Tag Archives: EPA

EPA’s New Ozone Rule: Part 24

This last post about EPA’s new ozone rule will summarize the topic and will draw some conclusions. We begun with a September 2011 news item that the Obama administration had requested the EPA to withdraw a new proposal to reduce the maximum amount of ground-level ozone in the air:    from 75 ppb to 70 ppb (.075 ppm to .070 ppm)1. This decision stirred controversy with many in the business community praising the President for keeping economic concerns front and center against many in the environmental community claiming that the President had missed an important opportunity to improve air quality2. Our purpose was to determine which side held more weight.

The answer to that question depends a great deal on one’s sense of priorities: is a robust economy more important or is reducing sickness and death from air pollution to a minimum more important? We know that ozone is a respiratory irritant, lethal in high concentrations but damaging even in very low concentrations3. We have ample research that shows higher ground-level ozone concentrations causes more deaths and results in more visits to hospital emergency rooms and missed days from work4. On the other hand, minimizing ozone creation is an expensive proposition. Requiring industry, responsible for most ground-level ozone production, to reduce its ozone contribution is laying on it a heavy regulatory burden that hampers business activity and reduces employment5.

We discussed the origins and chemistry of ground-level ozone and saw why industry would need to bear most of the burden of lowering the standard6. We noted that the new rule actually imposed two standards, a primary standard based on highest averages to protect human health, and a secondary standard based on cumulative exposure to protect property and economic interests, particularly plant life7.

We talked about the damage that ozone does to people and property8, then went on to discuss the history of ozone regulation since 20089. We went into some detail into EPA’s thinking as recorded in government documents, trying to understand why they set the primary standard as .075 ppm in 2008 but .070 only two years later10, and why they originally did not really set a secondary standard but later formulated one on the insistence of CASAC (Clean Air Scientific Advisory Committee)11. We saw that the two administrators, Stephen Johnson under President Bush and Lisa Jackson under President Obama, had access to about the same evidence but came to very difficult conclusions about what was needed to protect the public health and leave an adequate margin for error12. We saw how CASAC strongly objected to not having a separate secondary standard and how they influenced the EPA to adopt such a standard in 201013. We discussed the burden of implementation and touched on the many industries that are effected by tougher ozone rules14. We did a very rough cost-benefit analysis weighing the financial benefits of stricter ozone regulation against its economic costs to society15.

Finally, we discussed how well current ozone rules are being implemented, what areas of the country are not in compliance with the current standard of 75 ppb, and by how much16. We saw that non-attainment of the current EPA standard is confined largely to the East and West Coasts and to major metropolitan areas. Only California has severe problems with ozone, and it has those problem in a large swath through the state. Baltimore and Dallas have moderate problems, and the rest of the country have at most marginal problems with ozone.

So where does that leave us? Should the EPA try to implement a stricter standard at a later date? President Obama himself stated in his September 2011 statement that the ozone standard would be reconsidered in 2013, so perhaps this year we will see a second attempt. But maybe not: Lisa Jackson left the EPA last February, and until the Senate confirms a successor, the EPA will be headed by an acting administrator (Bob Perciasepe). I understand that an acting director does not have the same authority as an administrator confirmed by the Senate, so I doubt that the EPA will adopt a stricter standard until a new Administrator is confirmed (Obama’s current nominee is Gina McCarthy).

I don’t disagree with Obama’s decision to request a retraction. Business opposition to the new rule was strong. He was facing a difficult election and he didn’t need to stir up more opposition than he had to. As we discussed earlier, deciding whether the ozone standard should be at 75 ppb or 70 ppb is largely a judgement call. The lower standard will save lives, increase life expectancy, and relieve illness, but will likely be an economic burden and an impediment to job creation. Reasonable people could take either side of the argument.

I tend to fall on the side of environmentalists. While the regulatory burden is a concern, people and economies adjust over time, as long as burden is reasonable. If a tougher standard was enforced, I think we would see some loss of economic activity and employment. But when regulations are enforced in an intelligent way, people eventually get used to them and learn to work within them. For example, take EPA’s Acid Rain Program, legislated in 1990 as part of the Clean Air Act and put into effect in 199517. The Acid Rain Program is a cap-and-trade program, enabling industries that are able to cut their sulfur dioxide emissions beneath a certain limit to sell the rights to emit the saved sulfur dioxide to other industries. This program may have played a major role in sharply reducing emissions in the U.S.18 People seem to have adjusted to it, with very little vocal opposition that I am aware of. Nobody has blamed the Acid Rain Program for the poor state of the economy.

