In India, the Uttar Pradesh state authorities are mandating the shuts of pulp and paper (P&P) mills near the Ganges River for three months from mid-December.
The Kumbh Mela festival is a regular event, held roughly every three years, rotating between four locations.
It sees millions of pilgrims bathing in river water to be cleansed of their sins.
The 2019 festival, like the 2013 festival, is taking place at Allahabad in Uttar Pradesh. It starts January 15.
The 2013 festival saw an estimated 120 million pilgrims participating.