Common House Dust Could Contain Cancer-Causing Molecules

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 Most of us never give a second thought to the dust in our homes, except to sweep it up and throw it away. But for scientists, that dust is a goldmine of information about the chemicals we encounter every day. Unlike soil, water, or air, most of the chemicals in dust come directly from us or our stuff, and we spend so much time indoors that if scientists find something in dust, there’s a good chance it’s also in us. So when a team of Canadian scientists found some potentially cancer-causing chemicals in house dust, they knew they had to investigate further.
 

 Hui Peng and the team didn’t set out to find these chemicals. Rather, the chemist at the University of Saskatchewan was hoping to solve a puzzle. One of the more concerning chemicals in dust are flame retardants that contain the element bromine, some of which can disrupt hormone activity or impair fetal development. But there’s far more bromine in house dust than the flame retardants can account for.
 

 ­­To solve that puzzle, Peng suspected he could use a new tool that he and others in the lab of Dr. John Giesy. The tool, called DIPIC-Frag, sifts through complex mixtures like dust and finds unknown chemicals. It’s an advanced sort of mass spectroscopy, a method of identifying chemicals by breaking them apart and then using an electromagnet to sort the electrically-charged fragments by mass.
 

 Typically, finding the signal of a single chemical in the noise of a sample like dust is only possible by comparing the sample to a standard. But DIPIC-Frag uses a statistical analysis of the signals to find the chemical formulas of hundreds of molecules at once.
 

 Bromine-containing molecules are particularly easy to identify with mass spectroscopy, because bromine atoms come in two different masses, or isotopes, of approximately equal frequency. The mass spectrometer can zero in on this pair of signals, eliminating the noise from other chemicals in the sample.
 

 The method builds on years of advancement in what such analysis is capable of. “The science is good enough to do this,” said Dean Jones, a professor of medicine at Emory University who was not involved in the study. “They’re pushing the limits on what the technique is.”
 

 When the team used DIPIC-Frag to look for bromine-containing molecules in dust samples collected from seven homes in Saskatoon, Saskatchewan, about 17% of the molecules they identified were the expected flame retardants. But 56% of the bromine-containing molecules had chemical formulas that marked them as related to azo dyes, commonly used to color clothing and other textiles.
 

 It was a startling discovery. “Most of these compounds have never been reported before,” Peng said.
 
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/dust_2048x1152.width-990_5Sh6ays.jpg"/>
<figcaption>Scientists found that dust particles could contain potentially cancer-causing chemicals.
 
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 Most azo dyes are harmless by themselves, but when exposed to UV light or digested by bacteria on our skin, some can be degraded into smaller molecules that can enter our cells and damage DNA. What’s more, some compounds used in the manufacture of these dyes can still cling to clothes. Azo dyes that are known to degrade into harmful chemicals are banned in the European Union and seldom used elsewhere. The scientists were concerned that they had found so many previously undiscovered molecules similar to these toxic precursors and degradation products. The team decided to test how one of these molecules, a precursor called BNA, affected the DNA of the bacteria
 
 Salmonella
 
 .
 

 Even at the low concentrations found in house dust, BNA caused mutations in the
 
 Salmonella
 
 DNA. The results might solve another mystery of dust: “most of the toxicity cannot be explained by compounds we’ve seen before,” Peng said.
 

 But knowing whether BNA is in fact a cancer risk will take much more testing, said Jianxian Sun, a co-author on the study who performed the toxicity testing. Other compounds will be even harder to test, since many of them aren’t readily available for the scientists to buy and test.
 

 In the meantime, there’s no reason to panic, Jones said. “We’re probably exposed to a million chemicals in our lifetime,” he said. Most of these might not be harmful enough to be worth regulating, but could be risk to individual people in certain cases—if they’re particularly sensitive, or if they’re exposed to higher amounts for a long time.
 

 But the fact that Peng and his collaborators identified so many new chemicals is also good news for the fight against toxic chemicals he said, if it means that other potential threats can be discovered and examined more rapidly and cheaply. “We want to push this strategy in the future,” Peng said, using DIPIC-Frag to find chemicals that are already in the environment and decide if they should be regulated, rather than attempting to track all manner of industrial chemicals from their source.
 

 Such regulation would be important for chemicals that show up in something as ubiquitous as house dust, said An Li, a professor of Environmental and Occupational Health Sciences at the University of Illinois at Chicago. “If you find high levels in house dust, it’s very likely humans are exposed through skin contact or food,” she said.
 

