Tiny particles of carbon associated with air pollution can find their way into the placenta of pregnant women, a new paper reports. The findings cast light on the danger air pollution poses on developing fetuses.
Even unborn babies suffer from the poor quality of our air, new research shows. Previous research has linked complications such as premature birth, low birth weight, infant mortality, and childhood respiratory problems to a pregnant woman's exposure to air pollution. The present paper adds to that body of evidence, explaining that when pregnant women breathe polluted air, particles of soot are able to travel through the bloodstream to the placenta.
The smell of soot in the morning
The findings were presented by Dr. Norrice Liu, a pediatrician and clinical research fellow, and Dr. Lisa Miyashita, a post-doctoral researcher Sunday at the European Respiratory Society International Congress in Paris.
"We've known for a while that air pollution affects foetal development and can continue to affect babies after birth and throughout their lives," Dr. Miyashita explained.
"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 team worked with five pregnant women, all of whom were living in London. The five were all non-smokers, pregnant with uncomplicated pregnancies, and were due to have planned cesarean section deliveries at the Royal London Hospital.
After they gave birth, the team retrieved their placentas for study. The researchers were particularly interested in cells known as placental macrophages. Some of their previous research involved identifying and measuring soot particles in the human airway by investigating these cells.
Macrophages of all walks of life permeate the body. They're an integral part of the immune system and work by gobbling up foreign, harmful particles such as bacteria or soot, and then attacking them chemically -- i.e. 'digesting' them. In the placenta, they're tasked with keeping the fetus secure.
The team looked at roughly 3,500 placental macrophage cells retrieved from the five participants. Using a high-powered microscope, they investigated the cells for signs of soot. Some 60 cells contained these particles, the paper reports, totaling roughly 72 black areas. On average, each placenta contained around five square micrometers of this black substance.
Subsequent experiments with an electron microscope showed this black substance was made up of tiny carbon particles -- soot.
"We thought that looking at macrophages in other organs might provide direct evidence that inhaled particles move out of the lungs to other parts of the body," Dr Liu explains. "We were not sure if we were going to find any particles and if we did find them, we were only expecting to find a small number of placental macrophages that contain these sooty particles."
"This is because most of them should be engulfed by macrophages within the airways, particularly the bigger particles, and only a minority of small sized particles would move into the circulation.
The results form the first solid evidence of soot particles passing from the lungs into the circulatory system and, from there, to the placenta. As of now, the team cannot say for sure whether the particles can also make their way into the fetus, but note that "this is indeed possible" given the current findings.
"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," Dr Liu cautions, however.
The results support previous findings that women living in polluted cities are more prone to pregnancy issues. Furthermore, they suggest that such issues -- especially low birth weight -- can still happen at pollution levels that are lower than the EU's recommended annual limit.
The study "Do inhaled carbonaceous particles translocate from the lung to the placenta?" has been presented at the European Respiratory Society International Congress in Paris on September 16th. The work is a non-peer reviewed observational study.