Wildfire smoke exposure during pregnancy increases preterm birth risk


Date:
August 23, 2021
Source:
Stanford University
Summary:
Smoke from wildfires may have contributed to thousands of additional
premature births in California between 2007 and 2012. The findings
underscore the value of reducing the risk of big, extreme wildfires
and suggest pregnant people should avoid very smoky air.



FULL STORY ========================================================================== Exposure to wildfire smoke during pregnancy increases the risk that a
baby will be born too early, a new Stanford University study suggests.


==========================================================================
The study, published Aug. 14 in Environmental Research, finds there may
have been as many as 7,000 extra preterm births in California attributable
to wildfire smoke exposure between 2007 and 2012. These births occurred
before 37 weeks of pregnancy when incomplete development heightens
risk of various neurodevelopmental, gastrointestinal and respiratory complications, and even death.

Wildfire smoke contains high levels of the smallest and deadliest type
of particle pollution, known as PM 2.5. These specks of toxic soot, or particulate matter, are so fine they can embed deep in the lungs and pass
into the bloodstream, just like the oxygen molecules we need to survive.

The research comes as massive wildfires are again blazing through parched landscapes in the western U.S. -- just a year after a historic wildfire
season torched more than 4 million acres of California and produced some
of the worst daily air pollution ever recorded in the state. 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.

This year could be worse, said Stanford environmental economist Marshall
Burke, a co-author of the new study. And yet much remains unknown about
the health impacts of these noxious plumes, which contribute a growing
portion of fine particle pollution nationwide and have a different
chemical makeup from other ambient sources of PM 2.5, such as agriculture, tailpipe emissions and industry.

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



========================================================================== Extreme wildfires The new results show wildfire smoke may have contributed
to more than 6 percent of preterm births in California in the worst
smoke year of the study period, 2008, when a severe lightning storm,
powerful winds, high temperatures and a parched landscape combined for a
deadly and destructive fire season -- one that has now been dwarfed by
the record-setting infernos of 2020 and ongoing blazes like the Dixie
fire in Northern California.

"In the future, we expect to see more frequent and intense exposure
to wildfire smoke throughout the West due to a confluence of factors,
including 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," said lead author Sam Heft-Neal, a research scholar at Stanford's Center on Food Security and
the Environment.

The research provides new evidence for the value of investing in
prescribed burns, mechanical thinning, or other efforts to reduce
the risk of extreme wildfires. Given that premature births cost the
U.S. healthcare system an estimated $25 billion per year, even modest reductions in preterm birth risk could yield "enormous societal benefits,"
said Burke, an associate professor of Earth system science at Stanford's
School of Earth, Energy & Environmental Sciences (Stanford Earth). "Our research highlights that reducing wildfire risk and the air pollution
that accompanies it is one way of achieving these societal benefits."
'No safe level of exposure'


==========================================================================
The researchers analyzed 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 pulled 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 age,
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, regardless of race, ethnicity or income. And a
full week of exposure translated to a 3.4 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 5 additional micrograms per cubic meter to daily PM 2.5 concentrations. "If one can
avoid smoke exposure by staying indoors or wearing an appropriate mask
while outdoors, that would be good health practice for all," Shaw said.

The findings build on an established link between particle pollution and adverse birth outcomes, including preterm birth, low birth weight and
infant deaths. But the study is among the first to isolate the effect
of wildfire smoke on early births and to tease out the importance of
exposure timing.

"Our work, together with a number of other recent papers, clearly
shows that there's no safe level of exposure to particulate matter. Any exposure above zero can worsen health impacts," said Burke, who is also
deputy director of the Center on Food Security and the Environment and a
senior fellow at Stanford's Freeman Spogli Institute for International
Studies. "While as a society it will be extremely difficult to fully
eliminate all pollutants from the air, our research suggests that further reductions in key pollutants below current 'acceptable' levels could be massively beneficial for public health." This work was supported by
the Robert Wood Johnson Foundation and the March of Dimes Prematurity
Research Center at Stanford University School of Medicine.

========================================================================== Story Source: Materials provided by Stanford_University. Original written
by Josie Garthwaite. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sam Heft-Neal, Anne Driscoll, Wei Yang, Gary Shaw, Marshall Burke.

Associations between wildfire smoke exposure during pregnancy and
risk of preterm birth in California. Environmental Research, 2021;
111872 DOI: 10.1016/j.envres.2021.111872 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210823104330.htm

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