Risk Perception of Air Pollution: A Systematic Review Focused on Particulate Matter Exposure

Round 1

Reviewer 1 Report

The authors indicate that they are presenting a systematic review on the association between exposure to particulate matter and risk perception related to particulate matter. While this might be an area that needs further elucidation, there are several limitations to the manuscript. Overall the manuscript seems to be unfocused, without clear indication to the reader the motivation for the primary research question nor exactly what the authors intend to present. The introduction is extremely dense and presents too much information, much of which seems to not be suitably relevant to the data that the authors are able to abstract. This information may be more appropriate summarized in a discussion section. The reader is left a bit confused about the purpose of the manuscript and what type of results to expect. Further, the authors do not do a sufficient job of presenting the results that they abstracted from their literature review, and spend too much time describing studies but in a level of detail that does not include results. The authors do not synthesize the research they are conducting for the reader, they are instead just listing studies and what the studies found, or more frequently, what the articles did (methods instead of results). Overall the article is not well focused, and there are major issues with language, editing, and readability. Further, the authors have presented their tables results in an Excel file, which is not suitable for a manuscript and which appears to just be their abstraction table (instead of a synthesis of the results in paper-ready format).

Author Response

Reviewer 1

The authors indicate that they are presenting a systematic review on the association between exposure to particulate matter and risk perception related to particulate matter.

While this might be an area that needs further elucidation, there are several limitations to the manuscript.

1. Overall the manuscript seems to be unfocused, without clear indication to the reader the motivation for the primary research question nor exactly what the authors intend to present.

Answer:

Thank you for your comment. We hope to clarify and focus the objective of the systematic review opening the Introduction with the objectives in the first sentence, as follows:

Lines 39-49 - “This systematic review is dedicated to clarifying the role of the perception of risk of air pollution, due to its relevance in the environmental and health field. The goal is to explore studies that analyse people’s perception, together with the measurement of air pollution, in order to elucidate the relationship between them. The focus is on particulate matter (PM), as its negative health effects have been demonstrated and quantified. Social, cultural, and contextual factors can influence people’s perception, and the impacts on behavior, agency, self-efficacy, and the relationship with measured pollution should be clarified. This knowledge could be crucial to complementing studies on the health impacts of air pollution and improving decisions aimed at reducing human exposure. Moreover, recognizing the importance that perception holds in studies on Covid-19 [1] and its complex relationship with air pollution, this topic should be addressed and specifically investigated [2] “

2. The introduction is extremely dense and presents too much information, much of which seems to not be suitably relevant to the data that the authors are able to abstract. This information may be more appropriate summarized in a discussion section. The reader is left a bit confused about the purpose of the manuscript and what type of results to expect.

Answer:

Thank you for your comment. We reduced the introduction simplifying some part and including part of it in the discussion paragraph. Modified parts in the Introduction section and in the Discussion section are in blue print.

3. Further, the authors do not do a sufficient job of presenting the results that they abstracted from their literature review, and spend too much time describing studies but in a level of detail that does not include results. The authors do not synthesize the research they are conducting for the reader, they are instead just listing studies and what the studies found, or more frequently, what the articles did (methods instead of results). Overall the article is not well focused, and there are major issues with language, editing, and readability.

Answer:

Thank you for your comment. The description of the Results and the Discussion section have improved by referring to the table, which has been made more readable and included in the text.

The English was sent for proofreading

The sentences we modified or added to improve the Results section have been highlighted in blue print. The objectives of our review were clarified at the beginning of the Introduction section.

4. Further, the authors have presented their tables results in an Excel file, which is not suitable for a manuscript and which appears to just be their abstraction table (instead of a synthesis of the results in paper-ready format).

Answer:

Thank you for your comment. The table was substantially modified and included in the text in Word format.

Author Response File: Author Response.pdf

Reviewer 2 Report

This study explored the association of air pollution (particulate matter) with risk perception by conducting a systematic review of studies published between 2000 and 2020. The primary finding of the study was a general correlation between air pollution and perception of air pollution risk, as defined as understanding, psychological consequences, physical consequences, and behaviours. This is the first study of this type, and I believe the topic is important. Most elements of the study are in accordance with PRISMA guidelines, and data are well presented. However, I have several concerns with aspects of the study and manuscript. At present, the review is not systematic. I hope the following comments are helpful.

