Air pollution can cross the placenta, reach the fetus, in human pregnancies

Particles of black carbon in the air, aka soot, can cross the placenta and reach the fetus in human pregnancies, a new study published in the journal Nature Communications reveals.

The new research is the first of its kind to offer direct evidence that particles from the air can reach the part of the placenta that feeds the developing fetus.

As the authors explain:

Particle transfer across the placenta has been suggested but to date, no direct evidence in real-life, human context exists. Here we report the presence of black carbon (BC) particles as part of combustion-derived particulate matter in human placentae using white-light generation under femtosecond pulsed illumination. BC is identified in all screened placentae, with an average (SD) particle count of 0.95 × 10⁴ (0.66 × 10⁴) and 2.09 × 10⁴ (0.9 × 10⁴) particles per mm³ for low and high exposed mothers, respectively. Furthermore, the placental BC load is positively associated with mothers’ residential BC exposure during pregnancy (0.63–2.42 µg per m³). Our finding that BC particles accumulate on the fetal side of the placenta suggests that ambient particulates could be transported towards the fetus and represents a potential mechanism explaining the detrimental health effects of pollution from early life onwards

The research was conducted by scientists at Hasselt University in Belgium. Scientists studied placentas that were donated by mothers. All placentas that were a part of the study were donated within 10 minutes of either a pre- or full-term birth. Previously it was believed that the placental barrier created a sterile environment for the fetus.

Researchers believe that when women breathed in the black carbon it traveled into the mother’s lungs and then to the placenta.

 “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”, authors of the study concluded.

The study also found that the more black carbon a woman was exposed to during her pregnancy, the more black carbon was found on the placenta. Researchers suggest that pregnant women avoid busy roads, especially if cycling or walking.

“For an individual, it’s very difficult to escape from it – people have to breathe,” said Professor Tim Narwot, one of the lead authors on the study. “But in general this needs to be addressed at policy levels.”

Black carbon comes from sources such as diesel engines, power plants, charcoal grills, kerosene lamps, and the open burning of farmland.

This new development may be able to answer the question of how the risk so many birth issues, such as the risk of miscarriage, premature birth, and low birth weights, are higher among women and children that live in areas with heavier air pollution.

 “This is the most vulnerable period of life,” said Nawrot. “All the organ systems are in development. For the protection of future generations, we have to reduce exposure.”