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.
What’s less clear are the economic implications of these complications — and that’s an important factor to consider in discussions about air pollution, which often split into two sides: the costs of pollution reduction, which generally fall on the shoulders of the industries responsible for creating it in the first place, versus the social costs of continuing to pollute.
“So we decided to quantify the disease burden and costs of preterm birth that could ultimately be traced to fine particulate matter,” Trasande said.
Trasande, along with New York University colleagues Patrick Malecha and Teresa Attina, took data on air pollution from the Environmental Protection Agency (EPA) and data on preterm births from the Centers for Disease Control and Prevention (CDC). They used previous research on the risks of preterm birth associated with exposure to particulate matter to estimate how many premature babies were caused by pollution exposure in 2010. They concluded that just over 3 percent of all the preterm births that year could be attributed to fine particulate matter — nearly 16,000 in all.
The researchers then turned their attention to the costs associated with these preterm births. Using a report from the National Academy of Sciences’ Institute of Medicine, they concluded that the direct medical costs came to about $760 million in 2010. Far weightier, though, were the costs associated with lost economic productivity.
One common consequence of preterm birth is the appearance of developmental disabilities. The researchers were interested in estimating the economic losses that result from these disabilities — essentially, the economic productivity that’s lost over the course of an individual’s lifetime as a result of cognitive impairments and the reduced ability to work.
Previous studies have drawn connections between preterm birth, decreases in IQ and an individual’s lifetime earnings. Drawing on that research, Trasande and his colleagues estimated that more than $4 billion were lost in 2010 as a result of reduced economic productivity. Altogether, the medical costs and lost economic potential added up to just over $5 billion.
While these are national estimates, the researchers did find that the effects were more severe in some parts of the country than others. The greatest percentage of preterm births attributable to pollution exposure was generally found to occur in major urban areas, and was overall highest in the Ohio River Valley, Southern California and the Southeast, as well as New York City, southeastern Pennsylvania and Chicago.
“The implications also spread beyond the U.S. to other parts of the globe where air pollution is likely to be more of a substantial problem,” Trasande said. “Insofar as exposures in third world countries where regulations are much more limited, it’s likely that air pollution contributes more substantially to preterm birth.”
The results highlight the importance of stricter pollution regulations to both public health and the economy, said Bruce Lanphear, a health sciences professor at Simon Fraser University in Canada. He cited a variety of concrete actions that could be taken to address the problem, such as improving public transportation in cities to cut down on traffic emissions and refraining from building schools or residential developments near major sources of pollution.
But he also noted that, when it comes to preterm births, there are a variety of other environmental influences besides fine particulate matter likely having an effect, including lead and mercury exposure. “It no longer makes sense to pit one risk factor like air pollution against another,” he said. “Instead we should be recognizing that preterm birth is the consequence of cumulative exposure to a series of risk factors.”
Still, there’s value in conducting targeted studies like Trasande’s, he said. “They estimate that air pollution accounts for about three percent of all preterm births, which is quite sizable,” he said, adding that these types of focused studies can help draw attention to specific policy changes that need to be made — which, when all combined, can have substantial impacts on public health.