Major:

• It seems that the study did not include or seek to include unpublished/grey literature such as abstracts and theses, despite this being a PRISMA recommendation. This is something to consider given publication biases, where significant associations are published, whereas non-significant associations are not. Another way of examining this is by using funnel plots, though I appreciate that the authors were conducting a review and not a meta-analysis. If the authors decide not to include any unpublished/grey literature, this should be discussed as a limitation. However, it may be necessary in this case to also reframe the manuscript as a review rather than systematic review.

• Another recommendation from PRISMA that the authors did not follow is evaluation of the quality of the included studies. The authors mention sample size of studies and aspects of the study designs, but they did not evaluate this in terms of quality (e.g. longitudinal versus cross-sectional). A dedicated paragraph about this is needed. That is, the results and discussion are currently descriptive, where they should also be critical. The authors should also refer to study quality in their discussion. I.e., the limitations in the discussion should focus on the included studies as much as the review itself.

• The manuscript is well written in general, but there are several sections where simpler and plainer language would improve the manuscript considerably. For instance, lines 54-77 in the introduction about risk perception are very hard to understand. It seems essential that risk perception is described clearly, especially given that the readership of this journal may be less familiar with psychological theories of risk perception than with pollution literature.

Minor:

• Citation needed for risk perception sentence on starting on line 40.

• Line 145 – “air quality” needs to be spelled out in the manuscript in first use of AQ – it’s currently only in the abstract.

Author Response

Reviewer 2

This study explored the association of air pollution (particulate matter) with risk perception by conducting a systematic review of studies published between 2000 and 2020. The primary finding of the study was a general correlation between air pollution and perception of air pollution risk, as defined as understanding, psychological consequences, physical consequences, and behaviours. This is the first study of this type, and I believe the topic is important. Most elements of the study are in accordance with PRISMA guidelines, and data are well presented. However, I have several concerns with aspects of the study and manuscript. At present, the review is not systematic. I hope the following comments are helpful.

Major:

1. It seems that the study did not include or seek to include unpublished/grey literature such as abstracts and theses, despite this being a PRISMA recommendation. This is something to consider given publication biases, where significant associations are published, whereas non-significant associations are not. Another way of examining this is by using funnel plots, though I appreciate that the authors were conducting a review and not a meta-analysis. If the authors decide not to include any unpublished/grey literature, this should be discussed as a limitation. However, it may be necessary in this case to also reframe the manuscript as a review rather than systematic review.

Answer:

Thank you for your comment. We appreciate your remarks about the definition of a systematic review (SR). Thanks to your observation, we have deepened and expanded the topic of SR definition used among the international research community. In this regard, we consider useful the recent article by Martinic et al., 2019 that analysed the meaning of an SR in health care literature and proposed a starting point for a new, explicit SR definition.

We think we can agree that there is still no standard about the number and type of databases a researcher should explore to be considered a systematic review, whereas, the name of the databases and the methodology's description are essential to ensure transparency and reproducibility, which remain the main features of a systematic approach. The same PRISMA Statement (Moher et al., 2009) you mentioned does not rigidly define which databases should be analysed. Al things considered, we feel that we do not change the original title of our manuscript. However, in agreement with your suggestion, we have added a sentence about the non inclusion of articles available from the grey literature as a restriction we have made.

Added Lines 508-510: Moreover, we are aware that our decision not to consider scientific papers from gray literature may represent a limit of completeness, although, on the other hand, we believe the higher qualitative reliability of the review is reasonable and not negligible [39,95].

(Martinic, M. K., Pieper, D., Glatt, A., & Puljak, L. (2019). Definition of a systematic review used in overviews of systematic reviews, meta-epidemiological studies and textbooks. BMC medical research methodology, 19(1), 203. Moher, D., Liberati, A., Tetzlaff, J., Altman, D. G., & Prisma Group. (2009). Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS med, 6(7), e1000097)

2. Another recommendation from PRISMA that the authors did not follow is evaluation of the quality of the included studies. The authors mention sample size of studies and aspects of the study designs, but they did not evaluate this in terms of quality (e.g. longitudinal versus cross-sectional). A dedicated paragraph about this is needed. That is, the results and discussion are currently descriptive, where they should also be critical. The authors should also refer to study quality in their discussion. I.e., the limitations in the discussion should focus on the included studies as much as the review itself.

