Black carbon particles were discovered on the foetus-facing side of placentas, according to a study published in Nature Communications.

"Our study provides compelling evidence for the presence of black carbon particles originating from air pollution in human placenta," the authors said.

The study found the concentration of particles in placentas was highest for women most-exposed to pollution in their day-to-day lives.

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Researchers from Belgium's Hasselt University used a novel scanning technique to search for soot-like black carbon in the placentas of 28 new mothers. They were hoping to shed light on how exposure to the tiny particles lead to premature births and low birth weight.

Scientists led by Tim Nawrot said the results showed that "black carbon particles are able to translocate from the mothers' lungs to the placenta." There was no evidence of pollution particles in the fetus itself.

Next steps

However, a leading placenta expert who wasn't involved with the new research cautioned that the results are not proof the soot actually crossed the placenta to reach the fetus — or that it's responsible for any ill effects.

Still, "just finding it at the placenta is important," Dr. Yoel Sadovsky of the University of Pittsburgh Medical Center told the Associated Press. "The next question would be how much of these black carbon particles need to be there to cause damage."

The placenta nourishes a developing fetus and shields it from damaging substances in the mother's bloodstream.

This article was originally published on DW.

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