[GRRN] article on coffee & metal absorption in Environmental Health Perspectives July 2000

From: Stephanie C. Davis (ScD18@WasteReductionRemedies.com)
Date: Mon Oct 02 2000 - 17:13:22 EDT

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    Environmental Health Perspectives Volume 108, Number 7, July 2000
    There is no such thing as a "national" environment.
    Our growing economic interdependence provides the context for
    global cooperation in dealing with the global ecosystem.
    John Naisbitt, Utne Reader, November-December 1989

    New Grounds for Drinking Coffee

    New information suggests that your morning cup of coffee may be a healthy
    part of a nutritious breakfast. Research by an international team of
    scientists published in the April 2000 issue of Human and Ecological Risk
    Assessment has shown that automatic drip coffee makers can remove up to 85%
    of both copper and lead in tap water. Team leader Herbert E. Allen, a
    professor of civil and environmental engineering at the University of
    Delaware in Newark, speculates that coffee grounds retain heavy metals
    through surface chelation, a chemical reaction in which metals form
    complexes with organic matter. After looking at ion exchange or adsorption
    as possible filtering mechanisms, Allen says that due to coffee's
    nature--coffee grounds having uncharged or negatively charged
    molecules--surface chelation most likely explains the large percentage of
    metals removed. Because dissolved heavy metals are positively charged, the
    metal ions bind strongly to the coffee, he says.
    The study was conducted by Allen, graduate student Christopher
    Impellitterri, Michael McLaughlin of the division of soils at the
    Commonwealth Scientific and Industrial Research Organisation in Adelaide,
    Australia, and Gustavo Lagos, a scientist at the Pontificia Universidad
    Católica de Chile in Santiago. After attending a seminar about copper in the
    human diet presented by Lagos, the group speculated that the amount of
    copper in prepared coffee would be less than the amount present in the water
    used to make the coffee, and they decided to conduct a study to test their
    idea.
    In order to simulate home coffee brewing as closely as possible, the team
    studied three commercial coffee brands using a coffee maker with a
    basket-type paper-lined filter and a 12-cup-capacity glass carafe. For the
    first batch of each brand, the team began with the standard amount of coffee
    recommended by the manufacturer (one teaspoon per cup) and then adjusted
    that amount to 30 grams of coffee per liter of water, a strength they agreed
    was satisfactory. From each first batch, four samples were taken for both
    metal and pH analysis to establish a baseline value for the amount of copper
    and lead in an average pot of each brand of brewed coffee. The team prepared
    additional batches at different volumes (but maintaining the coffee-to-water
    ratio) and using different concentrations of coffee to produce stronger
    brews. They also ran normal and metal-spiked solutions through the coffee
    maker both with and without a paper filter to assess sorption by the coffee
    maker and the filter.
    The results of the team's research suggest several reasons for the lead and
    copper removal. When increasingly stronger batches of coffee were brewed, an
    increase in metal removal was observed, probably because of the increased
    contact time between the coffee and the water as it seeped through a thicker
    bed of grounds. People who prefer stronger coffee may be enjoying a greater
    decrease of the metals, the team says, since the stronger the coffee is
    brewed, the more metals may be removed. But after comparing the strongest
    batches and noting no additional removal of metals, they decided to continue
    the search for additional factors.
    The team then varied the coffee grounds' consistency. They found that coarse
    coffee grounds removed 73% of the copper and 79% of the lead. In comparison,
    finely ground coffee powder removed 90% of copper and 91% of lead,
    suggesting that the increased surface area of the smaller grounds enhances
    removal of the metals. A moister bed of coffee also increased how much metal
    was adsorbed, as demonstrated by collecting samples of the coffee as it
    passed through the coffee bed and comparing their metal concentrations to
    those of the finished pot. Allen says that sorption of the metals may also
    occur on interior surfaces of the coffee maker, paper filter, or glass
    carafe.
    Although Allen says that the metal removal could actually be much higher
    worldwide for those who drink coffee, depending on cultural and personal
    tastes in coffee preparation, he says that the team's findings are important
    to current human exposure assessment estimates of copper and lead in tap
    water. Current estimates for metal exposure could be much higher than actual
    levels for people whose main tap water intake is through coffee.
    -Lindsey A. Greene
    ------------------------------------------------------------------------

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    Experienced Professional of Healthcare &
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