Silver Showerheads May Promote Biofilms & Resistance

To protect against hazardous waterborne germs, many consumers, including health-care facility management, install antimicrobial silver-containing shower heads. However, in ACS ES&T Water, researchers claim that these fixtures are not a “silver bullet.” Most bacteria are not destroyed by silver exposure under normal bathing circumstances. However, the composition of uncommon microorganisms in the water from these showerheads differed depending on the type of fixture analyzed.

The stream of droplets and fine mist produced during a rainfall can be breathed or swallowed. Installing showerheads containing silver, a naturally antibacterial metal, is an inexpensive technique to potentially guard against drinking water-associated infections (DWPIs). DWPIs, like as the strains Pseudomonas and Legionella, can infect persons with weakened immune systems. However, studies have previously indicated that lowering DWPI by adding copper and silver to a building’s water system to kill germs and viruses (i.e., copper-silver ionization) is a temporary or minor solution. The findings of the copper-silver ionization study have aroused concerns among scientists that short-term silver exposure in showerheads may instead reinforce bacteria, increasing the chance of antibiotic resistance rather than reducing it. So, Sarah-Jane Haig and her colleagues sought to investigate how silver-containing showerheads altered the microbiological composition of water.

The researchers compared two typical showerheads made of plastic or metal to three fixtures containing silver: a silver mesh within the showerhead, a silver-coated copper mesh in the showerhead and hose, and a silver-embedded polymer composite. The showerheads were tested at Haig’s full-scale shower lab facility, which was designed to simulate real-world settings.

Contrary to product claims, silver did not diminish overall DWPI concentrations or total bacteria in water samples from the researchers’ shower lab. Haig and her team concluded that this was due to discrepancies in their testing settings versus those of the manufacturers. More specifically, in this investigation, the water flowed out of the showerhead in a rush, just like when someone takes a shower. However, the conventional tests performed by manufacturers expose microbe cultures to the silver substance alone for 16 to 24 hours, which the team claims is neither acceptable nor realistic.

The total pathogen concentration in water samples did not differ between ordinary and silver showerheads, but the microbiome makeup did. The populations differed for each of the silver-containing fittings, indicating that how the silver was incorporated into the showerheads was important, with rare bacteria accounting for the majority of the changes. Further research by the researchers suggests that microorganisms in silver-containing showerheads may be more likely to develop microbial colonies known as biofilms in reaction to the stressful environment. Biofilms may also explain the relationship between the number of various species and showerhead age, according to the researchers, because these communities serve as reservoirs for DWPIs.

“These findings underscore the need for improved testing standards, real-world performance evaluation, and innovative solutions to mitigate microbial risks in water systems, benefiting consumers and vulnerable populations,” says Haig.