Answer:

Thank you for your comment. We agree with you, this notwithstanding a standardized qualitative assessment is very difficult and a dedicated tool like GRADE would be needed. In fact, many of the characteristics considered are not themselves synonymous of quality if present or absent, since it depends on how they were considered by the authors of the studies and how the investigations were carried out. For example, with regard to the type of design, a longitudinal study is not always qualitatively better than a cross-sectional or a case-control, or whether or not the inclusion of confounders also depends on how measured and considered, etc. The problem is even more complex in studies that deal with risk perception, which is our main purpose, and not only with its measurement through classic epidemiological studies. For these reasons we have opted to offer a detailed description of the characteristics of the studies, renouncing to give a comparative quality judgment, also in consideration of the fact that the studies are very dissimilar and each brings different knowledge on pollution, health risk and risk perception. An evaluation via GRADE may be carried out in the near future. However we have made some changes and additions in the Results section which are all highlighted in bue print.

3. The manuscript is well written in general, but there are several sections where simpler and plainer language would improve the manuscript considerably. For instance, lines 54-77 in the introduction about risk perception are very hard to understand. It seems essential that risk perception is described clearly, especially given that the readership of this journal may be less familiar with psychological theories of risk perception than with pollution literature.

Answer:

Thank you for your comment. We have changed the text from line 54 to line 77 trying to simplify, carrying part of the text to Discussion section (as suggested by Reviewer 1) and adding a brief explanation regarding the perception of risk from a psychological point of view.

Lines 58-68: Risk perception is not entirely rational, since people assess risks using a mixture of cognitive skills (weighing the evidence, using reasoning and logic to reach conclusions) and emotional appraisals (intuition or imagination) [4–6].

In the domain of environment and health, the study of risk perception has acquired increasing relevance as part of the knowledge required to understand social contexts and specific personal dimensions of exposure to pollutants; risk perception is fundamental in environment and health risk communication because it determines which hazards people care about and how they deal with them [7–10]. It reinforces epidemiology in evaluating the health of communities living in areas where the main perceptible sources of pollution are known, even if the evidences produced always maintain a quote of uncertainty [11].

Minor:

4. Citation needed for risk perception sentence on starting on line 40.

Thank you, we added as required the citation.

5. Line 145 – “air quality” needs to be spelled out in the manuscript in first use of AQ – it’s currently only in the abstract.

Thank you for your observation, we added as required.

Author Response File: Author Response.pdf

Reviewer 3 Report

As a reviewer I have the following remarks

1. The paper is well written and presented.
2. Abstract. Line 15: “level of exposure” – is it really exposure or concentration levels? Please check your paper for this aspect. In many cases we don’t know exposure (or dose).
3. Your abbreviation: Willingness to Pay (WTP) – please add to the list.
4. As in 3: human biomonitoring (HBM) – may be are more (Authors!).
5. I suggest to change color in Fig 1. Now is blue, put something stronger (even red).
6. Does any of this articles considered a preventive role of communication of AQ (or AQHI index)? – these tools are used to help people to percept air quality and adjust their outdoor activities.Thank you

Author Response

Reviewer 3

As a reviewer I have the following remarks

1. The paper is well written and presented.

Thank you for your comment.

2. Abstract. Line 15: “level of exposure” – is it really exposure or concentration levels? Please check your paper for this aspect. In many cases we don’t know exposure (or dose).

Answer:

Thank you for your comment. We rephrased the sentence as

Lines 17-19   Adverse health effects of exposure to air pollutants, notably to particulate matter (PM), are well known as well as the association with measured or estimated concentration levels. The perception of pollution can have a not negligible role as well.

3. Your abbreviation: Willingness to Pay (WTP) – please add to the list.

Answer:

Thank you, we added the abbreviation as required.

4. As in 3: human biomonitoring (HBM) – may be are more (Authors!).

Thank you, we did not added because it is not repeated in the text.

5. I suggest to change color in Fig 1. Now is blue, put something stronger (even red).

Answer:

Thank you for your comment. Colour issue is highly subjective and people may perceive it differently. For this reason, we decided to adopt the official PRISMA flow diagram document, which was downloaded from the website of the PRISMA Statement (http://www.prisma-statement.org/). We thank you for your suggestion, but we prefer to leave the original colour prepared by the PRISMA Statement. Please find additional information at the link : http://prisma-statement.org/PRISMAStatement/FlowDiagram

6. Does any of this articles considered a preventive role of communication of AQ (or AQHI index)? – these tools are used to help people to percept air quality and adjust their outdoor activities.

Answer:

Thank you for your comment. We added and completed a paragraph according to your suggestions, and we added a paragraph in the Discussion section.

Lines 363-377. In Ban et al. 2017 [34], in Nanjing, China and in Wen et al. 2009 [60], in six States in USA together with air pollution perception – symptoms and behaviours were considered to elucidate the consequences of individual behaviour change, coping with smog pollution in the first article [34] and the consequences of the alerts in the second [60]. Several research paper deal with the issue of risk communication and alerts and their effects on the population risk perception [42,56,57,60,61]. In Mirabelli et al., 2020 [42], knowledge of pollution and symptoms of related illnesses are more significant in areas where information about AQI is measured and disseminated; also in Reames et al., 2019 [61] pollution perception and health concern were associated with air quality alert knowledge; the study of Wen et al., 2009 [60] shows that media alerts on air quality are a very important factor related to changes in outdoor activity. In Brody et al., 2004 [57] the authors seek to improve understanding of the major factors shaping public perceptions of air quality, concluding that perceptions appear to be influenced by setting (urban vs. rural), state identification, socioeconomic characteristics such as age, race, political identification and access to information. In the study of Semenza et al, 2008 [56] people change behaviours when air quality is worse, but this does not correspond with what is measured by the control units.

Lines 483-496 4.2. Communication and recommendations

The disintermediation of communication, which is growing exponentially in the recent years, represents a relevant change in the circulation of information, with a potential relevant impact on risk perception and consequently on health [92,93]. It is reflected in the studies here examined, with a growing attention to big data utilization, and the continuous attention given to the utilization of results, the role of citizens, the importance to inform and involve people to foster prevention and reduce environmental pollution.

In fact, it is clearly conceptualized by the scientific community and the decision makers, that the only possibility to manage complex problems in the environment and health domain is sharing responsibility and action to improve the quality and durability of decisions and actions. In particular, it is of the utmost importance to gather information about risk perception to plan risk governance actions including health literacy programs, communication and engagement activities to be able to dialogue with different social actors and contribute to prevention and protection [3,21].

Author Response File: Author Response.pdf

Reviewer 4 Report

The manuscript refers to combination of ambient particulate matter levels and perceived pollution, thus it is innovative, refers to important topics and interesting. All parts of the manuscript are correctly written, although despite the limitations that the Authors are aware of and which were pointed in the manuscript. I would suggest only some minor improvements before publication. Please see the following remarks.

Abstract

Lines 14-16: The sentence is too complicated. I would suggest at least to divide it to two sentences.

Lines 27-28. Please give more details here.

Keywords vs abbreviations: Please use consequently in the whole manuscript particulate matter or Particulate Matter

Introduction

I would suggest to leave just Introduction (without “– Background”) and change the 1.1. to Background of Risk Perception or relevant. 

Moreover, I would suggest to shift lines 34-37 at the end of Introduction section or to link it with objectives of the manuscript.

Line 70: I would suggest to add the name in the line: “the seminal article of Bickerstaff [23]”.

Line 122: “…or 5 micrometers (PM2.5),…” please correct.

Lines 181-182: There is the same sentence twice one after another.

Line 185: Study selection. Who were reviewers, meaning of education and of experience? How were they chosen?

Line 299: The sentence is not clear. What Authors had in mind as exception here? And should not lines 301-303 be the part of previous paragraph?

Author Response

Reviewer 4

The manuscript refers to combination of ambient particulate matter levels and perceived pollution, thus it is innovative, refers to important topics and interesting. All parts of the manuscript are correctly written, although despite the limitations that the Authors are aware of and which were pointed in the manuscript. I would suggest only some minor improvements before publication. Please see the following remarks.

Abstract

1. Lines 14-16: The sentence is too complicated. I would suggest at least to divide it to two sentences.

Answer:

Thank you for your comment. We agree with the reviewer and have divided that initial sentence of the abstract into 2 separate sentences as follows:

Lines 17-19. Adverse health effects of exposure to air pollutants, notably to particulate matter (PM), are well known as well as the association with measured or estimated concentration levels. The perception of pollution can have a not negligible role.

