Long-term trend of PM 2.5 over five Indian megacities using a new statistical approach

PM 2.5 is one of the major contributors to air pollution in India, resulting in poor air quality and human health issues. The current study explores the applicability of TTAinterfaceTrendAnalysis (an ‘R’ language-based Graphical User Interface package) in estimating the annual and month-wise trends in PM 2.5 over five Indian megacities (New Delhi, Kolkata, Mumbai, Hyderabad, and Chennai). The package offers a one-stop solution for various statistical analyses such as data imputation, outlier detection, trend analysis, data smoothing, diagnostic tests, etc. The trends are estimated using seven (2014–2020) years of PM 2.5 data. All estimated month-wise trends of PM 2.5 over the study cities were found to be statistically non-significant. Annual trends (both with and without applying data smoothing techniques) were found to be statistically significant with magnitudes ranging between − 0.27 and − 5.2 µg m −3 y −1 (negative sign indicates a declining trend). Autocorrelation analysis and normality tests are also conducted using the inbuilt options of TTAinterfaceTrendAnalysis. Results obtained are thoroughly discussed and compared with those of similar contemporary studies. To our knowledge, the current study is the first to apply TTAinterfaceTrendAnalysis for quantifying long-term trends in PM 2.5 . The sensitivity of the trend estimates due to the inclusion of COVID-19 lockdown PM 2.5 data was also examined. The net impact of lockdown on the PM 2.5 long-term trend ranged between − 0.13 and 2.29 µg m −3 y −1 across the study cities. Graphical Abstract