Investigating the effects of trendy ice baths, scientists at the University of Ottawa have made an interesting discovery on the beneficial way they affect cell functions, and have published their findings in Advanced Biology.
A new study conducted at the Human and Environmental Physiology Research lab (HEPRU) at the University of Ottawa has unveiled significant findings on the effects of cold water acclimation on autophagic (the cells’ recycling system, which promotes cellular health) and apoptotic (the programmed cell death that gets rid of damaged cells) responses in young males. The research highlights the potential for cold exposure to enhance cellular resilience against stress.
The study, conducted by Kelli King, postdoctoral fellow, and Glen Kenny, Full Professor at uOttawa’s School of Human Kinetics and Director of HEPRU, involved ten healthy young males who underwent cold-water immersion at 14°C for one hour across seven consecutive days. Blood samples were collected to analyse the participants’ cellular responses before and after the acclimation period.
“Our findings indicate that repeated cold exposure significantly improves autophagic function, a critical cellular protective mechanism,” says Professor Kenny. “This enhancement allows cells to better manage stress and could have important implications for health and longevity.”
The research revealed that while autophagy was initially dysfunctional after high-intensity cold stress, consistent exposure over a week led to increased autophagic activity and decreased cellular damage signals.
“By the end of the acclimation, we noted a marked improvement in the participants’ cellular cold tolerance,” explains King, the study’s first author. “This suggests that cold acclimation may help the body effectively cope with extreme environmental conditions.”
The implications of this study extend beyond athletic performance. Cold water immersion has gained popularity for its potential health benefits, and this research provides some scientific backing for its efficacy. The findings suggest that proper autophagic activity could not only extend cellular longevity but also prevent the onset of various diseases.
As the use of cold exposure becomes increasingly mainstream, understanding its effects on cellular mechanisms is vital. Professor Kenny emphasises, “This work underscores the importance of acclimation protocols in enhancing human health, especially in contexts where individuals are exposed to extreme temperatures.”
“We were amazed to see how quickly the body adapted,” notes King. “Cold exposure might help prevent diseases and potentially even slow down aging at a cellular level. It’s like a tune-up for your body’s microscopic machinery.”
These results apply to young males and more research is needed to see if it would also apply to other cohorts.
Tiny fragments of plastic have become ubiquitous in our environment and our bodies. Higher exposure to these microplastics, which can be inadvertently consumed or inhaled, is associated with a heightened prevalence of chronic noncommunicable diseases, according to new research being presented at the American College of Cardiology’s Annual Scientific Session (ACC.25).
Researchers said the new findings add to a small but growing body of evidence that microplastic pollution represents an emerging health threat. In terms of its relationship with stroke risk, for example, microplastics concentration was comparable to factors such as minority race and lack of health insurance, according to the results.
“This study provides initial evidence that microplastics exposure has an impact on cardiovascular health, especially chronic, noncommunicable conditions like high blood pressure, diabetes and stroke,” said Sai Rahul Ponnana, MA, a research data scientist at Case Western Reserve School of Medicine in Ohio and the study’s lead author. “When we included 154 different socioeconomic and environmental features in our analysis, we didn’t expect microplastics to rank in the top 10 for predicting chronic noncommunicable disease prevalence.”
Microplastics—defined as fragments of plastic between 1 nanometre and 5 millimetres across—are released as larger pieces of plastic break down. They come from many different sources, such as food and beverage packaging, consumer products and building materials. People can be exposed to microplastics in the water they drink, the food they eat and the air they breathe.
The study examines associations between the concentration of microplastics in bodies of water and the prevalence of various health conditions in communities along the East, West and Gulf Coasts, as well as some lakeshores, in the United States between 2015-2019. While inland areas also contain microplastics pollution, researchers focused on lakes and coastlines because microplastics concentrations are better documented in these areas. They used a dataset covering 555 census tracts from the National Centers for Environmental Information that classified microplastics concentration in seafloor sediments as low (zero to 200 particles per square meter) to very high (over 40 000 particles per square metre).
