The fading of a once-vibrant yellow rose reveals how the ravages of time and chemical alteration can dampen the visual power of a painting.
Most of the flowers in Abraham Mignon’s 17th century painting Still Life with Flowers and a Watch seem to leap off the canvas. But one yellow rose, painted with arsenic sulfide–based orpiment pigment, is a flat, jarring element. That wasn’t Mignon’s intention: The rose lost its luster due to the chemical transformation of some of its original bright pigment into colorless lead arsenates, researchers report June 8 in Science Advances. Paintings conservator Nouchka De Keyser of the Rijksmuseum in Amsterdam and colleagues analyzed the rose using noninvasive techniques including X-ray fluorescence imaging and X-ray powder diffraction (SN: 10/1/21). The team first mapped the lingering traces of arsenic, lead, calcium and other chemical elements in the layers of paint to reveal how Mignon carefully layered paint to create a nearly three-dimensional rose out of light and shadow.
The analyses also revealed two newer crystals on the rose containing both lead and arsenic. Called mimetite and schultenite, the crystals are the product of a series of chemical reactions. First, the reaction of orpiment with light created a highly mobile type of arsenic called arsenolite. That mobilized arsenolite then found its way to an underlying layer of lead white paint and chemically reacted with it to produce the mimetite and schultenite. The crystals lack the bright color of the orpiment — instead, they are colorless and flatten the flower’s appearance. Science can’t turn back the clock on the chemical transformation to restore the rose’s erstwhile glory — that’s a one-way street. But digital reconstructions made using similar techniques as in the new study could offer several benefits and not just to scientists and art historians, De Keyser says. Not only can such reconstructions reveal now-faded elements in other paintings — they might also appear in museums, allowing visitors a ghostly glimpse of a painting’s true past.
For the last two years, a person acting erratically in downtown Denver has likely first encountered unarmed health care workers rather than police. That shift stems from the rollout of a program known as Support Team Assisted Response, or STAR, which sends a mental health clinician and paramedic to respond to certain 911 calls about nonviolent behavior.
The program, and others like it, aim to defuse the tensions that can arise when police officers confront civilians in distress. Critics of these experimental programs have suggested that such reduced police involvement could allow crime to flourish. Now, researchers have found that during its pilot phase, the STAR program did not appear to lead to more violent crime. And reports of minor crimes substantially decreased, the researchers conclude June 8 in Science Advances. Much of that reduction occurred because the health responders do not issue citations or make arrests (SN: 12/18/21). But even that reduction in reported crime is beneficial, says economist Thomas Dee of Stanford University. “That person is getting health care instead of being arrested.”
Following the death of George Floyd at the hands of a white police officer and the subsequent rise of the Black Lives Matter movement in the summer of 2020, cities throughout the country have been rolling out programs like STAR. “We cannot police our way out of every social problem,” says Temitope Oriola, a sociologist at the University of Alberta in Edmonton, Canada. But so far there have been few studies of these programs’ effects on crime, let alone on the reduction of violence between police and the public (SN: 7/9/20).
Dee and Jayme Pyne, a sociologist also at Stanford, looked at the STAR program’s impact on crime reports. The duo investigated the program’s pilot phase, which ran from June to November 2020 and encompassed eight of the city’s 36 police precincts. Police officers and 911 operators in those eight precincts redirected calls for minor and non-dangerous complaints to STAR providers. These calls included concerns about trespassing, indecent exposure, intoxication and similar low-level offenses. During the six-month pilot, STAR providers responded to 748 calls, averaging roughly six incidents per eight-hour shift.
Dee and Pyne analyzed criminal offenses in all 36 precincts from December 2019 to November 2020. They then compared the change in crime rates in the eight precincts receiving STAR services with the change in crime rates in the other 28 precincts. The rate of violent crime remained unchanged across the board, including in the precincts where the STAR program was active, the researchers found. But there was a 34 percent drop in reports of minor offenses in the STAR precincts, from an average of about 84 offenses per month in each district to an average of about 56 citations.
The data also suggest that the actual level of minor crimes and complaints dropped too — that is, the drop wasn’t just due to a lack of reporting, the researchers say. Prior to the pilot, minor offenses in the eight precincts receiving STAR services resulted in an average of 1.4 citations per incident. So having health care workers rather than police respond to 748 such calls should generate roughly 1,000 fewer citations, the authors calculate. Instead, citations dropped by almost 1,400. Providing people in crisis with access to health services may be preventing them from reoffending, Dee says.
Research into these sorts of programs is crucial, says Michael Vermeer, a justice policy researcher with the RAND Corporation, a public policy research organization headquartered in Santa Monica, Calif. But he cautions against drawing firm conclusions from a single study launched at the onset of the COVID-19 crisis, which dramatically changed crime rates and patterns across the country. “They just got confounded by the pandemic,” Vermeer says.
Dee agrees that he and other researchers now need to replicate this study across more cities, and also scale up in Denver. The city has since expanded the STAR program beyond the initial pilot.
Even if researchers eventually find that STAR and similar programs don’t budge crime rates much, that doesn’t mean that the programs are unsuccessful, says sociologist Brenden Beck of the University of Colorado Denver. He points to the potential to save taxpayer dollars. Dee and Pyne estimate that a single offense processed through STAR costs about $150, compared with the roughly $600 it costs to process one through the criminal justice system.
What’s more, helping people having nonviolent mental health crises get help and stay out of jail lets these individuals hold onto their jobs and stay present in their family members’ lives, Beck says. “I would hope we as a research community move on to study the benefit of these programs not just in terms of crime but also in terms of human welfare.”
Nuclear submarines might provide rogue nations with a path to nuclear weapons. But neutrinos could help reveal attempts to go from boats to bombs.
Neutrinos, lightweight subatomic particles that are released from the reactors that power nuclear subs, could expose the alteration or removal of the nuclear fuel for nefarious purposes, physicists report in a paper accepted in Physical Review Letters. Crucially, this monitoring could be done remotely, while a submarine is in a port with its reactor shut off. To ensure that countries without nuclear weapons don’t develop them, international inspectors monitor the use of many types of nuclear technology around the world. Nuclear submarines are particularly worrisome. Many use highly enriched uranium, a potent type of fuel that can be weaponized relatively easily. But submarines are protected from monitoring by a loophole. Unlike nuclear power plants, nuclear submarines are used for secretive military purposes, so physical inspections could infringe on a country’s national security.
“Neutrino-based methods can considerably reduce the intrusiveness by making measurements at a distance, without having to physically access the vessel,” says nuclear scientist Igor Jovanovic of the University of Michigan in Ann Arbor, who was not involved with the research.
These particles — specifically their antimatter variety, antineutrinos — stream in droves from operating nuclear reactors. The particles interact feebly with other matter, allowing them to pass through solid material, including a submarine hull. So a neutrino detector placed near a submarine could reveal what’s going on inside, say neutrino physicists Bernadette Cogswell and Patrick Huber of the Center for Neutrino Physics at Virginia Tech in Blacksburg.
Scientists have previously suggested using neutrinos to detect other nuclear misdeeds, such as nuclear weapons tests (SN: 8/20/18).
But submarines, often on the move, are hard to monitor with stationary instruments. When the vessels do sit in port, their nuclear reactors may be turned off. So the researchers came up with a solution: They’d look at neutrinos produced by the decays of varieties of chemical elements, or isotopes, that remain after a reactor shuts down. A detector located in the water about 5 meters underneath the sub’s reactor could measure neutrinos produced in decays of certain cerium and ruthenium isotopes. Those measurements would reveal if nuclear material had been removed or swapped out.
This method of monitoring a reactor that’s off is “very clever,” says physicist Ferenc Dalnoki-Veress of the Middlebury Institute of International Studies at Monterey in California.
But the idea would still require buy-in from each country to agree to detectors in submarine berths. “Something like this would be so much better if it wouldn’t require cooperation,” says physicist Giorgio Gratta of Stanford University.
Submarine monitoring may become more pressing in the near future. So far, all countries that have nuclear submarines already possess nuclear weapons, so the issue was hypothetical. But that’s set to change. The United States and the United Kingdom, two nuclear weapons states, announced last September that they are entering into a cooperative security agreement with Australia and will help the country, a non-nuclear weapons state, acquire nuclear submarines.
There’s little suspicion that Australia would use these submarines as a cover for a nuclear weapons program. But “you still have to worry about the precedent that that sets,” Cogswell says. So, she says, monitoring nuclear submarines is newly important. “The question was how the heck to do that.”
In a large laboratory cage, a male mosquito carries a genetic weapon that could launch the destruction of his species. That loss could also mean the end of the parasite that causes malaria.
The weapon, a self-replicating bit of DNA known as a gene drive, is one of the most anticipated and controversial tools being developed to stop mosquitoes from spreading diseases like malaria to humans.
The gene drive interferes with the insects’ ability to reproduce. It wiped out captive populations of mosquitoes in eight to 12 generations (SN: 10/27/18, p. 6) in a small lab study. In 2021, the technology worked in the large cages in Terni, Italy, too. Within as little as five to 10 years, this gene drive could be ready to test in the wild.
The first experimental release could be rolled out in Burkina Faso, Mali, Ghana or Uganda. In those locations, researchers are working with a nonprofit research consortium called Target Malaria to develop the gene drive carriers along with other genetically engineered mosquitoes to fight malaria.
This research is driven by the idea that every tool available must be used to fight malaria, which sickened close to 241 million people in 2020 and killed 670,000 worldwide, mostly in Africa. Children 5 years old and younger accounted for about 80 percent of the continent’s malaria deaths, the World Health Organization says.
Because of malaria’s huge toll, large investments have been made to fight the disease, yielding preventive drugs, insecticide-treated bed nets and even malaria vaccines — one was recently recommended for use in sub-Saharan Africa (SN: 12/18/21 & 1/1/22, p. 32). These efforts are helping. But mosquitoes are developing resistance to insecticides, and some anti-malaria drugs may no longer work well.
“To go toward zero [cases], we need to have something that is transformational,” says Fredros Okumu, a mosquito biologist and director of science at Ifakara Health Institute in Tanzania. Gene drives might be the transformational answer people are looking for. Researchers are still refining and testing the technology, which was first devised in 2015 (SN: 12/12/15, p. 16). Though other types of genetically altered mosquitoes have been released in Brazil, the United States and elsewhere, those altered genes spread slowly among wild populations (SN Online: 3/9/22). Gene drives could potentially spread to nearly ever member of a species quickly, forever altering the species or wiping it out.
But whether gene drives ever play a role in combating malaria may depend as much on social considerations as on science.
“A technology doesn’t work by technical strength alone. It works because it embeds into a social context,” says Ramya Rajagopalan, a social scientist at the University of California, San Diego. In the past, scientists “developed a technology in the lab, got it all set up and ready to go, and then you go to the stakeholders and say, ‘Hey, we have this great technology, do you want to use it?’ ”
If people reject that sort of offer, as has happened with some genetically modified crops, researchers often think, “If [the public] only knew enough about the technology, they’d be more accepting,” Rajagopalan says. But more often the failure comes because the researchers “don’t include community voices from the outset in the design and the implementation.”
Because of the possibility of forever altering ecosystems, the European Union has already said “no” to using gene drives there. But Africa is where a gene drive might one day help defeat malaria. Researchers are hoping to eventually release gene drives on the continent, but must first get public consensus. To that end, scientists are looking for ways to involve members of the public in research, and learn about local priorities and how to talk about the technology.
Rattling the cage No one is ready to let mosquitoes carrying gene drives out of the lab yet. For now, researchers are doing tests with mosquitoes in captivity to get an idea of whether the technology will work as planned. In the Terni cage trials, scientists used small rooms, setting humidity levels, lighting and other characteristics to mimic some of the conditions the mosquitoes might encounter in the wild.
In cages almost 5 cubic meters big — about the size of a small dressing room — containing hundreds of Anopheles gambiae mosquitoes, scientists added male members of the same species that carried the engineered change to their DNA.
The gene drive used for this experiment is built on the molecular scissors known as CRISPR/Cas9. Male mosquitoes are engineered to carry the gene drive, which consists of instructions for making the DNA-cutting enzyme Cas9 and an RNA that guides the enzyme to the gene to be cut. When an engineered male mates with an unaltered female, Cas9 snips a gene called doublesex inside the fertilized egg. As the egg tries to repair the cut, the gene drive from the father’s doublesex gene is pasted over the copy of the gene inherited from the mother. So the offspring gets two copies of the gene drive, instead of one.
Normally, any particular version of a gene has a 50 percent chance of being passed from parent to offspring. But with the copy-and-paste CRISPR system, gene drive–carrying mosquitoes pass the drive to about 96 percent of male progeny and more than 99 percent of females. With that genetic cheat, the gene drive spreads rapidly through the population. The doublesex gene is essential for the development of female mosquitoes. When the gene doesn’t work, “the mosquito itself doesn’t work,” says Ruth Müller, chief ecologist and entomologist at the Institute of Tropical Medicine in Antwerp, Belgium. The gene drive breaks the gene.
Female offspring that inherit two copies of a broken doublesex gene develop mouthparts and genitalia that are closer to the male form. Those females are sterile, and they cannot bite people with their malformed mouthparts. Unable to bite, those mosquitoes can’t transmit malaria-causing parasites from their bodies to humans.
In those naturelike cages in Terni, when gene drive–carrying mosquitoes were introduced, the populations died out in 245 to 311 days, researchers reported in July 2021 in Nature Communications. In two cages where no gene drive mosquitoes were added, mosquito populations lived normally to the end of the experiment.
This was the first proof that the gene drive might work under almost real-world conditions, says Müller, one of the study’s leaders. But there is still a lot to learn about drives, she says, including how they will affect mosquito populations in the wild, whether they can slow malaria’s spread and importantly, what the impact will be on other creatures in the environment.
Getting those answers will determine the feasibility of moving forward scientifically. They will also play a big role in whether the public agrees to releasing a tool that could intentionally drive a species toward extinction. Considering all possibilities While Müller’s and other Target Malaria science teams based in Africa, Europe and North America refine gene drives, other affiliated and independent groups are mapping out what releasing a gene drive could do to the planet. “Right now there are a lot of theoretical discussions,” Müller says. It’s important to gather data to “fill the debate with more facts” about the real risks and benefits, she says.
At least 46 theoretical harms could arise from the use of gene drives on mosquitoes, researchers reported in March 2021 in Malaria Journal. Those potential downsides include reductions in pollinators and other species directly or indirectly related to the disappearance of the mosquitoes. It’s possible that people could develop allergic reactions to the bite of mosquitoes carrying a single copy of the gene drive, or to fish that eat the altered mosquito larvae. There could be a decline in water quality caused by large numbers of mosquito larvae dying. There’s even a set of scenarios in which malaria cases increase if, for instance, mosquito species that are better malaria spreaders take over in areas where a gene drive has thinned out less-troublesome mosquitoes.
Dreaming up possible nightmare consequences was an exercise intended to tell researchers what they might need to plan for and test before releasing gene drive mosquitoes into the wild. At workshops held in 2016 through 2019 in Ghana, Kenya, Botswana, Gabon and the United States, researchers worked out a chain of events that might lead to each of those potential harms.
The list of 46 possibilities focused on four areas that African leaders said were most important to protect: biodiversity, human and animal health, and water quality. By identifying these hypothetical hazards, researchers can begin calculating the likelihood of a harm happening and how bad it could be, says report coauthor John Connolly, a senior regulatory scientist for Target Malaria who is based at Imperial College London.
“You probably never really finish a risk assessment, but you get a clearer understanding of the risks and uncertainties,” Connolly says. Target Malaria and independent groups hope to answer some questions by examining data collected from the release of genetically altered mosquitoes that don’t carry gene drives.
Studies of biological pest control mechanisms — such as releasing a predator to eradicate an invasive species (remember invasive cane toads in Australia [SN Online: 10/14/14]) — may also provide some clues about how gene drives may spread, says Keith Hayes, who leads a risk assessment team at the Commonwealth Science and Industrial Research Organization’s Data61 in Hobart, Australia.
Some questions may never truly be answered unless gene drives are released. Scientists can experiment and simulate what might happen, but “at some point you have to say, ‘We don’t know everything. We can’t know everything. There may be surprises,’ ” Hayes says. That’s when a decision will need to be made about a release based on what is known about the risks and benefits.
High stakes Even if those evaluations reveal downsides to gene drives, the potential benefits for human health and economics may far outweigh the risks, Müller argues.
“If you have a high burden of malaria, that costs a lot,” Müller says. “Children cannot go to school. People cannot go to work. That should also be considered if you talk about costs.”
Opponents of gene drives say it’s unfair to paint rejection of the unproven, potentially dangerous, technology as dooming children to death from malaria. “We are already not saving those children with measures [that would help] such as improving sanitation and the medical system,” says Mareike Imken, the European coordinator of the Stop Gene Drives campaign. Her organization is calling for a global moratorium on the release of gene drives until there is worldwide consensus on whether they are safe and necessary and how they should be regulated.
“We need the highest possible obstacle to using this high-risk … technology,” Imken says. Allowing gene drives to be tried against malaria would essentially unleash them for use against a wide variety of organisms, with potentially devastating ecological consequences, she says. Instead, the world should invest more in already proven methods of controlling and eradicating malaria.
But there are potential upsides to gene drives that current approaches, such as insecticides, don’t offer. “The stuff we have been doing for years has been intentionally designed to eradicate mosquitoes. It just didn’t do it. We’ve been spraying the hell out of them for years, and in the process killing a lot of other nontarget organisms,” Okumu says.
By replacing insecticides, gene drives might help save insects including bees, butterflies and other pollinators. And gene drives are designed to eliminate only the mosquito species that are dangerous, Okumu says. “Of all the 3,500 species … we need to target one, two, at maximum three of them.”
He’s referring to the handful of species in the Anopheles genus that are mostly responsible for spreading malaria. In Africa, the primary disease carriers are Anopheles gambiae and the look-alikes An. arabiensis, An. coluzzii and An. funestus.
While eradicating malaria is the goal, making mosquitoes extinct is mostly hyperbole, says Tony Nolan, a molecular biologist at the Liverpool School of Tropical Medicine in England.
“Extinction is not a likely outcome, nor even a desirable one. It’s not necessary to make the mosquito extinct to eliminate malaria,” says Nolan, one of the Target Malaria researchers developing gene drives. Geographic isolation may enable the gene drive to eliminate a local population of mosquitoes but nothing further afield. Mutations can arise in the Cas9 or guide RNA, causing the drive to stop working. Or other things might limit its spread.
But what would happen to the environment if a major mosquito species suddenly disappeared? Some researchers are trying to measure the ecological contributions of An. gambiae, including whether males pollinate plants visited for nectar. As of now, the mosquitoes’ biggest known value is as food for predators. Birds, fish and other animals that eat mosquitoes or their larvae usually aren’t picky about which species is for dinner. Only one species of spider is known to prefer Anopheles mosquitoes over other kinds.
Okumu’s experience leads him to think the malaria carriers wouldn’t be missed much. In some parts of eastern Africa, including Okumu’s home village in Tanzania, a combination of factors including prolonged dry seasons and insecticide and bed net use pushed An. gambiae out. “We have not seen — maybe because we didn’t measure [well enough] — any ecological challenges associated with the disappearance of Anopheles gambiae,” he says.
The mix of malaria carriers can vary considerably depending on local conditions. In Burkina Faso in western Africa, for instance, two villages had different mosquito populations: In Bana, to the northwest of the city Bobo-Dioulasso, about 90 percent of mosquitoes were An. coluzzii with An. gambiae making up 9 percent of the catch, researchers reported in 2019 in Malaria Journal. But on the southeastern side of the city, in the village of Pala, An. gambiae dominated, making up about 84 percent of mosquitoes caught. An. arabiensis accounted for about 10 percent, and An. coluzzii was about 6 percent of the catch in Pala.
If An. gambiae disappeared, one of the other species would fill the vacuum, Okumu says. That could be a good thing if the replacements don’t bite people as much or are lousy at spreading malaria. It could also be worse if the balance shifts toward a more voracious people-biter that easily spreads the parasites. Community input Beyond the scientific hurdles, researchers must also get the public on board with releasing the technology. Without public support, even a gene drive that works perfectly could be a no-go.
