Comment on Abdul Jabbar et al. Air Quality, Pollution and Sustainability Trends in South Asia: A Population-Based Study. Int. J. Environ. Res. Public Health 2022, 19, 7534

This comment discusses the use of PM_2.5 (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. [1]. The authors have used two types of PM_2.5 data, i.e., PM_2.5 concentrations and PM_2.5 exposure data. The source of PM_2.5 concentration is not explicitly mentioned; however, the article published by Upadhyay et al. [2] is cited in Figure 4. Upadhyay et al. mentioned that PM_2.5 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 PM_2.5 concentrations provided by the US embassies, but instead to comment on the use of the PM_2.5 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)). PM_2.5 exposure (EXP) is related to PM_2.5 concentrations through Exp = SUM{(Pi/P) × Ci}, where Ci = annual mean PM₁₀ or PM_2.5 concentration in sub-population Pi, P = SUM (Pi), which is the total population in cities with data [3].

It is well established that both PM_2.5 concentrations [4] and PM_2.5 exposure [5] significantly increased in Pakistan during the last few decades. However, the PM_2.5 exposure data reported by Abdul Jabbar et al. [1] do not show substantial variation between 1990 and 2017, and they state that the mean exposure to PM_2.5 in Pakistan over the period was “steady”. We illustrate the discrepancy in Figure 1, which plots the time series of PM_2.5 exposure data (2010–2017) obtained from the World Bank database (which are used by Abdul Jabbar et al. [1]) and PM_2.5 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).

Pakistan is the second-most polluted country among South Asian countries, as reported by the authors [1]. 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 PM_2.5 exposure and concentration data from different sources before they can be used in any scientific research or policy application.