The researchers assessed rates of high blood pressure, diabetes, stroke and cancer in the same census tracts in 2019 using data from the U.S. Centers for Disease Control and Prevention. They also used a machine learning model to predict the prevalence of these conditions based on patterns in the data and to compare the associations observed with microplastics concentration to linkages with 154 other social and environmental factors such as median household income, employment rate and particulate matter air pollution in the same areas.
The results revealed that microplastics concentration was positively correlated with high blood pressure, diabetes and stroke, while cancer was not consistently linked with microplastics pollution. The results also suggested a dose relationship, in which higher concentrations of microplastic pollution are associated with a higher prevalence of disease. However, researchers said that evidence of an association does not necessarily mean that microplastics are causing these health problems. More studies are required to determine whether there is a causal relationship or if this pollution is occurring alongside another factor that leads to health issues, they said.
Further research is also needed to determine the amount of exposure or the length of time it might take for microplastics exposure to have an impact on health, if a causal relationship exists, according to Ponnana. Nevertheless, based on the available evidence, it is reasonable to believe that microplastics may play some role in health and we must take steps to reduce exposures, he said. While it is not feasible to completely avoid ingesting or inhaling microplastics when they are present in the environment, given how ubiquitous and tiny they are, researchers said the best way to minimise microplastics exposure is to curtail the amount of plastic produced and used, and to ensure proper disposal.
“The environment plays a very important role in our health, especially cardiovascular health,” Ponnana said. “As a result, taking care of our environment means taking care of ourselves.”
In a separate study presented at ACC.25, researchers from a different group reviewed the scientific literature and found that studies showed a strong correlation between microplastics in plaques in the heart’s arteries and the risk of adverse cardiovascular events, suggesting that the presence of microplastics could play a role in the onset or exacerbation of serious heart problems.
This effect even occurs with virtual nature – such as nature videos
Photo by Sebastian Unrau on Unsplash
In a new study, an international team of neuroscientists led by the University of Vienna has shown that experiencing nature can alleviate acute physical pain. Surprisingly, simply watching nature videos was enough to relieve pain. Using functional magnetic resonance imaging, the researchers found that acute pain was rated as less intense and unpleasant when watching nature videos – along with a reduction in brain activity associated with pain. The results, published in Nature Communications, suggest that nature-based therapies can be used as promising complementary approaches to pain management.
“Pain processing is a complex phenomenon” explains study lead and doctoral student Max Steininger from the University of Vienna. In order to better understand it and identify treatment options, Steininger and his colleagues investigated how nature exposure influences pain: participants suffering from pain were shown three types of videos: a nature scene, an indoor scene, and an urban scene. The participants rated the pain while their brain activity was measured using functional magnetic resonance imaging. The results were clear: when viewing the nature scene, the participants not only reported less pain but also showed reduced activity in brain regions associated with pain processing.
By analyzing the brain data, the researchers showed that viewing nature reduced the raw sensory signal the brain receives when in pain. “Pain is like a puzzle, made up of different pieces that are processed differently in the brain. Some pieces of the puzzle relate to our emotional response to pain, such as how unpleasant we find it. Other pieces correspond to the physical signals underlying the painful experience, such as its location in the body and its intensity. Unlike placebos, which usually change our emotional response to pain, viewing nature changed how the brain processed early, raw sensory signals of pain. Thus, the effect appears to be less influenced by participants’ expectations, and more by changes in the underlying pain signals,” explains Steininger.
Claus Lamm, head of research in the group, adds: “From another ongoing study, we know that people consistently report feeling less pain when exposed to natural environments. However, the underlying reason for this has remained unclear – until now. Our study suggests that the brain reacts less to both the physical source and the intensity of the pain.”
