Placental inflammation could explain link between air pollution and pregnancy complications, NIH-funded study in mice suggests

The increase in pregnancy complications linked to air pollution exposure could result from the pollutants’ direct effects on the placenta, suggests a study in mice funded by the National Institutes of Health. Placentas of mice exposed to a mixture of common urban air pollutants before and during pregnancy were inflamed and had a loss of blood vessel cells. The study authors say the findings could provide insight into how air pollution might affect pregnancies and lead to strategies for preventing pregnancy complications.

The study was conducted by Sherin U. Devaskar, M.D., the David Geffen School of Medicine at UCLA, and colleagues. It appears in Scientific Reports. Funding was provided by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development.


Previous studies have found that exposure to air pollution during pregnancy is associated with preterm birth, gestational diabetes, and preeclampsia, a blood pressure disorder.

In the current study, researchers exposed female mice to a mix of air pollutants found in urban areas beginning two months before conception and throughout pregnancy. Using various cellular and molecular techniques, they analyzed the animals’ placental cells.


Compared to placentas of mice exposed only to saline solution, placentas of mice exposed to air pollutants had fewer blood vessel cells. Maternal immune cells also attacked the pollutants accumulated in the placenta cells nearest the uterus, resulting in inflammation and damage to the blood vessel cells.


A maternal immune attack on the cells of the placenta could disrupt the supply of oxygen and nutrients to the fetus, potentially resulting in pregnancy complications, such as preterm labor or preeclampsia.

“The cellular changes we have observed could provide the missing link between exposure to air pollutants and adverse pregnancy outcomes, thereby helping to focus development on preventive strategies for at-risk pregnancies,” Dr. Devaskar said.


Tosevska, A, et al.  Integrated analysis of an in vivo model of intra‑nasal exposure to instilled air pollutants reveals cell‑type specific responses in the placenta. Scientific Reports. 2022. 10.1038/s41598-022-12340-z

Science Update: Placental inflammation could explain link between air pollution and pregnancy complications, NIH-funded study in mice suggests | NICHD – Eunice Kennedy Shriver National Institute of Child Health and Human Development
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Car tyres produce vastly more particle pollution than exhausts, tests show

Almost 2,000 times more particle pollution is produced by tyre wear than is pumped out of the exhausts of modern cars, tests have shown.

The tyre particles pollute air, water and soil and contain a wide range of toxic organic compounds, including known carcinogens, the analysts say, suggesting tyre pollution could rapidly become a major issue for regulators.

Air pollution causes millions of early deaths a year globally. The requirement for better filters has meant particle emissions from tailpipes in developed countries are now much lower in new cars, with those in Europe far below the legal limit. However, the increasing weight of cars means more particles are being thrown off by tyres as they wear on the road.

The tests also revealed that tyres produce more than 1tn ultrafine particles for each kilometre driven, meaning particles smaller than 23 nanometres. These are also emitted from exhausts and are of special concern to health, as their size means they can enter organs via the bloodstream. Particles below 23nm are hard to measure and are not currently regulated in either the EU or US.

“Tyres are rapidly eclipsing the tailpipe as a major source of emissions from vehicles,” said Nick Molden, at Emissions Analytics, the leading independent emissions testing company that did the research. “Tailpipes are now so clean for pollutants that, if you were starting out afresh, you wouldn’t even bother regulating them.”

Molden said an initial estimate of tyre particle emissions prompted the new work. “We came to a bewildering amount of material being released into the environment – 300,000 tonnes of tyre rubber in the UK and US, just from cars and vans every year.”

There are currently no regulations on the wear rate of tyres and little regulation on the chemicals they contain. Emissions Analytics has now determined the chemicals present in 250 different types of tyres, which are usually made from synthetic rubber, derived from crude oil. “There are hundreds and hundreds of chemicals, many of which are carcinogenic,” Molden said. “When you multiply it by the total wear rates, you get to some very staggering figures as to what’s being released.”

