Abstract

Public fireworks shows are widely used for national holiday celebrations, religious ceremonies, and sports events. However, fireworks produce short-lived atmospheric particulate matter (PM) peaks, posing a risk to spectators’ health. Every year, public fireworks shows expose over 140 million Americans to episodic transient PM2.5 peaks that exceed air quality standards by up to 10 times in the United States alone. Yet the magnitude and timing of this representativeness gap have not been measured within an event. This paper investigates the Independence Day fireworks display over Lake Union, Seattle, WA, USA, using a low-cost PM network deployed up to 2 km from the launch site. We evaluated the network observations against routine monitoring data from regulatory stations within 10 km of the launch site and generated a backward–forward Lagrangian stochastic dispersion model, calibrated with the network. Spectator zone PM2.5 concentrations varied by over threefold across sensors within 1.5 km. Duration above the World Health Organization (WHO) 24 h PM2.5 guideline concentration level at network sensors varied from 1 min to nearly 30 min, and regulatory hourly averaging retained 57% of the near-field peak signal on average and only 22% in the worst case. Peak detection at some regulatory stations was delayed by one to two hours compared with the network. The dispersion model, using only network data and public regional wind data, captured the launch site location to within ~100 m and provided minute-scale estimates of PM2.5 and PM1 concentrations across the spectator zone. The findings demonstrate and quantify, for a single event, the representativeness gap expected when transient near-field fireworks plumes are evaluated using spatially sparse and hourly averaged regulatory observations.

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