Getty Images/iStockphoto

If protecting the environment alone wasn’t reason enough to take measures to reduce air pollution, the massive global health implications of rising preterm birth rates certainly should be.

Each year, 15 million babies around the world ― that’s roughly 1 in 10 infants ― are born prematurely, according to the World Health Organization.

Along with factors like poverty and maternal health status, new research suggests that air pollution is a major risk factor for births occurring at 37 weeks or earlier.

The findings, published last week in the journal Environment International, showed that 2.7 million preterm births across 183 countries in 2010 were associated with a common air pollutant known as fine particulate matter, or PM.

PM is a dangerous form of air pollution consisting of tiny particles in the air that reduce visibility and can cause air to appear hazy. Primarily released from sources like diesel vehicles and agricultural waste-burning, PM can penetrate deep into the lungs and contribute to the development of health problems.

“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,” Dr. Chris Malley, a researcher at the University of York and the study’s lead author, said in a statement. “Preterm births associated with this exposure not only contribute to infant mortality, but can have life-long health effects in survivors.”

For the study, researchers from Sweden, the U.S. and the U.K. looked at data on air pollution levels in different countries, analyzing PM levels by region. Then, they compared PM levels with what scientists know about a mother’s risk of having a preterm baby based on her level of air pollution exposure.

Countries in Africa and Asia were the most deeply affected by pollution-related preterm births, with 75 percent coming from South and East Asia. India alone accounted for roughly 1 million of the 2.7 million pollution-related preterm births.

In terms of overall preterm birth rates globally, India ranks number one, followed by China, Nigeria, Pakistan and the United States.

Environment International The image above shows the percentage of total preterm births associated with outdoor PM exposure in 2010.

A woman living in urban India or China may inhale as much as ten times more air pollution than someone living in rural England, for example, the study’s authors note.

The researchers admit that it’s difficult to determine the exact causes of preterm birth, and that more research is needed, especially in places like India and China, to more clearly determine the risk factors.