2. Lines 27-28. Please give more details here.

Answer:

Thank you for your comment. We modified as follows:

Lines 29-32. This systematic review has shown that most studies establish a relationship between risk perception and pollution measurement. A broad spectrum of concepts related to perception also emerged, which undoubtedly are an indicator of information wealth, although they also stimulate the strengthening of harmonization and standardization activities.

3. Keywords vs abbreviations: Please use consequently in the whole manuscript particulate matter or Particulate Matter.

Answer:

Thank you for your comment. Done.

Introduction

4. I would suggest to leave just Introduction (without “– Background”) and change the 1.1. to Background of Risk Perception or relevant.

Answer:

Thank you for your comment. Removed Background. We maintained Risk Perception, but we changed the following name of paragraph 1.2.:

Line 78 - 1.2. Particulate matter pollution and health

5. Moreover, I would suggest to shift lines 34-37 at the end of Introduction section or to link it with objectives of the manuscript.

Answer:

Thank you for your comment. We modified the beginning of the Introduction section, clarifying the objectives of this systematic review at the beginning of the chapter.

Lines 39-49 - “This systematic review is dedicated to clarifying the role of the perception of risk of air pollution, due to its relevance in the environmental and health field. The goal is to explore studies that analyse people’s perception, together with the measurement of air pollution, in order to elucidate the relationship between them. The focus is on particulate matter (PM), as its negative health effects have been demonstrated and quantified. Social, cultural, and contextual factors can influence people’s perception, and the impacts on behavior, agency, self-efficacy, and the relationship with measured pollution should be clarified. This knowledge could be crucial to complementing studies on the health impacts of air pollution and improving decisions aimed at reducing human exposure. Moreover, recognizing the importance that perception holds in studies on Covid-19 [1] and its complex relationship with air pollution, this topic should be addressed and specifically investigated [2] “

6. Line 70: I would suggest to add the name in the line: “the seminal article of Bickerstaff [23]”.

Answer:

Thank you for your comment. Done.

7. Line 122: “…or 5 micrometers (PM2.5),…” please correct.

Answer:

Thank you for your comment. Done.

8. Lines 181-182: There is the same sentence twice one after another. IO

Answer:

Thank you for your comment. Done.

9. Line 195: Study selection. Who were reviewers, meaning of education and of experience? How were they chosen?

Answer:

Thank you for your comment. We modified the text adding the initials of the reviewers. Perhaps it was not clear that the reviewers are the authors of the article LC, GD, FG, FB and OC. The text has been modified as follows:

Lines 153-159. After removing duplicates, three researchers, authors of the paper (LC, GD and OC)) independently evaluated titles and abstracts according to the eligibility criteria. The articles selected simultaneously by the three reviewers went on to the next phase, i.e., read the full text. They thoroughly read the articles selected in the first phase in equal proportion. The reviewer individually decided to accept or reject the articles read. In cases of doubts among the three reviewers, the other two authors (FG and FB) were involved to examine the papers in order to achieve a final decision about their eligibility.

10. Line 299: The sentence is not clear. What Authors had in mind as exception here? And should not lines 301-303 be the part of previous paragraph?

Answer:

Thank you for your comment. The sentences were modified as follows:

Lines 252-259 Among the exceptions is the study of Bergstra and colleagues [51]. In this research, a cross-sectional questionnaire study was conducted for both children (2 ± 18 years) and adults (19 years and above) living in the direct vicinity of an area with heavy industry. Parents were asked to answer questions about the health of their children, with a particular focus on respiratory symptoms. Among the exceptions, a Chinese survey performed on 1000 parents 18 years old or older with children between 1 and 12 years old can also be mentioned [63].

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have put great effort into streamlining and clarifying their manuscript on several fronts. This has made it more clear why I had a hard time interpreting their initial manuscript. The manuscript reads much more clearly, and it much more understandable, especially to the likely audience of this journal. There is one major and a couple of minor points to make:

Major:

1. The authors consistently state that perception is associated with air pollution. In my initial reading, in the results section it was unclear to me that the authors meant some sort of positive association was found in the articles that they reviewed. I instead interpreted this as these articles investigating the association between AW and perception, more describing the methods than reporting results. I think a bit more clarity on this would help the reader fully understand what the authors are trying to get across. Additionally, there are some lingering questions about this association. In the discussion section the authors state that there is a “strong association” between AQ and perception, but this appears to be the first time that they have quantified the association in any way. In the results when they write of this association, how strong is this association? Relative to what? In what direction? It would be helpful to have this evidence clearly presented in the text for this discussion statement of “strong association”.

