Research shows that manipulated wood is more resistant to microorganisms than plastic

When you imagine a hospital, you might imagine concrete, stainless steel, or plastic. However, researchers at the University of Oregon hope that in these settings, they will create wood that is often overlooked in healthcare facilities.

The exposed wood they discover may resist microbial growth after it gets temporarily wet. During their study, wood samples were tested lower for levels of bacterial abundance than empty plastic enclosures used as controls.

“People generally think of wood as unhygienic in a medical environment,” said Professor Mark Fletz, co-director of UO’s Institute for Health and Environmental Research and Professor Mark Fletz, the research principal investigator. “But wood actually permeates microorganisms at a lower rate than other porous materials such as stainless steel.”

Many studies support these properties of wood. A UO-led research team, including scientists from the Salk Institute for Biological Studies and Portland State University, wanted to explore what happens when wood gets wet and dry.

In a recent study published in the Frontier of the Microbiota, they shared their findings on the effects of moisture on the discharge of volatile organic compounds from surface microorganisms and mass wood.

Mass material is a wood material designed to emerge as a popular construction alternative in the United States, but exposed wood is rarely used in medical facilities. That is partly due to strict building codes that have slow evolution, Flets said. Another reason: broad misconceptions about wood and pathogens.

“We wanted to explore how mass wood can withstand the everyday rigour of a healthcare environment,” said Gwynne Mhuireach, assistant research professor at UO. “Bacteria are constantly present in hospitals and clinics, and surfaces can sometimes get wet.”

For experiments, blocks of crosslinked wood were sealed in disinfected plastic boxes to create a microenvironment with carefully controlled temperatures and humidity. To simulate a healthcare setting, the air was filtered and replaced at a similar rate to the hospital code.

The team sprayed the blocks with tap water, inoculated them with a cocktail of microorganisms commonly found in hospitals, and sampled them for four months. An empty plastic box was used as a control.

Researchers compared wood samples coated with three different water spray events and uncoated wood samples. Every day in one week, every day in four weeks.

The results of this study showed that wood was effective in inhibiting bacteria and revealed cues regarding wetting that signal future research and development, Mhuireach said.

The empty plastic control box had a greater viable microorganism abundance than the wood samples, except for the first 14 days after inoculation.

Wetting wood blocks reduced the abundance of viable bacterial cells, and there was no discernible difference between uncoated and non-fluoroscopic specimens. During wetting, the composition of the microorganisms reflects more common in tap water than in hospital pathogens the team introduced.

The experiment was the first to investigate the relationship between microbial communities on crosslinked wood surfaces and the release of volatile organic compounds or VOCs under dry, wet conditions, Mhuireach said.

VOCs are chemicals that spread quickly into the air and cause a variety of odors, such as perfumes, mold, or “new car smells.” Some of them can cause current health hazards, while others can be beneficial.

Wood can release compounds called terpenes. Many smell pleasant and inhibit microorganism growth. Mhuireach added that there is a plateau in VOC emissions after wetting. This was interpreted as a slight increase by the team compared to the overall downward trend.

This study presents another milestone in UO’s work to promote the use of mass wood in healthcare facilities. That effort began in 2020 and led to the formation of a focus group that includes architects, engineers and healthcare building code experts.

Through work with the Tallwood Design Institute, a collaboration between UO and Oregon State University, Fretz has been working to promote the production and use of mass wood, including materials manufactured in Oregon.

Construction using engineered wood produced from veneer or timber bridge layers that began in Europe in the mid-1990s and are growing in the US.

Mass material, which is stronger per pound than steel or concrete, boasts a smaller carbon footprint. Exposed wood also promotes health and healing, Flets said.

The benefits of its human characteristics, what architects and designers call biological organisms, go beyond mere aesthetics.

Many studies have linked biophysiological design to better healthcare outcomes, including shorter hospital stays, faster healing, and mental health.

Wood’s ability to inhibit the spread of pathogens may be derived from pores that catch naturally occurring bacteria or antibiotic compounds, Flets said. It can also be attributed to the wood’s ability to absorb moisture.

Respiratory viruses move indoors in water droplets. Wood drys its droplets faster than plastic or stainless steel, reducing the survival time of the virus.