• 660 million footfalls during the Mahakumbh Mela-2025. • Stable mineralogy with quartz, biotite, gypsum, garnet, magnetite, and clay. • Magnetic susceptibility declined post-event with no major environmental impacts. • Microplastics and an iron-rich microspherule identified in sediment samples. • Human activity caused shifts in magnetic fractions at bathing sites. The environmental impact assessment of 660 million human congregation, observed between January 13 and February 26, 2025 during the Mahakumbh Mela (Prayagraj, India) event, is presented here. This study is based on 200 alluvial sediment samples collected before and after the mass-bathing event to evaluate variations in mineralogy, magnetic susceptibility, and particulate matter (PM) size. Analyses of pre- and post-Mahakumbh sediments (PRMK and POMK, respectively) reveal a broad mineralogical similarity across the study area, comprising quartz, biotite, gypsum, tourmaline, garnet, magnetite, clay minerals, and metallic phases. In addition, microplastic fibres and an iron-rich microspherule of possible anthropogenic origin were identified in the POMK and PRMK samples, respectively. Magnetic susceptibility values for PRMK (6.75 to 538.37 × 10⁻⁸ m³/kg; x ¯ = 67.69 × 10⁻⁸ m³/kg) and POMK samples (21.33 to 138.96 × 10⁻⁸ m³/kg; x ¯ = 46.50 × 10⁻⁸ m³/kg) show no major variations, although a few anomalous spikes were recorded in both sets. Despite their uneven spatial distribution, magnetic mineral fractions appeared to regroup in zones of high human activity, especially near designated bathing sites. Overall, this sediment-based study found no significant adverse environmental effects in terms of heavy-mineral or metal toxicity, elevated magnetic loading, or hazardous respirable PM concentration in the mass-bathing area in and around the “Sangam Nose” due to the massive influx of people and associated anthropogenic activities. However, short-term pollution from other environmental media, such as river water quality and air were not investigated in the present study, and therefore, can not be ruled out.
Dwivedi et al. (2026) studied this question.