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Science

MIT Finds Indoor Humidity “Sweet Spot” To Reduce Spread of COVID-19

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An MIT study shows that keeping indoor humidity at a sweet spot may reduce the spread of COVID-19.

New research links very dry and very humid indoor environments with worse

Relative humidity is the amount of moisture in the air compared to the total moisture the air can hold at a given temperature before saturating and forming condensation.

In a study published in the Journal of the Royal Society Interface on November 16, the MIT team reports that maintaining an indoor relative humidity between 40 and 60 percent is associated with relatively lower rates of COVID-19 infections and deaths, while indoor conditions outside this range are associated with worse COVID-19 outcomes. To put this into perspective, most people are comfortable between 30 and 50 percent relative humidity, and an airplane cabin is at around 20 percent relative humidity.

The findings are based on the team’s analysis of COVID-19 data combined with meteorological measurements from 121 countries, from January 2020 through August 2020. Their study suggests a strong connection between regional outbreaks and indoor relative humidity.

In general, the researchers found that whenever a region experienced a rise in COVID-19 cases and deaths prevaccination, the estimated indoor relative humidity in that region, on average, was either lower than 40 percent or higher than 60 percent regardless of season. Nearly all regions in the study experienced fewer COVID-19 cases and deaths during periods when estimated indoor relative humidity was within a “sweet spot” between 40 and 60 percent.

“There’s potentially a protective effect of this intermediate indoor relative humidity,” suggests lead author Connor Verheyen, a PhD student in medical engineering and medical physics in the Harvard-MIT Program in Health Sciences and Technology.

“Indoor ventilation is still critical,” says co-author Lydia Bourouiba, director of the MIT Fluid Dynamics of Disease Transmission Laboratory and associate professor in the departments of Civil and Environmental Engineering and Mechanical Engineering, and at the Institute for Medical Engineering and Science at MIT. “However, we find that maintaining an indoor relative humidity in that sweet spot — of 40 to 60 percent — is associated with reduced COVID-19 cases and deaths.”

Seasonal swing?

Since the start of the COVID-19 pandemic, scientists have considered the possibility that the virus’ virulence swings with the seasons. Infections and associated deaths appear to rise in winter and ebb in summer. But studies looking to link the virus’ patterns to seasonal outdoor conditions have yielded mixed results.

Verheyen and Bourouiba examined whether COVID-19 is influenced instead by indoor — rather than outdoor — conditions, and, specifically, relative humidity. After all, they note that most societies spend more than 90 percent of their time indoors, where the majority of viral transmission has been shown to occur. What’s more, indoor conditions can be quite different from outdoor conditions as a result of climate control systems, such as heaters that significantly dry out indoor air.

Could indoor relative humidity have affected the spread and severity of COVID-19 around the world? And could it help explain the differences in health outcomes from region to region?

Tracking humidity

For answers, the team focused on the early period of the pandemic when vaccines were not yet available, reasoning that vaccinated populations would obscure the influence of any other factor such as indoor humidity. They gathered global COVID-19 data, including case counts and reported deaths, from January 2020 to August 2020,  and identified countries with at least 50 deaths, indicating at least one outbreak had occurred in those countries.

In all, they focused on 121 countries where COVID-19 outbreaks occurred. For each country, they also tracked the local COVID-19 related policies, such as isolation, quarantine, and testing measures, and their statistical association with COVID-19 outcomes.

For each day that COVID-19 data was available, they used meteorological data to calculate a country’s outdoor relative humidity. They then estimated the average indoor relative humidity, based on outdoor relative humidity and guidelines on temperature ranges for human comfort. For instance, guidelines report that humans are comfortable between 66 to 77 degrees

“We saw more reported COVID-19 deaths on the low and high end of indoor relative humidity, and less in this sweet spot of 40 to 60 percent,” Verheyen says. “This intermediate relative humidity window is associated with a better outcome, meaning fewer deaths and a deceleration of the pandemic.”

