One of the planet’s deadliest viruses makes an annual pass through the United States with little fanfare. It rarely generates flashy headlines or news footage of health workers in hazmat suits. There’s no sudden panic when a sick person shows up coughing and feverish in an emergency room. Yet before next spring, this season’s lethal germ will probably have infected millions of Americans, killing tens of thousands. Still, it’s often referred to as just the flu.

The influenza virus seems so normal to most Americans that only about half of us will heed those “time for your flu shot” banners that pop up at pharmacies and worksites every autumn. Those annual shots remain the best means of protection, but they must be manufactured months before flu season starts, based on a best educated guess of what strains of the virus will be circulating. That means even in a successful year, vaccine performance may not be impressive. During the 2015–2016 season, only about half of those immunized were protected, according to a study in the Aug. 10 New England Journal of Medicine. Some years’ vaccines are duds: For the 2014–2015 season, the vaccine protected only 19 percent of people who received it, based on U.S. Centers for Disease Control and Prevention data.
Scientists have long worked to develop a flu shot that works better and lasts longer. But, unlike the very stable measles virus, influenza is a moving target. While only a few strains of flu virus circulate worldwide in a typical year, dozens more may exist. Each one is highly likely to mutate from year to year, with just enough shape-shifting to be unrecognizable to the body’s defenses.

Now, after years of searching, scientists believe they have better strategies to attack the parts of the virus that stay the same from year to year, offering the hope of protection across multiple seasons. The vaccines being developed in laboratories around the world “offer more promise than we’ve ever had,” says Walter Orenstein, associate director of the Emory Vaccine Center in Atlanta. And there are new creative approaches: One research group is trying to make a kind of super shot by anticipating every possible mutation a circulating virus might undergo.

“I’m optimistic we are going to get to a vaccine,” says Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, or NIAID, in Bethesda, Md. Then, you may need to heed those “time for your flu shot” messages only once.
Researchers often describe the flu virus as looking like a ball with lollipops sticking out. Tucked inside the ball is RNA, which the virus needs to make copies of itself. The lollipops on the outside are proteins: hemagglutinin and neuraminidase. There are 18 different kinds of hemagglutinin and 11 kinds of neuraminidase. Each kind of flu virus is named for its particular combination of these proteins; the current forms circulating around the world are H1N1 and H3N2. Hemagglutinin attaches to human cells to launch an infection; neuraminidase is more important for spreading the virus once infection has occurred.

Flu viruses involved in human epidemics are divided into types A and B, and A viruses are sliced even further into group 1 and group 2. Influenza A, the most troublesome for vaccine scientists, travels the world among birds, pigs and humans. The bird and pig versions don’t easily infect people, but the virus is constantly mutating and even swapping genes with other influenza viruses it meets along the way. Sometimes these genetic changes create a version that allows a bird or pig flu to move directly into humans. In 2013, one called H7N9 moved into people in China (SN Online: 3/11/15). The virus has since infected more than 1,500 people. Mostly, though, the genetic changes are more subtle, with just enough alterations to evade the human immune system.
Like kids with a sweet tooth, the immune system gets most excited about the top part of the hemagglutinin lollipop, and makes antibodies against it. The top is, after all, the first thing the immune system notices once the virus slips inside the nose, mouth and lungs. Every year, genetic mutations in the virus slightly change the chemical flavor of the lollipop, making it more sweet or sour than last season’s — just different enough so the immune system doesn’t recognize it. That’s why most years there’s a new flu shot.

Sometimes, in the gene shuffling with viruses in birds and pigs, the changes are so great that the flavor changes completely. Those are pandemic years, when there is so little residual immunity that a large portion of the global population falls ill from the new virus. The devastating 1918 flu, which killed an estimated 50 million people globally, was caused by such a drastic genetic shift (SN Online: 4/29/14). The most recent pandemic occurred in 2009, with the appearance of the “swine flu,” so named because the virus was first found in pigs. By one analysis, it caused between 148,000 and 249,000 deaths around the world.

Attack the stem
The 2009 disaster helped provide a blueprint for some of the latest experimental vaccines. Researchers noticed that when people with swine flu developed antibodies to the virus, those antibodies did something odd: They favored the hemagglutinin stem — the stick of the lollipop. And, more important, they appeared to react broadly against two kinds of flu virus. Scientists had known that the hemagglutinin stem, or stalk, isn’t as apt to change as the lollipop top, which theoretically makes the stem a good target for a universal vaccine. But in a usual flu season, the human body isn’t inclined to make infection-fighting antibodies against the stem.

“Unfortunately, the immune system preferentially recognizes the head, and we don’t know why it does that,” says Adrian McDermott, an immunologist at NIAID. So after infection, the biggest share of antibodies flocks to the hemagglutinin head. (Neuraminidase, the bigger player in disease after infection, is a target for influenza treatments but not a major focus for vaccine development.)

But in a study reported in the Journal of Experimental Medicine in 2011, a team of scientists from Emory and elsewhere found that antibodies to the so-called swine flu behaved unexpectedly. “If you have a head that the immune system hasn’t seen, you potentially redirect to a stalk response,” McDermott says. “That was an aha! moment.”
Researchers investigated further. For one study in 2012 in Frontiers in Immunology, scientists from Canada injected these stem-recognizing antibodies into mice to see if the mice were shielded from a different strain of flu. Not only were the mice protected from lethal doses of flu virus, but the protection was also in large part due to the absence of familiar antibodies against the head, the researchers found. Without the distraction of a head it recognized, the immune system seemed to rally against the stem.

