It’s common sense that inhaling pollutants, like exhaust fumes and wood smoke, isn’t a great thing for our health: just spend half an hour outside when wildfire smoke is choking up the sky and experience the inevitable coughing fits and sore throat that come with it. But the health effects of air pollution go beyond what we experience in the moment. According to a new study, certain pollutants could affect the long-term health and reproductive systems of fetuses while they’re still in the womb.
The study, published today in Environmental Health Perspectives, looked at a particular marker of infant reproductive development called anogenital distance, aka the length of the distance between genitals and anus. Previous studies have shown that shorter anogenital distance among adults might be related to hormone levels, semen quality and fertility in men, while both longer and shorter anogenital distance is associated with reproductive disorders in women.
Anogenital distance is also used as a marker in animal studies to find the developmental toxicity of pollutants. The researchers in the new study wanted to find out if the same pollutant relationship existed in humans, with potentially serious implications for reproductive health.
The researchers in this study used anogenital distance data from an ongoing study, The Infant Developmental and Environment Study, which involves pregnant women and their children in four major US cities. They used anogenital distance measured at birth and, for boys, at one year, and compared it to levels of pollutants measured in areas where the study’s participants lived during pregnancy.
Looking at both of these measures, the researchers found a clear connection. They saw that higher pollution levels during certain key periods of pregnancy correlated to shorter anogenital distance at birth. Specifically, higher exposure to pollutants at the end of the first trimester, when the male fetus usually receives a higher amount of hormones, was linked to a shorter anogenital length at birth. Higher pollutant exposure during the period known as “mini-puberty,” an early-infancy period when hormone production is also high, was also linked to shorter anogenital distance at age one for male babies.
So which pollutants were the issue? The researchers specifically looked at levels of nitrogen dioxide and fine particulate matter, aka PM2.5. This refers to particle pollution that measures 2.5 micrometers or smaller, released by burning wood and/or fossil fuels like gasoline, oil, and diesel.
PM2.5 is a kind of “trojan horse,” as it can carry endocrine disruptors like cadmium and lead, said Emily Barrett, PhD, lead author of the study and professor of environmental and occupational health, in a press release from Rutgers. “When these disruptors interfere with the body’s hormones, the result could be lifelong impacts on our health, from cancer risks to impaired ability to conceive a child,” she explained.
The conclusion, researchers wrote in the study, was that exposure to these pollutants “during critical pre- and postnatal windows may disrupt reproductive development,” though they noted that more research is needed to confirm the results and explain exactly how they occurred.
“These findings suggest air pollution may interfere with normal hormone activity during critical periods of prenatal and early infant development, and we suspect that disruption may have long-term consequences for reproductive health,” said Dr. Barrett.
The discovery is yet more proof that air pollution is doing damage to our health far beyond coughing and sore throats, and another reason to look towards cleaner fuel sources in the future beyond oil and gas.
Before you go, check out these must-have items to get you through pregnancy and bed rest: