From the journal Environmental Science: Atmospheres Peer review history

05-Apr-2024

Dear Dr Feltracco:

Manuscript ID: EA-ART-03-2024-000031
TITLE: Insights into size-segregated distribution of benzothiazoles in indoor aerosols from office environments

Thank you for your submission to Environmental Science: Atmospheres, published by the Royal Society of Chemistry. I sent your manuscript to reviewers and I have now received their reports which are copied below.

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************

Reviewer 1

The manuscript investigated the indoor size-segregated distribution of BTHs in office. The work enriches the database of air pollution in buildings like workplaces and offices. However, the authors should address some concerns before the work is published.

Some major issues are summarized in the following comments:

1 Introduction Please review some recent peer-reviewed papers, https://doi.org/10.1016/j.scitotenv.2020.137979 and https://doi.org/10.1016/j.scitotenv.2022.157144, both of which might provide more information for the statement in Line 61-64.

2 Line 79 the “Aerosol indoor samples were collected in a corridor of the administrative offices”. Why did the authors collect more data from each office and obtain more comprehensive conclusion? Besides, the location in the corridor of the samplers is not provided.

3 Line 94 Could the author mark the position of the ventilation units and the sampler in a figure or statement?

4 Line 137 Why did BTH-SO3H and SH-BTH dominate the total benzothiazoles in suspended indoor particles ? Line 148 Why is the current manuscript lower than Wan’s work? Similarly, many results in this work are not well discussed.

5 Line 157-160 Could the ratio among BTHs reveal the original sources of the BTHs. The statements are too general.

6 Line 165-167 Is it possible that the fine particles come from outside sources, like the tear of tires? The authors also mentioned in Line 170-171 , “These results were also observed in road dust samples,  where the BTHs tended to be distributed in small particles” ; and in Line 182, “finer mode may indicate another source, likely outdoor”.


7 Line 172-184 The statements are a good start to investigate the sources of BTHs, but not enough. We don’t know yet where the BTHs in door came from, after reading these.

8 Section 3.2, is it possible to evaluate the toxic equivalency factor of BTHs.

Some minor issues are summarized as following , but not limited as these，

1. Line 33, a reference suggested to be cited to approve the statement;

2. Line 40 “levels” suggested to be deleted;

3. Line 60 “waters” suggested to be deleted;

4. Line 120 the “Inhalation” suggested to be uncapitalized;

5. Table 1 references are needed;

Reviewer 2

Manuscript Number; EA-ART-03-2024-000031
Title; Insights into size-segregated distribution of benzothiazoles in indoor aerosols from office environments
Although the topic is of interest to the Scientific community, before considering it for publication, this paper should be improved. In this manuscript, some concerns need to be addressed to fit for publication as follows:
Evaluation; Major Revision
1. “The impactor is equipped with eight stages, with nominal cut points of >18, 10, 5.6, 3.2, 1.8, 1.0, 0.56 and <0.56 µm. The flow rate was set at 2 L min-1, with a pressure drop of 1 kPa.” When a cascade impactor is used there is a frequent overlap between the respective stages. How do your account for this in your results? Can you present your work in the form of a size distribution?
2. In this study use cascade impactor for PM sampling, the sampling durations were 96 to 244 hours. It is very critical point that long time sampling (more than 100 hours), the particle-bound during sampling period will affect the particle mass concentration. Please clarify it.
3. Justify the use of quartz fiber filters (QFF) for gravimetric analysis, report the underlying uncertainty involved in using QFF for gravimetric analysis.
4. In addition, what are the chances of VOC getting adsorbed on the QFF when kept in the environmental weighing chamber?
5. It is necessary to describe the number of measurements n of environmental factors applied to the analysis and about 30% of the data for the regression test should be separated for verification.
6. The main text and further within the manuscript and tables: Many numeric data are given with too many significant figures; 2 significant figures suffice and 3 suffice in case the first significant figure is "1".
7. The authors should be presented the limitations of this study based on the size-fractionated indoor particles study in this area. Future studies hope to address these limitations.

Response to the comments made by the referees

Note for the Editor and for the Referees: We corrected some minor typos throughout the manuscript. All the changes were highlighted in yellow.

Referee: 1

Comments to the Author

Q: The manuscript investigated the indoor size-segregated distribution of BTHs in office. The work enriches the database of air pollution in buildings like workplaces and offices. However, the authors should address some concerns before the work is published.
A: Thank you for your comment. We appreciate your acknowledgment of the importance of our manuscript in enriching the database on indoor air pollution, particularly in office environments.

Q: Some major issues are summarized in the following comments:
1 Introduction Please review some recent peer-reviewed papers, https://doi.org/10.1016/j.scitotenv.2020.137979 and https://doi.org/10.1016/j.scitotenv.2022.157144, both of which might provide more information for the statement in Line 61-64.
A: Thanks to the Referee 1 for the suggestion. We added the following sentence in lines 62-63:
Some studies determined the concentration of some BTHs in indoor and outdoor dust, also fractionating the dust samples for a better risk assessment8,9,15–17.”

Q: 2 Line 79 the “Aerosol indoor samples were collected in a corridor of the administrative offices”. Why did the authors collect more data from each office and obtain more comprehensive conclusion? Besides, the location in the corridor of the samplers is not provided.
A: As a preliminary study, especially considering the various particle sizes, we wanted to provide an initial dataset, defining for the first time their presence across different dimensional fractions of the indoor aerosol. In the future, we certainly plan to expand our sampling sites and increase the number of samples to further enhance the depth of our findings. Regarding the sampling sites in this current study, we have added the following sentence (lines 82-83), to read:
“The exact location of the sampler is reported in Figure S1 of the Supplementary Materials.”
We then added the Figure S1 in the Supplementary Materials, highlighting the sampling site with an orange dot.

Q: 3 Line 94 Could the author mark the position of the ventilation units and the sampler in a figure or statement?
A: As suggested by the Referee 1, we reported the ventilation units and sampler location in Figure S1. We also added the following sentence in line 103:
“The positions of the ventilation units are marked in the Figure S1.”

Q: 4 Line 137 Why did BTH-SO3H and SH-BTH dominate the total benzothiazoles in suspended indoor particles ?
A: Explaining the abundances of these two BTHs is indeed quite challenging due to the scarcity of literature. It appears that further research is warranted to shed more light on this matter. We although added this paragraph from line 177 to line 182:
“SH-BTH holds significance as a key industrial compound utilized in rubber and rubber product manufacturing, serving as the precursor for various chemical compounds. SH-BTH is the most widely used compound for this purpose 6. Exact production information for SO3H-BTH derivatives is not available and no clear degradation pathway are proposed for SH-BTH that could turn into SO3H-BTH 28. The notably high concentration of SO3H-BTH serves as a clear indication that SH-BTH has undergone degradation, and atmospheric photochemical reactions may facilitate this oxidation process.”

Q: Line 148 Why is the current manuscript lower than Wan’s work? Similarly, many results in this work are not well discussed.
A: As suggested by the Referee 1, we improved the discussion of the manuscript. Besides the information of the answer provided above, we added the following paragraph from line 182 to line 186:
OH-BT has been recognized as a byproduct of BTH oxidation 29, with laboratory experiments conducted in a previous study 17 confirming that elevated temperatures lead to the conversion of BTH into OH-BT within car tire rubber particles. Hence, it is possible that a portion of OH-BTH originates from the oxidation of BTH during friction events 30.
We believe that other assertions would be excessively speculative.
Q: 5 Line 157-160 Could the ratio among BTHs reveal the original sources of the BTHs. The statements are too general.
A: As suggested by the Referee 1, we improved the cited part (lines 157-162), to read:
The presence of BTHs in air fresheners, paints, rubber insulating material, may account for their presence in indoor aerosol 24. BTH, SH-BTH, and MeS-BTH have been discovered not only in the abovementioned material but also in textile clothing. For example, the levels of these compounds in car tires ranged from 0.46 μg g-1 (for MeS-BTH) to 23.5 μg g-1 (for BTH), which were notably higher compared to textile samples, where concentrations ranged from 0.73 to 8.64 μg g-1 25. These findings suggest that wearing clothing may serve as a potential route of human exposure to emerging chemicals.
Q: 6 Line 165-167 Is it possible that the fine particles come from outside sources, like the tear of tires? The authors also mentioned in Line 170-171 , “These results were also observed in road dust samples, where the BTHs tended to be distributed in small particles” ; and in Line 182, “finer mode may indicate another source, likely outdoor”.
A: It is certainly possible that the fine particles come from external sources, such as tire wear. In our article, we have indeed mentioned that a possible source of BTHs may be the outdoor (line 169, 196, 197). However, discriminating between different sources of BTHs is extremely difficult. Pollution sources are manifold both indoors and outdoors, and often interconnected. Therefore, we agree with the fact that fine particles could originate from various external sources, identifying the specific origin is challenging without further investigation.

