Dear Dr. Yakovenko,

Thank you for submitting your manuscript to PLOS ONE. I have received the reports from our reviewers on your manuscript, PONE-D-25-08822 "Human exposure to PM10 microplastics in indoor air", which you submitted to PLOS ONE, and have decided that your manuscript can be reconsidered for publication should you be prepared to incorporate major revisions. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. When preparing your revised manuscript, you are asked to carefully consider the reviewer comments which can be found below, and submit a list of responses to the comments.

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We look forward to receiving your revised manuscript.

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Linton Munyai, PhD

Academic Editor

PLOS ONE

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3. Thank you for stating the following financial disclosure:

 [ANR-20-CE34-0014 ATMO-PLASTIC

ANR-23-CE34-0012 BUBBLPLAST].

At this time, please address the following queries

a) Please clarify the sources of funding (financial or material support) for your study. List the grants or organizations that supported your study, including funding received from your institution.

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Additional Editor Comments:

Dear Authors,

I would like you to clarify few things on the manuscript:

1. The height of 1.6-1.7m, can you please justify the selection of this height?

2. In cars, how did you standardize the collection of air particles, Was the air-condition always on/off? During the period of collection, were the windows closed or opened? I assume if windows are open and aircorn is on, there will be re-suspension of particles inside the car. How did you standardize that from one car to the other? Same applies inside the house. When sweeping, whether the floor is carpet or tiled, there will also be re-suspension. How was all these accounted for?

3. I missed a point on verification of whether it was plastics inhaled, or it is other dust particles? Can you put readers into confidence on how microplastics were verified.

Reviewers' comments:

Comments to the Author

Reviewer #1: 

This manuscript is an interesting and important contribution to the study of airborne microplastics. The topic is highly relevant, and the findings add valuable insights into indoor exposure, which makes it even more compelling. The study is well thought out, and the methods are strong.

The comments below are just suggestions to help improve clarity and readability. The research is already solid, and with a few changes, it will be even stronger and easier for readers to engage with.

1) Lines 24–26: The abstract presents interesting findings, but the take-home message could be clearer. Consider emphasizing why your study is particularly significant compared to previous work. For example, rephrase the last two sentences to highlight the critical health implications more directly.

2) Line 20: The term "power size distribution law" is mentioned in the abstract but not explained. Since this may not be familiar to all readers, a brief clarification (even a parenthetical note) would improve accessibility.

3) Lines 72–78: The inclusion of the car cabin environment is an interesting and novel aspect, but its significance isn’t immediately clear. Would it be useful to briefly explain why car environments were chosen alongside residential space? perhaps highlighting their relevance to daily exposure?

4) Lines 62–65: The introduction covers a lot of ground effectively, but the transition to the research gap could be smoother. The sentence starting with "However, despite its potential, only two studies [27,28]..." feels abrupt. Could you introduce this section with a more gradual lead-in?

5) Lines 14, 20, 68 .. : The manuscript switches between "MP1–10µm" and "MP1–10 µm" (with and without a space). Standardizing this across the text will improve readability.

6) Lines 88–90: The choice of sampling heights (1.6–1.7 m for living rooms and 0.5 m for bedrooms) makes sense intuitively but would benefit from a brief justification. Does this reflect average breathing heights?

7) Lines 188–192: the author mentions that blank corrections were applied, but it would be helpful to explain if any contamination patterns were observed across different polymer types. Did specific polymers appear more frequently in blanks, and if so, how was this addressed?

8) Lines 320–322: the author reports that MP concentrations were higher in cars than in apartments but also mention that this difference was not statistically significant (p = 0.5). Perhaps rewording to avoid implying a strong contrast would prevent misinterpretation.

9) Lines 366–369: The estimated inhalation rates are striking, but a brief discussion of uncertainty sources (e.g., variability in human breathing rates, exposure conditions) would help contextualize the robustness of these values.

10) Lines 272–276, 300–301: The figures (1,2,3 and 4) are informative, but are the labels and axis text large enough for clear readability? I suggest improving the image quality by using higher-resolution versions.

11) Lines 317–319: The discussion highlights how your estimates are higher than previous extrapolations, which is great. However, a sentence explaining why earlier estimates were lower (e.g., due to detection limits, methodology differences) would provide helpful context.

12) Lines 348–350: The study focuses on indoor exposure, but some readers may wonder how these findings compare to occupational environments with high plastic use (e.g., textile industries). A brief mention of this in the discussion could add depth.

