A person is tested for COVID-19 at a drive-thru testing site in Florida in July 2020. Image Credit: Paul Hennessy/NurPhoto, Getty Images

Figuring out when to get tested after exposure requires understanding what happens once the virus enters your body. We’ve got you covered.

I’ve been exposed to Covid-19. When should I get tested?

Aqueous film-forming foam (AFFF), a powerful fire suppressant, is currently being phased out of use by the U.S. military. The foam is a major source of PFAS contamination in drinking water around the country. Image Credit: FEMA/U.S. Fire Administration

What makes PFAS chemicals extremely useful—and extremely hard to get rid of—are the bonds between carbon and fluorine atoms that are almost impossible to break.

Toxic synthetic 'forever chemicals' are in our water and on our plates

The bluespotted ribbontail ray (Taeniura lymma) is one of more than 200 stingray species found around the world. Image Credit: Antagain, Getty Images

Animal venoms are useful for drugmakers because they’re potent, targeted, and fast-acting. Trust me, I would know.

I got stung by a stingray, and all I got was this deeper understanding of venom medicine

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NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology. Launched in 2012, we feature in-depth articles and commentaries from some of the most respected journalists, scientists, and engineers. NOVA Next explores the ideas that are changing the future, from the frontiers of synthetic biology to the politics of personalized medicine.Let us know what you think. We’re listening on <a href="http://www.facebook.com/NOVAonline">Facebook</a>, <a href="http://twitter.com/novapbs">Twitter</a>, and email.If you’re a journalist and have an idea for a story, send it our way.

NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.

NOVA Next

NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.

NASA has delayed the first flight of its Ingenuity Mars helicopter, announcing that it expects to set a new date next week.The helicopter, which arrived on the red planet tucked inside <a href="https://www.pbs.org/wgbh/nova/article/nasa-perseverance-mars-rover-landing-success/">the Perseverance rover</a> in February, was initially set to fly on Sunday, securing its position as the first rotorcraft to lift off on another world. Late on Friday night, however, a high-speed test of Ingenuity’s rotors <a href="https://mars.nasa.gov/technology/helicopter/status/291/mars-helicopter-flight-delayed-to-no-earlier-than-april-14/">ended early</a>: As the helicopter’s command sequence tried to transition the flight computer from “preflight” to “flight” mode, engineers were alerted to a potential problem. The team has decided to update Ingenuity’s flight control software before attempting a maiden flight.During this first flight, the Ingenuity Mars helicopter will lift off, hover 10 feet above the Martian surface, take pictures, and touch back down—all in a period of about 40 seconds. Meanwhile, some 200 feet away, the Perseverance rover will snap pictures and videos of its companion’s brief voyage.
 

 
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 This first flight will be a modest beginning of a much more ambitious task: In the next 30 days, the Ingenuity team at NASA’s <a href="https://www.jpl.nasa.gov/">Jet Propulsion Laboratory</a> will attempt a total of five flights, each longer and more technical than the last.“Each world only gets one first flight,” Ingenuity Project Manager MiMi Aung said during a press conference on Friday. It’s a “historic moment that has analogues in 1903,” NASA’s Associate Administrator for Science Thomas Zurbuchen added, referring to the year the <a href="https://www.pbs.org/wgbh/nova/article/unlikely-inventors/">Wright brothers</a> became the first in the world to fly a motor-operated airplane—after two failed liftoffs.“History tells us that Orville and Wilbur took this setback like true engineers,” confirming that their fundamental understanding of flight was correct and going back and making subtle changes, Aung said during Friday’s press conference. Aung believes she and her team have become similarly well-versed in the unique challenges of flying a hovercraft on another planet and are aware that despite years of preparation, something could go wrong when it’s time for the first attempt. “I want to be conservative,” Aung said on Friday, adding the Ingenuity team had yet to celebrate the Mars helicopter’s achievements.Perhaps the greatest challenge the team will face is the <a href="https://www.pbs.org/wgbh/nova/video/mars-facts-red-planet/">Martian atmosphere</a>. Made up of mostly carbon dioxide, Mars’ atmosphere is a mere 1% as thick as our own planet’s, which is primarily nitrogen. Its thinness makes it the equivalent of flying at three times the height of Mount Everest, Ingenuity chamber test engineer Amelia Quon said on Friday.Rotorcrafts, including helicopters, fly by generating lift. As their blades spin, they push the air and this lifts the craft up, Aung explains. In a thin atmosphere, she says, there are fewer molecules to push, “so you need to spin much faster to get lift,” she says. While the blades of most Earthly helicopters operate at around 450 to 500 revolutions per minute, Ingenuity’s will move at 2,400 rpm.Ingenuity’s rotors “are not something off the shelf; they’re really fine-tuned to maximize lift in a really thin atmosphere,” Aung said. Weighing in at about 35 grams, the rotors have a foam core for lightweightedness and are covered in carbon fiber, laid out in a grid, for optimal stiffness and strength.Like its blades, the body of the Mars helicopter is also lightweight, at less than four pounds. “We couldn’t make this happen” with technology that existed 10 or 15 years ago, Aung said.Mars’ strong winds also pose a challenge. If gusts become too strong before Ingenuity is scheduled to fly, there’s no way of automatically postponing or canceling the flight through Perseverance, Ingenuity Operations Lead Tim Canham explained during Friday’s press conference. This is because the Perseverance rover’s weather-determining system has no connection to Ingenuity. And Ingenuity has no way to right itself; if it fails to land right-side-up during any of its flights, its mission on Mars would end.
 

