Thus, coffee drinkers absorb fewer heavy metals from the water. According to the researchers, coffee grounds contain uncharged and negatively charged molecules, while dissolved heavy metals are positively charged. Thus, they bind well to the coffee, causing large amounts of lead and copper to get stuck in the coffee grounds as the water runs through. The more coffee the researchers put in the filter, and the longer the water took to run through it, the more effective the removal of heavy metals.
Additional experiments are to show whether mercury, cadmium and zinc also are bound by the coffee.
The 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 significant proportion of water consumption.