“We were very skeptical initially, especially as the COVID-19 data can be noisy and inconsistent,” Bourouiba says. “We thus were very thorough trying to poke holes in our own analysis, using a range of approaches to test the limits and robustness of the findings, including taking into account factors such as government intervention. Despite all our best efforts, we found that even when considering countries with very strong versus very weak COVID-19 mitigation policies, or wildly different outdoor conditions, indoor — rather than outdoor — relative humidity maintains an underlying strong and robust link with COVID-19 outcomes.”

It’s still unclear how indoor relative humidity affects COVID-19 outcomes. The team’s follow-up studies suggest that pathogens may survive longer in respiratory droplets in both very dry and very humid conditions.

“Our ongoing work shows that there are emerging hints of mechanistic links between these factors,” Bourouiba says. “For now, however, we can say that indoor relative humidity emerges in a robust manner as another mitigation lever that organizations and individuals can monitor, adjust, and maintain in the optimal 40 to 60 percent range, in addition to proper ventilation.”

Reference: “Associations between indoor relative humidity and global COVID-19 outcomes” by C. A. Verheyen and L. Bourouiba, 16 November 2022, Journal of The Royal Society Interface.
DOI: 10.1098/rsif.2021.0865

This research was made possible, in part, by an MIT Alumni Class fund, the Richard and Susan Smith Family Foundation, the National Institutes of Health, and the National Science Foundation.



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Health

Exposure to Sun, Heat and Humidity Can Exacerbate Symptoms of Mental Disorders

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Summary: Researchers report exposure to hot, humid weather can trigger mental health symptoms that require emergency care.

Source: University at Albany

Exposure to sunny, hot and humid weather can trigger severe symptoms of mental disorders, requiring emergency care. So reports a recent study, led by researchers at the University at Albany, which used data on New York State weather and hospital emergency visits to assess how features of summer weather affect people with mental disorders.

The research was the first to evaluate combined effects of multiple meteorological factors across all classes of mental disorders designated by the World Health Organization.

These findings, published in Environment International, could inform strategies to improve patient care.

Lead author Xinlei Deng, who completed his Ph.D. in May in the Department of Environmental Health Sciences at UAlbany, says, “We know that weather affects mood. But while a warm, bright day is a boost for some, others can become more easily agitated or quicker to anger. For people with mental disorders, changes in multiple weather factors can provoke symptoms that pose serious health risks.”

“By examining local weather conditions together with information on emergency department visits, we found clear trends connecting high heat, humidity and sun exposure with increased emergency admissions due to mental disorders, especially among patients suffering symptoms linked to psychoactive substance use, mood disorders, stress disorders and adult behavior disorders, which can include forms of violence like pyromania.

” Understanding these connections can help care providers shape interventions to protect patient well-being.”

The statewide analysis included two six-month study periods, focusing on the warmer months: May-October, in 2017 and 2018.

The team leveraged meteorological data from NYS Mesonet––a UAlbany-operated network of 126 weather stations in every county and borough in New York, which record atmospheric and soil conditions at 5-minute intervals. Their study looked at data on temperature, solar radiation, relative humidity, heat index and rainfall.

Emergency department visits due to mental disorders were identified using the International Classification of Diseases (ICD-10). Disorders are coded by subtype, which include categories like stress-related disorders, intellectual disabilities and intentional self-harm.

Over the study periods, 547,540 emergency department visits attributed to mental disorders were recorded in New York State. To link local weather conditions and emergency department visits, the residential address of each case was geocoded and paired with the nearest Mesonet station. Information on patient diagnoses and demographics was obtained from the New York Statewide Planning and Research Cooperative System, a mandatory hospital discharge database covering ~95% of hospitals in the state.

Results showed that the combination of high temperature, solar radiation and relative humidity posed the greatest risk of severe mental disorder symptoms. Effects were strongest in the summer transition months of September and October. Populations impacted most acutely included: males, Hispanic and African American individuals, people aged 46-65, Medicaid or Medicare subscribers, and people without insurance.

Several mental disorder classes were distinctly responsive to certain combinations of weather conditions. For example, hospitals saw increased emergency department visits due to psychoactive substance use (e.g., consuming alcohol or opioids) when solar radiation, temperature, heat index and humidity were high.