But the key is that stricter standards must be intelligently enforced with sensitivity to the needs of business; heavy-handed regulation blindly administered with no regards to business can really be a drag on the economy. Not being an expert, I’m not sure how to do intelligent enforcement. However, I understand that Obama’s current nominee for EPA Administrator, Gina McCarthy, is a strong believer in working with business to find the best solutions to environmental problems. If so, she’d be perfect for the job, and I strongly urge the Senate to confirm her as soon as possible.

Yet the stricter standard was scuttled. I think part of the problem is that EPA’s manner can be rather imperious and somewhat patronizing, laying down new regulations without any serious input from other stakeholders. There was a period of public comment to which the agency responded19, but my impression is that the agency merely rebutted criticism rather than try to incorporate people’s concerns into the decision process. Naturally, affected stakeholders are resentful. As it writes a new standard into law, the EPA needs to build cooperation with stakeholders, and that was what was sorely lacking in the process. Everybody’s concerns need to be addressed and it’s important they feel their needs are being addressed.

Moreover, EPA tried to enact the new standard without garnering public support first. When I first learned of Obama’s retraction, I had never heard of the new ozone rule, and I doubt many people did, either. Many people were wondering, what is this bothersome new regulation all about and why is it important? EPA can still win a stricter ozone standard, but to accomplish that it must first raise awareness about the problems of ground-level ozone among the public. It can do this by working with environmental advocacy organizations and patient advocacy organizations (such as the American Lung Association) to build public awareness of ground-level ozone and its effects. Either it or a surrogate can build a major ad campaign to push ozone to the forefront of the national consciousness (how about the slogan “Ozone Kills!”). It can devise educational presentations that schools can use in their classrooms. It can put scientists and researchers on news programs and talk shows. It can have them write articles and op-ed pieces in newspapers and popular magazines. If there is a popular demand for stricter ozone standards, there will be a much better chance that the standards will make it into law.

I’ve wondered how ozone levels affect the performance of players in major league sports, particularly those played out-of-doors (baseball and football especially). If a negative correlation could be proved, we might have major league sports as allies. Players are occasionally accused of taking performance-enhancing drug. What if it could be proved that low-ozone air is a performance-enhancing drug that is perfectly legal?

Also, we need more research into ozone. I mentioned before that very few scientific studies have looked at the effects of 40 — 60 ppb ozone on subjects in the laboratory20. It also seems that there is a dearth of laboratory studies that have had asthmatics and other COPD (chronic obstructive pulmonary disease) sufferers as subjects21. We need more of these studies. We need to publicize epidemiological studies that compare the effects of living in areas of the country with high ozone concentrations with those of lower concentrations to convince people there is a difference, and that it affects them personally.

As for the secondary standard, I’d hold off on that. If the purpose of the secondary standard was to shore up struggling ecosystems and prevent species extinction, it would be worth fighting for. But if its main purpose is to protect property, then why should we be fighting for the concerns of property owners? We ought to educate people as to what a secondary standard can accomplish, but it shouldn’t be our responsibility to try to impose it. That should be for the beneficiaries, home owners, property owners, and farmers to demand. If they lobby EPA for it or if Congress pushes for it, the EPA should consider it. But if no stakeholders think they need such a standard, then we really don’t need it and we shouldn’t be pursuing it. With a world full of environmental threats, we need to choose our battles carefully, and this is a battle not worth fighting. We need to save our time, energy, and effort for where it is more needed.

So those are my conclusions and recommendations, which you can accept or reject as you see fit. Thank you for taking the time to read this topic, and I hope you found it helpful to understand an important public health issue.


