Modern-day Melanesians carry a two-pronged genetic legacy of ancient interbreeding that still affects their health and well-being, researchers say.

Unlike people elsewhere in the world, these Pacific islanders possess nuclear DNA that they inherited from two Stone Age hominid populations, say population geneticist Benjamin Vernot, formerly of the University of Washington in Seattle, and his colleagues. At least some of that ancient DNA contains genes involved in important biological functions, the researchers find. Nuclear DNA is passed from both parents to their children.
The finding means that ancestors of people now living in the Bismarck Archipelago, a group of islands off Papua New Guinea’s northeastern coast, mated with Neandertals as well as with mysterious Neandertal relatives called Denisovans, the scientists conclude online March 17 in Science.

In support of previous research, the researchers find that non-Africans — including Melanesians — have inherited an average of between 1.5 and 4 percent of their DNA from Neandertals. But only Melanesians display substantial Denisovan ancestry, which makes up 1.9 to 3.4 percent of their DNA, the researchers say. (Present-day African populations possess little to no Neandertal or Denisovan DNA.)

The bits of Neandertal and Denisovan DNA carried by Melanesians encompass genes involved in metabolism and immunity, indicating that interbreeding influenced the evolutionary success of ancient humans, Vernot’s group reports.

The new study reconstructs the microscopic landscape of Neandertals’ and Denisovans’ contributions to Melanesians’ DNA “in impressive detail,” says Harvard University paleogeneticist Pontus Skoglund.

Vernot’s team studied DNA from 35 Melanesians at 11 locations in the Bismarck Archipelago. Analyses concentrated on DNA from 27 unrelated individuals. The researchers also looked for evidence of ancient interbreeding in previously acquired genomes of close to 1,500 modern-day individuals from different parts of the world. Denisovan DNA for comparisons came from fragmentary fossils found in a Siberian cave; comparative Neandertal DNA came from a genome previously extracted from a 50,000-year-old woman’s toe bone.
Among Melanesians, DNA sequences attributed to Neandertals and Denisovans encompassed several metabolism genes. One of those genes influences a hormone that increases blood glucose levels. Another affects the chemical breakdown of lipids. Other Melanesian genetic sequences acquired through ancient interbreeding either include or adjoin genes that help to marshal the body’s defenses against illness.

These findings follow evidence suggesting that once-useful genes that ancient humans inherited from Neandertals now raise the risk of contracting certain diseases (SN: 3/5/16, p. 18). Vernot’s group reaches no conclusions about good or bad effects of ancient hybrid genes in Melanesians.

No sign of Neandertal or Denisovan DNA appears in areas of Melanesians’ genomes involved in brain development, the scientists say. So brain genetics, for better or worse, apparently evolved along a purely human path.

Denisovans’ evolutionary history remains poorly understood. Previous DNA comparisons suggest that Denisovans must have reached Southeast Asia. Skoglund suspects that’s where the ancestors of Melanesians bred with Denisovans.

Substantial interbreeding of humans with Denisovans probably occurred only once, Vernot and his colleagues suspect. Genetic exchanges of humans with Neandertals took place at least three times, they add. These estimates are derived from comparisons of shared Denisovan and Neandertal DNA sequences among individuals in different parts of the world.

The 22 men took the same pill for four weeks. When interviewed, they said they felt less daily stress and their memories were sharper. The brain benefits were subtle, but the results, reported at last year’s annual meeting of the Society for Neuroscience, got attention. That’s because the pills were not a precise chemical formula synthesized by the pharmaceutical industry.

The capsules were brimming with bacteria.

In the ultimate PR turnaround, once-dreaded bacteria are being welcomed as health heroes. People gobble them up in probiotic yogurts, swallow pills packed with billions of bugs and recoil from hand sanitizers. Helping us nurture the microbial gardens in and on our bodies has become big business, judging by grocery store shelves.
These bacteria are possibly working at more than just keeping our bodies healthy: They may be changing our minds. Recent studies have begun turning up tantalizing hints about how the bacteria living in the gut can alter the way the brain works. These findings raise a question with profound implications for mental health: Can we soothe our brains by cultivating our bacteria?
By tinkering with the gut’s bacterial residents, scientists have changed the behavior of lab animals and small numbers of people. Microbial meddling has turned anxious mice bold and shy mice social. Rats inoculated with bacteria from depressed people develop signs of depression themselves. And small studies of people suggest that eating specific kinds of bacteria may change brain activity and ease anxiety. Because gut bacteria can make the very chemicals that brain cells use to communicate, the idea makes a certain amount of sense.