 Li studies pollution in the Great Lakes, where DIPIC-Frag has also been useful. “Their machine is capable of something we cannot do here,” she said. Last year, Li and the Saskatchewan team found more than a thousand new bromine-containing chemicals in samples from Lake Michigan, some of which were also potentially toxic.
 

 But most of the chemicals found in the Lake Michigan study were “natural products,” Peng said—not human-made, and therefore hard to decrease with human efforts. Dust, on the other hand, is almost entirely manmade chemicals.
 

 Even so, Peng acknowledges that regulations of chemicals such as those in the house dust will be slow to change. “This is a very promising strategy, but it may take a long time” to assemble enough scientific evidence to know how to act.
 

 The more immediate effect of methods like DIPIC-Frag may not be in regulation, but in medicine, said Jones, the Emory professor. In the future, he said, “we’ll still be regulating chemical by chemical,” rather than using techniques like DIPIC-Frag. But if techniques for analyzing thousands of chemicals at once become cheap, he said, “one could in fact have devices in a person’s home to evaluate what they’re exposed to.”
 

 Jones thinks that cheap methods for evaluating what people are exposed to could do for the human “exposome” what genetic sequencing promises to do for the human genome—give us personalized medical advice based on massive amounts of data.
 

 The next step is to check if chemicals like BNA show up in dust in places other than Saskatoon. George Cobb, a professor of environmental science at Baylor University, is collaborating with scientists at Murray State University in Kentucky to collect samples from sites around Texas and Kentucky. If those samples contain similar brominated dyes to the Canadian ones, it’s a good indication that this is a concern that crosses borders and regions.
 

 “The method is very easy to adopt,” Cobb said. If he finds the same bromine-containing chemicals as the Canadian team, it will start the long process of testing the various chemicals for toxicity—in bacteria, in computer models, and finally in animals. Then another long review before any regulations are changed.
 

 But to Cobb, that’s all in the future.
 

 “What we really want to know first is what’s in there,” he said.
 
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In superagers, the brain networks used for memory, learning, and resilience are nearly untouched by age.

'Superaging': How Some 80-Year-Olds’ Memories Are as Sharp as 20-Year-Olds’

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 It’s as inevitable as grey hair and wrinkles—when we get old, our memories decline, even if Alzheimer’s or dementia doesn’t accelerate that process. But there are a select few whose memories seem to remain as hale as those decades younger. Scientists call them superagers. And now, there is some clarity as to how these superagers hold on to their robust memory.


 In superagers, the brain networks used for memory, learning, and resilience are nearly untouched by age. While other areas of their brains atrophied, the memory networks of superagers aged 60 to 80 were as healthy as those of the average 18-to-32-year-old’s brain, researchers at Massachusetts General Hospital
 <a href="http://jneurosci.org/content/36/37/9659.full?sid=dcaa88e5-304e-46b3-b140-f0ad3433d057">
 reported
 </a>
 recently in the Journal of Neuroscience. “We were surprised by that,” said Alex Touroutoglou, a researcher in neurology at Massachusetts General Hospital and a co-author of the study.


 While some earlier evidence of “superaging” had been found in the brains of patients older than 80, the new results show how the trait can appear in brains up to two decades younger.


 By watching how superagers avoid some of the consequences of normal aging, the researchers hope to understand and alleviate both the slow decline of healthy aging and the diseases that accelerate it.


 To measure brain health, Touroutoglou and her collaborators examined the cortex, the layer on the surface of our brains rich in grey matter. Only a few millimeters thick, the cortex coats the brain’s distinctive folds and is involved in many of the advanced thought patterns that are hallmarks of our humanity—like language, memory, and consciousness. But as we age, that cortex grows thinner, reducing the brain’s cognitive resources. By measuring the thickness of this cortex, then, scientists can see how much aging has degraded that part of the brain.

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 When the team looked at the cortex of superagers, they found that in many areas, it had thinned out as expected. But in areas used to recall memories and to make new ones, it remained about as thick as those in the 18-to-32-year-old brains.


 The researchers also found thick, healthy cortex in regions where it would bolster what Touroutoglou called “tenacity and the will to persevere in the face of challenges.” If this correlation is replicated in other studies, it could mean that the memory networks alone aren’t responsible for superaging. One interpretation is that elderly people who stay engaged with work, life, and family end up keeping these memory networks active, keeping them healthy later on.


 The study reinforces similar results previously seen in the brains of superagers older than 80, said Emily Rogalski, a research associate professor of cognitive neurology at Northwestern University’s School of Medicine who also studies the brains of superagers. She said she hoped more research on superaging could give a more optimistic view of aging: “There’s a need for looking at more than what’s going wrong with the brain.”


