Health

Can a prescription for nature help cure the loneliness epidemic?

Lisa Marshall — Tue, 13 Oct 2026 17:54:32 +0000

Can a prescription for nature help cure the loneliness epidemic? Lisa Marshall Tue, 10/13/2026 - 11:54

Participants in the Friends in Nature program walk arm in arm on a hiking path in Barcelona. As rates of loneliness rise globally, some clinicians are prescribing time in nature as an antidote to the loneliness epidemic. Credit: The RECETAS project.

Lisa Marshall

��ñ�� one in three Americans and one in six people worldwide feel lonely on a regular basis, a troubling reality that has prompted some public health officials to declare an “epidemic of loneliness.”

A new global study presents a novel remedy. It found that nature-based social prescribing—clinicians literally prescribing things like gardening, hiking or birdwatching—can significantly reduce loneliness. Spending time in nature with others works even better, particularly for the loneliest among us, the study found.

The findings appear in the October issue of the journal Lancet Regional Health.

“There has been a lot of passion about nature-based prescriptions, but not a lot of evidence,” said corresponding author Jill Litt, professor of environmental health at ��ñ�� and principal investigator for the RECETAS project, which studied a social prescribing model called Friends in Nature in 1,200 adults in six cities across Europe, Latin America and Australia. “We now have randomized controlled trials showing this works and the impacts last.”

What is loneliness?

As Litt explains, loneliness is not about being physically isolated. Rather, it is a “subjective disconnect between one’s expectations of their social relationships and one’s reality.”

“I’ve heard people describe it like a knot in their stomach, like something is just not right,” said Litt. “You could be in a room full of people and still feel lonely.”

Studies show that chronic loneliness can increase risk of cardiovascular disease, dementia, stroke, depression and anxiety. It can also burden the healthcare system financially, as people suffering from loneliness tend to visit their doctor more (sometimes in search of human connection) and are more likely to visit the emergency department with vague complaints on Friday afternoons — a phenomenon known as “Friday afternoon syndrome.”

Professor Jill Litt at Horesbarn Garden in Denver. Credit: Louissé Studio

Participants in the Friends in Nature program enjoy a bird watching outing. Credit: Irene Cervera Buisán/The RECETAS Project.

Due to stigma, people are often reluctant to admit or don’t recognize they are lonely and assume the physical symptoms they feel are due to something else.

“Once clinicians really start to drill down to the root causes, they discover that loneliness is a big factor and the solutions may lie outside the traditional medical system,” said Litt, who is also a researcher with the Barcelona Institute for Global Health.

Nature as medicine

RECETAS (Re-imagining Environments for Connection and Engagement) was launched in 2021 with a $5.6 million grant from the European Union. It has since conducted randomized controlled trials in Barcelona, Spain; Prague, Czech Republic; and Helsinki, Finland; and quasi-experimental studies in Marseille, France; Cuenca, Ecuador; and Melbourne, Australia.

Thus far, all the studies have yielded promising results. The newest, published this month, center around the site in Barcelona, where loneliness rates have doubled in recent years as multi-generational living has become less common and families have spread apart.

The study included 320 lonely older adults from 12 low-income neighborhoods.

Half were placed in a group of 8–10, which spent two hours weekly for nine weeks together doing things like gardening, birdwatching or nature-based art programs along with two trained facilitators. The group activities were chosen from a menu co-created by the local community. The other half were provided the same menu of free, easily accessible nature-based activities that they could do on their own.

Both strategies worked. Participants on average showed an 11% reduction in loneliness scores at three months; 12% at six months; and 17% at one year. For those who started with lower emotional wellbeing, the group intervention worked significantly better.

“Not only did it work, but the effects were sustained,” said Litt, noting that many participants still meet today for outdoor activities.

Why nature works

Litt said that nature, with its vivid sounds, smells and sights, can act as an “additional facilitator,” augmenting therapeutic benefits and creating a safe space to support the formation of social bonds. Some participants told her, “nature doesn’t judge you” and “it’s hard to be angry in nature.”

