By Joshua Yu
The Fourth of July is usually a time for awkward family gatherings and sweltering barbeques. But with COVID-19 precautions this year, many families celebrated this holiday from the comfort and safety of their own homes. Even with the coronavirus upending much of what we consider normal, one thing remained constant this July 4: fireworks.
From coast to coast, many still pulled up socially-distanced lawn chairs to watch the dazzling show in the night sky. However, over recent years, research has highlighted the environmental and human health concerns of fireworks. From respiratory issues to water pollution, the short-lived fun of fireworks is causing long-term harm.
From the accidental discovery of gunpowder in ancient China to the development of modern-day fireworks, the essential ingredients of these controlled explosions have remained the same for thousands of years: a strong oxidizing agent and a fuel source. This fuel-oxidizer system allows for a large enough transfer of energy to create an explosion. According to Chinese folklore, the explosions scared away evil spirits and the colorful display quickly became popular at weddings and holidays. From there, the use of gunpowder for both weaponry and celebratory ceremonies spread across the world.
The vivid colors of modern-day fireworks are produced by the heating of salts with perchlorate, a common oxidizing agent. The heating causes electrons in the salts to excite into a higher energy level. When an excited electron falls back down into its most stable state, it emits energy corresponding to a color on the visible light spectrum. Throughout the years, scientists have catalogued the colors associated with various salts, allowing pyrotechnicians to choreograph complex shows.
Advancements in aerial launching mechanisms allow fireworks displays to be seen from miles away. To ensure that ignition takes place thousands of feet in the air, pyrotechnicians have refined the composition of black powder, a major reactant in modern fireworks. The larger each grain of black powder is, the slower the explosion, giving pyrotechnicians more control over each firework.
Environmental advocates and health experts have raised concerns about the health implications of shooting chemicals into the sky. The lingering smoke after a fireworks display consists of particulate matter which falls back on nearby soil and streams, and greenhouse gases that linger in the atmosphere. These gases contribute to climate change by trapping heat inside the Earth’s atmosphere.
Perchlorate has come under fire for potential respiratory health concerns. Researchers following a firework show in Oklahoma in 2017 found that it took upwards of 80 days for the perchlorate to disperse in the surface water of a lake over which fireworks were launched. Concerningly, high perchlorate levels have been found around firework manufacturing sites as well. Perchlorate has been shown to impact thyroid function, which can inhibit the release of specific hormones required to maintain body homeostasis. Though there has not been any published research directly linking fireworks and thyroid deterioration, future studies should focus on the specific cardiovascular implications of fireworks.
A study conducted in London found that there were increased levels of nitric oxide and sulfur dioxide following firework shows. These two chemicals are major contributors to acid rain and have been linked to irritated lungs. In fact, epidemiologists in 2010 found that hospital admissions for asthma and other respiratory diseases spiked in the days following large firework shows in India.
The development of daytime fireworks and complex 3-D choreography, among other innovative techniques, will continue to amaze spectators every year. But as firework displays become more extravagant, their impact on human health and the environment will continue to grow. As you pack up your lawn chairs after your next fireworks show, take a moment to pause and think about what is left in the air as the colors fade into the night sky.