Satellites show air pollution influences fetal development.
Kloog, I, SJ Melly, WL Ridgway, BA Coull and J Schwartz. 2012. Using new satellite based exposure methods to study the association between pregnancy pm2.5 exposure, premature birth and birth weight in Massachusetts. Environmental Health http://dx.doi.org/10.1186/1476-069X-11-40.
A Harvard study suggests that exposures to fine air pollution during pregnancy increases the risk for preterm delivery and low birth weight in newborns. Further, the findings suggest particles from industrial sources may play a bigger role in exposures than traffic pollution.
This study – the first of its kind – shows that satellites offer a more accurate and comprehensive way to measure exposure and, therefore, health risks from particulate air pollution, especially in rural areas.
Previous studies suggest a link between particulate air pollution and pregnancy – that expectant mothers exposed to air pollution have increased risks of delivering a low birth weight or premature baby. These earlier studies mostly relied on ground-based monitors to measure air pollution, a method that can easily over or under estimate exposures for people who live far away from the monitors.
Satellite data allow researchers to estimate pollutant levels more accurately over large geographic areas. Additionally, since satellites capture information daily, levels can be measured over long periods of time.
In this study, the researchers were also more certain that their measurements of particulate matter (PM2.5) were not directly emitted from traffic, since emissions from cars and trucks are on too fine a scale to be captured by the pixels in the satellite image.
They determined that the fine particulate pollution they did capture was likely sulfates that are released when coal is burned or that formed in the air potentially from traffic sources farther away.
In this study, Dr. Etai Kloog and his colleagues analyzed 634,244 births from the Massachusetts birth registry. The data represented all single live births from 2000-2008 in seven Massachusetts counties. The mothers' residences were mapped and estimates of fine particulate matter (PM 2.5) concentrations for the locations were derived from images taken by NASA's MODIS satellite. The expectant mothers' average exposures to PM 2.5 were estimated for three time periods: the entire term of pregnancy, the last trimester and the final month.
From the data, Kloog and his colleagues determined if increased exposure to pollution during these three times increased the risk of delivering a pre-term baby or having a low birth weight full-term baby (defined as less than 2500 grams, or about 5.5 pounds). Figuring out ways to reduce chances of these adverse birth outcomes is important since they can lead to adverse health problems later in childhood and adulthood.
To isolate the association between PM 2.5 and adverse birth outcomes, the researchers accounted for health, socioeconomic status, traffic density and the amount of open space near where they lived.
On average, for every 10 percent micrograms per cubic meter of air (μ/m3) (Corrected 9/18/12) increase in the mother's exposure to PM 2.5 during the entire pregnancy, the baby's birth weight dropped almost an ounce (14 grams). The same 10 percent elevation in exposure also increased the odds of a premature birth by 6 percent.
PM2.5 could indirectly affect the fetus by potentially affecting the mother’s ability to deliver nutrients due to constriction of blood vessels. Particulate matter can also have direct effects, as the particles often contain toxics, such as metals and chemicals.
As satellite technology improves, satellite measures of air pollution – like particulate matter – will become more commonplace in human studies, the authors suggest. The images offer a robust way to look at air pollution over space and time, especially in regions not well covered by the national air pollution monitoring systems.
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