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First-ever link found between asthma in toddlers and prenatal exposure to air pollution

According to a new study, infants whose mothers have been exposed to greater amounts of small air pollution particles during pregnancy are more likely to develop asthma as toddlers.

In their preschool years, slightly more than 18% of the children born to these women acquired asthma, compared to 7% of children in the United States who were diagnosed with asthma by the Centers for Disease Control and Prevention.

The new study analyzed the effect of ultra-fine particles (UFPs), which are not controlled by governments. These are regarded to be considerably more harmful than the bigger particles that are examined on a regular basis, and have also been associated to asthma. Vehicles and wood stoves are also sources of UFPs, and each sugar cube-sized volume of urban air contains tens of thousands of particles. They are thought to pass through the lungs and into the bloodstream of the expecting female, producing harmful inflammation. They are also likely to penetrate the placenta and enter the circulation of the fetus.

UFPs have been related to other health effects, including as brain cancer, and researchers believe that showing these effects would encourage governments to properly assess and act to eliminate polluted air.

“One reason ultra-fine particulates are not routinely monitored is that there have been a number of unique challenges to measuring them accurately. Fortunately, recent methods have been developed to provide such exposure data which allowed us to conduct this study,” said lead author Rosalind Wright, MD, MPH, Horace W. Goldsmith Professor in Children’s Health Research, Professor of Environmental Medicine and Public Health and Co-director of the Institute for Exposomic Research at the Icahn School of Medicine at Mount Sinai.

There were 376 women and their children who participated in the research study, the majority of whom were Black or Latinx, who lived in the Boston metro region and were previously being monitored for their health. Mount Sinai researchers collaborated with a group of Tufts University scientists in the Boston region who had devised a method for providing reliable daily estimates of ultra-fine particle exposure that could be linked to the mothers’ and children’s residences.

Many of these mothers lived near major highways with high traffic density, which means they were exposed to more of these microscopic particles. The researchers followed up with the moms to see if their children had been diagnosed with asthma. The majority of asthma diagnoses in the children occurred after three years of age, and 18 percent of the children got asthma. Other variables considered by the researchers included the moms’ age and obesity. They also considered other contaminants in the air.

“These UFPs have independent effects,” Wright explained. The researchers discovered that the phase of gestation during which fetuses were most vulnerable to UFP exposure differed between male and female fetuses, potentially indicating that UFPs interfered with the hormonal system.

Fetuses are particularly sensitive to the oxidative stress that pollution particles induce in human tissues, according to Wright: “Fetal development is exquisitely sensitive to anything that throws the oxidation balance out of whack.”

“Our research is an important early step in building the evidence base that can lead to better monitoring of exposure to UFPs and ultimately to regulation,” said Prof Rosalind Wright, at the Icahn School of Medicine at Mount Sinai, New York, and who led the research. “Childhood asthma remains a global epidemic that is likely to grow with the anticipated rise in particulate air pollution exposures due to effects of climate change.”

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