There are so many diabolical possibilities, but which chemical is the most dangerous?

It comes down to a combination of effect and exposure—how much makes a deadly dose and what exactly will it do to you? Nerve agents are widely considered the most toxic chemical weapons owing to their tiny toxic limits and devastatingly rapid impacts on the human body: Just 10 milligrams (that’s ten thousandths of a gram) of VX is enough to cause death within minutes. Yet just one person has been killed by the nerve agent over the last decade.

Meanwhile, more than 100,000 people are accidentally poisoned in the U.S. every year by common household chemicals such as bleach and disinfectant, even though these substances are slower-acting and far less toxic than VX. And some common chemicals can be fatal when combined. For instance, combining drain cleaner and bleach will release poisonous chlorine gas. 

Those two examples highlight a key problem in ranking chemicals in order of danger: To evaluate danger, you need to know how likely you are to encounter a chemical.

Safety professionals define danger using a combination of two factors: hazard and risk. 

"A hazard is something with the potential to cause harm. Risk is the likelihood that harm will arise and the severity of that harm," said Richard Webb, the health, safety, environment and well-being officer at the University of Cardiff's School of Chemistry. The hazard is therefore a fixed property of a tool or chemical, while the risk varies depending on how that object is used.

We automatically consider this balance of factors every day. Take the example of a kitchen knife: We know the blade is sharp and will cut things, including us, in the right circumstances. But it's how we use and store the knife that determines whether it poses a danger to us, Webb told Live Science. 

Related: Can foxgloves really give you a heart attack?

This same logic applies to chemicals. "Even a very hazardous chemical does not pose any risk if there is no exposure," a spokesperson for the Finland-based European Chemicals Agency told Live Science. Botulinum toxin, VX and chlorine trifluoride are therefore extremely hazardous but very, very low risk to the average person.

"Some hazardous chemicals are also essential for our health in small doses," added the spokesperson, "whereas in higher exposures they may be lethal."

Ordinary table salt is an excellent example. The small amount in our diets is vital to maintain the correct ion balance within our bodies, but too much can cause severe health problems, like high blood pressure and heart failure. Outside the body, large quantities of that same salt act as a weedkiller by overwhelming plants' ion balance to the point of death.

Even determining which chemicals are the most hazardous is fraught with difficulty, as there are so many ways they could cause harm. In the European Union, classification, labeling and packaging regulations define nine hazardous characteristics, including toxic, explosive and corrosive. But again, Webb emphasized that which of these is most dangerous depends on the context.

For example, although chlorine is a common disinfectant in pools today, the concentrated gas was used as a chemical weapon in World War I and caused both chemical burns and respiratory irritation. The key difference though, is that pools include only a small amount of chlorine, and that small amount is dissolved into the water. "The thing that makes it high risk is the fact it's a gas," Webb said. 

On paper, sodium cyanide looks much worse. "It's famously poisonous. It binds to your hemoglobin permanently, which stops it from carrying oxygen so you can't respire," Webb said. However, as a solid, it's much easier to handle, meaning scientists using this toxic compound can more readily avoid the nasty effects of exposure. 

"If you work with it safely — you wear your PPE [personal protective equipment], work in a fume hood and wash your hands when you finish — the likelihood of contaminating yourself is pretty low," Webb explained.

This means our safety is often within our own control. Anything can become dangerous if it's not handled properly, but there are steps we can take to reduce the likelihood of harm. 

"The most important thing is knowing exactly what the hazards are and what you can do to minimize the risk," Webb said.

The odd red bodies, scientists say, hide stars that models suggest are "too old" to have lived during early cosmic times and black holes that measure up to thousands of times larger than the supermassive black hole at the heart of the Milky Way. Scientists believe these objects must have been born in a way unique to the early universe — by a method that seems to have ceased in the cosmos after around 1 billion years of its existence.

