Aerial view of pollution being emitted from steel factories in Hancheng, Shaanxi, China
How deadly is air pollution?
01:07 - Source: CNN
CNN  — 

New evidence has been found that air pollution can breach a mother’s placenta and potentially reach fetuses in the womb, raising the possibility of future health problems.

Researchers found that when pregnant women breathe in black carbon pollution – created by the combustion of fossil fuels, such as in diesel-powered cars or the burning of coal – harmful particles can make their way from the lungs to the placenta and may reach fetuses directly.

Dirty air has previously been linked to increased miscarriages, premature births and low birth weights among infants, as a result of the effects of pollution on the mother.

However, the placenta – an organ that attaches itself to the womb during pregnancy, allowing oxygen and nutrients to pass from the mother’s blood supply to the fetus through the umbilical cord – was previously thought to be an “impenetrable barrier.”

A study last year was the first to suggest this wasn’t the case, after pollutants were found in the placentas of five pregnant women in the United Kingdom.

New research by scientists at Hasselt University and published Tuesday in the Nature Communications journal examined 25 non-smoking women who were giving birth in the Belgian city of Hasselt. Immediately after birth, the researchers collected the women’s placentas to study the side facing toward the fetus – where they found black carbon had accumulated.

The more black carbon the women were exposed to during pregnancy, the more black carbon was found in the placenta.

Black carbon particles come from a range of sources as well as cars and power plants – biomass and coal stoves in households, kerosine lamps, and open burning of farmland for agriculture.

The study cautions that more research is needed to show whether once inside the placenta, the particles can travel to the fetus directly, but the results prove that placentas do in fact allow through particles like black carbon, providing “compelling evidence” for this theory.

It’s the latest step in research into the link between pollution and birth – a 2017 report also found that exhaust fumes and soot from road traffic in London could be causing low birth weights in babies. The 2018 study, also conducted in London, found similar results to the Hasselt study – but the particle composition hadn’t been identified, and researchers could only speculate the pollution particles were carbon.