The Environmental Protection Administration (EPA) yesterday suggeted that people boiling water at home should take the lid off the kettle for the last three to five minutes as it helps release trace carcinogens.
“Tap water contains substances such as humic acid, which after boiling becomes trihalomethanes (THMs). The concentration of these can be reduced 10-fold if you open the lid and boil the water for another three to five minutes,” said Yuan Shaw-ying (袁紹英), director-general of the EPA’s department of environmental sanitation and toxic substance management.
The extra boiling time also gives tap water a crisper taste and reduces remnant chloride levels, he said.
THMs are a group of chemical compounds similar to methane in which three or four of the hydrogen atoms are replaced by halogen atoms, Yuan said, adding that common THMs include chloroform and bromoform.
Though it is not common for THMs to naturally exist in water, the toxins can be produced when organic compounds in water interact with chloride used for deodorization and disinfection purposes at water purification plants, he said.
“The most common THM in tap water is chloroform, which contributes to 75 percent of human THM consumption from drinking water,” Yuan said.
When ingested by humans, the compound can impair the central nervous systems and affect liver and kidney functions, Yuan said. Acute toxic reaction to chloroform can cause loss of consciousness, coma or even death, he said.
Long-term consumption of trace amounts of THMs is equally grim, he said.
“Chloroform and bromodichloromethane have been classified by the WHO’s International Agency for Research on Cancer in 1993 as possible carcinogens [Group 2B], and in a US EPA report published in 1997, exposure to Group 2B pollutants in the environment were correlated to increased risks of cancer of the bladder, liver, kidney and central nervous system,” he said.
However, Yuan also said that the public needed not panic — or flock to stores to purchase domestic water filters —as the nation’s water safety is above par.
“In the past five years, THM concentration, in Taiwan’s tap water has been reduced to 0.02 milligrams per liter, which is far lower than the recommended safety standard [of 0.08 milligrams per liter], which the EPA adopted from US EPA and WHO regulations,” Yuan said, citing research data produced by the EPA’s National Institute of Environmental Analysis.
To further eliminate any doubts over drinking water safety, the public could follow the open-lid policy, especially after typhoons or heavy rains when water in reservoirs becomes murky, he said.