Then came the what ifs: What if a vaccine produced just antibodies to the stem? Would that be enough protection? For the last few years, McDermott and others have been trying to develop vaccines made of “headless stalks” — just the sticks of the lollipops. With no head in place to hoard the immune response, the vaccine might coax the body to make enough stem-focused antibodies to protect against flu, the researchers hoped, regardless of the seasonal mutations occurring at the top.

Several groups soon found that headless stalks are difficult to make. Without the top to stabilize it, the molecular assembly tended to break apart. Two teams working independently reported in 2015 their success in keeping the stalk in one piece. NIAID scientists and their partners held the stalks together by anchoring them to the protein ferritin, which can assemble itself into nanoparticles. In a study in Nature Medicine, the team reported that vaccinated mice and ferrets appeared to be protected from dying of the H5N1 bird flu after receiving the vaccine, even when they developed symptoms. Unvaccinated mice and ferrets died.

The second team, from the Janssen Center of Excellence for Immunoprophylaxis in Leiden, the Netherlands, and the Scripps Research Institute in La Jolla, Calif., glued the stalk together by creating a series of genetic mutations at its top. In Science, the researchers reported that the vaccine reduced the symptoms of flu in vaccinated monkeys.

“We realized that the stem has much less variability than the head, and then we developed the capability to use it for a possible vaccine,” says Fauci, commenting on both efforts. “These were two important things that came together.”

Despite progress, these stalk-focused vaccines haven’t yet been put to human tests that would show whether they could protect broadly against many mutations of flu circulating annually, which is the ultimate test. And some stalk-directed antibodies might be better than others. In July in Science Immunology, McDermott and colleagues reported that the stalk antibodies against group 2 of the A viruses appear to be more broadly effective than those against group 1 viruses.

Other researchers have stabilized the stalk by attaching a new hemagglutinin head — a lollipop flavor that the human immune system has never tasted. In this case, researchers from the Icahn School of Medicine at Mount Sinai in New York City took tops from two flu strains that circulate only in birds, and connected each one to a human hemagglutinin stalk. This experimental vaccine consists of two doses. The first dose prompts the immune system to make antibodies against the stalk with the first top, and a second dose produces a second round of antibodies against the stalk with the second top. The idea is that the abundance of stem-focused antibodies — amplified from the two shots of vaccine — will come to the rescue during a natural infection from a virus that possesses a third, totally different head.
“The human immune system will try to find something it has seen before,” says Peter Palese, chairman of microbiology at Mount Sinai. In theory, the only antibodies in play will be the ones responding to the parts of the stalk that the immune system recognizes, known as the “conserved domains.”

“The $64,000 question,” according to Palese: “Will the immune response to these conserved domains be enough to elicit a broad immune system reaction?”

In 2016, Palese and colleagues described a test of the vaccine in the Journal of Virology. Six ferrets given the two doses were housed with six ferrets infected with H1N1 flu. Within 10 days, the vaccinated animals had become infected but had no symptoms or signs of being able to easily spread virus to others. A report in June in the same journal described tests of the vaccine in mice against influenza B viruses; the animals were protected from normally lethal doses of flu.

What’s not known is whether the stem-focused antibodies are enough to protect people from all virus variants. The vaccine from the Mount Sinai researchers is entering the first human safety trials with drugmaker GlaxoSmithKline.

Unhide and seek
Another approach incorporates proteins that don’t tend to mutate like the hemagglutinin head but are hidden from the immune system under normal circumstances. When these proteins are made visible to types of white blood cells called T cells, the immune system wakes up. T cells don’t make antibodies, but certain T cells hold on to a memory of foreign molecules seen before. When these pre-programmed T cells recognize an infection, they destroy the invader.

This work began in the 1990s, when researchers at the Weizmann Institute of Science in Rehovot, Israel, set out to find parts of the virus that remain unchanged from year to year. The team identified stable regions in three proteins — hemagglutinin, plus one from the virus membrane and one from the virus core. In 2003, a company called BiondVax Pharmaceuticals formed to develop and test, in humans, an experimental vaccine that takes these proteins and packages them in a way that the immune system can recognize them.

So far, almost 700 volunteers have participated in six small trials, all of which showed signs of a lasting immune response among most volunteers. Writing in February in Vaccine, the researchers reported that the stored serum of elderly volunteers who received the vaccine in 2011 showed an immune response to new strains of flu that were circulating three years later. The company is starting larger trials to see if the vaccine can actually protect people from getting sick.
Out of many, one
Other experimental vaccines take a different approach. Rather than relying on precision to hit a narrow target, microbiologist Ted Ross and colleagues at the University of Georgia in Athens are attempting to cast a wide net. The researchers are taking hemagglutinin mutations from every flu strain that has ever circulated, dumping them into a kind of scientific blender and attaching them to particles that can form the basis of a vaccine.

“The question we asked is, how can we make a vaccine against a strain we don’t even know exists?” Ross says. The technique he uses is called COBRA for computationally optimized broadly reactive antigen. A computer compiles all seemingly possible genetic iterations of a particular flu type — in this case H1N1 — and then bundles them into one molecule. It’s kind of like taking every novel in your local library and combining them into one giant book.

