Friday, 31 January 2025
Dr Stephanie Taylor, MD, M. Arch, Infection Control Consultant, Harvard Medical School; ASHRAE Distinguished Lecturer; and Member, ASHRAE Epidemic Task Force, elaborates on how RH 40%- 60% is essential for reducing infection and on the need to put human health at the core of design intent of buildings…
Dr Stephanie Taylor
“The health of the public is in the hands of building professionals, much more than clinicians – that’s my experience and opinion as a physician and someone who now works in architecture.”
These were the opening words of Dr Stephanie Taylor, who served as Chairperson of the third edition of CPI Industry’s IAQ Webinar series: ‘The Air We Breathe’, drawing from her experience as an Infection Control Consultant for the Harvard Medical School and as a Member of the ASHRAE Epidemic Task Force.
For Dr Taylor, COVID-19 is a wakeup call that refocused the building sector’s attention to the built-environment’s impact on the health of its inhabitants. “This pandemic has rearranged our priorities,” she pointed out.
Such a shift in mindset, she said, is vital, because despite the fact that buildings have evolved to become much more sophisticated over the centuries, there has been a rise in infectious diseases. “Despite the increase in building hygiene, we have more infectious diseases, and there has been an increase in auto-immune disorders,” Dr Taylor said. “This bears taking a look at [the question], ‘Is there a relationship between how we manage our buildings – where we spend most of our time – and the increase in disease rate?’ We should ask if we are doing something that fosters an increase in diseases.”
In line with this, Dr Taylor presented three studies that explored the relationship between indoor air and environment and human infection rates. The first study, Dr Taylor discussed, was conducted in a new academic hospital in Chicago, in the United States. She explained that the study was spearheaded by a group of microbiologists that aimed to understand how microbial communities enter a brand new hospital and colonise the building. “Using very sophisticated generic analysis to understand the relationship between patient room parameters and communities of microbes, they were following the following parameters – temperature, hand hygiene, room pressurization, lux, CO2 level, absolute humidity, relative humidity, room traffic, room air changes and outdoor air ventilation,” she said.
The study led to approximately eight million data points over 13 months, Dr Taylor said, adding that for her part, she wanted to track patient infections. “Since we have electronic medical records, we can do that thoroughly,” she explained. “So, think about these parameters – were any of these related to new patient infections? We sent the data off, and our statisticians came back to say that the most powerful correlation with high infection rate was dry air in patient room.” According to the data, when the patient room’s relative humidity was at 40%, the infection rate came down, she said.
Still sceptical, Dr Taylor said she looked at another study, this time relating to nursing homes offering four years’ worth of data on the same parameters. “Once again, we found that when relative humidity is less than 40%, respiratory and gastrointestinal tract infections were especially high, and the infection rate came down at 40%-60% indoor relative humidity,” she said. This was confirmatory of the previous study, she emphasised.
The third study, Dr Taylor highlighted, was related to a pre- school in northern Minnesota, in the United States, conducted during wintertime. “They took half the school and humidified
at 45%, and the other half they did what they do in winter and humidified it at 20%,” she said. The study looked at how active Influenza A were and found that the humidified part of the school saw a third of the number of absentees compared to the non-humidified part. “This is a great study, and it moves beyond correlation to causation,” she pointed out.
For Dr Taylor, the global pandemic should trigger individuals in the building sector to look at their scope of responsibility, urging engineers to reflect on how the sector can diminish viral transmission through the building. “We need to manage our buildings as if it’s a significant route of transmission,” she said. “Multiple studies have shown that when relative humidity indoors is less than 40%, we have greater, longer aerosol transmission, it’s harder to effectively clean surfaces because of resettling, and for reasons we don’t fully understand, there is increased survival and virulence of many viruses and bacteria – and it happens to be true for this SARS-CoV-2 virus.”
She added that while energy efficiency is important, COVID- 19 has trained the spotlight on another reason we have buildings, which is to optimise our health. “I believe we could be comfortable and develop technology to safely humidify or dehumidify, in some cases, so we can begin to turn around this alarming trend,” she said. “Using health as a lens to understand IAQ, we have learned that RH 40-60% is essential. Low relative humidity is harmful to people and benefits pathogens (bad microbes). We must design and operate buildings to support health, and the first step is proper indoor humidification.” She added that a benefit of the finding is that addressing humidity is also easily implementable and can work well in tandem with other indoor air strategy improvements, with the benefit of being effective and immediate.
(Part 2 of the report will appear in the August 2020 issue of Climate Control Middle East.)
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