"In the outings we have done I have learned to contemplate everything more, to be with the sounds, to focus," reported one 63-year-old female participant. "I have met people. I have shared. It has been wonderful."

But how could being in nature alone alleviate loneliness?

In addition to the documented benefits of relieving stress and mental fatigue and promoting motivation, it can also create new memories.

“Being out in nature forms this kind of reservoir of calm that we can return to later in life during stressful times,” said Louise Chawla, an environmental psychologist and professor emerita at ��ñ��. “It’s not just restorative when you are in a place but also when you go back to it in memory.”

Chawla recently co-authored another paper with Litt, calling for more attention to the role that nature can play in fostering social connections.

She notes that with a shortage of mental health workers, the model of an individual sitting down with one therapist in an office is no longer realistic or affordable for many.

“We need to think in broader terms about how we can create group healing activities in places like parks and community gardens,” Chawla said.

Public health agencies in Spain have already begun to recognize the Friends in Nature model as a best-practice for addressing the loneliness epidemic.

Litt is now working to bring similar trials to the U.S. in hopes that someday, insurance might cover things like a membership in a community garden or birdwatching club.

“We have nature in our cities and investment in our green infrastructure,” she said. “Now we need a mechanism to bridge these resources with our health systems to offer person-centered care that leverages the power of nature for healing and wellbeing.”

A global study of hundreds of lonely adults finds that when healthcare providers prescribe time in nature, there are powerful and lasting impacts. Sharing time in nature with others works even better.

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Breast cancer awareness starts with better communication

Chloe Fischer — Wed, 07 Oct 2026 18:51:17 +0000

Breast cancer awareness starts with better communication Chloe Fischer Wed, 10/07/2026 - 12:51

When breast cancer patients and surgeons weigh treatment options, how—and when—information is shared matters. New research explores how better communication can help balance patient choice with medical guidance.

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Short on time? It could be good for you

Lisa Marshall — Wed, 30 Sep 2026 14:36:22 +0000

Short on time? It could be good for you Lisa Marshall Wed, 09/30/2026 - 08:36

Lisa Marshall

When it comes to mental health, it may not be how much time you have that matters but rather how you feel about the time you have.

That’s one key takeaway of a new ��ñ�� study examining the relationship between time and mental health.

The study of 646 undergraduates, published in the Journal of American College Health, found that those with the busiest schedules were significantly less likely to be depressed, and—contrary to some common assumptions—they got better grades. Those who felt a chronic sense of rush or “time pressure” had higher rates of anxiety and depression, regardless of what their schedules looked like.

"The amount of time we have in our week isn’t super malleable. But the way we think about time is."
— Caitlin McKimmy

Additionally, those who scored higher on measures of mindfulness (the ability to be present and aware in the moment) appeared to be able to take on a heftier schedule without compromising their mental health.

“We have a tendency to think, ‘Oh, things will get better, and I won’t be stressed if I can just take some things off of my plate,’” said first author Caitlin McKimmy, a doctoral candidate in the Department of Psychology and Neuroscience and the Renee Crown Wellness Institute. “These data show that it’s not that simple—that outside of what is actually on our calendar we need to heal our relationship with time.”

Time pressure vs. time scarcity

Previous research shows that people can experience time differently, depending on what they’re doing with it.

One study found that people who give their time away, through things like volunteering or helping friends, tend to feel less stressed about time than those who spend time on themselves or waste time. Other research has shown that when someone is fully immersed in a task they care about, also known as a “flow state,” time seems to speed by.

Deep breathing and other mindfulness practices have been shown to increase one’s sense that their time is abundant.

For the new study, McKimmy, a busy mother of two, wanted to examine the impact of two distinct elements of time: “time pressure” (or the subjective sense of rush); and “time scarcity” (the objective lack of non-committed hours).

In her survey, she gathered data on how many hours per week the student participants spent in class, preparing for class, working a job, commuting and doing other activities. Survey questions also assessed how much time pressure they felt, how anxious or depressed they were and their level of mindfulness.

The participants agreed to provide their GPAs and access to their academic records.

