA Administrator. These members include experts from outside the EPA in topics such as air quality, health effects, ecological effects and risk assessment methods. The seven-member CASAC is supported by panels for each NAAQS review that are augmented with additional experts. The Ozone Review Panel is composed of the seven members of CASAC plus 13 additional experts representing a wide range of disciplines needed to assess the scientific basis of the NAAQS.
CASAC is subject to the Federal Advisory Committee Act (FACA), which means that CASAC members and panelists are subject to a variety of ethics rules, and CASAC must conduct its work in public.
What was CASAC’s advice to EPA on the current NAAQS for ozone?
With regard to the standard to protect human health, CASAC concluded that there is “adequate scientific evidence to recommend a range of levels for a revised primary ozone standard from 70 ppb to 60 ppb.” In its June 26, 2014 letter to the EPA Administrator, CASAC advised that “based on the scientific evidence, a level of 70 ppb provides little margin of safety for the protection of public health, particularly for sensitive subpopulations” and further stated that “Although a level of 70 ppb is more protective of public health than the current standard, it may not meet the statutory requirement to protect public health with an adequate margin of safety.” Thus, CASAC advised the Administrator “to set the level of the standard lower than 70 ppb within a range down to 60 ppb.”
CASAC还提供有关修订NAAQ的福利效应的建议。CASAC确定了暴露于臭氧的生态系统损害的关键类型，包括“与生态系统服务，食物和纤维产品有关的不利福利效应，以及农作物的食物和纤维产品，以及对叶面损伤的资源使用损害。”CASAC建议EPA采用新的“指标”，以根据典型的植物生长季节估算生态系统暴露于臭氧。具体而言，CASAC建议使用称为“ W126”的索引，该索引基于上午8点至晚上8点之间的三个月时间的环境臭氧水平ppm小时至15 ppm小时。
How did CASAC reach that conclusion?
The process by which CASAC developed its scientific and policy advice regarding the NAAQS for ozone is lengthy. In general, the process includes preparation by EPA staff of a sequence of detailed technical reports which are reviewed by CASAC in an iterative multi-year process. Based on this review process, both EPA staff and CASAC develop recommendations to the Administrator regarding whether the current NAAQS is adequate and, if not, regarding how the NAAQS should be revised. CASAC concluded its review of the ozone NAAQS with advice delivered to the Administrator in a June 26,2014 letter regarding recommendations for revising the ozone NAAQS. The key steps in CASAC’s review process include the following:
- In December 2009, CASAC provided comments to the EPA Administrator on a draft plan from EPA regarding how EPA proposed to conduct the scientific review of the ozone NAAQS (EPA-CASAC-10-004).
- In June 2011, CASAC provided comments to the EPA Administrator regarding EPA’s draft plan for how it would conduct exposure and risk assessments for human health and for public welfare adverse effects (EPA-CASAC-11-008).
- In August 2011, CASAC provided a detailed review of the EPA’s first draft of the Integrated Science Assessment (ISA) for Ozone (EPA-CASAC-11-009).
- 2012年3月，CASAC对EPA综合科学评估的第二次草案（EPA-CASAC-12-004）进行了详细评论。CASAC对第二次草案不满意，并建议EPA提供ISA的第三稿以供进一步审查。
- 2012年11月，CASAC对综合科学评估的第三次草案进行了详细的审查，并得出结论，在完成建议的修订后，“ ISA将为风险和敞口评估和政策评估文件的科学良好基础，以实现科学良好的基础。臭氧国家环境空气质量标准（NAAQS）评论。”
- 还在2012年11月,CASAC提供一个详细的review of EPA’s draft exposure and risk assessments for both human health and public welfare adverse effects. CASAC found that these first drafts were “works in progress.”
- 还在2012年11月,CASAC提供一个详细的review of the EPA’s first draft of the Policy Assessment (PA), which contains EPA staff recommendations for consideration by the Administrator. CASAC found that “that the PA needs substantial improvement.”
- 在时间差距很大之后，CASAC收到并审查了有关人类健康和公共福利以及政策评估的风险和暴露评估的第二稿。CASAC在2014年6月至2014年7月的一系列信中完成了有关第二次接触和风险评估草案的详细审查，并提供了有关人类健康和公共福利的科学和政策建议。
因此，从2009年到2014年的CASAC审查过程跨越了近五年，并在此期间从CASAC到EPA管理员提供了10份单独的报告。
All of CASAC’s deliberations took place in public meetings that were announced in the Federal Register. Public comments were invited at all meetings. Several of the meetings were conducted face-to-face in the Research Triangle Park, NC, area, while others were conducted by teleconference.
Is EPA required to act on CASAC’s advice?
《清洁空气法》授予管理员酌情决定对NAAQ的决定。《清洁空气法》要求一个独立的科学小组向管理员提供有关NAAQ的建议，但并不具体要求管理员遵循建议。实际上，如果管理员不遵循CASAC建议，则通常将脱离CASAC建议的原因作为最终规则的一部分。美国上诉法院2013年对华盛顿特区巡回法院的裁决意味着，CASAC应明确将科学建议与政策建议区分开来，并且EPA的负担证明与CASAC咨询的辩护是关于科学问题而不是政策问题的强大。但是，CASAC并未无法提供政策建议。在NAAQ下对每种污染物的最新审查周期中，有一些例子遵循CASAC的建议和示例，管理员没有。CASAC没有也不能设置NAAQ。只有管理员才能设置NAAQ。
The Administrator’s proposed rule is consistent with CASAC advice for the public health standard, but deviates from CASAC advice for the public welfare standard. For the public welfare standard, the Administrator is considering a range of W126 values outside the range recommended by CASAC and is proposing to set the public welfare standard at the same level as the public health standard, rather than to follow CASAC’s advice to use the biologically relevant W126 index.
How often do EPA and CASAC review a NAAQS?
The Clean Air Act requires that “at 5-year intervals… the Administrator shall complete a thorough review of … the national ambient air quality standards… and shall make such revisions in such criteria and standards and promulgate such new standards as may be appropriate.” The review schedule for a NAAQS is set by EPA. The schedule for the current review cycle for the ozone standard slipped. In April 2014, the Northern District of California of U.S. District Court ordered EPA to issue its proposed decision on revising the ozone standard by Dec. 1, 2014 and to finalize the rule by Oct. 1, 2015.
NAAQS会每五年改变一次吗？
Not necessarily. CASAC will recommend revisions to an existing NAAQS if there is scientific evidence to warrant such a recommendation. In the previous review cycle for the ozone standard, completed in 2008, CASAC regarded that the NAAQS for human health should have been set between 60 ppb and 70 ppb, and the EPA Administrator at that time chose to set the standard at 75 ppb. The scientific evidence in the most recent scientific review is stronger and more complete than in the previous review. CASAC’s current recommendation is that the standard should be less than 70 ppb and as low as 60 ppb, which is similar to the recommendation from the previous review cycle. Thus, had the standard been set within the range recommended by CASAC in the previous review cycle, it is possible that little to no change would be countenanced in the current review cycle.
在达标的情况下,最近的CASAC review concluded that the current standard for lead is adequate and recommended that no revision be made. Thus, it is clearly not the case that a 5-year review cycle implies that a standard must change every 5 years.
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