about 250 million people in urban India drink municipal water, which is treated and disinfected before being supplied. A recent study shows the chemicals used for treatment methods might give the water a different set of harmful characteristics. Surface water, which contains microorganisms like bacteria, algae and suspended organic matter, is made potable for human consumption using chemicals such as chlorine, alum, potassium permanganate, polyphosphate, lime and other coagulants.
Researchers studied the effects of treated water on a particular species of yeasts, which is similar to mammalian cells with respect to growth. They found that the chemicals used to treat water damage the cells of the yeast species Schizosaccharomyces pombe. "The chemicals damage the dna structure of the yeast," says Soumendra N Talapatra, the lead researcher from the department of biochemistry, Calcutta University. The study was published in the January 2008 issue of Food and Chemical Toxicology (Vol 46, No 1).
The researchers collected drinking water samples from several areas of Kolkata and exposed yeast cells cultured in the lab to them. The dna, they observed, resembled a comet with a distinct head, the nucleus and a tail containing fragments of dna. Scientists say comet formation is a sure sign of cell damage.
Coagulants, which contain poly-diallyl dimethyl ammonium chloride, are used to treat raw water to make it potable. "The coagulant breaks down to form allyl chloride, which affects the cell and is also a potent carcinogen," says Dhrubajyoti Chattopadhyay, a co-researcher from B C Guha Centre for Genetic Engineering and Biotechnology, Calcutta University.
Chattopadhyay says about 50 genes of S pombe are associated with human diseases, and of the 50, malfunction of 23 can lead to cancer. "The study may have far-reaching implications regarding human health. S pombe should be routinely used as a model to test purity of water samples," he adds.
A who report points to increased risk of bladder cancer with the consumption of chlorinated tap water. Another study in central Wisconsin, usa, showed rise in bad cholesterol levels in communities using chlorinated water. "Though chlorination is essential to kill the disease-causing bugs present in surface water, indiscriminate chlorination increases the risks for human health," says Santanu Ray of Visva-Bharati University, Santiniketan, West Bengal. Ray studies fluoride contamination in water.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.