In a surprisingly short time, the COVID-19 pandemic has upended life as we know it. Many architects and designers now work remotely while sheltering in place, doing our part to “flatten the curve” and reduce pressures on health care services. Meanwhile, researchers are studying COVID-19 at a breakneck pace, with some scientists demonstrating the virus transfers not only between two people, but also between exposed surfaces and individuals. This finding has created a general surface phobia, characterized by a fear of door handles, handrails, and other high-contact objects.
Not all materials offer a lasting home for viruses, however, and architects can put this knowledge to use—particularly when designing spaces for more vulnerable occupants.
In a study published earlier this month in The New England Journal of Medicine, U.S. National Institutes of Health virologist Neeltje van Doremalen and her co-authors found that SARS-CoV-2 (the virus responsible for the COVID-19 illness) survives for two to three days on surfaces like plastic and stainless steel—a concerning fact for health care workers in facilities that largely feature these materials. The researchers assessed the decay rates of viruses aerosol sprayed onto these surfaces, as well as onto copper and cardboard. They reported that the virus can remain active on cardboard for up to 24 hours, while it dies the quickest on copper, lasting around four hours.
In fact, researchers have promoted the use of copper to slow the spread of other acute respiratory diseases, like SARS and MERS in recent years. Copper and its alloys such as bronze or brass are inherently antimicrobial, disrupting key cell functions once the metals are exposed to bacteria or viruses. Studies have shown that E. coli survive less than 90 minutes on a copper surface at room temperature. In contrast, the bacteria exhibit no signs of reduced viability after 270 minutes on stainless steel. The same New England Journal of Medicine study indicates a similar response, although for a longer duration, in the novel coronavirus. Not only is SARS-CoV-2 rendered inactive within four hours on copper, but SARS-CoV-1—the “most closely related human coronavirus”—also becomes inviable within eight hours.
Cardboard’s relative inhospitality to viruses is also intriguing. “We speculate due to the porous material, [the virus] desiccates rapidly and might be stuck to the fibers,” said Rocky Mountain Laboratories virologist Vincent Munster, a co-author on the NIH study, in a BBC interview. “[We’re] currently running follow-up experiments to investigate the effect of temperature and humidity in more detail.” The U.S. Centers for Disease Control and Prevention corroborates this finding, reporting that “there is likely very low risk of spread from products or packaging that are shipped over a period of days or weeks at ambient temperatures.” Although cardboard is not a typical material used in architecture (unless you are Shigeru Ban, Hon. FAIA), other similarly porous and fibrous materials may exhibit similar performance with regard to virus survivability. However, more research is required to determine specific viral death rates on different materials.
Although not included in the NIH study, antimicrobial coatings are commonly used to eliminate viruses on material surfaces such as doorknobs, countertops, and wall surfaces. A swiftly growing industry —now valued in the billion-dollar range—has quietly and rapidly formed around such coatings. While some paint manufacturers have added microbe-killing agents to paint and primer coatings, other manufacturers have created coatings leveraging other chemical capabilities. For example, organosilanes are silicon-based nanocoatings that form a highly-abrasive surface for viruses and bacteria, effectively ripping them apart. Meanwhile, the chemical compound quaternary ammonium, typically used in disinfectants, causes cell leakage and eventual death of microbes. Other strategies include photocatalytic and superhydrophobic coatings, which both exhibit self-cleaning functionality.
While these substances hold potential, concerns remain over an increased prevalence of chemicals in the built environment. For example, when the CDC found “no evidence to suggest the products offer any enhanced protection from the spread of bacteria and germs, and that proper cleaning and hand washing are the best ways to prevent infection,” Oakland, Calif.–based healthcare provider Kaiser Permanente issued a ban on 15 antimicrobial chemicals used in interior applications. It is unclear whether or not the mechanical approach—seen in promising advances such as the bioinspired nanostructured antimicrobial surfaces developed by U.K.–based University of Bristol and Bengaluru, India–based Indian Institute of Science researchers—will be encouraged as an alternative to chemical antibiotics. In the meantime, architects can support more research on naturally microbe-inhibiting materials and remind their clients that adequate cleaning and hand washing remain the best practices for maintaining microbe-free environments.
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