A Study of Filters Best Way to Clean Tap Water

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TORONTO - Pitchers with activated-carbon filters are the most effective way to reduce potentially harmful chemicals in tap water, Canadian researchers say.

A team at Universite Laval in Quebec City researched ways to cut down on the two main byproduct chemicals produced when chlorine used to disinfect tap water reacts with organic matter normally present in it.

Research team member Manuel Rodriguez said the byproducts were suspected of increasing the risk of liver, bladder, and kidney cancer.

Rodriguez and his four teammates collected samples from private homes in the Quebec area and tested for byproducts known as trihalomethanes (THMs) and haloacetic acids (HAAs) and subjected them to three common forms of household treatment.

Storing water in a refrigerator for 48 hours reduced THMs by 30 percent, while boiling water before storage cut them by 87 percent. Using an activated carbon filtering pitcher prior to storage cut the byproducts by 92 percent.

Direct storage and boiling had no effect on HAAs, although filtering was found to reduce them by 66 percent.

Despite the results, Rodriguez said HAAs were probably within regulation levels in cities with adequate water treatment, making no additional home treatment necessary.

"However, if I lived in a place where there were regular notifications to boil water or if I knew the water contained high levels of HAAs, I'd consider using home water-treatment devices," he said.

He said levels of the chemicals were now limited by law in Canada, but some municipalities may still be upgrading water-treatment facilities to meet the new regulations.

"It is important that people are educated in the use of filtering, and the need for filters to be changed regularly," he said.

In October 2005, the province of Ontario airlifted about 1,000 residents of a remote community due to contaminated water on a native Indian reserve in which they lived.

The community's water had been contaminated by E. coli bacteria and residents are suffering from nausea, diarrhea, parasites, and blistered skin. Some conditions were due to high levels of chlorine used to treat the water.

The community had been under a boil-water order, on and off, for the previous five years.

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