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Should the NAAQS Be Lowered?

Updated on April 10, 2015

What do you think? Should the NAAQS for ozone be tightened? You know, the NAAQS? You don't recall what those are? Alright, well, no worries. Here are a few hints; I'm sure it will come right back to you.

The What?

You're familiar with the United States' Clean Air Act, correct?


  • Do you recall that it has had 3 major amendments since its implementation in 1963?
  • And, remember that the latest of those three amendments, passed in 1990 under George H. W. Bush, gave greater authority to the EPA in regulating air quality?
  • Six really pervasive pollutants, labeled criteria pollutants, were listed as being the greatest threat to the public and the environment.

And... oh, you got it!

  • The EPA set up primary standards for each pollutant to protect public health, especially very sensitive people like asthmatics or the elderly.
  • Then, secondary standards were established to keep these pollutants from harming us indirectly, such as by limiting our vision. Secondary standards are also used to protect animals, crops, or even buildings.

You're on a roll!

  • In 2014, new primary and secondary standards were announced for ozone, one of the six criteria pollutants.
  • Both the primary and secondary standards were proposed to be set between 0.070 parts of ozone per million parts of total ambient air, or and 0.065 parts of ozone per million parts of total ambient air (or, we could just say 0.070-0.065 "ppm").
  • The standard the EPA finally decides on will be announced in November 2015, and comments were accepted on their proposal until March 17, 2015.

Now you remember!

Some feel that the proposed standard has gone too far; others feel that it hasn't gone far enough, with many in the latter group hoping for a 0.060 ppm rule. A few arguments in favor of that view are explored below.

A representation of a Forced Expiratory Volume measurement chart. For subjects in the study discussed in this paragraph, the rate of change between 0 and 1 on the x-axis (time) dropped considerably with exposure to higher concentrations of ozone.
A representation of a Forced Expiratory Volume measurement chart. For subjects in the study discussed in this paragraph, the rate of change between 0 and 1 on the x-axis (time) dropped considerably with exposure to higher concentrations of ozone. | Source

Respiratory Inflammation

In their final policy assessment for the NAAQS of ozone published in August 2014, the EPA shared the results of several studies on the effects of prolonged ozone exposure to multiple controlled groups of young, healthy adults engaged in moderate amounts of physical activity over a 6.6 hour period2. During the exercise, each group was exposed to a different concentration of ozone via facemask, the lowest being 40 ppb (0.040 ppm) and the greatest 120 ppb (0.120 ppm) (along with a control group exposed to filtered air). Decreases in Forced Expiratory Volume (FEV1; the volume of air an individual can force themselves to exhale under a given period of time (in this case, one second)) positively correlated with concentration of ozone. Each of the analyses of these studies used a different level of statistical significance when interpreting the results. The lowest level of ozone exposure to produce statistically significant inhibitions in lung function (in at least some studies) was 60 ppb, with average FEV1 decreases varying from 1.8% to 3.6%. All of the studies found statistically significant decrements in lung function at 70 ppb, and they uniformly lack any further evidence of significant impact on exhalation with exposure to lower concentrations. To reiterate, only around 60 ppb (not the current 70 ppb standard) did the tests begin to produce negligible results.

But What About the Children?

A cohort of major concern are children, especially those already suffering from respiratory illness. The EPA's Health Risk and Exposure Assessment for ozone contains data from a study that highlighted the impacts of ozone exposure on asthmatic children living in urban locales3. From 2006 to 2010, ozone concentrations of concern were monitored in 15 cities, with the results of the data being adjusted to reflect the currently proposed ozone standard. With the data presented from the study, the current standard is estimated to allow around 14% of the children considered in the study to experience at least one exposure of concern at or above 60 ppb. In other words, almost 2.5 million (14%) of the children residing in these cities will be exposed to air that is 60 ppb ozone. About a tenth of those children are asthmatic. The information collected from Denver, Colorado (one of the fifteen cities under consideration) sits at the high end of this data set, with 17.5% of the children living in Denver estimated to have at least one exposure to an ozone concentration of concern (i.e. for 6.6 hours) at or above 60 ppb. Considering Denver's rapid growth (which has risen considerably even since the end of the study in 2010), the number of children included in the 17.5% will no doubt continue to rise as well.

