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New study ties toxic dust from September 11 to more premature births

Dust in the aftermath of the World Trade Center collapse
Dust in the aftermath of the World Trade Center collapse
Spencer Platt/Getty Images News

The dust that settled in the neighborhoods around the World Trade Center after the 9/11 attacks was a toxic, caustic blend, containing pollutants tied to cancer, asthma, and other respiratory problems. Most concern — and compensatory funding — has concentrated on Ground Zero workers and the family members of victims.

But a new study resurfaces a less-discussed issue related to that dust cloud: the dust's impact on birth outcomes in the neighborhoods immediately surrounding the World Trade Center.

What did the authors find?

The study, released earlier this week in the National Bureau of Economic Research, found that the probability of premature birth went up 2.2 percentage points on average among infants exposed to the dust during fetal development. Not all infants were affected equally: among the group exposed during the first trimester, that figure climbs to 6.8 percentage points. Both are substantial increases over the baseline probability of about 8 percent.

Boys were more likely to suffer from adverse birth outcomes than girls, which is consistent with an existing "fragile male" theory in the medical literature; males generally seem to be more sensitive to in-utero shocks than females.

This is a more controversial finding than you might think

There are a lot of factors that are associated with adverse birth outcomes: having a low socioeconomic status, poor nutrition, inadequate prenatal care, smoking. And air pollution.

In the author's words, the fallout from 9/11 was one of the "worst environmental disasters to have ever befallen New York City." Carcinogenic and mutagenic air pollutant levels were some of the highest ever reported outdoors.

But, puzzlingly, past research hadn't shown any effects of exposure to the toxic dust from the World Trade Center collapse on birth outcomes. Maybe, the authors hypothesized, there were problems with how the past studies had been conducted.

The women who lived in the neighborhoods most affected by the 9/11 dust were systematically different from women in other parts of New York City, and past research didn't account for that very well. The neighborhood around the World Trade Center is a wealthy one; generally speaking, these women enjoyed socioeconomic advantages that made them more likely to have healthy births. Comparing a group of advantaged women to a group of "average" controls could obscure effects from the dust cloud.

To work around these issues, the authors decided to compare birth outcomes across children with the same mother. Some were exposed to the dust in utero, while their siblings functioned as "controls", having been born either before or conceived after the catastrophe. This way, things that stay constant in the mother across time — like her general health habits and her socioeconomic status — wouldn't bias the study results.