Last year in the Journal of Virology, Ross and colleagues described a COBRA-derived vaccine that represented almost all forms of H1N1 that have been around for the last 100 years. The vaccine protected mice against infection from strains of H1N1 that the mice had never been exposed to. “We took a bunch of different hemagglutinins and mixed them into one hemagglutinin molecule,” Ross says. “It protected against any strain of H1N1 we could throw at it.”

The study caught the attention of vaccine maker Sanofi Pasteur, which plans to test the vaccine in clinical trials. Ross’ lab is now using the same strategy to develop a vaccine against H3N2 strains, the other dominant kind of flu circulating around the world. Same approach, different library.

Meanwhile, the virus isn’t waiting around. Based on the heavy flu season in the Southern Hemisphere, some experts are predicting this year’s epidemic could be severe. It’s still too early to know whether the current vaccine will provide good protection, but someday, a super shot may remove the guesswork altogether.

Campfire legends of massive, shaggy bipeds called yetis are grounded in a less mysterious truth: bears.

Eight samples of remains such as fur, bones and teeth purportedly from mountain-dwelling yetis actually come from three different kinds of bears that live in the Himalayas, researchers report November 29 in the Proceedings of the Royal Society B. A ninth sample turned out to come from a dog.

Previous analyses of smaller fragments of “yeti” DNA yielded controversial results. The new study looks at bigger chunks of DNA, analyzing the complete mitochondrial genomes from alleged yetis and comparing them with the mitochondrial genomes of various bears, including polar bears and Tibetan brown bears.
The results also give new insight into the genetic relationships between the different bears that call the Tibetan Plateau home, which could guide efforts to protect these rare subspecies. During a period of glaciation about 660,000 years ago, Himalayan brown bears were one of the first groups to branch off and become distinct from other brown bears, the data suggest.

Tibetan brown bears, on the other hand, share a more recent common ancestor with their relatives in Eurasia and North America. They might have migrated to the area around 340,000 years ago, but were probably kept geographically isolated from Himalayan brown bears by the rugged mountain terrain.

COLLEGE PARK, Md. — Campus life typically challenges students with new opportunities for learning, discovery — and intimacy with germs. Lots of germs.

That makes dormitories and their residents an ideal natural experiment to trace the germs’ paths. “You pack a bunch of college kids into a very small environment … we’re not known as being the cleanliest of people,” says sophomore Parker Kleb at the University of Maryland in College Park. Kleb is a research assistant for an ongoing study tracking the spread of respiratory viruses through a student population. The study’s goal is to better understand how these viruses move around, in order to help keep illness at bay — all the more pressing, as the current flu season is on track to be among the worst recorded in the United States.
Called “C.A.T.C.H. the Virus,” which stands for Characterizing and Tracking College Health, the study traces the trajectory of viral infections using blood samples, nasal swabs and breath samples from ailing freshmen and their closest contacts. (Tagline: It’s snot your average research study.)

Donald Milton, an environmental and occupational health physician-scientist, heads the project. On a recent day, he described the study to a classroom of freshmen he hopes to recruit. He ticked off questions this research seeks to answer: What is it that makes people susceptible to getting sick? What makes them contagious? And how do they transmit a virus to others? “Maybe your house, your room has something to do with whether you’re at risk of getting infected,” Milton said.

He had a receptive audience: members of the College Park Scholars’ Global Public Health program. Infection control is right up their alley. “How sick do we have to be?” one student asked. It’s the culprit that matters, she’s told. The study covers acute respiratory infections due to influenza viruses, adenoviruses, coronaviruses or respiratory syncytial virus, known as RSV.

Of most interest, however, is influenza. “Flu is important to everybody,” says Milton. Influenza is thought to spread among humans three ways — touch; coughing and sneezing, which launches droplets containing virus from the lungs onto surfaces; and aerosols, smaller droplets suspended in the air that could be inhaled (SN: 6/29/13, p. 9).
How much each of these modes of transmission contributes to the spread of viruses is a point of fierce debate, Milton says. And that makes infection control difficult, especially in hospitals. “If we don’t understand how [viruses] are transmitted, it’s hard to come up with policies that are really going to work.”
Milton and his colleagues recently reported that people with the flu can shed infectious virus particles just by breathing. Of 134 fine-aerosol samples taken when patients were breathing normally, 52 contained infectious influenza virus — or 39 percent, according to the study, published online January 18 in the Proceedings of the National Academy of Sciences . Those fine-aerosol particles of respiratory tract fluid are 5 microns in diameter or less, small enough to stay suspended in the air and potentially contribute to airborne transmission of the flu, the researchers say.
“This could mean that just having good cough and sneeze etiquette — sneezing or coughing into tissues — may not be enough to limit the spread of influenza,” says virologist Andrew Pekosz at Johns Hopkins University, who was not involved with the study. “Just sitting in your office and breathing could fill the air with infectious influenza.”

The C.A.T.C.H. study aims to find out if what’s in the air is catching. In two University of Maryland dorms, carbon dioxide sensors measure how much of the air comes from people’s exhalations. In addition, laboratory tests measure how much virus sick students are shedding into the air. To get those samples, students sit in a ticket booth‒sized contraption called the Gesundheit-II and breathe into a giant cone. These data can help researchers estimate students’ airborne exposure to viruses, Milton says.

Another key dataset comes from DNA testing of the viruses infecting the students. “The virus mutates reasonably fast,” Milton says, so the more people it’s moved through, the more changes it will have. By combining this molecular chain of transmission with the social chain of transmission, the researchers will try to “establish who infected whom, and where, and how,” Milton says.