The current study provides important information on how nature can help alleviate pain and highlights that nature-based therapeutic approaches can be a useful addition to pain treatment. The fact, that this effect was observed by simply watching nature videos suggests that taking a walk outdoors may not be necessary. Virtual nature – such as videos or virtual reality – appears to be effective as well. This opens up a wide range of possible applications in both the private and medical sectors, providing people with a simple and accessible way to relieve their pain.
The study was conducted at the University of Vienna in collaboration with researchers from the Universities of Exeter and Birmingham (UK) and the Max Planck Institute for Human Development.
Good news for tea lovers: That daily brew might be purifying the water, too. In a new study, Northwestern University researchers demonstrated that brewing tea naturally adsorbs heavy metals like lead and cadmium, effectively filtering dangerous contaminants out of drinks. Heavy metal ions stick to, or adsorb to, the surface of the tea leaves, where they stay trapped.
“We’re not suggesting that everyone starts using tea leaves as a water filter,” said Northwestern’s Vinayak P. Dravid, the study’s senior author. “In fact, we often utilise model experiments and tweak diverse parameters to probe and understand the scientific principles and phenomena involved in capture/release cycles of contaminants. For this study, our goal was to measure tea’s ability to adsorb heavy metals. By quantifying this effect, our work highlights the unrecognised potential for tea consumption to passively contribute to reduced heavy metal exposure in populations worldwide.”
“I’m not sure that there’s anything uniquely remarkable about tea leaves as a material,” said Benjamin Shindel, the study’s first author. “They have a high active surface area, which is a useful property for an adsorbent material and what makes tea leaves good at releasing flavor chemicals rapidly into your water. But what is special is that tea happens to be the most consumed beverage in the world. You could crush up all kinds of materials to get a similar metal-remediating effect, but that wouldn’t necessarily be practical. With tea, people don’t need to do anything extra. Just put the leaves in your water and steep them, and they naturally remove metals.”
Exploring different variables
To conduct the study, the Northwestern team explored how different types of tea, tea bags and brewing methods affect heavy metal adsorption. The various varieties tested included “true” teas such as black, green, oolong and white, as well as chamomile and rooibos teas. They also examined the differences between loose-leaf and commercially bagged tea.
The researchers created water solutions with known amounts of lead and other metals (chromium, copper, zinc and cadmium), and then heated the solutions to just below boiling temperature. Next, they added the tea leaves, which steeped for various time intervals, from mere seconds to 24 hours.
After steeping, the team measured how much of the metal content remained in the water. By comparing metal levels before and after adding the tea leaves, they were able to calculate how much was effectively removed.
Cellulose bags work best — and don’t release microplastics
After multiple experiments, Dravid, Shindel and their team identified several trends. Perhaps somewhat unsurprising: The bag matters. After testing different types of bags without tea inside, the researchers found cotton and nylon bags only absorbed trivial amounts of the contaminants. The cellulose bags, however, worked incredibly well.
The key to a successful sorbent material is high surface area. Similar to how a magnet attaches to a refrigerator door, metal ions cling to the surface of a material. So, the more area for the particles to stick to, the better. Shindel posits that cellulose, which is a biodegradable natural material made from wood pulp, has higher surface area – and therefore more binding sites – than sleeker synthetic materials.
“The cotton and nylon bags remove practically no heavy metals from water,” Shindel said. “Nylon tea bags are already problematic because they release microplastics, but the majority of tea bags used today are made from natural materials, such as cellulose. These may release micro-particles of cellulose, but that’s just fiber which our body can handle.”
Longer steeping time, fewer metals
When comparing different varieties of tea, the researchers discovered tea type and grind played minor roles in adsorbing contaminants. Finely ground tea leaves, particularly black tea leaves, absorbed slightly more metal ions than whole leaves. Again, the researchers attributed this to surface area.
“When tea leaves are processed into black tea, they wrinkle and their pores open,” Shindel explained. “Those wrinkles and pores add more surface area. Grinding up the leaves also increases surface area, providing even more capacity for binding.”
