Tag Archives: gut health

London Underground polluted with metallic particles small enough to enter human bloodstream

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The London Underground is polluted with ultrafine metallic particles small enough to end up in the human bloodstream, according to University of Cambridge researchers. These particles are so small that they are likely being underestimated in surveys of pollution in the world’s oldest metro system.

The researchers carried out a new type of pollution analysis, using magnetism to study dust samples from Underground ticket halls, platforms and operator cabins.

The team found that the samples contained high levels of a type of iron oxide called maghemite. Since it takes time for iron to oxidise into maghemite, the results suggest that pollution particles are suspended for long periods, due to poor ventilation throughout the Underground, particularly on station platforms.

Some of the particles are as small as five nanometres in diameter: small enough to be inhaled and end up in the bloodstream, but too small to be captured by typical methods of pollution monitoring. However, it is not clear whether these particles pose a health risk.

Other studies have looked at overall pollution levels on the Underground and the associated health risks, but this is the first time that the size and type of particles has been analysed in detail. The researchers suggest that periodic removal of dust from Underground tunnels, as well as magnetic monitoring of pollution levels, could improve air quality throughout the network. Their results are reported in the journal Scientific Reports.

The London Underground carries five million passengers per day. Multiple studies have shown that air pollution levels on the Underground are higher than those in London more broadly, and beyond the World Health Organization’s (WHO) defined limits. Earlier studies have also suggested that most of the particulate matter on the Underground is generated as the wheels, tracks and brakes grind against one another, throwing up tiny, iron-rich particles.

“Since most of these air pollution particles are metallic, the Underground is an ideal place to test whether magnetism can be an effective way to monitor pollution,” said Professor Richard Harrison from Cambridge’s Department of Earth Sciences, the paper’s senior author. “Normally, we study magnetism as it relates to planets, but we decided to explore how those techniques could be applied to different areas, including air pollution.”

Pollution levels are normally monitored using standard air filters, but these cannot capture ultrafine particles, and they do not detect what kinds of particles are contained within the particulate matter.

“I started studying environmental magnetism as part of my PhD, looking at whether low-cost monitoring techniques could be used to characterise pollution levels and sources,” said lead author Hassan Sheikh from Cambridge’s Department of Earth Sciences. “The Underground is a well-defined micro-environment, so it’s an ideal place to do this type of study.”

Working with colleagues from Cambridge’s Department of Materials Science and Metallurgy, Sheikh and Harrison analysed 39 dust samples from the London Underground, provided by Transport for London (TfL). The samples were collected in 2019 and 2021 from platforms, ticket halls, and train operator cabins on the Piccadilly, Northern, Central, Bakerloo, Victoria, Northern, District and Jubilee lines. The sampling included major stations such as King’s Cross St Pancras, Paddington, and Oxford Circus.

The researchers used magnetic fingerprinting, 3D imaging and nanoscale microscopy to characterise the structure, size, shape, composition and magnetic properties of particles contained in the samples. Earlier studies have shown that 50% of the pollution particles in the Underground are iron-rich, but the Cambridge team were able to look in much closer detail. They found a high abundance of maghemite particles, ranging in diameter from five to 500 nanometres, and with an average diameter of 10 nanometres. Some particles formed larger clusters with diameters between 100 and 2,000 nanometres.

“The abundance of these very fine particles was surprising,” said Sheikh. “The magnetic properties of iron oxides fundamentally change as the particle size changes. In addition, the size range where those changes happen is the same as where air pollution becomes a health risk.”

While the researchers did not look at whether these maghemite particles pose a direct health risk, they say that their characterisation methods could be useful in future studies.

“If you’re going to answer the question of whether these particles are bad for your health, you first need to know what the particles are made of and what their properties are,” said Sheikh.

“Our techniques give a much more refined picture of pollution in the Underground,” said Harrison. “We can measure particles that are small enough to be inhaled and enter the bloodstream. Typical pollution monitoring doesn’t give you a good picture of the very small stuff.”

The researchers say that due to poor ventilation in the Underground, iron-rich dust can be resuspended in the air when trains arrive at platforms, making the air quality on platforms worse than in ticket halls or in operator cabins.

Given the magnetic nature of the resuspended dust, the researchers suggest that an efficient removal system might be magnetic filters in ventilation, cleaning of the tracks and tunnel walls, or placing screen doors between platforms and trains.

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“Walnuts” the new brain food for stressed university students

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Stressed university students might want to add walnuts to their daily diet in the weeks leading up to their next exam.

A new  clinical trial of undergraduate students during their university studies has shown positive effects of walnut consumption on self-reported measures of mental health and biomarkers of general health.

The University of South Australia study, published in the journal Nutrients, also suggests that walnuts may counteract the effects of academic stress on the gut microbiota during periods of stress, especially in females.