Though preliminary, such results suggest that the right bacteria in your gut could brighten mood and perhaps even combat pernicious mental disorders including anxiety and depression. The wrong microbes, however, might lead in a darker direction.
This perspective might sound a little too much like our minds are being controlled by our bacterial overlords. But consider this: Microbes have been with us since even before we were humans. Human and bacterial cells evolved together, like a pair of entwined trees, growing and adapting into a (mostly) harmonious ecosystem.

Our microbes (known collectively as the microbiome) are “so innate in who we are,” says gastroenterologist Kirsten Tillisch of UCLA. It’s easy to imagine that “they’re controlling us, or we’re controlling them.” But it’s becoming increasingly clear that no one is in charge. Instead, “it’s a conversation that our bodies are having with our microbiome,” Tillisch says.

Figuring out what’s being said in this body-microbe exchange, and how to shift the tone in a way that improves mental health, won’t be easy. For starters, no one knows the exact ingredients for a healthy microbial community, and the recipe probably differs from person to person. And it’s not always simple to deliver microbes to the gut and persuade them to stay. Nor is it clear how messages travel between microbes and brain, though scientists have some ideas.

It’s early days, but so far, the results are compelling, says neuro­scientist John Cryan of University College Cork in Ireland, who has been trying to clarify how microbes influence the brain. “It’s all slightly weird and it’s all fascinating,” he says.

Cryan and others are amassing evidence that they hope will lead to “psychobiotics” — bacteria-based drugs made of live organisms that could improve mental health.

We’re not alone
Ted Dinan, the psychiatrist who coined the term “psycho­biotics,” was fascinated by a tragedy in Walkerton, Canada, in May 2000. Floods caused the small town’s water supply to be overrun with dangerous strains of two bacteria: Escherichia coli and Campylobacter. About half the town’s population got ill, and a handful of people died. For most residents, the illness was short-lived, about 10 days on average, says Dinan, who collaborates with Cryan at University College Cork. But years later, scientists who had been following the health of Walkerton residents noticed something surprising. “The rates of depression in Walkerton were clearly and significantly up,” Dinan says. That spike raised suspicion that the infection had caused the depression.

Other notorious bacteria have been tied to depression, such as those behind syphilis and the cattle-related brucellosis, and not just because ill people feel sad, Dinan says. He suspects there’s something specific about an off-kilter microbiome that can harm mental health.
This possibility, though it raises troubling questions about free will, is certainly true for lab animals. Mice born and raised without bacteria behave in all sorts of bizarre ways, exhibiting antisocial tendencies, memory troubles and recklessness, in some cases. Microbes in fruit flies can influence who mates with whom (SN: 1/11/14, p. 14), and bacteria in stinging wasps can interfere with reproduction in a way that prevents separate species from merging. Those findings, some by evolutionary biologist Seth Bordenstein of Vanderbilt University in Nashville, show that “there’s this potential for [microbes] to influence behavior in this complex and vast way,” he says.

By sheer numbers, human bodies are awash in bacteria. A recent study estimates there are just as many bacterial cells as human cells in our bodies (SN: 2/6/16, p. 6). Just how legions of bacteria get messages to the brain isn’t clear, though scientists have already found some likely communication channels. Chemically, gut microbes and the brain actually speak the same language. The microbiome churns out the mood-influencing neurotransmitters serotonin, norepinephrine and dopamine. Bacteria can also change how the central nervous system uses these chemicals. Cryan calls microbes in the gut “little factories for producing lots of different neuro­active substances.”

Signals between the gut and the brain may zip along the vagus nerve, a multilane highway that connects the two (SN: 11/28/15, p. 18). Although scientists don’t understand the details of how messages move along the vagus nerve, they do know that this highway is important. Snip the nerve in mice and the bacteria no longer have an effect on behavior, a 2011 study found. And when the gut-to-brain messages change, problems can arise.

New bacteria, new behavior
Wholesale microbe swaps can also influence behavior. In unpublished work, Dinan and his colleagues took stool samples from people with depression and put those bacteria (called “melancholic microbes” by Dinan in a 2013 review in Neurogastroenterology and Motility) into rats. The formerly carefree rodents soon began showing signs of depression and anxiety, forgoing a sweet water treat and showing more anxiety in a variety of tests. “Their behavior does quite dramatically change,” Dinan says. Rats that got a microbiome from a person without depression showed no changes in behavior.

