Air Pollution and COVID-19 Mortality in Brazil
Round 1
Reviewer 1 Report
The authors investigated the association between ambient PM2.5, NO2, and O3 with COVID-19-associated deaths in Brazil using a negative binomial mixed model. They found 1μg/m3 increase of long-term PM2.5 exposure was associated with a 10.22% (95% CI: 9.35; 11.09) increase in COVID-19 deaths, which is significant. The result is interesting and I have some minor comments.
Major concern
In the mortality rate analysis (Figure 3, 4 and 5) associated to PM2.5 exposure, the author found the mortality rate increated from “without 2021” to “without 2020”, which was confusing, since the Covid-19 in 2020 was more serious than 2021. The author can provide more explannation for this result or check the model analysis.
Minor concers:
Line 32, please mention the full nae of “CI”;
Table 1, change the comma “,” to “.” in the numbers.
Figure 3, I am confusing by the result of bi-pollutants model, for example why the NO2 (+PM2.5) and PM2.5 (+NO2) did not show the same result, what has been constrained to make these two cases different? The author should well explain this in the Methods.
Figure 4, please improve the x axis, to clarify it.
Line 252, 254, 255, please change PM25 to “PM2.5”.
Line 266, “In our study, we estimated a 10.22% (95% CI: 9.35; 11.09) increase in COVID-19 deaths associated with PM2.5 exposure”, please provide how did the authors calculate.
Author Response
Please see the attached file
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Damasceno et al. described the link between air pollution and COVID-19 mortality in Brazil. The authors found that air pollution is an important cofactor that increases the risk of death from COVID-19 in Brazil. The study is very interesting and the manuscript is well-written. I suggest improving the discussion to describe how air pollution can complicate COVID-19 cases. Also, the introduction needs to be improved, please see the attached file.
Comments for author File: Comments.pdf
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors,
this is a well-written manuscript, presenting a real-life ecological study which evaluated the association between air pollution and deaths due to the COVID-19 pandemic. I liked the idea to design single pollutant models and compare them with bi- and tri-pollutant models. Your research question may have important implications, as the ability to connect the mortality of severe pulmonary viral infections with air-pollution may influence political and public health decision making. You have worked retrospectively in a national scale, which is the main strength of your study. The confounders have been mentioned as a disadvantage in the discussion, but the straight-forward statistical analysis of your data has unquestionably provided some impulse for further studies in the future. I have no questions or queries and wish you good luck in publishing your work.
Best Regards
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The manuscript is very interesting and improved a lot. I have no further comments. Thanks