Lead researchers, PhD student Mauritz Herselman and Associate Professor Larisa Bobrovskaya, say the results add to the growing body of evidence linking walnuts with improved brain and gut health.

Walnuts may counteract the effects of academic stress on the gut microbiota during periods of stress, especially in women./CREDIT:Open Verse

“Students experience academic stress throughout their studies, which has a negative effect on their mental health, and they are particularly vulnerable during exam periods,” Herselman says.

Eighty undergraduate students split into treatment and control groups were clinically assessed in three intervals, at the beginning of a 13-week university semester, during the examination period and two weeks after the examination period. Those in the treatment group were given walnuts to consume daily for 16 weeks over these three intervals.

“We found that those who consumed about half a cup of walnuts every day showed improvements in self-reported mental health indicators.  Walnut consumers also showed improved metabolic biomarkers and overall sleep quality in the longer term.”

Students in the control group reported increased stress and depression levels in the leadup to exams but those in the treatment group did not. The walnut consumers also reported a significant drop in feelings associated with depression between the first and final visits, compared to the controls.

Previous research has shown that walnuts are full of omega-3 fatty acids, antioxidants, as well as melatonin (sleep inducing hormone), polyphenols, folate and vitamin E, all of which promote a healthy brain and gut.

“The World Health Organization has recently stated that at least 75 per cent of mental health disorders affect people under the age of 24 years, making undergraduate students particularly vulnerable to mental health problems,” Herselman says.

Assoc Prof Larisa Bobrovskaya says mental health disorders are common in university students and can adversely affect students’ academic performance and long-term physical health.

“We have shown that consuming walnuts during stressful periods can improve mental health and general wellbeing in university students, as well as being a healthy and delicious snack and a versatile ingredient in many recipes, to fight some negative effects of academic stress,” Assoc Prof Bobrovskaya says.

“Due to fewer numbers of males in the study, more research is needed to establish sex-dependent effects of walnuts and academic stress in university students. It’s also possible that a placebo effect might have come into play as this was not a blind study.”

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Novel device: ‘Surface mapping’ a reliable diagnostic tool for gut health

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Non-invasive sensors laid on the skin’s surface to measure bioelectrical activity could offer a better alternative for patients suffering with poor gut health.

Stefan Calder, a recent PhD graduate at the Auckland Bioengineering Institute (ABI), at Waipapa Taumata Rau, University of Auckland is the lead and joint-first author for two papers published in prestigious scientific journals this month on gut health. Stefan says gastric disorders are increasingly prevalent in humans, but reliable non-invasive tools to objectively assess gastric function are lacking.

“Many people suffering with chronic gut issues are on a constant diagnostic treadmill of antibiotics or proton pump inhibitors until they are sent for an endoscopy. A reliable surface-based recording could bridge the gap between symptom-based diagnostics and the more invasive minor surgery tests.”

Like the rhythmic beatings of the heart, gut movements depend on bioelectrical activity – but the electrical activity in the gut has been much more difficult to reliably detect. Researchers at ABI and the Faculty of Medical and Health Sciences’ Department of Surgery have employed a novel device using a sticky patch of sensors and a recording device and associated techniques to create a new and reliable non-invasive tool to map electrical waves from the stomach.

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Coined “Body Surface Gastric Mapping” (BSGM), the method has proven a reliable detector of gastric slow wave activity and has now led to an exciting and unexpected discovery identifying two distinct disease subgroups in chronic nausea and vomiting syndromes.

BSGM has shown to reliably record bio-electrical activity on the gut’s surface and accurately detect changes in both the frequency or rhythm, and direction of electromagnetic waves with intricate detail.

The degree of difference in bio-electrical activity between healthy people and patients with chronic nausea and vomiting syndromes defined by the novel gastric mapping device was set to explore. While previous surgical and non-invasive studies have shown that gastric dysfunctions are associated with abnormal bio-electrical slow waves, the researchers found surprising results.

“Approximately two-thirds of the symptomatic patient group had completely normal bio-electrical activity, while the rest had abnormal activity. We realised there were two sub types of what was previously considered a single disease.

“This may go on to explain or further classify that single disease into two diseases based on different mechanisms. For example, abnormal bioelectrical activity is likely to point to something intrinsically wrong with the stomach itself, but for those patients who show a completely normal slow wave propagation, their issue is likely arising from somewhere else.

“This idea of recording electrical activity on the body’s surface has been around for a long time. ECG machines, recording electrical activity have gained diagnostic acceptance for the last 100 years, but in the gut that is not the case. Through these studies we have validated a device and process that can reliably and accurately evidence bioelectrical activity in the stomach. We also show that bioactivity in the stomach can be a useful biological marker for disease.

“With this bio-electrical information on hand to inform clinical guidance or treatment, people experiencing chronic vomiting or nausea may be directed to different pathways and may receive diagnosis and more appropriate treatment options sooner.”