Air pollution in the U.S. may be causing thousands of premature births each year, a new study suggests — costing the nation billions of dollars along the way. The study, published Tuesday in the journal Environmental Health Perspectives, lends support to a growing body of research pointing to the grim health consequences of air pollution all over the world and its spectacular economic burdens.

The new study focuses on a type of pollution known as fine particulate matter — tiny particles, less than 2.5 micrometers in diameter, that can be emitted by traffic, factories and other industrial activities. Exposure to particulate matter has been implicated in all kinds of adverse health outcomes, particularly cardiovascular problems, and is believed to be responsible for millions of premature deaths every year. Now, increasing evidence is also linking it to problems related to pregnancy and birth, including preterm birth, said Leonardo Trasande, an associate professor of pediatrics at New York University’s School of Medicine.

The mechanisms behind this phenomenon are not entirely understood, but it’s believed that exposure to air pollution can cause inflammation of the placenta during pregnancy, which can ultimately lead to an early delivery. Preterm birth — which is usually defined as delivery that occurs more than three weeks ahead of term — is associated with a variety of medical problems including an increased risk of infant mortality, breathing and feeding difficulties, cerebral palsy, increased risk of developing other diseases and developmental delays that can lead to cognitive impairment throughout life.