Review Reports

Round 1

Reviewer 1 Report

General comments

Indoor exposure to particulate matter (PM) may lead to harmful health effects. However, a lack of the measurement hampered the accurate quantification. The authors collected the aerosol samples produced by different indoor sources. They measured the number, mass, and surface area. They reported higher PM mass and surface area during electronic cigarette usage than tobacco cigarette burning, as opposed to the number concentration presented in this paper. This might contradict to previous studies. The authors should address this issue before publication in Atmosphere.

 

Specific comments

p.3, l.107: This paragraph is almost taken from [68] and the connection to previous paragraph, which already describes the importance of size, is not fluent. Please describe the relationship between the indoor PM and the low solubility particles.

 

p.4, l.130: Pease specify the measurement method of surface area.

 

p.6, l.173: Please compare the present results regarding e-cigarette vs. tobacco with previous results in the literatures and elucidate why the electronic cigarette usage resulted in higher mass than tobacco cigarette burning, as opposed to the number concentration.

 

p.8, l.213: Fig. 3 showed the highest number concentration for the combustion of the tobacco cigarette. Please rephrase the sentence and explain why the tobacco cigarette burning resulted in lower surface area than electronic cigarette usage.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting, useful and well-conducted study of various common indoor sources of particulate matter, including several of particular current interest. The paper is well-written and will make a useful contribution to the literature. I have a few suggestions for improvements.

General: it’s not strictly correct to say that e-cigarettes “burn”. I appreciate that it’s difficult to find another suitable word – perhaps ‘during emission’? I would welcome other ways to make this distinction.

Methods: is anything known about the air exchange rate in the room? Information about particle removal is given in the results (e.g. line 162) but without knowing more about ventilation it’s difficult to assess this.

More general information about the room (and possibly a picture, perhaps replacing Figure 1) would be helpful in understanding the circumstances of the measurements.

How were e-cigarette and tobacco emissions produced? E-cigarettes in particular generally require a vaper to be using the device actively in order to produce aerosol. There may be ethics approval requirements if a vaper was asked to participate in this fashion.

E-cigarette emissions can vary substantially between different brands (to a lesser extent this is true of tobacco cigarettes and candles as well). More details on the types of each product would be useful.

Table 1: were candles removed from the room, extinguished or allowed to smoulder after 40 minutes? This would affect their particle emissions. It would be helpful to clarify this for each source.

Discussion: it might be helpful to comment on the types of particles likely to be emitted by each sources. E-cigarettes, for instance, produce largely liquid particles which evaporate quickly. This may lead to different health effects than solid-phase particles from combustion sources.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The contribution of indoor combustion sources to fine particles and ultra fine particles is not a problem. This experimental design does not have a better understanding of indoor fine particle pollution. The details of the experiment need to be further explained. There are also several basic problems that need to be further discussed and explained by the author.

1. The structure of the environmental cabin needs to be described in detail. The figure of the structure of the environmental cabin is more helpful than the DAS.
2. Is the particulate matter monitor in or outside the environmental cabin?
3. The burning time of different combustion sources and the specific experimental description are not detailed enough. It is suggested that the specific time node diagram of the experiment should be given, especially cooking.
4. The values for UFP, PM1, PM2.5 and PM10 from different combustion source in figure 3-6 showed different highest level at different time. There might be more story to talk.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I have a minor comment.

p.8, l.236: Please indicate the median diameters for medium and small-sized aerosol particles. I would like to read the discussion on what makes the higher concentration of medium and small-sized aerosol particles in the smoke of an electronic cigarette than tobacco smoke.

Author Response

p.8, l.236: Please indicate the median diameters for medium and small-sized aerosol particles. I would like to read the discussion on what makes the higher concentration of medium and small-sized aerosol particles in the smoke of an electronic cigarette than tobacco smoke.

In text, Figure 2 presents UFP and fine particle concentration generated by six different aerosol sources (burning duration means when the aerosol source was on), as measured by the DAS.

And Table 2.  Added Number size distribution parameters of ultrafine particles for different aerosol sources.

Aerosol sources		Background		During source on		10 min after stop		60 min after stop
		NMD(nm)	GSD	NMD(nm)	GSD	NMD(nm)	GSD	NMD(nm)	GSD
	T-cig.	54.6	1.73	92.1	1.85	115.8	1.43	57.1	1.86
	E- cig.	54.5	1.84	71.3	2.22	39.4	2.06	50.1	1.83

Reviewer 2 Report

I thank the authors for their attention to my previous review. I have responded to a few of their responses below.

“We agree that the term "burning" does not quite adequately describe the functioning of the electronic cigarette. However, it should be noted that the sublimation of the contents of an electronic cigarette occurs when it is heated. It seems to us that the term "combustion" is simpler and more comprehensible than the term "during emission". We will comment on the use of the term "combustion". By the way, this comment will be appropriate for the heat treatment of food, for combustion as such was absent, but oil boiling was observed.”

‘Combustion’ or ‘burning’ may be an easier word but it isn’t correct – I see what you mean about oil boiling but it only reinforces my point here! However, this is a minor issue of language and clarification in text will be sufficient.

“Experiments with tobacco and electronic cigarettes were carried out with the participation of a volunteer who constantly uses them.”

Was ethical approval sought to use human participants in this study? I think this should be considered and reported in the paper, along with details of the applicable committee.

