Snan reaches its largest and most concentrated collective expression at the Kumbh Mela, the periodic mass pilgrimage gathering held at four rotating sites in India, at which the specific bathing dates, determined by astrological calculation, are believed to carry the greatest possible spiritual benefit and draw pilgrim numbers regularly reported in the tens of millions, making the event's principal bathing days among the largest single gatherings of human beings for any purpose anywhere in the world, a scale UNESCO's 2017 inscription of the Kumbh Mela onto its Representative List of the Intangible Cultural Heritage of Humanity formally recognised.
The Ganges and other sacred rivers' documented pollution, from industrial discharge, inadequately treated sewage and the sheer volume of pilgrim and ritual activity along their banks, has become a genuinely significant public health and environmental concern discussed openly by Indian environmental authorities, religious leaders and scholars alike, a tension between the river's sacred status and its measurable physical condition that has prompted major, though only partially successful, government river cleaning initiatives over recent decades, and that sits, largely unresolved, alongside the continued and undiminished devotional practice of snan by millions of Hindus each year.