Out of all the experiments, one factor stood out most. Steeping time played the most significant role in tea leaves’ ability to adsorb metal ions. The longer the steeping time, the more contaminants were adsorbed.
“Any tea that steeps for longer or has higher surface area will effectively remediate more heavy metals,” Shindel said. “Some people brew their tea for a matter of seconds, and they are not going to get a lot of remediation. But brewing tea for longer periods or even overnight – like iced tea – will recover most of the metal or maybe even close to all of the metal in the water.”
Future opportunities
Although results depend on several factors – steeping time and water-to-tea ratio, for example – tea preparation removes an amount of lead from water that should be significant from a public health perspective.
From their experiments, the researchers estimate that tea preparation can remediate about 15% of lead from drinking water, even up to lead concentrations as high as 10 parts per million. That estimate applies only to a “typical” cup of tea, which includes one mug of water and one bag of tea, brewed for three to five minutes. Changing the parameters remediates different levels of lead. Steeping for longer than five minutes, for example, adsorbs more lead compared to the average steeping time.
“Ten parts lead per million is obviously incredibly toxic,” Shindel said. “But with lower concentrations of lead, tea leaves should remove a similar fraction of the metal content in the water. The primary limiting factor is how long you brew your tea for.”
In high-resource areas of the world, it’s unlikely that concentrations will reach such high levels. And if there is a water crisis, brewing tea will not solve the problem. But Shindel said the study’s results provide useful new information that could be applied to public health research.
“Across a population, if people drink an extra cup of tea per day, maybe over time we’d see declines in illnesses that are closely correlated with exposure to heavy metals,” he said. “Or it could help explain why populations that drink more tea may have lower incidence rates of heart disease and stroke than populations that have lower tea consumption.”
Exposure to high ambient temperatures is associated with lower connectivity in three brain networks in preadolescents, suggesting that heat may impact brain function. This is the conclusion of a study led by the Barcelona Institute for Global Health (ISGlobal). The results have been published in the Journal of the American Academy of Child & Adolescent Psychiatry.
The study involved 2229 children aged 9 to 12 from the “Generation R” cohort in Rotterdam, Netherlands. Functional connectivity data from brain networks, i.e., how different regions of the brain communicate and collaborate, were assessed using resting-state magnetic resonance imaging, when the children were not performing any active tasks. Daily mean temperature estimates were obtained from the UrbClim urban climate model, developed by the Flemish Institute for Technological Research. Temperature values were calculated for the period from 2013 to 2015, assigning daily averages to each participant based on their home address.
Higher ambient temperatures during the week preceding the MRI assessment were associated with lower functional connectivity within the medial parietal, salience, and hippocampal networks, which are essential for proper brain functioning. This implies that brain areas may work less synchronously, affecting processes such as attention, memory, and decision-making. The medial parietal network is related to introspection and self-perception; the salience network detects environmental stimuli and prioritises what deserves our attention; and the hippocampal network is critical for memory and learning.
The research shows that the association between high temperatures and lower functional connectivity was strongest on the day before the brain scan and progressively decreased on subsequent days. In contrast, low average daily temperatures were not associated with functional connectivity.
“We hypothesise that dehydration could explain our findings, as children are particularly vulnerable to fluid loss when exposed to heat, which can affect the functional connectivity of brain networks,” says study lead author Laura Granés, researcher at IDIBELL and ISGlobal.
“In the current climate emergency, public health policies aimed at protecting children and adolescents from high temperatures could help mitigate potential effects on brain function,” says Mònica Guxens, ICREA researcher at ISGlobal and senior author of the study.
Implications for mental health
Although brain function alterations have been suggested as a possible mechanism linking temperature and mental health, no study to date has examined the effects of ambient temperature on functional brain networks. In another recent study, the same research team found that exposure to cold and heat can affect psychiatric symptoms such as anxiety, depression and attention problems. In addition, other studies have linked lower connectivity within the brain’s salience network to suicidal ideation and self-harming behaviours in adolescents with depression, as well as to anxiety disorders.