The three little red dots are seen as they were when the universe was between 600 million and 800 million years old. Though that may seem like a tremendously long time after the Big Bang, the fact that the universe is 13.8 billion years old means it was no more than 5% of its current age when these objects existed.

By confirming the existence of these dots in the early universe, these JWST findings could challenge what we know about the evolution of galaxies and the supermassive black holes that sit at their hearts.

RELATED: 35 jaw-dropping James Webb Space Telescope images

The team, led by scientists from Penn State University, saw these mysterious crimson cosmic oddities when investigating the early universe with the JWST's Near Infrared Spectrograph (NIRSpec) instrument as part of the RUBIES survey.

"It's very confusing," team member Joel Leja, an assistant professor of astronomy and astrophysics at Penn State, said in a statement. "You can make this uncomfortably fit in our current model of the universe, but only if we evoke some exotic, insanely rapid formation at the beginning of time.

"This is, without a doubt, the most peculiar and interesting set of objects I've seen in my career."

What's behind the dots?

The researchers studied the intensity of different wavelengths of light coming from the little red dots. This revealed signs that the stars are hundreds of millions of years old — far older than is expected for stars at this early stage of the cosmos.

The researchers also saw traces of supermassive black holes within the little red dots' regions with masses equivalent to millions, sometimes even billions, of suns. These black holes are between 100 and 1,000 times as massive as Sagittarius A* (Sgr A*), the supermassive black hole at the heart of the Milky Way that sits just 26,000 light-years from Earth.

Both of these discoveries are not expected under current models of cosmic evolution, galaxy growth, or supermassive black hole formation. All of these theories suggest galaxies and supermassive black holes grow in lockstep — but this growth takes billions of years.

"We have confirmed that these appear to be packed with ancient stars — hundreds of millions of years old — in a universe that is only [600 million to 800 million years] old. Remarkably, these objects hold the record for the earliest signatures of old starlight," research leader Bingjie Wang, a postdoctoral scholar at Penn State, said in the statement. "It was totally unexpected to find old stars in a very young universe. The standard models of cosmology and galaxy formation have been incredibly successful, yet these luminous objects do not quite fit comfortably into those theories."

The team first spotted the little red dots while using the JWST back in July. At the time, the researchers immediately suspected the objects were actually galaxies that existed roughly 13.5 billion years ago.

Deeper investigation of these objects' light spectra confirmed these as galaxies that lived during the very dawn of time and also revealed that "overgrown" supermassive black holes and impossibly "old" stars were powering the red dots' impressive light output.

The team isn't yet certain how much of the light from the little red dots comes from each of these sources. That means these galaxies are either unexpectedly old and more massive than the Milky Way, having formed far earlier than models predict, or have normal amounts of mass yet overly massive black holes somehow — voids that are vastly more massive than a similar galaxy would have during the current epoch of the cosmos.

"Distinguishing between light from material falling into a black hole and light emitted from stars in these tiny, distant objects is challenging," Wang said. "That inability to tell the difference in the current dataset leaves ample room for interpretation of these intriguing objects."

That's no ordinary supermassive black hole!

Of course, all black holes have light-trapping boundaries called "event horizons," meaning that, however much light they contribute to the little red dots, it must come from the material that surrounds them rather than from within.

The tremendous gravitational influence of the black holes generates turbulent conditions in this material, which also feeds the black hole over time, heating it and causing it to glow brightly. Regions powered by supermassive black holes in this way are called "quasars," and the regions of their galaxies they sit in are known as "active galactic nuclei (AGNs)."

These newly found, "red dot" black hole regions could be different from other quasars, even those the JWST has already seen in the early universe. For instance, the red dot black holes seem to produce far more ultraviolet light than expected. Still, the most shocking thing about these supermassive black holes remains just how massive they seem.

"Normally, supermassive black holes are paired with galaxies," Leja said. "They grow up together and go through all their major life experiences together. But here, we have a fully formed adult black hole living inside of what should be a baby galaxy. 

