It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Scanning electron microscope image of black tea leaves, magnified by 300 times. Black tea, which is wilted and fully oxidized, exhibits a wrinkled and surface, potentially increasing the available surface area for adsorption.
Credit: Vinayak P. David Group/Northwestern University
Good news for tea lovers: That daily brew might be purifying the water, too.
In a new study, Northwestern University researchers demonstrated that brewing tea naturally adsorbs heavy metals like lead and cadmium, effectively filtering dangerous contaminants out of drinks. Heavy metal ions stick to, or adsorb to, the surface of the tea leaves, where they stay trapped until the used tea bag is disposed.
The study will be published on Tuesday (Feb. 25) in the journal ACS Food Science & Technology.
“We’re not suggesting that everyone starts using tea leaves as a water filter,” said Northwestern’s Vinayak Dravid, the study’s senior author. “For this study, our goal was to measure tea’s ability to adsorb heavy metals. By quantifying this effect, our work highlights the unrecognized potential for tea consumption to passively contribute to reduced heavy metal exposure in populations worldwide.”
“I’m not sure that there’s anything uniquely remarkable about tea leaves as a material,” said Benjamin Shindel, the study’s first author. “They have a high active surface area, which is a useful property for an adsorbent material and what makes tea leaves good at releasing flavor chemicals rapidly into your water. But what isspecial is that tea happens to be the most consumed beverage in the world. You could crush up all kinds of materials to get a similar metal-remediating effect, but that wouldn’t necessarily be practical. With tea, people don’t need to do anything extra. Just put the leaves in your water and steep them, and they naturally remove metals.”
An expert on sorbent materials and sponge entrepreneur, Dravid is Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering. At the time of the research, Shindel was a Ph.D. student in Dravid’s laboratory; now he works with the U.S. Department of Energy’s National Energy Technology Laboratory.
Exploring different variables
To conduct the study, the Northwestern team explored how different types of tea, tea bags and brewing methods affect heavy metal adsorption. The various varieties tested included “true” teas such as black, green, oolong and white, as well as chamomile and rooibos teas. They also examined the differences between loose-leaf and commercially bagged tea.
The researchers created water solutions with known amounts of lead and other metals (chromium, copper, zinc and cadmium), and then heated the solutions to just below boiling temperature. Next, they added the tea leaves, which steeped for various time intervals — from mere seconds to 24 hours.
After steeping, the team measured how much of the metal content remained in the water. By comparing metal levels before and after adding the tea leaves, they were able to calculate how much was effectively removed.
Cellulose bags work best — and don’t release microplastics
After multiple experiments, Dravid, Shindel and their team identified several trends. Perhaps somewhat unsurprising: The bag matters. After testing different types of bags without tea inside, the researchers found cotton and nylon bags only adsorbed trivial amounts of the contaminants. The cellulose bags, however, worked incredibly well.
The key to a successful sorbent material is high surface area. Similar to how a magnet attaches to a refrigerator door, metal ions cling to the surface of a material. So, the more area for the particles to stick to, the better. Shindel posits that cellulose, which is a biodegradable natural material made from wood pulp, has higher surface area — and therefore more binding sites — than sleeker synthetic materials.
“The cotton and nylon bags remove practically no heavy metals from water,” Shindel said. “Nylon tea bags are already problematic because they release microplastics, but the majority of tea bags used today are made from natural materials, such as cellulose. These may release micro-particles of cellulose, but that’s just fiber which our body can handle.”
Longer steeping time, fewer metals
When comparing different varieties of tea, the researchers discovered tea type and grind played minor roles in adsorbing contaminants. Finely ground tea leaves, particularly black tea leaves, adsorbed slightly more metal ions than whole leaves. Again, the researchers attributed this to surface area.
“When tea leaves are processed into black tea, they wrinkle and their pores open,” Shindel explained. “Those wrinkles and pores add more surface area. Grinding up the leaves also increases surface area, providing even more capacity for binding.”