Not everyone agrees on when and how to get input. Okumu worries that asking the public whether they want gene drives before scientists have answers to some of the most pressing questions could backfire. “I would rather we know the true benefits, the true risks and gain a consensus around it, and then start engaging the communities,” he says.
Waiting until all the answers are in hand is a flawed approach, says Lea Pare Toe, a social scientist at the Institut de Recherche en Sciences de la Santé in Bobo-Dioulasso. “We should listen to [the community] and develop the science together,” says Toe, who works with Target Malaria to engage local people in the research.
At Bana, researchers didn’t start out talking about gene drives, or even genetic modifications, Toe says. First, the team had to clarify the connection between mosquitoes and malaria. They also had to dispel myths, such as eating fatty foods or sweet fruit can cause the disease. After an intensive engagement campaign from 2014 through 2019, researchers found that such false statements were far less accepted, the researchers reported in October 2021 in Malaria Journal. Once people are clear on the causes of malaria, Toe and colleagues introduce the idea of genetics, and how researchers want to alter mosquitoes to combat malaria. People are generally OK with the uncertainty of research, she says. But they want to know more.
Residents pose specific questions about mosquito biology and ask how researchers can possibly work with such small creatures. They often ask whether the genetic alterations that make the mosquitoes sterile will transfer to humans. People “love the details,” Toe says.
Sometimes, creative approaches are needed to get concepts across. For instance, Target Malaria planned a first stage — releasing genetically sterilized male mosquitoes that won’t diminish mosquito populations — to help researchers collect data on how genetically altered mosquitoes stack up to normal ones in the wild.
Before those altered mosquitoes were set free, the organization wanted to ensure that Bana residents had a deep understanding of the project. Local leaders suggested a play. The scientists wrote a script, but the actors, a local storyteller and other community members revised it to improve storytelling. This helped forge an emotional connection with the audience, Toe and colleagues reported April 5 in Humanities and Social Sciences Communications. Meanwhile in Tanzania, although reluctant to move too soon with the public, Okumu and colleagues talked with community leaders and surveyed residents of 10 villages in the southeastern part of the country, where very few people had heard about genetically modifying mosquitoes. The aim of this 2019 effort was to understand community perceptions, rather than ask permission. People were intrigued by the idea of gene drives, but they had concerns about whether the mosquitoes would look and behave differently from local mosquitoes, the team reported in March 2021 in Malaria Journal.
Community members were also skeptical that targeting just one type of mosquito would be enough to reduce malaria transmission or decrease mosquito bites enough to keep communities on board with the project. It would be better, they said, to get rid of all the biting mosquitoes.
In a separate study done in 2019, people in Uganda who were already familiar with gene drives expressed similar concerns. But those participants anticipated problems if the mosquitoes cross national borders into a country opposed to the release, researchers reported in March 2021 in Malaria Journal. Researchers may have to seek permission to release gene drive mosquitoes on a multinational scale, instead of just getting local and national consent.
Gene drives may win hearts and minds because they will first be tried against disease-carrying mosquitoes “that are very, very much not beloved or charismatic or anything,” says developmental geneticist Kimberly Cooper of UC San Diego. “Do you know anyone who has sympathies for the mosquito? It’s probably the most hated animal on the planet.
“But there will always be people who are very concerned about genetically modified organisms and their release into the environment,” even if those organisms are mosquitoes, says Cooper, who is not involved with the malaria gene drive research but is developing a gene drive to use as a research tool in mice (SN Online: 1/23/19).
Still, the attraction of stamping out malaria is powerful. The benefits could be enormous. But whether they outweigh any environmental risks from the technology and whether the public will buy in to this radical approach remains to be seen.
“There are tons of unknowns,” Okumu says. “The question is, should we pursue it? If you ask me, it would be unethical not to.”
The undoing of toxic “forever chemicals” may be found in products in your pantry.
Perfluoroalkyl and polyfluoroalkyl substances, also known as PFAS, can persist in the environment for centuries. While the health impacts of only a fraction of the thousands of different types of PFAS have been studied, research has linked exposure to high levels of some of these widespread, humanmade chemicals to health issues such as cancer and reproductive problems.