  1. Statement by the President on the Ozone National Ambient Air Qualities Standards. White House website. To view, click here.
  2. See my post The EPA’s New Ozone Rule: Part 1. To view it, click here.
  3. See my post The EPA’s New Ozone Rule: Part 7. To view it, click here. See also my blog pages Ozone Excerpts 1, which you can view here, and Ozone Excerpts 2, which you can view here.
  4. For example, see the six papers listed in my post The EPA’S New Ozone Rule: Part 22, which you can view by clicking here.
  5. I admit I’m on very shaky ground here: I haven’t actually seen a scientific study on the economic effects of regulation. Perhaps I’ve bought too deeply into the arguments of conservative Republicans and the Tea Party. But it makes sense that if companies are forced to spend large amounts of money, time, and effort on government regulations, they will have less resources to spend on their business and less money to pay employees. The regulations may be necessary or even vital, but there’s always a cost. Of course, the net cost to the world economy is lessened because money spent on regulation benefits other businesses. The net cost to the U.S. economy is lessened, too, if money spent on conforming to regulations is spent on U.S. businesses.
  6. See my post The EPA’s New Ozone Rule: Part 4, which you can view by clicking here.
  7. See my posts The EPA’s New Ozone Rule: Part 6, which you can view by clicking here, and The EPA’s New Ozone Rule: Part 15, which you can view by clicking here.
  8. See my post The EPA’s New Ozone Rule: Part 7. To view it, click here. See also my blog pages Ozone Excerpts 1, which you can view here, and Ozone Excerpts 2, which you can view here. As for the damage that ozone causes property, I haven’t really discussed that in any depth. However, in Ozone Excerpts 1, see Table 1-2: Summary of ozone causal determination for welfare effects, vegetation, and ecosystem effects. In Ozone Excerpts 2, see Table 2-2: Summary of ozone causal determinations for vegetation and ecosystem effects.
  9. See my post The EPA’s New Ozone Rule: Part 8. To view it, click here.
  10. See my posts The EPA’s New Ozone Rule: Part 10 through Part 14. You can view any of these posts by clicking on the following:     Part 10,     Part 11,     Part 12,     Part 13,     Part 14.
  11. See my posts The EPA’s New Ozone Rule: Part 15 through Part 18. You can view any of these posts by clicking on the following:     Part 15,     Part 16,     Part 17,    Part 18.
  12. For Administrator Stephen Johnson’s view, see my post The EPA’s New Ozone Rule: Part 10 which you can view by clicking here. For Administrator Lisa Jackson’s view, see my posts The EPA’s New Ozone Rule: Part 11, click here to view, and The EPA’s New Ozone Rule: Part 12, click here to view.
  13. See my posts The EPA’s New Ozone Rule: Part 17. To view it, click here.
  14. See my posts The EPA’s New Ozone Rule: Part 20 and Part 21. To view Part 20, click here. To view Part 21, click here.
  15. See my post The EPA’s New Ozone Rule: Part 22. To view it, click here.
  16. See my post The EPA’s New Ozone Rule: Part 23. To view it, click here.
  17. U.S. Environmental Protection Agency website, Clean Air Markets Acid Rain Program. To view, click here.
  18. For example, U.S. Environmental Protection Agency, Acid Rain and Related Programs: 2009 Highlights, 15 Years of Results 1995 to 2009. To review the report, click here.
  19. For example, U.S. Environmental Protection Agency, National Ambient Air Quality Standards for Ozone, July 2011, Section II.C.2. “Comments on the Proposed Decision”, pp. 77 – 163.
  20. See my post The EPA’s New Ozone Rule: Part 9. To view it, click here.
  21. This observation was made from inference. The U.S. Envronmental Protection Agency’s document National Ambient Air Quality Standards for Ozone, July 2011, states (p.38) “The most certain evidence of adverse health effects from exposure to O3 comes from the controlled human exposure studies, as discussed in the 2010 proposal in section II.A.2, and the large bulk of this evidence derives from studies of exposures at levels of 0.080 ppm and above. At those levels, there is consistent evidence of lung function decrements and respiratory symptoms in healthy young adults, as well as evidence of inflammation and other medically significant airway responses.” Later on, the document mentions the Adams studies at the only controlled studies “that examine respiratory effects associated with prolonged O3 exposures at levels below 0.080 ppm.” But the Adams studies only used healthy subjects. Thus, the number of controlled studies using subjects with COPD and other respiratory ailments must be few and far between.

EPA’s New Ozone Rule: Part 8

In 2008, the EPA under George W. Bush reduced the maximum allowable concentration of ground-level ozone from 80 ppb to 75 ppb1. Two years later, the EPA decided to reduce the limit still further to 70 ppb.2. What made the EPA decide to do so in only two years? This was unusual because the Clean Air Act only requires the EPA to review its policy on ozone once every five years, the next review required in 20133. What was the rush?

In April 2008, soon after the EPA lowered the standard, the Clean Air Scientific Advisory Committee (CASAC, EPA’s scientific advisory board on clean air4) sent the EPA a letter strongly disagreeing with the new standard, claiming that the new ozone standard was not low enough to provide a margin of safety. It wanted a primary standard between 60 and 70 ppb. In addition, CASAC felt that a different secondary standard should be established to protect property and the environment. This standard should be cumulative rather than be based on highest average readings5.

