The regulation of air pollution has reduced its toll on heart and lung diseases. For example, the Clean Air Act Amendments of 1990 helped avert an estimated 160,000 deaths and 86,000 hospitalizations in 2010 alone.1 However, a growing body of research suggests that polluted air also puts our brain in harm’s way.

Chronic exposure to traffic-related pollutants may increase the risk of neurological disorders. Both short and long-term exposures have been associated with reduced human capital, including the academic performance of schoolchildren and the productivity of workers across the adult lifespan. As Matthew Neidell of Columbia University and Joshua Graff Zivin of the University of California, San Diego, wrote in 2018, "The ubiquity of these less lethal impacts, revealed by emerging economic research on labor productivity and human capital accumulation, can add up to considerable, society-wide impacts across the globe."

Components of Outdoor and Indoor Air Pollution

Estimating the subtle effects of air pollution requires long-term air quality data. The Clean Air Act has made much of this information available to researchers and the general public through an extensive monitoring network for selected outdoor air pollutants. Today, this national network contains more than 4,000 monitoring stations operated mainly by state environmental agencies. These agencies send hourly or daily measurements of pollutant concentrations to a central database maintained by the U.S. Environmental Protection Agency (EPA).

The U.S. EPA defines and monitors six "criteria pollutants" in ambient air: particulate matter (PM), ground-level ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. PM includes a variety of tiny airborne solids and droplets emitted by vehicles, factories, wildfires, and other anthropogenic and natural sources. Additional pollutants from outdoor sources include methane, volatile organic compounds (VOCs), pollen, metals, and other sulfur and nitrogen oxides.

Pollutants generated outdoors can travel indoors, where Americans spend on average 90% of their time. Some of the energy-efficient building practices intro-duced in the 1970s allowed indoor pollutants to concentrate; by the 1980s, reports of "sick building syndrome" had begun to appear in the medical literature.

Newer building rating systems such as Leadership in Energy and Environmental Design® recognize the importance of optimal ventilation. Read full document (pdf format)