Out of all the experiments, one factor stood out most. Steeping time played the most significant role in tea leaves’ ability to adsorb metal ions. The longer the steeping time, the more contaminants were adsorbed.
“Any tea that steeps for longer or has higher surface area will effectively remediate more heavy metals,” Shindel said. “Some people brew their tea for a matter of seconds, and they are not going to get a lot of remediation. But brewing tea for longer periods or even overnight –- like iced tea –- will recover most of the metal or maybe even close to all of the metal in the water.”
Future opportunities
Although results depend on several factors — steeping time and water-to-tea ratio, for example — tea preparation removes an amount of lead from water that should be significant from a public health perspective.
From their experiments, the researchers estimate that tea preparation can remediate about 15% of lead from drinking water, even up to lead concentrations as high as 10 parts per million. That estimate applies only to a “typical” cup of tea, which includes one mug of water and one bag of tea, brewed for three to five minutes. Changing the parameters remediates different levels of lead. Steeping for longer than five minutes, for example, adsorbs more lead compared to the average steeping time.
“Ten parts lead per million is obviously incredibly toxic,” Shindel said. “But with lower concentrations of lead, tea leaves should remove a similar fraction of the metal content in the water. The primary limiting factor is how long you brew your tea for.”
In high-resource areas of the world, it’s unlikely that concentrations will reach such high levels. And if there is a water crisis, brewing tea will not solve the problem. But Shindel said the study’s results provide useful new information that could be applied to public health research.
“Across a population, if people drink an extra cup of tea per day, maybe over time we’d see declines in illnesses that are closely correlated with exposure to heavy metals,” he said. “Or it could help explain why populations that drink more tea may have lower incidence rates of heart disease and stroke than populations that have lower tea consumption.”
New study finds that brewing tea naturally removes lead and other toxic heavy metals from water.
In the study, researchers tested various varieties of teas, including “true” teas such as black, green, oolong and white, as well as chamomile and rooibos teas. They also examined the differences between loose-leaf and commercially bagged tea.
In the study, researchers examined the differences in loose-leaf and bagged teas. They found cotton and nylon bags only adsorbed trivial amounts of the contaminants. The cellulose (or paper) bags, however, worked incredibly well.
Credit
Vinayak P. David Group/Northwestern University
Journal
ACS Food Science & Technology
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Brewing clean water: The metal-remediating benefits of tea preparation
Article Publication Date
25-Feb-2025
How plants epigenetically regulate their chemical defences
A new study demonstrates how plants of the nightshade family produce pharmaceutically valuable compounds and how this biosynthesis is epigenetically regulated.
Plants are masters at producing a huge variety of chemical substances to protect themselves against animals and pathogens. Among the hundreds of thousands of botanical compounds, many are interesting for human health due to their medicinal characteristics. Many plants of the nightshade family, for example, form so-called withanolides, a diverse group of steroids with health-beneficial properties. However, there has been little research into the biosynthesis and regulation of these compounds.
A research team led by Professor Claude Becker, geneticist in the Faculty of Biology at LMU, has now discovered a gene cluster that is responsible for the production of withanolides in the ground-cherry (Physalis grisea). Recently published in the journal PNAS, the study was a collaboration with partners from the Max Planck Institute of Molecular Plant Physiology in Golm and the University of Hohenheim. “In such gene clusters, genes encoding for enzymes that coordinate the subsequent steps in a biosynthetic pathway are organized in close proximity to each other,” explains Becker. “This ensures that they are regulated and inherited together.”
In the case of the withanolide cluster, the team found a duplication in the genome, whereby the two resulting units are organized in two functionally separate domains. While one is active only in the plant root, the other is active in above-ground tissues. “What surprised us is that the separation and organization of the two units appears to be regulated epigenetically,” says Becker. Thus, the two cluster versions differ in the local structure and chemical modifications of the DNA. The researchers believe this separation allows the plant to produce slightly different chemical defenses in its above- and below-ground tissues.
