PALLAVAKAM , India ( CNN ) -- South India 's sun beats down on a long line of trucks wending to the Bay of Bengal . In the back of these trucks , giant , brightly painted statues of the Hindu god Ganesha are waiting to be dropped in the nearby ocean . Ganesha worshippers transport their Idol for an immersion ritual . All over India , Hindus recently celebrated the birthday of the elephant god and now the idols made for this festivity are being taken to India 's ocean , rivers and lakes and deposited . It 's part of the Hindu religious cycle . But it 's also a huge source of pollution . And in recent years , idol immersion has become a popular local event , with some statues so huge they must be lifted by cranes . The Ganeshas gleam with gold paint and glisten with reds , pinks and greens . But scientists who 've studied the problem say these paints often contain toxic metals , such as lead and mercury . They contaminate plants , and poison fish and irrigation and drinking water . They end up in the human food chain . The problem is not just caused by idols of Ganesha , but by the many other Hindu god idols as well , such as Saraswati and Durga . Hundreds of thousands of god idols are immersed every year in festivals across India . A detailed study of the problem has been done by Shyam R. Asolekar of the Indian Institute of Technology in Bombay . He estimates that , in the city of Mumbai alone , several hundred thousand idols are made annually . Watch a Hindu immersion ritual » . Decades ago , there were far fewer idols and idols were made of mud and biodegradable materials , Asolekar said . The effect also was `` minimal '' he said , because waterways were n't linked as they are now . As a result of water and irrigation projects , `` connected water systems and dams have reduced the flow of water '' and dramatically increased the effect of pollution . According to Asolekar 's study , `` Forbidding the disposal of painted idols , ornaments and decoration is the only sure way of protecting our water bodies . '' Various Indian states are testing out new approaches , such as mobile immersion tanks , and encouraging mud idols . Asolekar dismissed the idea of an eco-friendly idol , saying even large amounts of mud kill waterways . `` The number of idols is so high , '' he said , `` no matter what the material , there will always be an impact . Even organic substances in large quantities cause a problem . '' He suggests a `` dry immersion , '' in which the idol is sprinkled symbolically with water and then later dried for reuse . This approach would face great hurdles in a country where religious rituals have deep social and cultural ties and change comes slowly . Another possible interim measure uses a polymer-lined tank for immersion . More than 100 such tanks have been installed in Mumbai . The linings can be rolled up after use and the materials separated into bio and nonbiodegradable materials for composting and landfill . The water is filtered . But this solution is far from ideal , Asolekar said , as tens of thousands of such tanks would be needed , and there is still plenty of contamination . `` It will take time to change people 's attitudes , '' he said .
Hindu ritual of immersing idols in oceans , rivers and lakes is causing contamination . Paints on idols often contain toxic metals , such as lead and mercury . Pollutants contaminate plants , poison fish and irrigation and drinking water . `` Dry immersion '' suggested as a solution -- idol is sprinkled symbolically with water .