Lung cancer does not decrease in line with reduced smoking

UMEA UNIVERSITY

 

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BENGT JÄRVHOLM, PROFESSOR AT DEPARTMENT OF PUBLIC HEALTH AND CLINICAL MEDICINE, UMEÅ UNIVERSITY, SWEDEN

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CREDIT: MATTIAS PETTERSSON

Despite the fact that the number of people who smoke has decreased very sharply in Sweden, the number of cases of lung cancer in the population is not decreasing as much as expected. Among women lung cancer has in fact increased. This is shown in a new study at Umeå University, Sweden. The study means that the view of how long smoking affects health may change.

“Smoking is undoubtedly the most important risk factor for lung cancer. It is therefore surprising that the decline in smoking is not yet more visible in the statistics. More research is needed to find out why this is the case,” says Bengt Järvholm, professor at the Department of Public Health and Clinical Medicine at Umeå University.

The number of people who smoke has been declining in Sweden for many years. Today, one of twenty Swedes, about five percent, among men and women state that they smoke daily. In the 1960s, about one in two Swedish men between the ages of 18 and 69 smoked. Women generally started smoking later in history than men. In a large study in 1963, only slightly more than one in ten women, 11 per cent, aged 50–69 smoked, while 46 per cent of men were smokers. Among women, it was mainly younger people who smoked in the 1960s.

According to previous research, the risk of developing lung cancer decreases sharply and quickly after quitting smoking. According to a British study, the number of people who had lung cancer before the age of 75 fell from 16 percent to three percent among those who quit smoking before the age of 50.

The Umeå researchers have compared the change in smoking habits in Sweden from the 1950s with the incidence of lung cancer between 1970 and 2021 in men and women aged 40–84 years. They studied how the risk varied among men and women in different age groups. Previous studies have shown that squamous cell cancer is the form of lung cancer that has the strongest association with smoking.

The results showed that the risk of being affected varied greatly depending on the type of lung cancer, age and gender. Based on previous studies, it would have been expected that the risk of cancer would have decreased among the elderly as well. However, lung cancer was as common in 1970 as in 2021 among men aged 75–79 years. The number of squamous cell cancer had fallen sharply, while in 2021 it had instead increased six-fold for the other common form of cancer, adenocarcinoma. The risk of squamous cell cancer had increased among women in the age group 75-79 years to the same level as among men. For adenocarcinoma, the risk was similar for women and men, despite the fact that there were large differences in smoking habits among women and men in the 1970s.

The study does not provide an answer as to why the development of lung cancer does not correspond well with expectations. For that, other types of studies are required. However, there are several possible explanations. One explanation may be that people may underreport their smoking, i.e. that the reduction in smoking may be smaller in reality. Another possible explanation may be that previous assumptions have been exaggerated about how quickly the risk of being affected decreases when you quit smoking. Nor can it be ruled out that other environmental or lifestyle factors may play a role; Even those who have never smoked can get lung cancer, although it is less common. The fact that the trend is so much worse for women than for men is due to the fact that Swedish women generally started smoking later in history than men.

“The results should certainly not be interpreted as it is useless to quit smoking. On the contrary, the study emphasizes the importance of quitting early, preferably never starting, as it may be the case that the risk of lung cancer is elevated for longer than we previously thought,” says Bengt Järvholm.

The study shows that if the risk of developing lung cancer in 2021 was as high as the risk in 1970 in men and women aged 40–84, approximately 2,250 men would have suffered from lung cancer in 2021 instead of 1695 cases, i.e. a decrease of 555 cases. Among women, there would have been 544 cases instead of the current 2,181 cases, i.e. there has been an increase of 1,637 cases of lung cancer.

The study is based on data from the National Board of Health and Welfare's cancer registry, which was compared with statistics on tobacco smoking from surveys and from the sale of cigarettes.

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JOURNAL

European Journal of Public Health

DOI

10.1093/eurpub/ckae050 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Changing smoking habits and the occurrence of lung cancer in Sweden—a population analysis

 

Why don't we stick to home physiotherapy exercises?