"That doesn't really make sense because these things should grow together, or at least that’s what we thought."

The red dot galaxies themselves are also surprising. They seem to be much smaller than other galaxies despite having almost as many stars. That means the red dot galaxies seem to consist of between 10 billion and 1 trillion stars crammed into a galaxy a few hundred light-years across with a volume 1,000 times smaller than the Milky Way.

To put that into context, if the Milky Way were reduced to the size of one of these red dot galaxies, then the closest star to the sun (Proxima Centauri, which is 4.2 light-years away) would be within the solar system. Additionally, the distance between the Earth and the Milky Way's supermassive black hole, Sgr A*, would be reduced from 26,000 light-years to just 26 light-years. That would see it and its surroundings appearing in the night sky over Earth.

"These early galaxies would be so dense with stars — stars that must have formed in a way we've never seen, under conditions we would never expect during a period in which we’d never expect to see them," Leja said. "And for whatever reason, the universe stopped making objects like these after just a couple of billion years. They are unique to the early universe."

The team intends to follow up on its findings with more observations of these confusing little red dots to understand the dots' mysteries better. This will include obtaining deeper spectra by pointing the JWST at the red objects for prolonged periods of time to obtain emission spectra of light associated with various elements. This could help unravel the contributions of ancient stars and supermassive black holes in the galaxies.

"There's another way that we could have a breakthrough, and that's just [having] the right idea," Leja concluded. "We have all these puzzle pieces, and they only fit if we ignore the fact that some of them are breaking. This problem is amenable to a stroke of genius that has so far eluded us, all of our collaborators, and the entire scientific community.

"Honestly, it's thrilling to have so much of this mystery left to figure out."

The team's research was published on June 26 in the journal Astrophysical Journal Letters.

Originally posted on Space.com.

The case is the first human illness detected in Colorado in connection with an ongoing outbreak in cattle. It follows one human case in Texas and two in Michigan. The second case in Michigan caused mild respiratory symptoms, such as coughing, but the other three cases — including the most recent in Colorado — have only included eye symptoms, such as redness.

The culprit behind these infections is a bird flu virus called influenza A(H5N1). This subtype of flu was first spotted among U.S. dairy cows in March. Since then, dozens of herds across the country have tested positive for the virus.

Recent research suggests that, when it infects cows, the virus can end up in the animals' milk and remain infectious in unpasteurized milk for at least an hour after harvest. This poses a significant risk to dairy workers, who may come into contact with contaminated milk through contact with cows or with milking equipment. The pasteurized milk supply, on the other hand, is safe because the pasteurization process inactivates any viruses in the milk. 

Related: 'Playing Russian roulette with your health': Officials warn that social media trend of consuming raw milk will not protect you from bird flu

Because of the risk posed by raw milk, the CDC recommends that dairy workers wear personal protective equipment.

In the recent Colorado case, the individual was being monitored because they'd been exposed to H5N1-infected cattle at work. Clinical samples from the person were sent to the CDC, who confirmed an infection with an influenza A(H5) virus. The agency is continuing to analyze the sample to confirm that the virus is in fact H5N1.

The infected person was treated with a common drug for seasonal flu, called oseltamivir; Tamiflu is a well-known, brand-name version of the drug. The person recovered following this treatment. 

All three people previously infected in the outbreak also recovered from their mild infections. In the past, though, H5N1 has been known to sometimes kill people.

Overall, the Colorado case doesn't change the CDC's overall assessment of the unfolding outbreak.

"CDC has been watching influenza surveillance systems closely, particularly in affected states, and there has been no sign of unusual influenza activity in people," the agency reported. "Based on the information available at this time, this infection does not change CDC's current H5N1 bird flu human health risk assessment for the U.S. general public, which the agency considers to be low."

