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Chemicals used to purify drinking water create toxic by-products

Chemical disinfectants used to make water safe to drink react with organic material in it, and yield toxic consequences, say researchers.

health and fitness Updated: Apr 01, 2009 17:32 IST

Chemical disinfectants used to make water safe to drink react with organic material in it, and yield toxic consequences, say researchers.

Michael Plewa, a geneticist at the University of Illinois, points out that disinfection by-products (DBPs) in water are the unintended consequence of water purification.

"The reason that you and I can go to a drinking fountain and not be fearful of getting cholera is because we disinfect water in the United States," he said.

"But the process of disinfecting water with chlorine and chloramines and other types of disinfectants generates a class of compounds in the water that are called disinfection by-products. The disinfectant reacts with the organic material in the water and generates hundreds of different compounds. Some of these are toxic, some can cause birth defects, some are genotoxic, which damage DNA, and some we know are also carcinogenic," he added.

Funded by the U.S. Environmental Protection Agency (EPA), the 10-year study was started with a view to developing mammalian cell lines that would be used specifically to analyse the ability of such compounds to kill cells, or cytotoxicity, and the ability of these emerging disinfection by-products to cause genomic DNA damage.

"Our lab has assembled the largest toxicological data base on these emerging new DBPs. And from them we''''ve made two fundamental discoveries that hopefully will aid the U.S. EPA in their regulatory decisions. The two discoveries are somewhat surprising," Plewa said.

His team’s first finding involves iodine-containing DBPs.

"You get iodine primarily from sea water or underground aquifers that perhaps were associated with an ancient sea bed at one time. If there is high bromine and iodine in that water, when you disinfect these waters, you can generate the chemical conditions necessary to produce DBPs that have iodine atoms attached. And these are much more toxic and genotoxic than the regulated DBPs that currently EPA uses," he said.

Plewa revealed that the study’s second discovery concerned nitrogen-containing DBPs.

"Disinfectant by-products that have a nitrogen atom incorporated into the structure are far more toxic and genotoxic, and some even carcinogenic, than those DBPs that don''''t have nitrogen. And there are no nitrogen-containing DBPs that are currently regulated," he said.

The researcher even said that apart from drinking water DBPs, swimming pools and hot tubs are also DBP reactors.

"You''''ve got all of this organic material called 'people' -- and people sweat and use sunscreen and wear cosmetics that come off in the water. People may urinate in a public pool. Hair falls into the water and then this water is chlorinated. But the water is recycled again and again so the levels of DBPs can be ten-fold higher than what you have in drinking water," he said.

According to Plewa, higher levels of bladder cancer and asthma have been observed in people who do a lot of swimming — professional swimmers as well as athletic swimmers.

These individuals have greater and longer exposure to toxic chemicals, which are absorbed through the skin and inhaled.

"The big concern that we have is babies in public pools because young children and especially babies are much more susceptible to DNA damage in agents because their bodies are growing and they''''re replicating DNA like crazy," he said.

Telling about a new project that his team is working on, Plewa said: "We're working with engineers and chemists to develop new technologies that will disinfect water, that will desalinate water, that will remove pharmaceuticals from water but in so doing, don't generate by-products that are even more toxic than the things you're trying to remove."

He suggests that until the development of new technologies to safely disinfect the water in public pools, education is needed to encourage people to bathe or shower before entering a public pool.

"It's the organic material that gets in the pool that is disinfected and then re-circulated over and over again. That's why we call swimming pools disinfectant by-product reactors. But by public education, by personal behaviour, there should be ways that we can reduce the levels of the dissolved organic material that should reduce the level of DBPs," he said.

A report on this study has been published in the journal Mutation Research.

First Published: Apr 01, 2009 17:29 IST