Abstract Description: This study examines variation in ultrafine particles (PM1) during a festival and their toxicity using an in-vitro experiment on A549 cell line. PM1 collected before, during and after the festival for two consecutive years 2019–20. Its size, morphology and elemental composition were examined using SEM–EDX and EDXRF. Backward wind trajectories were calculated to analyse the transport of pollutants through wind action. To determine toxicity, A549 cells were treated for 24 h with four different PM1 concentrations: 25, 50, 100 and 150 μg/ml. Cell viability, oxidative stress and cell morphology were examined to assess the cytotoxicity due to PM1 exposure. This analysis suggests a significant increase in PM1 and its metal fraction during the festival. PM1 concentrations before, during and after the festival were 67.11, 90.30 and 143.85 μg/m3 in 2019; and 135.12, 201.47 and 60.14 μg/m3 in 2020. During Diwali, high concentration of metal-rich PM1 was observed compared to pre- and post-Diwali for 2019 and 2020. Concentrations of all metals were higher on Diwali than that of pre- and post-Diwali. Metals such as Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Br, Sb, Ba, W, Pt and Pb associated with PM1 were strongly correlated with ROS generation and cytotoxicity. The particulate matter of Diwali has the capacity to adhere to the cells and affect them in various ways. The backward trajectory suggests that air pollutants may be transported to the city from northwest parts of the country. Metal-rich PM1 exposure was strongly correlated with reactive oxygen species (ROS) generation and cytotoxicity. A high dose (150 μg/ml) of PM1 exposure lowered the cell viability significantly by 71% (at p < 0.05). Elevated PM1 during Diwali has the potential to adhere to the cellular membrane and affect its morphology.
