Outdoor air pollution, largely from fossil fuel burning, is a major cause of morbidity and mortality in the U. S., costing billions of dollars every year in health care and loss of productivity1. The developing fetus and young child are especially vulnerable to neurotoxicants, such as polycyclic aromatic hydrocarbons (PAH) released to ambient air by combustion of fossil fuel and other organic material. Low income populations are disproportionately exposed to air pollution. Based on the results of a prospective cohort study in a low-income population in New York City (NYC) that found a significant inverse association between child IQ and prenatal exposure to airborne PAH, we estimated the increase in IQ and related lifetime earnings in a low income urban population as a result of a hypothesized modest reduction of ambient PAH concentrations in NYC of .25 ng/m3. For reference, the current estimated annual mean PAH concentration is~ 1 ng/m3. Restricting to NYC Medicaid births and using a 5% discount rate, we estimated the gain in lifetime earnings due to IQ increase for a single year cohort to be $215 million (best estimate). Using much more conservative assumptions, the estimate was $43 million. This analysis suggests that a modest reduction in ambient concentrations of PAH is associated with substantial economic benefits to children.