Brass is an alloy of copper and zinc. Specific types of brass are antimicrobial, meaning they can kill microorganisms such as bacteria and viruses on contact. This powerful, self-sanitizing capability is directly linked to the presence of copper within the alloy structure. This characteristic positions certain brass surfaces as a tool for reducing the spread of pathogens, particularly in high-traffic environments.
The Required Copper Content in Brass
For brass to function as an antimicrobial surface, its composition must include a substantial percentage of copper. The antimicrobial efficacy of any copper alloy, including brass, is directly proportional to its copper concentration. This means that not all brass alloys possess the necessary pathogen-killing power.
The U.S. Environmental Protection Agency (EPA) has registered hundreds of copper alloys for public health benefits. These alloys must contain a minimum of 58% to 60% copper to qualify for antimicrobial claims. This registration allows products made from these specific formulations to be marketed with claims of continuous antibacterial action. The copper atoms must be present in high enough density to ensure the continuous release of ions that interact with microbial life. Alloys with copper content lower than the required threshold will not exhibit the same level of rapid and effective microbial reduction.
The Science Behind the Kill: Oligodynamic Effect
The process by which brass eliminates microorganisms is known as the oligodynamic effect, which is the biocidal action of metal ions at very low concentrations. This effect begins when copper atoms on the surface of the alloy release electrically charged copper ions into the thin layer of moisture on the surface. These ions are the active agents that attack microbial cells.
Once a microbe lands on the brass, the released copper ions rapidly penetrate its outer membrane, a process often called “contact killing.” The ions then disrupt several functions within the cell. Specifically, copper ions interfere with the cell’s respiration and metabolism, preventing it from producing energy. The ions also damage the microbe’s DNA and RNA, blocking the ability of the cell to replicate or repair itself, which quickly leads to cell death.
Practical Applications and Real-World Efficacy
The antimicrobial action of brass makes it an effective material for high-touch surfaces in public and healthcare settings. Common applications include door handles, push plates, railings, bed rails, and sink faucets. Studies in real-world environments, such as hospital intensive care units, have demonstrated that introducing copper alloy surfaces can significantly reduce the bacterial bioburden.
Laboratory testing conducted under EPA protocols shows that registered antimicrobial copper alloys kill greater than 99.9% of specific disease-causing bacteria within two hours of exposure. This rapid destruction includes resilient pathogens like Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Brass provides continuous antibacterial action, meaning it keeps killing microbes between routine cleanings and does not require chemical intervention to remain effective.
Comparing Brass to Other Common Touch Surfaces
The antimicrobial properties of brass provide a distinct advantage over more commonly used surfaces like stainless steel, plastic, and aluminum. While these materials are easily cleaned with disinfectants, they do not possess any inherent ability to kill microbes on their own. Pathogens can survive and multiply on stainless steel and plastic for days or even weeks, turning these surfaces into reservoirs for transmission.
Brass, however, passively eliminates microbes, making it a self-sanitizing surface. Research comparing brass directly to stainless steel has consistently shown that brass exhibits greater antimicrobial activity against various opportunistic pathogens. This passive, continuous killing action is a benefit that non-antimicrobial surfaces cannot replicate, positioning brass as a valuable tool for public health infection control strategies.