A month later, a number of groups challenged EPA’s standards in court. Some of them felt the standard went too far: business interests and some states. Other petitioners felt the standard did not go far enough: environmental organizations, public health organizations, and other states. These lawsuits were consolidated into one: State of Mississippi et al v. U.S. Environmental Protection Agency. In March 2009, the EPA filed an unopposed motion to hold the lawsuit in abeyance while it reviewed the new standard. 6 The revised standard, which lowered the maximum allowable concentration from 75 ppb to 70 pbb, was published in July 20117. In September 2011, the Obama administration requested that the EPA rescind its new standard8.

The document which lays out this new standard, National Ambient Air Quality Standards for Ozone, Final Preamble published July 7, 2011, lays out a detailed explanation of EPA thinking: why it didn’t think 75 ppb was a good enough standard, why 60 ppb was too low and 70 ppb was about right, and why it felt a new secondary standard to protect property and the environment was necessary9. I am going to try to summarize that thinking here.


  1. U.S. Environmental Protection Agency, Integrated Science Assessment for Ozone and Related Photochemical Oxidants, Third External Review Draft, June 2012, p.lxxiii.
  2. U.S. Environmental Protection Agency, National Ambient Air Quality Standards for Ozone, Final Preamble, 2011, p.6.
  3. United States Code, Title 42, Chapter 85, §7409 (d)(1). To view, click here.
  4. The Clean Air Act requires that an independent scientific body review the NAAQS at five-year intervals and make recommendations. CASAC currently fulfils this role. See United States Code, Title 42, Chapter 85, §7409 (d)(2). To view, click here.
  5. U.S. Environmental Protection Agency, National Ambient Air Quality Standards for Ozone, Final Preamble, 2011, p.18.
  6. ibid.pp.29-30
  7. This is the National Ambient Air Quality Standards for Ozone, Final Preamble, 2011 that has been referred to above.
  8. Statement by the President on the Ozone National Ambient Air Qualities Standards. White House website. To view, click here.
  9. U.S. Environmental Protection Agency, National Ambient Air Quality Standards for Ozone, Final Preamble, 2011. The rationale for the primary standard (section II) starts on p. 34 and the rationale for the secondary standard (section III) starts on p. 192.

EPA’s New Ozone Rule: Part 6

Let’s look at EPA’s proposed ozone rule to see exactly what it entails. Unlike previous ozone rules, it has two distinct parts1:

  • A primary standard to protect human life and health.
  • A secondary standard to protect property, agriculture, and the environment.

Technically speaking, EPA rules always had primary and secondary standards, but up to now, the ozone primary and secondary standards were identical2. This is the first time that the two standards were made distinct, done at the urging of EPA’s Clean Air Scientific Advisory Committee (CASAC)3.

The two standards are different in character. The primary standard is based solely on averages4. If the average ozone concentration rises above a certain level, that location is in non-attainment. The secondary standard is based on cumulative exposure to ozone1. It is more focused on the effects caused by long-term exposure to ozone.

The new rule is making an interesting statement: it appears that with regards to human health we are more interested in the acute effects of high exposure. With property and agriculture, we seem more concerned with ozone’s long term effects. Yet the EPA is aware of that long-term exposure to ozone can degrade human health over time.

Now if a locale is to be in attainment, it presumably must meet both the primary and secondary standards. Sometimes one standard will be more stringent, sometimes the other. Consider locales which meet one standard and not the other. In one locale, ozone levels are usually very low. Occasionally, they peek to high levels, just often enough so that the locale does not meet the primary standard, yet the cumulative exposure to ozone remains low. In another locale, ozone levels are consistently high causing large cumulative exposure, but they fall just shy of breaking the primary standard. State and Federal authorities will need to keep track on two sets of numbers for each locale to enforce both standards.

The primary standard in the proposed rule is actually the same as in current rule, just a little stricter, the maximum concentration lowered from 75 ppb in the current rule to 70 ppb. The air is sampled frequently at a measuring station, and readings are averaged out over an eight-hour period. This yields 1,095 such averages in a calendar year (1,098 in a leap year). The three highest averages are thrown out and the fourth-highest average is used to represent the year’s maximum. The maximums from three consecutive years are then averaged together. If this composite average exceeds 70 ppb, that locale is considered in nonattainment1.

