Our estimates confirm that carbon monoxide has a significant effect on fetal health even at the relatively low levels of pollution experienced in New Jersey in recent years, and that it has further effects on infant mortality conditional on measures of health at birth.
In particular, we estimate that a one unit change in mean CO during the last trimester of pregnancy increases the risk of low birth weight by 8%. Furthermore, a one unit change in mean CO during the first 2 weeks after birth increases the risk of infant mortality by 2.5% relative to baseline levels.
These findings for CO are robust to many different specifications. We also find that the effects of CO on infant health at birth are two to six times larger for smokers and for mothers over age 35.
Since the major source of CO in urban areas is automobile exhaust, these findings have implications for regulations of automobile emissions.