“Regular tobacco cigarette. The experiment was carried out in two versions. In the first experiment, the cigarette smoldered on its own for about 10 minutes. In the second experiment, a volunteer smoked a cigarette of the same type.”

Please report the results of these experiments separately and make these methods clear in the body of the paper.

“The composition of solutions for electronic cigarettes is almost the same. It consists of propylene glycol and a small amount of aromatizates. In this regard, we did not consider the differences in the characteristics of aerosols for various types of electronic cigarettes.”

The issue here isn’t with the composition of the solution but the brand of e-cigarette. Different models heat the solution in different ways – e.g. see https://doi.org/10.1016/j.envpol.2018.08.069. Please address this in text by providing the brand and type of e-cig used, along with any applicable settings on the device.

“IQOS devices, where the thermal sublimation of nicotine from tobacco occurs, were also investigated by us. These devices showed a minimal increase in the concentration of aerosol particles above the background level (2-3 times). Therefore, the results of this experiment were excluded from further consideration. The reason for this decision was, among other things, ethical considerations. The authors of the article would not like to give a scientific support of the "safety" of IQOS devices.”

I’m concerned by this omission. The authors indicate that they didn’t submit these results for publication because they didn’t like what they found. It may be the case that HTPs produce less PM2.5 than combustible cigarettes and other sources – that doesn’t necessarily make them safe (non-PM pollutants may be present in vapour phase) but it may still be true. Refusing to publish these results because they may be interpreted positively for HTPs creates bias in the literature and reduces the credibility of tobacco control researchers.

For clarity, I have no connection, financial or otherwise, with the tobacco industry (or any front group such as the “Foundation for a Smoke-Free World”).

I have one additional minor comment. There appears to be an error with Dr Zhukovsky’s affiliations – there’s a superscript ‘3’ by their name but no third affiliation is listed for that number.

Author Response

I thank the authors for their attention to my previous review. I have responded to a few of their responses below.

Again we want to present a great thanks for informative and sensitive revision

“We agree that the term "burning" does not quite adequately describe the functioning of the electronic cigarette. However, it should be noted that the sublimation of the contents of an electronic cigarette occurs when it is heated. It seems to us that the term "combustion" is simpler and more comprehensible than the term "during emission". We will comment on the use of the term "combustion". By the way, this comment will be appropriate for the heat treatment of food, for combustion as such was absent, but oil boiling was observed.”

‘Combustion’ or ‘burning’ may be an easier word but it isn’t correct – I see what you mean about oil boiling but it only reinforces my point here! However, this is a minor issue of language and clarification in text will be sufficient.

Agree with you

“Experiments with tobacco and electronic cigarettes were carried out with the participation of a volunteer who constantly uses them.”

Was ethical approval sought to use human participants in this study? I think this should be considered and reported in the paper, along with details of the applicable committee.

Agree with you, a volunteer here one of the authors

“Regular tobacco cigarette. The experiment was carried out in two versions. In the first experiment, the cigarette smoldered on its own for about 10 minutes. In the second experiment, a volunteer smoked a cigarette of the same type.”

Please report the results of these experiments separately and make these methods clear in the body of the paper.

Agree with you, but now we prepared separate article in details with this point

“The composition of solutions for electronic cigarettes is almost the same. It consists of propylene glycol and a small amount of aromatizates. In this regard, we did not consider the differences in the characteristics of aerosols for various types of electronic cigarettes.”

The issue here isn’t with the composition of the solution but the brand of e-cigarette. Different models heat the solution in different ways – e.g. see https://doi.org/10.1016/j.envpol.2018.08.069. Please address this in text by providing the brand and type of e-cig used, along with any applicable settings on the device.

Agree with you, Pone type added in text

“IQOS devices, where the thermal sublimation of nicotine from tobacco occurs, were also investigated by us. These devices showed a minimal increase in the concentration of aerosol particles above the background level (2-3 times). Therefore, the results of this experiment were excluded from further consideration. The reason for this decision was, among other things, ethical considerations. The authors of the article would not like to give a scientific support of the "safety" of IQOS devices.”

I’m concerned by this omission. The authors indicate that they didn’t submit these results for publication because they didn’t like what they found. It may be the case that HTPs produce less PM2.5 than combustible cigarettes and other sources – that doesn’t necessarily make them safe (non-PM pollutants may be present in vapour phase) but it may still be true. Refusing to publish these results because they may be interpreted positively for HTPs creates bias in the literature and reduces the credibility of tobacco control researchers.

There is miss understanding we already discuss and publish these results in

Journal of Environmental Health Science and Engineering (2021) 19:867–879 https://doi.org/10.1007/s40201-021-00653-6

For clarity, I have no connection, financial or otherwise, with the tobacco industry (or any front group such as the “Foundation for a Smoke-Free World”).

We understand your scientific view we also the same.

I have one additional minor comment. There appears to be an error with Dr Zhukovsky’s affiliations – there’s a superscript ‘3’ by their name but no third affiliation is listed for that number.

Many thanks with your focus eye moderated in text

 

 

 

Reviewer 3 Report

The design of this experiment should be sufficiently improved to understand deep on the indoor air pollution.

Author Response

The design of this experiment should be sufficiently improved to understand deep on the indoor air pollution.

We hope that revised version be clear and sufficiently improved to understand deep on the indoor air pollution with the scope of Particulate Matter for Quotidian Aerosol Sources in Indoor Air