PM_2.5 pollution and its correlation with meteorological parameters over the four capital cities of Pakistan

In terms of air pollution-related mortalities, Pakistan comes in third place globally, with aerosol mass concentrations (PM_2.5) continuously significantly higher than the WHO air quality guidelines. However, regulation relies on inadequate ground data and a limited network of air quality monitoring stations. This study describes and ranks the air pollution scenarios and pollution features of four chosen cities in Pakistan using long-term PM_2.5 measurements. One of the datasets utilized is CAMS (Copernicus Atmosphere Monitoring Service). The findings indicate that the type of pollutant considered and the metric employed determine which cities are the most polluted. For instance, Lahore was named Pakistan's most polluted city in terms of PM_2.5. According to the findings, the average annual PM_2.5 concentration in Pakistan from 2018 to 2023 was 54.7 µg m^-3, indicating that the entire population has been exposed to elevated levels of PM_2.5 for a long time. This number surpasses both the air quality guidelines (AQG) (mean annual PM_2.5 < 15 µg m^-3) and National Environmental Quality Standards, i.e., < 15 µg m^-3 annual mean for ambient air as specified by the Pakistan Environmental Protection Agency (Pak-EPA). All four cities showed statistically significant negative (falling) trends in PM_2.5. In most cities, humidity had the greatest impact on PM_2.5 concentrations, followed by temperature, wind speed, and precipitation, despite the variations in climate. There was a negative correlation between PM_2.5 and weather in many cities. This is the first study of its sort to examine PM_2.5 in detail, including its spatiotemporal properties, trends, and relationship to meteorological parameters across four Pakistani cities.