Recently a new study shows that even unborn babies can be affected by air pollution that when pregnant women breathe polluted air, soot particles can travel from the lungs to the placenta through blood and are likely to affect infants.
   The study adds to a growing body of research that has found links between air pollution and complications such as premature birth, low birth weight, infant mortality, and childhood respiratory problems. The study involves five local pregnant women who were planning to have a caesarean section at Royal London hospital. They are all non-smokers and show no symptom of complications during pregnancy. After the baby was born, the researchers studied the macrophages in her placenta which is an important component of the human immune system.
   "We already know that air pollution affects the development of the fetus and the impact lasts for the whole process of growth after he or she is born." Dr Lisa Miyashita, one of the study participants, explained, "but we were interested to see if these effects could be due to contamination particles moving from the mother's lungs to the placenta. So far, few studies have shown that pollution particles inhaled by the human body get into the blood from the lungs.”
   The bacteria, viruses or foreign matter that invades human body, as well as the waste that human body produces, damage cell and necrotic tissues, all need to be digested and cleared by phagocytes. Therefore, phagocytes are  regarded as "guardians of human health". Phagocytes can be divided into large phagocytes and small phagocytes. Macrophages have different names in different tissues. They are called "pulmonary phagocytes" in the  lungs and "placental phagocytes" in the placenta.
   The researchers found 3,500 macrophages in five placentas, and when they looked at the cells using a high-power microscope, they found about 60 cells containing air pollution particles, a total of about 72 black areas, with an average of about five square microns of black material on each placenta. The researchers then used an electron microscope to look further at two of the placentas and confirmed that the black material was made of tiny carbon particles called soot. It is a solid evidence that soot particles enter the circulatory system from the lungs and thus the placenta.
   Researchers aren't sure whether smoke particles can enter the baby, but  based on the current findings, "this is very likely," Dr Liu said, "but we also know that these soot particles can affect fetus without entering his or her body, because if they have a side effect of the placenta, they will directly affect the fetus." However, at the moment, the report is an observational study that has not been peer-reviewed and the results  still need more experimental evidence.