McKimmy was surprised to find that time scarcity was strongly associated with both better grades and lower rates of depression. Heightened time pressure, on the other hand, was strongly associated with more anxiety, depression and lower grades.

Importantly, those short on time didn’t necessarily feel time pressure.

“You can have a very busy person who has a harmonious relationship with time and someone else who, objectively speaking, has a calendar with some space in it but is really stressed out about time,” McKimmy said.

When asked what they would do with it if they did have more time, students listed self-care, including mental healthcare, as No. 1.

Can mindfulness make busyness manageable?

McKimmy stresses that the findings don’t prove that staying busy causes people to be happier. It could be that those with better mental health naturally seek out more experiences while those struggling with low mood say no more. There could also be shared underlying factors that influence both how someone perceives time and their mental health. For instance, some research suggests that depression itself can influence perception of time, potentially making it feel unmanageable.

What we can infer from these data, she said, is that the common less-is-more narrative may not always hold.

For instance, while a student might be inclined to skip taking a part-time job, for fear it might hurt their GPA, the study found no evidence that adding more to a schedule will hurt academic performance or mental health. While someone might retreat socially when their grades or work start to slip, this could potentially backfire, leading to a monotonous schedule—that can make time crawl by—and a sense of loneliness, warns McKimmy.

“These data support the idea that doing more and being engaged can not only lead to better mental health but could also support academic and professional success,” she said.

This is not to say that there’s no such thing as being overscheduled, she stressed. Often, for reasons they can’t control, people have less free time than is ideal.

Notably, the study showed that people who scored higher on measures of mindfulness had less negative mental health impacts when they were stressed about time.

“There appears to be something about attuning to the present moment that protects you against the negative impact of time pressure,” she said.

Her advice to those feeling stressed about their schedule: If you must fill it, try to fill it with things in line with your passions and values; try to be in the moment, not thinking about the future or past.

If you notice you are feeling stressed, take a moment to focus on your breath and ground yourself in your body and in the moment.

“The amount of time we have in our week isn’t super malleable,” she said. “But the way we think about time is.”

People with busy schedules are less likely to experience depression and more likely to get better grades, according to a new study of college students. Those who feel chronic pressure around their schedules don't fare so well.

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Breaking barriers to mental health care at community colleges

Chloe Fischer — Thu, 24 Sep 2026 20:18:42 +0000

Breaking barriers to mental health care at community colleges Chloe Fischer Thu, 09/24/2026 - 14:18

��ñ�� Assistant Professor Tamar Kodish is studying how targeted text messages could help connect community college students with mental health services when they need them.

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Sudden, unexpected deaths on rise among infants born to Black mothers

Lisa Marshall — Wed, 23 Sep 2026 22:48:11 +0000

Sudden, unexpected deaths on rise among infants born to Black mothers Lisa Marshall Wed, 09/23/2026 - 16:48

Lisa Marshall

After years of declines in sudden unexpected infant deaths (SUID), rates have been ticking up again, particularly among babies born to Black mothers, new research shows.

The findings, published Sept. 22 in the journal JAMA Network Open, help explain a puzzling widening of the disparity in infant mortality rates between white and Black populations since 2020.

“This study provides evidence that there is an acute crisis right now in sudden unexplained infant death, a category of cause of death that we assumed we got under control a long time ago,” said co-author Leslie Root, a demographer and assistant research professor in the Institute of Behavioral Science at ��ñ��.

Mortality rates for babies born to Black mothers are about twice that of babies born to white mothers, a gap that has persisted for decades. Experts point to higher rates of preterm birth among Black women as the primary cause of the gap, and public health campaigns centering around prenatal care and education have worked to address the issue.

But since 2020, the gap has begun to widen again.

To explore why, Root and her co-authors analyzed federal data on nearly 58 million live births from Jan. 1, 2003, to Dec. 31, 2024. The data set included linked birth-and-death certificates for 366,384 infant deaths among non-Hispanic Black mothers and 224,733 non-Hispanic white mothers.