The wear rate of different tyre brands varied substantially and the toxic chemical content varied even more, he said, showing low-cost changes were feasible to cut their environmental impact.

“You could do a lot by eliminating the most toxic tyres,” he said. “It’s not about stopping people driving, or having to invent completely different new tyres. If you could eliminate the worst half, and maybe bring them in line with the best in class, you can make a massive difference. But at the moment, there’s no regulatory tool, there’s no surveillance.”

The tests of tyre wear were done on 14 different brands using a Mercedes C-Class driven normally on the road, with some tested over their full lifetime. High-precision scales measured the weight lost by the tyres and a sampling system that collects particles behind the tyres while driving assessed the mass, number and size of particles, down to 6nm. The real-world exhaust emissions were measured across four petrol SUVs, the most popular new cars today, using models from 2019 and 2020.

Used tyres produced 36 milligrams of particles each kilometre, 1,850 times higher than the 0.02 mg/km average from the exhausts. A very aggressive – though legal – driving style sent particle emissions soaring, to 5,760 mg/km.

Far more small particles are produced by the tyres than large ones. This means that while the vast majority of the particles by number are small enough to become airborne and contribute to air pollution, these represent only 11% of the particles by weight. Nonetheless, tyres still produce hundreds of times more airborne particles by weight than the exhausts.

The average weight of all cars has been increasing. But there has been particular debate over whether battery electric vehicles (BEVs), which are heavier than conventional cars and can have greater wheel torque, may lead to more tyre particles being produced. Molden said it would depend on driving style, with gentle EV drivers producing fewer particles than fossil-fuelled cars driven badly, though on average he expected slightly higher tyre particles from BEVs.

Dr James Tate, at the University of Leeds’ Institute for Transport Studies in the UK, said the tyre test results were credible. “But it is very important to note that BEVs are becoming lighter very fast,” he said. “By 2024-25 we expect BEVs and [fossil-fuelled] city cars will have comparable weights. Only high-end, large BEVs with high capacity batteries will weigh more.”

Dr James Tate, at the University of Leeds’ Institute for Transport Studies in the UK, said the tyre test results were credible. “But it is very important to note that BEVs are becoming lighter very fast,” he said. “By 2024-25 we expect BEVs and [fossil-fuelled] city cars will have comparable weights. Only high-end, large BEVs with high capacity batteries will weigh more.”

“The US is more advanced in their thinking about [the impacts of tyre particles],” said Molden. “The European Union is behind the curve. Overall, it’s early days, but this could be a big issue.”

Car tyres produce vastly more particle pollution than exhausts, tests show | Pollution | The Guardian

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Severe Covid cases ‘more likely in highly polluted areas’

Air pollutant nitrogen dioxide may contribute to intensive care admissions, German study finds

People who contract Covid-19 are more likely to suffer severe symptoms if they have been exposed to air pollution for long periods.

A study found that people who live in places where there are high levels of the atmospheric pollutant nitrogen dioxide had higher chances of ending up in intensive care units (ICUs) or of needing mechanical ventilation after they had caught Covid.

Nitrogen dioxide is released into the atmosphere when fossil fuels are burned, and the gas is known to have harmful effects on people’s lungs. In particular, endothelial cells – which form a thin membrane lining the inside of the heart and blood vessels – become damaged, and this inhibits the transfer of oxygen from inhaled breath to a person’s blood.

“Our results show a positive association between long-term nitrogen dioxide exposure and Covid-19 fatality and Covid-19 incidence rate,” said the team of German researchers, who were led by Susanne Koch, of Universitätsmedizin Berlin, a large teaching hospital.

Scientists had previously made links between Covid and air pollution, but few studies have concentrated on cases that were particularly severe or on underlying health conditions in those affected by the disease.

Koch and her team used air pollution data to calculate average levels of nitrogen dioxide for each county in Germany. The highest was found in Frankfurt, while the lowest was experienced in Suhl, a small county in Thuringia, the group revealed in its report, which was presented last week to Euroanaesthesia, the annual meeting of the European Society of Anaesthesiology and Intensive Care in Milan.

The group also studied data on how many Covid patients in German hospitals had required ICU treatment and mechanical ventilation during one month in 2020. These figures were adjusted for other factors, such as pre-existing health conditions.

After analysing their results, the team reported that on average, 28 ICU beds and 19 ventilators were needed for Covid patients in each of the 10 counties that had the lowest long-term nitrogen dioxide exposure. These figures contrasted with an average of 144 ICU beds and 102 ventilators needed in the 10 counties with the highest long-term exposure.

The research has worrying implications. In the UK, 75% of urban areas in 2019 had illegal levels of air pollution, underscoring the fact that the British government has made almost no progress on legal obligations that should have been met in 2010. During lockdown, there was a temporary decrease in nitrogen in some areas. However, traffic and pollution are returning to past levels in many towns and cities.

According to the Royal College of Physicians, air pollution causes the equivalent of 40,000 early deaths a year, and has been linked to cancer, asthma, stroke and heart disease, diabetes, obesity and changes linked to dementia. Now evidence is mounting that Covid should be added to this list.

The German study did not prove a causative relationship between air pollution and severe Covid, the researchers admitted. However, they did suggest a plausible causal link that could explain the relationship between severe Covid and levels of nitrogen dioxide in the atmosphere.

Coronavirus is known to bind to the Ace-2 receptor when it enters cells after infecting a person. This receptor has many key roles, one of which involves helping the body to regulate levels of angiotensin II, a protein that increases inflammation. In other words, Ace-2 helps to put the brakes on inflammation.

However, when Covid binds to Ace-2, these brakes are removed. It is also known that air pollution causes a similar release of controls over angiotensin II. So the combination of Covid and long-term air pollution exposure would lead to more severe inflammation, more severe Covid and more need for ICUs and mechanical ventilation, the team argued.

“Exposure to ambient air pollution can contribute a range of other conditions, including heart attacks, strokes, asthma and lung cancer, and will continue to harm health long after the Covid-19 pandemic ends,” added Koch. “A transition to renewable energy, clean transportation and sustainable agriculture is urgently needed to improve air quality. Reducing emissions won’t just help to limit climate crisis, it will improve the health and the quality of life of people around the world.”

Severe Covid cases ‘more likely in highly polluted areas’ | Coronavirus | The Guardian

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Mouse study links air pollution exposure to adverse outcomes in pregnancy

A new study in mice by UCLA scientists reveals how exposure to traffic-related air pollutants causes cellular changes in the placenta that can lead to pregnancy complications and affect the health of both mother and offspring.

The researchers found that the cellular changes caused by chronic exposure to air pollutants were related to immune activation by foreign substances entering the blood from the lungs. This immune response attacks some of the placental cells that are required to maintain the placenta structurally, and most importantly, the blood flow from mother to developing baby.

Although previous research has analyzed the effect of air pollution on pregnancy, those studies did not utilize cell-specific methods or focus on molecular signatures of the placenta. This study is the first to assess how such exposure can negatively affect the placenta, leading to adverse outcomes in pregnancy.

One group of female mice was exposed to environmental air pollutants nasally starting two months before conception and during pregnancy, while the control group of mice was exposed to saline. By the end of the study, tissue samples indicated that inhaled air pollutants had compromised the composition of the placental cells and molecular signatures. Researchers also identified inflammation in the mucosal lining of the uterus triggered by pollution.

The placenta is essential for a successful pregnancy and for maintaining the health of both the mother and the baby. These study findings suggest that maternal cells of immunity may be responsible for destruction of vital vascular cells in the placenta. This auto-destruction of placental structures can disrupt the maintenance of a healthy pregnancy or at least affect nutrient supply from the mother to the baby, with the potential for adverse pregnancy consequences or outcomes such as preterm labor or uteroplacental insufficiency as encountered in pre-eclampsia.

