How Copper and Copper Alloys can Kill Pathogens in Minutes
By Loveday Hedgcock
In an age when preventing both infection and waste is topical, the need to find effective means of killing pathogens in sustainable ways becomes increasingly critical. One material that could be at the forefront of this ambition is Copper.
Copper has been helping to prevent infections for thousands of years. It was recorded in the Smith papyrus (an ancient Egyptian medical document from over 4000 years ago) as it was used to sterilize wounds and water. Babylonian soldiers are even said to have put the filings from sharpening their bronze swords into their injuries for the same reason. More recently, during the 19th century, it protected copper workers from three cholera outbreaks in
France. In this case a French doctor called Victor Burq made the connection in 1852 after visiting a copper smelting yard in Paris. None of the 200 workers, although extremely poor, had died of cholera in the outbreaks of 1832 and 1849.
Copper kills pathogens on contact by releasing copper ions which make holes in the cell membrane or virus coating. They also prevent the pathogen respiring, and destroy genetic material. The latter is particularly useful as it prevents mutations which could otherwise cause resistance to copper.
Copper even kills antibiotic resistant bacteria - super bugs - such as MRSA.
Copper is able to destroy pathogens in minutes or hours (depending on the pathogen), whereas they could remain active for days on other surfaces such as stainless steel, so copper is continuously helping to remove pathogens between cleaning times. Studies showed a 58% reduction in infection rates across three American Intensive Care Units when copper was used on frequently touched surfaces (Michael G. Schmidt, professor of microbiology and immunology at the Medical University of South Carolina).
Why isn’t copper more widely used? Partly this is a question of cost. But stainless steel, while less effective, is generally preferred as it has connotations of cleanliness due to its shiny appearance whereas copper oxidizes and turns green. Surprisingly, though, copper remains antimicrobial even after oxidation. Tests on railings in New York’s Grand Central terminal showed that copper was still able to destroy pathogens even 100 years after it was installed.
So how can we use copper to stop infections? Many doorknobs are made of brass which, as an alloy with a high copper content, also kills bacteria. So maybe you’ve been reducing infections without even knowing it.