BEN-GURION UNIVERSITY OF THE NEGEV

BEER-SHEVA, Israel, April 2, 2024 – The lack of persistence in home physiotherapy exercises is a well-known problem hindering the effectiveness of treatment. It is especially evident in vestibular rehabilitation (exercises to treat dizziness and balance problems). Researchers from Ben-Gurion University of the Negev analyzed the barriers to conducting consistent home exercises and have published recommendations to overcome them in the leading physical therapy journal, The Journal of Neurologic Physical Therapy (JNPT).

Vestibular rehabilitation addresses abnormalities in the vestibular system, such as dizziness, gait instability, sensitivity to movement and blurred vision. Treatment is especially effective when consistently practiced at home.

To find a solution to the lack of consistent practice at home, a research group from the Department of Physiotherapy at Ben-Gurion University approached 39 patients doing vestibular rehabilitation and experienced physiotherapists to identify barriers.

 They found six barriers: motivation (lack of confidence in the effectiveness of the practice, boredom and lack of internal drive); increased symptoms during the practice (temporary worsening of dizziness, during or after the exercises); difficulties in time management (difficulty integrating practice into daily routine); lack of feedback and guidance (patients' limited understanding of how exercises should be done and their effect); psychosocial factors (what will the environment think?); and related medical deficiencies (such as neck pain and migraines).

The research team formulated recommendations for clinicians, which can significantly improve treatment outcomes and patients' quality of life. Thus, for example, to increase motivation – personal interaction and follow-up by a clinician would allow for greater attention to the exercises, availability and feedback conversations on the performance of the exercises – including initiated phone calls, text messages to patients in between visits to the clinic, would nurture motivation for the practice. Investing time and money should also increase motivation. In terms of time management – personalizing the exercises to fit into the patient's daily routine. For example, to practice a little bit at a time throughout the day and/or write in a daily diary. Patient guidance – the exercise instructions should include an explanation of the importance of the exercises, the expected symptoms, and the expected recovery time. Documenting improvement by providing quantitative and visual feedback, such as charts and graphs, should encourage continued practice.

"Our study provided a broad perspective for data analysis by both patients and treating physicians," explained Prof. Shelly Levy-Tzedek who led the research. "Identifying the common barriers to practice allowed us to build strategies that could improve adherence to home practices and, as a result, the effectiveness of treatment. This is a study that can be applied in any clinic and to any patient, and therefore an important guide for therapists."

This research was carried out as part of Liran Kalderon's doctoral dissertation in the Department of Physiotherapy at Ben-Gurion University of the Negev, under the joint supervision of Prof. Shelly Levy-Tzedek and Dr. Yoav Gimmon, and together with Azriel Kaplan and Dr. Amit Wolfovitz.

Photo Caption: Prof. Shelly Levy-Tzedek. Credit: Dani Machlis, Ben-Gurion University of the Negev: https://bgu.chorus.thirdlight.com/link/lvbxvpkl98qm-9xn58o/@/preview/1?o

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JOURNAL

Journal of Neurologic Physical Therapy

DOI

10.1097/NPT.0000000000000470 

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Barriers and Facilitators of Vestibular Rehabilitation: Patients and Physiotherapists’ Perspectives

 

Precise localization of miniature robots and surgical instruments inside the body

GERMAN CANCER RESEARCH CENTER (DEUTSCHES KREBSFORSCHUNGSZENTRUM, DKFZ)

In the medicine of the future, tiny robots will navigate independently through tissue and medical instruments will indicate their position inside the body during surgery. Both require doctors to be able to localize and control the devices precisely and in real time. Until now, there has been no suitable method for this. Scientists from the German Cancer Research Center (DKFZ) have now described a signaling method based on an oscillating magnet that can significantly improve such medical applications.

What until recently sounded like science fiction is now well advanced in development: Nanorobots that move independently through the body are expected to transport drugs, take measurements in tissue or perform surgical procedures. Magnetically driven nanorobots that navigate through the muscle, through the vitreous body of the eye or through the blood vessel system have already been developed.

However, there is a lack of sophisticated systems to track and control the activities of the robots deep inside the body in real time. Traditional imaging techniques are only suitable to a limited extent. Magnetic resonance imaging (MRI) is limited in temporal resolution, computer tomography (CT) is associated with radiation exposure and the strong scattering of sound waves limits the local resolution of ultrasound.

