<p>Fine particulate matter (PM_2.5) poses a critical threat to air quality and public health in India, influenced by rapid urbanization, industrialization, and diverse meteorological conditions. This study examines the spatial, seasonal, and temporal variations of PM_2.5 across India from 1980 to 2020, using long-term emission inventories and atmospheric data. The Indo-Gangetic Plain consistently exhibits the highest PM_2.5 concentrations due to dense population, industrial activities, biomass burning, and agricultural practices, while central and eastern India show moderate levels, and southern and northeastern regions remain relatively clean. Seasonal analysis highlights peak pollution during winter and post-monsoon periods, driven by temperature inversions, low boundary layer heights, and crop residue burning, whereas monsoon rains reduce particulate concentrations. Over four decades, PM_2.5 levels have increased steadily, with residential, commercial, and agricultural waste-burning sectors contributing the majority of emissions. High PM_2.5 exposure correlates with elevated health risks, including respiratory diseases, premature mortality, and economic costs, particularly in densely populated northern regions. The study findings indicate that integrated mitigation strategies—such as emission control, promotion of clean energy, and improved transport and industrial policies, combined with regional air quality management—are essential to reduce PM_2.5-related impacts in India. These insights can help policymakers and stakeholders develop targeted interventions to protect human health and achieve sustainable air quality across the country.</p>