The researchers grouped infants’ gestational age into seven categories, from extremely preterm (28 weeks) to post-term (42 weeks) to compare mortality rates among white and Black infants born at each gestational age. They also divided deaths into 13 categories.

They found that while differences in gestational age at birth still account for the bulk of the infant mortality gap, other factors are playing an increasing role.

SUID—which includes sudden infant death syndrome (SIDS), accidental suffocation in bed and other unexplained causes, now accounts for more than a third of the disparity, making it the largest single cause-of-death contributor.

“This finding suggests that even if preterm birth disparities were eliminated entirely, a large mortality gap would remain, and sudden unexpected infant death is what is driving the increase,” said Root.

Root said it’s not clear why rates of SUID are rising among infants born to Black mothers while staying relatively flat among whites. But she points out that the increase coincided with the COVID-19 pandemic.

Some recent studies have suggested that off-season resurgences in respiratory infections, including COVID, RSV and influenza, could be making infants more vulnerable to sudden infant death syndrome and other forms of SUID. Lingering social and economic consequences associated with the pandemic may have also exacerbated health disparities, widening the infant mortality gap.

Root notes that the shift also coincided with an increase in opioid deaths and overdoses among Black Americans, surpassing, for the first time, the rate among white Americans.

In future studies, the team would like to study whether parental opioid use, which can increase risk of SUID, could be a factor. They also want to look at the data around Native American and Alaska Native populations, which were not included in this study.

An estimated 3,400 infants die unexpectedly in the US each year, making SUID a leading cause of death in infants.

Root hopes the findings will prompt more attention to the issue and heighten efforts to prevent it.

“We have come a long way since a few decades ago,” she said, pointing to campaigns urging parents that “back is best” for a baby’s sleep position and heightening awareness of safe crib standards. “That’s why this uptick, and the fact that there is a racial disparity component, is so alarming. We need to address it.”

A new analysis of 22 years of U.S. mortality data highlights a troubling trend.

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Why some stroke patients fare better than others

Lisa Marshall — Wed, 02 Sep 2026 17:33:58 +0000

Why some stroke patients fare better than others Lisa Marshall Wed, 09/02/2026 - 11:33

Lisa Marshall

A clot forms. Blood flow to the brain is blocked. Starved of oxygen, neurons begin to die.

This scenario, known as an ischemic stroke, plays out in roughly 21,000 people worldwide each day, threatening long-term disability or even death. In recent years, clot-busting drugs and mechanical tools for removing them have revolutionized care.

Yet, even with the clot gone and the vessel clear, up to 50% of patients never recover neurologically. New research from ��ñ�� and the University of Antwerp helps explain why.

The study, published in the journal PNAS, reveals in unprecedented detail how the brain’s own defense mechanisms against stroke can backfire, triggering additional micro-clots in minor vessels which can damage tissue long after the primary culprit is gone.

“We now have a way to explain why so many of these patients are not seeing neurological improvements,” said co-author Debanjan Mukherjee, an assistant professor of mechanical engineering at ��ñ��. “Our findings also point to a new potential target for therapeutics that could be extremely impactful for stroke patients.”

The mystery behind ‘no reflow’

Doctors have long known that removing a stroke-causing clot cannot always restore full blood flow to the brain. But why this phenomenon, known as “no reflow,” occurs has remained a mystery.

To unravel it, Mukherjee, who studies the physics of blood flow, teamed up with senior author Frederik Denorme, an assistant professor of biology at the University of Antwerp who studies, as he puts it, “life after the clot.”

“The dogma used to be that you just need to get rid of that blood clot and then all problems should be solved,” said Denorme. “We now know that is not the case.”

In fact, only about 1 in 10 surviving stroke patients recover completely after a stroke; 25% have minor impairments; and half have moderate to severe impairments.

To examine what, precisely, goes on in the brain after a clot is removed, the research team first turned to mice.

Using a technique called intravital microscopy, they observed in real time how blood flowed in the brain, and cells behaved, in the hour after mice suffering from stroke underwent endovascular thrombectomy. The procedure involves threading a tool through a blood vessel to pluck out an obstructive clot.