The secondary standard is a little more complicated but easily understandable if you remember your high school algebra. The values to be summed are not the ozone concentrations themselves but a calculation based on each reading of ozone concentration, called the W126 index5. To determine, the cumulative index, hourly readings of ozone concentrations are taken at an individual station 12 hours a day, starting at 8 a.m. and finishing at 7 p.m. A value Wi is then calculated as follows:

                                     Wi =        Ci                 
1 + 4403e –ACi


Ci (read as “C sub i”) is the reading of ozone concentration measured in parts per million (ppm) taken at hour i. Because the W126 index is cumulative, Ci is in units of ppm-hours.

e is the base of natural logarithms, approximately equal to 2.71828.
A is a constant equal to 126/ppm-hour.

For example, suppose at 2:00 in the afternoon we measured an ozone concentration of .083 ppm. We would then calculate a W value for 2 pm this way:

             W2pm =                              .083 ppm-hours                   
                                1 + (4403)(e – (126/ppm-hour)(.083 ppm-hours))

This can easily be calculated with the help of a scientific calculator6 (note that the ppm-hours units cancel in the exponent as they should), yielding a value of 0.74 ppm-hours. This means that the ozone concentration at 2 pm will contribute slightly less to the cumulative total than if we did not use the formula (.074 ppm-hours versus .083 ppm-hours).

The Wi values are summed each day, giving a daily cumulative total:

Wdaily = ΣWi

summed from the first reading of the day at 8 am to the last reading at 7 pm.

The Wdaily values are themselves summed over a three-month period. As I understand it, these are running totals: January-February-March, February-March-April, March-April-May, and so on.

W126 = ΣWdaily

summed from the first day of each three-month period through the last day.

Thus, each calendar year produces ten W126 values, from January-February-March through October-November-December. The highest W126 value for the year is selected. This process is carried out for three consecutive years, producing three yearly maximum W126 values. The average of these three values is the final W126 value. If it is higher than 13 ppm-hours, then the area where the readings were taken is declared to be in non-attainment5.

For example, the following are fictitious highest W126 totals summed up during each of 2008, 2009, and 2010. All values are in ppm-hours:

Year Highest Value Period Summed
2008 15.2 Apr-May-Jun
2009 14.3 May-Jun-Jul
2010 12.9 Mar-Apr-May

The average of these three values is 14.1 ppm-hours. Since this is above the standard of 13 ppm-hours, the area from where these readings were taken is in non-attainment.

Why is the W126 index used? To quote A.S.L. & Associates, a Montana company whose founder developed the W126 index:

The W126 index is a cumulative exposure index that is biologically based. The W126 ozone index focuses on the higher hourly average concentrations, while retaining the mid- and lower-level values. By applying a continuous weighting, the W126 index has the advantage of not utilizing an artificial “threshold.”

In 1985, A.S. Lefohn proposed the use of the W126 ozone exposure index for predicting vegetation effects. The cumulative W126 exposure index uses a sigmoidally weighted function (i.e., “S” shaped curve) as described by Lefohn and Runeckles (1987) and Lefohn et al. (1988). The W126 index is a cumulative exposure index and not an “average” value. It is a biologically based index, which is supported by research results (i.e., under both experimental and ambient conditions) that show that the higher hourly average ozone concentrations should be weighted greater than the mid- and lower-level values. The W126 index is accumulated over a specified time period.7

Let’s look again at the equation that defined the individual hourly W126 values, designated as Wi:

                                     Wi =        Ci                 
1 + 4403e –ACi

Let’s plot the Wi values on a graph as a function of the original hourly ozone concentrations that generated them, Ci:

Graph of Wi values plotted against the ozone concentrations used to calculate the values.

As the graph shows, when the ozone concentration Ci is less than .035 ppm-hour, Wi values are negligible. As Ci increases, the Wi values quickly climb, but are still always less than Ci. As Ci increases beyond about .085 ppm-hour, the growth rate of Wi subsides somewhat until about .10 ppm-hour, when Ci nearly equals Wi (within 1%), and the graph becomes linear. This shows that for ozone concentrations less than 0.035 ppm, the W126 values contribute almost nothing to the cumulative total. For concentrations greater than than .100 ppm, the W126 values are almost identical to the ozone concentrations. In between 0.035 ppm and .100 ppm, the contribution varies, with larger concentrations contributing much more to the cumulative total than smaller concentrations.