Now, a study shows that the combination of ultraviolet light and a couple of common chemicals can break down nearly all the PFAS in a concentrated solution in just hours. The process involves blasting UV radiation at a solution containing PFAS and iodide, which is often added to table salt, and sulfite, a common food preservative, researchers report in the March 15 Environmental Science & Technology. “They show that when [iodide and sulfite] are combined, the system becomes a lot more efficient,” says Garrett McKay, an environmental chemist at Texas A&M University in College Station who was not involved in the study. “It’s a big step forward.”
A PFAS molecule contains a chain of carbon atoms that are bonded to fluorine atoms. The carbon-fluorine bond is one the strongest known chemical bonds. This sticky bond makes PFAS useful for many applications, such as water- and oil-repellant coatings, firefighting foams and cosmetics (SN: 6/4/19; SN: 6/15/21). Owing to their widespread use and longevity, PFAS have been detected in soils, food and even drinking water. The U.S. Environmental Protection Agency sets healthy advisory levels for PFOA and PFOS — two common types of PFAS — at 70 parts per trillion.
Treatment facilities can filter PFAS out of water using technologies such as activated carbon filters or ion exchange resins. But these removal processes concentrate PFAS into a waste that requires a lot of energy and resources to destroy, says study coauthor Jinyong Liu, an environmental chemist at the University of California, Riverside. “If we don’t [destroy this waste], there will be secondary contamination concerns.”
One of the most well-studied ways to degrade PFAS involves mixing them into a solution with sulfite and then blasting the mixture with UV rays. The radiation rips electrons from the sulfite, which then move around, snipping the stubborn carbon-fluorine bonds and thereby breaking down the molecules.
But some PFAS, such as a type known as PFBS, have proven difficult to degrade this way. Liu and his colleagues irradiated a solution containing PFBS and sulfite for an entire day, only to find that less than half of the pollutant in the solution had broken down. Achieving higher levels of degradation required more time and additional sulfite to be poured in at spaced intervals.
The researchers knew that iodide exposed to UV radiation produces more bond-cutting electrons than sulfite. And previous research has demonstrated that UV irradiation paired with iodide alone could be used to degrade PFAS chemicals.
So Liu and his colleagues blasted UV rays at a solution containing PFBS, iodide and sulfite. To the researchers’ surprise, after 24 hours of irradiation, less than 1 percent of the stubborn PFBS remained.
What’s more, the researchers showed that the process destroyed other types of PFAS with similar efficiency and was also effective when PFAS concentrations were 10 times that which UV light and sulfite alone could degrade. And by adding iodide the researchers found that they could speed up the reaction, Liu says, making the process that much more energy efficient.
In the solution, iodide and sulfite worked together to sustain the destruction of PFAS molecules, Liu explains. When UV rays release an electron from iodide, that iodide is converted into a reactive molecule which may then recapture freed electrons. But here sulfite can step in and bond with these reactive molecules and with electron-scavenging oxygen in the solution. This sulfite “trap” helps keep the released electrons free to cut apart PFAS molecules for eight times longer than if sulfite wasn’t there, the researchers report.
It’s surprising that no one had demonstrated the effectiveness of using sulfite with iodide to degrade PFAS before, McKay says.
Liu and his colleagues are now collaborating with an engineering company, using their new process to treat PFAS in a concentrated waste stream. The pilot test will conclude in about two years.
U.S. and Soviet leaders … signed agreements on space, science and technology, health and the environment…. The space agreement … outlines plans for cooperation in fields such as meteorology, study of the natural environment, planetary exploration and space biology.
Update The 1972 space agreement led to the first international human spaceflight, the Apollo-Soyuz mission, during which Soviet and U.S. crews socialized in space (SN: 7/26/75, p. 52). Apollo-Soyuz encouraged decades of collaboration that continues today on the International Space Station. Now, Russia’s war in Ukraine has prompted many countries to pull back on scientific endeavors with Russia, in space and on Earth (SN: 3/26/22, p. 6). While NASA remains committed to the space station, the head of Russia’s space agency has threatened to end the cooperation in retaliation for sanctions imposed in response to the war. Russia has yet to make moves to abandon the station, though the country has ceased supplying rocket engines to the United States.
