Environmentalists said materials like Plaster of Paris do not dissolve easily and reduce the oxygen content in the water, which in turn results in the death of fish and other aquatic species.
"The government needs to undertake a regular exercise of wedging the Plaster of Paris. The level water has come up. The number of idols is increasing and it takes a lot of time to dissolve," said W. G. Prasanna, the Director of the Andhra Pradesh National Green Caps, an NGO.
The paint used in idols also contain heavy metals such as mercury, chromium and lead, which contaminate the water further.
Usually, idols are made of Plaster of Paris and adorned with glittering clothes, tonnes of artificial jewellery and harmful chemical paint. These take an extremely long time to degrade.
The Central Pollution Control Board (CPCB) had issued guidelines on use of material for the making Idols. They stipulate that idols should be made of clay instead of Plaster of Paris.
The CPCB has also asked idol makers to discard the use of all plastics and other insoluble ornaments.
In recent years, religious festivals and customs have come under scrutiny, as public awareness of environmental issue is growing.