A mounting number of studies have recently linked poor air quality to a host of nasty health problems, culminating in millions of premature deaths each year. Now, yet another study has found that air pollution could have a horrific effect on unborn children.

The study, published last month in journal Fertility and Sterility, has found that high levels of air pollution were associated with a 16 percent higher risk of miscarriage in the US. Most shocking of all, the team discovered that miscarriages could be specifically linked to weeks where air quality was especially poor.

Researchers from the University of Utah analyzed the records of more than 1,300 women living in Wasatch Front, a populous chain of urban areas in Utah, who experienced miscarriages between 2007 and 2015. After accounting for other risk factors, such as maternal age, they then compared the rates of miscarriage with concentrations of three common air pollutants: small particulate matter (PM 2.5), nitrogen dioxide (NO₂), and ozone.

Certain periods, especially during the winter, experience high levels of air quality due to pollutants being trapped in pockets of cold air closer to the ground. The researchers found that there was a slight (but notable) increased risk of miscarriages in a 3- to 7-day window after there was a spike in nitrogen dioxide levels. The most prominent sources of nitrogen dioxide are motor vehicles' internal combustion engines burning fossil fuels.

Although the research was limited to a relatively small geographic area, the researchers argue their findings point to a widespread problem that many city-dwellers could face.

"While we live in a pretty unique geographic area, the problems we face when it comes to air pollution are not unique," senior author Matthew Fuller said in a statement. "As the planet warms and population booms, air pollution is going to become a bigger problem not only in the developing world but across the United States."

“The results of this study are upsetting, and we need to work together as a society to find constructive solutions,” he added.

This is not the first study looking at air pollution and miscarriages to reach this conclusion. A study from 2017 found that couples with higher exposure to ozone were 12 percent more likely to experience an early pregnancy loss, while those exposed to small particulate matter were 13 percent more likely.

Speaking to The Guardian, Fuller added: “If you compare that increase in risk to other studies on environmental effects on the foetus, it’s akin to tobacco smoke in first-trimester pregnancy loss.”