Through comparative genomics, the team could also show that, while the duplication of the withanolide gene cluster is specific to the sub-family of Physalis and its close relatives, the cluster itself is highly conserved across the nightshade family but absent in the genus containing tomato and potato. “Our study provides first insights into the production of the diverse and multi-functional metabolite group of the withanolides, an essential first step for the potential development of derived alternative pesticides and novel therapeutics,” concludes Becker.
The Huns suddenly appeared in Europe in the 370s, establishing one of the most influential although short-lived empires in Europe. Scholars have long debated whether the Huns were descended from the Xiongnu. In fact, the Xiongnu Empire dissolved around 100 CE, leaving a 300-year gap before the Huns appeared in Europe. Can DNA lineages that bridge these three centuries be found?
To address this question, researchers analyzed the DNA of 370 individuals that lived in historical periods spanning around 800 years, from 2nd century BCE to 6th century CE, encompassing sites in the Mongolian steppe, Central Asia, and the Carpathian Basin of Central Europe. In particular, they examined 35 newly sequenced genomes ranging from: a 3rd-4th century site in Kazakhstan and 5th-6th century contexts in the Carpathian Basin, including exceptional Hun-period burials that exhibit Eastern or “steppe” traits often linked to nomadic traditions (i.e. “eastern-type” burials).
The study was carried out as part of the ERC Synergy Grant project HistoGenes (No. 856453), by a multidisciplinary research team of geneticists, archaeologists and historians, including researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The results showed that there was not a large Asian- or steppe-descended community living in the Carpathian Basin after the Huns' arrival. However, they identified a small but distinct set of individuals - often belonging to the “eastern-type” burials - who did carry significant East Asian genetic signatures. Advanced comparisons of genealogical connections (the analysis of shared DNA segments known as identical-by-descent, or IBD) led to a remarkable discovery. Co-first author Guido Alberto Gnecchi-Ruscone of the Max Planck Institute for Evolutionary Anthropology adds: “It came as a surprise to discover that few of these Hun-period individuals in Europe share IBD links with some of the highest-ranking imperial elite individuals from the late Xiongnu Empire”. These connections also include an individual from the largest terrace tomb ever discovered in a Xiongnu context.
Connections across the steppe and mixed legacy
This link suggests that some among the Huns in Europe could trace their lineage back to important late Xiongnu burials from the Mongolian steppe. Yet the archaeogenomic picture for most Hun and post-Hun period individuals in the Carpathian Basin is far more varied. Co-first author Zsófia Rácz of the Eötvös Loránd University in Budapest adds: “DNA and archaeological evidence reveal a patchwork of ancestries, pointing to a complex process of mobility and interaction rather than a mass migration.” While these connections confirm the presence of some direct descendants of Xiongnu elites, the study also shows that the population of the Hun empire in Europe was genetically highly heterogeneous. Another key conclusion of the study is that the 5th century “eastern-type” burials from Central Europe are highly diverse in both their cultural and genetic heritage.
The findings also underscore that the Huns’ arrival in Europe contrasts with that of the Avars two centuries later. Co-corresponding author Walter Pohl of the Austrian Academy of Sciences adds: “The Avars came directly to Europe after their East-Asian empire had been destroyed by the Turks, and many of their descendants still carried considerable East Asian ancestry until the end of their rule in c. 800. The ancestors of Attila’s Huns took many generations on their way westward and mixed with populations across Eurasia”.
Implications for European history
This research illuminates how past societies in the Carpathian Basin adapted and changed in response to new arrivals. Co-corresponding author Zuzana Hofmanová of the Max Planck Institute for Evolutionary Anthropology adds: “Although the Huns dramatically reshaped the political landscape, their actual genetic footprint - outside of certain elite burials - remains limited”. Instead, the population as a whole appears to be predominantly of European origin and have continued local traditions, with some newly arrived steppe influences woven in.
