In a small study published in Nature Communications on September 17, 2019, researchers at Belgium’s Hasselt University found the presence of black carbon (BC) particles as part of combustion-derived particulate matter in human placentas.
This is the first direct evidence that the particles can get into the part of the placenta that feeds the developing fetus, and goes a long way in explaining why air pollution is linked to an increased risk of miscarriage, premature birth, and low birth weights.
The amount of black carbon embedded in the fetal side of the placenta correlated with the estimated air pollution found near the expectant mother’s home, according to the study.
“This is the most vulnerable period of life. All the organ systems are in development. For the protection of future generations, we have to reduce exposure,” said study co-author Tim Nawrot at Hasselt University in Belgium, in an interview.
Scientific confirmation
Particle transfer across the placenta has been suggested – and a study presented at a conference in 2018 revealed that inhaled black carbon can enter the placenta through the mother’s bloodstream.
But the research failed to prove that the soot particles could move from the maternal placenta, made from the mother’s uterine tissue to the fetal placenta, made from the same tissue that forms the fetus. The new Belgium study provides the evidence.
The research team examined nearly 30 placenta samples from non-smoking women in the Belgian town of Hasselt. Each placental sample was exposed to ultrafast laser bursts, that in turn excited negatively charged particles within the tissue. The technique caused the tissues to radiate colored light — red for collagen, green for placental cells and white for black carbon.
The results were interesting – with an average of 9,500 soot particles per cubic millimeter (about the volume of a grain of salt) in the placentas of women who lived far from main roads and areas of high pollution.
However, women living in more polluted areas accumulated about 20,900 particles of black carbon per cubic millimeter on the fetal side of their placentas.
Air pollution has long been linked to a heightened risk of preterm birth, low birth weight, and miscarriage. However, this was quite often attributed to inflammation in the mother herself – primarily the uterus.
“There’s no doubt that air pollution harms a developing baby,” said Amy Kalkbrenner, an environmental epidemiologist at the University of Wisconsin-Milwaukee, who was not involved in the work, in an interview with Science News. “The new study suggests “air pollution itself is getting into the developing baby,” she said.
Writing in the journal, the scientists said: “Our results demonstrate that the human placental barrier is not impenetrable for particles. Further research will have to show whether the particles cross the placenta and reach the fetus” and if that “represents a potential mechanism explaining the detrimental health effects of pollution, from early life onwards.”