“Given the role of the salience network in suicidal ideation, our findings raise a new hypothesis: high temperatures could decrease the functional connectivity of this network, indirectly contributing to a higher risk of suicide in individuals with pre-existing mental health conditions,” explains Carles Soriano-Mas, researcher at IDIBELL and the University of Barcelona and one of the study’s authors. “While we do not propose that these connectivity changes, triggered by heat exposure, directly induce suicidal behaviours, they could act as a trigger in vulnerable individuals,” adds the researcher.
A new USC Leonard Davis School of Gerontology study suggests greater exposure to extreme heat may accelerate biological aging in older adults, raising new concerns about how climate change and heat waves could affect long-term health and aging at the molecular level.
People in neighbourhoods that experience more days of high heat show greater biological aging on average than residents of cooler regions, said Jennifer Ailshire, senior author of the study, which appears in Science Advances. Ailshire is professor of gerontology and sociology at the USC Leonard Davis School.
Biological age is a measure of how well the body functions at the molecular, cellular, and system levels, as opposed to chronological age based on one’s birthdate; having a biological age greater than one’s chronological age is associated with higher risk for disease and mortality. While exposure to extreme heat has itself long been associated with negative health outcomes, including increased risk of death, heat’s link to biological aging has been unclear.
Measuring epigenetic changes
Ailshire and her coauthor Eunyoung Choi, USC Leonard Davis PhD in Gerontology alumna and postdoctoral scholar, examined how biological age changed in more than 3600 Health and Retirement Study (HRS) participants aged 56 and older from throughout the U.S. Blood samples taken at various time points during the six-year study period were analysed for epigenetic changes, or changes in the way individual genes are turned “off” or “on” by a process called DNA methylation.
The researchers used mathematical tools called epigenetic clocks to analyse methylation patterns and estimate biological ages at each time point. They then compared participants’ changes in biological age to their location’s heat index history and number of heat days reported by the National Weather Service from 2010 to 2016.
The National Weather Service Heat Index Chart categorises heat index values into three levels based on the potential risk of adverse health effects. The “Caution” level includes heat index values ranging from 80°F (27°C) to 90°F (32°C), the “Extreme Caution” level includes values between 90°F (32°C) and 103°F (34°C), and the “Danger” level includes values between 103°F (34°C) and 124°F (51°C). Days in all three levels were included as heat days in the study.
The analysis revealed a significant correlation between neighbourhoods with more days of extreme heat and individuals experiencing greater increases in biological age, Choi said. This correlation persisted even after controlling for socioeconomic and other demographic differences, as well as lifestyle factors such as physical activity, alcohol consumption and smoking, she added.
“Participants living in areas where heat days, as defined as Extreme Caution or higher levels (32°C), occur half the year, such as Phoenix, Arizona, experienced up to 14 months of additional biological aging compared to those living in areas with fewer than 10 heat days per year,” she said. “Even after controlling for several factors, we found this association. Just because you live in an area with more heat days, you’re aging faster biologically.”
All three epigenetic clocks employed in the study – PCPhenoAge, PCGrimAge, and DunedinPACE – revealed this association when analysing epigenetic aging over a 1- to 6-year period. PCPhenoAge also showed the association after short (7 days) and medium (30-60 days) periods of time, indicating that heat-related epigenetic changes could happen relatively quickly, and some of them may accumulate over time.
Climate implications for communities
Older adults are particularly vulnerable to the effects of high heat, Ailshire said. She noted that the study used heat index, rather than just air temperature, to take relative humidity into account as they analyzed results.
“It’s really about the combination of heat and humidity, particularly for older adults, because older adults don’t sweat the same way. We start to lose our ability to have the skin-cooling effect that comes from that evaporation of sweat,” she explained. “If you’re in a high humidity place, you don’t get as much of that cooling effect. You have to look at your area’s temperature and your humidity to really understand what your risk might be.”