“The cellular changes we have observed could provide the missing link between exposure to air pollutants and adverse pregnancy outcomes, thereby helping to focus development of preventive strategies for at-risk pregnancies,” said Dr. Sherin Devaskar, lead author of the study and physician-in-chief of UCLA Mattel Children’s Hospital and distinguished professor of pediatrics at the David Geffen School of Medicine at UCLA.

The research also underscores the need to examine the timing of exposure and whether acute v. chronic exposures have different effects. The authors also plan to study dietary interventions to alleviate distress on placental molecular signatures, nutrient supply and development.

The study is published in Scientific Reports.

The collaborative study also involved Dr. Suhas G. Kallapur, chief of neonatology and developmental biology; Amit Ganguly, staff research associate; Shubhamoy Ghosh, Ph.D., assistant project scientist; Monica Cappelletti, Ph.D., adjunct assistant professor of pathology and laboratory medicine, all four in the department of Pediatrics-Neonatology at UCLA; Matteo Pellegrini, a professor of molecular, cell and developmental biology at UCLA and Anela Tosevska, Ph.D., bioinformatics scientist in the division of rheumatology, internal medicine at Medical University of Vienna, Austria.

Mouse study links air pollution exposure to adverse outcomes in pregnancy
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An invisible tango with death as Bangladesh deals with pollution: Statesman

More than 215,000 people in Bangladesh succumbed to pollution in 2019. The ever lurking, at times invisible, killer – air pollution – alone claimed about 175,000 lives.

Water pollution was responsible for 30,000 deaths, while soil contamination, lead pollution, and occupational hazard-related pollution factors, including exposure to harmful chemicals and substances at work, made up for the rest of the death pie. This was revealed in a recent report titled “Pollution and Health: A Progress Update,” by the medical journal The Lancet.

While these numbers are new, the scenario is not. This dark underbelly of the growing, flourishing nation is known to all of us. Day in and day out, we breathe, we drink, we eat, we touch death like it is nobody’s business. In fact, for us, it is business as usual. Unfortunately, for our lawmakers and the government, this daily brush of the common people with death has also become an acceptable norm, which is why, despite the publication of multiple reports flagging this morose reality and the concerns raised by various quarters, little to no action has been taken to rectify this.

As late as March this year, it was revealed in a report by US-based organisations Health Effects Institute (HEI) and the Institute for Health Metrics and Evaluation (IHME) that, on an average, almost three years of a person’s life expectancy is cut by air pollution in Bangladesh. The report, titled “State of Global Air 2020: How Does Air Pollution Affect Life Expectancy around the World?”, added that outdoor air pollution is responsible for reducing 1.16 years, while indoor air pollution is responsible for reducing 1.53 years.

And Bangladesh often, unfortunately, finds itself at the top of the list of the most air-polluted countries in the world, based on the AQI score. According to IQAir, Bangladesh was the most air-polluted country in the world in 2021 with an average AQI of 161.

Despite these, the brick kilns keep operating at full throttle, non-compliant factories keep emitting harmful gases and discharging toxic wastes in rivers and water bodies, unfit vehicles keep polluting the air, and biomass burning, fossil fuel combustion, and dust from the various ongoing development works keep choking the life out of us. And no one bothers to take any measure to stop these.

Similarly, water pollution has exposed us to various health complications, including diarrhoea and cholera outbreaks, among other diseases. Over the years, we have allowed industries to discharge their chemical and factory wastes into the rivers without a worry, which has made the waters of our rivers so toxic and polluted that they have now become hotbeds for various diseases, including harmful skin diseases and cancer. A dip in the Buriganga, and one would emerge carrying a host of germs and bacteria, resulting in immediate reactions.

