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Air Pollution and Infant Health

[The authors] find consistently negative effects of exposure to pollution, especially carbon monoxide, both during and after birth. The effects are considerably larger for smokers than for nonsmokers, and for older mothers. The effects of pollution also may be larger for babies born to mothers at risk for poor birth outcomes.

In Air Pollution and Infant Health: Lessons from New Jersey (NBER Working Paper No. 14196), co-authors Janet Currie, Matthew Neidell, and Johannes Schmieder estimate how exposure to carbon monoxide, ozone, and particulate matter affected infant health in New Jersey during the 1990s. They combine information taken from birth certificates on mothers' address with data on air quality from New Jersey air pollution monitors. This research, in addition to a large sample size -- all infant births and deaths recorded by the New Jersey Department of Health from 1989 to 2003 -- has three innovative features: the researchers can select mothers living closest to air monitors; they can follow mothers over time to control for unobserved characteristics; and, they can examine the interaction between air pollution and smoking, or other predictors of poor infant health.

The authors find consistently negative effects of exposure to pollution, especially carbon monoxide, both during and after birth. The effects are considerably larger for smokers than for nonsmokers, and for older mothers. The effects of pollution also may be larger for babies born to mothers at risk for poor birth outcomes because of chronic illness or other complications. When the sample was pared to include only children who had died in their first year, and their siblings, the resulting estimates suggest that a one unit increase in average maximum carbon monoxide increased the risk of infant death by an estimated 2.5 percent from a base of 40 percent.

The authors point out that their estimates may understate the health impact from pollution exposure. Residence within 10 kilometers is a relatively crude proxy for individual pollution exposure, and they did not measure any fetal losses that may have been caused by pollution. Given that automobiles are the main source of carbon monoxide emissions, they also note that their results "have important implications for the regulation of automobile emissions."

-- Linda Gorman