You can also see this in a table that I prepared of oxygen concentrations in increments of .010 ppm and their corresponding W126 values:

Ozone   Percent of Ozone
Concentration (ppm) W126 Value Concentration
0.01 0.0000 0.08%
0.02 0.0001 0.28%
0.03 0.0003 0.99%
0.04 0.0014 3.39%
0.05 0.0055 11.01%
0.06 0.0182 30.36%
0.07 0.0424 60.59%
0.08 0.0675 84.42%
0.09 0.0855 95.03%
0.10 0.0985 98.54%


  1. U.S. Environmental Protection Agency, National Ambient Air Quality Standards, 2010, pg. 1 and pg. 6
  2. U.S. Environmental Protection Agency website, Ozone (O3) Standards – Table of Historical Ozone NAAQS. To view, click here.
  3. U.S. Environmental Protection Agency, National Ambient Air Quality Standards, 2010, pg. 17.
  4. ibid., pg. 34
  5. ibid., pg. 193.
  6. It is even easier using Microsoft Excel® or similar spreadsheet program. If an ozone concentration in ppm is in cell A1, then this formula typed in cell B1 will give the corresponding W126 value:

    = A1 / (1 + 4403 * EXP(-126*A1))

  7. A.S.L. & Associates website, How the W126 Ozone Exposure Index Was Developed. To view, click here.

Topic: The EPA’s New Ozone Rule Part I

Welcome to the very first topic of this blog, The EPA’s New Ozone Rule. It’s a rather long topic, consisting of 24 posts. If you arrived at this post via a link, you can navigate between posts using the arrows that appear above each post heading. Click on the right arrow (→) to go to the next post. Click on the left arrow (←) to go to the previous post.

On September 2, 2011, the White House released a statement that President Obama had requested the Director of the Environmental Protection Agency (EPA) Lisa Jackson to withdraw a recent EPA proposal to tighten standards for ground-level ozone1.  This proposal would lower the maximum allowable concentration of ground-level ozone from the current standard set in 1997 of 0.08 parts per million (ppm)2 3 to somewhere in a range between 0.060 and 0.070 ppm4.

This change in policy evoked cheers from political conservative and business circles and outrage from the environmental community. Jack Gerard, president of the American Petroleum Institute, was quoted by the newspaper USA Today as saying, “The president’s decision is good news for the economy and Americans looking for work. EPA’s proposal would have prevented the very job creation that President Obama has identified as his top priority.”5 The same article quotes Michael Steel, spokesperson for Speaker of the House John Boehner as saying, “We’re glad that the White House responded to the speaker’s letter and recognized the job-killing impact of this particular regulation.”6 On the other hand, environmentalists were furious. Gene Karpinski, president of the League of Conservation Voters, was quoted by the USA Today article as saying, “The Obama administration is caving to big polluters at the expense of protecting the air we breathe. This is a huge win for corporate polluters and huge loss for public health.”7  Conservatives and business interests, then, see the new rule as an undue burden on business. Environmental groups regard the rule as vital in protecting the public health. Who is correct?

It is possible that both sides have valid points and that the truth lies somewhere between them. I suspect that the rule would place a heavy burden on business, but not as heavy as its opponents make it out to be. Similarly, the rule would probably contribute to public health, although not as critically as its proponents think it will. Perhaps it would be wise to delay implementing the rule, but not to postpone it indefinitely.

I hope in my next postings to analyze the proposed rule, spell out exactly what claims are being made for it, and examine closely the claims of its opponents.


  1. Statement by the President on the Ozone National Ambient Air Qualities Standards. White House website. To view, click here.
  2. National Ambient Air Quality Standards. EPA website. To view, click here.
  3. The 1997 standard is widely quoted as being 0.084 ppm rather than 0.08 ppm. This is because the EPA only demands an accuracy of 0.01 ppm. Therefore, any reading of ozone concentration between 0.075 ppm and 0.084 ppm would be rounded to 0.08 ppm and be considered in compliance. However, a reading of 0.085 ppm would be rounded to 0.09 ppm and would not be considered in compliance. Practically speaking then, 0.084 is the highest reading possible that remains in compliance. See EPA’s March 2008 National Ambient Air Quality Standards for Ground-Level Ozone: General Overview, p. 3. To view, click here. By the way, this is an excellent review of the case against ground-level ozone.
  4. Federal Register Vol. 75 No. 11, p. 2938 Tuesday, January 19, 2010. Docket no. EPA-HQ-OAR-2005-0172. To view, click here.
  5. USA Today, “Obama decides against tougher ozone standards” September 2, 2011, paragraph 14. To view, click here.
  6. Ibid. Paragraph 7
  7. Ibid. Paragraph 26