And while water sources have been compromised, the lack of an efficient water purification and distribution system by Wasa has exposed the population, especially in the big cities, to deadly bacteria and viruses, which can cause a wide variety of fatal liver diseases, including Hepatitis A and Hepatitis E.

An invisible tango with death as Bangladesh deals with pollution: Statesman | The Straits Times
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Size of air pollution particles may affect a person’s risk of dying from stroke, study finds

Living in areas with higher air pollution is associated with an increased risk of in-hospital death from stroke, and the risk varies depending on the size of the air pollution particles, according to a new study published in the May 25, 2022, online issue of Neurology®, the medical journal of the American Academy of Neurology.

The study looked at three sizes of air pollution particulate matter. Particulate matter consists of liquids or solids suspended in air. Submicron particulate matter, PM1, is less than one micron in diameter and includes soot and smog. Fine particulate matter, PM2.5, is less than 2.5 microns in diameter and includes fly ash from coal combustion. Respirable particulate matter, PM10, is less than 10 microns in diameter and includes cement dust.

“Air pollution has been previously linked to a greater risk of stroke, and stroke is a leading cause of death worldwide. What is lesser known is how the different sizes of particulate matter affect that risk. Our research found that the size of air pollution particles may affect a person’s risk of dying from stroke.”

Hualiang Lin, PhD, study author, Sun Yat-sen University in Guangzhou, China

For the study, researchers examined electronic medical records in China to identify over 3.1 million hospitalizations for stroke, both ischemic stroke caused by a blood clot, and hemorrhagic stroke caused by bleeding in the brain. Participants had an average age of 67. Of this group, 32,140 people, or 1%, died of stroke while hospitalized.

Researchers identified individual levels of air pollution exposure for each participant by using their home addresses and an air pollution data source that records daily concentrations of different types of particulate matter. Researchers then calculated seven-day air pollution exposure immediately before hospitalization for stroke, which was 31.38 micrograms per cubic meter (µg/m3) of PM1, 45.43 µg/m3 of PM2.5 and 78.75 µg/m3 of PM10. They also calculated a person’s average daily exposure to pollution particles in the year before hospitalization, which was 32.98 µg/m3 of PM1, 49.08 µg/m3 of PM2.5 and 87.32 µg/m3 of PM10.

After adjusting for factors such as age, sex, socioeconomic status, diabetes and high blood pressure, researchers found each 10 μg/m3 increase in annual average exposure to particulate matter was associated with increased risk of dying of stroke while hospitalized, with a 24% greater risk for exposure to PM1, a 11% greater risk for exposure to PM2.5, and a 9% greater risk for exposure to PM10. The seven-day average exposure to particulate matter included a 6% increased risk for exposure to PM1, a 4% increased risk for exposure to PM2.5, and a 3% increased risk for exposure to PM10.

The risks were stronger in people with ischemic stroke than in people with hemorrhagic stroke. The greatest risk of death from stroke was in people with ischemic stroke and exposure to the smallest air pollution particles, PM1.

Yet researchers also found that a reduction in PM10 would have the largest impact on reducing overall deaths from stroke, reducing the number of hospital deaths by 10% for short-term exposure and 21% for long-term exposure.

Lin said it is important to note that the study results do not prove that air pollution causes stroke deaths, they only show an association.

“Our study includes measurements of PM1, which may be small enough to be inhaled deeply into lungs, pass through lung tissue, and circulate in the bloodstream,” said Lin. “Obtaining a deeper understanding of the risk factors of all particulate matter sizes and the magnitude of their possible effects may help reduce the number of deaths and improve the outcomes for people with stroke.”

A limitation of the study was that results were not adjusted for a person’s smoking status or the severity of stroke. Researchers also examined air pollution exposure only at a person’s current residence and not at previous residences.

Source:American Academy of NeurologyJournal reference:Cai, M., et al. (2022) Association of Ambient Particulate Matter Pollution of Different Sizes With In-Hospital Case Fatality Among Stroke Patients in China. Neurology.