Cryan and colleagues have found that the microbiomes of people with depression differ from those of people without depression, raising the possibility that a diseased microbiome could be to blame.
The fecal-transplant results suggest that depression — and perhaps other mental disorders — are contagious, in a sense. And a mental illness that could be caught from microbe swaps could pose problems. Fecal transplants have recently emerged as powerful ways to treat serious gut infections (SN Online: 10/16/14). Fecal donors ought to be screened for a history of mental illness along with other potentially communicable diseases, Dinan says.

“Gastroenterologists obviously check for HIV and hepatitis C. They don’t want to transmit an infection,” he says. The psychiatric characteristics of the donor should be taken into account as well, he says.

A fecal transplant is an extreme microbiome overhaul. But there are hints that introducing just one or several bacterial species can also change the way the brain works. One such example comes from Cryan, Dinan and colleagues. After taking a probiotic pill containing a bacterium called Bifidobacterium longum for a month, 22 healthy men reported feeling less stress than when they took a placebo. The men also had lower levels of the stress-related hormone cortisol while under duress, the researchers reported at the Society for Neuroscience meeting in Chicago last October. After taking the probiotic, the men also showed slight improvements on a test of visual memory, benefits that were reflected in the brain. EEG recordings revealed brain wave signatures that have been tied to memory skill, Cryan says.

The researchers had previously published similar effects in mice, but the new results move those findings into people. “What’s going to be important is to mechanistically find out why this specific bacteria is inducing these effects,” Cryan says. And whether there could be a benefit for people with heightened anxiety. “It’s a very exciting study, but it’s a small study,” Cryan cautions.

Bacteria in an even more palatable form — yogurt — affected brain activity in response to upsetting scenes in one study. After eating a carefully concocted yogurt every morning and evening for a month, 12 healthy women showed a blunted brain reaction to pictures of angry or scared faces compared with 11 women who had eaten a yogurtlike food without bacteria.

Brain response was gauged by functional MRI, which measures changes in blood flow as a proxy for neural activity. In particular, brain areas involved in processing emotions and sensations such as pain were calmed, says Tillisch, co­author of the study, published in 2013 in Gastroenterology. “In this small group, we saw that the brain responded differently” when shown the pictures, she says. It’s not clear whether a blunted response would be good or bad, particularly since the study participants were all healthy women who didn’t suffer from anxiety. Nonetheless, Tillisch says, the results raise the questions: “Can probiotics change your mood? Can they make you feel better if you feel bad?”

So far, the human studies have been very small. But coupled with the increasing number of animal studies, the results are hard to ignore, Tillisch says. “Most of us in this field think there is something definitely happening,” she says. “But it’s pretty complicated and probably quite subtle…. Otherwise, we’d all be aware of this.” Anyone who has taken a course of anti­biotics, or fallen ill from a bacterial infection, or even changed diets would have noticed an obvious change in mood, she says.

Two-way traffic
If it turns out that bacteria can influence our brains and behaviors, even if just in subtle ways, it doesn’t mean we are passive vessels at the mercy of our gut residents. Our behavior can influence the microbiome right back.

“We usually give up our power pretty quickly in this conversation,” Tillisch says. “We say, ‘Oh, we’re at the mercy of the bacteria that we got from our mothers when we were born and the antibiotics we got at the pediatrician’s office.’ ” But our microbes aren’t our destiny, she says. “We can mess with them too.”

One of the easiest ways to do so is through food: eating probiotics, such as yogurt or kefir, that contain bacteria and choosing a diet packed with “prebiotic” foods, such as fiber and garlic, onion and asparagus. Prebiotics nourish what are thought to be beneficial microbes, offering a simple way to cultivate the microbiome, and in turn, health.
That a good diet is a gateway to good health is not a new idea, Cryan says. Take the old adage: “Let food be thy medicine and let medicine be thy food.” He suspects that it’s our microbiome that makes this advice work.

Combating stress may be another way to change the microbiome, Tillisch and others suspect. Mouse studies have shown that stress, particularly early in life, can change microbial communities, and not in a good way.

She and her colleagues are testing a relaxation technique called mindfulness-based stress reduction to influence the microbiome. In people with gut pain and discomfort, the meditation-based practice reduced symptoms and changed their brains in clinically interesting ways, according to unpublished work. The researchers suspect that the microbiome was also altered by the meditation. They are testing that hypothesis now.

If the mind can affect the microbiome and the microbiome can affect the mind, it makes little sense to talk about who is in charge, Bordenstein says. In an essay in PLOS Biology last year, he and colleague Kevin Theis, of Wayne State University in Detroit, make the case that the definition of “I” should be expanded. An organism, Bordenstein and Theis argued, includes the microbes that live in and on it, a massive conglomerate of diverse parts called a holobiont. Giving a name to this complex and diverse consortium could shift scientists’ views of humans in a way that leads to deeper insights. “What we need to do,” Bordenstein says, “is add microbes to the ‘me, myself and I’ concept.”

A new X-ray telescope run by the Japan Aerospace Agency has gone silent a little more than a month after its launch. JAXA reported online March 27 that the telescope, ASTRO-H (aka Hitomi), stopped communicating with Earth. U.S. Strategic Command’s Joint Space Operations Center also reported seeing five pieces of debris alongside the satellite on March 26.

Attempts to figure out what went wrong with the spacecraft, which launched February 17, have not been successful. Up until now though, ASTRO-H seemed to be functioning. In late February, mission operators successfully switched on the spacecraft’s cooling system and tested some of its instruments.

ASTRO-H carries four instruments to study cosmic X-rays over an energy range from 0.3 to 600 kiloelectron volts. By studying X-rays, astronomers hope to learn more about some of the more feisty denizens of the universe such as exploding stars, gorging black holes, and dark matter swirling around within galaxy clusters. Earth’s atmosphere absorbs X-rays, so the only way to see them is to put a telescope in space.

Clownfish and anemones depend on one another. The stinging arms of the anemones provide clownfish with protection against predators. In return, the fish keep the anemone clean and provide nutrients, in the form of poop. Usually, several individual clownfish occupy a single anemone — a large and dominant female, an adult male and several subordinates — all from the same species. But with 28 species of clownfish and 10 species of anemone, there can be a lot of competition for who gets to occupy which anemone.

In the highly diverse waters of the Coral Triangle of Southeast Asia, however, clownfish have figured out how to share, researchers report March 30 in the Proceedings of the Royal Society B. Anemones in these waters are often home to multiple species of clownfish that live together peacefully.

From 2005 to 2014, Emma Camp, of the University of Technology Sydney and colleagues gathered data on clownfish and their anemone homes from 20 locations that had more than one species of clownfish residents. In 981 underwater survey transects, they encountered 1,508 clownfish, 377 of which lived in groups consisting of two or more fish species in a single anemone.

Most of those cohabiting clownfish could be found in the waters of the Coral Triangle, the team found, with the highest levels of species cohabitation occurring off Hoga Island in Indonesia. There, the researchers found 437 clownfish from six species living among 114 anemones of five species. Every anemone was occupied by clownfish, and half had two species of the fish.

In general, “when the number of clownfish species exceeded the number of host anemone species, cohabitation was almost always documented,” the researchers write.

The multiple-species groups divvied up space in an anemone similar to the way that a single-species group does, with subordinate fish sticking to the peripheries. That way, those subordinate fish can avoid fights — and potentially getting kicked off the anemone or even dying. “Living on the periphery of an anemone, despite the higher risk of predation, is a better option than having no host anemone,” the team writes.

These multi-species groups might even be better for both of the clownfish species, since they wouldn’t have to compete so much over mates, and perhaps even less over food, if the species had different diets.

This isn’t the first time that scientists have found cohabitation to be an effective strategy in an area of high biodiversity. This has also been demonstrated with scorpions in the Amazon. But it does show how important it is to conserve species in regions such as this, the researchers say — because losing one species can easily wipe out several more.

NEW YORK — Lip-readers’ minds seem to “hear” the words their eyes see being formed. And the better a person is at lipreading, the more neural activity there is in the brain’s auditory cortex, scientists reported April 4 at the annual meeting of the Cognitive Neuroscience Society.

Earlier studies have found that auditory brain areas are active during lipreading. But most of those studies focused on small bits of language — simple sentences or even single words, said study coauthor Satu Saalasti of Aalto University in Finland. In contrast, Saalasti and colleagues studied lipreading in more natural situations. Twenty-nine people read the silent lips of a person who spoke Finnish for eight minutes in a video. “We can all lip-read to some extent,” Saalasti said, and the participants, who had no lipreading experience, varied widely in their comprehension of the eight-minute story.

In the best lip-readers, activity in the auditory cortex was quite similar to that evoked when the story was read aloud, brain scans revealed. The results suggest that lipreading success depends on a person’s ability to “hear” the words formed by moving lips, Saalasti said.

It’s official: Zika virus causes microcephaly and other birth defects.