A team led by Tian Qiu from the DKFZ, Dresden site, has now invented a new method to solve this problem. The tiny device they have developed is based on a magnetic oscillator, i.e. a mechanically oscillating magnet located in a millimeter-sized housing. An external magnetic field can excite the magnet to vibrate mechanically. When the oscillation subsides again, this signal can be recorded with magnetic sensors. The basic principle is comparable to nuclear magnetic resonance in MRI. The researchers refer to the method as "Small-Scale Magneto-Oscillatory Localization" (SMOL). 

SMOL allows the position and orientation of the small device to be determined at a great distance (over 10 cm), very precisely (less than 1 mm) and in real time. In contrast to tracking methods based on static magnets, SMOL can detect movements in all six degrees of freedom and with significantly higher signal quality. As the device is based on weak magnetic fields, it is harmless to the body, wireless and compatible with many conventional devices and imaging techniques.

"There are many possible applications for the SMOL method," says Felix Fischer, first author of the current publication. "We have already integrated the system into miniature robots and instruments for minimally invasive surgery. A combination with capsule endoscopes or the marking of tumor tissue for very precise radiotherapy would be conceivable. Our method could also provide a decisive advantage for fully automated surgical robotics or augmented reality applications."

"SMOL only requires comparatively simple technical equipment. Due to its dimensions in the millimetre range, the oscillator can be integrated into many existing instruments, and there is still potential for further miniaturization. Thanks to its precise spatial and temporal resolution, our technique has the potential to significantly advance many medical procedures of the future," comments Tian Qiu, senior author of the current publication.

F. Fischer, C. Gletter, M. Jeong, T. Qiu: Magneto-oscillatory localization for small-scale robots.

npj Robotics 2024, DOI: https://doi.org/10.1038/s44182-024-00008-x

 

With more than 3,000 employees, the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) is Germany’s largest biomedical research institute. DKFZ scientists identify cancer risk factors, investigate how cancer progresses and develop new cancer prevention strategies. They are also developing new methods to diagnose tumors more precisely and treat cancer patients more successfully. The DKFZ's Cancer Information Service (KID) provides patients, interested citizens and experts with individual answers to questions relating to cancer.
To transfer promising approaches from cancer research to the clinic and thus improve the prognosis of cancer patients, the DKFZ cooperates with excellent research institutions and university hospitals throughout Germany:

National Center for Tumor Diseases (NCT, 6 sites)

German Cancer Consortium (DKTK, 8 sites)

Hopp Children's Cancer Center (KiTZ) Heidelberg

Helmholtz Institute for Translational Oncology (HI-TRON Mainz) - A Helmholtz Institute of the DKFZ

DKFZ-Hector Cancer Institute at the University Medical Center Mannheim

National Cancer Prevention Center (jointly with German Cancer Aid)

The DKFZ is 90 percent financed by the Federal Ministry of Education and Research and 10 percent by the state of Baden-Württemberg. The DKFZ is a member of the Helmholtz Association of German Research Centers.

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JOURNAL

npj Robotics

DOI

10.1038/s44182-024-00008-x 

 

Is it the school, or the students?

Study shows perceptions of “good” schools are heavily dependent on the preparation of the students entering them

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

Are schools that feature strong test scores highly effective, or do they mostly enroll students who are already well-prepared for success? A study co-authored by MIT scholars concludes that widely disseminated school quality ratings reflect the preparation and family background of their students as much or more than a school’s contribution to learning gains. 

Indeed, the study finds that many schools that receive relatively low ratings perform better than these ratings would imply. Conventional ratings, the research makes clear, are highly correlated with race. Specifically, many published school ratings are highly positively correlated with the share of the student body that is white.

“A school’s average outcomes reflect, to some extent, the demographic mix of the population it serves,” says MIT economist Josh Angrist, a Nobel Prize winner who has long analyzed education outcomes. Angrist is co-author of a newly published paper detailing the study’s results.