Severe symptoms of mood disorders, which include depression and bipolar disorders, coincided with less sun and high heat.

“As extreme heat becomes increasingly intense and more frequent due to climate change, we can expect these changes to have adverse physiological effects on people,” said Shao Lin, senior author of the study and a professor at UAlbany’s School of Public Health.

“Individuals with mental disorders are especially vulnerable to these changes, and our findings suggest that multiple, simultaneous weather stressors may compound health risk. Efforts to hone targeted care must take combined factors into account.”

Exposure to sunny, hot and humid weather can trigger severe symptoms of mental disorders, requiring emergency care. Image is in the public domain

Since mental health symptoms associated with weather can take time to manifest, the team measured “lag days” –– time between the onset of a particular weather condition and the date of hospital admittance –– to account for this delay. They found that high temperature alone presented the most immediate short-term risk, while heat index increased risk over a two-week period.

Deng, now doing postdoctoral work at the National Institutes of Health, explains, “As we learn more about the ways that weather affects mental health, putting a finer point on symptom emergence timing is critical.

Understanding lag effects could help hospital caregivers know when to prepare to receive a higher number of patients in the wake of prolonged weather conditions known to exacerbate certain mental disorders.”

Public health agencies like the CDC could use these findings to establish early-warning systems to preempt mental health-related violence and syndromes. Proactive measures could include facilitating access to cooling centers and encouraging patients with relevant mental disorders to pay attention to heatwaves and sun exposure, and take shelter as appropriate.

“Knowing that transition months see the highest risk of severe symptoms tells us that early warning systems and related education should start in May and continue through September-October,” Lin said. “Policymakers can plan preparedness efforts using health risk thresholds connected to weather factors.”

See also

“Weather and climate have profound impacts on health –– directly from severe and hazardous weather to more indirect impacts from allergens and mental health,” said Jerry Brotzge, a coauthor of the paper and the New York State Mesonet’s long-time program manager who was recently hired as state climatologist in his home state of Kentucky.

“Recent advances in weather observations collected at high temporal and spatial scales, like those recorded by Mesonet, have the potential to revolutionize our understanding of how changes in weather cause changes in health. Once we understand these relationships better, we can respond to patients’ needs more effectively.”

About this climate change and mental health research news

Author: Press Office
Source: University at Albany
Contact: Press Office – University at Albany
Image: The image is in the public domain

Original Research: Open access.
“Identifying joint impacts of sun radiation, temperature, humidity, and rain duration on triggering mental disorders using a high-resolution weather monitoring system” by Xinlei Deng et al. Environment International

Abstract

Identifying joint impacts of sun radiation, temperature, humidity, and rain duration on triggering mental disorders using a high-resolution weather monitoring system

Background

Mental disorders (MDs) are behavioral or mental patterns that cause significant distress or impairment of personal functioning. Previously, temperature has been linked to MDs, but most studies suffered from exposure misclassification due to limited monitoring sites. We aimed to assess whether multiple meteorological factors could jointly trigger MD-related emergency department (ED) visits in warm season, using a highly dense weather monitoring system.

Methods

We conducted a time-stratified, case-crossover study. MDs-related ED visits (primary diagnosis) from May-October 2017–2018 were obtained from New York State (NYS) discharge database. We obtained solar radiation (SR), relative humidity (RH), temperature, heat index (HI), and rainfall from Mesonet, a real-time monitoring system spaced about 17 miles (126 stations) across NYS. We used conditional logistic regression to assess the weather-MD associations.

Results

For each interquartile range (IQR) increase, both SR (excess risk (ER): 4.9%, 95% CI: 3.2–6.7%) and RH (ER: 4.0%, 95% CI: 2.6–5.4%) showed the largest risk for MD-related ED visits at lag 0–9 days. While temperature presented a short-term risk (highest ER at lag 0–2 days: 3.7%, 95% CI: 2.5–4.9%), HI increased risk over a two-week period (ER range: 3.7–4.5%), and rainfall hours showed an inverse association with MDs (ER: −0.5%, 95% CI: 0.9-(-0.1)%). Additionally, we observed stronger association of SR, RH, temperature, and HI in September and October. Combination of high SR, RH, and temperature displayed the largest increase in MDs (ER: 7.49%, 95% CI: 3.95–11.15%). The weather-MD association was stronger for psychoactive substance usage, mood disorders, adult behavior disorders, males, Hispanics, African Americans, individuals aged 46–65, or Medicare patients.

