Effects of Independence Day Fireworks on Observed PM2.5 Concentrations

Celebratory fireworks displays are known to increase atmospheric concentrations of a variety of pollutants, including fine particulate matter. However, quantitative estimates of the increase in PM2.5 (particulate matter of diameter less than 2.5 microns) are not generally available, and these “emissions” are generally not included as sources in air quality forecast models, in part because source strength and timing are not well established. We address these gaps through analysis of hourly PM2.5 observations from over 300 air pollution monitoring sites in the U.S.

Data from the U.S. Environmental Protection Agency's Air Quality System Data Mart for several years during 1999-2013 (3-11 years per station, depending on availability) were used to compare the 24-hour periods beginning with 8 pm on July 4 with 24-hour periods on four “control” days (July 2, 3, 5, 6). We find statistically significant increases in hourly PM2.5 concentrations at many sites in the evening hours of July 4 and early morning hours of July 5. At some locations, concentration increases are large enough to cause 24-hour average values to exceed the National Ambient Air Quality Standard of 35 micrograms per cubic meter.