The goal is to enroll 130 students in C.A.T.C.H. It’s doubtful they’ll all get sick, but not that many students from this initial group are needed to start the ball rolling, says Jennifer German, a virologist and C.A.T.C.H. student engagement coordinator. “For every index case that has an infection we’re interested in, we’re following four additional contacts,” she says. “And then if any of those contacts becomes sick, we’ll get their contacts and so on.”

The study began in November 2017. As of the end of January, German says, researchers have collected samples from five sick students, but only one was infected with a target virus, influenza. The researchers now are following three contacts from that case.

But timing and the size of the current flu outbreak may be on the researchers’ side. Kleb, the research assistant, says that students are still waiting for this season’s flu to sweep through the dorms. “Once one person gets sick, it goes around to everyone on the floor,” he says. “I’m very interested to see what happens in the next few weeks, and how the study will hopefully benefit.”

Nature may have a few things to teach tennis players about backspin.

The hairyflower wild petunia (Ruellia ciliatiflora) shoots seeds that spin up to 1,660 times per second, which helps them fly farther, researchers report March 7 in Journal of the Royal Society Interface. These seeds have the fastest known rotations of any plant or animal, the authors say. Plants that disperse seeds a greater distance are likely to be more successful in reproducing and spreading.
Glue that holds the flower’s podlike fruit together breaks down on contact with water, allowing the fruit to split explosively, launching millimeter-sized seeds. Little hooks inside the pod help fling these flattened discs at speeds of around 10 meters per second.

Using high-speed cameras that record 20,000 frames per second, the researchers analyzed the seeds’ flight. “Our first thought was: ‘Why doesn’t this throw like a Frisbee?’” says Dwight Whitaker, an applied physicist at Pomona College, in Claremont, Calif. Instead of spinning horizontally, most seeds spin counterclockwise vertically, like a bicycle wheel in reverse.

Whitaker and his colleagues calculated that backspin should help stabilize the seeds as they travel through the air, reducing drag. Experiments backed this up: Stable “spinners” had less drag on average than “floppers,” seeds that tumbled as they fell. Simulations predict that lower drag lets spinners travel 6.7 meters on average — more than twice as far on average as floppers.

Meet STEVE, a newfound type of aurora that drapes the sky with a mauve ribbon and bedazzling green bling.

This feature of the northern lights, recently photographed and named by citizen scientists in Canada, now has a scientific explanation. The streak of color, which appears to the south of the main aurora, may be a visible version of a typically invisible process involving drifting charged particles, or ions, physicist Elizabeth MacDonald and colleagues report March 14 in Science Advances.
Measurements from ground-based cameras and a satellite that passed when STEVE was in full swing show that the luminous band was associated with a strong flow of ions in the upper atmosphere, MacDonald, of NASA’s Goddard Space Flight Center in Greenbelt, Md., and colleagues conclude. But the researchers can’t yet say how a glow arises from this flow.

Part of a project called Aurorasaurus (SN Online: 4/3/15), the citizen scientists initially gave the phenomenon its moniker before its association with ion drift was known. MacDonald and colleagues kept the name, but gave it a backronym: “Strong Thermal Emission Velocity Enhancement.”

We’ll just stick with STEVE.

Tiny particles of plastic have been found everywhere — from the deepest place on the planet, the Mariana Trench, to the top of Mount Everest. And now more and more studies are finding that microplastics, defined as plastic pieces less than 5 millimeters across, are also in our bodies.

“What we are looking at is the biggest oil spill ever,” says Maria Westerbos, founder of the Plastic Soup Foundation, an Amsterdam-based nonprofit advocacy organization that works to reduce plastic pollution around the world. Nearly all plastics are made from fossil fuel sources. And microplastics are “everywhere,” she adds, “even in our bodies.”
In recent years, microplastics have been documented in all parts of the human lung, in maternal and fetal placental tissues, in human breast milk and in human blood. Microplastics scientist Heather Leslie, formerly of Vrije Universiteit Amsterdam, and colleagues found microplastics in blood samples from 17 of 22 healthy adult volunteers in the Netherlands. The finding, published last year in Environment International, confirms what many scientists have long suspected: These tiny bits can get absorbed into the human bloodstream.

“We went from expecting plastic particles to be absorbable and present in the human bloodstream to knowing that they are,” Leslie says.
The findings aren’t entirely surprising; plastics are all around us. Durable, versatile and cheap to manufacture, they are in our clothes, cosmetics, electronics, tires, packaging and so many more items of daily use. And the types of plastic materials on the market continues to increase. “There were around 3,000 [plastic materials] when I started researching microplastics over a decade ago,” Leslie says. “Now there are over 9,600. That’s a huge number, each with its own chemical makeup and potential toxicity.”

Though durable, plastics do degrade, by weathering from water, wind, sunlight or heat — as in ocean environments or in landfills — or by friction, in the case of car tires, which releases plastic particles along roadways during motion and braking.

In addition to studying microplastic particles, researchers are also trying to get a handle on nanoplastics, particles which are less than 1 micrometer in length. “The large plastic objects in the environment will break down into micro- and nanoplastics, constantly raising particle numbers,” says toxicologist Dick Vethaak of the Institute for Risk Assessment Sciences at Utrecht University in the Netherlands, who collaborated with Leslie on the study finding microplastics in human blood.