Conclusions

Hot and humid weather, especially the joint effect of high sun radiation, temperature and relative humidity showed the highest risk of MD diseases. We found stronger weather-MD associations in summer transitional months, males, and minority groups. These findings also need further confirmation.

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Health

You Don’t Have to Suffer From Winter Eyes

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Photo: Prostock-studio (Shutterstock)

In addition to our skin and our hair, winter also can take a toll on our eyes—and for many of the same reasons. When it’s cold outside, we want to spend more time inside, where it’s warm and dry. Unfortunately, these warm and dry conditions have a tendency to make our eyes feel dry and irritated.

But then, if we walk outdoors and it’s windy and/or cold out, our eyes can start to water—while somehow remaining dry. Really, it’s not ideal. Here’s what to know about winter dry eye, including symptoms to look for, and how to treat it.

What is winter dry eye?

“Dry eye” doesn’t only describe what you’re experiencing—it’s also the name of the condition. It’s possible to experience dry eye any time of year, as it’s the result of low tear production or quality, but according to Marissa K. Locy, O.D., a professor at the University of Alabama at Birmingham’s Department of Ophthalmology, it tends to get worse during the winter.

“On average, the humidity drops in the winter with the colder weather,” Locy explains. “In addition, most people turn on the heat in their homes or offices to combat the cold. So, what you end up having is lower humidity outside, and even lower humidity inside, making for warm, dry conditions where moisture can evaporate from the eye faster than normal.”

What are the symptoms of winter dry eye?

The symptoms of winter dry eye tend to occur in both eyes, and be worse for people who wear contact lenses. According to the Mayo Clinic, these symptoms can include:

  • A stinging, burning, gritty, or scratchy sensation in your eyes
  • Watery eyes
  • Eye redness
  • Stringy mucus in or around your eyes
  • Sensitivity to light
  • Blurred vision or eye fatigue

How to treat winter dry eye

The bad news is that there is no cure for dry eye. But the good news is that there are different ways to manage the condition, including:

But if you’ve already tried all of the above and continue to experience dry eye over extended periods of time, it’s time to see a doctor. They can assess the situation, and either recommend other treatment options, or refer you to a specialist.

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Entertainment

Jennifer Aniston wows in wavy-haired, makeup-free selfie: ‘Okay, Humidity’

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Jennifer Aniston is stunning her fans yet again.

The 52-year-old actress took to Instagram on Thursday and shared a pair of photos of herself fresh-faced and makeup-free.

Also noticeable in the photos was the “Morning Show” actress’s blonde hair, which was surprisingly wavy, considering she’s known for primarily wearing a rather straight ‘do.

“Okay, Humidity…” she captioned the post with a few dizzying emojis. “Let’s go…..”

JENNIFER ANISTON PASSED ON ‘SERENDIPITY’ TO AVOID BEING ROM-COM QUEEN

She also tagged her hair care line LolaVie.

Jennifer Aniston showed off her wavy hairdo on Instagram.
(Getty Images)

“Thank you for REAL pics,” a follower commented. “We’re the same age and I respect gracefully aging.”

“I love that look on you,” said another.

“Beautiful with or without makeup,” a third gushed.

JENNIFER ANISTON SAYS SHE’S ‘READY’ TO DATE, LOOKING FOR SOMEONE WITH ‘CONFIDENCE’ AND ‘HUMOR’

“Sexy bed hair though….” joked Ali Wentworth.

Aniston launched her first LolaVie product in September 2021: a 99% naturally-derived Glossing Detangler.

Jennifer Aniston is known for generally wearing her hair smooth and straight.
(Photo by Gregg DeGuire/Getty Images for Turner)

In an interview with People magazine at the time, the “Friends” alum described the product as “the Swiss Army Knife” of hair products, which she finds helpful because her hair seems to have “300 personalities.”

