The History of Air Quality in Utah: A Narrative Review

Round 1

Reviewer 1 Report

The manuscript “The History of Air Quality in Utah: A Narrative Review” by Logan E. Mitchell and Chris A.B. Zajchowski is a narrative review that describes the history of the relationship between air pollution and Utah’s residents from late 1800s to the present. It is an interesting account of the main events that drove public concerns and air pollution research during that period. The manuscript is well written and provides a useful case study for other regions struggling with air pollution. Once the following aspects are addressed, I recommend the publication of the manuscript.

·         Line 121 “Attitudes about how to address air pollution in the late 1800’s are similar to those in the State today.” This is a misleading generalization statement, as the attitudes in these periods are not directly compared by the authors. The information compiled for the late 1800’s was obtained from a small batch of opinions by reporters and newspaper editors. However, nowadays the attitudes about how to address air pollution can more broadly be accounted for using dedicated surveys. In addition, opinions can include inputs from concerned citizens but also efforts from the scientific community, government agencies, community advocacy groups, NGOs, etc.

·         Line 105. Analyzing objectively the comment itself, there is nothing of a prescient nature (i.e., knowledge of events before taking place) in the paragraph of lines 101-104. The paragraph reads more of a self-evident comment.

·         Can the authors present information (e.g., time series) on population growth, vehicle fleet, fuels consumption, etc. and discuss it in the context of what is known on millstone changes in Utah’s air quality trends? Even if presented in general terms, such information will provide valuable insights to understand the drivers of air pollution in the region.

·         Can the authors briefly describe what is known of the contribution of local versus regional emission sources of pollutants to air quality levels in Utah?

·         Line 607. Note that the high ozone concentrations are indeed correlated to higher temperatures but not (primarily) because of a “speed up these chemical reactions”. It is true that oxidation reactions generally increase with temperature (thus the common assertions for expected ozone increases in warmer temperatures in a climate change context). However, the sensitivity of the rate coefficients is not particularly high in the typical ranges of temperature changes in the urban atmosphere. Instead, the sensitivity of ozone formation is way higher to changes in the availability of UV radiation for the photolysis of NO2 to produce the atomic oxygen that eventually forms ozone. It just happens that UV availability typically correlates positively with ambient temperature.

·         Lines 106-107. Please clarify if indoor air pollution is still major concern in Utah.

·         Can the authors present similar data as in Figure 2, but for Utah? Such information would be valuable to understand the relationships of changes in fuel consumption and changes in air quality in Utah.

·         Lines 558-562. This is an important statement that warrants further discussion. As it reads, it can be misinterpreted as if nothing has changed in the interim period. It may be true the assertion that current policies for improving air quality are, in general, still focusing on similar emission source sectors and control strategies than 30 years ago. However, it can also be argued that source characteristics (e.g., fuels, technologies, etc.) have been continuously changing and that strategies (including regulations) are in continuous need of more sophisticated designs.

Minor:

·         To highlight the impacts of high mountain / low valley terrain, consider adding topographic contour lines or color-scaled terrain features to Figure 1.

·         Lines 191-292. Add reference for this statement.

·         Line 242. 1920 instead of 2020?

·         Replace the word “today” in line 168 by “nowadays”, “recent”, or something similar.

·         Can the resolution of Figure 6 (left side) be improved?

·         For comparison purposes to Table 1, can the authors add another table of the current NAAQS values and a recent number of annual exceedances?

Author Response

Please see the attachment. Thank you for your review.

Author Response File: Author Response.pdf

Reviewer 2 Report

As a narrative review, the manuscript is well written, and therefore I suggest for publication. There is just a minor comment regarding Fig. 2. Please replace it with the case for Utah state since the whole paper is talking about Utah instead of the US.

Author Response

Please see the attachment. Thank you for your review.

Author Response File: Author Response.pdf

Reviewer 3 Report

This article is original and very interesting. As explained by the authors, Utah has its own history related to air pollution. However, it is not widely known or documented, what has changed from now owing to the work of the authors. As it is a narrative review and I am not a Utah air pollution expert, I have no additional comment. 

Author Response

Please see attachment. Thank you for your review.

Author Response File: Author Response.pdf