Air Pollution Effects on Mental Health Relationships: Scoping Review on Historically Used Methodologies to Analyze Adult Populations

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The author reviewed the effects of air pollution on mental health relationships. The topic is also interesting. This is a good review paper. The reviewer recommends a minor revision of this manuscript before its publication.

General comments:

Abstract

·         Line 11: Replace percent with “ %”.

·         Line 16: Replace PM with “Particulate matter (PM)” whenever you use it the first time.

·         Line 33: What is MH? Mental Health?

·         Line 142: there are some reviews. Not exactly like yours. However, these authors did a review on a similar topic. I think it's good to acknowledge those reviews.

o   Zundel, Clara G., Patrick Ryan, Cole Brokamp, Autumm Heeter, Yaoxian Huang, Jeffrey R. Strawn, and Hilary A. Marusak. "Air pollution, depressive and anxiety disorders, and brain effects: a systematic review." Neurotoxicology 93 (2022): 272-300.

o   Buoli, Massimiliano, Silvia Grassi, Alice Caldiroli, Greta Silvia Carnevali, Francesco Mucci, Simona Iodice, Laura Cantone, Laura Pergoli, and Valentina Bollati. "Is there a link between air pollution and mental disorders?." Environment international 118 (2018): 154-168.

o   Lu, Jackson G. "Air pollution: A systematic review of its psychological, economic, and social effects." Current opinion in psychology 32 (2020): 52-65.

·         Table 2: Whenever you use AQ for the first time write the word as “Air quality (AQ)”. Same for MH.

·                  According to your table 2, you exclude the indoor air quality. Is there any reason for this? Indoor air pollution can be more harmful to health than outdoor air pollution because people spend most of their time indoors. According to US EPA, indoor air pollution levels can be 2-5 times higher than outdoor levels, sometimes up to 100 times worse. Also, biomass burning inside kitchens (traditional cooking stoves mainly in Asian countries) is a major source of indoor air pollution and can have serious health effects. I think it's good to include indoor air pollution.

·        It would be nice if you can subdivide Asia into North, Central, West, South, and East Asia because Asia is the most pouted region in the world, and in 2019, 98.8% of people in South Asia (the most polluted region of all) breathed unhealthy air.

·        Line 289: would you please explain a bit about your notation “n=15/51.72%”

15 represents the number of studies in Asia and 51.72% is the ratio of the number of studies to the total number of studies.?

·         Line 805: Per your knowledge, what is the reason for the lack of studies in North America, Africa, and South America? Is it because of the lack of air quality monitoring stations in countries in Africa and South America? But what’s the reason for North America?

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Dear Reviewer,

Thank you very much for taking the time to review my work. I appreciate your careful and straightforward comments and recommendations for corrections. 

I agree with all your comments. Please find the detailed responses below and the corresponding revisions/corrections highlighted in the re-submitted file.

• Line 11 - Changed to "%".
• Line 16: Replaced “PM” with “Particulate matter (PM)”.
• Line 142: I added recommended reviews and other works, which can now be found in Line 150.
• Table 2: “Air quality (AQ)” – added in Line 18.
• “According to your table 2, you exclude the indoor air quality. Is there any reason for this? Indoor air pollution can be more harmful to health than outdoor air pollution because people spend most of their time indoors. According to US EPA, indoor air pollution levels can be 2-5 times higher than outdoor levels, sometimes up to 100 times worse. Also, biomass burning inside kitchens (traditional cooking stoves mainly in Asian countries) is a major source of indoor air pollution and can have serious health effects. I think it's good to include indoor air pollution.” – Yes, I agree with this comment. I explained in the Abstract that this review will focus on outdoor PM to clarify it. We are focusing on outdoor PM primarily in this review as outdoor air pollution is a significant global concern with widespread impacts on populations and ecosystems. Indoor air pollution could be incorporated into another study in conjunction with outdoor PM or as an entirely different study focusing only on indoor air quality. Additionally, I believe this study fits perfectly in my PhD thesis, in which I analyze ambient PM and MH disorders.
• Subdividing Asia: Yes, I agree. I did not go into too much detail but added some information regarding China, as it is the country in Asia with the most studies produced, per the review. No Southern countries were found in the review, so this information has not been added. However, if necessary, it can be investigated in more detail. Overall, changes were added (Line 393 onwards).
• Line 286 – I explained this in Line 308. Yes, the “n” represents the number of Asian countries, followed by the overall percentile proportion of the studies in this review (29 studies = 100%). The breakdown of countries and the number/percentages of the studies were explained in the following lines.
• Line 805: This is explained in more detail in Line 829. This has been changed since a North American study was included in the review.

