DO the gods pollute? Scientists in India, worried about the public health consequences of immersing idols in lakes and rivers, have been looking anew at water pollution. They hope to harmonise their medical concerns with some people’s religious priorities.

Most of their research has focused on idols of the elephant-headed god Ganesh, created for the annual Ganesh Chaturthi celebration. Once a fairly quiet, mostly private practice, Ganesh Chaturthi now involves large, public festivals in many parts of India. Researchers have also looked, a little, at the effects of immersing other idols, especially those of the many-armed goddess Durga.

One of the latest studies is called Assessment of the Effects of Municipal Sewage, Immersed Idols and Boating on the Heavy Metal and Other Elemental Pollution of Surface Water of the Eutrophic Hussainsagar Lake (Hyderabad, India).

A team sampled water repeatedly from different parts of the lake, including one spot “immersed with hundreds of multicoloured idols of Lord Ganesh and Goddess Durga”, and another near “the outfall of black-coloured, untreated raw sewage containing a collection of industrial effluents”. Sewage, they conclude, accounts for most but not all of the pollution. High levels of zinc, calcium and strontium “were probably due to the immersed idols painted with multicolours”.

Some studies concentrate on isolating the effects of idols from those of other sources. Impact of Ganesh Idol Immersion Activities on the Water Quality of Tapi River, Surat (Gujarat, India) tells of sampling the water “at morning hours during pre-immersion, during immersion and post-immersion periods of Ganesh idols”. The conclusion: the “main reason of the deterioration of water quality . . . is various religious activities”, with special blame given to “the plaster of paris, clothes, iron rods, chemical colours, varnish and paints used for making the idols”.

Heavy Metal Contamination Cause of Idol Immersion Activities in Urban Lake Bhopal, India, published in 2007, finds that idol immersion has become “a major source of contamination and sedimentation to the lake water”.

It warns that idol-derived heavy metals are likely to find their way into “fishes and birds inhabiting the lake, which finally reach the humans through food”. The authors want to “educate idol makers” to make their idols small, of non-baked, quick-dissolving clay, and with “natural colours used in food products”. — The Guardian, London