While blood quickly started flowing again post-procedure, the researchers were stunned to see that in many mice, it flowed haphazardly, in fits and starts, even reversing course at certain points.

“We saw it with our own eyes. Blood that was flowing left all of a sudden flowed right and vice versa,” said Denorme. “It was remarkable.”

A Jekyll and Hyde protein

Debanjan Mukherjee and his students work with a blood vessel simulation in the FLOWLab at the ��ñ��. Credit: Patrick Campbell

An even closer look revealed that, as the brain tried to divert blood around the original obstruction, tiny clots formed where the haphazard channels converged.

To drill down on why those clots formed, Mukherjee’s FLOWLab recreated this scenario using computer simulations. In other research, his lab has recreated similar scenarios using a 3D artificial brain filled with fake blood.

These experiments implicated von Willebrand factor—a protein best known for stopping bleeding when we get a cut.

In its resting state, Mukherjee explained, von Willebrand factor is coiled up like a ball of string inside blood vessels, waiting for distress signals from the body that make it stretch out and start forming clots to stop bleeding.

In a brain experiencing a stroke, something else unfolds the ball.

“If there is some kind of fluid motion induced after the clot is removed, it can stretch out that ball into an extended thread that attracts platelets, forms new clots and blocks flow even after the original culprit clot is gone,” Mukherjee said.

Meanwhile, the study showed, the brain's inflammatory response to stress interferes with safeguards that normally keep the protein’s clotting efforts in check, creating what the authors call “a perfect storm” of collateral damage.

Other experiments, looking at blood from stroke patients at the University of Washington in St. Louis, suggest a similar phenomenon happens in humans too.

“We are the first to really show in this hyperacute phase of stroke what is happening with these cells inside blood vessels,” said Denorme.

More research is necessary to determine why no reflow happens in some stroke patients but not others. But the study did find that stroke patients with higher blood levels of a pro-inflammatory compound called Interleukin 6 had more overactive von Willebrand factor and fared worse long-term.

The researchers envision a day when therapeutics targeting von Willebrand factor, or the inflammatory compounds that exacerbate its clotting capabilities, could be given to stroke patients alongside clot-busting drugs and surgery.

Notably, several such drugs already exist and are approved for use for other disorders.

“It’s early days. But now that we have a lead on what drives these micro-clots, we have a promising new avenue to explore for improving recovery,” said Denorme.

As it tries to defend itself from stroke, the brain can paradoxically trigger tiny new clots in minor blood vessels, damaging tissue even after the original culprit has been removed. The findings help explain why nearly half of treated stroke patients don’t recover—and identify potential new treatments.

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Blood vessels in the brain, captured by MRI. Credit: Adobe Stock Photos

Why permanent standard time is the healthiest choice

Yvaine Ye — Wed, 12 Aug 2026 19:12:39 +0000

Why permanent standard time is the healthiest choice Yvaine Ye Wed, 08/12/2026 - 13:12

Lisa Marshall

Spring forward. Fall back.

For 60 years, most of the U.S. has engaged in this biannual clock-changing ritual, much to the chagrin of critics who have argued that it’s confusing, outdated and dangerous.

The Sunshine Protection Act, passed by the U.S. House of Representatives in July, would end this practice, enabling states to stick with daylight saving time (DST) year-round.

Another recently introduced proposal, the Sunshine for our Kids Act, calls for the opposite: making standard time—which currently goes from November to March—the permanent national default. This proposal would still allow states to pass laws opting into permanent daylight saving time (pDST).

Under permanent standard time (pST), our winters would stay the same. But in the summer, the sun would rise and set earlier. For instance, in Denver, sunrise in June would occur as early as 4:31 a.m. and set as early 7:23 p.m.

Which is better? Or should we just keep switching our clocks?

Ken Wright

“If we take a pure health, safety and well-being perspective, especially for our children, the clear choice based on all the available evidence is permanent standard time,” said Ken Wright, an integrative physiology professor of distinction and director of the Sleep and Chronobiology Lab at ��ñ��. “Permanent daylight saving time, which is being considered the most right now, is the worst choice.”

