Posted in | Pollution

Study Shows Air Pollution is Associated with Increased Risk of Miscarriage

Adverse health outcomes, ranging from pre-term birth to asthma, have been shown to be associated with air quality. Now, scientists at the University of Utah Health have discovered that women who live along the Wasatch Front—the most populous area in the state of Utah—had a greater risk (16%) of miscarriage after short-term exposures to increased air pollution. The results of the study have been reported in the journal Fertility and Sterility.

Pollution in the Salt Lake Valley. (Image credit: University of Utah Health)

Not being from Salt Lake originally, I noticed a pattern in the relation to air quality and pregnancy loss. I knew this was an understudied question so we decided to dig deeper.

Matthew Fuller, MD, Study Senior Author and Assistant Professor of Surgery, University of Utah Health.

Fuller joined Claire Leiser, a research analyst at the University of Utah (U of U), on a retrospective study that includes over 1300 women (38% Hispanic, 54% Caucasian, and other/missing 8%; average age 28 years). The females who participated in the study sought assistance at the U of U emergency department after a miscarriage (around 20-weeks gestation) from 2007 to 2015.

After an increased concentration of three common air pollutants—ozone, small particulate matter (PM 2.5), and nitrogen dioxide—the researchers assessed the women’s risk of miscarriage during a three- or seven-day window. Women living outside the state of Utah were not considered in the study.

We are really only seeing the most severe cases during a small window of time. These results are not the whole picture.

Claire Leiser, Research Analyst and Study First Author, University of Utah Health.

According to Leiser, the outcomes of the study indicate that there might be an elevated risk for an individual. However, the study only captured women who sought aid at an emergency department of just one hospital in the area, and did not account for women who might have sought outpatient care through their primary care providers or obstetricians.

Women exposed to increased levels of nitrogen dioxide (16% for 10 ppb increase at the time of the seven-day window) were found to have a slightly increased risk of miscarriage. Even though small particulate matter obviously tracks with nitrogen dioxide, these outcomes were not considerably linked with an elevated risk of miscarriage.

While we live in a pretty unique geographic area, the problems we face when it comes to air pollution are not unique. 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.

Matthew Fuller, MD, Study Senior Author and Assistant Professor of Surgery, University of Utah Health.

At the Wasatch Front, short periods of poor air quality were experienced mostly at the time of the winter months. This is the period when inversions trap pollutants near to the ground (for the seven-day window: PM 2.5 minutes = 0.3 µg/m3; PM 2.5 maximum = 73.0 µg/m3; O3 minimum = 4 ppb; O3 maximum = 80 ppb; NO2 minimum = 0.5 ppb; NO2 maximum = 65 ppb).

The team monitored the air quality by zip code, ascertaining six designated air basins inside the Wasatch Front, and then compared the air quality in the individual basin to their patients’ outcomes.

Next, the researchers performed a case cross-over analysis that helped estimate a woman’s risk of miscarriage many times in a month where exposure to air pollution differed considerably. This method eliminated other risk factors, for example, maternal age, from the study. However, the researchers were unable to establish the fetus’ age at the time of the miscarriage and hence could not identify a crucial period when the fetus would be most susceptible to pollutants.

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

According to Fuller, women should speak with their doctor regarding any health concerns. They can control the risk by avoiding outdoor physical activity on poor air quality days or applying an N95 particulate respirator face mask to filter out pollutants. Women can even utilize filters to reduce indoor pollution and, if possible, time conception so as to prevent seasonal episodes of poor air quality.

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