13) Lines 381–384: The potential health impacts of inhaling MP1–10µm are mentioned, but could you add one or two specific examples of known biological effects (e.g., inflammation, oxidative stress) to make this more concrete?

14) Lines 395–398: The conclusion does a great job summarizing findings, but a forward-looking statement about next steps in this field (e.g., improving detection methods, longitudinal exposure studies) would make for a stronger closing.

Reviewer #2:  

• The study addresses a critical and emerging issue—human exposure to airborne microplastics, particularly in the PM10 range, which is often overlooked.

• The use of Raman spectroscopy enhances the reliability of microplastic identification and size classification down to 1 µm.

• The study successfully compares indoor MP concentrations across different environments (residential vs. car cabin), contributing to the understanding of MP inhalation risks.

• The Introduction effectively highlights the importance of studying airborne microplastics, but a clearer transition into study objectives would improve flow.

• The Discussion could be streamlined to avoid redundancy (e.g., repeated explanations about particle inhalation pathways).

• The Figures & Tables are valuable, but better integration into the text with clear references to their significance would be helpful.

• It would be beneficial to provide more details about sampling duration and how variability in MP concentrations was controlled.

• Clarify whether cross-contamination controls were performed beyond blanks (e.g., during sampling in the field).

• Some comparisons, such as MP concentrations between apartments and cars, use median values. A statistical significance test (e.g., Mann-Whitney U test) should be explicitly mentioned.

• The power law fitting for MP size distribution is informative, but additional explanation about its implications for human exposure would be useful.

• The study makes strong claims about increased MP inhalation leading to health risks. While plausible, direct toxicological evidence linking MP1-10µm to specific diseases should be elaborated with relevant citations.

• Consider discussing how long-term exposure may differ from acute exposure in different environments.

• Minor grammatical errors and awkward phrasing should be polished. Example: "Given these findings, and the fact that people spend 90% of their time indoors, the greater potential for exposure to MPs through inhalation in indoor environments should be emphasized." Suggested revision: "Given that people spend 90% of their time indoors, the potential for inhalation exposure to MPs in indoor environments is significantly higher and warrants attention."

• The study provides valuable insights into indoor airborne microplastics; however, several recent studies on ambient microplastics have been published. I recommend the authors conduct a thorough keyword search to identify and incorporate relevant literature. Strengthening the discussion by comparing indoor and ambient microplastic studies will enhance the manuscript's impact and provide a more comprehensive context for human exposure risks.

• Line 35 marine boundary layer it would be good if you will rewrite this sentence as Over the past decade, MPs have been detected in outdoor atmospheric aerosols [5–8] and deposition [9–14], in various parts of the world, from urban and highly industrialized areas [9,13] to remote mountainous regions [10,12], the marine boundary layer [7] and indoor environments. As it will give proper flow For indoor environment cite following references. Unravelling the microplastic contamination: a comprehensive analysis of microplastics in indoor house dust. An in-depth study of dust samples reveals microplastic (MP) contamination in indoor commercial markets.

• Lines 62 and 63 check the below articles as Raman has been used in indoor PM microplastics studies. So cite them here as it is contradictory when there is a gap. Airborne microplastic contamination across diverse university indoor environments: A comprehensive ambient analysis. A comprehensive characterization of indoor ambient microplastics in households during the COVID-19 pandemic. A comprehensive characterization of indoor ambient microplastics in households during the COVID-19 pandemic.

• Line 303 check the missing literature. You can cite the above literature here also.

• Compare your results of lnhaltion rates with the recent studies like. Airborne microplastic contamination across diverse university indoor environments: A comprehensive ambient analysis.. A comprehensive characterization of indoor ambient microplastics in households during the COVID-19 pandemic…

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Attachments

Attachment

Submitted filename: REVIEW plos one.pdf

Human exposure to PM10 microplastics in indoor air

PONE-D-25-08822R1

Dear Dr. Yakovenko,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Linton Munyai, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: I think this revised manuscript ’Human exposure to PM10 microplastics in indoor air’ is interesting and relevant, and I appreciate the effort the authors have put into addressing the previous comments. Their responses were clear and constructive, and the corresponding changes have improved the overall quality and clarity of the manuscript.

I am satisfied with the revisions and have no further comments. I believe the manuscript is now suitable for publication in its current form.

Reviewer #2: (No Response)

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Reviewer #1: No

Reviewer #2: No

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Attachments

Attachment

Submitted filename: reviewers report.docx