Fireworks inject color and light into the night sky. According to a new study, they also emit toxic metals into the air.
Heavy metals like titanium, copper, strontium, and even lead, are often packed inside fireworks to give the pyrotechnic explosions their vibrant glow. When fireworks explode, toxins spread through the air and can be breathed in.
In turn, these metals can potentially damage human cells and animal lungs, research published Wednesday in the Particle and Fibre Toxicology Journal suggests.
This troubling finding doesn't necessarily mean the health risks outweigh the rewards of a dazzling firework show. Researchers still don't know the health impacts of an at-home sparkler session or watching a firework show at a sports game.
“You can still have your celebrations and enjoy the whiz-bang of the sounds and colors but still protect people," study co-author Terry Gordon, an environmental medicine expert at NYU Langone Health, tells Inverse.
Gordon says there are four key strategies to stay safe and limit these potentially harmful effects:
- Set fireworks off outside.
- Stay upwind of the explosion.
- Choose non-lead fireworks.
- Make fireworks a special treat, not a frequent habit.
"While many are careful to protect themselves from injury from explosions, our results suggest that inhaling firework smoke may cause longer-term damage, a risk that has been largely ignored," Gordon says.
Up to this point, researchers have focused on firework-related injuries to life and limb. In 2018, fireworks were involved in an estimated 9,100 injuries treated in U.S. hospital emergency departments. Hands, fingers, legs, as well as the head, face, and ears are the most frequently damaged body parts. People can suffer burns, loss of eyesight or limbs, and sometimes death.
"Traditionally, people are worried about physical injuries and they should," Gordon says. "It is probably the biggest risk."
This is the first study to examine whether fireworks detonation injects significant amounts of toxic metals into the atmosphere, potentially harming human health.
To answer that question, Gordon rounded up 12 types of commercially available fireworks commonly sold in the United States including the Black Cuckoo, the Color Changing Wheel, and the Blue Storm firecracker.
Gordon and his team set them off in a stainless steel chamber and collected the emitted particles. Then, they exposed human cells and living mice to the particles and tested for the particles' toxicity.
Five of these commercially available fireworks significantly increased oxidation or reactive oxygen species (ROS), a process that can damage or kill cells. Black Cuckoo, a fountain-style firework, was the most toxic of the group — it was 10 times more damaging to human cells than a non-toxic saline solution.
Two of the fireworks, Black Cuckoo and Saturn Missiles, contained "exceedingly high" levels of lead, a heavy metal that can permanently disable young children when chronically exposed.
To create bright colors, heavy metals need to be exposed to high temperatures. This causes the chemical reaction that gives off a flash of colored light. For example, red fireworks can be made with strontium and blue fireworks with copper.
While those colors look striking, the inclusion of heavy metals isn't great for human health.
Some metals, like magnesium or copper, exist naturally in the human body. But when the body is overloaded with them, heavy metals can interfere with metabolic activity, put the body under oxidative stress, and sometimes drive cancer. They're especially harmful to babies and young children because they can stunt development — that's why heavy metals like lead have been banned from household goods.
The team also analyzed 14 years of air quality samples taken at dozens of sites across the United States by the Environmental Protection Agency (EPA). They found that levels of toxic metals were higher in samples taken near Independence Day and New Year's Eve celebrations than at any other time of the year — two holidays where fireworks are mainstays.
Importantly, scientists still don't know the health effects of fireworks on crowds, the influence of repeated exposure, or what constitutes a safe viewing distance or a "healthy" firework.
It is well known that in areas with high levels of ambient particulate matter with heavy metals — a polluted neighborhood or industrial area — there are increases in hospital visits for asthma, Gordon explains. There are also at times increases in cardiovascular and pulmonary morbidity — illnesses and deaths just from acute exposure.
You can imagine there are similar health risks happening if people are chronically breathing in firework smoke. Gordon worries about the recent uptick in firework use in U.S. cities over the past few weeks.
"Once or twice a year for a day or two is now becoming more of a longer-term exposure," Gordan says. "Maybe not as high concentration is on the Fourth of July celebrations, but it's more pollution."
Background: Particle matter (PM) has been associated with increased morbidity and mortality rates across the world. This study was designed to test the hypotheses that pyrotechnic firework displays introduce significant amounts of toxic metals into the atmosphere and are hazardous to human health. Size-selective emissions from 10 different fireworks displays were collected during particle generation in a dynamic, stainless steel chamber and tested for toxicity in cells. A subset of 2 particle types were tested in vivo in mice. At doses that did not produce cytotoxicity in an LDH assay, in vitro reactive oxygen species (ROS) formation was measured in bronchial epithelial airway (BEAS-2B) and human pulmonary microvascular endothelial (HPMEC-ST1.6R) cell lines treated with size- fractionated particles from the emissions of fireworks.
Results: Significant increases in ROS, in both cell types, were dependent upon the type of firework but not particle size. The in vitro ROS activity was correlated with lung inflammation produced in groups of mice treated by oropharyngeal aspiration with 0, 50, or 100 μg fireworks PM10/mouse. Trace metal analyses of the PM10 samples showed significant differences in metal content among fireworks type. Interestingly, the PM10 sample for the fireworks type producing the greatest in vitro ROS response in BEAS-2B cells contained ~ 40,000 and ~ 12,000 ppm of lead and copper, respectively. This sample also produced the greatest inflammatory response (i.e., increased neutrophils in bronchoalveolar lavage fluid) in mice.
Conclusions: These findings demonstrate that pyrotechnic display particles can produce adverse effects in mammalian cells and lungs, thus suggesting that further research is needed to expand our understanding of the contribution of metal content to the adverse health effects of fireworks particles. This information will lead to the manufacture of safer fireworks.