Remember when doorknobs were made from copper or brass and cutlery was made from silver? As it turns out, these frequently touched items were made from these metals quite deliberately and for a very good reason. In this blog post, we’ll describe the amazing anti-bacterial properties of copper which are a result of a natural phenomenon known as the “oligodynamic effect”.
Copper has been used since ancient times to disinfect and purify water. In addition, several recent studies have established that copper surfaces may have practical applications in healthcare as well as in the food industry. Copper is an essential element in the human diet and is considered safe for humans when consumed at low levels. However, while humans are not susceptible to copper, microorganisms such as harmful bacteria are very sensitive to the presence of copper, and, in fact, show rapid inactivation when exposed to copper surfaces. As a result, copper pitchers can be very effective at purifying water and eliminating water-borne pathogens.
Various studies have shown that water pitchers made from copper were effective at removing bacteria from water. For example, in one recent study scientists studied the effect of a copper pitcher on drinking water contaminated with dangerous bacteria including E.coli and salmonella. The scientists stored the contaminated water in the copper pitchers for 16 hours at room temperature, and to their amazement, were later unable to recover any bacteria from the water.
In another recent study, researchers studied the best method to remove biological contamination from drinking water for domestic use. In particular, the researches stored contaminated drinking water in a variety of different water pitchers made from copper, silver, clay, and plastic. The study revealed that the copper pitcher was the most effective at removing the bacteria in the water and that there was a very significant inhibitory effect on the bacteria after only a few hours of storage in the copper pitcher.
In yet another recent study, scientists contaminated water with bacteria and then stored the water overnight at room temperature in both copper water pitchers and glass bottles. When examined in the morning, the bacteria was no longer present in the water that had been stored in the copper water pitchers, although the bacteria was present in the water stored in the glass bottles.
This phenomenon is known as the oligodynamic effect, which one recent study defines as “the ability of small amounts of heavy metals to exert a lethal effect on bacterial cells.” In particular, certain metals including copper have been found to effectively sterilize themselves after a certain period of time, which makes them ideal metals for water pitchers and doorknobs. Copper is a unique metal in this regard, as certain other metals, such as stainless steel and aluminum, do not have a significant effect on harmful bacteria.
But how does the oligodynamic effect work? While the mechanism is not yet fully understood by modern science, studies suggest that copper ions cause membrane damage to bacteria by affecting the protein in the bacteria’s cell walls thereby resulting in their precipitation and inactivation.
The results of these studies support the ancient ayurvedic practice of storing water in copper vessels. Significantly, the U.S. Environmental Protection Agency has registered copper as the only solid surface material able to kill bacteria that may pose a threat to human health. As a result, copper is now being considered in further applications where bacteria control is a concern, such as hospitals. In fact, many hospitals have begun equipping their patient rooms and operating rooms with copper alloy surfaces, replacing bed rails, tables, and door knobs. In fact, studies have shown that such changes can help reduce the number of healthcare-acquired infections in patients by more than half.
The next time you touch a stainless steel doorknob, be warned that this metal can be a major source of bacteria, some surviving for more than a month. In fact, recent studies of hospital doorknobs have found that copper doorknobs impeded bacterial growth, while aluminum and stainless steel permitted bacteria to run wild. In fact, within 15 minutes the copper doorknob had already partially disinfected itself. Perhaps copper doorknobs will become popular once again, all thanks to the ogliodynamic effect.