The next steps for the researchers will be to determine what other factors might make someone more vulnerable to heat-related biological aging and how it might connect to clinical outcomes. In the meantime, the study results could also prompt policymakers, architects, and others to keep heat mitigation and age-friendly features in mind as they update cities’ infrastructure, from placing sidewalks and building bus stops with shade in mind to planting more trees and increasing urban green space, Ailshire said.
“If everywhere is getting warmer and the population is aging, and these people are vulnerable, then we need to get really a lot smarter about these mitigation strategies,” she said.
From early ocean dips to ice-cold polar plunges, cold-water immersion is increasingly popular among athletes and wellness warriors. But how much of the hype is backed by science?
In the most comprehensive systematic review and meta-analysis of its kind, University of South Australia researchers have taken a deep dive into the effects of cold-water immersion on health and wellbeing.
Analysing data from 11 studies with 3177 participants, researchers found that cold-water immersion may lower stress, improve sleep quality, and boost quality of life.
UniSA researcher Tara Cain says the study, which appears in PLOS ONE, reveals time-dependant and nuanced effects on health and wellbeing measures.
“Cold-water immersion has been extensively researched and used in sporting contexts to help athletes recover, but despite its growing popularity among health and wellbeing circles, little is known about its effects on the general population,” Cain says.
“In this study, we noted a range of time-dependant results. Firstly, we found that cold-water immersion could reduce stress levels, but for only about 12 hours post exposure.
“We also noted that participants who took 20, 60, or 90 second cold showers reported slightly higher quality of life scores. But again, after three months these effects had faded.
“Benefits may be gained from cold showers as well, with one study reporting that participants who took regular cold showers experiencing a 29% reduction in sickness absence.
“We also found some links to cold-water immersion and better sleep outcomes, but the data was restricted to males, so its broader application is limited.
“And while there have been many claims that cold-water immersion experiences can boost your immunity and mood, we found very little evidence to support these claims.”
Cold-water immersion involves immersing the body partially or fully in cold water, in temperatures typically ranging from 10-15°C, and in this study, data was only included if exposure was at or above chest level, and for a minimum time of 30 seconds. It included cold showers, ice baths and cold plunges.
Co-researcher, UniSA’s Dr Ben Singh says the study also showed that cold-water immersion caused a temporary increase in inflammation.
“At first glance this seems contradictory, as we know that ice baths are regularly used by elite athletes to reduce inflammation and muscle soreness after exercise,” Dr Singh says.
“The immediate spike in inflammation is the body’s reaction to the cold as a stressor. It helps the body adapt and recover and is similar to how exercise causes muscle damage before making muscles stronger, which is why athletes use it despite the short-term increase.
“Knowing this, people with pre-existing health conditions should take extra care if participating in cold-water immersion experiences as the initial inflammation could have detrimental health impacts.”
Researchers say that while the findings highlight the potential benefits of cold-water immersion, they also underscore the highly time-dependent and contextual nature of its effects.
“Whether you are an elite athlete or everyday wellness seeker – it’s important to understand the effects of what you put your body through,” Cain says.
“Right now, there isn’t enough high-quality research to say exactly who benefits most or what the ideal approach is to cold-water immersion. More long-term studies, among more diverse populations, are needed to understand its lasting effects and practical applications.”
Air pollution is a well-known risk factor for respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) – but its contribution to lower respiratory infections is less well known, especially in adults. To address this, a team from the Barcelona Institute for Global Health (ISGlobal), a centre supported by the ”la Caixa” Foundation, assessed the effect of air pollution on hospital admissions for lower respiratory infections in adults, and which subgroups that could be particularly vulnerable to these infections. The results have been published in the journalEnvironment International.
The research shows that long-term exposure to particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2) and ozone (O3) air pollution is associated with more hospital admissions for lower respiratory tract infections in adults. The associations were stronger in men, people over 65 years of age and those diagnosed with hypertension.
