This comment discusses the use of PM2.5 (mass concentration of fine particulate matter with an aerodynamic diameter less than 2.5 microns) data in the recently published article entitled “Air Quality, Pollution and Sustainability Trends in South Asia: A Population-Based Study” by Abdul Jabbar et al. []. The authors have used two types of PM2.5 data, i.e., PM2.5 concentrations and PM2.5 exposure data. The source of PM2.5 concentration is not explicitly mentioned; however, the article published by Upadhyay et al. [] is cited in Figure 4. Upadhyay et al. mentioned that PM2.5 concentrations were obtained from the ground-based air quality monitoring stations installed at the US embassies in major cities in South Asian countries. These concentrations are limited to specific cities and do not represent country-level air pollution scenarios. The purpose of this comment is not to discuss the PM2.5 concentrations provided by the US embassies, but instead to comment on the use of the PM2.5 exposure data, which are used in Abdul Jabbar et al.’s paper. These exposure data are obtained from the World Bank database (https://databank.worldbank.org/source/world-development-indicators (accessed on 17 October 2022)). PM2.5 exposure (EXP) is related to PM2.5 concentrations through Exp = SUM{(Pi/P) × Ci}, where Ci = annual mean PM10 or PM2.5 concentration in sub-population Pi, P = SUM (Pi), which is the total population in cities with data [].
It is well established that both PM2.5 concentrations [] and PM2.5 exposure [] significantly increased in Pakistan during the last few decades. However, the PM2.5 exposure data reported by Abdul Jabbar et al. [] do not show substantial variation between 1990 and 2017, and they state that the mean exposure to PM2.5 in Pakistan over the period was “steady”. We illustrate the discrepancy in Figure 1, which plots the time series of PM2.5 exposure data (2010–2017) obtained from the World Bank database (which are used by Abdul Jabbar et al. []) and PM2.5 concentrations obtained from both the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis data (2010–2017) and the World Health Organization (WHO) website (https://www.who.int/data/gho/data/themes/air-pollution/who-air-quality-database, accessed on 17 October 2022) (2010–2016).
Figure 1.
Time series of PM2.5 concentrations obtained from (a) the WHO database (2010–2016) and (b) CAMS reanalysis data (2010–2017). (c) PM2.5 exposure was obtained from the World Bank database (2010–2017). PM2.5 concentrations from the WHO website were not available for 2017.
Pakistan is the second-most polluted country among South Asian countries, as reported by the authors []. Therefore, reliable and accurate information is required for policymakers and research scientists to mitigate air pollution problems in Pakistan. Thus, further investigation is required to resolve discrepancies between PM2.5 exposure and concentration data from different sources before they can be used in any scientific research or policy application.
Author Contributions
Conceptualization, M.B.; methodology, M.B.; software, M.B.; validation, M.B. and G.d.L.; formal analysis, M.B.; investigation, M.B.; resources, M.B.; data curation, M.B., A.M. and M.A.A.; writing—original draft preparation, M.B.; writing—review and editing, M.B., G.d.L., J.E.N., M.P.B., L.Y. and H.C.; visualization, M.B.; supervision, M.B.; project administration, M.B.; funding acquisition, M.B. and H.C. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by the National Natural Science Foundation of China (grant number U22A20620).
Data Availability Statement
The data used in this research are available on the World Bank website (https://databank.worldbank.org/source/world-development-indicators (accessed on 17 October 2022)) and the World Health Organization (WHO: https://www.who.int/data/gho/data/themes/air-pollution/who-air-quality-database (accessed on 17 October 2022)).
Acknowledgments
The authors would like to acknowledge the Copernicus Atmosphere Monitoring Service (CAMS), the World Health Organization, and the World Bank for air quality data (PM2.5).
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.
References
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