Nearly two decades ago, marine biologists began drawing attention to the accumulation of microplastics in the ocean and their potential to interfere with organism and ecosystem health (SN: 2/20/16, p. 20). But only in recent years have scientists started focusing on microplastics in people’s food and drinking water — as well as in indoor air.

Plastic particles are also intentionally added to cosmetics like lipstick, lip gloss and eye makeup to improve their feel and finish, and to personal care products, such as face scrubs, toothpastes and shower gels, for the cleansing and exfoliating properties. When washed off, these microplastics enter the sewage system. They can end up in the sewage sludge from wastewater treatment plants, which is used to fertilize agricultural lands, or even in treated water released into waterways.

What if any damage microplastics may do when they get into our bodies is not clear, but a growing community of researchers investigating these questions thinks there is reason for concern. Inhaled particles might irritate and damage the lungs, akin to the damage caused by other particulate matter. And although the composition of plastic particles varies, some contain chemicals that are known to interfere with the body’s hormones.

Currently there are huge knowledge gaps in our understanding of how these particles are processed by the human body.

How do microplastics get into our bodies?
Research points to two main entry routes into the human body: We swallow them and we breathe them in.

Evidence is growing that our food and water is contaminated with microplastics. A study in Italy, reported in 2020, found microplastics in everyday fruits and vegetables. Wheat and lettuce plants have been observed taking up microplastic particles in the lab; uptake from soil containing the particles is probably how they get into our produce in the first place.

Sewage sludge can contain microplastics not only from personal care products, but also from washing machines. One study looking at sludge from a wastewater treatment plant in southwest England found that if all the treated sludge produced there were used to fertilize soils, a volume of microplastic particles equivalent to what is found in more than 20,000 plastic credit cards could potentially be released into the environment each month.

On top of that, fertilizers are coated with plastic for controlled release, plastic mulch film is used as a protective layer for crops and water containing microplastics is used for irrigation, says Sophie Vonk, a researcher at the Plastic Soup Foundation.

“Agricultural fields in Europe and North America are estimated to receive far higher quantities of microplastics than global oceans,” Vonk says.
A recent pilot study commissioned by the Plastic Soup Foundation found microplastics in all blood samples collected from pigs and cows on Dutch farms, showing livestock are capable of absorbing some of the plastic particles from their feed, water or air. Of the beef and pork samples collected from farms and supermarkets as part of the same study, 75 percent showed the presence of microplastics. Multiple studies document that microplastic particles are also in fish muscle, not just the gut, and so are likely to be consumed when people eat seafood.

Microplastics are in our drinking water, whether it’s from the tap or bottled. The particles may enter the water at the source, during treatment and distribution, or, in the case of bottled water, from its packaging.

Results from studies attempting to quantify levels of human ingestion vary dramatically, but they suggest people might be consuming on the order of tens of thousands of microplastic particles per person per year. These estimates may change as more data come in, and they will likely vary depending on people’s diets and where they live. Plus, it is not yet clear how these particles are absorbed, distributed, metabolized and excreted by the human body, and if not excreted immediately, how long they might stick around.

Babies might face particularly high exposures. A small study of six infants and 10 adults found that the infants had more microplastic particles in their feces than the adults did. Research suggests microplastics can enter the fetus via the placenta, and babies could also ingest the particles via breast milk. The use of plastic feeding bottles and teething toys adds to children’s microplastics exposure.

Microplastic particles are also floating in the air. Research conducted in Paris to document microplastic levels in indoor air found concentrations ranging from three to 15 particles per cubic meter of air. Outdoor concentrations were much lower.

Airborne particles may turn out to be more of a concern than those in food. One study reported in 2018 compared the amount of microplastics present within mussels harvested off Scotland’s coasts with the amount of microplastics present in indoor air. Exposure to microplastic fibers from the air during the meal was far higher than the risk of ingesting microplastics from the mussels themselves.

Extrapolating from this research, immunologist Nienke Vrisekoop of the University Medical Center Utrecht says, “If I keep a piece of fish on the table for an hour, it has probably gathered more microplastics from the ambient air than it has from the ocean.”
What’s more, a study of human lung tissue reported last year offers solid evidence that we are breathing in plastic particles. Microplastics showed up in 11 of 13 samples, including those from the upper, middle and lower lobes, researchers in England reported.

Perhaps good news: Microplastics seem unable to penetrate the skin. “The epidermis holds off quite a lot of stuff from the outside world, including [nano]particles,” Leslie says. “Particles can go deep into your skin, but so far we haven’t observed them passing the barrier, unless the skin is damaged.”

What do we know about the potential health risks?
Studies in mice suggest microplastics are not benign. Research in these test animals shows that lab exposure to microplastics can disrupt the gut microbiome, lead to inflammation, lower sperm quality and testosterone levels, and negatively affect learning and memory.

But some of these studies used concentrations that may not be relevant to real-world scenarios. Studies on the health effects of exposure in humans are just getting under way, so it could be years before scientists understand the actual impact in people.

Immunologist Barbro Melgert of the University of Groningen in the Netherlands has studied the effects of nylon microfibers on human tissue grown to resemble lungs. Exposure to nylon fibers reduced both the number and size of airways that formed in these tissues by 67 percent and 50 percent, respectively. “We found that the cause was not the microfibers themselves but rather the chemicals released from them,” Melgert says.

“Microplastics could be considered a form of air pollution,” she says. “We know air pollution particles tend to induce stress in our lungs, and it will probably be the same for microplastics.”