Nonetheless, the CDC will continue to monitor for unusual flu activity. There's a possibility that, in time, H5N1 could pick up mutations that enable the virus to spread easily from person to person — something it hasn't yet been able to do. Such a change in the virus' genetics would be concerning because the pathogen could then potentially spark a widespread outbreak, or even a pandemic.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

A Night with the Valkyries — Jose Miguel Picon Chimelis

In this image, a powerful geomagnetic storm creates a stunning display of multicolored hues across the night sky in Iceland.

"There was a prediction of a KP7 storm [a strong geomagnetic storm that can cause auroras and affect electrical power systems] and I was excited as to what I might see," photographer José Miguel Picón Chimelis said in a statement. 

He took the panoramic photo near Eystrahorn mountain, capturing a scene full of vibrant colors, which he described as "one of the most amazing that I have experienced in my nighttime photography outings."

Solar Pulsation — Wenlian Li

In this vibrant display of energy, photographer Wenlian Li captured an exploding sunspot spewing out glowing plasma from the sun's surface.

 Observations at night — Jakob Sahner 

In this shot from La Palma, one of the Canary Islands in the Atlantic Ocean, the immense Isaac Newton Telescope sits below ominous cosmic clouds from the Cygnus constellation.

"The Cygnus region with its bright and vibrant star-forming regions is one of my favorite parts of the night sky. You can see it in the top right of the image," photographer Jakob Sahner said in the statement.

Cygnus, which translates to "the swan" in Latin, is a northern constellation that sits above the Milky Way.

Related: The Milky Way will be visible without a telescope this summer. Here are the key nights to watch for.

 Arctic Dragon — Carina Letelier Baeza 

Carina Letelier Baeza captured the aurora borealis forming the shape of a dragon. Its tail descends into the horizon, and bright green hues take the shape of wings that tower over the rock pyramids of the Arctic Henge in Iceland.

 Serpentine — Paul Haworth 

Paul Haworth created this entrancing image of radial stars above the ruins of an old jetty and cracked mudflats at Snettisham beach in Norfolk, U.K.

"I named this image 'Serpentine' as I love the curved channel in the mudflat, mirroring the trailing stars, and the wonderful scaly texture of the mud cracks," Haworth said in the statement.

The Galaxy Devourer — ShaRa (Shared Remote Astrophotography) Team 

The interstellar clouds of CG 4 (Cometary Globule 4) form a monstrous shape as if ready to devour the cosmos, in this picture taken by a team of astrophotographers known as ShaRA (Shared Remote Astrophotography).

The peculiar formation of gas clouds and dust is classed as a "cometary globule" because of its comet-like shape, and it's often referred to as "God's Hand" because of its similarity to an arm stretching across the universe. 

Along with these names, a member of the astrophotography team noticed its resemblance to two famous fictional monsters.

"Is this the cosmic sandworm of Arrakis, from 'Dune,' or the terrifying Graboid from the film 'Tremors'?" ShaRa group member Alessandro Ravagnin said in the statement.

 The Blue Details of M45: The Pleiades — Sandor Biliczki 

In this image, Sándor Biliczki captured the beauty of the Pleiades constellation. 

Also known as Messier 45 or the Seven Sisters, the Pleiades consists of thousands of stars but is known for its seven brightest stars and is located 445 light-years from Earth, according to NASA.

Due to light pollution in Budapest, Biliczki traveled to  Spain to photograph the constellation.

"The Pleiades are a popular target among astrophotographers, but there are still many tiny details to be discovered," Biliczki said in the statement.

A Cosmic Firework: the Geminid Meteor Shower — Jakob Sahner 

This panorama captures the Geminid meteor shower in front of the entire winter Milky Way in the night sky over La Palma.

Jakob Sahner said he could see three meteors per minute within his field of view during the peak of the shower.

 The Scream of a Dying Star — Yann Sainty 

Yann Sainty captured the Cygnus supernova in this haunting image, named "The Scream of a Dying Star."

The name is a reference to 'The Scream,' the famous painting by Edvard Munch, symbolising the scream that continues to echo through space after the star’s death, according to the image caption.