With a total population of 650,000 (600,000 in 2010), 17.5% of Denver's children are estimated to experience ozone exposures of concern.
With a total population of 650,000 (600,000 in 2010), 17.5% of Denver's children are estimated to experience ozone exposures of concern. | Source
Taken from the EPA's 2014 Health and Risk Exposure Assessment for Ozone.
Taken from the EPA's 2014 Health and Risk Exposure Assessment for Ozone. | Source

In the table above, exposures were estimated for each of the five years between 2006 and 2010 using each of the hypothetical standards listed at the top of the table (and reproduced above the magnified portion). In other words, if the standard had been 75 (or 70, or 65, etc.), then, based on what the exposures actually were for that year under the 80 ppb standard, results were adjusted to simulate what would have happened under the hypothetical standard. As can be deduced (and, rather, inferred intuitively), 60 ppb produced much lower percentages of exposure than any of the other standards. This table focuses on asthmatic children, with the magnified portion highlighting asthmatic children in Houston, the 6th most ozone-polluted city in the U.S. in 2014 (the preceding 5 are all in California).

Test Your Knowledge

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'I Do What I Want'

"For to imprint anything on the mind without the mind's perceiving it, seems to me hardly intelligible."

Indeed, John Locke.

Yet, regularly does this phenomenon occur.

Ozone's ubiquity is made more problematic by the fact that people rarely change their behavior during poor air quality episodes. A 2008 study of randomly selected individuals in Houston, Texas, and Portland, Oregon, showed that only around 10% of those surveyed in either city adjusted their outdoor activities in response to the air quality (despite the fact that both of these cities have significant numbers of environmental activists and environmentally-related educational programs). Ambient concentrations of ozone often find their way indoors, where people are increasingly spending more of their time. In an analysis of data accumulated over 23 years in the United States and Canada, indoor mean ozone levels were shown to have reached ratios as high as 0.51 (in North Carolina; the indoor levels were 51% of outdoor levels)4. Toronto and areas of southern California reached levels of .43, and even certain mountain communities experienced indoor concentrations as high as 36% of ambient levels (although, admittedly, these levels decrease during the nighttime, when individuals are more likely to be spending time inside). While neither of the studies mentioned in this paragraph directly addressed the effects of a specific concentration of ozone on the sample populations, it may be prudent for the United States Environmental Protection Agency to set the standard in such a way as to maximize public health, given the difficulty of reducing ozone exposure on an individual level (suggested by the second study) and the complacence the public often shows toward warnings (evidenced by the first study).

Of course, continuing to refine methods used in motivating citizens to take action couldn't hurt, either.

Signs and warnings seem to have poor efficacy.
Signs and warnings seem to have poor efficacy. | Source

Legal Precedents

42 U.S.C. section 7409(b)(1) explicitly states that the national primary air quality standards should "[allow] an adequate margin of safety"5. Healthy adults engaged in moderate amounts of exercise have displayed adverse reactions after prolonged exposure to ozone at 70 ppb*. For more sensitive populations (such as asthmatics), it could be safely posited that negative impacts would have an even greater likelihood of occurrence. The EPA's Clean Air Scientific Advisory Committee (CASAC) has unequivocally supported a standard within the .060 to .070 ppm (60 - 70 ppb) range. In a 2008 letter to the Administrator, it was the CASAC Ozone Review Panel's "consensus scientific opinion that [the Administrator's] decision to set the primary ozone standard above this range fail[ed] to satisfy the explicit stipulations of the Clean Air Act that [it] ensure an adequate margin of safety for all individuals, including sensitive populations."6 In 2011, CASAC again stated that "the evidence from controlled human and epidemiological studies strongly supports the selection of a new primary ozone standard within the 60 - 70 ppb range for an 8-hour averaging time"7, and, repeated in 2014, "there is clear scientific support for the need to revise the standard"8. The Scientific Advisory Committee has consistently supported a more cautious standard. It is the EPA's duty to be preventive, not reactive, when it comes to public health.

Economic considerations are generally not expected to inordinately influence the setting of air quality standards. In Whitman v. American Trucking Assns., the Supreme Court maintained the view that costs should not be considered when setting NAAQS9. In Am. Petroleum Inst. v. Costle., attainability and technological feasibility were not seen as determinant factors in the creation of said air standards10. 42 U.S.C 7409(b)(1) necessitates that the EPA set standards "requisite to protect the public health"; costs are not the agency's primary focus. 42 U.S.C. 7409(d)(2)(C)(iv) admonishes the Administrator's Committee, to advise the Administrator of "any adverse ... economic effects which may result from various strategies for attainment and maintenance of such national ambient air quality standards". Certain comments made in the final Welfare Risk and Exposure Assessment for Ozone of the economic impacts lend support to the view that a lower standard could be beneficial. To quote the research committee, "Economic welfare impacts resulting from just meeting the existing and alternative standards were largely similar between the forestry and agricultural sectors -- consumer surplus, or consumer gains, generally increased in both sectors because higher productivity under lower W126 index [O3] concentrations increased total yields and reduced market prices."11 To be fair, "comparisons are not straightforward to interpret due to market dynamics," but, it would be reasonable to conclude that lesser strains on lung function could create boons for the industries that rely on outdoor physical labor.

Is 0.070 - 0.065 parts per million ozone an adequate refinement to the current standard?

See results

Naturally, there is a lot to consider when deciding on appropriate air quality standards. How does one interpret the clause, "requisite to protect public health", found in the Clean Air Act? Do we set standards that are good-enough, so to speak, or do we maximize public health and minimize other concerns? How adequate does an "adequate margin of safety" have to be? And, should studies used to support a certain viewpoint be used to sway the public? There are many variables involved in measuring things such as personal ozone exposure or indoor ambient ozone filtration. Atmospheric chemistry itself is a complex field; lowering concentrations of one ozone precursor can lead to a spike in other atmospheric compounds. How can information be presented in a way so that the degree of uncertainty inherent in the data being shown does not undermine the still-present risks of the topic under consideration, and hence possibly discourage the public from acting on the information? Regardless of how one would answer those questions, one thing remains the same.

"NAAQS" is a fun acronym to say, isn't it?

Be Safe!

Ozone accumulates throughout the day as sunlight becomes more intense. Try scheduling your runs in the morning or in the evening.
Ozone accumulates throughout the day as sunlight becomes more intense. Try scheduling your runs in the morning or in the evening. | Source


  1. "Most Polluted Cities." State of the Air 2014. American Lung Association, n.d. Web. <>.
  2. "ADEQUACY OF THE CURRENT PRIMARY STANDARD." Policy Assessment for the Review of the Ozone National Ambient Air Quality Standards (2014): 117-19. United States Environmental Protection Agency. US EPA, 29 Aug. 2014. Web.
  3. "CHARACTERIZATION OF URBAN-SCALE HUMAN EXPOSURE." Health and Risk Exposure Assessment for Ozone: Final Report. N.p.: n.p., n.d. 166-68. United States Environmental Protection Agency, 29 Aug. 2014. Web.
  4. "EXPOSURE TO AMBIENT OZONE." Integrated Science Assessment for Ozone and Related Photochemical Oxidants. N.p.: United States Environmental Protection Agency, n.d. 393-402, 426-427. Feb. 2013. Web.
  5. "42 U.S. Code § 7409 - National Primary and Secondary Ambient Air Quality Standards." 42 U.S. Code § 7409. Cornell University Law School, n.d. Web. <>.
  6. "Clean Air Scientific Advisory Committee Recommendations Concerning the Final Rule for the National Ambient Air Quality Standards for Ozone." CASAC Recommendations Concerning the Final Rule for the NAAQS for Ozone (EPA-CASAC-08-009) (2008): 2. Yosemite EPA. U.S. Environmental Protection Agency, 7 Apr. 2008. Web.
  7. "Clean Air Scientific Advisory Committee (CASAC) Response to Charge Questions on the Reconsideration of the 2008 Ozone National Ambient Air Quality Standards." (2011): 2. 30 Mar. 2011. Web.
  8. EPA Science Advisory Board (SAB). "CASAC Review of the EPA’s Second Draft Policy Assessment for the Review of the Ozone National Ambient Air Quality Standards." June 26, 2014 EPA-CASAC-14-004 The Honorable Gina McCarthy Administrator U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N.W. Washington, D.C. 20460 Subject: CASAC Review of the EPA’s Second Draft Policy Assessment for the Review of the (2011): 5. Yosemite EPA. United States Environmental Protection Agency, 26 June 2014. Web.
  9. WHITMAN v. AMERICAN TRUCKING ASSNS., INC., 175 F.3d 1027 and 195 F.3d 4. Section II par. 2 (2001)
  10. American Petroleum Institute v. M Costle & Ei. 609 F2d 20 pars. 1, 13 (1979)
  11. "SUMMARY OF ANALYSES AND SYNTHESIS OF RESULTS." Final Welfare Risk and Exposure Assessment for Ozone. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air and Radiation, Office of Air Quality Planning and Standards, Health and Environmental Impacts Division, Risk and Benefits Group, 2014. 267-68. United States Environmental Protection Agency, Aug. 2014. Web. <>.
  12. Locke, John. "An Essay Concerning Human Understanding." An Essay Concerning Human Understanding. N.p., 1689. Web. <>.
  13. "National Ambient Air Quality Standards." EPA. Environmental Protection Agency, n.d. Web. <>.
  14. "U.S. National Ambient Air Quality Standards Policy Assessment." (n.d.): n. pag. United States Environmental Protection Agency, 2014. Web. <>.

© 2015 F S Miller


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