Vrisekoop is studying how the human immune system responds to microplastics. Her unpublished lab experiments suggest immune cells don’t recognize microplastic particles unless they have blood proteins, viruses, bacteria or other contaminants attached. But it is likely that such bits will attach to microplastic particles out in the environment and inside the body.

“If the microplastics are not clean … the immune cells [engulf] the particle and die faster because of it,” Vrisekoop says. “More immune cells then rush in.” This marks the start of an immune response to the particle, which could potentially trigger a strong inflammatory reaction or possibly aggravate existing inflammatory diseases of the lungs or gastrointestinal tract.
Some of the chemicals added to make plastic suitable for particular uses are also known to cause problems for humans: Bisphenol A, or BPA, is used to harden plastic and is a known endocrine disruptor that has been linked to developmental effects in children and problems with reproductive systems and metabolism in adults (SN: 7/18/09, p. 5). Phthalates, used to make plastic soft and flexible, are associated with adverse effects on fetal development and reproductive problems in adults along with insulin resistance and obesity. And flame retardants that make electronics less flammable are associated with endocrine, reproductive and behavioral effects.

“Some of these chemical products that I worked on in the past [like the polybrominated diphenyl ethers used as flame retardants] have been phased out or are prohibited to use in new products now [in the European Union and the United States] because of their neurotoxic or disrupting effects,” Leslie says.
What are the open questions?
The first step in determining the risk of microplastics to human health is to better understand and quantify human exposure. Polyrisk — one of five large-scale research projects under CUSP, a multidisciplinary group of researchers and experts from 75 organizations across 21 European countries studying micro- and nanoplastics — is doing exactly that.

Immunotoxicologist Raymond Pieters, of the Institute for Risk Assessment Sciences at Utrecht University and coordinator of Polyrisk, and colleagues are studying people’s inhalation exposure in a number of real-life scenarios: near a traffic light, for example, where cars are likely to be braking, versus a highway, where vehicles are continuously moving. Other scenarios under study include an indoor sports stadium, as well as occupational scenarios like the textile and rubber industry.

Melgert wants to know how much microplastic is in our houses, what the particle sizes are and how much we breathe in. “There are very few studies looking at indoor levels [of microplastics],” she says. “We all have stuff in our houses — carpets, insulation made of plastic materials, curtains, clothes — that all give off fibers.”

Vethaak, who co-coordinates MOMENTUM, a consortium of 27 research and industry partners from the Netherlands and seven other countries studying microplastics’ potential effects on human health, is quick to point out that “any measurement of the degree of exposure to plastic particles is likely an underestimation.” In addition to research on the impact of microplastics, the group is also looking at nanoplastics. Studying and analyzing these smallest of plastics in the environment and in our bodies is extremely challenging. “The analytical tools and techniques required for this are still being developed,” Vethaak says.

Vethaak also wants to understand whether microplastic particles coated with bacteria and viruses found in the environment could spread these pathogens and increase infection rates in people. Studies have suggested that microplastics in the ocean can serve as safe havens for germs.

Alongside knowing people’s level of exposure to microplastics, the second big question scientists want to understand is what if any level of real-world exposure is harmful. “This work is confounded by the multitude of different plastic particle types, given their variations in size, shape and chemical composition, which can affect uptake and toxicity,” Leslie says. “In the case of microplastics, it will take several more years to determine what the threshold dose for toxicity is.”

Several countries have banned the use of microbeads in specific categories of products, including rinse-off cosmetics and toothpastes. But there are no regulations or policies anywhere in the world that address the release or concentrations of other microplastics — and there are very few consistent monitoring efforts. California has recently taken a step toward monitoring by approving the world’s first requirements for testing microplastics in drinking water sources. The testing will happen over the next several years.

Pieters is very pragmatic in his outlook: “We know ‘a’ and ‘b,’” he says. “So we can expect ‘c,’ and ‘c’ would [imply] a risk for human health.”

He is inclined to find ways to protect people now even if there is limited or uncertain scientific knowledge. “Why not take a stand for the precautionary principle?” he asks.

For people who want to follow Pieters’ lead, there are ways to reduce exposure.

“Ventilate, ventilate, ventilate,” Melgert says. She recommends not only proper ventilation, including opening your windows at home, but also regular vacuum cleaning and air purification. That can remove dust, which often contains microplastics, from surfaces and the air.

Consumers can also choose to avoid cosmetics and personal care products containing microbeads. Buying clothes made from natural fabrics like cotton, linen and hemp, instead of from synthetic materials like acrylic and polyester, helps reduce the shedding of microplastics during wear and during the washing process.

Specialized microplastics-removal devices, including laundry balls, laundry bags and filters that attach to washing machines, are designed to reduce the number of microfibers making it into waterways.

Vethaak recommends not heating plastic containers in the microwave, even if they claim to be food grade, and not leaving plastic water bottles in the sun.

Perhaps the biggest thing people can do is rely on plastics less. Reducing overall consumption will reduce plastic pollution, and so reduce microplastics sloughing into the air and water.

Leslie recommends functional substitution: “Before you purchase something, think if you really need it, and if it needs to be plastic.”

Westerbos remains hopeful that researchers and scientists from around the world can come together to find a solution. “We need all the brainpower we have to connect and work together to find a substitute to plastic that is not toxic and doesn’t last [in the environment] as long as plastic does,” she says.

A thick sphere of icy debris known as the Oort cloud shrouds the solar system. Other star systems may harbor similar icy reservoirs, and those clouds may be visible in the universe’s oldest light, researchers report.