 Joseph Adreano, a psychiatry researcher at MGH and co-author on the study, said the next step is to understand how superager brains stay healthy. Even when brains age normally, without any visible sign of disease, they accumulate molecules called amyloids—the suspected culprits behind Alzheimer’s and some dementias. Adreano is studying superagers to see if their brains contain fewer of these molecules, especially in the areas that have remained unusually healthy. “There’s a possibility that these superaging people might be more resilient to disease,” he said.


 Despite their hopes to better understand Alzheimer’s and dementia, the team is unsure how quickly, if at all, superaging research will help treat or prevent those diseases. The study used only healthy volunteers, so more research comparing the brains of superagers to those of diseased patients is needed to make progress on those diseases.


 “We are at the very early stages, but it’s exciting,” Touroutoglou said.

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In &quot;superagers,&quot; the brain networks used for memory, learning, and resilience are nearly untouched by age.

Emergency Response, Courtesy of Twitter

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 The response is drilled into us from childhood. Whatever the emergency—fire, earthquake, or riot—we reach for our phones and… send out a tweet? It may sound like a luddite’s social-media dystopia, but if researchers at the Indian Institute of Technology-Bombay (IIT-B) get their way, Twitter might be as important to emergency response as 911 calls.
 

 The researchers have developed a tool to turn tweets into emergency alerts, in real time. Called Civique (pronounced “civic”), it searches for tweets about emergencies, then sends information about those emergencies to responders and bystanders. Though its creators don’t anticipate fully replacing telephone reporting systems like 911, they expect it to supplement such calls with instantaneous, geo-located updates. The tool is described in a conference
 <a href="https://arxiv.org/pdf/1610.04377.pdf">
 paper
 </a>
 posted on arXiv.
 

 “The problem with 911 is you’re asking questions,” which can take up valuable time, said Krithi Ramamritham, an IIT-B professor of Computer Science who led the team. With Civique, he said, “the emergency is detected automatically,” collecting information more quickly and from more people than any human emergency response could manage.
 
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<figcaption>A new tool called Civique searches for tweets about emergencies, then sends information about those emergencies to responders and bystanders.
 
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 But Civique faces an uphill fight for widespread adoption. “People will not change their habits in emergencies,” said Tomer Simon, an emergency management expert for Israeli Home Front Command who researches how first responders should use social media. Simon points to a previous emergency crowdsourcing system, called Tweak, which he says failed because it asked people to use an invented grammar and vocabulary to tweet about language.
 

 To track where emergencies are occurring, Civique would also require that users change their mindset to allow Twitter, and the world, to view their location. “99% of tweets are not geo-located,” said Simon, “so you really cannot know where the tweet is originating from.”
 

 But this problem should be surmountable, said Dave Yates, an assistant professor of business information and analytics at the University of Denver who was not involved with the project. “With some training, you could develop the mindset that you should enable geo-locating,” he said.
 

 When Civique reads a tweet, it uses a machine learning algorithm called a classifier to decide if the tweet describes an emergency, and if so, what sort of emergency. Ramamritham and his team trained the system on tweets they designed to be misleading to prevent the system from sending firemen after someone frustrated about being fired.
 

 But before Civique can decide what the words mean, it has to decide what the words actually are. “People tend to tweet using a sort of SMS language,” said Diptesh Kanojia, a PhD student at IIT-B who worked on developing the tool. So before the tweet is fed to the classifier, words like “fiiiiiirrrreeee” or “hlp” passes through several layers of compression, normalization, and spell-checking.
 

 “They did a pretty good job of trying to stress their system,” Yates said. But he noted that no matter how good the training, the number of tweets—and thus the number of mistakes—would be vastly greater in a real-world context, leading to false or missed alerts. “You would still have to overcome that or be aware of that,” he said.
 

 Yates also worries that people could use the tool maliciously; Imagine a criminal who wanted to draw police away from one part of town, so tweeted about an active shooter elsewhere. “Things like that aren’t really a problem with the tool itself, but in how the tool would be implemented,” he said, noting that a false 911 call could achieve the same end.
 

 Accuracy isn’t just important for its own sake, but for ensuring first responders believe the information they are getting. “They get used to their information coming in from certain sources they can verify,” Yates said. “This throws that model on its head.” First responders make life-and-death decisions quickly, and they cannot make the right decision if they have too little—or too much—confidence in the tool.
 

