A night of wonder for 1 million — but a nightmare for everyone else

"Wow, they're finally going off."

At 8 p.m. Saturday, the skies above Yeouido in Seoul erupted in color. Thunderous booms rolled across the Han River as brilliant bursts of light filled the night, drawing gasps and cheers from the crowds below.

The show lasted about an hour — a festival night that drew roughly 1 million spectators.

But only humans know that fireworks are a spectacle. For others, the deafening noise and blinding flashes trigger pure panic, sending them on desperate, life-threatening flights into the dark.

It is, quite literally, a deadly flight. In documented cases, disoriented birds have slammed into buildings immediately after fireworks displays, with thousands dying at once.

Pet animals in urban areas are no less affected. In a state of panic, they search frantically for somewhere to hide, sometimes injuring themselves or exhibiting other erratic behavior.

Fireworks leave their mark on humans, too. Long after the last shell bursts, dangerously high concentrations of fine particulate matter linger in the surrounding air for hours — the result of tiny particles laden with heavy metals released during the explosions.

Air quality near the festival site deteriorated sharply as soon as the show ended Saturday. At 10 p.m. in Yeongdeungpo-gu, the concentration of ultrafine particulate matter (PM2.5) surged to 121 micrograms per cubic meter — a level classified as "very bad." The Seoul-wide average at the same hour was 11 micrograms per cubic meter, meaning the festival area recorded roughly 11 times the city average.

The PM10 reading also hit 148 micrograms per cubic meter, rated "bad," compared with a Seoul average of 16 micrograms per cubic meter at the same time — about nine times higher. Elevated PM2.5 levels persisted in the area for some time afterward.

The post-fireworks particulate spike is not a new finding — domestic research has documented it before.

A research team led by Choi Yun-hyung, a professor at Korea University's School of Health and Environmental Science, analyzed air quality during the Seoul International Fireworks Festival and the Busan Fireworks Festival in 2023. In Seoul, PM2.5 concentrations that had hovered between 9 and 12 micrograms per cubic meter before the show rocketed to as high as 320 micrograms per cubic meter immediately after.

That peak was up to about 32 times the pre-show level. It took roughly three hours for concentrations to return to baseline.

Fireworks are far more than a light show. As the shells explode and burn, they release not only fine particles but also sulfates, nitrates, organic compounds, various metallic elements and soot.

A range of metal compounds is used to produce vivid colors: strontium for red, barium for green and copper compounds for blue are among the most common.

A study conducted during China's 2025 Lunar New Year found that PM2.5 levels rose between 10.5 and 226.4 percent compared with the period before the fireworks. Secondary inorganic aerosols — including sulfates, nitrates and ammonium — increased significantly, as did fireworks-specific marker compounds such as potassium and chloride.

The damage extends beyond the air. Fireworks and firecracker debris contain incompletely burned fuel, additives, metal salts and packaging residue — all of which can eventually wash into rivers and lakes, disrupting microbial activity and harming aquatic life.

A study that monitored pond water quality after three fireworks events in Albany, New York, between 2008 and 2010 found that perchlorate concentrations spiked to at least 30 times — and as much as 1,480 times — normal levels immediately after each display.

The harm fireworks cause does not stop with humans. Among the most directly affected are birds.

Bird casualties are among the most widely cited direct harms. When intense noise and light erupt nearby, birds do not merely deviate from their usual flight paths — they lose the ability to find new ones altogether. Disoriented, they collide with buildings and other structures, and mass die-offs are far from uncommon.

In Beebe, Arkansas, in 2010, between 3,000 and 5,000 red-winged blackbirds were found dead around New Year's Eve. A US Geological Survey examination of the carcasses determined the direct cause of death to be blunt-force trauma — injuries consistent with collision with hard objects.

In early 2021, hundreds of birds were found dead on a street in Rome following a large fireworks display. The International Organisation for Animal Protection suggested the birds had taken flight simultaneously in fright at the noise, then collided with one another or struck buildings and power lines.

The geographic reach of fireworks-related bird harm is also vast. Research by a team led by Bart Hoekstra, a professor at the University of Amsterdam, found that birds can be disturbed by New Year's fireworks from as far as 10 kilometers away. The researchers also confirmed that in one specific study area alone, fireworks caused 400,000 birds to take flight.

Household pets are no exception. A 2010 study by researchers at Unitec Institute of Technology in Auckland, New Zealand, found that 46 percent of the 3,527 dogs and cats surveyed showed fear responses to fireworks that their owners could clearly observe.

Dogs tended toward more active fear responses — trembling and destructive behavior — while cats more often hid, cowered or tried to flee. Notably, 51 of the 923 animals for which complete responses were recorded, about 6 percent, had suffered physical injuries related to fireworks.

As awareness of fireworks' side effects grows, some jurisdictions are tightening the rules. The Netherlands banned the purchase, possession and use of consumer fireworks — except for the lowest-risk F1 category — nationwide from Aug. 1 this year, citing air pollution and harm to animals and the environment.

Other proposed measures include restricting fireworks near areas where birds congregate, concentrating professional displays at designated venues rather than allowing indiscriminate private use, and developing low-emission "eco-friendly fireworks." Drone light shows and laser displays that require no gunpowder are also being discussed as alternatives.

"We need to shift away from large fireworks toward eco-friendly alternatives that do not cause air pollution — for example, drone shows or light festivals," said Choi Yun-hyung, a professor at Korea University's School of Health and Environmental Science. "The government and local authorities should work together to regularly monitor air quality before and after fireworks events and pursue technological solutions to clean up the polluted air that remains after festivals."