Astronomer Eric Baxter of the University of Pennsylvania and colleagues looked for evidence of such exo-Oort clouds in maps of the cosmic microwave background, the cool cosmic glow of the first light released after the Big Bang, roughly 13.8 billion years ago. No exo-Oort clouds have been spotted yet, but the technique looks promising, the team reports November 2 in the Astronomical Journal. Finding exo-Oort clouds could help shed light on how other solar systems — and perhaps even our own — formed and evolved.
The Oort cloud is thought to be a planetary graveyard stretching between about 1,000 and 100,000 times as far from the sun as Earth. Scientist think that this reservoir of trillions of icy objects formed early in the solar system’s history, when violent movements of the giant planets as they took shape tossed smaller objects outward. Every so often, one of those frozen planetary fossils dives back in toward the sun and is visible as a comet (SN: 11/16/13, p. 14).

But it’s difficult to observe the Oort cloud directly from within it. Despite a lot of circumstantial evidence for the Oort cloud’s existence, no one has ever seen it.

Ironically, exo-Oort clouds might be easier to spot, Baxter and colleagues thought. The objects in an exo-Oort cloud wouldn’t reflect enough starlight to be seen directly, but they would absorb starlight and radiate it back out into space as heat. For the sun’s Oort cloud, that heat signal would be smeared evenly across the entire sky from Earth’s perspective. But an exo-Oort cloud’s warmth would be limited to a tiny region around its star.

Baxter and colleagues calculated that the expected temperature of an exo-Oort cloud should be about –265° Celsius, or 10 kelvins. That’s right in range for experiments that detect the cosmic microwave background, or CMB, which is about 3 kelvins.
The team used data from the CMB-mapping Planck satellite to search for areas across the sky with the right temperature (SN Online: 7/24/18). Then, the researchers compared the results with the Gaia space telescope’s ultraprecise stellar map to see if those regions surrounded stars (SN: 5/26/18, p. 5).

Although the astronomers found some intriguing signals around several bright, nearby stars, it wasn’t enough to declare victory. “That’s pretty interesting, but we can’t definitively say that it’s from an Oort cloud or not,” Baxter says.

Other ongoing CMB experiments with higher resolution, like those with the South Pole Telescope and the Atacama Cosmology Telescope in the Chilean Andes, could confirm if those hints of exo-Oort clouds are real.

“It’s a super clever observational idea,” says astronomer Nicolas Cowan of McGill University in Montreal who was not involved in the new work. “Looking for exo-Oort clouds is looking for a signature of these violent histories in other solar systems.”

Cowan has suggested that the cosmic microwave background could also be used to search for a hypothetical Planet Nine in the sun’s Oort cloud (SN: 7/23/16, p. 7). “The very coolest thing would be if we could get measurements of the exo-Oort clouds and find planets in those systems,” he says.

A newly designed airplane prototype does away with noisy propellers and turbines.

Instead, it’s powered by ionic wind: charged molecules, or ions, flowing in one direction and pushing the plane in the other. That setup makes the aircraft nearly silent. Such stealth planes could be useful for monitoring environmental conditions or capturing aerial imagery without disturbing natural habitats below.

The aircraft is the first of its kind to be propelled in this way, researchers report in the Nov. 22 Nature. In 10 indoor test flights the small plane, which weighs about as much as a Chihuahua, traveled 40 to 45 meters for almost 10 seconds at a steady height, even gaining about half a meter of altitude over the course of a flight.
Most planes rely on spinning parts to move forward. In some, an engine turns a propeller that pushes the plane forward. Or a turbine sucks in air with a spinning fan, and then shoots out jets of gas that propel the plane forward.

Ionic wind is instead generated by a high-voltage electric field around a positively charged wire, called an emitter. The electricity, often supplied by batteries, makes electrons in the air collide with atoms and molecules, which then release other electrons. That creates a swarm of positively charged air molecules around the emitter, which are drawn to a negatively charged wire. The movement of molecules between the two wires, the ionic wind, can push a plane forward. The current design uses four sets of these wires.
Moving ions have helped other things to fly through the air, such as tiny airborne robots. But conventional wisdom said that using the approach to move something through the air as big as an airplane wasn’t possible, because adding enough battery power to propel a plane this way would make it too heavy to stay aloft. (The ion thrusters that propel spacecraft through the vacuum of space work in a very different way and aren’t functional in air.) Attempts to build ion-propelled aircraft in the 1960s weren’t very successful.
MIT aeronautics researcher Steven Barrett thought differently. With the right aircraft design and light enough batteries, flight might be possible, his initial calculations suggested. So he and his team used mathematical equations to optimize various features of the airplane — its shape, materials, power supply — and to predict how each version would fly. Then the researchers built prototypes of promising designs and tested the planes at the MIT indoor track, launching them via a bungee system.
“The models and the reality of construction don’t always match up perfectly,” Barrett says, so finding the right design took a lot of tries. But in the new study, he and his collaborators report success: 10 flights of the aircraft, which has a 5-meter wingspan and weighs just under 2.5 kilograms.

Barrett’s team isn’t the only one who thought the ionic wind method might take off. Based on calculations done in his lab, “we were confident that this could be done,” says Franck Plouraboue of the Toulouse Fluid Mechanics Institute in France, who wasn’t part of the research. “Here they’ve done it — which is fantastic!”