Co-corresponding author Johannes Krause, director of the Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthroplogy, adds: “From a broader perspective, the study underscores how cutting-edge genetic research, in combination with careful exploration of the archaeological and historical context, can resolve centuries-old debates about the composition and origin of past populations”. While many questions remain, this work offers compelling evidence for direct connections between the Hun period population, the steppe and the Xiongnu Empire, deepening our understanding of the dynamic networks that linked East and West Eurasia in the past.
Gold animal figurine found in Árpás (Hungary), in a 5th century eastern-type burial.
This research project has been funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 856453 ERC-2019-SyG HistoGenes). HistoGenes is a research framework investigating the period of 400 to 900 CE in the Carpathian Basin from an interdisciplinary perspective.
Elephants, giraffes, pythons and other large species have higher cancer rates than smaller ones like mice, bats, and frogs, a new study has shown, overturning a 45-year-old belief about cancer in the animal kingdom.
The research, conducted by researchers from the University of Reading, University College London and The Johns Hopkins University School of Medicine, examined cancer data from 263 species across four major animal groups - amphibians, birds, mammals and reptiles. The findings challenge "Peto's paradox," a longstanding idea based on observations from 1977 that suggested there was no link between an animal's size and its cancer risk.
The study, published today (Monday, 24 February) in the journal Proceedings of the National Academy of Sciences (PNAS), revealed that bigger animals consistently show higher prevalence of both benign and malignant tumours. The researchers also discovered that species which evolved to be larger more rapidly, like elephants, developed better natural defences against cancer.
Professor Chris Venditti, senior author of the research at the University of Reading, said: "Everyone knows the myth that elephants are afraid of mice, but when it comes to cancer risk, mice are the ones who have less to fear. We've shown that larger species like elephants do face higher cancer rates - exactly what you'd expect given they have so many more cells that could go wrong.”
Keeping cancer in check
The study involved the analysis of the largest dataset of its kind to date. The researchers studied cancer records from veterinary autopsies of 31 amphibians, 79 birds, 90 mammals, and 63 reptiles. They used advanced statistical methods to analyse how cancer rates related to body size while accounting for how different species evolved.
Birds and mammals (which stop growing at a set size) and amphibians and reptiles (which can grow throughout their lives) were observed separately. Despite these differences in growth patterns, both groups showed the same overall trend - larger species had higher cancer rates. However, the study shows species that rapidly evolved to large sizes over short evolutionary timescales, like elephants, evolved improved mechanisms to control cell growth and prevent tumours. An elephant, for instance, has about the same cancer risk as a tiger - an animal just one-tenth its size.
Dr Joanna Baker, co-author from the University of Reading, added: "When species needed to grow larger, they also evolved remarkable defences against cancer. Elephants shouldn't fear their size - they developed sophisticated biological tools to keep cancer in check. It's a beautiful example of how evolution finds solutions to complex challenges."
Modern medicine makes it difficult to know exactly how humans fit this size-cancer pattern. The research shows a general trend where larger species have higher cancer rates, but also reveals how some species evolved better cancer defences as they grew larger. Overall, the findings support the idea that superior mechanisms of cellular defence - such as improved control of cell growth - have evolved at specific points in time and in larger species. This opens the door to new approaches to understanding the mechanisms responsible for cancer, potentially providing novel insight into human disease - and its treatment.
Budgies vs naked mole rats
On average, larger species get more cancer compared to smaller species. However, the researchers also identified a subset of species that get much more or much less cancer than you would expect given their body size. For example, the common budgie (Melopsittacus undulatus) was found to have rates of cancer more than 40 times higher than would be expected for its body size - weighing less than 30g. Conversely, the naked mole rat (Heterocephalus glaber), has almost no recorded prevalence of cancers.
Dr George Butler, lead author of the research at University College London and Johns Hopkins said: “Finding which animals are naturally better at fighting off cancer opens exciting new paths for research. By studying these successful species, we can better understand how cancers develop and potentially discover new ways to fight the disease. This could lead to breakthrough treatments in the future."