The study involved 3 800 000 adults from the COVAIR-CAT cohort, a large cohort of 7.7 million people based on the health system of Catalonia. The research team used exposure models to estimate annual average concentrations of PM2.5, PM10, NO2 and ozone during the warm season (May-September) between 2018 and 2020 at the participants’ residences. Information on hospital admissions, mortality and comorbidities was obtained from various administrative databases. The study included hospital admissions for all lower respiratory infections and, separately, the subgroup of hospital admissions for influenza and pneumonia. A statistical model was then used to assess the association between air pollution and hospital admissions.
“The association between air pollution and hospital admissions for lower respiratory tract infections was observed even at pollution levels below current EU air quality standards,” says Anna Alari, ISGlobal researcher and first author of the study. “It is crucial to adopt stricter air quality standards, as more ambitious measures to reduce air pollution would decrease hospital admissions and protect vulnerable populations,” she adds.
Stronger association in men and people over 65
The association between air pollution and hospitalisations for lower respiratory tract infections was more pronounced in people over 65 years of age or with comorbidities, compared with younger people or those without comorbidities. Specifically, elevated levels of air pollution were associated with approximately three times higher rates of hospital admissions for lower respiratory infections among people aged 65 years and older compared with younger people.
In addition, exposure to elevated levels of NO2, PM2.5 or PM10 (but not O3) was associated with about a 50% increase in hospital admissions in men, while the association was about 3% higher in women.
The team observed the same pattern for hospital admissions for influenza or pneumonia, but with smaller associations compared to lower respiratory infections. “This may be due to the influence of available vaccines against the pathogens responsible for influenza and most cases of pneumonia,” says Cathryn Tonne, senior author of the study.
People experienced less stress and anxiety while listening to nature soundscapes, but the addition of road traffic noise increased their stress and anxiety
Photo by Lucas Davies on Unsplash
Manmade sounds such vehicle traffic can mask the positive impact of nature soundscapes on people’s stress and anxiety, according to a new study published November 27, 2024, in the open-access journal PLOS ONE by Paul Lintott of the University of the West of England, U.K., and Lia Gilmour of the Bat Conservation Trust, U.K.
Existing research shows that natural sounds, like birdsong, can lower blood pressure, heart, and respiratory rates, as well as self-reported stress and anxiety. Conversely, anthropogenic soundscapes, like traffic or aircraft noise, are hypothesized to have negative effects on human health and wellbeing in a variety of ways.
In the new study, 68 student volunteers listened to three 3-minute soundscapes: a nature soundscape recorded at sunrise in West Sussex, U.K., the same soundscape combined with 20 mile per hour road traffic sounds, and the same soundscape with 40 mile per hour traffic sounds. General mood and anxiety were assessed before and after the soundscapes using self-reported scales.
The study found that listening to a natural soundscape reduced self-reported stress and anxiety levels, and also enhanced mood recovery after a stressor. However, the benefits of improved mood associated with the natural soundscape was limited when traffic sounds were included. The natural soundscape alone was associated with the lowest levels of stress and anxiety, with the highest levels reported after the soundscape that included 40 mile per hour traffic.
The authors conclude that reducing traffic speed in urban areas might influence human health and wellbeing not only through its safety impacts, but also through its effect on natural soundscapes.
The authors add: “Our study shows that listening to natural soundscapes can reduce stress and anxiety, and that anthropogenic sounds such as traffic noise can mask potential positive impacts. Reducing traffic speeds in cities is therefore an important step towards more people experiencing the positive effects of nature on their health and wellbeing.”
A team of University of Utah chemists have found that carbon dioxide, well-known for being deadly at high concentrations, also has an important beneficial effect in preserving cell function. This is something not accounted for in most in vitro experiments of cell damage, and may have important consequences for understanding environments with high CO2 concentrations, like underground mines, submarines and spacecraft.
