Fluoride Exposure and the Effect of Tobacco Smoking on Urinary Fluoride Levels in Primary Aluminum Workers

Round 1

Reviewer 1 Report

The paper shows a survey on fluoride exposure in industrial setting.

Numerous elements require a change/implementation:

1)Introduction: is too long. It must be more concise and centered on the topic.

2)The population under study: you enrolled 76 workers in a period of 6 years, it is useful a description of these men more detailed, in addition to age and smoking, (place of residence? town? country? seaside? also to know the probabile fluoride level in drinking water; any other information regarding possible fluoride exposure in daily lifetime: tea consumption? how often?; use of toothpastes enriched with fluoride? how often in a day? during the workshift?). A more accurate description of the 76 workers is needed, above all regarding the confounding factors.

3)Results: is missing a description of sampling: how many workers in 2012, in 2014, in 2016, in 2018?  in what tasks/site/position? A comparison among the different years is needed, both for environmental and biological monitoring. Also to understand if there were some differences across the time.

It would be advisable to insert a correlation graph between the environmental and biological data for the same worker, reporting the results for all the recruited subjects. This graph help us to understand also counfounding factors (between environmental and biological data there should be a close correlation in the absence of other exposure source).

4)Discussion: you need to enter a comparison between results of this study and reference value for general population, in addition to considerations on working limit values. This is needed because results are higher in end-shif samples but it is important to understand if this level is still comparable with that of a population not occupationaly exposed to fluoride.

This section must be more concise and centered to the topic.

5)Conclusion: The absence of statistical significance for smoking habit call for further consideration about confounding factors: during the 8 hours of working shift is possible the assumption of fluoride by other sources? (tea? toothpastes, others? or is possibile that workers don't smoke?), these information are important also to understand the accuracy of statistical significance for the overall results. Moreover if the levels are quite low, and similar to general population, the occupational exposure seems to be less problematic. 

6) bibliographic citations: in the text, as at line 220 or 246, the correct mode of citation is: "According to Seixas et al [7], mean urine..." and NOT "According to [7] mean urine...". 

 

Author Response

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Reviewer 2 Report

Introduction – An historical overview of aluminium production is presented in great depth. While this may be interesting to the reader, the authors should also use this section to describe the context of their current work in relation to the scientific literature and current knowledge. This is certainly not the first paper to describe an occupational biomonitoring study of fluorine, so I would expect some significant changes to this section where the authors present this other information, outlining biomonitoring and specifically its application for fluoride with some relevant references.

Methods are generally well described. It is unfortunate that the authors did not consider using a quantitative measure for smoking, such as urine cotinine, rather than just relying on self-reported data. However, it is unlikely that such testing could be performed at this time. But perhaps the authors might consider this point for future studies?

Line 129 – Can you expand on ‘clean containers’. For example, had a random selection been screened for contamination?

Table 2 – It might help with clarity to move the ‘n= ‘ to the bottom row of each section.

Page 5 – Tighten up the discussion. The authors start describing exposure conditions as far back as the 1980s. Is this relevant to the current study? Please delete any irrelevant discussion.

I am no expert in fluorine biomonitoring, however, I am aware that fluoride in urine is a challenging biomarker to interpret. The authors should outline the main issues better (perhaps in their introduction). The data presented here are interesting. However, I would like to see a much greater level of discussion of the current data with respect to other published studies. The authors only refer to a couple of studies towards the end of the paper.

The authors should give much more consideration to the existing scientific literature on fluoride exposure. They should make a serious assessment of how their data adds to our current scientific knowledge and make this clear in their discussion.

Author Response

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Round 2

Reviewer 1 Report

Dear,

the correct form of your paper is now more complete in results presentation and in confounding factors definition.

The studying sample is more clear. The limit of the study are now better explained.

I have only one question:

in figure n. 2 (pre-shift and post shift data) it seems that the urine samples were collected in different time (and perhaps on different workers?). While in the text (335-340) you talk about pre-shift and post-shift data of the same worker.

So I ask you: the graphic is uncorrect? the workers were the same but the collection of pre-shift and post-shift data was done in different days? this last situation is not ideal for a comparison.

Perhaps you could clarify this element.

Attention in line 54: there's a "and" to eliminate.

Attention in line 321: there's "approx." the word must written completely

kind regards

Author Response

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Reviewer 2 Report

Happy with changes

Author Response

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