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First evidence that soot from polluted air may be reaching placenta

Evidence of tiny particles of carbon, typically created by burning fossil fuels, has been found in placentas for the first time, in early research involving a small number of people, presented today by researchers from Queen Mary University of London.

16 September 2018


Previous research has indicated links between pregnant mothers’ exposure to air pollution and premature birth, low birth weight, infant mortality and childhood respiratory problems.

The study, presented at the European Respiratory Society International Congress and funded by Barts Charity, adds to existing evidence on the dangers of pollution for unborn babies and suggests that when pregnant women breathe polluted air, sooty particles are able to reach the placenta via the bloodstream.

The work was presented by Dr Norrice Liu, a paediatrician and clinical research fellow, and Dr Lisa Miyashita, a post-doctoral researcher, both members of Professor Jonathan Grigg’s research group at Queen Mary’s Blizard Institute.

Air pollution affecting foetal development

Dr Miyashita said: “We’ve known for a while that air pollution affects foetal development and can continue to affect babies after birth and throughout their lives.

“We were interested to see if these effects could be due to pollution particles moving from the mother’s lungs to the placenta. Until now, there has been very little evidence that inhaled particles get into the blood from the lung.”

The researchers worked with five pregnant women who were all living in London and due to have planned caesarean section deliveries at the Royal London Hospital. They were all non-smokers with an uncomplicated pregnancy and each one gave birth to a healthy baby. The women all gave permission for researchers to study their placentas after delivery.

The team was interested in particular cells called placental macrophages. Macrophages exist in many different parts in the body. They are part of the body’s immune system and work by engulfing harmful particles, such as bacteria and pollution particles. In the placenta they also help to protect the foetus.

First evidence that inhaled pollution particles move to the placenta

The team studied a total of 3,500 placental macrophage cells from the five placentas and examined them under a high-powered microscope. They found 60 cells that between them contained 72 small black areas that researchers believe were carbon particles.

They went on to study the placental macrophages from two placentas in greater details using an electron microscope and again found material that they believe was made up of tiny carbon particles.

Dr Liu added: “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 foetus, 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 foetus.”

Professor Mina Gaga, President of the European Respiratory Society who was not involved in the study, said: “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.

“We need stricter policies for cleaner air to reduce the impact of pollution on health worldwide because we are already seeing a new population of young adults with health issues.”

More information

  • Research: Abstract no: PA360, “Late Breaking Abstract - Do inhaled carbonaceous particles translocate from the lung to the placenta?”, Norrice Liu et al; Occupational and environmental lung diseases: asthma and the airways, 08:30 hrs CEST, Sunday 16 September, Paris Expo Porte de Versailles.
  • Find out more about our postgraduate courses in Public Health at the Blizard Institute, Queen Mary University of London.

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For media information, contact:

Joel Winston
Public Relations Manager
Queen Mary University of London
email: j.winston@qmul.ac.uk