Sainty took advantage of the lack of light pollution and a long exposure time to capture rare details of the Cygnus Loop, such as the outer layers of the supernova remnant.

Martian Dementors  —  Leonardo Di Maggio

Leonardo Di Maggio created this eerie, abstract landscape image using a photo taken from NASA's Mars Reconnaissance Orbiter (MRO) — a spacecraft on a mission to find evidence of water on Mars. 

The striking surface feature, named Aganippe Fossa, is a graben — a "ditch-like groove with steep walls on either side," according to the European Space Agency (ESA). Astronomers first spotted it as early as 1930 but only officially named it in 1976, according to the U.S. Geological Survey.

The graben is incomplete, with various breaks in the groove from end to end, but it is considered to be a single structure that stretches around 375 miles (600 kilometers). That is longer than the Grand Canyon, which is 277 miles (446 km) from one end to the other, according to the National Park Service. However, the structure is still significantly shorter than Mars' Valles Marineris — the largest canyon in the solar system, which runs for more than 2,500 miles (4,000 km) along the Red Planet's equator.

ESA's Mars Express orbiter captured the newly released photos on December 13, 2023. The satellite has been circling the Red Planet on an elliptical orbit for more than two decades. 

One of the most interesting things in the photo is the surrounding landscape, which varies on either side of the giant crack. To the left, the ground appears to be very uneven and contains several mounds, grooves and ridges. But to the right, the land looks smooth and is painted with "zebra-like" rocky stripes, ESA representatives said. 

This stark difference was likely caused by historic wind erosion to the right of the graben, which wore down the planet's surface in that area. However, it is unclear why the rest of the surrounding landscape was unaffected.

Related: 15 Martian objects that aren't what they seem

Aganippe Fossa is located near the base of Arsia Mons, a 12-mile-tall (20 km) extinct volcano on Mars' Tharsis plateau. This region contains two other major volcanoes, Pavonis Mons and Ascraeus Mons, and together the three dead peaks form a near-perfect line perpendicular to the planet's equator. The trio is flanked by Olympus Mons, the tallest peak in the solar system, which lies just outside of Tharsis and stands over 16 miles (25 km) above the surface — around three times taller than Mount Everest.

The scar was likely caused by a large plume of magma that pooled underneath Arsia Mons long ago, pushing the planet's crust upward and tearing apart the surface, ESA representatives wrote. 

It is currently unclear how old Aganippe Fossa is, but NASA previously estimated that the volcano stopped erupting around 50 million years ago. However, scientists recently discovered evidence of a Martian volcanic eruption as recently as 50,000 years ago, hinting that volcanic activity on the Red Planet is not as ancient as we previously thought.

Similar grabens also exist in Noctis Labyrinthus (meaning "Labyrinth of Night" in Latin) — a massive canyon around the size of Italy, which is situated between Tharsis and Valles Marineris.

The area surrounding Tharsis is one of the most geologically interesting regions on the Red Planet. The region also caught the attention of researchers earlier this year after the discoveries of a giant volcano hidden next to Noctis Labyrinthus and more than 150,000 tons of frozen water across the peaks of the three Tharsis volcanoes.  

Waiting for Amazon Prime Day to save some bucks on a new rowing machine? There's no need. Right now, retailers far and wide are stepping up their game against Amazon with some truly unmissable deals. Like Echelon, for example.

This compact, foldable rowing machine is one of our all-time favorites, which is why we included it in our roundup of the best rowing machines as the best option for small spaces. During our Echelon Smart Rower review, it impressed us with its sleek design, sturdiness and smooth, near-silent magnetic resistance. We enjoyed the engaging fitness classes available on the Echelon Fit app, too. True, you have to watch them on your own device, and they require a monthly subscription — but it is money well spent. Especially when you can knock a hefty $400 off the price of the rower in the first place.

Key features: 32 levels of magnetic resistance, foldable design, Bluetooth connectivity and a device holder.