The study, which examines the Denver and New York City school districts, has the potential to significantly improve the way school quality is measured. Instead of raw aggregate measures like test scores, the study uses changes in test scores and a statistical adjustment for racial composition to compute more accurate measures of the causal effects that attending a particular school has on students’ learning gains. This methodologically sophisticated research builds on the fact that Denver and New York City both assign students to schools in ways that allow the researchers to mimic the conditions of a randomized trial.

In documenting a strong correlation between currently used rating systems and race, the study finds that white and Asian students tend to attend higher-rated schools, while Black and Hispanic students tend to be clustered at lower-rated schools. 

“Simple measures of school quality, which are based on the average statistics for the school, are invariably highly correlated with race, and those measures tend to be a misleading guide of what you can expect by sending your child to that school,” Angrist says. 

The paper, “Race and the Mismeasure of School Quality,” appears in the latest issue of the American Economic Review: Insights. The authors are Angrist, the Ford Professor of Economics at MIT; Peter Hull, a professor of economics at Brown University; Parag Pathak, the Class of 1922 Professor of Economics at MIT; and Christopher Walters PhD ’13, an associate professor of economics at the University of California at Berkeley. Angrist and Pathak are both professors in the MIT Department of Economics and co-founders of MIT’s Blueprint Labs, a research group that often examines school performance.

The study uses data provided by the Denver and New York City public school districts, where 6th-graders apply for seats at certain middle schools, and the districts use a school-assignment system. In these districts, students can opt for any school in the district, but some schools are oversubscribed. In these circumstances, the district uses a random lottery number to determine who gets a seat where. 

By virtue of the lottery inside the seat-assignment algorithm, otherwise-similar sets of students randomly attend an array of different schools. This facilitates comparisons that reveal causal effects of school attendance on learning gains, as in a randomized clinical trial of the sort used in medical research. Using math and English test scores, the researchers evaluated student progress in Denver from the 2012-2013 through the 2018-2019 school years, and in New York City from the 2016-2017 through 2018-2019 school years. 

Those school-assignment systems, it happens, are mechanisms some of the researchers have helped construct, allowing them to better grasp and measure the effects of school assignment. 

“An unexpected dividend of our work designing Denver and New York City’s centralized choice systems is that we see how students are rationed from [distributed among] schools,” says Pathak. “This leads to a research design that can isolate cause and effect.”

Ultimately, the study shows that much of the school-to-school variation in raw aggregate test scores stems from the types of students at any given school. This is a case of what researchers call “selection bias.” In this case, selection bias arises from the fact that more-advantaged families tend to prefer the same sets of schools. 

“The fundamental problem here is selection bias,” Angrist says. “In the case of schools, selection bias is very consequential and a big part of American life. A lot of decision-makers, whether they’re families or policymakers, are being misled by a kind of naïve interpretation of the data.” 

Indeed, Pathak notes, the preponderance of more simplistic school ratings today (found on many popular websites) not only creates a deceptive picture of how much value schools add for students, but has a self-reinforcing effect — since well-prepared and better-off families bid up housing costs near highly-rated schools.As the scholars write in the paper, “Biased rating schemes direct households to low-minority rather than high-quality schools, while penalizing schools that improve achievement for disadvantaged groups.” 

The research team hopes their study will lead districts to examine and improve the way they measure and report on school quality. To that end, Blueprint Labs is working with the New York City Department of Education to pilot a new ratings system later this year. They also plan additional work examining the way families respond to different sorts of information about school quality.

Given that the researchers are proposing to improve ratings in what they believe is a straightforward way, by accounting for student preparation and improvement, they think more officials and districts may be interested in updating their measurement practices. 

“We’re hopeful that the simple regression adjustment we propose makes it relatively easy for school districts to use our measure in practice,” Pathak says.

The research received support from the Walton Foundation and the National Science Foundation. 

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Written by Peter Dizikes, MIT News

Paper: “Race and the mismeasure of school quality”

https://www.aeaweb.org/articles?id=10.1257/aeri.20220292

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JOURNAL

American Economic Review Insights

DOI

10.1257/aeri.20220292 

ARTICLE TITLE

“Race and the mismeasure of school quality”

 

Music: Song lyrics have become simpler and more repetitive since 1980

SCIENTIFIC REPORTS

We have been alerted to a potential error in some of the coding used by the authors in their analyses and are looking into this as a matter of urgency. The authors are confident that the main findings of the paper will remain unaltered, however some aspects may be affected and we have removed two sentences from the press release to reflect this. We will provide an update if there are further developments. We apologise for any inconvenience caused.

