New Delhi: The immersion of thousands of statues of Hindu gods containing toxic chemicals into rivers and lakes every year poses a pollution threat as festivals become increasingly commercialized, environmentalists said.

Hindus across India celebrate various religious festivals in September and

Polluting splash: Ganesh idols immersed by devotees in the Sabarmati river in Ahmedabad on Monday.

Elaborately painted and decorated idols are worshipped before mass processions take them to nearby rivers, lakes and the sea where they are immersed in accordance with the Hindu faith.

But environmentalists say the idols are often made from non-biodegradable materials such as plastic, cement and plaster of Paris and painted using toxic dyes.

“The commercialization of holy festivals like Ganesh Chaturthi and Durga Puja has meant people want bigger and brighter idols and are no longer happy with the ones made from eco-friendly materials," said Ramapati Kumar, a toxics campaigner for Greenpeace India. “Traditionally, the idols were made from mud and clay and vegetable-based dyes were used to paint them but now it’s more like a competition between households and between corporates who sponsor the idols to gain publicity."

Environmentalists say materials such as plaster of Paris do not dissolve easily and reduce the oxygen level in the water resulting in the death of fish and other aquatic organisms.

Also, the paints used contain heavy metals such as mercury, chromium and lead which are carcinogenic, said activists, adding that this could adversely affect drinking water.

Some 80% of India’s 1.1 billion population are Hindus but in recent years, their religious festivals and customs have come under increasing scrutiny as public awareness of environmental issues grows.

The spring festival of Holi involves the throwing of coloured powder but studies have found that the industrial powders are often toxic and can cause asthma, temporary blindness and even skin cancer.

“No one is saying that the immersion of idols should not happen—religious practices should be respected," said Suresh Babu from the Centre for Science and Environment, an environmental activist group.

“But the government should impose guidelines to craftsmen who make the idols to use eco-friendly materials and organic paints so that we give the environment as much respect as we give god."