In a developing fetus, one of the the last organs to form fully is the lungs. The National Institutes of Health (NIH) defines a preterm birth (PTB) as one that occurs before 37 weeks of gestation. This definition is, in part, due to the fact that the fetus does not begin to develop pulmonary surfactant, a vital lipoprotein that allows the lungs to remain expanded as one breathes, until around 30 weeks. All told, a child born before 36 weeks will struggle to breathe on his/her own.
PTB remains a serious issue in the United States. It is responsible for 35% of infant deaths, making it the single leading cause of infant mortality, and it can contribute to major cognitive and developmental disabilities. Given the vital role that lung function plays in infant health, it is clear that PTB directly affects a child’s ability to take in air. But what about the reverse? Could the air that a fetus (and its mother) breathes contribute to PTB? New research suggests that’s the case.
Drawing the link between air quality and preterm birth
Earlier this week, the journal Environmental Health Perspectives published a study from three researchers at New York University that explored the connection between air pollution and PTB. As I’ve noted in the past, there is a plethora of studies linking air pollution to low birth weight, PTB, and infant mortality. This study builds upon that literature by determining the proportion of PTB that is directly attributable air pollution.
In order to explore this issue, the researchers decided to examine the impact of the single worst criteria air pollutant, fine particulate matter (PM2.5). They assembled county level PTB values during 2010 from the Centers for Disease Control’s (CDC) WONDER database. Next, sing established epidemiological methods, they then calculated the proportion of PTBs in each county attributable to PM2.5 pollution, using a reference ambient concentration of 8.8 micrograms per cubic meter (μg/m3). This level of pollution is what the World Health Organization uses to determine the global burden of disease caused by outdoor air pollution.
Nationally, PTB rates have fallen to 11.3%, but they remain far too high. According to the study’s authors, 3.32% of all preterm births in the continental United States during 2010 were due to particle pollution. This amounts to 15,808 PTBs in that year alone.
Calculating the social costs of PTB from air pollution
But the authors did not stop there. Theirs is the first study to quantify the economic impacts of this link. They developed estimates of the medical costs associated with PTB for children from birth through 5 years of age. To this value, they added the costs of lost economic productivity from reduced cognitive function and potential.
According to the study, the average premature child suffers an 11.9 point IQ decrement, which leaves them significantly disadvantaged compared to their peers.
Based on the best available data, the authors find:
These estimated numbers of attributable preterm births cost $760 million in medical care…and $4.33 billion…in lost economic productivity was also identified (based on estimated reductions in IQ and estimated consequences for productivity over a lifetime). In total, we estimated that $5.09 billion in preterm birth-related costs (medical care costs and lost economic productivity combined) could be attributed to PM2.5…
Uneven distribution of costs
But, predictably, these costs are not distributed evenly among counties or demographic groups. The single highest fraction of PTBs attributable to particle pollution occurred here in Ohio, where 5.44% of all PTBs – 924 children in 2010 – are due to our polluted air. Compare this to New Mexico and Wyoming, states with drastically lower PTB rates, where the attributable fraction is just 0.12%. This leads to total annual costs of just under $300 million in Ohio: $253 million in lost economic productivity and $44.4 million in medical care costs.
Unfortunately, the authors did not provide supplemental data breaking down these attributable fractions and costs by county or metro area. They do provide a map that shows the percentage of PTB attributable to particle pollution by county, but it lumps all values above 5% together.
That said, Greater Cleveland has extremely high levels of both particle pollution and PTB. Cuyahoga County is one of just nine nonattainment areas for the 2012 PM2.5 standard, and Cleveland has the third highest PTB rate in the country. Pollution almost certainly accounts for a larger proportion of PTBs here then the state average. Additionally, based on data from the Ohio EPA, the annual ambient concentration of PM2.5 in Cuyahoga County during 2010 was 13.7μg/m3, 56% higher than the reference level of 8.8μg/m3 that the authors applied. Given this fact, I have to conclude that significantly more than 5% of PTBs in this region are tied to air pollution.
But let’s be conservative and assume that particle pollution is only responsible for 6% of preterm births in Cuyahoga County. That still means that the parents of 126 premature children born in 2010 can place the blame squarely on our elevated levels of particle pollution. If we raise this threshold to 10% – not an unreasonable assumption – this number increases to 209.
Additionally, Cuyahoga County accounts for 12.3% (2,093 out of 17,007) of all PTBs in Ohio during 2010. If we apportion this share, that means the county incurred $36.6 million in costs.
These numbers are equal parts dumbfounding and infuriating. The quality – or lack thereof – of the air we breathe day in and day out affects everyone of us here in Greater Cleveland. But it doesn’t just harm those of who have the means to choose where we live. It reaches into the womb and directly affects the futures of children who have never even taken a breath.
It’s well past time we stop pretending that air quality doesn’t affect every one of us profoundly and in a number of ways.