Traditionally, clay was used to make Ganesh idols. Over the years however, plaster of Paris (POP), which is lighter and cheaper, has become the favoured material to mould these idols. POP contains chemicals such as gypsum, sulphur, phosphorus, and magnesium. The dyes used to colour these idols contain mercury, cadmium, arsenic, lead, and carbon. Plastic and thermocol accessories are used to decorate these idols. Such materials are not biodegradable, hence are toxic. Also, while earlier the idols were quite small, today a spirit of competitiveness pervades the celebrations, so that the idols are becoming increasingly colossal. The immersion of idols made from non-biodegradable or toxic materials has the following environmental repercussions:

With the immersion of these idols in the sea or inland water bodies such as lakes and streams, the chemicals in these idols dissolve in the water. POP dissolves slowly, gradually releasing its harmful components. The water experiences a rise in acidity as well as traces of heavy metal. The toxic waste kills plant and animal life in the water. In Mumbai, for instance, dead fish washed ashore after the immersion is a common occurrence.

Plastic and thermocol waste, including polythene bags containing offerings, is usually immersed with the idols. Because it is non-biodegradable—meaning that it does not decompose—this waste simply keeps adding up. It also obstructs the flow of streams, leading to flooding during the rains. Running water, when obstructed, turns stagnant. This can become a breeding ground for diseases and is a major health hazard for a locality.

People who use water polluted by these immersions experience a host of health problems such as infections of the lungs, and diseases of the skin, blood, and eyes.