Air pollution contributed to almost six million preterm births and almost three million underweight babies around the world in 2019 alone, according to a huge new global study.
Mounting evidence is showing that exposure to PM2.5, tiny airborne particles of pollutants like soot and ash, during pregnancy has a tight link to an increased risk of their babies being born too small or too early. It’s also well established that preterm birth complications are the leading cause of death among children under 5 years of age worldwide, known to significantly increase the risk of many diseases. The risk is especially high in low-income settings, where around half of the babies born at or before 32 weeks (2 months early) die.
As reported in the journal PLOS Medicine, scientists at UC San Francisco and the University of Washington looked to get a global snapshot of how air pollution affected childbirth and child mortality in 2019. Using huge amounts of existing data, they carried out a meta-analysis of several key indicators of pregnancy across the world, including gestational age at birth, reduction in birth weight, low birth weight, and preterm birth.
Much impact was seen in developing countries. The findings suggest the global incidence of preterm birth and low birthweight could be reduced by almost 78 percent if air pollution were minimized in Southeast Asia and sub-Saharan Africa. However, developed parts of the world also felt the sting. The researchers estimate there were almost 12,000 preterm births in 2019 in the US that can be linked to outdoor air pollution.
Up to two-thirds of the detrimental effects on birth were linked to indoor air pollution, mostly from burning coal, dung, and wood inside the home in developing countries. The remaining third were related to ambient outdoor pollution caused by combustion processes from motor vehicles, fossil fuel burning, and industry.
The researchers behind this new report are also involved with the State of Global Air report. In 2020, the annual report took a close look at how air pollution was affecting pregnancy and childbirth, concluding that air pollution contributed to the deaths of 476,000 babies in 2019.
Scientists have not definitively explained why air pollution appears to be closely associated with preterm births. Broadly speaking, it’s known that air pollution can result in toxic chemicals in the blood and stress the immune system, which can weaken the placenta surrounding the fetus and lead to preterm birth. Studies have also indicated that soot particles can enter the fetal part of the placenta, which is likely to cause inflammatory responses and might also react with the DNA.
Whatever its cause, the researchers argue that the solution is all too obvious: “The air pollution-attributable burden is enormous, yet with sufficient effort, it could be largely mitigated,” Dr Rakesh Ghosh, lead study author and public health specialist at the Institute for Global Health Sciences at UCSF, said in a statement.
“With this new, global and more rigorously generated evidence, air pollution should now be considered a major driver of infant morbidity and mortality, not just of chronic adult diseases,” added Ghosh.