Heavy traffic inches along on a main ring road under heavy pollution in Beijing on July 19, 2016. A new study has linked outdoor air pollution to millions of preterm births worldwide. Photo by Stephen Shaver/UPI | License Photo
Feb. 16 (UPI) -- Researchers at the Stockholm Environment Institute at the University of York in England have found a correlation between millions of preterm births and outdoor air pollution levels.
The study found that in 2010, roughly 2.7 million, or 18 percent, of preterm births worldwide were linked to outdoor exposure to fine particulate matter, or PM2.5, which is harmful to humans.
PM2.5, particulate matter with a diameter less than 2.5 microns, comes from diesel vehicles and agricultural waste-burning, among others sources.
"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," Chris Malley, researcher in SEI's York Center and lead author of the study, said in a press release. "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."
An estimated 14.9 million births were preterm in 2010 with 4 to 5 percent from European countries and 15 to 18 percent in African and South Asian countries. The largest amount of global PM2.5-associated preterm births were from South Asia and East Asia with accounting for about 75 percent of the global total.
Of the 2.7 million preterm births worldwide, India accounted for about 1 million with China accounting for 500,000.
"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 and 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."
The study was published in Environment International.