About 80 percent 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 colored 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 think-tank.

"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."