 Field tests may help build confidence—the team has already developed a modified version of Civique for the IIT-B campus to alert the school to maintenance problems, and they are pushing the city of Mumbai to deploy it to track local emergencies.
 

 The next step, Ramamritham said, is to correlate the tweets to provide first responders with richer information—to, say, combine one tweet geo-located in a building with another indicating that the building had collapsed, which would tell emergency crews that there were people in the collapsed building. “You can do that almost right now. We have that information,” he said.
 
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Ancient Cultural Exchanges May Have Driven Modern Human Behaviors

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 Before we ever wrote on paper or even stone tablets, humanity was unwittingly writing its history in the DNA of each successive generation. Now, after tens of thousands of years, scientists reading the history written in—and omitted from—those genes are re-writing the story of how human culture began.
 

 By combing through 100,000 years of genetic history, scientists say they have shown that modern human behaviors which arose about 50,000 years ago traveled from person to person through cultural, not genetic exchange. The genetic data also add new layers to the history of human migration out of Africa and provide a valuable medical resource. The findings were
 <a href="http://www.nature.com/nature/journal/v538/n7624/full/nature18964.html">
 published
 </a>
 last month in the journal
 
 Nature
 
 .
 
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<figcaption>Human innovations like art are thought to have arisen from cultural exchanges, according to a new study.
 
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 Ancient humans became a lot more like modern humanity around 50,000 years ago, developing innovations like art, fishing, and blades within a relatively short span of time, said Stanford University anthropologist Richard Klein, who noted this change in his 2002 book
 
 The Dawn of Human Culture
 
 . “[There] was a radical change in human innovative ability about 50,000 years ago,” Klein said, “and I speculated that genetic change was responsible.”
 

 Without genetic evidence, though, others argued the change was not a sudden genetic leap but gradual cultural change. The “human revolution” was instead “a gradual assembling of the package of modern human behaviors in Africa,” argued anthropologists Sally McBrearty and Alison Brooks in a
 <a href="https://cashp.columbian.gwu.edu/sites/cashp.columbian.gwu.edu/files/downloads/ASBrooks_The%20Revolution%20that%20wasn't.pdf">
 2000 paper.
 </a>


 The DNA evidence was collected by sequencing the genomes of more than 300 people from around the world. To ensure that a full history of humanity was represented, scientists made a special effort to collect DNA from a diverse grouping of humans. Thus the project became known as the Simons Genome Diversity project.
 

 With each generation, our DNA accumulates small, mostly harmless mutations, which scientists can use as a sort of marker to trace which populations the DNA has passed through.
 

 “Our genome is not just ours,” said Shop Mallick, a computational biologist at Harvard Medical School, and a co-author on the paper. “Your genome contains signals from all of your ancestors.”
 

 By measuring how different the DNA of people from disparate populations are, the scientists could answer one critical question: “How far back in time do you have to go before the populations that two samples came from are linked?” Mallick said. For many populations in the study, enough mutations had occurred since their last genetic exchange that their last common ancestor must have been at least 100,000 years ago.
 

 This paints a picture of humanity 50,000 years ago as a species consisting of sparsely separated geographical groups with little genetic exchange between them. If the groups were genetically separate before the “human revolution” and before the migration out of Africa, it is extremely unlikely that all of humanity underwent the same genetic change at the same time.
 

 The “human revolution,” the study says, was a cultural one.
 

 Examining this history didn’t just lead to a picture of humanity 50,000 years ago during the “human revolution.” It also confirmed how humans left Africa—finding that everyone from Europeans to Australian Aboriginals shared DNA from a single migration. Though there may have been earlier migrations which left small traces on non-African humans’ DNA, “we can be quite sure that less than 2% of genomic DNA that may have come from an earlier expansion,” Mallick said.
 

 Because of the diversity of the sampled populations, the data from the study could prove valuable for more modern medical purposes as well. The researchers found 5.8 million new mutations in human DNA that had never before been encountered; the list of these mutations is a valuable resource for scientists researching the genetics ailments from cancer to developmental diseases. To aid these studies, the authors have posted the data online for other scientists to use.
 

 The resulting depository, Mallick said, “creates a snapshot of humanity as it is today.” In this DNA is a sort of family photo of the seven billion of us—one that both hints at our past and could aid in a healthier future.
 
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Bennett McIntosh

Articles

Common House Dust Could Contain Cancer-Causing Molecules

'Superaging': How Some 80-Year-Olds’ Memories Are as Sharp as 20-Year-Olds’

Emergency Response, Courtesy of Twitter

Ancient Cultural Exchanges May Have Driven Modern Human Behaviors

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