 
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 But there’s good news: Martian weather is easy to predict. “Weather on Mars tends to stay the same over a period of sols,” Canham explains. (At 24 hours, 39 minutes, and 35 seconds, a Martian sol is slightly longer than a day on Earth.) The Ingenuity team initially chose 12:30 p.m. Martian time Sunday, the equivalent of 11:00 p.m. EDT, for a potential first liftoff because the team calculated that’s when Ingenuity would have the most charged battery and Mars would have the calmest skies.The team started testing in 2014 whether Ingenuity could successfully fly on another planet. We “made Mars on Earth,” Quon said, referring to NASA’s Jet Propulsion Laboratory’s 25-foot space simulator thermal vacuum chamber, which Voyager 1 and 2 were tested in before making their way into space and out of our solar system.First, the team used a flight model to illustrate that lift is possible—picture a couple of hops and a crash landing—in a Martian-like environment. Then, in 2018, the team had the model spin up three feet in the air and turn. In 2019, NASA scientists took data from previous tests and applied them to testing the actual Ingenuity Mars helicopter.If all goes well, during its first sol after taking to the sky, Ingenuity will transmit its black-and-white photos and flight summary data to Perseverance, which will transmit the data to scientists on Earth. In the following days, scientists expect to receive color imagery and more complex data from the flight.
 <figure class="richtext-image full-width"><img alt="Perseverance_Selfie.jpg" class="richtext-image full-width" height="450" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Perseverance_Selfie.width-800.jpg"/><figcaption>NASA’s Perseverance Mars rover took a selfie with the Ingenuity helicopter, seen here about 13 feet (3.9 meters) from the rover in this image taken April 6, 2021, the 46th Martian day, or sol, of the mission. Image credit: NASA/JPL-Caltech/MSSS<div class="credit"></div></figcaption>
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 Canham is also eager to hear the sound of Ingenuity’s liftoff: Perseverance is equipped with a microphone specifically designed to survive on Mars—and capture the <a href="https://www.scientificamerican.com/article/perseverance-mars-rover-records-sound-of-rock-zapping-laser1/">snaps, crackles and pops of its sizzling stones</a>. It’s possible for the microphone to capture Ingenuity’s liftoff, but given its somewhat significant distance (more than 200 feet) from the helicopter, there are no guarantees. It’s “very touch and go on whether we’ll get anything,” Canham said on Friday. “But who knows.”What’s more certain is that Perseverance will capture its own photos of Ingenuity’s first flight.Before, during, and after Ingenuity’s 40-second airtime, Perseverance will snap six to seven photos a second using its onboard <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/mastcam-z/">Mastcam-Z cameras</a>, one with zoomed-in perspective and the other a zoomed-out perspective. (You can view images as they come in on <a href="http://go.nasa.gov/perseverance-raw-images">NASA’s website here</a>.)The Ingenuity team expects its second flight to happen four days after its initial flight. And if that one goes well—the goal being to have the helicopter fly up to 15 feet—the team will move to an every-three-day flight cadence.“We want to have fun” with the fourth and fifth flights, Aung said, suggesting that the team may venture at least 150 feet out and back from the helicopter’s takeoff site, possibly into never-before-seen territory. “This is all about the future. This is all about being a pathfinder,” she said, explaining that Ingenuity can inform how future space helicopters, which will be bigger and heavier, should function.Like NASA’s <a href="https://www.nasa.gov/mission_pages/mars-pathfinder">first Mars rover</a>—the modest 23-pound microwave-sized Sojourner, which touched down on the red planet in 1997—Ingenuity is a “tech demonstration,” explained Zurbuchen, NASA’s Associate Administrator for Science. Similar to Sojourner’s brief mission on Mars, Zurbuchen believes, decades from now, we’ll look back on Ingenuity’s month of flight with awe and fondness.“Ingenuity’s month will be an aggressive demonstration of what it can possibly do,” he said. And, teammate Elsa Jensen added, “Big Sister”—Perseverance—“will be watching.”
 

 
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A close-up of Ingenuity taken on April 5 by Mastcam-Z, a pair of zoomable cameras aboard the Perseverance rover. Credit: NASA/JPL-Caltech/ASU.

Want to fly a rotorcraft on another planet? Here’s what it takes.

What to expect during NASA’s first-ever Mars helicopter flight

You’ve seen the images: floating islands of plastic in the ocean, marine life entangled in nets and lines. Whether in the ocean or on land, <a href="https://www.pbs.org/wgbh/nova/article/bacteria-plastic-biodegradable-pha-recycling/">plastic pollutants</a>—and their effects—are often visible.But not all pollutants are.“What most people don’t realize is that there has been pollution for a long time,” says Desiree Plata, an environmental engineer and chemist at the Massachusetts Institute of Technology (MIT). “Most of it we just can’t see.”Enter methane, a colorless, odorless chemical that, like carbon dioxide and other greenhouse gases, contributes to climate change by collecting in our atmosphere and trapping radiation from the sun. Methane is emitted into the air by many sources, including <a href="https://www.nature.com/articles/d41586-021-00659-y">melting permafrost</a>, gassy cows, and oil and gas drilling sites. And it’s about <a href="https://www.scientificamerican.com/article/how-bad-of-a-greenhouse-gas-is-methane/">86 times more potent</a> than carbon dioxide, according to the Intergovernmental Panel on Climate Change.
 

 
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 Methane is the main ingredient in natural gas, which powers 48% of homes in the United States. Commercial natural gas is scented with odorants to make a potential gas leak detectable, alerting a resident to shut off their stove or track down the leak.“I like to call methane ‘the elephant in the atmosphere,’” Plata says. “It’s the gas everyone should be talking about, but few people know about.”But now, a team at MIT is producing sensors to allow people to “see” methane, and ultimately track down its sources and mitigate its harmful effects.<h3>Sensor technology: by chemicals, for chemicals</h3>These methane sensors, developed by chemist Tim Swager <a href="https://www.c2sense.com/gas-sensors">and his team</a> at MIT, vary in size depending on how large of an area a user would like to monitor. The sensors could be big, shaped like a laptop briefcase for easy carrying. Or they could be small, about the size of a sticker, and shaped like the flat chip in your credit card.The sensors are inexpensive, low-power devices that can detect methane emissions in nature and at industrial sites, Swager said in an email. The company C2Sense is working with his team’s technology, which could be on the market within a few years.Though they’re not yet licensed for commercial use, Swager’s methane sensors have the potential to be as widely used as the carbon monoxide detectors we have in our homes. Methane is present in natural, industrial, and agricultural environments, and sometimes leaches into drinking water through the ground <a href="https://www.health.state.mn.us/communities/environment/water/wells/waterquality/methane.html">in the form of tiny gas bubbles</a>, meaning that anyone—from a farmer to an engineer to a homeowner—could use a sensor to get a better idea of the chemical’s presence in their air or water.All of Swager’s team’s sensors are powered by the same thing: chemical elements. Platinum and oxygen naturally react with methane, so they can be used in the sensors to detect methane in an environment, Swager explains.
 <figure class="richtext-image full-width"><img alt="Methane_Bubbles.jpg" class="richtext-image full-width" height="450" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Methane_Bubbles.width-800.jpg"/><figcaption>Ice-rich permafrost thaws in Alaska. The carbon stored in the formerly frozen ground is consumed by microbes, which release methane gas. Image credit: USGS<div class="credit"></div></figcaption>
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 Here’s how: The platinum in the sensor reacts with oxygen in the atmosphere, bonding to create a chemical compound. This compound then reacts with any methane present in the surrounding environment. “Basically, you’re oxidizing the methane,” Swager says. This reaction between the platinum-oxygen compound and methane sets off the sensor, which sends a notification to a specialized device (for an industrial-use sensor) or a cell phone (for a personal-use sensor).The sensor’s platinum and electrode sensing component “is very tiny—and that means that you could put it into lots of different structures,” says Plata, who’s not involved in Swager’s work. Unlike some other machinery that’s weighed down by the bulky essential technology within it, C2Sense’s sensors rely on very little to work, so they can be easily integrated into homes, barns, drilling sites, and other environments where methane is present.Gas sensors that can detect volatile organic compounds, including methane, already exist. But they’re not tailored to detect methane alone, Swager said in an email, and require temperatures higher than 570 F to operate. This makes them both costly and potentially dangerous around high concentrations of methane, a flammable gas.Conversely, Swager&#x27;s sensors can operate in ambient conditions and have low power requirements—they can run at submicrowatts—making them inexpensive to operate. And unlike existing sensors on the market, which generally need a battery pack or wiring to work, Swager&#x27;s sensors can be powered wirelessly and read by a smartphone.Some of the smaller prototype methane sensors are 0.08 inch (2mm) cubes, approximately as thick as a nickel. They can potentially help pinpoint leaks in homes or wells, attaching physically to an area where methane may spew from. The sensors can also attach to a cell phone for on-the-go sensing, reporting the changes in air or water quality right to a “mobile-friendly sensor platform” on the phone, Swager explains.That said, personal-use sensors may be a ways off, Swager cautions. Currently, odorants added to methane-containing gas serve as the main indicator for gas leaks in homes. Unfortunately, scent is only useful if you’re present and able to smell it. “Houses can blow up if there’s too much natural gas,” Swager says. When someone is away from their home or is unable to smell a leak, it’s harder to protect against a possible gas fire—<a href="https://www.nytimes.com/2020/02/26/us/columbia-gas-massachusetts.html">or worse, explosion</a>.
 

 
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 Another possible application for the sensors, Swager says, is to test well water, which <a href="https://www.usgs.gov/mission-areas/water-resources/science/domestic-private-supply-wells?qt-science_center_objects=0#qt-science_center_objects">millions of people</a> in the U.S. rely on. When methane is drilled underground, the gas sometimes escapes from the pipe it’s being pumped into, travels through the porous earth, and rises from the ground. “In the process of drilling down, you&#x27;ve created another pathway for the methane to reach the surface. It could come up 100 yards from the well pad depending on the location, even get into the groundwater,” Swager says. Because the gas is considered nontoxic by several state departments of public health, methane doesn’t have a <a href="https://www.rcap.org/resource/natural-gas-and-your-drinking-water-system/">Safe Drinking Water Act maximum contaminant level</a>. (Although the U.S. Department of the Interior suggests a <a href="https://extension.psu.edu/methane-gas-and-its-removal-from-water-wells">specific methane level</a> at which homeowners should vent their wells.)Larger sensors can sense transient leaks (leaks that start and stop) over large swaths of land. Intended for use by engineers, park rangers, and other professionals, industrial-use sensors could identify methane leaks at natural gas drilling sites, where methane comes up from the earth; forests, where <a href="https://www.nationalgeographic.com/environment/article/trees-release-methane-what-it-means-climate-change">raging fires can emit</a> the chemical; or large farms, where <a href="https://www.smithsonianmag.com/smart-news/seaweed-fed-cows-burp-less-planet-warming-methane-180977296/">methane-emitting livestock</a> live.Cattle farming is the <a href="https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane">leading cause of methane emissions</a> in the U.S., with nearly <a href="https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions#agriculture">2% of total greenhouse gas</a> emissions annually coming from the methane cows burp and fart (and the U.S. is the <a href="https://www.usda.gov/topics/animals/animal-production">world’s largest producer of beef</a>). Scientists have looked for ways to lower methane emissions from cattle farming, going so far as to put <a href="https://www.wired.co.uk/article/cows-climate-change-methane-stop">masks on cows to catch their burps</a>.<h3>Addressing the elephant in the room</h3>As methane and other greenhouse gases collect in the atmosphere, they “work as a blanket,” says Andra Garner, a climate scientist at Rowan University in New Jersey. “Methane is a much thicker and heavier blanket than carbon dioxide and if you add too many blankets, we start to get way too warm,” she explains.Beyond climate change and immediate safety risks of methane, the health effects of being exposed to high levels of methane over a prolonged period of time are also a concern, but haven’t been thoroughly investigated. Communities that have dealt with large amounts of methane leaking into their air—like the residents of Belmont County, Ohio, where one of the <a href="https://www.nytimes.com/2019/12/16/climate/methane-leak-satellite.html">biggest methane leaks ever recorded</a> in the U.S. happened in 2018—have reported respiratory problems and dizziness after being exposed to methane gas. In-home methane sensors could notify residents of leaks when their noses can’t, just like carbon monoxide and smoke detectors do.“You probably hear headlines all the time, ‘Everywhere we look for plastics in the environment, we find them,’” Plata says. “The same is true of most industrial chemicals, but the problem is I can’t pull out my cell phone and take a picture of [them]. Tim’s sensors are helping to close that gap.”Being able to see where methane comes from is the first step to controlling its effects on our planet. “Any time we have more data, that’s better; we get a better handle on where these emissions are coming from,” Garner says. After all, Plata says, “Getting chemicals out of the environmental system is a bigger challenge than trying to keep them from getting there in the first place.”
 

 
 

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Water flowing from a Weatherford, Texas resident's well ignites when he puts a flame to the well spigot. The U.S. Environmental Protection Agency had evidence a gas company's drilling operation contaminated his drinking water with explosive methane,  but withdrew its enforcement action, leaving the family with no useable water supply, according to a report obtained by The Associated Press. Image credit: Lm Otero/AP/Shutterstock

Methane is a greenhouse gas 86 times as potent as carbon dioxide. What if we could see methane emissions in real time?

Could tiny sensors keep methane out of our atmosphere—and homes?

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 We are outraged and heartbroken by the murders of eight people in Georgia, including six women of Asian descent. Anti-Asian racism has deep roots in our country’s history, but should have no place in our country’s future. In these challenging times, with anti-Asian sentiment on the rise nationwide, we believe that silence itself can be a form of violence. As leaders in public media, we feel it is imperative for us to clearly state our opposition to misogyny, hatred and racism in all forms. And we join our chief executive, Jon Abbott, in extending heartfelt support for our Asian American/Pacific Islander friends and family, colleagues, staff and the communities we serve.
 

 
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 John Bredar, VP for National Programming, GBHRaney Aronson-Rath, Executive Producer, FRONTLINEMarsha Bemko, Executive Producer, ANTIQUES ROADSHOWJulia Cort, Co-Executive Producer, NOVADenise DiIanni, Senior Executive in Charge, GBH STUDIO SIXLaurie Donnelly, Executive Producer, GBH STUDIO SIXCameo George, Executive Producer, AMERICAN EXPERIENCEChris Schmidt, Co-Executive Producer, NOVASusanne Simpson, Executive Producer, MASTERPIECEJudith Vecchione, Executive Producer, GBH STUDIO SIX
 

 
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NOVA GBH Joint Anti-Racism Statement Hero

This week’s tragic killings in Atlanta are a continuation of the anti-Asian racism the country has seen for the past year. The attached letter is a joint statement reflecting our collective stand against this racism and for a commitment to fostering inclusivity in our country.

Joint statement against anti-AAPI racism

Despite the efforts of recycling programs and environmental education, it’s still hard for many of us to grasp just how much plastic humans produce. We are on track to produce a billion tons of plastic a year by 2050. Cumulatively, we’ve already produced more than 8.3 billion metric tons since 1950. That’s 20 times the weight of all human beings alive right now. The systems we’ve developed for recycling that plastic are full of logistical, political, and economic obstacles, and the numbers show it. By 2015, three quarters of those <a href="https://www.pbs.org/wgbh/nova/article/76-of-all-plastic-ever-made-has-already-been-discarded/">8 billion metric tons of plastic were already out of use</a>, with 9% of it having been recycled and 12% incinerated. A whopping 79% wound up in landfills or the natural environment, destined to sit virtually unchanged for hundreds, if not thousands, of years.
 

 
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 It doesn’t have to be this way. “Plastic” is a category that encompasses a huge diversity of materials with one thing in common: They’re made of repeating chains of molecules known as “polymers” and can be molded or extruded while soft to take particular shapes. Until recently, we&#x27;ve only looked to petrochemicals (made from crude oil and natural gas) to create plastics with the properties we find so useful: the rigidity of takeout utensils, the flexibility of plastic films, the moisture barrier that contains greasy food. Although some less-common petroplastics are indeed biodegradable, bioplastics—which are often made from plant materials like sugar cane pulp, corn, or cassava and in many cases biodegrade after relatively short periods—may also be able to help address our big plastic problem.Enter polyhydroxyalkanoates, also known as PHAs, polymers used to make biodegradable bioplastics from an unlikely source: bacteria guts. PHAs and other bioplastics seek to challenge our assumptions about what plastic can be, and companies like Danimer in Georgia and Mango Materials in California are betting big that their products can help make a dent in our plastic waste numbers. Danimer’s partnership with Bacardi will see that company unveiling PHA bottles in all of its liquor lines by 2023; it also has partnerships in the works with <a href="https://www.fastcompany.com/90569273/pepsi-nestle-and-bacardi-are-all-using-this-new-plastic-like-packaging-thats-compostable-anywhere">Nestle, Pepsico, and other giants</a> of single-use plastic. Meanwhile, Mango is making inroads into other plastic-reliant industries, like apparel. (Yes, your workout clothes have plastic in them.)But PHAs aren’t new. They’ve been around for 35 years, and doubters like to point to Metabolix, a PHA company that seemed promising, grew quickly, and then collapsed in 2016. Metabolix and other would-be innovators have lived and died trying to “make PHAs happen.” Is now the time for this bioplastic to break through?
 

 
 

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 You might not think plastic and beer have much in common, but in the case of PHAs, there’s some surprising overlap. The bio-based plastic is derived from what amounts to bacteria guts, a polymer the microorganisms use to turn food into energy stored away for a rainy day. To make that polymer into something usable for humans, PHA scientists and entrepreneurs grow the bacteria in big vats under specific conditions, feeding them with vegetable oil, sugar, or methane gas and waiting to harvest the results. So far, kinda like beer.Here’s where it gets a little different. When the bacteria have gotten so full and roly-poly that they’re barely bacteria anymore—when their cells have gone from around 3% polymer to upwards of 95%—they’re subject to a purification process that bursts their membranes and brings the polymer out of solution. The resulting white powder is combined in pellets that then can be made into straws and takeout containers. Voila: plastic that’s not just made without fossil fuels but is also fully compostable, biodegrading in both your backyard and the ocean.We’ve known about bacteria’s capacity to manufacture plastic since the 1920s. But it took until 1983 to figure out how to get the polymers from inside the bacteria into human hands and until quite recently for that to happen on a scale that could be commercialized. “If you think of what we knew in the early 20th century about bacteria, microscopy, evolution, all those things have rapidly evolved,” says Mango Materials CEO Molly Morse. Only in the last decade have we had the tool set to <a href="https://link.springer.com/chapter/10.1007/978-3-642-03287-5_2">make PHAs a reality</a>.
 <figure class="richtext-image full-width"><img alt="small white plastic pellets" class="richtext-image full-width" height="600" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/biopolymer_pellets.width-800.jpg"/><figcaption>Pellets made from PHA biopolymers. Photo courtesy of Mango Materials<div class="credit"></div></figcaption>
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 Now, there are over 150 types of PHAs, which differ based on the length of their molecules, how they’re structured, which microorganisms are producing them, and what those microorganisms are fed. The longer the molecule chains, the more flexible and stretchable the plastic is; the shorter they are, the more brittle the material becomes. PHAs melt and flow like petroplastics and they can be turned into sheets or molded into many forms. That makes them great for all kinds of applications with one thing in common: whether in backyard compost, in industrial composting facilities, or in the ocean, they’ll completely biodegrade within six months. The big difference is that petroplastics are synthetic, and while bacteria may attempt to break them down, those organisms lack enzymes to break the plastics’ carbon-carbon bonds, making full degradation impossible. But since bacteria already use PHAs to store energy, they have built-in ways to both recognize and break them down. That’s what makes PHAs uniquely biodegradable—but only in specific settings. To understand why this is possible, “think about wood,” says Danimer Chief Technology Officer Phil Van Trump. If you build your desk out of wood, it won’t just disappear out of your house one day; it needs the right environment for that. “But in your yard, it’s a different story. Put it back in that environment, and bacteria and fungi will recognize it as food and start in on it.”
 

 
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 Of course, there are some drawbacks. In plastic-nerd parlance, PHAs have a “narrow processing window,” which means that their melting point and the point at which heat transforms them chemically into something else are only 10 degrees apart. That limits the ways they can be processed to stand in for petroplastics—for example, in materials that are subjected to very high heat or need very high mechanical strength, like airplane windshields, car bumpers, or bulletproof vests. But PHAs&#x27; biggest drawback is cost. Production is relatively expensive, especially the part of the process that draws the polymer out of the bacteria, says Amar Mohanty, a polymer and plastics engineer at the University of Guelph in Canada. Though there are different techniques for doing so, they often require large amounts of expensive chemicals like acetone or chloroform. “And to get a really purified polymer, you need to repeat the steps two or three times,” adds his colleague, fellow engineer Manjusri Misra.PHAs, like other bioplastics, also release methane when they degrade under anaerobic conditions (like in landfills). Since methane is a major contributor to greenhouse gas emissions, some critics worry that if PHA products grow popular and then are improperly disposed of, they may end up contributing to the climate crisis. In response, Van Trump and Mohanty stress the importance of developing proper waste-disposal infrastructure along with PHA technology, including industrial composting and digesters. “There’s growing we need to do as a society with how much we stick in landfills,” Van Trump says. In her work at Mango Materials, Morse has taken the methane release issue in a different direction, since Mango’s PHA bacteria actually feed on methane to grow their polymer. Mango has even partnered with Silicon Valley Clean Water in Redwood City, California, to build a digester on site and harness the methane coming off the city’s waste. At just that single location, Mango could produce up to 10 million pounds of PHA plastic per year.And then there’s the question of toxicity. In a <a href="https://www.sciencedirect.com/science/article/pii/S0160412020320213">recent study</a>, Lisa Zimmerman, a biologist at Goethe University in Germany, tested 40 different bioplastics, including one PHA product, and found they were not on average any less toxic than regular plastics. And when chemicals from the bioplastics leached into an environment where Zimmerman was raising microorganisms, many of them (including those from the PHA product) exhibited the potential to simulate hormones and interrupt the organisms’ metabolisms. Since some of the products she tested were not toxic, Zimmerman sees her result as an impetus to increase industry transparency. “The problem is that the product composition is not made openly available, so it’s really hard for other producers to integrate those less harmful chemicals,” she says. “To scale up, it would really help if it was openly communicated what is in the product.” 
 <figure class="richtext-image full-width"><img alt="2 plastic caps and roll of plastic film" class="richtext-image full-width" height="396" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Bioplastic_products.width-800.png"/><figcaption>Plastic caps (left) and film (right) produced from PHA biopolymers. Photos courtesy of Mango Materials<div class="credit"></div></figcaption>
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 Still, all the people interviewed for this article see the current moment as a time with enormous potential for bioplastics. As recently as 2014, when Mango applied for funding through the National Science Foundation to work on marine plastic pollution, their application was denied because the foundation “didn’t believe <a href="https://www.iucn.org/resources/issues-briefs/marine-plastics">plastics in the ocean were a problem</a>,” Morse says. She’s seen huge societal change since then, even noticing a difference just within the period of the COVID-19 pandemic. “People are at home staring at their trash cans wondering where all this stuff is going,” she says. “We’ve seen interest in the past 12 months like never before.”
 

 
 Van Trump also sees a major change in the attitudes of the corporations Danimer is partnering with, like Pepsi, Nestle, and Bacardi, which now seem more willing to invest in solutions to the plastics problem. “We’re growing like a weed,” he says of Danimer, which just opened new facilities in Georgia and Kentucky. And Van Trump and Morse both point out that price and scale are intimately connected. Bioplastics like PHAs are competing against a petroplastics industry producing in simply enormous volumes, with some single plants producing a billion pounds a year—and economies of scale make it possible for petroplastics companies to keep their prices low. “The industry has had 70 to 80 years to optimize and build capacity,” Van Trump says. He holds out hope, though, that “when we get to the scales of the ‘traditional’ polymers, then costs will come down dramatically.”In fact, Mohanty says the current problem for PHAs is the opposite of what it was in the days of Metabolix: too much demand and not enough production capacity. He expects the industry will grow into that demand in the coming decade, <a href="https://www.nytimes.com/2020/08/30/climate/oil-kenya-africa-plastics-trade.html">especially as widespread single-use petroplastic bans go into effect</a>. The key, in the meantime, is to educate consumers about their options and to build enough infrastructure that all those new PHA containers and films and straws don’t end up in landfills. Of our voracious plastic appetite, he says, “If we cannot stay away from it, we have to find ways to handle it.”
 

 
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Drinking straws are one of many single-use plastic products that could potentially be produced using biopolymers. Image Credit: Phichai, Shutterstock

Bioplastics called PHAs grow like beer and biodegrade like wood. And they may be able to help with our plastic waste problem.

Could plastic made from bacteria guts help solve our waste crisis?

Image Credit: Gallinago_media, Shutterstock

In the past year, millions of the animals have been culled to stop the spread of COVID-19 on mink farms across Europe. But this is more than just a fur coat crisis.

What’s the deal with mink Covid?

The grandson of Alabama slaves, Percy Julian worked tirelessly—transitioning from university classrooms to private laboratories; from the U.S. to Austria and back—to find a place that would allow him to work in chemistry. After one year as a department head at Howard University—a stint <a href="https://www.pbs.org/wgbh/nova/video/forgotten-genius/">that ended in his resignation</a>—Julian would go on to work at DePauw University, where he became the first to ever totally synthesize physostigmine, an alkaloid used to treat glaucoma.His other successes, which include synthesizing cortisone (used to treat arthritis) and progesterone (used to prevent miscarriages) improved society. They also helped pave the way for Black, Indigenous, and other people of color in STEM, and <a href="https://www.pbs.org/wgbh/nova/article/percy-julian/">inspire the next generation of scientists</a>.
 

 
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 One of those scientists is Percy Julian’s granddaughter, Katherine Julian. A physician and associate dean of graduate medical education at the University of California, San Francisco, Katherine trains medical residents and fellows, and researches medical education. Her work of practicing science and educating others mirrors—and honors—her grandfather’s legacy, and she sees Percy Julian’s sacrifices reflected in the work she and other Black scientists do today. A lot of Black people “have to work three times as hard” to be taken seriously, Katherine says. “I think that kind of work ethic is something that I have to continue to uphold—certainly in my professional world. That has been instilled in me in a lasting manner.” Katherine spoke with NOVA about her memories of Percy, her career, and the effect his life and work has had on the way she perceives progress in STEM today.Hanna Ali: <a href="https://www.pbs.org/wgbh/nova/article/blackinnature-tropical-paleontology/">Black scientists</a> and <a href="https://www.pbs.org/wgbh/nova/video/joys-challenges-birding-while-black-christian-cooper/">hobbyists</a> still face discrimination in the lab and in public, much like Percy Julian did himself. More often than not, the onus is on Black, Indigenous, and other people of color to push their way into STEM environments and educate their peers on what it means to treat them with humanity.Do you often find that your cohort of students is fairly diverse, and have you seen more strides being made at UCSF to make more opportunities for students of color?Katherine Julian: In my almost 25-year career—and I think this is not just at UCSF, this is on a larger scale—we’ve made great strides to become more diverse in science. Do I think we are where we need to be? No, of course not. And I still feel like we have a ways to go. We are not perfect. We have many things to learn and change. But I do feel like we are at a unique point—particularly now—because, unfortunately, of many current events. There is more consciousness-raising presently than I have seen in the last 20 years. I feel like that’s an incredible opportunity to be able to continue to make change.HA: In the time that your lives overlapped, did you witness your grandfather working as a chemist? If so, what impression did this leave on you?KJ: Well, he passed away when I was pretty young. The side that I saw of him was not necessarily the scientist side. I saw a side that was super passionate about gardening: the garden he had, around his house [in Chicago] and on the grounds of his home. He loved tulips—and planted thousands and thousands and thousands of tulip bulbs in the ground. [He’d] go out and garden every morning before going to work. I think it does reflect that he was someone who worked so incredibly hard. I think he was someone that put himself fully into many, many things. Obviously he had science. And moving that forward and to do the things that he did, I think required such incredible fortitude.HA: Did your grandfather use gardening as a way to educate the younger children in your family?KJ: I definitely remember being out there with him. I was probably too young for there to be any sort of education aspect. But I do think after he passed away, there has been an education aspect: from my grandmother and my father and my aunt, in terms of his legacy and what that meant, and almost a responsibility for that legacy. And that goes a little bit toward having to work twice as hard and how important education is. I think that there was very much a feeling that he had worked so hard to be able to advance Black and African Americans and to be able to provide for his family. HA: It seems like, instead of a hands-on teaching approach, there was more of a legacy of learning.KJ: That’s exactly right. 
 

 
 

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 HA: “Forgotten Genius” offers a perspective of Percy Julian’s career and also suggests that he made lots of friends along the way, including some overseas in Austria, that came to do research with him in the States later on. Are you in touch with any of them?KJ: You know, I actually am in touch with a family friend—she&#x27;s now of advanced age. Her family worked with my grandfather. She now lives in Israel. She travels to the U.S. once a year—well, not in COVID times—usually for competitions. She&#x27;s a scientist herself, and we get together every year when she comes. So there is some of that connection, obviously, because my grandfather now would be very old, and a lot of those connections have now passed. Staying in touch with her [has] really been terrific. And [being] able to hear old stories has been great. 
 

 
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 HA: It’s interesting to think about how Percy Julian had to go out of the country just to get more research and work experience. KJ: And to encounter all of the racism and barriers there—just even to try and live in the community of what he was trying to live—I think required incredible fortitude. HA: My family members are immigrants, and we don’t have that sort of long story of a family legacy in America. It’s more like, “Your parents came here to go to school and they made a life for themselves. Any sort of family history is back in Somalia.” KJ: I see an immigrant&#x27;s story in a way very similar to the way you think back to fortitude. How hard it is to leave everything behind, to go someplace new to try and make a better life—whether it&#x27;s for you or often really for your kids—right? So I see it as very, very similar. I can&#x27;t speak for children of immigrants, but having spoken to several of my friends, I do think they also feel a big responsibility. It&#x27;s like, “Wow, my parents went through all of this for me…I have a responsibility to pay that forward in a way.” HA: We’ve been highlighting <a href="https://www.pbs.org/wgbh/nova/article/inaugural-black-x-weeks-foster-inclusivity-and-empowerment-stem/">&quot;Black in X&quot; weeks at NOVA</a>, talking about what it means to be a Black scientist. Being a physician, do you find yourself having to explain the most basic inequities in health care or STEM to your peers, where you say something like, “I shouldn’t have to tell you this, but I do?”KJ: You know, not so much now. Some of that is a function of the stage I&#x27;m at in my career, [and] where I&#x27;m at, being at UCSF, where I do think people are really looking at <a href="https://www.pbs.org/wgbh/nova/video/covid-19-vaccine/">health equity</a> in a real way and thinking deeply about it. I do feel fortunate that I am not having those conversations in my workplace, at least presently. I have, years and years ago, [but] I do feel that that&#x27;s a marker where I am in terms of change. Because I also recognize that&#x27;s not the case for many, many other people and where they are. The current pandemic has just uncovered so much <a href="https://www.pbs.org/wgbh/nova/article/racism-stress-covid-allostatic-load/">health inequity.</a> And I think people—at least the folks I’m working with—realize that. I do think folks are really looking and thinking about “How can we, as a medical community, make a difference in terms of really trying to eliminate those disparities and help?” This interview has been edited for length and clarity.
 

 
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Katherine Julian, physician and associate dean of graduate medical education at the University of California, San Francisco (UCSF). Image courtesy of UCSF

Dr. Katherine Julian, the granddaughter of famed chemist Percy Julian, discusses her grandfather’s legacy—and how barriers for people of color in science still exist.

A physician on her grandfather’s experience as a minority in STEM—and the state of progress today

Chris Mazurek was a freshman in college when he had a dream that he was inside the <a href="https://www.youtube.com/watch?v=WyzyMcgCS1E">Legends of Zelda</a> video game. He saw himself as the main protagonist, Link, in third person. Suddenly, beeping noises came from inside the game. “That was my cue,” Mazurek says.
 

 
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 In reality, Mazurek was napping on a bed inside a laboratory during his third session of being induced into a lucid dream (in which you are aware, while dreaming, that what you are experiencing is in fact a dream) by a research team at Northwestern University in 2019. He was one of 36 participants in an international experiment that aimed to establish communication between the sleeping and awake. Northwestern’s research team had asked Mazurek to signal to them—while asleep—that he was having a lucid dream. Mazurek was to do this by moving his eyes left to right three times as quickly as he could. The team then asked Mazurek a simple math equation through a speaker: What is eight minus two?Still asleep, he moved his eyes back and forth, and gave “six” as his answer. “Answering them, I was half-dreaming I was in the video game and half where I was still in the lab,” Mazurek says. “When I heard the math problem cue [in the dream], I realized I must still be asleep.” <h3>Dialogue between experimenters and dreamers</h3>On Thursday, Northwestern’s team—along with three other independent teams in France, the Netherlands, and Germany—released their findings suggesting that two-way communication with someone in a lucid dream is possible. Their work, <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(21)00059-2">published Thursday in the journal Current Biology</a>, sheds light on the role lucid dreaming has in communicating with a sleeping person while they’re in the rapid-eye movement (REM) stage of sleep.“My question was: ‘Can the awareness of a lucid dream extend to the outside world?’” says Emma Chabani, study author and member of the Brain and Spine Institute at Sorbonne University in France. “I wanted to know if, during this stage of sleep, it was possible to hear the outside world.”Chabani defines lucid dreaming as the awareness of being in one’s dream, “with reflexive thoughts on [one’s] inner world.” For those who’ve experienced one or more lucid dreams, it can feel as if one’s awake inside their dream—consciously aware that they’re dreaming while remaining asleep.Though the Northwestern and European teams didn’t initially know they were working on the same subject, they eventually began partnering, attempting to streamline their methods. First, the researchers trained study participants to communicate to the researchers with eye movements if they were successful in achieving lucid sleep. These included participants confirming that they were having a lucid dream by answering “yes” when prompted by an audio or visual stimulation. Then, in a total of 56 sessions under electroencephalogram (EEG) measurement, participants were given roughly 90 minutes to nap. The communication tactics involved were <a href="https://www.youtube.com/watch?v=7M06fJxiayo&amp;t=2s">captured in exclusive footage by NOVA’s Greg Kestin</a>, Harvard physicist and host of the YouTube series <a href="https://www.youtube.com/channel/UCj1gfrsi8H8zTrmR0ft1Kjw">What the Physics?!</a> The footage includes electrophysiological signals—both aural and visual signals once REM was confirmed—beginning with Northwestern’s research team asking participants to confirm whether they were having a lucid dream.
 

 
 

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 The Northwestern study participants generally could confirm upon waking that they had lucidly dreamed. But some could not recall what was said or done. How participants did report hearing questions varied; some reported that the questions or cues came from something within the dream—perhaps through a radio or, in Mazurek’s case, a video game—whereas others, upon awakening, misreported the questions they had heard while dreaming. 
 <figure class="richtext-image full-width"><img alt="Mazurek, mid-test, and his EEG composite" class="richtext-image full-width" height="400" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Mazurek_EEG_composite_16x9.width-800.jpg"/><figcaption>Mazurek, mid-test, and his EEG composite, Image courtesy of Stephanie Kulke, Northwestern University<div class="credit"></div></figcaption>
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 Researchers call the initial cue, asking the sleeper to confirm they were in a lucid dream, the “reality check.” For Mazurek, that took place in Legends of Zelda. For another subject, as depicted in Kestin’s documentary, the “reality check” appeared as flashing lights upon her dreamed-up childhood house. The flashing lights were, in reality, coming from inside the laboratory room while she slept.
 

 
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 <h3>Lucid dreaming, particularly, makes two-way communication possible</h3>The REM stage of sleep has <a href="https://www.ncbi.nlm.nih.gov/books/NBK11121/">long been studied</a> as the key area for dreaming. Because of its role in dreaming, the REM stage, previous research has found, is also a key element to allowing for successful two-way communication between an asleep person and an awake one. But it’s just now that Chabani and her colleagues are discovering the potentially essential role that lucidity has in complex communication between the sleeping and the awake. Although <a href="https://www.researchgate.net/publication/260761277_Asleep_but_aware">previous studies</a> have suggested that communication to a sleeping person can cause a physical response (such as finger tapping), this study is the first to illustrate not only more complex communication (questions and answers) but recollection upon awakening. Of the 57 total reported napping sessions conducted by all four research teams, 26% of the sessions resulted in a confirmed lucid dream. In almost half of those lucid dream sessions, participants answered at least one of the experimenters’ questions correctly. In sessions where participants failed to signal they were experiencing a lucid dream, most participants also failed to respond to any of the researchers&#x27; other questions. Lucid dreaming, Chabani says, was the key to opening dreamers to receiving information, in that it allows sleepers to be more aware of the external world.However, that meant that the stimulations from researchers—and the pre-sleep training—were key to bridging the distance between sleep and the external world created by REM-stage sleep.“To be aware of external stimulation,” Chabani says, “the stimulation has to be clear enough and your attention must be directed to [it].”Even before participating in the study, Mazurek had wanted to learn how to lucidly dream. But he found it difficult until his third and final session. “During the first trial,” he says, “the lucid dream quickly fell apart” after cueing from the experimenters. More exposure and training throughout the experiment, Mazurek says, gave him an “awareness” he believes is key to reaching a lucid state while dreaming.Studies comparing subjects who have frequent lucid dreams to those who have had infrequent ones have found no difference between the psychology of subjects, she says. But they have identified differences in creativity and “metacognitions,” or one’s awareness of one’s own thoughts. “It is possible lucid dreaming is easier with the number of lucid dreams,” Chabani says. Increased creative thinking may help a sleeping person reach the lucid dreaming state, Chabani adds. <h3>The scientific—and recreational—applications of lucid dreaming</h3>Chelsea Mackey, a clinical psychology Ph.D. student at the University of Washington who was not involved in the study, finds the research to be an important contribution to neuroscience and to the idea of “interactive dreaming.” “It aids our understanding of the complexity of sleep and dreams by integrating novel approaches to the study of two-way communication during sleep,” Mackey says. “It has critical implications for health and well-being.”Now a junior at Northwestern majoring in neuroscience, Mazurek is working in the lab of study author Ken Paller. Paller and his team have developed a smartphone app called <a href="https://pallerlab.psych.northwestern.edu/dream">Lucid</a>, which trains users to achieve lucidity while asleep in a similar manner to Northwestern’s study participants. Once turned on, the app will wait six hours. Then, in an attempt to induce lucid dreaming in its user, it will play preset soft noises. Users are asked to fill out a dream report upon waking up to record their experiences.Mazurek and his teammates are working on the second version of the app, which they’re hoping to release in April. The early results have been promising: App users tend to have lucid dreams more often than other people, Mazurek explains. And the app increases lucid dreaming induction in 40% of its users, he says.Historically, dream reporting has been fraught with difficulty, as many people cannot reliably or coherently recall a dream after waking up. That makes the ability to communicate with a person while they’re still sleeping so promising, Chabani believes. If we see something on a physiological level in a study participant that’s interesting, such as an acceleration in their heart rate, “we could ask a subject what is happening,” she says. Her team’s new study, Chabani hopes, can offer new insight into—and a better understanding of—the dreaming world. Mackey agrees that the findings of the study are promising. While there is still a significant amount of work to be done in this area, she says, “this study does represent substantial progress toward identifying ways to leverage and gain valuable information from lucid dreams. I am thrilled to see future progressions on this topic.”“If we’re able to get a technique down for lucid dream induction, the applications are wild and limitless,” Mazurek says. “There are a lot of different applications, whether lucid dreaming therapy or recreational enjoyment...I think it’s a bright future ahead.”Hanna Ali contributing to the reporting of this story.
 

 
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The study's first author, Karen Konkoly, watches a laboratory monitor. Image courtesy of Stephanie Kulke, Northwestern University

A study from four independent teams report that lucid dreaming during the REM sleep stage allows for two-way communication.

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