One of copper's benefits appears to be backed by science--its antibacterial effect. Both ancient and recent evidence suggests that copper may be used as a water purification or sterilization system, as ancient Ayurveda techniques recommend (3, 4). Studies have shown that adding copper to drinking water can reduce the amount of bacteria such as Escherichia coli (E. coli) and Giardia lamblia by up to 99% for E. coli and 100% for Giardia. However, only high-quality copper products should be used to add copper to water because inexpensive materials may not be effective at reducing bacteria. Also, excessive amounts of copper can be toxic to humans. For these reasons, it is important to follow recommended concentrations of copper when using this approach to purify water. High levels of copper in water can cause serious health problems if you are exposed to it for long periods of time. For example, infants and young children are at risk for brain damage from excess copper because their immune systems are not yet fully developed. The U.S. Environmental Protection Agency (EPA) recommends that individuals do not consume more than 15 milligrams of copper per day, which is equivalent to about 1 teaspoon of copper salt. However, some studies suggest that levels as high as 10 grams per day may cause adverse effects.