Wildfire Exposed Women Give Birth Early

Pregnant women exposed to wildfire smoke are likely to give birth early, which has heightened the risk during pregnancy, according to a new study by the Stanford University.

The journal Environmental Research published the study. The research records as many as 7000 extra preterm births in California due to wild fire smoke exposure between 2007 and 2012. The researchers said that these births occurred before 37 weeks of pregnancy when incomplete development heightens risk of various neuro-developmental gastrointestinal and respiratory complications, and even death.


The study said that smoke from wildfire contained high levels of smallest and deadliest type of particle pollution, known as PM 2.5. These are so fine that they can embed deep in the lungs and pass into the bloodstream just like the oxygen molecules.

The Stanford University study comes out at a time the world is witnessing massive wildfires. In California, wildfire torched more than four million acres. During the 2020 fire season, more than half of the state’s population experienced a month of wildfire smoke levels in the range of unhealthy to hazardous.

Stanford environmental economist and co-author of the study Marshall Burke said that it remained unknown about the health impacts of these noxious plumes, which contribute a growing portion of fine particle pollution nationwide. They also have a different chemical makeup from other ambient sources of PM 2.5, such as agriculture, tailpipe emissions and industry.


The authors said that one possible explanation for the link between wildfire smoke exposure and preterm birth was that the pollution might trigger an inflammatory response, which then sets delivery in motion. The increased risk is relatively small in the context of all the factors that contribute the birth of a healthy, full-term baby. “However, against a backdrop where we know so little about why some women deliver too soon and why others do not, finding clues like the one here helps us start piecing bigger puzzle together,” said co-author Gary Show, professor of professor of paediatrics and co-primary investigator of Stanford’s March of Dimes Prematurity Research Center.

The new study showed that wildfire smoke might have led to more than six per cent of preterm births in California in the worst smoke year of the percent of the study period 2008.

Lead author Sam Heft-Neal, a research scholar at Stanford’s Centre on Food Security and the Environment pointed out that one could except to see more frequent and intense exposure to wildfire smoke throughout the West due to a confluence of factors. These factors include climate change, a century of fire suppression and construction of more homes along the fire-prone fringes of forests, scrublands and grasslands. As a result, the health burden from Smoke exposure – including preterm births – is likely to increase, the professor said.


The researchers looked into satellite data of smoke plumes from the National Oceanic and Atmospheric Administration (NOAA) to identify smoke days for each of 2,610 zip codes. They paired these data with estimates of ground-level PM 2.5 pollution which were developed using a machine learning algorithm that incorporates data from air quality sensors, satellite observations and computer models of how chemicals move through Earth’s atmosphere. They also collected additional data from California birth records, excluding twins, triplets and higher multiples, which commonly arrive early,

After accounting for other factors known to influence preterm birth risk such as temperature, baseline pollution exposure and the mother’s income, race or ethnic background, they looked at how patterns of preterm birth within each zip code changed when the number and intensity of smoke days rose above normal for that location.

They found every additional day of smoke exposure during pregnancy raised the risk of preterm birth. In addition, a full week of exposure percent greater risk relative to a mother exposed to no wildfire smoke.

Exposure to intense smoke during the second trimester.- between 14 and 26 weeks of pregnancy – had the strongest impact, especially when smoke contributed more than five additional micrograms per cubic metre to daily 2.5 concentrations.

Burke noted that their work along with other works showed that there was no safe level of exposure to particulate matter.


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