Price history: For the most part of this year, the price of the Echelon Smart Rower at Amazon fluctuated between $700 and $800. The last time we saw it dip below $600 was in late April when it stood at $523.99.  

Price comparison: The Echelon Smart Rower is currently discounted to $699.99 at both Amazon and Best Buy, while at Walmart it stands at $685. 

Reviews consensus: The online reviews for the Echelon Smart Rowers are overwhelmingly positive, with most rating it at 4 or 4.5 out of 5 stars. The rowing machine is universally praised for its near-silent operation, sturdiness, space-savvy design and ease of use. Many reviewers, however, complain about its high price given the lack of an integrated screen, and that the Echelon Fit app requires a monthly subscription.      

Buy it if: You are looking for a well-made, thoughtfully designed rowing machine that offers engaging workouts and does not take up much space. The Echelon Smart Rower is a quiet, sturdy and good-looking piece of kit. 

Don't buy it if: You want a built-in touchscreen and other frills typical of more premium rowing machines. 

More than 1 billion people each year will have a migraine, and about one-quarter of those migraines will be accompanied by an aura. These sensory symptoms can include seeing lights and hearing sounds that aren't there or feeling tingling or numbness. 

Scientists have known that these auras are associated with "cortical spreading depression," waves of abnormal activity that wash over the brain and temporarily inactivate certain neurons. The waves are thought to somehow trip pain-detecting nerves outside the brain, in part by releasing chemicals into the cerebrospinal fluid (CSF), a substance that surrounds and cushions the organ. 

Exactly how the chemicals reached the nerves was a mystery. Now, scientists have uncovered a route by which some molecules can escape the brain's protective barrier. 

Related: Migraines and blood sugar issues share common genetic risk factors

In a study published Thursday (July 4) in the journal Science, researchers examined the route CSF takes to exit the brain by zooming in on a cluster of neurons called the trigeminal ganglion. This bundle of cells transmits signals from the nerves of the face and jaw to the brain, plugging in around the brainstem. 

The scientists discovered that this nerve bundle also provides a route for CSF and the molecules within it to reach the world beyond the brain.

They learned this by using genetically engineered mice whose neurons make a protein that glows in the presence of calcium. Calcium is a key element that brain cells use to send electrical signals. While observing the trigeminal ganglion, the researchers would inject a tracer into the mouse's brain to track the flow of its CSF. They also introduced a substance that allows calcium to flow into neurons, activating them.

The experiment revealed that CSF appeared in the trigeminal ganglion about four minutes after injection, followed by a sharp increase in calcium-driven activity. This provided direct evidence that CSF can carry molecules outside the brain via this channel. 

The fluid likely makes contact with the ganglion near the brainstem. There, the ganglion lacks the tightly fused outer barrier that can be seen elsewhere along its length, the team found.

To connect the dots to migraine, the team looked at the effects of cortical spreading depression. They demonstrated that it can increase the flow of CSF in the affected area, carrying more proteins and other molecules to the trigeminal ganglion than it normally would. Many of those proteins were drivers of pain and inflammation.

"We found that during aura, proteins that can activate and sensitize sensory nerves are released to the CSF and transported to the trigeminal ganglion, where they activate pain-mediating sensory nerves," study author Martin Kaag Rasmussen, a postdoctoral scholar at the University of Copenhagen, told Live Science in an email. 

"This is what drives the migraine headache, and it is what links the aura phase to the headache," he said.

Related: Does caffeine help or cause headaches?

Of the 12 proteins found to activate pain-sensing nerves, only one — calcitonin gene-related peptide (CGRP) — is a current target for migraine therapies. Medications that block CGRP function relieve migraine symptoms in about half of patients, but that still leaves millions of people without effective treatment. 

Rasmussen is optimistic that the additional molecules uncovered in the study could offer new treatment options. "I believe that, when patients do not respond well to currently available therapies, it is because we have not identified what molecule is responsible for their headache," he said. 

