One in 10 babies in the United States is born prematurely, before 37 weeks of pregnancy. Preterm birth is the leading cause of death for children under five and is linked to numerous health problems that persist throughout life. Many factors can contribute to preterm birth but air pollution -- particularly fine particulate pollution -- is increasingly being linked to the incidence of premature birth in the US and elsewhere around the world. According to a study published this week in Environmental Health Perspectives, the annual economic costs of the nearly 16,000 premature births linked to air pollution in the US each year has reached $4.33 billion.
These costs stem from both direct healthcare expenses and costs associated with lifelong health problems. "Preterm babies who survive often face a life of health complications, including chronic disease, asthma, cognitive and motor problems and psychological impairments," explains Linda Franck, chair of family health care nursing at the University of California San Francisco School of Nursing.
"To our knowledge, this is the first time that such economic estimates are reported and suggest that considerable health and economic benefits can be gained through reductions in outdoor air pollution exposure in pregnancy," write lead study author Leonardo Trasande and colleagues at New York University.
"For a long time we've known that air pollution contributes to cardiovascular disease in adults and to asthma and other respiratory conditions in children," explains Trasande, New York University School of Medicine associate professor of pediatrics and environmental medicine and the study's lead author. Now a growing number of studies have linked particulate pollution with low birth weightand preterm birth. These studies look both at where preterm births are occurring and also how air pollution can adversely affect pregnancy through inflammation, stress, and other biological mechanisms.
There is also increasingly precise information showing where particulate pollution is occurring. This includes information collected by US states and by the US Environmental Protection Agency. Using such data about air pollution and the number of premature births per county in a year, Trasande and colleagues were able to estimate how many preterm births could be traced to particulate matter.
Overall, the study looked at nearly 4 million births in the lower 48 US states, of which about 12 percent were preterm. Of those, the researchers found that 3.32 percent of all preterm births recorded in 2010 were attributable to exposure to fine particulate matter (PM 2.5). The greatest number of these births occurred in urban areas, especially in Southern California, the Eastern US, and the heavily industrial Ohio River Valley.
The research team then linked those premature births to healthcare costs. Those associated with hospital stays and other immediate events related to preterm birth were estimated at $760 million. Added to these costs are an additional estimated $3.57 billion over the children's lifetimes. These include medical expenses during the first five years of life and costs associated with long-term health implications -- overall poor health, specific neurological, psychological, and physical problems, lost economic productivity due to lowered IQ, work absences, disabilities, and early death.
Children born prematurely "are prone to social isolation and anxiety and are less likely to attend college or obtain a well-paid job," explains Franck, who did not work on this study but works with UCSF's Premature Birth Initiative. "The emotional and financial toll on families and the country is enormous."
And "medical costs are always an underestimate of the total costs," adds Tracey Woodruff, UCSF School of Medicine professor of reproductive sciences, obstetrics and gynecology, whose research includes the relationship between pollution and preterm birth. "There are other issues beside hospital costs. These don't value the emotional burden and all the other aspects of working with a sick child," she says.
And while these additional costs are not included in the study's estimates, which Trasande calls "conservative," the study does acknowledge them, saying they should "be taken into account when considering the benefits that could be achieved" by reducing the pollution associated with increased preterm birth.
"We are seeing some of the worst, most alarming statistics we've seen in history," says Larry Rand, assistant professor of reproductive sciences and principal investigator with UCSF's Preterm Birth Initiative in a mini-documentary made for the program. California has some of the country's highest rates of preterm birth, he says. Children born prematurely, he says, "face lifelong obstacles." And while rates of premature birth have dropped somewhat in recent years, preterm birth remains so prevalent that Rand calls it "an epidemic."
"The bottom line," says Franck, "is that in industrialized countries, mortality has decreased fairly steadily over the last decade," for babies born prematurely. But, she says, "The number of children with moderate or severe complications remains at a steady level. We've made incremental progress in saving babies but not done well with the outcomes."
Asked if air pollution crosses the minds of parents of premature babies, Franck responds: "From looking at families for many years, the guilt that parents feel about why a baby would be born early, anything they might have done, it all runs through their minds… Unfortunately we can't always give them any answers."
And as the new study's data shows, when it comes to air pollution and premature birth, these impacts aren't distributed equally across the country. Additional data shows that low income and communities of color bear the burden of preterm birth disproportionately.
While the numbers in the study published today are startling, Trasande explains that it may actually be an underestimation of the actual number of premature births a year. The study's estimates are limited to births technically categorized as preterm, those occurring before 37 weeks of pregnancy. There may, however, be babies whose early births are not fully captured due to miscalculation during pregnancy. "Shift the curve to the right that way and it shifts a lot of people to preterm birth," says Trasande. And such a shift, however small, could have enormous implications.
The study's findings "speak to the ongoing need to limit fine particulate emissions," says Trasande, whether from cars, coal fired power plants, or industry. We're making some progress in air quality standards, but he says, "standards don't mean action."
"We're not out of the woods yet by any stretch of the imagination."