The most serious impact of the Ganesh Chatutrhi festival on the natural environment is due to the immersion of icons made of Plaster of Paris into lakes, rivers and the sea. Traditionally, the Ganesh icon was sculpted out of earth taken from nearby one's home. After worshipping the divinity in this earth icon, it was returned back to the Earth by immersing it in a nearby water body. This cycle represented the cycle of creation and dissolution in Nature.
However, as the production of Ganesh icons on a commercial basis grew, the earthen or natural clay (shaadu maati in Marathi) was replaced by Plaster of Paris. Plaster is a man made material, easier to mould, lighter and less expensive than clay. However, plaster takes much longer to dissolve and in the process of dissolution releases toxic elements into the water body. The chemical paints used to adorn these plaster icons; themselves contain heavy metals like mercury and cadmium.
On the final day of the Ganesh festival thousands of plaster icons are immersed into water bodies by devotees. These increase the level of acidity in the water and the content of heavy metals. The day after the immersion, shoals of dead fish can be seen floating on the surface of the water body as a result of this sudden increase.
Several non-governmental and governmental bodies have been addressing this issue. Amongst the solutions proposed by various groups some are as follows: