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Residential exposure to ambient air pollutants is linked to an elevated risk of SARS-CoV-2 infection, an observational study of young adults in Stockholm, Sweden shows. The study was conducted by researchers from Karolinska Institutet and is published in JAMA Network Open.

Since pollutants in outdoor air can increase the risk of respiratory infections such as influenza and SARS, the COVID-19 pandemic aroused fears that they could also contribute to the risk of SARS-CoV-2 infection. Studies have also shown that areas of poor air quality have more cases of COVID-19.

Researchers at Karolinska Institutet have now studied this more closely by examining the link between estimated exposure to air pollutants at home addresses and positive PCR tests for SARS-CoV-2 in young adults in Stockholm, Sweden.

The results show that exposure to certain traffic-related air pollutants is associated with a greater likelihood of testing positive.

“Our results add to the growing body of evidence that air pollution has a part to play in COVID-19 and support the potential benefit of improving air quality,” says Olena Gruzieva, associate professor at the Institute of Environmental Medicine at Karolinska Institutet and one of the study’s last authors.

The study draws on the population-based BAMSE project, which has regularly followed over 4,000 participants in Stockholm from birth. By linking these data to the national communicable disease registry (SmiNet), the researchers identified 425 individuals who had tested positive for SARS-CoV-2 (PCR test) between May 2020 and the end of March 2021. The average age of the participants was 26, and 54 per cent were women.

Daily outdoor concentrations of different air pollutants at the participants’ home addresses were estimated using dispersion models. The pollutants were particles with a diameter less than 10 micrometers (PM10) and 2.5 micrometers (PM2.5), black carbon and nitrogen oxides.

The researchers studied the associations between infection and exposure to air pollutants in the days before the positive PCR test, on the day of the test and on later control days. Each participant served as his or her own control on these different occasions.

The results show associations between infection risk and exposure to PM10 and PM2.5 two days before a positive test and exposure to black carbon one day before. They found no link between the risk of infection and nitrogen oxides.

The increase in risk was of an order of magnitude around seven per cent per particle exposure increase equivalent to the interquartile range, i.e. between the first quartile (25%) and the third quartile (75%) of the estimated particle concentrations.

“Seven per cent doesn’t sound much, but given that everyone is more or less exposed to air pollutants, the association may be of great significance to public health,” says Erik Melén, professor of paediatrics at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, BAMSE project leader and the study’s joint last author.

The observed association was not influenced by gender, smoking, overweight or asthma.

The researchers note that the results might be affected by the willingness to take a PCR test and the fact that many of the young adults were asymptomatic or had only mild symptoms following infection. The study can also not rule out the possibility that time-varying confounding factors also influenced the results.

The researchers are now examining the link between air pollutants and post-COVID symptoms in young adults.

The first author of the paper is Zhebin Yu, postdoctoral researcher in Olena Gruzieva’s group. The study was financed by Forte, the Swedish Research Council, the Swedish Heart-Lung Foundation and Region Stockholm. The authors have reported no conflicts of interest.

Air pollution linked to higher risk of COVID-19 in young adults — ScienceDaily

How do the lungs develop after taking their first breaths outside the womb? What cellular events and changes early in life give rise to lung malfunction and disease? To help answer these questions, scientists have constructed the first single-cell atlas of postnatal lung development in humans and mice.

The research could help provide a more detailed understanding—at the level of individual cells—of which genetic and epigenetic factors affect lung health across the human lifespan, starting from birth. 

The work, recently published in Cell Genomics, was led by a team of researchers at the University of California San Diego and the University of North Carolina at Chapel Hill.

By analyzing lung tissue samples from newborn and young humans and mice, the researchers were able to gain insights on how certain cell types in the lung originate and change during childhood.

“These are unique samples that we’ve collected information on during a time in lung development that has not been well studied,” said first author Thu Elizabeth Duong, a physician-scientist in pediatric respiratory medicine at UC San Diego School of Medicine and pulmonologist at Rady Children’s Hospital-San Diego. “What’s exciting is being able to see, at single-cell resolution, what the lung cells are doing at this stage in development.”

The goal is to build a so-called “reference map” of the human lungs. Such a map would serve as a foundation to understand the cellular differences between healthy and diseased lungs. This work represents a small step toward building a reference for the pediatric population.

“Your respiratory health gets shaped by what happens during your early years of life. So when things go wrong, we can refer back to these early years to identify potential causes of disease,” said Duong.

“In cases of lung abnormality or disease, we can zoom in and examine what specific types of cells are different from their counterparts in the healthy references and what are the molecular pathways underlying these changes,” said Kun Zhang, professor and chair of bioengineering at UC San Diego who is a senior author of the study. “Diagnosis and treatment could then be developed based on differences from the reference map.”

The lungs are an important barrier in the body. They let in and maintain the balance of vital substances such as oxygen, while removing wastes such as carbon dioxide. And they filter the air that we breathe. The researchers hope that their findings here will lay the groundwork for more in-depth studies of how environmental factors such as exposure to air pollution and smoking influence lung health and disease throughout different stages of life.

To construct their map, the researchers analyzed post-mortem human lung tissues that were collected at different time points, starting from day one and up to 9 years after birth. The researchers also collected lung tissue samples from mice at matching time points between one day and nearly one month after birth.

The researchers used next-generation single-cell sequencing technologies developed in Zhang’s lab to analyze individual nuclei of more than 80,000 human and mouse lung cells combined.

With this analysis, the researchers could start to map developmental pathways for different lung cell types including alveolar epithelial type 1 cells. These cells are vital for the exchange of oxygen and carbon dioxide gases. The researchers gained clues as to how alveolar type 1 cells communicate with other cells such as myofibroblasts, and how this communication could play a role in alveolar cell development.

The study also revealed a unique population of fibroblast cells in the human lung that was not observed in mice. These fibroblasts are cells in connective tissue that play a role in how the lungs stretch. The researchers also found cell states in the human lung that are present in early life at birth but disappear by 9 years of age.

“These data are helping us piece together how key cell types in the lung come into existence,” said Duong. “We hope this will serve as a valuable resource for lung researchers moving forward.”

Paper: “A single-cell regulatory map of postnatal lung alveologenesis in humans and mice.” Co-authors include Yan Wu, Brandon Chin Sos, Weixiu Dong and Siddharth Limaye, UC San Diego; Lauraine H. Rivier, Greg Myers and James S. Hagood, University of North Carolina at Chapel Hill.

Researchers map lung development after birth | EurekAlert!