“There’s not one strand that’s doing the same thing. And it’s just always been a challenge for me, ever since I was a kid,” she recalled. “Well, actually, I feel like [this is] punishment, because I had this incredible head of hair that was long and straight and down to my waist. And I always wanted to cut it, but my mom never let me. She said, ‘When you’re 13, you can do whatever you want.’ And that was the biggest mistake I ever made because I cut it all off.” 

JENNIFER ANISTON REVEALS THE TEXT MESSAGES SHE RECEIVED FOLLOWING DAVID SCHWIMMER DATING RUMORS

The star joked: “I think I might’ve hit the Dorothy Hamill!”

Aniston launched a hair line, LolaVie, in September 2021.
(Photo by Jordan Strauss/Invision/AP)

Aniston’s hairstyles have long captivated audiences, with “The Rachel” becoming a popular style for women while the actress was appearing on “Friends.”

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Surprisingly, however, her hairdo has never been much of a focus for the star.

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“I just love a good blowout. Hairstyles have never been my thing,” she said. “I just want to feel good in my skin at the end of the day, no matter what I am wearing.”



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Science

It’s not the heat, it’s the humidity that grounded Boeing’s Starliner

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Enlarge / The Boeing Starliner spacecraft to be flown on Orbital Flight Test-2 is seen at NASA’s Kennedy Space Center in Florida on June 2, 2021.

NASA

NASA and Boeing officials said Tuesday that they have successfully removed two valves from the Starliner spacecraft and have shipped them to Marshall Space Flight Center in Alabama for further analysis.

The forensic examination—the two valves will be inspected with a variety of techniques, including a CT scan—is part of Boeing’s ongoing effort to diagnose the “stuck” valve issue that caused an abort of Starliner’s uncrewed test flight on August 3. With less than five hours remaining in the countdown to launch, during a routine procedure, 13 of the 24 valves that control the flow of dinitrogen tetroxide oxidizer through the service module of the spacecraft would not cycle between closed and open.

An initial diagnostic effort at the launch pad yielded no results, so the Atlas V rocket and spacecraft were rolled back to an integration facility. After more inspection and testing there, engineers decided to “de-stack” the spacecraft and return it to Boeing’s spacecraft processing building at Kennedy Space Center. This eventually led to further dissection of the vehicle and removal of several valves.

Corrosive humidity

Boeing’s chief engineer for space and launch, Michelle Parker, said during a news conference with reporters Tuesday that the company has a pretty solid hypothesis for what went wrong. At some point during the 46-day period when the vehicle was fueled—and when the valves were found to be stuck—humidity must have gotten into the spacecraft. This moisture combined with the oxidizer and created nitric acid, beginning the process of corrosion.

Parker said dew points at the launch site were high in August, and while the vehicle was designed to operate in Florida’s humidity, there is physical evidence that humidity is nonetheless the culprit. Boeing and NASA engineers now want to try to recreate the corrosive reaction in similar test conditions so that they can be confident of the root cause and any countermeasures they implement.

The company and NASA will press ahead with work in Florida, Alabama, and at Boeing’s test site in White Sands, New Mexico. All of this will take time, acknowledged Boeing’s program manager for commercial crew, John Vollmer. He said Boeing is now targeting the “first half” of 2022 for the uncrewed test flight of Starliner. (One source told Ars the “no earlier than” date is May 2022).

This mission is formally named Orbital Flight Test-2, or OFT-2. The company is flying OFT-2 at its own expense, $410 million, following an uncrewed Starliner mission in December 2019 that went awry due to software issues. The company’s technicians and engineers worked long and hard after the OFT-1 flight to fix the software, only to have these new hardware problems crop up during launch-day checks on the pad in early August.

NASA is hoping that Boeing can get Starliner up and flying so that it can have a second launch system, alongside SpaceX’s Crew Dragon vehicle, to get its astronauts to and from the International Space Station. Assuming that Boeing safely completes OFT-2, Vollmer said the company and NASA would like to have about six months to review data and prepare for a crewed test flight. That would put the earliest possible launch date for Starliner’s first mission carrying astronauts toward the end of 2022. More realistically, the mission may not fly until early 2023.