The lyrics of English-language songs have become simpler and more repetitive over the past 40 years, according to a study published in Scientific Reports.

Eva Zangerle and colleagues analysed the lyrics of 12,000 English-language rap, country, pop, R&B, and rock songs (2,400 songs per genre) released between 1980 and 2020. The authors found that, in general, lyrics have become simpler and easier to understand over time and that the number of different words used within songs has decreased, particularly among rap and rock songs. They suggest that general increases in the repetitiveness of lyrics across multiple genres has led to lyrics becoming simpler overall. The authors speculate that the trend towards simpler lyrics could reflect changes in music consumption, such as increases in songs being played as background music.

The authors found that lyrics have tended to become more emotional and personal over time. Use of emotionally positive and negative words increased in rap songs, while the use of emotionally negative lyrics increased for R&B, pop and country songs. Additionally, all genres showed an increase in the use of anger-related words.

Additional analyses into the views of the 12,000 song lyrics on the online song lyric platform Genius revealed that the lyrics of older rock songs tend to be viewed more than those of newer rock songs but that the lyrics of newer country songs tend to be viewed more than those of older country songs. This could indicate that rock listeners prefer lyrics from older songs, while country listeners may prefer lyrics from newer songs.

The findings provide further insight into the evolution of music over the past 40 years.

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Article details

Song lyrics have become simpler and more repetitive over the last five decades

DOI: 10.1038/s41598-024-55742-x

Corresponding Author:

Eva Zangerle
University of Innsbruck, Innsbruck, Austria
Email: eva.zangerle@uibk.ac.at

 

Please link to the article in online versions of your report (the URL will go live after the embargo ends): https://www.nature.com/articles/s41598-024-55742-x.

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-024-55742-x 

ARTICLE TITLE

Song lyrics have become simpler and more repetitive over the last five decades

ARTICLE PUBLICATION DATE

28-Mar-2024

 

Building blocks for greener energy: Reconfigurable elastic metasurface akin to lego

POHANG UNIVERSITY OF SCIENCE & TECHNOLOGY (POSTECH)

 

IMAGE: 

(A) SCHEMATIC OF THE TIMOSHENKO-EHRENFEST BEAM-BASED RECONFIGURABLE ELASTIC METASURFACE (TREM) FOR MULTIFUNCTIONAL WAVE MANIPULATION (TOTAL REFLECTION, SELF-ACCELERATION, WAVE FOCUSING, AND ANOMALOUS REFRACTION). (B) IMAGE OF THE SUBSTRATE FOR THE (C) ASSEMBLY COMPONENTS DESIGNED BASED ON THE TIMOSHENKO-EHRENFEST BEAM THEORY. (D) THE ASSEMBLED TREM ON THE SUBSTRATE PLATE, WITH EACH COMPONENT CONFIGURED TO CONTROL THE INDIVIDUAL PHASE-SHIFT Ψ.

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CREDIT: POSTECH

Energy harvesting, an eco-friendly technology, extends beyond solar and wind power in generating electricity from unused or discarded energy in daily life, including vibrations generated by passing car engines or trains. Recent intriguing research has been announced, aiming to enhance the efficiency of energy harvesting using a new type of metasurface that can be reconfigured, resembling the assembly of LEGO bricks.

 

Professor Junsuk Rho from the Departments of Mechanical Engineering, Chemical Engineering, and Electrical Engineering and PhD/MS student Geon Lee from the Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH) have joined Professor Miso Kim from the School of Advanced Materials Science and Engineering at Sungkyunkwan University (SKKU) to collaborate on a research project. Together, they developed a multifunctional elastic metasurface that can be freely configured by attaching and detaching components for practical applications. This research was published in one of the international journals in materials science, Advanced Science.

