New nationwide modeling points to widespread racial disparities in urban heat stress

 From densely built urban cores to sprawling suburbia, cities are complex. This complexity can lead to temperature hot spots within cities, with some neighborhoods (and their residents) facing more heat than others.

Understanding this environmental disparity forms the spirit of new research led by scientists at the Department of Energy's Pacific Northwest National Laboratory. In a new paper examining all major cities in the U.S., the authors find that the average Black resident is exposed to air that is warmer by 0.28 degrees Celsius relative to the city average. In contrast, the average white urban resident lives where air temperature is cooler by 0.22 degrees Celsius relative to the same average.

The new work, published last week in the journal One Earth, involved a two-part effort. The study's authors aimed to produce a more useful nationwide estimate of urban heat stress -- a more accurate account of how our body responds to outdoor heat. By creating and comparing these estimates against demographic data, they also tried to better understand which populations are most exposed to urban heat stress.

The findings reveal pervasive income- and race-based disparities within U.S. cities. Nearly all the U.S. urban population -- 94 percent, or roughly 228 million people -- live in cities where summertime peak heat stress exposure disproportionately burdens the poor.

The study's authors also find that people who now live within historically redlined neighborhoods, where loan applicants were once denied on racially discriminatory grounds, would be exposed to higher outdoor heat stress than their neighbors living in originally non-redlined parts of the city.

The work also highlights shortcomings in the typical approach scientists take in estimating urban heat stress at these scales, which frequently relies on satellite data. This conventional satellite-based method can overestimate such disparities, according to the new work. As the world warms, the findings stand to inform urban heat response plans put forward by local governments who seek to help vulnerable groups.

What is heat stress?

The human body has evolved to operate within a relatively narrow temperature range. Raise your core body temperature beyond just six or seven degrees and drastic physiological consequences soon follow. Cellular processes break down, the heart is taxed, and organs begin to fail.

Sweating helps. But the cooling power of sweating depends partly on how humid the environment is. When both heat and humidity are omnipresent and difficult to escape, the body struggles to adapt.

How is heat stress measured?

To measure heat stress, scientists use a handful of indicators, many of which depend on air temperature and humidity. Weather stations provide such data. Because most weather stations are outside of cities, though, scientists often rely on other means to get some idea about urban heat stress, including using sensors on satellites.

Those sensors infer the temperature of the land surface from measurements of thermal radiation. But such measurements fall short of delivering a full picture of heat stress, said lead author and Earth scientist TC Chakraborty. Measuring just the skin of the Earth, like the surface of a sidewalk or a patch of grass, said Chakraborty, offers only an idea of what it's like to lay flat on that surface.

"Unless you're walking around barefoot or lying naked on the ground, you're not really feeling that," said Chakraborty. "Land surface temperature is, at best, a crude proxy of urban heat stress."

Indeed, most of us are upright, moving through a world where air temperature and moisture dictate how heat actually feels. And these satellite data are only available for clear-sky days -- another limiting factor. More complete and physiologically relevant estimates of heat stress incorporate a blend of factors, which models can provide, said Chakraborty.

To better understand differences between satellite-derived land surface temperature and ambient heat exposure within cities, Chakraborty's team examined 481 urbanized areas across the continental United States using both satellites and model simulations.

NASA's Aqua satellite provided the land surface temperature; and through model simulations that account for urban areas, the authors generated nationwide estimates of all variables required to calculate moist heat stress. Two such metrics of heat stress -- the National Weather Service's heat index and the Humidex, often used by Canadian meteorologists -- allowed the scientists to capture the combined impacts of air temperature and humidity on the human body.

They then identified heat stress hotspots across the country for summer days between 2014 and 2018. Overlaying maps of both historically redlined neighborhoods and census tracts, the team identified relationships between heat exposure and communities.

How is heat distributed within cities?

Residents in poorer neighborhoods often face greater heat stress. And a greater degree of income inequality in any given city often means greater heat stress exposure for its poorer residents.

Most U.S. cities, including heavily populated cities like New York, Los Angeles, Chicago, and Philadelphia, show this disparity. But the relationship between heat stress and race-based residential segregation is even more stark.

Roughly 87.5 percent of the cities studied show that Black populations live in parts of the city with higher land surface temperatures, warmer air, and greater moist heat stress. Moreover, the association between the degree of heat stress disparity and the degree of segregation between white and non-white populations across cities is particularly striking, said Chakraborty.

"The majority -- 83 percent -- of non-white U.S. urban residents live in cities where outdoor moist heat stress disproportionately burdens them," said Chakraborty, "Further, higher percentages of all races other than white are positively correlated with greater heat exposure no matter which variable you use to assess it."

In the 1930s, the U.S. federal government's Home Owners' Loan Corporation graded neighborhoods in an effort to rank the suitability of real estate investments. This practice is known as "redlining," where lower grades (and consequently fewer loans) were issued to neighborhoods composed of poorer and minority groups. The authors find that these redlined neighborhoods still show worse environmental conditions.

Neighborhoods with lower ratings face higher heat exposure than their non-redlined neighbors. Neighborhoods with higher ratings, in contrast, generally get less heat exposure.

This is consistent with previous research on originally redlined urban neighborhoods showing lower tree cover and higher land surface temperature. Chakraborty, however, notes that using land surface temperature would generally overestimate these disparities across neighborhood grades compared to using air temperature or heat index.

"Satellites give us estimates of land surface temperature, which is a different variable from the temperature we feel while outdoors, especially within cities," said Chakraborty. "Moreover, the physiological response to heat also depends on humidity, which satellites cannot directly provide, and urbanization also modifies."

The findings are not without uncertainty, the authors added. "Ground-based weather stations helped to dwindle down, but not eliminate, model bias," said co-author Andrew Newman of the National Center for Atmospheric Research, who generated the model simulations. However, the results are still consistent with both theory and previous large-scale observational evidence.

What can be done?

Planting more trees often comes up as a potential solution to heat stress, said Chakraborty. But densely built urban cores, where poorer and minority populations in the U.S. often live, have limited space for trees. And many previous estimates of vegetation's potential to cool city surroundings are also based solely on land surface temperature -- they are perhaps prone to similar overestimation, the authors suggest.

More robust measurements of urban heat stress would help, they added. Factors like wind speed and solar insolation contribute to how heat actually affects the human body. But those factors are left out of most scientific assessments of urban heat stress because they are difficult to measure or model at neighborhood scales.

Novel study deepens knowledge of treatment-resistant hypertension

 For many patients with hypertension -- an elevated blood pressure that can lead to stroke or heart attack -- medication keeps the condition at bay. But what happens when medication that physicians usually prescribe doesn't work? Known as apparent resistant hypertension (aRH), this form of high blood pressure requires more medication and medical management.

Novel research from investigators in the Smidt Heart Institute at Cedars-Sinai, published today in the peer-reviewed journal Hypertension, found that aRH prevalence was lower in a real-world sample than previously reported, but still relatively frequent -- affecting nearly 1 in 10 hypertensive patients.

Through their analysis, investigators also learned that patients with well-managed aRH were more likely to be treated with a commonplace medication called mineralocorticoid receptor antagonist, or MRA. These MRA treatments were used in 34% of patients with controlled aRH, but only 11% of patients with uncontrolled aRH.

"Apparent resistant hypertension is more common than many would anticipate," said Joseph Ebinger, MD, assistant professor of Cardiology in the Smidt Heart Institute and corresponding author of the study. "We also learned that within this high-risk population, there are large differences in how providers treat high blood pressure, exemplifying a need to standardize care."

Study findings were based on a unique design, which used clinically generated data from the electronic health records of three large, geographically diverse healthcare organizations. Of the 2,420,468 patients analyzed in the study, 55% were hypertensive. Of these hypertension patients, 8.5%, or 113,992 individuals, met criteria for aRH.

According to Ebinger, treating aRH can be just as tricky as diagnosing it.

In fact, the "apparent" in apparent resistant hypertension stems from the fact that before diagnosis, medical professionals must first rule out other potential reasons for a patient's blood pressure to be high.

These reasons might include medication non-adherence, inappropriate medication selection, or artificially elevated blood pressure in the doctor's office -- known as "white coat hypertension."

"Large amounts of data tell us that patients with aRH, compared to those with non-resistant forms of hypertension, are at greatest risk for adverse cardiovascular events," said Ebinger, director of Clinical Analytics in the Smidt Heart Institute. "Identifying these patients and possible causes for their elevated blood pressure is increasingly important."

The takeaway, Ebinger says, is awareness -- for both medical professionals and patients. He says providers should be mindful that if it's taking four or more antihypertensive medications to control a patient's blood pressure, they should consider evaluation for alternative causes of hypertension, or refer patients to a specialist.

Similarly, patients should lean on their medical providers to help them navigate the complex disease, including having a conversation around strategies for remembering to take their medication and addressing possible treatment side effects.

Treating patients with complex cardiac issues like aRH is at the heart of Cedars-Sinai's expertise.

The Smidt Heart Institute was recently awarded the American Heart Association's Comprehensive Hypertension Center Certification, recognizing the institute's commitment to following proven, research-based treatment guidelines to care for people with complex or difficult-to-treat hypertension.

"This accreditation, coupled with our clinical and research expertise in hypertensive diseases, serves as a mark of excellence," said Christine M. Albert, MD, MPH, chair of the Department of Cardiology and the Lee and Harold Kapelovitz Distinguished Chair in Cardiology. "These efforts signal to patients, healthcare providers, and the community that the Smidt Heart Institute is committed to delivering evidence-based, comprehensive care for hypertension."

Lean body mass, age linked with alcohol elimination rates in women

 The rate at which women eliminate alcohol from their bloodstream is largely predicted by their lean body mass, although age plays a role, too, scientists found in a new study. Women with obesity -- and those who are older -- clear alcohol from their systems 52% faster than women of healthy weights and those who are younger, the study found.

Lean body mass is defined in the study -- published in the journal Alcohol Clinical and Experimental Research -- as one's total body weight minus fat.

"We believe the strong relationship we found between participants' lean body mass and their alcohol elimination rate is due to the association that exists between lean body mass and lean liver tissue -- the part of the liver responsible for metabolizing alcohol," said research group leader M. Yanina Pepino, a professor of food science and human nutrition at the University of Illinois Urbana-Champaign.

To explore links between body composition and alcohol elimination rates, the team conducted a secondary analysis of data from a study performed at the U. of I and another at Indiana University, Indianapolis. Both projects used similar methods to estimate the rate at which alcohol is broken down in the body.

The combined sample from the studies used in the analysis included 143 women who ranged in age from 21 to 64 and represented a wide range of body mass indices -- from healthy weights to severe obesity. Among these were 19 women who had undergone different types of bariatric surgery.

In a subsample of 102 of these women, the researchers had measured the proportions of lean and fat tissue in their bodies and calculated their body mass indices. Based on their BMI, those in the subsample were divided into three groups: normal weight, which included women with BMI ranging from 18.5-24.9; overweight, those with BMI ranging from 25-29.9; and obese, participants with BMI above 30.

As the researchers expected, women with higher BMI had not only more fat mass than women of healthy weights, they also had more lean mass. On average, the group with obesity had 52.3 kg of lean mass, compared with 47.5 kg for the normal weight group.

The two studies both used an alcohol clamp technique, where participants received an intravenous infusion of alcohol at a rate controlled by a computer-assisted system. The system calculated personalized infusion rates based upon each participant's age, height, weight and gender and was programmed so they would reach a target blood alcohol concentration of .06 percent within 15 minutes and maintain that level for about two hours

Using a breathalyzer, breath samples were collected at regular intervals throughout the experiments to estimate participants' blood alcohol concentration and provide feedback to the system.

"We found that having a higher fat-free body mass was associated with a faster alcohol elimination rate, particularly in women in the oldest subgroups," said Neda Seyedsadjadi, a postdoctoral fellow at the university and the first author of the study.

"The average alcohol elimination rates were 6 grams per hour for the healthy weight group, 7 grams for the overweight group, and 9 grams for the group with obesity," she said. "To put this in perspective, one standard drink is 14 grams of pure alcohol, which is found in 12 ounces of beer, 5 ounces of table wine or 1.5 ounces shot of distilled spirits."

The interaction between participants' age and lean body mass accounted for 72% of the variance in the time required to eliminate the alcohol from their system, the team found.

Pepino, who also holds an appointment as a health innovation professor at Carle Illinois College of Medicine, has conducted several studies on alcohol response in bariatric surgery patients.

The findings also shed light on alcohol metabolism and body composition in women who have undergone weight loss surgery. Researchers have long known that bariatric surgery alters women's response to alcohol but were uncertain if it affected how quickly they cleared alcohol from their systems.

Some prior studies found that these patients metabolized alcohol more slowly after they had weight loss surgery. The new study's findings indicate that these participants' slower alcohol elimination rates can be explained by surgery-induced reductions in their lean body mass. Weight loss surgery itself had no independent effects on patients' alcohol elimination rates, the team found.

Ants have a specialized communication processing center that has not been found in other social insects

 Have you ever noticed an ant in your home, only to find that a week later the whole colony has moved in? The traps you set up catch only a few of these ants, but soon, the rest of the colony has mysteriously disappeared. Now, a study published in the journal Cell on June 14 explores how certain danger-signaling pheromones -- the scent markers ants emit to communicate with each other -- activate a specific part of the ants' brains and can change the behavior of an entire nest.

"Humans aren't the only animals with complex societies and communication systems," says lead author Taylor Hart of The Rockefeller University. "Over the course of evolution, ants have evolved extremely complex olfactory systems compared to other insects, which allows them to communicate using many different types of pheromones that can mean different things."

This research suggests that ants have their own kind of communication center in their brains, similar to humans. This center can interpret alarm pheromones, or "danger signals," from other ants. This section of their brain may be more advanced than that of some other insects such as honeybees, which prior work has suggested instead rely on many different parts of their brain to coordinate in response to a single pheromone.

"There seems to be a sensory hub in the ant brain that all the panic-inducing alarm pheromones feed into," says corresponding author Daniel Kronauer of The Rockefeller University.

The researchers used an engineered protein called GCaMP to scan the brain activity of clonal raider ants that were exposed to danger signals. GCaMP works by attaching itself to calcium ions, which flare up with brain activity, and the resulting fluorescent chemical compound can be seen on high-resolution microscopes adapted to view them.

When performing the scans, the researchers noticed that only a small section of the ants' brains lit up in response to danger signals, but the ants still showed immediate and complex behaviors in response. These behaviors were named the "panic response" because they involved actions such as fleeing, evacuating the nest, and transporting their offspring from the nest toward a safer location.

Species of ants with different colony sizes also use different pheromones to communicate a variety of messages. "We think that in the wild, clonal raider ants usually have a colony size of just tens to hundreds of individuals, which is pretty small as far as ant colonies go," says Hart. "Frequently, these small colonies tend to have panic responses as their alarm behavior because their main goal is to get away and survive. They can't risk a lot of individuals. Army ants, the cousins of the clonal raider ants, have massive colonies -- hundreds of thousands or millions of individuals -- and they can be much more aggressive."

Regardless of the species, ants within a colony divide themselves by caste and role, and ants within different castes and roles have slightly different anatomy. For the purpose of this study, researchers chose clonal raider ants as a species because they are easy to control. They used ants of one sex within one caste and role (female worker ants) to ensure consistency and therefore make it easier to observe widespread patterns. Once researchers have a clearer understanding of the neural differences between castes, sexes, and roles, they may better be able to comprehend exactly how different ant brains process the same signals.

"We can start to look at how these sensory representations are similar or different between ants," says Hart. Kronauer says, "We're looking at division of labor. Why do individuals that are genetically the same assume different tasks in the colony? How does this division of labor work?"

This work was supported by the National Institute of General Medical Sciences of the National Institutes of Health, the National Institute of Neurological Disorders and Stroke, the Howard Hughes Medical Institute, the National Science Foundation, and the Kavli Neural Systems Institute.

10-year countdown to sea-ice-free Arctic

 If the world keeps increasing greenhouse gas emissions at its current speed, all sea ice in the Arctic will disappear in the 2030s, an event that could at best be postponed until the 2050s should emissions be somehow reduced. The prediction is a decade earlier than what the Intergovernmental Panel on Climate Change (IPCC) has projected: an ice-free Arctic by the 2040s.

A possible ice-free Arctic in the 2030-2050s was projected regardless of humanity's efforts to reduce its greenhouse gas emissions by Professor Seung-Ki Min and Research Professor Yeon-Hee Kim from the Division of Environmental Science and Engineering at Pohang University of Science and Technology (POSTECH) and a joint team of researchers from the Environment Climate Change Canada and Universität Hamburg, Germany. The research was published in the international journal, Nature Communications.

The term global warming has become a household name since it was first used by a climate scientist at NASA in 1988. The Earth has seen a rapid decline in the Arctic sea ice area as its temperature has increased over the past several decades. This reduction in Arctic sea ice has induced the acceleration of Arctic warming, which is suggested to contribute to the increased frequency of extreme weather events in mid-latitude regions.

To predict the timing of Arctic sea ice depletion, the research team analyzed 41 years of data from 1979 to 2019. By comparing the results of multiple model simulations with three satellite observational datasets, it was confirmed that the primary cause of the decline is attributed to 'human-made greenhouse gas emissions'. Greenhouse gas emissions resulting from human fossil fuel combustion and deforestation have been the primary drivers of Arctic sea ice decline over the past 41 years, while the influence of aerosols, solar and volcanic activities has been found to be minimal. Monthly analysis found that increased greenhouse gas emissions were reducing Arctic sea ice all year round, regardless of season or timing, although September exhibited the smallest extent of sea ice reduction.

Furthermore, it was revealed that climate models used in previous IPCC predictions generally underestimated the declining trend of sea ice area, which was taken into account to adjust the simulation values for future predictions. The results showed accelerated decline rates across all scenarios, most importantly confirming that Arctic sea ice could completely disappear by the 2050s even with reductions in greenhouse gas emissions. This finding highlights for the first time that the extinction of Arctic sea ice is possible irrespective of achieving 'carbon neutrality.'

The accelerated decline of Arctic sea ice, faster than previously anticipated, is expected to have significant impacts not only on the Arctic region but also on human societies and ecosystems worldwide. The reduction of sea ice can result in more frequent occurrences of extreme weather events such as severe cold waves, heat waves, and heavy rainfalls all across the globe, with the thawing of the Siberian permafrost in the Arctic region possibly intensifying global warming further. We may witness terrifying scenarios, which we have seen only in disaster movies, unfold right before our eyes.

Professor Seung-Ki Min, who led the study, explained, "We have confirmed an even faster timing of Arctic sea ice depletion than previous IPCC predictions after scaling model simulations based on observational data." He added, "We need to be vigilant about the potential disappearance of Arctic sea ice, regardless of carbon neutrality policies." He also expressed the importance of "evaluating the various climate change impacts resulting from the disappearance of Arctic sea ice and developing adaptation measures alongside carbon emission reduction policies."