Early research from the UK has provided the first evidence that soot from polluted air is reaching the placenta.
The findings, presented at the European Respiratory Society International Congress 2018 in Paris, reinforce the Society’s call for improved air quality legislation in its 10 Principles for Lung Health document.
Paediatrician and clinical research fellow Dr Norrice Liu said epidemiological research has previously linked maternal exposure to air pollution with foetal and infant outcomes including premature birth, low birth weight, infant mortality and childhood respiratory problems.
Yet it was generally accepted that macrophages in the lung could remove most particulate matter before it entered the circulation.
Instead, the study conducted at the London Hospital and the Queen Mary University of London found direct evidence that particulate matter was reaching the placenta via the bloodstream.
The pilot study harvested placental macrophages from five women – non-smokers with uncomplicated pregnancies and healthy singleton babies delivered via elective caesarian sections.
Using high-powered light microscopy, the researchers found dense, black particles that they believed to be phagocytosed carbonaceous particulate matter in 60 of the 3,500 placental macrophages.
Closer examination of two placentas using electron microscopy also confirmed black inclusions within phagolysosomes, likely to be inhaled black carbon and similar to sooty particles seen in lungs.
Dr Liu told the meeting that each placenta contained on average around five square micrometres of the particular matter.
“Our results provide the first evidence that inhaled pollution particles can move from the lungs into the circulation and then to the placenta.”
“We do not know whether the particles we found could also move across into the fetus, but our evidence suggests that this is indeed possible. We also know that the particles do not need to get into the baby’s body to have an adverse effect, because if they have an effect on the placenta, this will have a direct impact on the fetus.”
She said the research should help improve awareness of the danger of air pollution particularly in cities like London where pollution thresholds were breached regularly.
Commenting on the study, ERS president Professor Mina Gaga said there was a need for stricter policies to reduce the impact of pollution on health worldwide.
“This new research suggests a possible mechanism of how babies are affected by pollution while being theoretically protected in the womb. This should raise awareness amongst clinicians and the public regarding the harmful effects of air pollution in pregnant women.”