We spoke with Wright about the potential health impacts of making DST permanent and why other options may be healthier.

When was daylight saving time invented?

It was first introduced on a large scale by the Germans during World War I. The idea was that extending evening sunlight would mean people wouldn’t use as much energy and that savings could be used to support the war effort. Several countries, including the U.S., followed suit temporarily during World Wars I and II. It wasn’t until 1966 that uniform start and stop dates for daylight saving time were established nationwide.

Have we tried to make DST year-round before?

Yes. During the oil crisis in 1974, but it was a very short-lived experiment. As soon as we hit the winter months, the public said, "No, we don't like these dark winter mornings," so Congress repealed it.

Why is permanent standard time your first choice?

Standard time is more closely aligned with the natural patterns in the environment under which we, as humans, have evolved. For instance, under standard time, we get lots of morning light, and the sun is high in the sky above us around noon. Under daylight saving time, there’s less morning light and the sun is high in the sky when the clock says 1 p.m.—after midday. We basically have a mismatch between the clock on the wall and the natural environment.

Why is morning light so important?

Light synchronizes our circadian rhythms (biological clocks that control an array of bodily processes) and our sleep timing to the 24-hour day. Morning light sets our circadian rhythm early, activates our brain, alerts us that it’s time to be awake and makes our mood better. But if we get that light at night it can shut down our melatonin (a hormone that signals us to sleep) and keep us awake.

What concerns you about permanent DST?

It would lead to darker mornings and brighter evenings, and this pushes our sleep times and our circadian rhythms later. We know that the later our sleep and circadian rhythms are, the less we sleep, the less healthy we are.

For instance, insufficient sleep and waking up and going to sleep later increases our risk for obesity, heart disease, mental health disorders and substance use disorders. For children, if their internal clock is set later, it makes it more difficult for them to learn in school. The same goes for people’s performance at work, especially in the morning.

What would permanent DST look like in Colorado?

This change would cause Colorado to lose 2.4 months of having sunlight in the morning before 8 a.m. and four months of having sunlight in the morning before 7:30 a.m., compared to a permanent standard time system.

The sun would rise late—after 7:30 a.m.—on 38% of school days, under permanent daylight saving time. Under permanent standard time, there would be no school days with a sunrise after 7:30 a.m. Under the current bi-annual change, Colorado has only four days with a sunrise after 7:30 a.m., so permanent daylight saving time is really a drastic change that will have consequences.

What concerns you about those dark mornings?

A lot of our children are going to be waiting for the school bus or walking to school in the dark. A lot of people are going to be driving to work or the ski slopes in the dark. These conditions could increase accidents.

Also, many places have adopted late school start times because they recognize the benefits to our children—it allows them to be more in sync with the sunrise and shift their circadian rhythm and sleep timing earlier. There’s less absenteeism, better grades and students are falling asleep less in class. With permanent daylight saving time, we would lose all those benefits.

Why not just stick with the time change twice a year?

There is no question the change itself is associated with problems. In the days after the "spring ahead," we get less sleep and wake up at a time when our brains are telling us we should still be sleeping. There are lots of associated risks, including an increase in fatal motor vehicle accidents and in heart attacks and strokes.

That said, there are strategies that we could think about to reduce the negative impacts of the time change. Instead of having the change occur in the early morning hours on Sunday, what if we shifted it to Saturday morning so most people would have an extra day to adjust?

What's your takeaway for lawmakers?

If you look across the board, not only at societies that focus on sleep, but also on health in general, it's nearly unanimous. Everyone says that permanent standard time, if we're going to make a change, is going to be the healthier, safer choice. Arizona and Hawaii have used permanent standard time since the 1960s, as federal law currently allows states the freedom to choose permanent standard time. We all should follow suit.

��ñ�� Today regularly publishes Q&As on news topics through the lens of scholarly expertise and research/creative work. The responses here reflect the knowledge and interpretations of the expert and should not be considered the university position on the issue. All publication content is subject to edits for clarity, brevity and university style guidelines.

Congress is considering dueling proposals this summer. One would make daylight saving time permanent; another would make standard time permanent. Which is better? Or should we just keep changing our clocks? A sleep expert weighs in.

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How gut bacteria offer clues about the cost of industrialization

Megan M Rogers — Thu, 06 Aug 2026 16:08:43 +0000

How gut bacteria offer clues about the cost of industrialization Megan M Rogers Thu, 08/06/2026 - 10:08

��ñ�� scientist Matthew Olm and colleagues have mapped the gut microbiome's hidden global diversity, offering new insight into how industrialization has reshaped the microbes that support human health.

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From napkin sketch to operating room: Designing a safer hip surgery tool

Megan M Rogers — Tue, 21 Jul 2026 14:55:40 +0000

From napkin sketch to operating room: Designing a safer hip surgery tool Megan M Rogers Tue, 07/21/2026 - 08:55

A collaboration between ��ñ�� and CU Anschutz researchers led to the CAP-LIFT cannula, a redesigned surgical instrument that is making arthroscopic hip procedures safer and more efficient.

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Is wildfire smoke bad for your health?

Lisa Marshall — Tue, 30 Jun 2026 17:02:41 +0000

Is wildfire smoke bad for your health? Lisa Marshall Tue, 06/30/2026 - 11:02

Lisa Marshall

Editor's note: This article was originally published July 12, 2021, and updated June 30, 2026.

Coloradans awoke to hazy skies this week, as smoke from multiple large fires burning across the West deemed air quality “poor” and “unhealthy for sensitive groups” in some regions, according to federal data.

Not long ago, researchers had little understanding of how such smoke impacts human health—if at all, says Colleen Reid, an assistant professor of geography who, in 2008, became one of the first researchers in the country to start studying it.

“At the time, there was a sense that it was ‘natural’ air pollution, and that it was only short-term so it was not as much of a concern as pollution from things like factories, refineries and vehicles,” she said. “What we are realizing now, as these episodes of exposure become more frequent and last longer, is that wildfire smoke can have measurable and potentially lasting health impacts.“

Reid spoke with ��ñ�� Today about what those impacts are and how we can minimize them.

It seems like smoke is getting worse each summer. Is it?

It is. When I started this work, people collecting data from monitors in Northern California said "disregard anything above 400 micrograms per cubic meter (ug/m3)" because they assumed it was impossible. They thought the monitors were malfunctioning. Now, in some areas of the country, levels have reached the thousands during extreme wildfire smoke events near the fire.

There is now evidence that wildfire smoke is offsetting the gains in air quality that have been achieved by regulating industrial and vehicular emissions under the Clean Air Act.

What is wildfire smoke made of?

It’s a complex mix of gases and solid and liquid particles. From a health perspective, the particles—that dark cloud that you see when you look at the smoke plume—are most concerning. They are so tiny that, unlike larger particles, they don’t get stopped in the trachea or nose when you breathe them in.

When assessing air quality, we tend to focus on PM2.5, particulate matter that is 2.5 microns or smaller in diameter. The smaller the particle, the deeper they get into the lungs, and the more likely they are to get into the bloodstream.

Most particles created during wildfires are 1 micron or smaller, not only affecting respiratory health but potentially having systemic effects—including inflammatory effects. They have found particles in the brains of cadavers, so we also know they can get into the brain.

Is there anything else in there of concern?

Some researchers have also become concerned about hazardous air pollutants such as formaldehyde, benzene and hydrogen cyanide present in wildfire smoke. We also have found these contaminants in ash after wildfires that burn structures, such as the Marshall Fire and the L.A. fires. Ground-level ozone is also a concern, as it is a respiratory irritant and can be formed through chemical reactions of other air pollutants in wildfire smoke.

Is wildfire smoke worse for you than other forms of air pollution?

The case is not yet settled on this.

Some epidemiological studies suggest that PM2.5 found in wildfire smoke is more harmful than other sources of PM2.5, but these findings do not take into account differences in what burned (forest, grassland or human-made materials) or the fact that wildfire smoke is very bad for short periods, whereas other sources of PM2.5 contribute lower levels but regularly throughout the year.