A new analysis by the U.S. Centers for Disease Control and Prevention confirms what many earlier studies had suggested: The virus, typically passed via the bite of an infected mosquito, can travel from a pregnant woman to her fetus and wreak havoc in the brain.

“There is no longer any doubt that Zika causes microcephaly,” CDC director Tom Frieden said in a news briefing Wednesday. The findings, reported April 13 in the New England Journal of Medicine, follow a March 31 report from the World Health Organization that concluded nearly the same thing.

Because the connection between a mosquito-borne illness and such birth defects is so unprecedented, the CDC took time to carefully weigh the evidence, Frieden said. “Never before in history has there been a situation where a bite from a mosquito could result in a devastating malformation.”

In the NEJM analysis, researchers factored in molecular, epidemiological and clinical data, including recent reports of babies born with microcephaly in Colombia. The country has been suffering from a Zika outbreak for months, and thousands of pregnant women have been infected with the virus. Based on what scientists know about the virus, now is about the time they would have expected to see birth defects, said CDC public health researcher and study coauthor Sonja Rasmussen. WHO reports 50 cases of microcephaly in Colombia, seven of which have a confirmed link to Zika.

Researchers still can’t pin down the odds that an infection during pregnancy will lead to microcephaly, though. “What we don’t know right now is if the risk is somewhere in the range of 1 percent or in the range of 30 percent,” Rasmussen said.

Scientists do believe, however, that women who aren’t pregnant would probably clear a Zika infection within eight weeks, and not have problems with future pregnancies, Rasmussen said.

Bacterium effective when dusted on plants — The successful agent for destroying pesty insects, the microscopic bacterium, Bacillus thuringiensis, is most effective when it is dusted onto tobacco or other plants…. The bacteria are now recommended for use against tobacco budworms and hornworms. From known results …. they look promising as biological control agents. — Science News, April 30, 1966

Update
Bacillus thuringiensis, or Bt, is still used to combat agricultural pests. Different strains of the bacterium target different insects; one strain can even kill mosquito larvae in water. Organic farmers dust or spray Bt on crops and consider it a natural insecticide. In conventional farming, Bt DNA is often inserted into a plant’s genome, creating genetically modified crops that make their own pesticide (SN: 2/6/16, p. 22). In 2015, 81 percent of U.S. corn and 84 percent of U.S. upland cotton contained Bt genes.

To rewrite an Alanis Morissette song, the brain has a funny way of waking you up (and putting you to sleep). Isn’t it ionic? Some scientists think so.

Changes in ion concentrations, not nerve cell activity, switch the brain from asleep to awake and back again, researchers report in the April 29 Science. Scientists knew that levels of potassium, calcium and magnesium ions bathing brain cells changed during sleep and wakefulness. But they thought neurons — electrically active cells responsible for most of the brain’s processing power — drove those changes.
Instead, the study suggests, neurons aren’t the only sandmen or roosters in the brain. “Neuromodulator” brain chemicals, which pace neuron activity, can bypass neurons altogether to directly wake the brain or lull it to sleep by changing ion concentrations.

Scientists hadn’t found this direct connection between ions and sleep and wake before because they were mostly focused on what neurons were doing, says neuroscientist Maiken Nedergaard, who led the study. She got interested in sleep after her lab at the University of Rochester in New York found a drainage system that washes the brain during sleep (SN: 11/16/13, p. 7).When measuring changes in the fluid between brain cells, Nedergaard and colleagues realized that ion changes followed predictable patterns: Potassium ion levels are high when mice (and presumably people) are awake, and drop during sleep. Calcium and magnesium ions follow the opposite pattern; they are higher during sleep and lower when mice are awake.
In the study, Nedergaard’s group administered a “wake cocktail” of neuromodulator chemicals to mouse brains. Levels of potassium ions floating between brain cells increased rapidly after the treatment, the researchers found. That ion change happened even when the researchers added tetrodotoxin to stop neuron activity. The results suggest that the brain chemicals — norepinephrine, acetylcholine, dopamine, orexin and histamine — directly affect ion levels with no help from neurons. Exactly how the chemicals manage ion levels still isn’t known.
Similar changes happen under anesthesia. When awake mice were anesthetized, potassium ion levels in their brains dropped sharply, while levels of calcium and magnesium rose, the researchers found. As mice awoke from anesthesia, potassium ion levels rose quickly. But calcium and magnesium levels took longer to drop. As a result, the mice “are totally confused,” says Nedergaard. “They bump into their cages, they run around and they don’t know what they are doing.”