"I find it really exciting because it's a new pathway for delivery of molecules from the brain to peripheral ganglia," Andrew Russo, a professor of neurology at the University of Iowa who was not involved in the study, told Live Science. That could have relevance well beyond migraines, he said.

The caveat, however, is that all of the group's experiments were performed in mice. In comparison to the human brain, "the mouse brain is very smooth," Russo said. Humans' brain tissue has more folds so the abnormal waves tied to migraine can't travel as efficiently. That might affect how fast CSF flows out of the brain and whether or not it triggers the pain-sensing nerves, Russo noted.

The next step will be to answer that question by examining the same processes in humans or more human-like animal models. The researchers also want to take a closer look at the new pain-triggering proteins they identified, both in migraines and other headache disorders. This could potentially lead to new diagnostic tests and treatments for a variety of patients.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

The findings support current guidelines on the use of this class of drugs, which caution against using benzodiazepines for extended periods of time. 

Benzodiazepines, also known as "benzos," are sedative drugs commonly prescribed to treat numerous conditions, including insomnia, anxiety and seizure disorders. They work by slowing down the activity of the central nervous system, meaning the brain and spinal cord. This can relax a person's mood, relieve muscle spasms and also cause people to feel sleepy. 

These drugs, which include Xanax, are highly addictive and previous research has shown that long-term use comes with a risk of memory and movement issues. As such, the U.S. Food and Drug Administration (FDA) recommends that benzodiazepines are prescribed at the lowest dose possible and for the minimum time required to achieve the desired clinical effects — usually around two to four weeks. 

Despite these concerns, evidence suggests that between 6% and 15% of patients prescribed benzodiazepines use the drugs for more than six months.

In the new study, published Monday (July 1) in the journal BMC Medicine, researchers have revealed another reason to be cautious about prolonged benzo use: it use may speed up the natural age-related dwindling of two regions of the brain involved in memory and mood regulation, called the hippocampus and the amygdala. 

Related: Scientists debunk myth that human brains are 'underdeveloped' at birth

The researchers reviewed the medical records of 5,443 adults in the Netherlands who initially had no reported cognitive impairment. The scientists scanned the medical records to determine if, and how many, benzodiazepines the individuals had taken daily between 1991 and 2008. On average, people took their prescribed daily dose 37 times within this time frame. 

The team found that around 50% of study participants had used benzodiazepines at some point up to 2008, and approximately 13% of the overall group went on to be diagnosed with dementia by 2020. Notably, the people who took benzodiazepines were no more likely to develop dementia than those who'd never taken them, regardless of how much they took and for how long, the team found. 

These findings contradict two prior analyses conducted by different groups of researchers. These past analyses summed up the findings of numerous studies on the topic — however, those studies differed in how they were conducted, and their differences might have muddied the results, the team said. 

Although the new study didn't find that benzos boosted dementia risk, it did uncover physical brain changes tied to the drugs. The researchers looked at brain scans that were taken at least once from roughly 4,800 of the 5,443 participants. These scans showed changes in the volume of different structures in the brain over time. 

Based on these scans, the researchers concluded that benzodiazepine use was associated with an accelerated reduction in the volume of the hippocampus and amygdala. In other words, these structures shrunk faster in the group who took benzos, compared to the group who had not used the drugs. 

In addition to these changes in overall brain volume, the team uncovered differences in white matter, the brain tissue that contains the passageways that transmit signals between neurons. Participants who took benzodiazepines specifically for sleep issues — known as sedative-hypnotics — showed a faster reduction in white matter volume than those who took benzodiazepines for anxiety, called anxiolytics.

"Our results underline guidelines that say that you shouldn't take benzodiazepines for a very long period of time," Ilse vom Hofe, co-senior study author and a doctoral candidate at Erasmus University Medical Center in The Netherlands, told Live Science. "Also, I think it motivates health clinicians to look into other therapies to address the problems that people are experiencing, instead of just riding out the benzodiazepines."

