Water and health experts have raised doubts about Delhi Jal Board's (DJB) claim of supplying pure water, when it is carrying out quality tests for less than required parametres for samples from its distribution network.
Over exposure to pesticides and metals such as lead, chromium, cadmium - not tested on a daily basis - can be toxic and a potential health hazard, causing carcinogenic diseases, experts have warned.
The DJB claimed that water is tested for physico-chemical and bacteriological parametres. After a series of reports on water contamination in HT this week, the DJB stated that its water is "absolutely safe, potable and free of any contamination".
Sanjam Chima, DJB's consultant (PR), in a rebuttal said: "The number of samples taken as part of water quality surveillance was commensurate with the norms prescribed by Central Public Health and Environmental Engineering Organisation (CHEEPO)". She claimed that the water quality is maintained as per BIS standards IS: 10500:2003.
Himanshu Thakkar, a water expert, however, pointed out that the key to CHEEPO norms was a credible distribution system, ensuring total representation of the population and lifting of samples in a proper manner with community's involvement. "None of this is true here," he said.
Also, when IS: 10500: 2012 rules are in place, why has the DJB not migrated to that level from the 2003 norms, he asked.
Chima also claimed that water is tested for physico-chemical and bacteriological parameters. But CPHEEO manual talks about "essential characteristics" and "desirable characteristics". Under the second category, tests are carried out for calcium, magnesium, iron, copper, zinc, fluroids, nitrates and for toxic-chemical substances lead, arsenic, mercury, chromium and selenium.
"For samples from distribution network, no tests are done for presence of pesticides or metals on a daily basis," a source said. Water contamination is evident more at the level of distribution network where residents complain of the mixing of sewage with drinking water (see story on Hauz Rani).
The harmful metals enter humans through skin route or inhalation and by direct consumption. Water contamination is usually the most common mode of exposure. Continued consumption of water laced with heavy metals beyond permissible limits can lead to diarrhoea, ulcers, abdominal pain, indigestion, vomiting, and chest discomfort among other things.
"Lead can contaminate drinking water through corroded supply pipes. Lead toxicity can lead to abdominal ulcers, behavioural changes, learning disability, rise in blood pressure, miscarriages, etc," said Dr MP Sharma, head, department of gastroenterology, Rockland Hospital.
Prolonged exposure to these metals can even cause respiratory problems and damage the lungs, said Dr Neeraj Jain, chest specialist, Sir Ganga Ram Hospital.
Chima and Debashree Mukherjee, Delhi Jal Board chief executive officer, both did not respond.