Q: 7 Line 172-184 The statements are a good start to investigate the sources of BTHs, but not enough. We don’t know yet where the BTHs indoor came from, after reading these.
A: We added this sentence at the end of the section, to clearly state the sources (lines 196-198), to read:
To sum up, we identified four major sources: 1) textile materials, likely the most probable source; 2) shoes abrasion; 3) building materials; 4) outdoor sources, due to the presence of fine and ultrafine particles.

Q: 8 Section 3.2, is it possible to evaluate the toxic equivalency factor of BTHs.
A: Knowing that TEF is based on the idea that PCDDs and PCDFs are structurally similar compounds with the same mechanism of action, for BTHs the authors note a lack of clear data on the mechanism of action between BTHs and the AhR receptor, making it impossible to calculate TEF and consequently TEQ. Furthermore, the toxicity of SH-BTH seems to be related to bacteria and other organisms due to its metal-chelating properties, general interference with membrane linked processes, and reactions with functional groups present in proteins.

Q: Some minor issues are summarized as following , but not limited as these，
1. Line 33, a reference suggested to be cited to approve the statement; A: Done.
2. Line 40 “levels” suggested to be deleted; A: Done.
3. Line 60 “waters” suggested to be deleted; A: Done.
4. Line 120 the “Inhalation” suggested to be uncapitalized; A: Done.
5. Table 1 references are needed; A: Done.

Referee: 2

Comments to the Author

Manuscript Number; EA-ART-03-2024-000031

Title; Insights into size-segregated distribution of benzothiazoles in indoor aerosols from office environments

Q: Although the topic is of interest to the Scientific community, before considering it for publication, this paper should be improved. In this manuscript, some concerns need to be addressed to fit for publication as follows:
A: Thanks to the Referee 2 for the feedback. We addressed the concerns raised.

Evaluation; Major Revision

Q: 1. “The impactor is equipped with eight stages, with nominal cut points of >18, 10, 5.6, 3.2, 1.8, 1.0, 0.56 and <0.56 µm. The flow rate was set at 2 L min-1, with a pressure drop of 1 kPa.” When a cascade impactor is used there is a frequent overlap between the respective stages. How do your account for this in your results? Can you present your work in the form of a size distribution?
A: Sampling artifacts were not considered in this study and for this reason we reduced this part as follows (lines 87-89): “The cascade impactor can be affected by sampling artifacts (i.e. the bounding of particles, inter-stage losses, the blow-off of particles and potential losses of semi-volatile compounds) but these are limited only to the back-up filter 23”.
D. Contini, D. Cesari, A. Genga, M. Siciliano, P. Ielpo, M.R. Guascito, M. Conte, Source apportionment of size-segregated atmospheric particles based on the major water-soluble components in Lecce (Italy), Science of The Total Environment, Volume 472, 2014, Pages 248-261, ISSN 0048-9697, https://doi.org/10.1016/j.scitotenv.2013.10.127.
Therefore, the stages are designed to prevent cross-flow interference between adjacent nozzles. The result is sharp cut-size characteristics. In addressing the question regarding the size distribution, we detail the dimensional trends in Figure 3 and Table 3, though. We believe that these existing representations capture the dimensional trends and findings relevant to our study.