After this flight, NASA will certify that Starliner is ready for regular, operational astronaut flights.

Buying more Dragons

As part of its commercial crew program, NASA ordered six “post-certification” missions from SpaceX and Boeing. SpaceX successfully completed its demonstration crewed mission in 2020 and is set to launch its third certified crew mission, Crew-3, to the International Space Station on October 31. A fourth and fifth mission are scheduled to follow in 2022.

During Tuesday’s news conference, NASA’s commercial crew program manager, Steve Stich, said the agency is negotiating additional flights for SpaceX—and possibly Boeing. He said details about those contract extensions could be announced within the next few months. Given the issues discussed Tuesday, It now seems possible that SpaceX could complete its initial six-mission contract before Boeing flies its first certified mission. But Stich is confident that Boeing will get there.

“I have no reason to believe that Boeing won’t be successful in getting Starliner operational,” Stich said. “We’ll get this problem solved, and then we’ll have two space transportation systems like we want.”

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Science

We Just Found The Secret Weapon That Makes Cotton The Best For Reusable Face Masks

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While some still quibble over wearing masks a year into the pandemic, scientists have gotten on with working out exactly what strategy is best – and cotton face masks just received another tick of approval.

 

Various studies have tested different material combinations and health authorities such as the World Health Organization and the CDC recommend cloth masks for the general public, based on their conclusions. But some of these studies overlooked an important real-world factor – these face covering fabrics end up damp from our breath. 

Now, a team of researchers has tested mask materials under high humidity conditions that mimic the air expelled from our mouths.

“This new study shows that cotton fabrics actually perform better in masks than we thought,”  said material scientist Christopher Zangmeister from the US National Institute of Standards and Technology (NIST).

Zangmeister and colleagues tested nine different types of cotton and six types of synthetic fibers including polyester and rayon in 99 percent humidity (about how humid our breath is) and 55 percent humidity.

This resulted in a remarkably visible difference in the performance of cotton.

While synthetic fabrics, which also performed poorly compared to dry cotton, did not change performance under humid conditions, cotton fabrics increased their ability to capture particles by 33 percent. 

The researchers used variously sized particles of salt as a test substitute for virus-transporting droplet and aerosol particles,and these appeared to absorb some of the moisture trapped by the water-attracting cotton fibers. The particles swell in volume, which makes it harder for them to pass through the fabric uninhibited.

 

Synthetic fibers, however, repel water, thus not creating the humid environment within the mask itself for this inhibition to happen. There was also no change in medical masks – but they are designed to work at high levels in all conditions (equivalent levels to cotton).

The best-performing type of cotton was cotton flannel, according to the results.

Microscopic images of the materials reveal a stark difference in structure – an orderly weave pattern in synthetic polyester compared to the chaotic network of crisscrossing fibers that give flannel its soft-to-touch feel.

NIST researchers believe this mess of fibers is what increases the chance airborne particles passing through the mask will collide and stick to the fabric.

Cotton flannel (left), polyester (right). (E.P. Vicenzi/Smithsonian Museum/NIST)
However, all this doesn’t mean wet masks are better: If your mask gets wet, it should be replaced. The amount of liquid present in the masks in these humid conditions amounts only to a few drops, which doesn’t alter the material’s breathability – the team found air pressure on both sides of the fabric remained relatively similar.

This is great news from an environmental perspective too. With mounting waste from disposable surgical masks that shed microplastics, it’s comforting to know there’s a safe, reusable option.

Research suggests owning a bunch of reusable masks that can be machine-washed together is the most eco-friendly option to keep you and your loved ones safe.

 

While the team says more research is required to fully appreciate the interactions between masks, humidity, and aerosol particle transmission, their study has contributed to the first international standards for fabric masks meant to slow the spread of COVID-19, recently released by the standards-developing organization ASTM International.

“To understand how these materials perform in the real world we need to study them under realistic conditions,” Zangmeister concluded.

This research was published in ACS Applied Nano Materials.

 



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