Reviewer 2 Report

Comments and Suggestions for Authors

This paper is a review that links air quality and mental health outcomes based on previous studies (29 suitable studies were selected from 3891 potential studies).

This is very important research since it highlights the critical need to study air pollution health effects and not only for vulnerable groups of people.  

Major comments

-Ln.11. “Ninety per cent of the global population is exposed to toxic air pollution”. This is a very strong statement in the abstract that needs to be referenced or it should be re-phrased.

-The conclusion section needs more “results” to support the statements (e.g., list research gaps and that population need to be included, what quantitative methods are strongly recommended to be used based on this review).

-Under “limitations” section more discussion is needed not only on the link between PM and MH , but also “Ozone vs. MH”, “VOCs vs. MH”, etc. This discussion should be supported with references on specific pollutants’ health effects.

Some minor comments:

Ln 5. Numbers next to the names should be in superscript format.

Lines 16, 22, 32, 33, 66, 811, 830: abbreviations are not explained

Ln 22, “Fine” should not be capitalized and use symbol for micro units

Ln 28, NOx, NO2, SO2, O3 (use subscripts)

Lines 51, references are missing

Ln 97 explain what is PM2.5.

Ln 100. Explain what is PM10.

Lines 109-110 (explain it above Ln 97 and 100)

Line 145, references of webpages of these databases are missing

Table 3. In the table caption explain all used in the table abbreviations (e.g. WHO)

Tables: some columns in the tables need adjustment

In the text extra spaces are present (e.g., Ln 378)

Ln 465, explain EPA abbreviation

Ln 693. Use “These data” not “this data”

Ln 705, what is “GDPR limit”?

Ln 817, use (SES) after “status”

Ln 855, “The” should not be capitalized.

Comments on the Quality of English Language

This is a very good and well written manuscript

Author Response

Dear Reviewer,

Thank you very much for taking the time to review my work. I appreciate your careful and straightforward comments and recommendations for corrections. 

I agree with all your comments. Please find the detailed responses below and the corresponding revisions/corrections highlighted in the re-submitted file.

• Line 11: I agree. This has been removed from the abstract, and I included this in the introductory section instead with citations.
• Conclusion: I agree with this. I have added more details but kept it still relatively short. I hope this is better.
• Limitations: Thank you. I agree. I added this in Line 862.
• Line 5: Changed.
• Lines 16, 22, 32, 33, 66, 811, 830: The abbreviations are not explained—explained.
• Line 28: Changed. I also found more of these later, which were also changed.
• Line 51: References added.
• Line 97: Explained
• Line 100: Explained
• Line 145: I was unsure about this but added the references. I hope it looks okay.
• Table 3: I added this information in the caption.
• Line 465: Explained
• Line 693: I was unsure where this was, as I am guessing the document format has changed, and the lines did not align correctly as per your comments. I have changed this; I hope this was the right line.
• Line 705: There is no GDPR limit. “Limit” was changed to “restrict” to make it clearer. I was trying to say that GDPR restricts researchers from using people’s personal information, which is deemed to be sensitive information.
• Line 817: Changed
• Line 855: Changed.

Thank you again for your time!