Coffee Filters Heavy Metals from Tap Water
SYDNEY, Australia, February 2, 2000 (ENS) - Filtered coffee can remove from 78 to 90 percent of dissolved heavy metals such as lead and copper from tap water, providing coffee lovers with a safer, healthier drink, an international scientific team has found.
Toxic metals like copper and lead get into drinking water from storage tanks, copper pipes and solder, and from natural sources, says Dr. Mike McLaughlin who works with the Land and Water division of the Australian government research arm, Commonwealth Scientific Industrial Research Organisation (CSIRO).
The softer the water, the higher the level of heavy metals in solution is likely to be.
Both copper and lead have long term toxic effects on humans, and lead is strongly linked to intellectual impairment, especially in infants and young children.
But coffee grounds have a remarkable ability to mop up the heavy metal atoms, research by the Australian, Chilean and U.S. scientists shows.
Their findings could mean that daily human exposure to heavy metals in many cities round the world may have been greatly overestimated.
This could mean that current public health risk assessment models are inaccurate where coffee forms a large proportion of water consumption.
"We were at a seminar at the University of Delaware, and a Chilean scientist, Dr. Gustavo Lagos, was presenting a paper on the problem of heavy metal contamination of drinking water in Santiago," Dr. McLaughlin recounts.
"I asked the question, 'How do people in Santiago actually drink the water?' because if, as I thought, they drank a lot of coffee, chances were the coffee would absorb a lot of the heavy metals."
As a result of Dr. McLaughlin's question, the researchers decided to run an experiment to find out exactly how much heavy metal does survive the coffee-brewing process, and how much is trapped in the grounds.
To their surprise, they found that normal filtered coffee removed 78 to 90 percent of copper and lead from the water, using three different commercial brands of coffee.
"The reason is that coffee grounds have uncharged or negatively charged molecules in them, whereas dissolved heavy metals are positively charged. As a result, the heavy metal ions bind strongly to the coffee," explains Dr. McLaughlin.
The deeper the bed of coffee in the drip-maker, the more effective the removal of heavy metals. We consider that the main factor influencing the extent of metal removal is contact time, the scientists found.
Dr. McLaughlin says that it is highly likely the process also removes other heavy metals such as mercury, cadmium and zinc from drinking water, although this remains to be tested.
"It is also possible tea-bags and tea leaves may work in the same way, but not as well as coffee," he says.
The researchers say the results of their study are important for formulating reliable risk assessment models for drinking water standards which protect the health of the public.
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