It’s an example of distributed electric propulsion, says Plouraboue — spreading out the thrust-generating parts of the plane, instead of having one centralized source. That’s a hot area for aircraft research right now. NASA’s X-57 Maxwell plane, for example, bears 14 battery-operated motors along its wings. Increasing the number of propellers makes the plane go farther on the same amount of energy, says Plouraboue, but also increases the drag. With ionic wind propulsion, increasing the number of wires doesn’t increase drag very much.

The plane still needs some upgrades before it’s ready for the real world: Its longest flight was only 12 seconds. And while the aircraft can maintain steady flight for a short time once launched, it can’t actually get off the ground using ionic wind.

Even with improvements, ion-propelled aircraft won’t find their niche as passenger planes, predicts Daniel Drew, an aerodynamics researcher at the University of California, Berkeley, who was not involved in the work. (Drew has designed miniature flying bots that fly using ionic propulsion.) It’s probably not feasible to scale up to something the size of a 747 — there are efficiency trade-offs as planes get bigger, he says. But down the road, the approach might be useful for small, uncrewed planes or drones.

From tales about whales to enthralling scientific histories and the memoir of a frustrated astrophysicist, 2018 was a banner year for science books. Here are Science News’ picks for the titles that should be on any science lover’s bookshelf. Find detailed reviews of many of these books in the links below and in our Editor’s Pick: Favorite books of 2018.

The Truth About Animals
Lucy Cooke

A zoologist debunks myths about bats, pandas, Adélie penguins and many other misunderstood creatures, recounting surprising stories from the animal kingdom (SN: 4/14/18, p. 26). Basic Books, $28

Spying On Whales
Nick Pyenson

In this captivating look at whales, a paleontologist dives into the animals’ past, exploring how some of Earth’s most intelligent species came to be, and their uncertain future (SN: 7/7/18, p. 29). Viking, $27

Eager
Ben Goldfarb

Some people see beavers as pests. But a science writer explains how the dam-building rodents are actually vital ecosystem engineers that can create or expand habitats that benefit the entire wildlife community (SN: 8/4/18, p. 28). Chelsea Green Publishing, $24.95

The Rise and Fall of the Dinosaurs
Steve Brusatte

In this memoir, a paleontologist blends experiences from his career with evolutionary science to take readers on an engrossing journey through time, from the beginnings of the dinosaurs to their ultimate extinction. William Morrow, $29.99

The Big Ones
Lucy Jones

A seismologist examines past catastrophic natural disasters, including volcanic eruptions, earthquakes and floods, and their impact on culture, politics and society (SN: 3/31/18, p. 26). With the past as a guide, the author warns readers to be prepared for when the next disaster strikes. Doubleday, $26.95

Losing the Nobel Prize
Brian Keating

An astrophysicist’s dream of winning a Nobel Prize turned to dust after a promising experiment failed to find the first definitive evidence of cosmic inflation. The experience revealed how the prize can hamper scientific progress (SN: 4/14/18, p. 27). W.W. Norton & Co., $27.95

The Poisoned City
Anna Clark

Weaving together history, science and reporting, a journalist explores the public health crisis that began in Flint, Mich., when lead started leaching into residents’ drinking water (SN: 7/21/18, p. 28). Metropolitan Books, $30

The Poison Squad
Deborah Blum

A Pulitzer Prize–winning journalist tells the story of a government chemist at the turn of the 20th century and his mission to make food safe in the United States. Penguin Press, $28

Aroused
Randi Hutter Epstein

The history of endocrinology makes for a strange and fascinating read, from the scientists who discovered the effects of hormones to the people whose lives have been irrevocably changed by these powerful substances (SN: 7/7/18, p. 28). W.W. Norton & Co., $26.95

Nine Pints
Rose George

Blood, the feared as well as revered substance that flows throughout the human body, has a rich historical and scientific past (SN: 10/27/18, p. 28). Metropolitan Books, $30

She Has Her Mother’s Laugh
Carl Zimmer

This comprehensive history recounts how researchers have come to understand genetic inheritance. Looking to the future, the author considers risks of gene manipulation (SN: 6/9/18, p. 29). Dutton, $30

Genetics in the Madhouse
Theodore M. Porter

Using archival records, a science historian traces the origins of the study of human heredity to insane asylums in the 1800s (SN: 7/7/18, p. 29). Princeton Univ., $35

The Tangled Tree
David Quammen

In chronicling the lives of researchers who made important advances in molecular biology and genetics, this book shows how recent findings shake up our understanding of evolution and the tree of life. Simon & Schuster, $30

Poop contains a lot of valuable scientific information. Researchers can monitor microbes, track enzyme activity or hunt for DNA to gather clues about overall health.

There’s so much one can learn from the waste product that microbiologist Aadra Bhatt at the University of North Carolina at Chapel Hill decided there should be a word for that research — something in the same vein as “in vivo” (research done in living animals) and “in vitro” (research done in a petri dish).

After some linguistic digging, she and two colleagues settled on “in fimo.” The term comes from fimus, one of several Latin words for manure or excrement. Their choice won out over the more obvious option of “in feces” because the word feces doesn’t have the same rich scatological legacy — originally it referred to the dregs in a wine cask, Bhatt says.

She and her colleagues, while already using in fimo at meetings and seminars, published their argument online December 13 in Gastroenterology. Compared with the laborious process of pulling together a scientific paper, coming up with this term was “delightful — and it wasn’t particularly drawn out,” Bhatt says. She hopes the word catches on and gains a place in the lexicon for poopetuity.