Minor:

1. Line 19: “The perception of pollution can also have a non-negligible role” – would recommend re-wording as this is a big clunky and confusing.
2. Line 20: The perception of measured exposure to PM with respect to health risks – also should reword for clarity. Overall, I would recommend using wording along the lines of the association between air pollution exposure and perception of health risks from air pollution exposure. For example, lines 40-42 are much clearer in the description of the exposure-outcome relationship the authors are investigating.
3. Need to make sure that the exposure association is clear. For example, the authors state on Line 29-30 “most of the studies establish a relationship between risk perception measurement.” The second line of the introduction is much clearer, and this clarity needs to be carried throughout the manuscript.

Besides what I’ve previously mentioned, the clarity and language has been improved.

Author Response

Cover Letter

Answers to Reviewers

Review: “Risk Perception of Air Pollution: A Systematic Review Focused on Particulate Matter Exposure”

Manuscript n. 891045

Date: August 28th 2020

Dear Reviewer,

Below you can find the complete list of comments to your review, with the answers of the authors.

Thank you and best regards,

Liliana Cori

Gabriele Donzelli

Francesca Gorini

Fabrizio Bianchi

Olivia Curzio

1

The authors have put great effort into streamlining and clarifying their manuscript on several fronts. This has made it more clear why I had a hard time interpreting their initial manuscript. The manuscript reads much more clearly, and it much more understandable, especially to the likely audience of this journal. There is one major and a couple of minor points to make:

Major:

1. The authors consistently state that perception is associated with air pollution. In my initial reading, in the results section it was unclear to me that the authors meant some sort of positive association was found in the articles that they reviewed. I instead interpreted this as these articles investigating the association between AW and perception, more describing the methods than reporting results. I think a bit more clarity on this would help the reader fully understand what the authors are trying to get across. Additionally, there are some lingering questions about this association. In the discussion section the authors state that there is a “strong association” between AQ and perception, but this appears to be the first time that they have quantified the association in any way. In the results when they write of this association, how strong is this association? Relative to what? In what direction? It would be helpful to have this evidence clearly presented in the text for this discussion statement of “strong association”.

Answer

Thank you for your comments. We understand that now the text is comprehensible, as well as the intentions of the authors.

With reference to your discussion about the association, we agree that mention a strong association in the conclusive remarks is not suitable. The strength of association derives from the number of articles establishing a direct connection (we modified the phrase in the conclusions as follows:

In most articles, a direct association of perception with measured pollution was identified, with several specific features.

To further clarify the results, we added a Table 3 to the text, the following

Table 3. Association between perception and measured air pollution. The number of articles for each kind of association is shown, with the references. Further details for each article in Table 1.

Minor:

1. Line 19: “The perception of pollution can also have a non-negligible role” – would recommend re-wording as this is a big clunky and confusing.

Thank you for your comments. New phrase

The role of perception can be relevant in exploring effects and pollution control actions.

1. Line 20: The perception of measured exposure to PM with respect to health risks – also should reword for clarity. Overall, I would recommend using wording along the lines of the association between air pollution exposure and perception of health risks from air pollution exposure. For example, lines 40-42 are much clearer in the description of the exposure-outcome relationship the authors are investigating.

Thank you for your comments. New phrase

The purpose of this study was to explore studies that analyse people’s perception, together with the measurement of air pollution, in order to elucidate the relationship between them. We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

1. Need to make sure that the exposure association is clear. For example, the authors state on Line 29-30 “most of the studies establish a relationship between risk perception measurement.” The second line of the introduction is much clearer, and this clarity needs to be carried throughout the manuscript.

Thank you for your comments. We think now the association is more clear.

Besides what I’ve previously mentioned, the clarity and language has been improved.

 Thank you for your comments.

Reviewer 2 Report

The authors' revisions appear sound - I have no further comments to offer. Many thanks. 

Author Response

Cover Letter

Answers to Reviewers

Review: “Risk Perception of Air Pollution: A Systematic Review Focused on Particulate Matter Exposure”

Manuscript n. 891045

Date: August 28th 2020

Dear reviewer,

We thank you very much for your revision and approval to the work done,

We send our best regards

Liliana Cori

Gabriele Donzelli

Francesca Gorini

Fabrizio Bianchi

Olivia Curzio