Air Pollution Can Reach The Fetal Side Of Placentas In The Womb

Startling new research has just found that air pollution particles in the fetal side of placentas in the womb. This is the black carbon that is breathed in by mothers, caused by vehicular emissions and fossil fuel burning that causes a major part of the atmospheric pollution experienced in cities and other urban centers.

According to the researchers, this is the first study to “show that air pollution particles can reach the fetal side of the placenta,” to quote author Hannelore Bove, postdoctoral researcher, Centre for Environmental Sciences and Biomedical Research Institute, Hasselt University, Belgium, from an interview in WebMd.

This research looked at high-resolution images from over 25 placentas taken from women who were not smokers and had just delivered babies in Belgium. Of the placentas studied, five were those taken from premature births, while the rest were from full-term babies. The placentas were retrieved ten minutes after delivery. All the placentas had black carbon nanoparticles on the fetal side of the placenta. The finding of air pollution and black carbon particles on the fetal side of the placentas is a major direct correlation of how unborn children are exposed to pollution while still in the womb. This finding is evidence that even children in the womb can no longer be said to be protected from pollution while in the womb.

This is the first research that has actually shown that the placental barrier is not as impenetrable as hitherto thought. The research found thousands of microparticles of carbon per cubic millimeter of the placental tissue.

To quote the corresponding author of the study, Tim Nawrot, Professor of environmental epidemiology at Hasselt University from an interview to The Guardian, "The placenta's principal function is to deliver nutrition and oxygen to the fetus. But to some extent, it also forms a barrier against toxicants."

Bove adds, “Decades ago it was thought that nothing can cross the placenta. And that the fetus is completely safe inside the womb."

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Nonetheless, previous research has proved the link between exposure to high levels of pollution, the increased risk of miscarriages, premature births, and low birth weights. This new research suggests that these particles might well be the cause. In utero damage to fetuses could manifest in forms that remain over a lifetime. To quote Prof Tim Nawrot, “This is the most vulnerable period of life. All the organ systems are in development. For the protection of future generations, we have to reduce exposure.”

This latest research published in Nature Communications used a laser technique to pinpoint the pollution particles of black carbon. Their findings showed that these nanoparticles on the fetal side of the placenta were consonant with the levels of pollution the mothers experienced. They found an average of 20,000 nanoparticles per cubic millimeter in the placentas from mothers living near roads which had high traffic and consequently high pollution. Those living further away from these roads had an average of 10,000 nanoparticles per cubic millimeter. The research also examined placentas from miscarriages and found these particles present even in fetuses as small as 12 weeks. The researchers will now study whether these particles have caused any DNA damage in these fetuses.

Interestingly, the town in Belgium where the study was conducted has particle pollution levels well below the EU limit, although above the WHO limit.

In our cities though, pollution levels have consistently been going off the charts. In fact, in a recent study conducted by the environment NGO Greenpeace, Delhi was named as the most polluted capital in the world for the year 2018.

There are efforts being taken to reduce the air pollution levels but these will take time to be really effective and for us to see discernable change. Over 122 cities in India are working on plans to implement clean air policies and measures under the National Clean Air Program (NCAP), targeting a reduction in PM10 and PM2.5 (air pollutants) levels across the country by at least 20-30 percent by 2024.

Given the current levels of pollution, citizens in urban India live with on a daily basis, this news is worrying, especially for expectant mothers.

These findings have shaken up the traditional belief that the womb was a barrier to the toxic environment that we often live in. That pollution reaches the fetus through the womb, at a critical phase in human fetal development is something that should worry us because we are yet to know the repercussions of this on the child and the adult. Some chronic and lifelong diseases may originate in the womb itself.

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To quote Bove, "Black carbon particles are thought to be especially toxic, since they can absorb toxic compounds like, for example, heavy metals and benzene.” These are cancer-causing agents and they can potentially mix with the nutrients and the oxygen taken in by the growing fetus.

Doctors are concerned about these findings. Says Dr. Munjaal V. Kapadia, Gynecologist, Obstetrician and Director at Namaha Superspecialty Hospital for Women, “Although the clinical sequelae of these toxins on the fetus have been established, the very fact that such particles have been proven to cross the placental barrier is worrying. More studies need to be done to investigate the lingering effect of these toxins during early childhood and ultimately adulthood.”

Says Dr. Megha Consul, Principal Consultant and Neonatologist, Max Speciality Hospital, Gurgaon, “Fetal development is extremely critical and relevant as the etiology of diseases in adulthood may have a fetal origin. Many diseases have been attributed to adverse effects of in utero environmental exposures. Outdoor air pollution exposure is such a detrimental environmental factor.”

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She lists out the adverse effects of pollution on pregnancies. She says, “Combustion-related pollution is associated with lower birth weight, preterm birth, and intrauterine growth restriction. Various potential mechanisms have been proposed including both indirect (e.g., intrauterine inflammation) and/or direct (e.g., particle translocation). Secondly, studies have started to investigate effects on pregnancy-induced hypertension and spontaneous abortion, the latter possibly triggered by air pollution’s damage to DNA in sperm. Thirdly, studies have shown a clear association of preterm birth and low birth weight mostly with high levels of carbon monoxide and particulate matter during the first trimester and the final months before birth. Air pollution exposure during early pregnancy may interfere with placental development and subsequent oxygen and nutrient delivery to the fetus throughout pregnancy, while the last trimester is important for fetal weight gain. Increased risks of certain heart defects were found to be correlated to high levels of carbon monoxide and possibly ozone in the second month of pregnancy, presumably because this is the most important time period for fetal heart development.”

Fetal development is extremely critical and relevant as the etiology of diseases in adulthood may have a fetal origin. Many diseases have been attributed to adverse effects of in utero environmental exposures. - Dr Megha Consul

While most doctors do realise it is realistically not possible to expect pregnant women living in highly polluted areas to shift homes, there is definitely a possibility to minimise exposure to pollution. So what do expectant mothers living in cities and towns with high levels of pollution do? Given that measures to reduce pollution substantially are still a long way off, avoiding busy traffic areas as much as possible, installing air purifiers and wearing masks when outdoors could be the best options.

Dr. Consul says they should avoid heavily polluted areas and invest in air purifiers from conception itself to minimize its adverse effects on the developing fetus. Adds Dr. Kapadia, “ It is difficult to recommend any particular measures that may be of practical value to women. One can only suggest that they try their best to distance themselves from areas known to be heavily polluted. The use of face masks to wear in public or the use of home air purifiers needs further research and development. The only real hope, for future generations, is to curb our reliance on fossil fuel.”

We must bear in mind that research has yet to tell us how the presence of pollutants in the placenta affects the growing fetus in its development and in its lifetime, and it is always better to err on the side of caution given the high levels of pollution in our cities.

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