A computer-generated image showing single nickel (Ni) atoms embedded in silver, used “to enhance oxygen dissociation and enable efficient production of ethylene oxide, a commodity chemical,” says Charles Sykes.
Few people have heard of the chemical ethylene oxide, but all of us have used products that rely on it for their production, from antifreeze and plastics to textiles and disinfectants. It’s a “platform chemical”—the basis for many other chemicals—and there’s a $40 billion annual worldwide market for it.
The ethylene oxide production process emits millions of tons of CO2 into the atmosphere, which contributes to climate change. The process also currently requires chlorine, which is toxic. Now a team of researchers led by Tufts chemistry professor Charles Sykes has discovered an inexpensive way to potentially reduce CO2 emissions and decrease the need for chlorine to produce the chemical.
Writing in the journal Science, the researchers describe how adding small amounts of nickel atoms to silver catalysts made the reaction just as efficient, but without the need for chlorine that is currently used. This could revolutionize the production of the ubiquitous chemical ethylene oxide.
It was a long road to the discovery. Sykes, who is John Wade Professor of Chemistry, first discussed the idea with collaborator Matthew Montemore, a chemical engineering professor at Tulane University, six years ago. They were interested in exploring selective oxidation reactions, and settled on ethylene oxide production, which is made from ethylene and molecular oxygen.
Catalysts break the strong O2 bond, allowing single atoms of oxygen to bind with the ethylene to form ethylene oxide. (Catalysts are substances that increase the rate of a chemical reaction without undergoing chemical change themselves.) Silver is the main catalyst for making ethylene oxide, but it produces two molecules of CO2 for every molecule of ethylene oxide; adding chlorine brings it to about one molecule of CO2 per two ethylene oxide molecules produced, but there was still room for improvement.
Knowing the safety and environmental impacts of current industrial production methods that rely on chlorine, Sykes and Montemore looked for elements they could add to the silver catalyst to substitute for chlorine. “The answer was nickel,” Sykes says “which surprised us because we couldn’t find anything in the scientific or patent literature about nickel despite it being a common and inexpensive element used in many other catalytic processes. Could 70+ years of industrial R&D have missed it?”
Testing the Prediction
In his lab at Tufts, Sykes worked with graduate students Elizabeth Happel, AG25, and Laura Cramer, AG21, to do the fundamental experiments “to test Matthew Montemore’s prediction and see how far it could go towards application,” he says. The results were promising.
They used Sykes’ single-atom alloy concept—a fundamental approach to understanding and controlling chemical reactions that he had pioneered over a decade earlier. By adding nickel in the form of individual atoms to silver, they were able to carefully test how it would work as a catalyst. “It was fundamental research, but our results indicated that it may be applicable to real industrial catalysts,” Sykes says.
He enlisted Phillip Christopher, a professor of chemical engineering at the University of California Santa Barbara (UCSB), to make a new formulation of the silver catalyst by adding tiny amounts of nickel, to see how it might work. “Selective oxidation is one of the more challenging reactions, and so I wouldn’t have been surprised if it hadn’t have worked,” says Sykes. But it did.
“Incorporating nickel atoms into the silver catalyst by a reproducible protocol was a real technical hurdle that Anika Jalil, a Ph.D. student at UCSB, navigated impressively. The challenge in incorporating nickel could be why the effect we observed was never previously reported,” Christopher says.
Because nickel added to the catalyst improves the efficiency of the process, it might now be possible to lower the amount of CO2 that is released in the making of ethylene oxide. “I have worked on ethylene oxide catalysts since my PhD and was so surprised and excited by the magnitude of the effect nickel addition had,” Christopher says.
The team submitted a provisional patent in 2022 and an international patent in 2023. They are also in regular contact with a major commercial producer of ethylene oxide, interested in seeing if their discovery can be implemented in existing manufacturing facilities.
