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University Warns About Antimicrobial Paints

Monday, May 6, 2019

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Though antimicrobial paints claim to offer extra protection against bacteria, researchers at Northwestern University (Evanston, Illinois) are cautioning that the coatings might be doing more harm than good.

In a recent study, a team of researchers tested common household bacteria on samples of drywall coated with an antimicrobial, synthetic latex paint. Although almost all the bacteria were destroyed within a 24-hour-period, Bacillus timonensis—a spore-forming bacterium—remained.

What Makes This Dangerous?

Since most bacteria is known to thrive in warm, wet areas, it typically doesn’t survive long when transferred to dry and cold indoor surfaces. This caused study lead Erica Hartmann, an assistant professor of civil and environmental engineering in Northwestern’s McCormick School of Engineering, to question if the use of antimicrobial paints was causing the bacteria to become stronger.

Northwestern University, McCormick School of Engineering

Though antimicrobial paints claim to offer extra protection against bacteria, researchers at Northwestern University (Evanston, Illinois) are cautioning that the coatings might be doing more harm than good.

“If you attack bacteria with antimicrobial chemicals, then they will mount a defense,” Hartmann explains.

“Bacillus is typically innocuous, but by attacking it, you might prompt it to develop more antibiotic resistance.”

Since Bacillus is a spore-forming bacteria, it can protect itself by falling dormant for a period of time. During this period of self-protection, the bacteria becomes highly resistant to even the harshest conditions. Once said conditions lighten up, the bacteria reactivates.

Hartmann continued to add, “We should be judicious in our use of antimicrobial products to make sure that we’re not exposing the more harmless bacteria to something that could make them harmful.”

According to Northwestern’s report on the study, the problem with antimicrobial products—such as these paints—is that they’re not tested against more common bacteria.

Although a manufacturer will test the survival rate of pathogenic bacteria on these coatings, they fail to test bacteria that people (and the products they use) are more likely to encounter.

“E. coli is like the ‘lab rat’ of the microbial world,” Hartmann said. “It is way less abundant in the environment than people think. We wanted to see how the authentic indoor bacteria would respond to antimicrobial surfaces because they don’t behave the same way as E. coli.”

The study, “Impacts of Indoor Surface Finishes on Bacterial Viability,” was published online April 13 in Indoor Air. It was supported by the Alfred P. Sloan Foundation (award number G-2016-7291) and the Searle Leadership Fund.


Tagged categories: Antibacterial coatings; Colleges and Universities; Good Technical Practice; Latex; NA; North America; PaintSquare App - Commercial; Research; Research and development

Comment from David Darling, (5/22/2019, 7:06 AM)

This article was largely based on a press release issued by Northwestern University touting work done by their researchers. However, the American Coatings Association finds that the scientific statements made in the release do not accurately represent the findings of the research. The press release states that “antimicrobial paints may prompt bacteria to develop more antibiotic resistance,” but a closer reading of the research paper indicated that while the investigators specifically looked for antibiotic resistance they found no evidence. The paper states: “In this particular case, the exposure to antimicrobial surfaces did not explicitly select for antimicrobial-resistant microbes…” Further, the findings of the Hu paper did not demonstrate increased resistance to either antibiotics or antimicrobials. Similarly, the press release made another misrepresentative statement, specifically the “study shows antimicrobial paints might do more harm than good.” While the Hu paper did note that “a non-pathogenic bacteria might form spores on a paint surface,” this is far from an indication of demonstrating potential harm.

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