Size of air pollution particles may affect a person’s risk of dying from stroke, study finds
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Air pollution linked to more severe COVID-19: study

Several common air pollutants are linked to more severe outcomes following a coronavirus infection, a new study has found. 

Individuals who lived in areas of Ontario, Canada with higher levels of three common air pollutants — fine particulate matter, nitrogen dioxide and ground-level ozone — were at increased risk of being admitted to the intensive care unit, according to the authors, who published their findings on Tuesday in the Canadian Medical Association Journal. 

Chronic exposure to ozone specifically carried an elevated risk of death from COVID-19, the scientists determined. 

To draw these conclusions, researchers from the Canadian government’s Health Canada analyzed data on all 151,105 people ages 20 years and older who had confirmed coronavirus infections in 2020 in Ontario. 

Information about fine particulate matter, nitrogen dioxide and ground-level ozone was readily available to the researchers, as these substances are all regularly monitored by the Canadian government, the authors noted. 

These pollutants are emitted from a variety of different sources, including fuel combustion and reactions of volatile organic compounds or other chemicals. 

The scientists calculated each infected individual’s long-term exposure to the three air pollutants based on their residence from 2015-2019, according to the study. 

The authors excluded infected individuals living in long-term care facilities and adjusted for date of diagnosis, sex, age, essential worker status, socioeconomics, healthcare access and other factors. 

Long-term exposure to air pollution, the authors explained, could increase the risk of developing severe COVID-19 by several different mechanisms. For example, air pollutants can reduce immune responses and antimicrobial activities in the lungs, thereby boosting viral loads, according to the authors. 

These substances can also cause chronic inflammation and the over expression of a specific receptor protein that enables the entry of coronavirus into human cells, the researchers added. 

“Given the ongoing pandemic, our findings that underscore the link between chronic exposure to air pollution and more severe COVID-19 could have important implications for public health and health systems,” the authors stated.

Air pollution linked to more severe COVID-19: study | The Hill
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AFRICA: The continent tops a global ranking on pollution levels

The results of the “Global Health” study published recently in the British scientific journal The Lancet, reveal that the African continent is the most affected of the 9 million deaths caused annually by air pollution across the planet. This phenomenon, which affects people and biodiversity, is increasingly attracting the attention of African policy makers.

Chad, Central African Republic (CAR), Niger, Burkina Faso, Somalia and South Africa are among the top 10 countries in the world with the highest number of air pollution-related deaths. In total, the phenomenon has been killing 9 million people each year across the planet since 2015. According to the British scientific journal The Lancet, which published the results of the study, this is an increase of 7% compared to the previous decade.

“This puts pollution on a par with smoking in terms of deaths. Covid-19, by comparison, has killed about 6.7 million people worldwide since the start of the pandemic,” says the report, called “Global Health” and based on data from the University of Washington.

While industrial processes (toxic chemicals, fumes) and urbanisation have usually been blamed, contaminated water and soil have rapidly increased pollution levels on the continent, with economic losses estimated at $4.6 trillion annually. Yet some countries, such as Ethiopia and Nigeria, have cut pollution-related deaths by two-thirds between 2000 and 2019 thanks to a number of government programmes, the report says.

Breaking the deadlock

While 51% of Uganda’s 600 tonnes of annual waste ends up in the environment, according to the International Union for Conservation of Nature (IUCN), the East African country has developed air quality regulations and standards, including for emissions from vehicles and industries.

In Morocco, where fossil fuels, notably coal, oil and gas, still account for more than 63% of the energy mix, according to the Moroccan National Office of Electricity and Drinking Water (ONEE), the authorities are focusing on the energy transition for climate change resilience. Togo has also developed major renewable energy projects in recent years with a view to diversifying its electricity mix and pursuing the objective of carbon neutrality.

AFRICA: The continent tops a global ranking on pollution levels | Afrik 21
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