The cells in our bodies are like bustling cities, running on an iron-powered system that uses hydrogen peroxide (H₂O₂) not just for cleaning up messes but also for sending critical signals. Normally, this works fine, but under stress, such as inflammation or a burst of energy use, oxidative stress damages cells at the genetic level.
This is because iron and H₂O₂ react in what’s known as the Fenton reaction, producing hydroxyl radicals, destructive molecules that attack DNA and RNA indiscriminately. But there’s a catch. In the presence of carbon dioxide, our cells gain a secret weapon in the form of bicarbonate which helps keep pH levels balanced.
In this study, the researchers discovered that bicarbonate doesn’t just act as a pH buffer but also alters the Fenton reaction itself in cells. Instead of producing chaotic hydroxyl radicals, the reaction instead makes carbonate radicals, which affect DNA in a far less harmful way, according to Cynthia Burrows, a distinguished professor of chemistry and senior author of a study published this week in PNAS.
“So many diseases, so many conditions have oxidative stress as a component of disease. That would include many cancers, effectively all age-related diseases, a lot of neurological diseases,” Burrows said. “We’re trying to understand cells’ fundamental chemistry under oxidative stress. We have learned something about the protective effect of CO₂ that I think is really profound.”
Without bicarbonate or CO₂ present in experimental DNA oxidation reactions, the chemistry is also different. The free radical species generated, hydroxyl radical, is extremely reactive and hits DNA like a shotgun blast, causing damage everywhere, Burrows said.
In contrast, her team’s findings show that the presence of bicarbonate from dissolved CO₂ changes the reaction to make a milder radical striking only guanine, the G in our four-letter genetic code.
“Like throwing a dart at the bullseye where G is the center of the target,” Burrows said. “It turns out that bicarbonate is a major buffer inside your cells. Bicarbonate binds to iron, and it completely changes the Fenton reaction. You don’t make these super highly reactive radicals that everyone’s been studying for decades.”
What do these findings mean for science? Potentially a lot.
For starters, the team’s discovery shows cells are a lot smarter than previously imagined, which could reshape how we understand oxidative stress and its role in diseases like cancer or aging.
But it also raises the possibility that many scientists studying cell damage have been conducting laboratory experiments in ways that don’t reflect the real world, rendering their results suspect, Burrows said. Chemists and biologists everywhere grow cells in a tissue culture in an incubator set to 37°C. In these cultures, carbon dioxide levels are raised to 5%, or about 100 times more concentrated than what’s found in the atmosphere.
The elevated CO₂ recreates the environment the cells normally inhabit as they metabolise nutrients, however, it is lost when researchers start their experiments outside the incubator.
“Just like opening up a can of beer. You release the CO₂ when you take your cells out of the incubator. It’s like doing experiments with a day-old glass of beer. It’s pretty flat. It has lost the CO₂, its bicarbonate buffer,” Burrows said. “You no longer have the protection of CO₂ to modulate the iron-hydrogen peroxide reaction.”
She believes bicarbonate needs to be added to ensure reliable results from such experiments.
“Most people leave out bicarbonate/CO₂ when studying DNA oxidation because it is difficult to deal with the constant outgassing of CO₂,” Burrows said. “These studies suggest that to get an accurate picture of DNA damage that occurs from normal cellular processes like metabolism, researchers need to be careful to mimic the proper conditions of the cell and add bicarbonate, ie baking powder!”
Burrows anticipates her study could result in unintended outcomes that may someday benefit research in other areas. Her lab is seeking new funding from NASA, for example, to study the effect of CO₂ on people confined to enclosed spaces, such as inside of space capsules and submarines.
“You’ve got astronauts in a capsule living and breathing, and they are exhaling CO₂. The problem is how much CO₂ can they safely handle in their atmosphere? One of the things we found is that, at least in terms of tissue culture, CO₂ does have a protective effect from some of the radiation damage these astronauts might experience. So what you might want to do is push up that CO₂ level. You certainly don’t want to go very high, but having it slightly higher might actually have a protective effect against radiation, which generates hydroxyl radicals.”
