Pollution and purity

The year 2013 began in India with the culmination of a 144 year wait at the confluence of Hinduism's holiest rivers, the Ganga and Yamuna, at the city of Allahabad, also known as Prayag. The Maha Kumbh Mela had millions of devotees, tourists and academics flocking to the holy confluence over a span of two months. By the end of this massive fair, Prayag had borne the footprints of about a hundred million people – a number five times the population of Mumbai, itself one of the world's most populous cities.

The Kumbh Mela, occurring every three years, has long been considered the largest congregation of humans on the planet. The Ardh Kumbh happens every six years, the Purna Kumbh every twelve, and the Maha Kumbh – the 'Great Kumbh' – occurs only once every 144 years, or every twelfth Purna Kumbh. There are references to this festival in the Vedas and Puranas, in epics like the Mahabharata and Ramayana, and in various Tantric texts. Although not known as the Kumbh back then, under various other names the festival also finds its way into the historical accounts of Megasthenes, the Greek ambassador to the Mauryan court in the 4th century BCE, and into the Chinese traveller Xuanzang's narratives on India in the 7th century CE.