The team acknowledged several limitations of the new study. For instance, they only looked at people who started out "cognitively healthy," so it's unclear whether benzos might have more or less profound impacts in people with cognitive impairment. Participants were also mainly white, which may limit how well the findings apply to additional groups. 

As they stand, though, the findings support the need for more research investigating the impact of long-term benzodiazepine use on brain health, the team said. 

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

The crystal-clear waters of Shark Bay are home to the world's largest plant: a seagrass meadow spanning 77 square miles (200 square kilometers) and stretching 112 miles (180 kilometers) from end to end. The shoots that make up the massive meadow all originate from one stem, which researchers estimate is at least 4,500 years old.

Researchers analyzed the genetic makeup of the seagrass at Shark Bay for the first time in 2022. They discovered that almost all the Poseidon's ribbon weed (Posidonia australis) — which grows in a network of meadows inside the bay — was genetically identical, indicating that the weeds belonged to one plant. Unlike other types of seagrass, which reproduce sexually, this meadow appeared to be continually cloning itself through an underground stem called a rhizome.

Related: 2 plants randomly mated up to 1 million years ago to give rise to one of the world's most popular drinks

On the sandy seafloor, the self-cloning seagrass meadow forms clumps of grass that look like separate organisms, but underground, the shoots are connected to form "the largest clone in any environment on Earth," the researchers wrote in the study. 

This means the Shark Bay seagrass dwarfs the previous record-holder: The second-largest clone on record is a 9-mile-long (15 km) meadow of Posidonia oceanica seagrass in the western Mediterranean Sea. 

The meadow at Shark Bay is expanding through a process known as "horizontal rhizome extension," in which the plant grows stems that extend horizontally beneath the seafloor. These stems then grow vertical stems that develop shoots and leaves, which break through the sand to form seagrass. Based on the size and age of the meadow, researchers estimate it is expanding by around 6 to 14 inches (15 to 36 centimeters) per year — which is fairly quick compared with other self-cloning seagrass meadows, according to the study.

The meadow has remained relatively undisturbed for millennia, which has enabled it to reach colossal proportions. The clone could continue its creeping expansion for as long as it is left untouched, making it practically immortal, Elizabeth Sinclair, an evolutionary biologist at the University of Western Australia, previously told Live Science. 

What it is: A cerulean statuette of a hippopotamus molded in faience, a glazed ceramic material made partly out of ground quartz. The artifact is decorated with drawings of lotus flowers, which grow in marshes and symbolize regeneration and rebirth.

Where it was found: Inside a shaft associated with a tomb chapel in Meir, an ancient Egyptian cemetery located outside the city of Asyut. 

When it was made: Circa 1961 to 1878 B.C.

What it tells us about the past: Ancient Egyptians feared hippos (Hippopotamus amphibius), viewing them as dangerous and aggressive animals, especially when provoked, according to The Metropolitan Museum of Art in New York City. Thanks to these mostly herbivorous mammals' insatiable appetites, they often wreaked havoc on farmers' fields. In fact, one papyrus refers to a particularly bad harvest in which "the worm took half and the hippopotamus ate the rest."

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Hippo hunts were a common sport among the ancient Egyptians, who would use harpoons to snare the large beasts, which were associated with chaos. By 3000 B.C., depictions of kings successfully battling hippos became commonplace, as it was a way to show rulers overcoming chaos. However, due to overhunting, the last wild hippos disappeared from Egypt by the early 19th century, according to The Met.

This statuette, which measures about 8 inches by 5 inches (20 centimeters by 11 cm), is one of many examples of hippo sculptures crafted by ancient Egyptians. When it was discovered, three of its legs were missing and were likely broken on purpose to prevent it from doing harm in the afterlife, according to The Met.

In 1931, the artifact was dubbed "William" after the British humor magazine Punch ran a cartoon about the hippo.