Those results may help explain why people are groggy after waking up from anesthesia; their ion levels haven’t returned to “awake” levels yet, says Amita Sehgal, a sleep researcher at the University of Pennsylvania School of Medicine.

Learning more about how ions affect wake and sleep may eventually lead to a better understanding of sleep, consciousness and coma, Nedergaard says.

But, says neuroscientist Chiara Cirelli of the University of Wisconsin‒Madison, practical implications of the work, such as improved sleep drugs, are probably far in the future. “How they make use of it will take some time, but just knowing this is certainly very eye-opening.” It would be interesting to find out what happens to ion concentrations during REM sleep, when neurons are as active as they are when a person is awake, she says.

techstyle

Through July 10
Museum of Fine Arts, Boston

You wouldn’t expect wardrobe classics like leather jackets or denim jeans at an exhibit celebrating fashion at its most forward. But “#techstyle” at the Museum of Fine Arts in Boston features those sartorial mainstays and others, each with a technological twist.

A feast for the eyes, the diversity of pieces is matched by the diversity of artists and approaches. Yet a single theme unites: The fusion of technology and fashion will increasingly influence both. Visitors are introduced to this theme via a room featuring works by prominent designers already known for merging fashion and tech: A digitally printed silk dress by Alexander McQueen hangs next to a fiberglass “airplane dress” by Hussein Chalayan that has flaps that open and shut via remote control.
The largest part of the exhibit focuses on how technology is changing design and construction strategies. In addition to clothes made with mainstream techniques like laser-cutting, several 3-D printed garments are on display. These include a kinematic dress made of more than 1,600 interlocking pieces that can be customized to a wearer’s body via a 3-D scan. The dress comes off the printer fully assembled. Other pieces are made with technologies still being developed, such as the laser-welded fabrics from sustainable textile researcher Kate Goldsworthy.
The real standouts are in the “Performance” section, which displays attire that uses data from the immediate environment to generate some visible aspect of the garment. These interactive pieces “reveal something to the eye that you wouldn’t see normally, something that science often captures with graphs and charts,” says Pamela Parmal, a curator of the exhibit. For instance, the interactive dress “Incertitudes” is adorned with pins that flex in response to nearby voices, creating waves in the fabric; a dress embedded with thousands of tiny LEDs can display tweeted messages or other illuminated patterns.
And there are two leather jackets that, at first glance, look like their innovation is merely a stylish cut. But the jackets are coated in reactive inks that shimmer with iridescent colors in response to the wind and heat generated by heat guns in the display case. (These creations were born after designer and trained chemist Lauren Bowker used the reactive compounds to reveal the aerodynamics of race cars in a wind tunnel in a project for Formula One.)

Visitors seeking in-depth explanations of the science behind the fashions will have to look elsewhere. But “#techstyle” still has something for everyone, whether fashionista or engineer. And while the fashions represented are all cutting edge, the show harks back to an era when clothes were custom-made. Technology might have brought us mass-produced cookie-cutter clothing, but it can also enable clothing tailored to the individual.

Lead contamination in drinking water can change with the seasons. Tracking lead levels in water pipes over several months, researchers discovered three times as much dissolved lead and six times as much undissolved lead in summer than in winter. The finding could help improve water testing, says study coauthor Sheldon Masters, an environmental engineer at Virginia Tech and Corona Environmental Consulting in Philadelphia.

Masters and colleagues analyzed water contamination data collected from pipes in Washington, D.C., and Providence, R.I., and tested the dissolvability of lead in different water conditions. In many, but not all, homes and lab tests, the amount of lead leaching into drinking water rose as water temperature increased.

For pipes in Washington, average wintertime dissolved lead levels were 3.6 parts per billion, compared with 10.8 ppb during summer. Average undissolved lead concentrations varied from 7.6 ppb during winter to 48.4 ppb during summer. Each 1 degree Celsius rise in water temperature boosted dissolved lead levels by about 17 percent and lead particles by about 36 percent, the researchers report online April 14 in Environmental Science & Technology. Washington water temperature varied from about 5° to 30° C. Seasonal variations in lead were smaller than those expected from temperature changes alone, since other factors such as the amount of organic matter in water can also influence lead levels.

Some water systems could meet the regulatory standard of less than 15 ppb in winter while exceeding that threshold during warmer months, the researchers warn. Water testing prioritizes conditions with the highest risk for lead leaching. However, no current guidelines explicitly address seasonal variability. Lead consumption can cause severe health problems including birth defects, anemia and brain damage (SN: 3/19/16, p. 8).