Q: 2. In this study use cascade impactor for PM sampling, the sampling durations were 96 to 244 hours. It is very critical point that long time sampling (more than 100 hours), the particle-bound during sampling period will affect the particle mass concentration. Please clarify it.
A: We agree with referee if you consider a high flow of sampling with a high load of sampled material. In this case, we sampled with a flow set at 2 L min-1 and the load into the filter is low, avoiding problems of particles jump (into the middle stages) or obstruction of filter for the last stage.
In our previous studies, we have frequently utilized cascade impactors for PM sampling, using multi-stage impactors with similar sampling time resolutions. However, we have not encountered the specific issue raised by referee 2 regarding the potential impact of particle-bound effects on particle mass concentration during the sampling. Below, we list the studies where we have already addressed these methodologies:
Feltracco, M., Barbaro, E., Contini, D., Zangrando, R., Toscano, G., Battistel, D., Barbante, C., Gambaro, A., 2018. Photo-oxidation products of α-pinene in coarse, fine and ultrafine aerosol: A new high sensitive HPLC-MS/MS method. Atmospheric Environment 180, 149–155. https://doi.org/10.1016/j.atmosenv.2018.02.052
Barbaro, E., Feltracco, M., Cesari, D., Padoan, S., Zangrando, R., Contini, D., Barbante, C., Gambaro, A., 2019. Characterization of the water soluble fraction in ultrafine, fine, and coarse atmospheric aerosol. Science of the Total Environment 658, 1423–1439. https://doi.org/10.1016/j.scitotenv.2018.12.298

Q: 3. Justify the use of quartz fiber filters (QFF) for gravimetric analysis, report the underlying uncertainty involved in using QFF for gravimetric analysis.
and
4. In addition, what are the chances of VOC getting adsorbed on the QFF when kept in the environmental weighing chamber?
A: In this study, we did not conduct a gravimetric analysis due to the low mass loading on the filter. Additionally, it wasn't the primary objective of our study to evaluate the contribution of particulate matter mass. However, I'd like to note that in our research group, we typically use QFF for gravimetric analysis (see the citations above). The quartz fiber filter is usually used in our investigation because we have evaluated in our previous studies that this material has low concentrations of contaminants or chemical species, as determined in our chemical analysis. When we perform an experimental design with sampling followed by chemical analysis, we consider using a material with low contamination for a wide range of compounds measured in our laboratory. We often use the same sample and water extract to determine many species, considering that the samples are typically precious and irreplaceable.
This choice is made because quartz filters are known to introduce less contaminations compared to, for instance, glass fiber filters.

Q: 5. It is necessary to describe the number of measurements n of environmental factors applied to the analysis and about 30% of the data for the regression test should be separated for verification.
A: In the present manuscript, we opted not to conduct regression tests as we believe they wouldn't yield significant insights to draw conclusions from. Consequently, we don't see the necessity for this particular modification, as implementing it would lack a clear rationale in our current framework.

Q: 6. The main text and further within the manuscript and tables: Many numeric data are given with too many significant figures; 2 significant figures suffice and 3 suffice in case the first significant figure is "1".
A: We corrected some significant figures in the Supplementary Material and throughout the manuscript. Thank you for your comment.

Q: 7. The authors should be presented the limitations of this study based on the size-fractionated indoor particles study in this area. Future studies hope to address these limitations.
A: As suggester by the Referee 2, we integrated the Conclusion paragraph (lines 231-235), to read:
The present manuscript includes a limited number of samples and a low sample volume was sampled. The latter is attributed to the minimal noise generated by the suction pump in a public setting, aimed at minimizing disruption to administrative personnel working nearby. In future studies, efforts are required to increase the sample size by incorporating diverse sampling locations, thus enhancing the obtained information.

12-Apr-2024

Dear Dr Feltracco:

Manuscript ID: EA-ART-03-2024-000031.R1
TITLE: Insights into size-segregated distribution of benzothiazoles in indoor aerosols from office environments

Thank you for submitting your revised manuscript to Environmental Science: Atmospheres. I am pleased to accept your manuscript for publication in its current form. I have copied any final comments from the reviewer(s) below.

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Reviewer 2

Accept in the current form.

Reviewer 1

Thank you for your response.