Differences between Weekday and Weekend Air Pollutant Levels in Atlanta; Baltimore; Chicago; Dallas–Fort Worth; Denver; Houston; New York; Phoenix; Washington, DC; and Surrounding Areas

Weekends provide an opportunity to examine how urban O3 and PM nitrate respond to large reductions in precursor emissions, although future emission reductions may differ in spatial and temporal distribution from those that presently occur on weekends. Weekend reductions of urban NOx emissions generate little change in peak O3 and mean PM nitrate concentrations at most urban U.S. locations. The findings from this study suggest that timely attainment of O3 standards will require greater emphasis on reducing VOC emissions in major metropolitan areas.