The air we breathe is increasingly toxic. The World Health Organization (WHO) estimates that 99 percent of the global population inhales dirty air that exceeds their guideline limits, air that kills about 6.7 million people each year. For perspective, the WHO estimates that there were between 1.8 and 3 million deaths from COVID-19 in the year 2020. Although with the pandemic, official figures are likely an extreme undercount, the fact remains that air pollution is a prevalent, mostly invisible killer.
The problem is only getting worse. In the American Lung Association's 2022 State of the Air report, they found that "nearly 9 million more [American] people were impacted by daily spikes in deadly particle pollution than reported last year." Alarmingly, air pollution's effects are not confined to the breathing, as a growing body of research suggests that air pollution worming its way into the bodies of fetuses and unborn babies vis-a-vis their mothers' lungs.
The level of estimated pollution exposure strongly correlated with the level of black carbon found in the placenta samples and in cord blood, which accumulates in the umbilical cord.
Indeed, even before drawing their first breath, babies are being exposed to air pollution. It was first discovered in 2018 that air pollution particles can make their way into the placenta, an important organ that forms a protective interface in the uterus during pregnancy. But new research in The Lancet's Planetary Health journal shows for the first time that these pollutants can enter the fetus, exposing unborn infants to toxins before they even breathe for the first time.
To determine this, scientists at the University of Aberdeen in the U.K., and Hasselt University in Belgium conducted two studies. In the first, 60 mothers who had just given birth at East-Limburg Hospital in Belgium voluntarily donated their placentas and blood samples, which were analyzed at Hasselt University. Nearly 90 percent of the newborns were white Europeans, so it may not give a picture of what exposure is like in places like, say, New Delhi, India, one of the most polluted regions on Earth.
The researchers analyzed the samples for black carbon, a sooty byproduct of burning fossil fuels and wildfires that long-term exposure has been associated with cardiovascular and respiratory diseases, birth defects and early death. Then, using the volunteers' addresses and public air pollution monitoring data using satellites, they calculated the average level of exposure to toxic air. The level of estimated pollution exposure strongly correlated with the level of black carbon found in the placenta samples and in cord blood, which accumulates in the umbilical cord.
The second study was conducted in Scotland using liver, lung and brain tissue of fetuses. These samples were blasted with specialized white light lasers for just one quadrillionth of a second, but this was enough to illuminate thousands of tiny black carbon molecules.
Together, these results are pretty damning evidence that air pollutants can spread to a fetus and accumulate in worrying amounts that could lead to severe health problems down the road.
"What we have shown for the first time is that black carbon air pollution nanoparticles not only get into the first and second trimester placenta, but then also find their way into the organs of the developing fetus, including the liver and lungs," Paul Fowler, a professor at the University of Aberdeen and one of the study authors, said in a statement. "What is even more worrying is that these black carbon particles also get into the developing human brain. This means that it is possible for these nanoparticles to directly interact with control systems within human fetal organs and cells."
The researchers are quite sure the fetal samples weren't contaminated by the ambient air in the lab because the black carbon was deeply embedded in the organ tissue. The mothers in both studies were also screened against smoking tobacco, so cigarette use didn't skew the results.
"These findings are especially concerning because this window of exposure is key to organ development," the authors wrote. "It is the life stage during which susceptibility for many diseases later in life is programmed."
However, researchers still need to determine what mechanism of action black carbon and other pollutants actually cause disease. The presence of toxins alone isn't enough evidence, although it is a strong indicator. "Nevertheless," the authors conclude, "the exact impact of direct fetal black carbon exposure requires clarification and must be further elucidated in follow-up studies."
"We know that exposure to air pollution during pregnancy and infancy has been linked with still birth, preterm birth, low weight babies and disturbed brain development, with consequences persisting throughout life," Professor Tim Nawrot, a professor of environmental epidemiology at Hasselt University said in the same release. "We show in this study that the number of black carbon particles that get into the mother are passed on proportionally to the placenta and into the baby. This means that air quality regulation should recognize this transfer during gestation and act to protect the most susceptible stages of human development."
There are other ways air pollution may damage an infant's health. A study published in August in the journal Gut Microbes examined 103 Latino babies in Southern California and found that air pollution could influence the gut microbiome, the first time this was shown in infants. Some of these changes have "previously been linked with adverse health outcomes such as systemic inflammation, gastroenteritis, multiple sclerosis, and mental health disorders," the authors reported.
"Overall, we saw that ambient air pollution exposure was associated with a more inflammatory gut-microbial profile, which may contribute to a whole host of future adverse health outcomes," senior author Tanya Alderete, assistant professor of Integrative Physiology at University of Colorado, Boulder, said in a statement.
Alderete recommended that mothers avoid walking near high-traffic areas, investing in an air filtration system, opening the windows and breastfeeding as long as possible.
"Breast milk is a fantastic way to develop a healthy microbiome and may help offset some of the adverse effects from environmental exposures," Alderete said.
However, as Salon previously reported, microplastics were recently found in human breast milk for the first time. Breastfeeding is still recommended, of course, but it underscores the ubiquity of pollutants when it comes to reproductive and infant health. It is critical to address this growing issue, as the future health of our children is literally at stake.
