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Delhi water carcinogenic: CPCB

india Updated: Nov 11, 2006 01:54 IST

The water that flows out of the taps in Delhi is a cocktail of carcinogenic substances. A study conducted by the Central Pollution Control Board (CPCB) on the levels of toxic substances called total trihalomethanes (TTHM) in tap water has revealed shocking results.

Over the past six months, the CPCB tested water collected from 30 locations in the capital. It found that the levels of TTHM were four to five times the World Health Organisation (WHO) standards. While the TTHM levels considered safe by the WHO are 60 micrograms per litre, in the United States they are 80.

TTHM is the sum of organic substances like chloroform, bromoform and bromodichloromethane which cause cancer.

The water-treatment process is to blame, says a CPCB official. Trihalomethanes are formed when chlorine reacts with small concentrations of naturally occurring organic material — and the Yamuna has a high level of those. TTHMs are also formed during the water-distribution stage when chlorine reacts with metals.

Dr Anil Bansal of the Delhi Medical Council says that when the concentration of TTHM is more than 0.46 milligram per litre, the water can cause cancers of the colon, rectum and bladder and miscarriages. Studies worldwide have shown that drinking TTHM-laced water or even bathing in it can lead to health problems. "Cancer is the greatest among the possible TTHM risks," says Dr John Capece, in his recent study published in Southern Datastream, a US medical journal.

While the battle against TTHM is yet to start in India, many western countries have adopted water-purification processes to lower TTHM levels. The US follows a five-level purification process as compared with a three-level system in India. "The US's additional levels of chemical treatment and ozonation kill TTHMs," says a CPCB scientist.

The CPCB's TTHM testing was the first of its kind in Delhi and was done at its new National Organics Trace Lab, set up with the help of German development agency GTZ. The details of the study will be published in the December edition of Parivesh, the CPCB newsletter.

Email Chetan Chauhan: cchauhan @hindustantimes.com

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