When fireworks are launched into the sky, they introduce a variety of chemicals into the atmosphere. Launching the shell requires an oxidizer, which is also needed for the shell explosion, and many fireworks contain oxidizers such as perchlorates. These can dissolve in water, contaminating rivers, lakes and drinking water. Fireworks displays are often done over bodies of water to lessen the chances of brush fires starting from any residual glowing embers. The result is pollution of rivers and lakes from unburned perchlorate residues.
The smoke and particulate matter created by the launch of the shell can result in locally poor air quality for hours after the display is over. The colors in firework displays come from metallic compounds and salts (such as barium or aluminum) and many of these chemicals can also be harmful to both people and the environment.
Work is underway, using recycled materials and alternatives to the perchlorate rocket fuel used to launch the shells. Some newer, ‘cleaner’ fireworks replace perchlorates with safer alternatives, or use compressed air to reduce smoke created.