Exposure to air pollution affects fetal development, new study finds

Diabetes, obesity, hypertension… Exposure to three major air pollutants is associated with changes that can “alter fetal development”, found researchers from Inserm and the University of Grenoble Alpes, who studied the effects of air pollution on the placenta. According to a study published in The Lancet Planetary Health, these modifications may have long-term effects on metabolism, affecting boys and girls differently.

The harmful effects of air pollution on the fetus have already become the subject of research, which has identified the risk of a number of cardiometabolic and respiratory pathologies. But this new research aims to specifically understand what “molecular mechanisms are at work,” Inserm explains in a press release.

Neonatal diabetes and obesity

So the team looked at the placenta, which plays a “key role in fetal development” and is “particularly vulnerable to many chemicals.” With a group of nearly 1,500 pregnant women, she studied exposure to three air pollutants: nitrogen dioxide and fine particles PM2.5 and PM10.

She found a “significant impact” of this exposure associated with “epigenetic modifications,” in other words, changes in gene expression, but no modification of the DNA sequence. These changes “are likely to alter fetal development, particularly at the metabolic, immune and neurological levels,” the press release explains.

A third of these modifications directly affected “indicators of child development,” such as birth weight and height, head circumference, or even length of pregnancy. Placental modifications also affected genes involved in the development of the nervous system, immune system, and metabolism, including genes involved in neonatal diabetes or obesity.

“Different changes depending on gender”

The study also notes that while these epigenetic modifications have been observed in both sexes, the effects differ in girls and boys. To begin with, the placenta is vulnerable to changes in gene expression during more than one period of pregnancy: the first trimester in boys and the third trimester in girls.

“These differential effects may contribute to different changes in the development and course of pregnancy depending on the sex of the unborn child,” explains Inserm researcher Johanna Lepel, who led the team, as quoted in the report.

In boys, the research team identified effects on genes involved “critically in neurodevelopment and intelligence,” the paper notes. Enough to “support a growing body of research” that establishes a link between air pollution and “neurodevelopmental damage and/or cognitive decline” in fetuses, “with greater vulnerability in male children,” explains Lucille Broseus, first author of the study, also quoted in the press release.

As for girls, the detected epigenetic modifications may be associated “with developmental defects that may increase the risk of developing chronic metabolic diseases (…) later in life,” such as hypertension, diabetes or obesity, among others.

The mother may also be at increased risk of miscarriage or preeclampsia, a condition that causes increased blood pressure and protein in the urine. It is responsible for a third of very premature births in France and can lead to the death of the mother and/or her baby if left untreated.

In short, changes caused by air pollution leading to “dysregulation of fetal growth” “may be responsible for long-term changes in metabolism,” the press release summarizes. This observation will be strengthened by future studies, which could focus on “populations from other geographical regions and with different genetic profiles,” Joanna Lepel suggests. She also calls for research into “whether these changes persist after birth and how they may impact development in childhood.”