At least one study in mice found that particles in wildfire smoke are more toxic than particles from other sources.

How does wildfire smoke impact short-term health?

Probably everyone exposed to wildfire smoke is impacted in some way, even if they don’t recognize it. They might be a little short of breath or have some heart rate variability or lung function decline. We know that it can cause a sore throat, cough, itchy/watery eyes, congestion and shortness of breath. If you can’t breathe as deeply and get as much oxygen, especially at this altitude, you might feel tired.

For people with pre-existing respiratory disease (such as asthma or emphysema), wildfire smoke can lead to increased need to use medication and, in some cases, needing emergency care. Generally, there are more people who die during wildfire events than would be expected if the wildfire was not there—these are probably individuals who were very sick and the air pollution from the wildfire smoke was the proverbial straw that broke the camel’s back.

Are there longer-term effects?

My own research found that babies whose gestation is during a wildfire event are more likely to be born with a lower birth weight and more likely to be born early. There is also some evidence that wildfire smoke can trigger heart attacks and impact the immune system.

One recent study looking at eight years of data in Montana found that areas with more intense wildfire smoke exposure in the summer had worse flu seasons the following winter. It could be that wildfire smoke irritates the lungs and makes people more susceptible to worse infection upon exposure. Some evidence suggests that areas with worse wildfire smoke may experience more COVID-19 cases or more severe cases of the disease.

Researchers are also studying whether wildfire smoke is affecting metabolic health and cognition.

What should people do on smoky days?

Make sure that your medication is up to date and that you have enough of it.

Use indoor air cleaners and make sure to check the filter on portable air cleaners and on your HVAC system. After just one bad wildfire smoke episode, the filter can be filled with particulates and needs to be changed. Get the highest MERV (minimum efficiency reporting value) rating on your HVAC filter that your system can handle.

On very smoky days, people with pre-existing conditions or those who are more sensitive should wear an N95, KN95 or KF94 mask (good for smaller sizes or children) that fits them well.

What if the fire is really far away? Should I worry?

A study from researchers at Colorado State University found there were more asthma hospitalizations along the Front Range when there was wildfire smoke in the area from the Pacific Northwest than when there was smoke from a local fire.

The difference is likely due to people being more likely to protect themselves when fires are close than when there is only smoke. That means people should take precautions when there is smoke in the area, regardless of how close the fire is.

Should I exercise outdoors when it’s smoky?

That is a challenging question. We know from studies of cyclists that when the air pollution levels are not too high, the benefits of exercise outweigh the risk of air pollution exposure. But when the air quality gets really bad, it is challenging.

I recommend following the guidelines of the air quality index (AQI):

For the average person—curb outdoor exercise when levels exceed an AQI level of 150 or PM2.5 concentrations of 55 micrograms per meter cubed.
For those with pre-existing respiratory or cardiovascular disease—the recommended levels are lower, 100 on the AQI or 35 micrograms per meter cubed PM2.5 concentration.

If you can’t see to the end of your street, that might be a time to curb your outdoor exercise.

Can the smoke get inside?

From research I have done looking at indoor and outdoor PM2.5 in normal times and during wildfire smoke episodes, we see that PM2.5 can infiltrate indoor environments—but this happens less so in newer constructions (which are less leaky or tighter) and those with central HVAC systems. Indoor spaces do protect people from outdoor smoke.

But even with a really tight home, if the air pollution is bad for many days at a time, the smoke will get in. HEPA filters can help a lot. When it is really smoky, try to keep your windows and doors closed. But you also don’t want the indoor temperature to get so high that it is a health threat.

With heat and wildfires happening at the same time, that gets really challenging, especially for people who don’t have air conditioning. Some cities are looking into creating public clean-air shelters with air conditioning and HEPA filters.

With fires blazing across Colorado and surrounding states, many communities are inundated with smoke this week. How does it impact our health? Is it OK to exercise outside? How can we protect ourselves? Wildfire smoke researcher Colleen Reid has answers.

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