A new study published in Environment International reports that outdoor air pollution is linked with 2.7 million preterm births per year.
The study, which was led by a team from The Stockholm Environment Institute (SEI) at the University of York, found that in 2010, about 2.7 million preterm births globally — or 18% of all preterm births — were associated with outdoor exposure to fine particulate matter (PM2.5).
Results suggest that addressing major sources of PM2.5 — from diesel vehicles, to agricultural waste-burning — could save babies’ lives and improve health outcomes.
For the first time, the study quantified the global impact by combining data about air pollution in different countries with knowledge about how exposure to different levels of air pollution is associated with preterm birth rates.
“This study highlights that air pollution may not just harm people who are breathing the air directly – it may also seriously affect a baby in its mother’s womb,” said Chris Malley, a researcher in SEI’s York Centre, at the University of York, and lead author of the study. “Preterm births associated with this exposure not only contribute to infant mortality, but can have life-long health effects in survivors. This study adds an important new consideration in measuring the health burden of air pollution and the benefits of mitigation measures.”
The largest contribution to global PM2.5-associated preterm births was from South Asia and East Asia, which together contributed about 75% of the global total.
India alone accounted for about one million of the total 2.7 million global estimate, and China for about another 500,000. Western sub-Saharan Africa and the North Africa/Middle East region also had particularly high numbers, with exposures in these regions having a large contribution from desert dust.
“There is uncertainty in these estimates because the concentration-response function we used is based mainly on studies in the United States and Europe,” Malley said.
“Not only don’t we know whether the relationship is the same at much higher concentrations, such as those found in some Indian or Chinese cities, but the prevalence of other risk factors also varies considerably.
“Expectant mothers in many places are also exposed to high levels of indoor pollution from cooking smoke. Resolving these uncertainties will require more studies in these countries and regions.”
“To reduce the PM2.5 problem, you need to control many different sources, but in many developing countries, certain emission sources dominate,” said Johan C.I. Kuylenstierna, co-author of the study, SEI’s Policy Director.
“This includes emissions from cooking with biomass fuels (which is also associated with very harmful indoor pollution), diesel vehicles and other transport, and particles emitted when agricultural residues are burned in fields.”