 

Metamaterials are artificially designed structures that exploit the relationships among wavelengths to manipulate wave energy such as light, vibration, and sound. Harnessing this capability in energy harvesting allows for the gathering of elastic waves in piezoelectric components, thereby increasing the efficiency of electricity production. However, limitations in the theoretical analysis of the beams constituting metamaterials confine their operation to a single frequency and restrict their utility to specific purposes, posing challenges for their practical application in real structures.

 

The research team overcame these limitations by employing the Timoshenko–Ehrenfest beam theory instead of the conventional Euler-Bernoulli beam theory. What distinguishes the former is its consideration of the fundamental characteristics of elasticity, including shear deformation and rotational inertia effects of the beam. This study marks the first application of this theory to elastic metamaterial research.

 

The researchers succeeded in interpreting and modeling elastic metamaterials for phase modulation of elastic waves using the Timoshenko–Ehrenfest beam theory. Furthermore, they fabricated a new type of Timoshenko–Ehrenfest beam-based reconfigurable elastic metasurface (TREM) capable of attaching and detaching multiple structures. The TREM can reconstruct its surface depending on its application, enabling control over various wave phenomena such as anomalous wave refraction, wave focusing, self-accelerated wave propagation, and total wave reflection across a wide frequency range.

 

Notably, the team's TREM demonstrated outstanding effectiveness in harvesting elastic wave energy, enhancing the electrical output power of piezoelectric components by up to eight times. This highlights its value as a piezoelectric energy harvesting system.

 

Professor Junsuk Rho, the lead researcher, stated: “I believe that our newly developed metasurface, designed to operate across multifunctional and wide-frequency ranges, will prove invaluable in energy harvesting, most notably in the eco-friendly utilization of ambient energy. This technology, along with its applications in structural health monitoring, wireless sensing, and the Internet of Things, holds great potential for significant contributions across diverse fields.”

 

This work was supported by the N.EX.T. Impact Project of POSCO Holdings, as well as by funding from various programs including the Pioneer Research Center Program, the Regional Leading Research Center (RLRC) Program, and the Laboratory for Future Technology Program, all administered by the National Research Foundation of Korea and funded by the Ministry of Science and ICT of the Korean government.

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JOURNAL

Advanced Science

DOI

10.1002/advs.202400090 

ARTICLE TITLE

Timoshenko–Ehrenfest Beam-Based Reconfigurable Elastic Metasurfaces for Multifunctional Wave Manipulation

 

Exploring ‘sufficiency’: An overlooked strategy for protecting biodiversity?

PENSOFT PUBLISHERS

 

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METHODOLOGY

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CREDIT: MARIANNE HACHTMANN

A study from the Technical University Berlin suggests ‘sufficiency’ should be a more prominent strategy for protecting biodiversity.

Published in the open-access journal Nature Conservation, the paper analyses the intersection between biodiversity conservation and sufficiency strategies aimed at reducing consumption and resource use.

Study author Marianne Hachtmann notes that despite the established connection between excessive resource use by humans and biodiversity loss, there is limited explicit focus on how sufficiency strategies can support biodiversity preservation.

Reviewing literature from 2017 to 2021 and publications by nature conservation associations, the research identifies a notable gap in discussions linking sufficiency directly with biodiversity outcomes. Possible reasons for this may be the term’s political implications, lack of descriptiveness, as well as the use of other terms.

Furthermore, the lack of connection between sufficiency and biodiversity could be because they belong to different 'scientific spheres'. Linking the two terms thus requires a reflective, interdisciplinary perspective.

The study proposes a detailed sufficiency typology to foster a systematic approach towards integrating the term in biodiversity conservation efforts.

“The sufficiency typology developed here allows for a systematic integration of sufficiency into biodiversity conservation and thus a joint consideration of social and nature conservation concerns,” says Marianne Hachtmann, Technical University Berlin.

Policymakers, conservationists, and researchers are urged to prioritise sufficiency for the broader strategy for biodiversity conservation and sustainable living. The paper calls for further investigation into how adopting sufficiency strategies can be a crucial element in conserving biodiversity and ensuring a sustainable future.

Original source

Hachtmann M (2024) Linking sufficiency and the protection of biodiversity: An issue of political implications, framing, descriptiveness and interdisciplinarity? Nature Conservation 55: 83-102. https://doi.org/10.3897/natureconservation.55.118243

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JOURNAL

Nature Conservation

DOI

10.3897/natureconservation.55.118243 

ARTICLE TITLE

Linking sufficiency and the protection of biodiversity: An issue of political implications, framing, descriptiveness and interdisciplinarity?

 

Corn reduces arsenic toxicity in soil 

UNIVERSITY OF BASEL

 

IMAGE: 

CORN PLANTS IN A FIELD EXPERIMENT NEAR LIESBERG, BASELLAND, SWITZERLAND.

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CREDIT: UNIVERSITY OF BASEL, VERONICA CAGGÌA

When crops grow in arsenic-contaminated soil, this toxic element accumulates in the food chain. A study involving the University of Basel has now discovered a mechanism used by corn plants to reduce arsenic uptake: the key factor is a special substance released into the soil by the roots.

Arsenic is a toxic metalloid of natural origin. Arsenic-contaminated soils and waters are found all over the world, especially in southeastern Asian countries like Bangladesh, Vietnam, and China. Also, Switzerland has a few natural hot spots where arsenic is found in above-average concentrations. An example is soil at Liesberg in the canton of Baselland.

“The particular problem for plants is that arsenic behaves chemically similar to phosphorus,” says Professor Klaus Schlaeppi of the Department of Environmental Sciences at the University of Basel. Phosphorus is an important nutrient that plants take up through special transport channels in their roots. “The arsenic enters the plants through these channels.” As a result, more and more of the toxic substance accumulates in the biomass and gets into the food chain. On the long run, this negatively affects human health. High arsenic exposure can cause neurological damage and cancer, for example.

Roots release an antidote
But as Schlaeppi's team has now reported in the scientific journal PNAS, corn reduces arsenic toxicity through compounds known as benzoxazinoids. These substances are produced by most plants in the botanical group of grasses, which also includes corn and wheat. Corn produces particularly large quantities of benzoxazinoids, which are also released into soil through the root system. “There was already some evidence that corn takes up less arsenic than other plant species,” says Schlaeppi.

To test this hypothesis, the researchers grew corn plants in two types of soil: without arsenic and with high levels of arsenic. They performed the same experiment in parallel using corn plants that cannot produce benzoxazinoids because of a genetic defect. Schlaeppi performed these experiments in collaboration with the research groups of Professor Adrien Mestrot and Professor Matthias Erb at the University of Bern.

Mitigating arsenic toxicity
The result was unambiguous: benzoxazinoid-producing corn grew better in the arsenic-containing soil and accumulated significantly less arsenic in its biomass than the corn that did not exude benzoxazinoids. When the researchers mixed benzoxazinoids into the arsenic-containing soil, the mutant plants were also protected from arsenic toxicity. “This provided the proof that the presence of benzoxazinoids in soil reduced arsenic uptake into plants,” says Schlaeppi.

Next, the researchers wanted to find the underlying mechanism causing this effect. Analyses of the root microbiome indicated that bacteria and fungi were not involved. However, chemical soil analyses showed that a particularly toxic form of arsenic disappeared when benzoxazinoids are present. “This indicated that the benzoxazinoids transform arsenic in such a way that it can no longer be taken up through the root.” What chemical processes are involved is currently still unclear.

Further experiments showed that the positive effect of benzoxazinoids in soil persisted for a long time: even a second generation of corn still benefited from the benzoxazinoids discharge of the first generation.

“One application of these findings would be to cultivate at arsenic-contaminated locations plant varieties that release more benzoxazinoids,” says Schlaeppi. Hyper-emitting plants could be generated through classic breeding or targeted genetic modifications. “This way we could be more certain that less arsenic is entering the food chain.”

Seedlings of corn plants in a field experiment near Liesberg. W22 denotes the plants that produce benzoxazinoids. The bx1 corn plants lack the ability to produce these substances.

CREDIT

University of Basel, Veronica Caggìa

First author Veronica Caggìa measures the chlorophyll content of maize leaves. 

These measurements provide an approximation for photosynthesis and plant health.

CREDIT

University of Basel, Antoine Baud

JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2314261121